Enhancing Pilot Ability to Perform Continuous Descent Approach with Descriptive Waypoints

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Thesis completed in 2010 for master program in Human Factors and Applied Psychology.

Thesis completed in 2010 for master program in Human Factors and Applied Psychology.

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  • 1. CALIFORNIA STATE UNIVERSITY, NORTHRIDGEEnhancing Pilot Ability to Perform Continuous Descent Approach withDescriptive WaypointsA thesis submitted in partial fulfillment of the requirementsFor the degree of Master of Arts in Psychology,Human Factors and Applied PsychologyByMichael C. LaMarrDecember, 2010
  • 2. iiThe thesis of Michael LaMarr is approved by:Dr. Nhut Ho DateBarry Berson, M.A. DateDr. Tyler Blake, Chair DateCalifornia State University, Northridge
  • 3. iiiAcknowledgmentsDr. Nhut HoThanks for your advice, guidance, support, and critique throughout the research andthesis writing process. Your guidance on meaningful research gave me the drive to keepon task and kept me going on to do the best work that I could produce.Dr. Tyler BlakeI am grateful for your guidance throughout my education in the Human Factors Master’sprogram. You taught me that it is important to start from the outside and to work my wayin and to keep up with technology and new practices in the Human Factors world.Barry BersonThank you for your support on my thesis writing and helping me whenever I had anytrouble. Your classes taught me the tools and how to use them to be a successful HumanFactors professional. You also taught me how to connect with other Human Factorsprofessionals and I have made many connections because of you.Dr. Walter Johnson, Vern BattisteThanks for all the meetings we had about the design of my thesis. I had to work extrahard just to make sure everything was up to standard. Also thanks for the opportunitiesof working with you guys on your research and for allowing me the opportunity to workwith pilots and air traffic controllers.Joe BivianoThanks for all your time in helping me design my flight scenarios and making them asrealistic as possible. I couldn’t have done this study without your help.
  • 4. ivTable of ContentsSignature Page................................................................................................................................................ iiAcknowledgments......................................................................................................................................... iiiList of Figures ................................................................................................................................................viABSTRACT................................................................................................................................................. viiBackground .....................................................................................................................................................1Continuous Descent Approach Benefits .....................................................................................................1Continuous Descent Approach Challenges.................................................................................................3Descriptive Waypoints to aid in CDA Arrivals ..........................................................................................7Display of Descriptive Waypoints ..............................................................................................................9Objective .......................................................................................................................................................14Hypotheses ....................................................................................................................................................15Method ..........................................................................................................................................................17Participants................................................................................................................................................17Design.......................................................................................................................................................17Material.....................................................................................................................................................19Facilities....................................................................................................................................................21Procedure ..................................................................................................................................................22Results...........................................................................................................................................................25Time Variation..........................................................................................................................................25Power Usage .............................................................................................................................................26Attitude and IAS Deviation.......................................................................................................................27Perceived Workload..................................................................................................................................33Preference Number of DW .......................................................................................................................34Discussion .....................................................................................................................................................36Hypothesis One.........................................................................................................................................36Time Variation..........................................................................................................................................36Power Usage .............................................................................................................................................36Attitude Deviation.....................................................................................................................................37IAS Deviation ...........................................................................................................................................38Hypothesis Two ........................................................................................................................................39Time Variation..........................................................................................................................................40Power Usage .............................................................................................................................................40Attitude and IAS Deviation.......................................................................................................................40Hypothesis Three ......................................................................................................................................41Time Variation, Power Usage, Altitude and IAS Deviation .....................................................................41Hypothesis Four........................................................................................................................................41Perceived Workload..................................................................................................................................41Hypothesis Five ........................................................................................................................................42Preferred DW Amount..............................................................................................................................42
  • 5. vSubjective Data and Feedback.......................................................................................................................43Flight Chart Feedback...............................................................................................................................43Vertical View of CSD Feedback...............................................................................................................43DW Feedback ...........................................................................................................................................43Pilot Strategies ..........................................................................................................................................45Feedback on CDA scenarios.....................................................................................................................46Limitations ....................................................................................................................................................47Future Research.............................................................................................................................................48Conclusion.....................................................................................................................................................49References.....................................................................................................................................................51Appendix A: Example Flight Chart..............................................................................................................54Appendix B: Training Manual......................................................................................................................55Appendix C: Orientation PowerPoint...........................................................................................................63Appendix D: Training Checklist ..................................................................................................................67Appendix E: Practice Run Checklist ............................................................................................................68Appendix F: Pilot Responsibilities...............................................................................................................69Appendix G: Debrief/ Questionnaire............................................................................................................70
  • 6. viList of FiguresFigure 1: Conventional Approach ..................................................................................................................2Figure 2: Conventional Approach and Continuous Descent Approach..........................................................3Figure 3: Flap Cues Recommended by Koeslag (1999) in Primary Flight Display .......................................5Figure 4: Energy Management System used by NASA Langley Research Center ........................................6Figure 5: DW Cues with Flap, Altitude and Indicated Air Speed References (Ho 2006) ..............................8Figure 6: 2D Navigation Display ...................................................................................................................9Figure 7: Flight Chart Final Approach .........................................................................................................10Figure 8: Three Descriptive Waypoints........................................................................................................11Figure 9: Coplanar Navigation View (Prevot, 1998)....................................................................................12Figure 10: 3D Cockpit Situation Display .....................................................................................................13Figure 11: Experimental Design Matrix.......................................................................................................18Figure 12: Wind Speed.................................................................................................................................18Figure 13: MACS on left and Cockpit Situation Display on right ...............................................................19Figure 14: One Descriptive Waypoint Condition.........................................................................................20Figure 15: Three Descriptive Waypoints Condition.....................................................................................20Figure 16: Five Descriptive Waypoints Condition.......................................................................................21Figure 17: Pilot Station Setup ......................................................................................................................22Figure 18: Mean Time Deviation Main effect on Wind ...............................................................................26Figure 19: Average Power Main effect on DW............................................................................................27Figure 20: Average Altitude Deviation Main effects on DW.......................................................................28Figure 21: Average Altitude Standard Deviation on DW ............................................................................29Figure 22: Average Altitude Deviation Main effects on DW 1....................................................................30Figure 23: Average Altitude Deviation Main effects on DW 2....................................................................31Figure 24: Average Altitude Deviation Main effects on DW 3....................................................................32Figure 25: Average Altitude Deviation Main effects on DW 4....................................................................33Figure 26: Workload Main effect on DW ....................................................................................................34Figure 27: Preferred number of DW for each Wind Condition....................................................................35
  • 7. viiABSTRACTEnhancing Pilot Ability to Perform Continuous Descent Approach withDescriptive WaypointsByMichael LaMarrMaster of Arts in Psychology, Human Factors and Applied PsychologyObjective: Conduct an experimental study to determine the effectiveness of usingDescriptive Waypoints (DWs) (a target/checkpoint in space along the flight path thatgives the pilot altitude and indicated airspeed) to improve flight performance duringContinuous Descent Approach (CDA) procedures, and provide recommendations on DWdesign and integration into existing CDA procedures.Background: Aircraft noise is a burden on people living around airports and is animpediment to the growth of air transportation. CDA is an approach that reduces noiseimpact on the ground by keeping the aircraft at a higher altitude longer than standardapproaches and by keeping engines idle or near idle. However, CDA implementationrequires controllers to add large separation buffers between aircraft because aircraft ofdifferent sizes and weights descend at different rates, consequently creating uncertainty inseparation between aircraft. A possible solution to allow aircraft to descend moreconsistently is to use DWs to provide pilots targets and feedback along the CDA path.Method: Twelve Instrument rated commercial pilots participated in a 3 by 3 WithinSubject Factorial Design. Participants flew three different wind conditions using one,three, or five number of DWs. Dependent variables included: deviation from target DWaltitude and Indicated Airspeed (IAS), deviation from Required Time of Arrival (RTA),average power usage, perceived workload, and pilot acceptance of DWs. Objective andsubjective data were collected to evaluate the effectiveness of the number of DWs.Results: As the number of DW increased pilots mean altitude deviations decreased by726 feet and standard deviations by 332 feet with a slight increase in perceived workloadand one percent in power usage. Wind had a significant effect on RTA with mean timesbeing within eleven seconds of each other. Pilots would prefer to have two DWs targetsin each wind condition, and felt comfortable using DW to fly CDA.Conclusion and Application: The results showed that DWs can be used as an effectivecuing system to enhance pilot ability to perform CDA, and that they are a potential choicefor near to midterm implementation in improving the effectiveness of CDA approach andlanding procedures.
  • 8. 1BackgroundContinuous Descent Approach BenefitsNoise and emissions produced by aircraft when landing are a burden on peopleliving around airports and is an impediment to the growth of air transportation. Theproduced noise limits how many aircraft can land at night and the ability to expand morerunways or build new airports in populated areas. Another problem with airtransportation expansion is the cost of fuel, which is about 27% of the operation cost toairlines (Lowther, Clarke, & Ren, 2007). Lowther (2007) also mentions that with airtraffic growth expected to increase 150% by 2025, corresponding increase in noise,emissions, and fuel will be a problem for the air transportation system.Currently, aircraft descend and land at different speeds based on their size andweight, making it difficult to predict their future trajectory. Air Traffic Controllers(ATC) compensate for dissimilar aircraft performance by creating an approach pattern inwhich all aircraft fly level flight segments at the same speeds as they enter the terminalarea (Reynolds, H., Reynolds, T. & R. Hansman, 2005). This practice makes it lesschallenging for the ATC to separate aircraft; however, it creates a significant noiseimpact on the local community. The noise is most profound in areas where the aircrafthave to fly at low altitudes near the runway because of the existing navigationconstraints. Specifically, aircraft land by using an instrument landing system (ILS) (seeFigure 1) glide slope to intercept the glide path at the correct descent angle to the runway.The ILS provides the pilot with lateral and vertical guidance to maintain the correctapproach orientation for landing. This is accomplished by leveling off at an altitude thatallows the aircraft to intercept the glide slope from below. If the aircraft flies above the
  • 9. 2glide slope it may intercept a false glide slope and come into the airport at an incorrectlanding angle.Figure 1: Conventional ApproachTo operate within the navigation constraints of the ILS and reduce noise impact,noise abatement approach procedures have been developed and implemented. One suchprocedure is Continuous Descent Approach (CDA). CDA also offers other benefits suchas fuel savings and lower emissions impact by using an idle or near idle power bydecelerating the aircraft at a higher altitude longer than the standard landing procedurewithout reverting to level flights (see Figure 2). A CDA study flight demonstration wasconducted in Louisville, Kentucky with Boeing 767-300 aircraft equipped with thePegasus flight management system (FMS) (Clarke, Ho, .et al 2006). It was shown thatCDA can reduce noise by 3.5 to 6.5 dBA (3 dBA is noticeable to the ear) and fuelconsumption by 400 to 500 pounds.10,000Feet4,000 feetILS Glide SlopeAirport
  • 10. 3Figure 2: Conventional Approach and Continuous Descent ApproachContinuous Descent Approach ChallengesImplementation of CDA is not practical in moderate to high traffic because itrequires a larger separation buffer between aircraft than the standard landing procedure.Predicting where the aircraft will be is cognitively taxing on the controller and pilotsbecause deceleration is non-linear and humans have a difficult time judging non-lineardeceleration when speeds are constantly changing (Reynolds, H. 2006). To implementCDA, ATC have to know when aircraft are at the right distance from the airport toinitiate the clearance to start the CDA approach procedure. If the air traffic controllertells the pilot to initiate CDA too early, then the aircraft will arrive before the runway andwill have to level out before landing. Leveling out early requires power increase, whichin turn creates more noise and defeats the purpose of the procedure. If the air trafficcontroller tells the pilot to initiate the procedure too late, then the pilot will end upmaking a fast landing or have to fly around and make another landing attempt (whichproduces more noise and uses more fuel, which also defeats the purpose of the CDA).4,000feetILS GlideSlopeRunwayContinuousDescentApproachConventionalApproach10,000Feet
  • 11. 4Other challenges to the implementation of CDA procedures remain the difficultythat pilots have managing the deceleration of aircraft in the presence of uncertainties inpilot response time, vertical navigation (VNAV) (controls vertical automation of aircraftaccording to flight profile programmed in the flight management system (FMS))performance, and wind conditions (Clarke, Ho, et al., 2006). Koeslag, M. F., (1999) alsoidentified other problems with current CDAs. The first problem is that vertical flightprofile is not fixed and depends on the FMS installed, and if there is no vertical capabilityit depends on the skill and training of the pilot. The second problem is that wind cancause the aircraft to deviate from the FMS-predicted flight trajectory. This unpredictedinterference can cause the flight trajectory to differ from the true flight trajectory, causingthe pilot to make adjustments such as adding thrust. Wind deviations can cause a +/- 2minute deviation from the FMS trajectory. One of Koeslag’s proposed solutions was tofix the vertical profile of CDA to improve arrival time predictability. Another issuebeing addressed was to update the flap profile of the aircraft when there were speeddeviations. This profile is displayed in the primary flight display. Koeslag developed analgorithm to address problems with the FMS and tested it in a simulator, but concludedthat many real world tests will need to be conducted to deal with various aircraft sizesand weights in multiple wind conditions. One recommendation that Koeslag made toassist pilots performing CDA is to add flap guidance in the primary flight display (PFD)(see Figure 3).
  • 12. 5Figure 3: Flap Cues Recommended by Koeslag (1999) in Primary Flight DisplayOther research efforts aiming to make CDA more predictable focus on equippingthe flight management system with 4D guidance (x, y, z, and time). Moore (2009)proposed 4D information with a required time of arrival (RTA) to help ATC establish astrategic time scale of CDA traffic flow. The algorithms designed in this research areaimed to minimize time, fuel, and emissions produced. One problem noted is thatautomation can cause the VNAV to make occasional thrust changes that can cause extranoise and fuel usage. Other research on RTA during CDA operation proposed to providepilots with an energy management cueing system (see Figure 4) in the navigation displayto minimize fuel, noise, and emissions by providing pilots with optimal vertical path withenergy events and energy error cues for managing throttle and drag (Williams, 2008).
  • 13. 6Figure 4: Energy Management System used by NASA Langley Research CenterAnother study, conducted at Louisville International airport, found that near termCDA implementation is possible by conducting flight tests (Clarke, Ho, Ren, Elmer,Tong, & Wat, 2004). The authors noticed in the flight tests that the FMS and pilot delayhad some undesired effects on noise produced by the aircraft. Pilot delay in initiating theflaps could have undesired effects on VNAV that could cause the aircraft to deviate from
  • 14. 7the altitude programed on the FMS. Another problem with the VNAV is that whendescending, VNAV’s logic gives the altitude constraint higher priority than the speedconstraint, and with factors such as tail wind, the aircraft would not always meet thespeed targets. It is important to meet both the speed and altitude constraints on the flightpath for fuel and time efficiency, and for traffic separation.Descriptive Waypoints to aid in CDA ArrivalsThese studies have been beneficial to CDA research, but are aiming for mid tolong term implementation; until better VNAV logics and FMS designs can compensatefor pilot delay, altitude and speed constraints, and wind uncertainties, the pilot has tocontrol the vertical profile manually. If pilots have information to help them stay on theflight path, managing their aircraft’s speed, and arrive at the airport at a predictable time,CDA would be more feasible for daily use. One way to aid pilots to execute CDA is togive them feedback information. Without the help of a cuing system, pilots find itdifficult to manage the aircraft energy to meet a target speed at a specific altitude in thepresence of uncertainty. According to Ho (2006), there are two reasons for uncertaintyduring CDA. One reason is the pilot’s inability to estimate future position of aircraftbecause the deceleration profile is non-linear. The second reason is that the pilot’sprojection may be incorrect because of wind uncertainty. In Ho’s study, gates (forconsistency purpose, gates will be called Descriptive Waypoints (DW) in this thesis)(altitude and speed target along the flight path) varying in number (zero, one, two, andthree) were proposed to use with a flap schedule. Each of these conditions also had winduncertainty and no wind uncertainty. For the two DW condition, the DWs were locatedat 5000 and 3000 feet from the runway, and the three DW condition had DWs at 5000,
  • 15. 84140, and 3000 feet. Pilots were given DWs on a cue card (see Figure 5). In the threeDW condition, pilots were able to achieve the target speed at a higher rate than the otherconditions.Figure 5: DW Cues with Flap, Altitude and Indicated Air Speed References (Ho2006)CDA is being considered at further distances for fuel savings and emissionsreduction. Coppenbarger researched oceanic tailored arrivals (OTP) which starts CDA at37,000 to 40,000 feet altitude. OTP uses CDA in constrained airspace conditions byintegrating advanced air and ground 4D automation through digital datalink with theaircraft FMS. Results showed that the fuel savings with Boeing 777 is between 200 and3000 lb per flight (Coppenbarger, Mead, and Sweet 2006).After reviewing these studies, the idea of Descriptive Waypoints (altitude andspeed target along flight path) (DW) was formed. The name DW was given becausedynamic waypoints (target altitude and speed waypoints that can be created in real time,
  • 16. 9with relying on existing waypoint database) focus on providing updated waypointinformation and DW is a description of a waypoint that could include a time target, flaprequirement, gear deployment, target altitude, and speed. For this study, only altitude andIndicated Air Speed (IAS) was provided in the DW. Flap information was displayed inthe PFD.Display of Descriptive WaypointsWith the description of DW defined, it is important to examine how to display theinformation to the pilot. Currently, pilots use a navigation system to keep track of wherethey are going. Information such as other aircraft, weather, and terrain can be displayed.The navigation system (see Figure 6) is a useful way of informing the pilot of the generalsurroundings, but is currently limited to a 2D perspective.Figure 6: 2D Navigation Display
  • 17. 10Pilots also use arrival charts when they are on their final approach, with thevertical information (altitude) displayed as text as in the 2D navigation display, as well.See Appendix A for an example full flight chart (Global Aviation Navigation, Inc.,2009). Figure 7 represents the vertical profile the pilot needs to take to intercept the glideslope to land.Figure 7: Flight Chart Final ApproachThomas and Wickens (2006) found that it is easier to make specific and accuratejudgments based on absolute spatial information displayed in 2D with 3D information.This is because 3D displays tend to make the x, y, and z axis ambiguous whereas 2Dinformation gives precise x, and y information, but will need the 3D information in text.So, is it better to display information in 3D or 2D to the pilot during CDA? There is aproblem that occurs while using 3D views. Without other depth cues available, thelocation of objects become ambiguous (Cowen, John, Oonk, & Smallman, 2001). Even
  • 18. 11with this problem 3D views do have their advantages. For example, shape understandingis beneficial in 3D, whereas 2D is more accurate for precision tasks (Symmes & Pella,2005). There is no clear answer for which display is better for DW, but for the currentstudy it makes sense to display the information to pilots in 2D because they are onlycontrolling their vertical descent during CDA, without traffic separation and terrainavoidance.A near term solution is to display DW information in a vertical flight chart (seeFigure 8). Flight charts typically display the final approach right before the glide slope atroughly around 3,000 to 10,000 feet altitude. In a study by Ho (2006), it was shown thatproviding vertical information and DW at 7,000 feet altitude improved pilot ability toperform CDA. The current study is taking the vertical information provided to the pilotback to 23,000 feet altitude at 70 miles from the airport. This is motivated by the factthat CDA procedures are being proposed to start at a very far distance from the airport,such as the top of descent location, which is typically at 37,000 to 40,000 ft.Figure 8: Three Descriptive Waypoints
  • 19. 12A possible solution for near to midterm is to use a coplanar view (horizontal andvertical profiles) of the navigation with DW information. The vertical display wouldbenefit pilots, enabling them to monitor the vertical profile when VNAV is turned off andthe pilot is manually flying the vertical profile (Prevot, 1998) (see Figure 9).Figure 9: Coplanar Navigation View (Prevot, 1998)Another possible long term solution that can help the pilot perform CDA moreefficiently is to use DW displayed in Cockpit Situation Display (CSD) to provide 3Dvisualization of the flight plan (see Figure 10). CSD is a navigation aid that pilots canuse to gain information of surrounding air traffic, alert them of possible conflicts, providespacing tools, etc. CSD takes care of 3D ambiguities by allowing the pilot to rotate thescreen 360 degrees and switch to 2D at any moment.
  • 20. 13Figure 10: 3D Cockpit Situation Display
  • 21. 14ObjectiveThe objective of this study was to conduct an experimental study to determine theeffectiveness of using Descriptive Waypoints in CDA procedures and providerecommendations on DW design and integration into existing CDA procedures. Thisstudy expands on past research of providing pilots with DW information byimplementing the DW at a farther distance and at a higher altitude than in previousstudies. Thus, this current study is more of a strategic approach to perform CDA bystarting at a cruise altitude compared to the Ho (2006) study of using DW near finaldescent. Also being studied is short to midterm implementation, whereas other studiesaimed for a mid to long term implementation, with a focus on FMS algorithmdevelopment.
  • 22. 15HypothesesHypothesis one is that, as the number of Descriptive Waypoints increases,required time of arrival deviation, average power of aircraft, and altitude and IASdeviation will decrease. This is the result found in Ho (2005), and is also supported byReynolds (2005) work on adding structure, or standardization, to the procedure, to reduceuncertainty and thereby improve the pilot’s ability to predict future locations along aflight path.The second hypothesis is that required time of arrival, average power, and altitudedeviation will be less for the nominal wind speed condition in comparison to the slow andfast wind speed conditions. Koeslag (1999) stated that wind can cause aircraft to deviatefrom flight path and cause a +/- 2 minute deviation in time. Also, Ho (2006) states thatpilot’s projection may be incorrect because of wind uncertainty.The third hypothesis is that as number of Descriptive Waypoints increase,required time of arrival, average aircraft power, and altitude deviation will be the sameacross the different wind conditions. One DW gives pilots freedom of flight whichwould create variation among the different wind conditions. With five DWs, there is astrong structure for the pilot that should make the variation practically the same for allwind conditions.The forth hypothesis is as the number of Descriptive Waypoints increase,perceived workload will increase. One DW gives pilots less constraints to meet, andshould not drive up pilot workload. Three DWs generate more structure and slightly
  • 23. 16more workload, while five DWs should provide even more structure and constraints forthe pilot to meet, and the perceived difficulty can go up.Hypothesis five is that pilots will prefer five Descriptive Waypoints in all windconditions. Pilots in the Ho (2006) study preferred to have three DWs, but this was for ashort distance from the runway. Over a longer distance such as the one studied in thisthesis, it was predicted that five DWs would be preferred by pilots.
  • 24. 17MethodParticipantsParticipants included twelve instrument-rated, commercial pilots (11 male, 1female) between the ages of 24 and 67 (Mean 37.64 years old) with years of flyingbetween 2 and 37 years (Mean 18.75 years) and with 590 to 23,000 (Mean 7660) hoursflight time. Two pilots with CDA experience, and one with CDA simulation experience,participated in this experiment.DesignA 3 wind (Fast, Normal, and Slow) x 3 DW (One, Three, and Five) within-subjectfactorial design was used (see Figure 11). In the Fast wind condition, the wind speedstarted at 52.8 knots (60% increase over the normal wind condition), the Normal windcondition had a starting wind speed of 33 knots, and the Slow wind condition had astarting speed of 19.8 knots (40% decrease in normal wind) (see Figure 12). These windconditions were based on historical data at Louisville International Airport, and the windconditions were chosen to produce noticeable differences. The One DW conditionprovided the pilot with an end target to achieve, the Three DW condition provided thepilot with three targets, and the Five DW condition provided the pilot with five targets.The number of DWs was designed to vary the amount of feedback provided to the pilots.Dependent variables included: altitude and IAS deviation, computed as theabsolute deviation from target DW altitude and IAS. Altitude deviations and IASdeviations are metrics used to evaluate how adding feedback helps pilots maintain CDA.RTA is computed by determining the absolute time in seconds from target time (fast windtarget time 720s, normal wind target time 750s, and slow wind target time is 770s).
  • 25. 18Varying RTA for different wind conditions gives the pilot different arrival time targetsand provides data to evaluate the effects of using DWs on improving the separationbuffer, which is an indication of the airport throughput. Power usage was computed asthe average power the aircraft uses during the CDA. Perceived workload, pilotacceptance of DW, pilot strategies and other subjective data were collected in aquestionnaire (rating scales and open ended questions) (see appendix G) to evaluate theeffectiveness of DW and obtain feedback on pilot acceptance and the integration of DWinto existing CDA procedures.1 DW x Slow Wind 3 DW x Slow Wind 5 DW x Slow Wind1 DW x Normal Wind 3 DW x Normal Wind 5 DW x Normal Wind1 DW x Fast Wind 3 DW x Fast Wind 5 DW x Fast WindFigure 11: Experimental Design MatrixFigure 12: Wind Speed01020304050600 5000 10000 15000 20000 25000AltitudeFast WindNormal WindSlow WindWindSpeed
  • 26. 19MaterialStimuli were displayed on two 19” monitors, one running Multi Aircraft ControlStation (MACS) software and the other monitor, Cockpit Situation Display (CSD)software (see Figure 13). MACS is a dynamic interface that allows the pilot to fly andinteract with the aircraft’s systems, such as IAS, vertical speed, flap settings, and altitude.The CDA landing procedure flight plan was shown on a 2D fixed vertical view of CSD.DWs will be displayed on a flight chart as one, three, and five DWs. The vertical profilewas developed by NASA in a study (Prevot, T., Callantiner, T. Kopardekar, P., Smith,N., Battiste, V., 2004). Modifications were made by creating aircraft start and end points,removing all traffic, and by adding DW locations with energy consideration, noise,deceleration, speed/altitude targets, and power usage.Figure 13: MACS on left and Cockpit Situation Display on rightIn the one DW condition, pilots see their flight plan on their flight chart (seeFigure 14). The only information pilots received is a target to intercept five miles fromthe airport. Figure 14 through 16 present an example of the one, three and five DWconditions. The vertical profile is the same in all conditions.
  • 27. 20Figure 14: One Descriptive Waypoint ConditionFigure 15: Three Descriptive Waypoints Condition
  • 28. 21Figure 16: Five Descriptive Waypoints ConditionA training manual (see Appendix B) was developed to train pilots how to use theMACS and CSD interfaces that were used for the experiment. A PowerPoint presentation(see appendix C) was developed to introduce the pilot to the task and goals for theexperiment. Two checklists were developed to assess pilot learning. The first checklist(see appendix D) checked pilot understanding of the training manual. The secondchecklist (see appendix E) made sure the pilot could perform the tasks that were requiredfor the experiment during a practice CDA simulation.FacilitiesThe study was conducted in the Systems Engineering Research Laboratory(SERL) (see Figure 17). Pilots were in a room with a one-way mirror and sat at a deskwith two computer monitors, a flight chart and used a mouse to interact with themonitors.
  • 29. 22Figure 17: Pilot Station SetupProcedurePilots were contacted by the experimenter by phone. CDA and DW weredescribed to the pilot. Date and time of the experiment were set and a training manual(see Appendix B) was emailed to the pilots. On the day of the study, the experimenteradministered the participant bill of rights, consent form, and reviewed the training manualwith the pilot. After that, the pilots were shown a short PowerPoint presentation (seeappendix C). This presentation informed the pilot that they are flying for a companycalled Silent Deliveries. This presentation also discussed CDA and pilot goals. Thecompany’s three goals, starting with highest prioritized goal of achieving all of theDescriptive Waypoints at the specified altitude (range of +/- 300 feet) and IAS targetswere described to the participants. Another restriction to IAS is that the pilot must keepspeed under 250 IAS below 10,000 altitude. The second goal was to achieve the last DWat RTA within 30 seconds. The third goal was to keep aircraft power below 10%, butkeep it as close to 0% as possible. Also, from 10,000 feet to the last DescriptiveWaypoint, power should be monitored more closely.Pilots were told to be alert and not leave speed brakes on when not decelerating,to avoid power increase. Pilots were also told that LNAV will be engaged and that
  • 30. 23horizontal navigation is not required. VNAV will be turned off: vertical navigation bypilot will be required, flaps must be used as indicated on PFD, and landing gear must bedown by 5.5 nm from SDF.After the presentation, the experimenter went over the training manual. Thismanual explained the controls for the MACS software and information that is displayedon the CSD. After that, the pilots were trained to use the software and were given theobjectives of the study. The experimenter loaded the MACs on the left 19” monitor, andCSD on the right 19” monitor.The experimenter then gave an oral checklist to the pilot to check the pilots’understanding of the training manual (see appendix D). The training checklist asked thepilots to identify the vertical speed indicator and buttons, IAS indicator and buttons, PFDpower indicator, flap location on PFD, flap settings, speed brakes, and landing gear onthe MACs display. If a pilot had trouble with any of this, the experimenter took a note ofit and assisted the pilot to find the correct location on the MACs display. Also, thechecklist indicated that the wind speed and direction are located on the navigationaldisplay on the MACS screen.After the checklist, the experimenter loaded up a CDA practice run. The practicerun was different than the experimental run. Experimenter also had the pilot fly CDA,and went over another checklist (see appendix E) to make sure the pilot could performthe tasks that were required for the experiment. This checklist asked the pilot to changethe vertical speed and IAS, use flaps, speed brakes, and landing gear to make sure thepilots could make the changes on their own. Also, the experimenter showed the pilothow the speed brakes affect the power of the aircraft and asked the pilot to intercept the
  • 31. 24Descriptive Waypoint Alt<10 (a waypoint shown in the CSD) at +/- 300 feet and within+/-5 IAS deviations. The pilot was given an RTA of 5 minutes 30 seconds from Alt<10to 5nm to SDF. After the pilot had completed all practice tasks, the pilot received a paperwith instructions on pilot responsibilities for the experiment (see appendix F). After thatthe experiment began.The experimenter watched the experiment in the next room through a one-waymirror and on camera. At the end of each experimental trial, the experimenter entered theroom to load the next scenario and give the pilot a five-minute break. After the break, thenext experiment simulation began. The experiment was broken up into ninecounterbalanced trials at about 12-13 minutes each. When the experiment was over, ashort questionnaire/debrief (see appendix G) that included likert scales, lists, and openquestions were given to pilot followed by a short interview. The pilot was thencompensated $50.
  • 32. 25ResultsTime, average power, altitude and IAS deviations were collected from MACSoutput and put into excel for each participant for nine conditions. Data was organized bydependent variable, and a 3x3 (Wind x DW) analysis of variance (ANOVA) on SPSS 17was run for each of the dependent variables.Time VariationThere was a non-significant main effect of DW on time, F(1.698, 18.678)= 2.096,p=0.156, and a significant main effect of Wind on time ,F(1.873, 20.605)=7.172,p<0.005, etap2=0.879. High wind (mean=13.87 sd=18.59) resulted in significant differenttime compared to Slow wind (mean=17.28 sd=13.33) and Normal wind (mean=25.03sd=17.64). Time difference between High wind and Slow wind was 3.41 seconds, Slowwind to Normal wind 7.75 seconds and from Normal wind to Fast wind was 11.16seconds. There was not a significant interaction effect between DW and Wind on time, F(2.884, 31.721)=1.67, p=0.912. Figure 18 shows the mean time deviations on Wind.
  • 33. 26Figure 18: Mean Time Deviation Main effect on WindPower UsageThere was a significant main effect of DW on average power, F(1.928, 21.203)=3.731, p<0.042, etap2=0.609 and no significant main effect of Wind on average powerF(1.299, 14.288)=0.350, p=0.620. One DW (mean=7.25 sd=2.31) resulted in significantdifference of average power, compared to the three DW condition (mean=7.62 sd=2.39)and five DW condition (mean=8.35 sd=3.45). One DW difference between three DW was.37 average power, between three DW and five DW was .73 average power, and betweenfive DW and one DW was 1.1 average power. There was not a significant interactioneffect between DW and Wind on average power, F (2.495, 27.442)=0.826, p=0.472.Figure 19 shows the mean power for different DW conditions.051015202530SlowWindNormalWindHighWindRTADeviationInSeconds
  • 34. 27Figure 19: Average Power Main effect on DWAttitude and IAS DeviationFor ease of illustration, Figure 16 shows the vertical profile and DW along theflight path. In these sections, location DW 1 is 18nm to Cheri, DW 2 is Cheri, DW 3 isAlt<10, DW 4 is 10nm to SDF, and DW 5 is 5nm to SDF.There was a significant main effect of DW on altitude deviation on DW targets 2through 4, F(1.392, 15.308)= 26.364, p<0.000, etap2=1.000 and no significant maineffect of Wind on average altitude deviation on DW targets 2 through 4 F(1.861,20.468)=0.547, p=0.586. Five DWs (mean=196.06 sd=238.90) resulted in a significantdifference in average altitude deviation compared to three DWs (mean=516.00sd=287.68) and one DW (mean=922.32 sd=570.61). The difference between five DWsand three DWs was 319.94 altitude deviation, between three DWs and one DW was406.32 altitude deviation, and between five DWs and one DW was 726.26 altitude0.002.004.006.008.0010.001 DW 3 DW 5 DWAveragePowerPercentage
  • 35. 28deviation. There was not a significant interaction effect between DW and Wind onaltitude deviation of DW targets 2 through 4, F (1.875, 20.621)=0.311, p=0.709. Figure20 shows the mean altitudes in the DW targets 1 through 5 and Figure 21 shows standarddeviations of altitudes.Figure 20: Average Altitude Deviation Main effects on DW02004006008001000120014001600DW1DW2DW3DW4DW51 DW3 DW5 DWDWConditionAltitudeDeviationinFeet
  • 36. 29Figure 21: Average Altitude Standard Deviation on DWThere was a significant main effect of DW on altitude deviation at location DW 1(see Figure 16, DW 1 is 18nm to Cheri), F(1.820, 20.019)= 4.115, p<0.034, etap2=0.639and no significant main effect of Wind on altitude deviation at location DW 1 F(1.472,16.190)= 1.3670, p=0.276. Five DWs (mean=378.59 sd=270.60) resulted in a significantdifference in altitude deviation compared to three DWs (mean=687.58 sd=527.18) andone DW (mean=612.18 sd=465.83). The difference between three DWs and five DWswas 308.99 altitude deviation, between three DWs and one DW was 75.4 altitudedeviation, and between five DWs and one DW was 233.59 altitude deviation. There wasnot a significant interaction effect between DW and Wind on altitude deviation atlocation DW 1, F (2.666, 29.326)=0.891, p=0.447. Figure 22 shows the mean altitudesat location DW 1.0.00200.00400.00600.00800.001000.001200.001400.001600.00DW1DW2DW3DW4DW51 DW3 DW5 DWAltitudeDeviationinFeetDWCondition
  • 37. 30Figure 22: Average Altitude Deviation Main effects on DW 1There was a significant main effect of DW on altitude deviation at location DW 2(see Figure 16, DW 2 is Cheri), F(1.338, 14.718)= 17.834, p<0.000, etap2=0.991, and nosignificant main effect of Wind on altitude deviation at location DW 2, F(1.434,15.774)= 1.100, p=0.336. Five DWs (mean=170.04 sd=255.25) resulted in significantdifference in altitude deviation compared to three DWs (mean=318.91 sd=425.77) andone DW (mean=749.84 sd=523.80). The difference between five DWs and three DWswas 148.87 altitude deviation, between three DWs and one DW was 430.93 altitudedeviation, and between five DWs and one DW was 579.8 altitude deviation. There wasnot a significant interaction effect between DW and Wind on altitude deviation atlocation DW 2, F (2.573, 28.304)=1.139, p=0.345. Figure 23 shows the mean altitudesat location DW 2.0.00200.00400.00600.00800.001000.001200.001400.001 DW 3 DW 5 DWDW 1 Altitude DeviationsAltitudeDeviationinFeet
  • 38. 31Figure 23: Average Altitude Deviation Main effects on DW 2There was a significant main effect of DW on altitude deviation at location DW 3(see Figure 16, DW 3 is Alt<10), F(1.060, 11.656)=5.884, p<0.031, etap2=0.618 and nosignificant main effect of Wind on altitude deviation at location DW 3 F(1.097, 12.072)=0.651, p=0.449. Five DWs (mean=134.07 sd=204.37) resulted in a significant differencein altitude deviation compared to three DWs (mean=103.22 sd=149.92) and one DW(mean=608.41 sd=1023.40). The difference between five DWs and three DWs was 30.85altitude deviation, three DWs and one DW was 505.19 altitude deviation, and betweenfive DWs and one DW was 474.34 altitude deviation. There was not a significantinteraction effect between DW and Wind on altitude deviation at location DW 3, F(1.211, 13.319)=0.456, p=0.548. Figure 24 shows the mean altitudes at location DW 3.0.00200.00400.00600.00800.001000.001200.001400.001 DW 3 DW 5 DWDW 2 Altitude DeviationsAltitudeDeviationinFeet
  • 39. 32Figure 24: Average Altitude Deviation Main effects on DW 3There was a significant main effect of DW on altitude deviation at location DW 4(see Figure 16, DW 4 is 10nm to SDF), F(1.930, 21.226)=24.958, p<0.000, etap2=1.000,and no significant main effect of Wind on altitude deviation at location DW 4, F(1.382,15.207)= 0.139, p=0.793. Five DWs (mean=284.06 sd=474.33) resulted in a significantdifference in altitude deviation compared to three DWs (mean=1125.86 sd=475.83) andone DW (mean=1408.69 sd=814.50). The difference between five DWs and three DWswas 841.8 altitude deviation, three DWs and one DW was 282.83 altitude deviation, andbetween five DWs and one DW was 1124.63 altitude deviation. There was not asignificant interaction effect between DW and Wind on altitude deviation at location DW4, F (2.178, 23.953)=1.178, p=0.329. Figure 25 shows the mean altitudes at locationDW 4.0.00200.00400.00600.00800.001000.001200.001400.001 DW 3 DW 5 DWDW 3 Altitude DeviationsAltitudeDeviationinFeet
  • 40. 33Figure 25: Average Altitude Deviation Main effects on DW 4There was not a significant main effect at location DW 5 or the IAS conditions.Perceived WorkloadThe results from a 3x1 (DW x Wind) within-subject analysis of variance(ANOVA) revealed a significant main effect of DW on perceived workload, F(1.496,16.451)=77, p<0.000, etap2=1.000. One DW (mean=2.58 sd=0.67) resulted in asignificant difference in workload compared to three DWs (mean=3.25 sd=0.75) and fiveDWs (mean=4.17 sd=0.72). The difference between one DW and three DWs was 0.67perceived workload, three DWs and one DW was 0.92 perceived workload, and betweenfive DWs and one DW was 1.59 perceived workload. Figure 26 shows the meanworkload for each DW condition. A likert scale was used to assess workload (seeappendix G).0.00200.00400.00600.00800.001000.001200.001400.001 DW 3 DW 5 DWDW 4 Altitude DeviationsAltitudeDeviationinFeet
  • 41. 34Figure 26: Workload Main effect on DWPreference Number of DWThe results from a 3x1 (DW x Wind) within-subject analysis of variance(ANOVA) revealed a non-significant main effect of DW on Wind, F(1.877,18.772)=2.031, p=0.161. Figure 27 shows preferred number of DWs for each windcondition.01234561 DW 3 DW 5 DWDWDifficultyfromLowtoHighverage
  • 42. 35Figure 27: Preferred number of DW for each Wind Condition012345SlowWindNormalWindFastWindDWPreferredAverage
  • 43. 36DiscussionHypothesis OneIt was predicted that as the number of Descriptive Waypoints increase, requiredtime of arrival deviation, average power of aircraft, and altitude and IAS deviation willdecrease.Time VariationThere was not a significant effect on time deviation from RTA even though themeans and standard deviation are lower in the five DW condition compared to three DWand one DW conditions. The hypothesis that more DWs would lower the RTA deviationwas not supported by the data. Pilots stated that the target RTA was not enough to keepthem at a consistent time, but they would need RTA and estimated time of arrival (ETA)at each DW to assist them.Power UsageThere was a significant main effect on power usage for DW. This did not supportthe hypothesis that power usage would decrease as the number of DWs increased, but thisoutcome makes sense. Pilots would tend to fly safe and therefore arrive at the DW targetaltitude early, therefore leveling off and increasing power. Overall, in all threeconditions, there was no change in power usage; there was a small increase in powerusage of about one percent in the five DW condition. This could be a drawback to havingmore DWs, but it is important to look at all performance issues before looking at thisnegatively.
  • 44. 37Attitude DeviationStatistical analysis was conducted overall from location DW 2 through 4 to seethe mean altitude deviations and standard deviation. There was a main effect, but not alltargets had a Descriptive Waypoint. For example, at 18,000 feet, location DW 1 wasonly a target for the five DW condition. It was important to examine the standarddeviation at each DW target as well to see the overall spread in altitude for eachcondition. When looking at the standard deviation graph (see Figure 21) the five DWcondition had a noticeably lower standard deviation for each DW target than in the oneand three DW conditions. This is important because it shows that the spread of aircraftaltitude is much tighter in the five DW condition, and this helps ATC with separation ofaircraft. This is important to note because knowing the aircraft trajectory is needed foraircraft separation and ultimately implementation of CDA in higher traffic conditions, asmentioned by Reynolds (2005).There was a significant main effect in the mean altitude at location DW 1. Thismakes sense because the five DW condition was the only condition that had a DW targethere. The standard deviation in the five DW condition was much lower than in the oneand three DW conditions, which shows that there was a tighter grouping of the aircraft inthe five DW condition.There was a significant main effect in the mean altitude at location DW 2. Thismakes sense as well because the one DW condition does not have a DW target here. It isinteresting to see that the five DW condition has the lowest mean and standard deviationcompared to the one and three DW conditions.
  • 45. 38There was a significant main effect in the mean altitude at location DW 3. Wewould expect the one DW condition to have lower altitude deviation here because thisDW target is in a level flight segment of the flight profile. Three and five DW means andstandard deviations where roughly the same, which can be explained by the level flightsegment and by both conditions sharing a previous DW target.There was a significant main effect in the mean altitude at location DW 4. Themean and standard deviations are much lower in the five DW condition, which is good tosee because the DW target is keeping the aircraft altitude spread together. The mean andstandard deviation are a little higher than desired for the five DW condition because afew pilots flew at a higher altitude than the DW 4 target required. This probably was themost difficult DW target to intercept on altitude because pilots were slowing down from240 IAS to 160 IAS, using speed brakes, and flaps while monitoring altitude.There was not a significant main effect at the location DW 5. This makes sensebecause all pilots are at the same speed of 160 IAS and an altitude of 2000 feet. Also,pilots know that it is very important to be at the right altitude before approaching therunway. One pilot flew this target at 5,000 feet altitude in the five DW condition so hisaltitude was modified to 3,000 feet to match the third standard deviation for Figure 20.IAS DeviationThe data did not show any significant main effects at any of the DW targetlocations. This did not support the hypothesis that more DWs would result in less IASdeviation. One reason that this outcome could have happened is that pilots would havenaturally been at the DW IAS target speed just by flying the aircraft at the altitudes theDW targets were set at.
  • 46. 39There was not a significant main effect at location DW 1, which makes sensebecause all aircraft start out at 305 IAS and the first target is 305 IAS.At location DW 2, all aircraft start out at 305 IAS and the first target is 305 IAS.The trend indicates that one-DW aircraft start to deviate here, which suggests that pilotswill slow down earlier if they do not have a hard speed target.At location DW 3, the target speed is now 240 IAS. Aircraft in the five DW andthree DW conditions have a hard speed target, but aircraft in the one DW condition alsohave to be at 240 IAS because once the aircraft gets below 10,000 feet altitude, it ismandatory to be at or below 240 IAS. Aircraft in the one DW have a greater IASdeviation and the standard deviation is much higher as well, compared to three DW andfive DW conditions. The three DW mean and standard deviation would have beenslightly lower, but one pilot came in fast at 300 IAS.At location DW 4, it was surprising that there was not a significant main effectbecause one DW and three DW conditions did not have IAS targets. The aircraft whereslowing down at this point to reach a safe speed for the runway so the IAS for all threeDW conditions were similar.Every DW condition had location DW 5 target and most pilots were already at 160IAS by this point so it makes sense that there was not a significant main effect here andthe standard deviations were very low.Hypothesis TwoIt was predicted that RTA, average power, and altitude deviation will be less forthe nominal wind speed condition in comparison to the slow and fast wind speedconditions.
  • 47. 40Time VariationThe trend is that fast and slow wind conditions had less time deviation than thenormal condition (see Figure 18). This is not what was predicted to happen, but thenormal wind condition had the highest deviation overall. One possibility is that the targettime of 750 second for the normal wind condition was not as accurate of a target RTA tointercept as the 720 second time for fast wind or the 770 seconds for the slow windcondition.Power UsageThere was not a significant effect on power usage for the wind conditions. Theaverage power usage did not change much from any of the wind conditions. It waspredicted that normal wind would have been easiest for pilots to intercept DW altitude,which would have lowered power usage, but the data did not support this hypothesis.Attitude and IAS DeviationThere was not a significant main effect for any altitude or IAS at any of the DWtargets, which was surprising because Koeslag (1999) stated that wind can cause aircraftto deviate from flight path and cause a +/- 2 minute deviation in time IAS Deviation.Also, Ho (2006) stated that pilot’s projection may be incorrect because of winduncertainty. Pilots are more used to the normal wind condition, so altitude and IASdeviation should have been better compared to slow and fast wind conditions. Thedifference in performance probably did not occur because the different wind conditionsdid not create uncertainty for the pilots, but instead just became different descent profilesto manage.
  • 48. 41Hypothesis ThreeAs number of Descriptive Waypoints increase, required time of arrival, averageaircraft power, and altitude deviation will be the same across the different windconditions.Time Variation, Power Usage, Altitude and IAS DeviationThere was not an interaction in any of the conditions. This was surprisingbecause Reynolds (2005) pointed out that structure creates less uncertainty. The idea thatthe uncertainty of the wind conditions would affect the performance in time, power,altitude and IAS deviations and that as number of DWs increased there should have beenreduced uncertainty and create an interaction. As stated earlier, it appears that thedifferent wind conditions did not create the uncertainty to affect performance, so therewas not an interaction.Hypothesis FourAs number of Descriptive Waypoints increase, perceived workload will increase.Perceived WorkloadThere was a significant effect in perceived workload. As number of DWsincreased, so did perceived workload. The main concern is if workload becomes toohigh, the benefits of the DWs will start to diminish. Pilots stated that on the computerthey were only able to manipulate one control at a time and if they were in a cockpit theywould use multiple tools at a time, and that also having a co-pilot would reduceworkload.
  • 49. 42Hypothesis FivePilots will prefer five Descriptive Waypoints in all wind conditions.Preferred DW AmountThere was not a significant main effect on preferred number of DWs. Pilots weregiven a scale to choose number of DW the pilot would prefer to have used ranging fromone through five. The expected outcome was that pilots would prefer five DWs in allwind conditions. Instead, pilots tended to choose one DW or thee DWs. Pilots said thatthe different wind speeds just required adjustments to vertical speed needed. Pilots whoselected one DW liked it for the freedom of constraints, but stated that it is unrealistic.Pilots who selected two DWs liked the ten thousand feet DW 3 target and the 2000 feetDW 5 target. Pilots who preferred three DWs said this condition is realistic and it is whatthey are used too. Pilots also stated that they preferred one DW over three DWs becauseit gave them more freedom over the control of the aircraft but would be unrealistic.
  • 50. 43Subjective Data and FeedbackFlight Chart FeedbackPilots gave a mean score of 4.42 out of 6 with a standard deviation of 1 for usinga vertical flight chart with integrated DW information. Most pilots liked the DW flightchart, but said it was new so they gave it a lower score. Pilots also mentioned they wouldlike the DW information much better in combination with the Jeppesen chart, and preferto have the distance to next DW inserted into DW flight chart, and descent angles (basedon ground speeds).Vertical View of CSD FeedbackPilots gave a mean score of 3.75 out of 6 with SD of 1.22 when asked if the flightpath on the CSD helped them stay on their flight plan. Pilots would like CSD better witha smaller aircraft on screen, bigger flight path, known vertical deviation from flight path,green arc ("banana" for altitude confirmation), and option to zoom in and out. A pilot of aBoeing 757 said his Cockpit setup (vertical NAV screen is next to the regular NAVscreen on the right) is similar to what was done in the study. Pilots would also likeestimated time of arrival to each Descriptive Waypoint. A pilot who flies a Boeingaircraft said he had a display that had an energy management arrow, similar to Figure 4,which would be very helpful for flying CDA.DW FeedbackPilots gave a mean score of 4.67 out of six with SD of 0.78 when asked if theywere comfortable with the DW target locations in the flight plan. Pilots liked the spacingand how 10,000 feet altitude helped them slow down. One pilot said that it was difficult
  • 51. 44for him to slow down at 10,000 feet from 240 IAS to 160 IAS until the end of thescenario.When asked how DWs help pilots fly CDA, the pilots responded it gives crosschecks that help determine descent rates and to know if they are on the flight path andtarget; two pilots felt that it was necessary to have something tell if they are off the flightpath.When asked how much distance should be between each DW, pilots said rangesfrom no less than 5nm to 30nm. Pilots preferred 10-30nm and only less distance forprecision closer to airport.When asked if DW helped manage vertical speed eight, pilots said yes, butcautioned that too many DWs increase workload. Two pilots said no because it increasedworkload and the pilots had to generate their own descent rates.When asked if DW helped the pilot manage vertical speed, pilots felt that the10,000 feet (location DW 3) and location DW 5 were only necessary for speed. One pilotmentioned that he would like a target to let pilots know when to initiate slow down. Twopilots mentioned they would fly quicker without restrictions.When asked if DW helped pilots with RTA, they responded no for the most part.Pilots in general did not pay attention to it after 10,000 feet altitude. Pilots mentionedthey would pay attention to RTA more if it was provided for each DW target.When asked if DW helped reduce power usage of the aircraft, half the pilots saidyes, if planned correctly to intercept DW altitude. If early to altitude before DW target, itcreates level off section, which increases power usage. Pilots mentioned that with the
  • 52. 45green arc tool in their NAV display, they would get to the DW altitude target withoutleveling off.Pilot StrategiesWhen pilots were asked what were their strategies and priorities were (power/fuel,waypoints, RTA, etc.), ten pilots put DW targets as top priority, one pilot put power astop priority, and one put RTA as top priority. For the second priority, ten pilots putpower and two put DW targets. For the third priority, eleven pilots put RTA, and onepilot put power. Other goals pilots said they focused on were minimal speed brakes andvertical speed. One pilot put a priority on groundspeed.The pilots’ rule of thumb for managing vertical speed is a three to one ratio: forevery 1,000 feet, it takes three miles, groundspeed divided by 60 gives miles travelled perminute (use this into distance to next DW). Pilots felt DWs were just a target to confirmthat they were on the flight plan.The pilots’ rule of thumb for decelerating was one nm for each 10knts in levelflight, use of minimal speed brakes and flaps. One pilot said just use speed brakes andflaps, and one pilot said educated guessing.When asked how pilots adjusted vertical speed or deceleration when they werecoming into a DW target, pilots stated that when coming in too fast they would reducevertical speed, and when coming in too slow, increase vertical speed. One pilot said justmake up for it at the next target when off target.When asked how to adjust for RTA, pilots stated fly profile and hope to make it.Three pilots said that they would slow down and speed up after 10,000 feet altitude(location DW 3) to adjust for RTA.
  • 53. 46When asked what was the strategy for speed brakes during CDA, three pilotsstated they used brakes to slow down after 10,000 feet altitude (location DW 3). Most ofthe pilots said they use brakes as little as possible and used flaps as needed.Feedback on CDA scenariosWhen asked about the realism of these scenarios, pilots felt it was realistic, butsaid they would fly better in aircraft, having a copilot and with tools such as green arc.When asked what would be the functions of the pilot flying, they stated the pilotwould fly vertical speed and IAS, make decisions for making DWs, and vocalize plan andcallouts to pilot monitoring.For the function of pilot monitoring, they stated pilots would monitor targets, airspeed, IAS, and DWs, do all calculations for pilot flying, setting altitudes, MCP, work thegear and flaps, crosschecking altitude inputs, and talking to ATC.One pilot commented that workload should be lowered after 10,000 feet altitude(location DW 3).
  • 54. 47LimitationsThe DWs were used with limited aircraft automation to determine the effects ithad on pilot performance. In an actual aircraft, pilots would have the option to use flightlevel change (FLCH), or VNAV where they felt necessary. Also, there would be a co-pilot to help with calling out altitude changes at each DW to ensure the pilot did notforget or miss DW fixes. Another limitation, which also increased perceived workload,was using the knobs of the MCP to control speed brakes, and flaps. Unlike the software,in a real aircraft multiple knobs can be used simultaneously. Also, if pilots left speedbrakes on in a real aircraft they would feel the drag, hear a beep, and know to turn it off.With the software, pilots had to visually see that the speed brakes were still on to turnthem off. This resulted in some pilots leaving speed brakes on longer than they intended.Another limitation, which was a research design choice, was not allowing pilots tomanipulate the CSD. This was to limit workload and training, but pilots felt that theywould have zoomed in more to the aircraft once they passed the 10,000 feet DW 3 target.A final limitation was that this study was a part-task simulation and that pilots would beengaging in more tasks in an actual flight and be in an environment that they are used to.
  • 55. 48Future ResearchIt would be interesting to see future studies use a full simulation with allautomation tools available to pilots, have a copilot or a researcher act as one, and includeDW information in a Jeppesen chart with the DW chart. Other useful research would beto provide an updated DW chart with distance to each DW and angle of descent for eachDW; integrate DW targets into CSD or another vertical display; use DW with CSD 3Dguidance, traffic avoidance and terrain.
  • 56. 49ConclusionThis study had three main goals for the pilots: RTA, managing power, andintercepting DWs on altitude and IAS. RTA was shown to be difficult to manage forpilots with just the DWs, but in combination with projected ETA and updated timetargets based on wind, this would help pilots predict and manage when aircraft will be ateach DW and the runway, which would help with traffic throughput to the airport. Thefive DW condition used slightly more power (one percent) than the one and three DWconditions. With automated assistance (such as the green arc), the pilots believed thatthey would use less power by intercepting the DW altitude target without resorting tolevel flight. An important part of this study was the pilot’s ability to intercept DWtargets. The five DW condition gave structure for the pilots, and the aircraft consistentlyflew similar flight paths and were closer to their DW target altitudes, which is importantfor aircraft separation, especially in higher traffic conditions. DW 3 target at 10,000 feetaltitude was seen as the most important DW by the pilots. This gave the pilot time to losespeed and get the aircraft ready for approach to the runway. DWs will help ATC withaircraft separation, which would ultimately make CDA more feasible in high trafficconditions. Pilot perceived workload went up as the number of DWs increased, but thiscould be reduced with a co-pilot and a more realistic simulation in which multiple knobs,and automation are available to help with prediction of future altitude based on currentdescent rates.The results of increasing performance in the three and five DW conditions supportuse and implementation of DW into CDA procedures. With the recommended changesby pilots to the DW flight chart with distance to each DW, angle of descent, and
  • 57. 50implementation of DW into vertical NAV display this would make the pilots morecomfortable with flying CDA with DWs and achieve the desired noise and fuel reduction,meet RTA requirements, and altitude and IAS targets.
  • 58. 51ReferencesClarke, J-P., B., Ho, N. T., Ren, L., Brown, J. A., Elmer, K. R., Tong, K-O & Wat, J. K.(2004). Continuous Descent Approach: Design and Flight Test for LouisvilleInternational Airport. Journal of Aircraft, 41(5), 1054-1066.Clark, J-P., Bennett, D., Elmer, K., Firth, J., Hilb, R., Ho, N., Johnson, S., Lau, S., Ren,L., Senechal, D., Sizov, N., Slattery, R., Tong, K., Walton, J., Willgruber, A.,Williams, D. (2006). Development, Design, and Flight Test Evaluation of aContinuous Descent Approach Procedure for Nighttime Operation at LouisvilleInternational AirportCoppenbarger, R., Mead, R., Sweet, D., (2009). Field Evaluation of the Tailored ArrivalsConcept for Datalink-Enabled Continuous Descent Approach. Journal ofAircraft, 46(4), July–August 2009Cowen, M., John, M., Oonk, H., & Smallman, H. (2001). The Use of 2D and 3DDisplays for Shape-Understanding versus Relative-Position Tasks. HumanFactors, 43(1), 79-98.Global Aviation Navigation, Inc., (2009). Retrieved May 2009, fromhttp://www.globalair.com/d-TPP_pdf/00239IL17R.PDFHo, N. T., Clarke, J-P., Riedel, R., & Omen, C. (2006). Development and Evaluation of aPilot Cueing System for Near-Term Implementation of Aircraft Noise AbatementApproach Procedures.Koeslag, M. F., (1999) Advanced Continuous Descent Approaches –An algorithm designfor the Flight Management System-.
  • 59. 52Lowther, M. B., Clarke, J-P., & Ren, L., (2007). En Route Speed Change Optimizationfor Spacing Continuous Descent ArrivalsMoore, S. (2009). Benefits of Highly Predictable Flight Trajectories in PerformingRoutine Optimized Profile Descents: Current and Recommended Research.Environmental Working Group Operations Standing Committee2009 Annual Workshop, NASA Ames.Prevot, T., (1998). A Display for Managing the Vertical Flight Path - an AppropriateTask with Inappropriate Feedback-. International Conference on Human-Computer Interaction in Aeronautics Montreal, Canada, 1998Prevot, T., Callatine, T., Kopardekar, P., Smith, N., Palmer, E., Battiste, V., (2004).Trajectory-Oriented Operations with Limited Delegation: An Evolutionary Path toNAS Modernization. AIAA 4th Aviation Technology, Integration and Operations(ATIO) Forum, Chicago, IL, September 2004.Reynolds, H., Reynolds, T. & R. Hansman, J. (2005). Human Factors Implications ofContinuous Descent Approach Procedures for Noise Abatement in Air TrafficControl. 6th USA/Europe Air Traffic Management R&D Seminar, Baltimore,USA, June 27-30.Reynolds, H. (2006). Modeling the Air Traffic Controller’s Cognitive ProjectionProcess. MIT International Center for Air Transportation Department ofAeronautics & Astronautics Massachusetts Institute of Technology Cambridge,MA, 2006
  • 60. 53Symmes, D., & Pella, J. (2005). Three-Dimensional Image. Microsoft® Encarta® 2006[CD]. Redmond, WA: Microsoft Corporation, 2005.Thomas, L. & Wickens, C. (2005). Display Dimensionality and Conflict GeometryEffects on Maneuver Preferences for Resolving In-Flight Conflicts. Proceedingsof the Human Factors and Ergonomics Society 49thAnnual Meeting.Thomas, L. & Wickens, C. (2006). Individual Effects of Battlefield Display Frames ofReference on Navigation Tasks, Spatial Judgments, and Change Detection.Ergonomics, 49, 154-1173.Williams, D. (2008). Flight Deck Merging and Spacing and Advanced FMS Operations.EWG Operations Standing Committee Meeting.
  • 61. 54Appendix A: Example Flight Chart
  • 62. 55Appendix B: Training Manual
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  • 70. 63Appendix C: Orientation PowerPointSILENT DELIVERIESContinuous Descent Approach (CDA)Overview1
  • 71. 64Company Overview• We are a delivery company that fly 757’s at night• To keep residents happy around airports we use CDA(keeps noise low on ground by using low power)• We also try to be as efficient as possible bymaintaining a time schedule by arriving at airport atspecified times2
  • 72. 65Current Problem with Conventional Approach• Cost of fuel = 27% operation cost toairlines• People complain about loud aircraft noisenear airports• Can’t expand runways• Limited air craft throughput atnightImplementation challenges for CDA:• Pilots have difficulty maintaining vertical flight profile without automationWhy use Continuous Descent Approach?• Idle engine• Less noise is produced• Less fuel is consumed~220lbs• Fewer emissions produced10,000Feet4,000feetILS GlideSlopeRunwayyyyyyyContinuousDescent ApproachConventionalApproach
  • 73. 66Company Objectives for CDA1. Intercept all of the Descriptive Waypoints (DW) atthe specified altitude (range of +/- 300 feet) andspecified IAS targets (range +/-5 IAS)• A speed restriction to IAS is that the pilot mustkeep under 250 IAS below 10,000 altitude2. Intercept last DW at Required Time of Arrival(RTA) within 30 seconds3. Attempt to keep aircraft power below 10%, butkeep it as close to 0% as possible• From 10,000 altitude to last waypoint powershould be monitored more closely 4
  • 74. 67Appendix D: Training ChecklistTraining checklist (experimenter checklist to have pilot do)1. On MACS, please point out the following on the Mode Control Panel(MCP):a. Vertical Speedb. Vertical Speed Buttonc. Indicated Air Speedd. Indicated Air Speed Knob2. Point out the speed brakes, landing gear, and flaps3. Where is the aircraft power level on the PFD?4. Where would the flap indicator cues be on the PFD?5. When does the landing gear need to be used by?6. Point out where is wind speed and direction located on navigation display.
  • 75. 68Appendix E: Practice Run ChecklistPractice Run (experimenter checklist to have pilot do)Complete the following:1. On Macs, please interact with the following Mode Control Panel (MCP)tools as stated by experimenter:a. State current Vertical Speedb. Decrease Vertical Speedc. Increase Vertical Speedd. State Indicated Air Speede. Increase Indicated Air Speed by using IAS Knobf. Decrease Indicated Air Speed by using IAS Knob2. Use speed brakesa. Midb. Fullc. Turn speed brakes off3. Lower landing gear then retract it4. State current power level of aircraft5. How many nm is aircraft from next DW?6. State current wind speed7. After Cheri, instruct pilot to Alt<10 intercept DW +/- 300 feet and 5 IAS8. At Alt<10 instruct pilot to intercept last DW in five minutes and 30 seconds(+/- 30 second buffer)9. When aircraft gets to appropriate speed point out the flap indicator on pfdand instruct pilot to use flaps according to MACS PFD indicator10.Remind the pilot of the 250 kts speed limitation if he misses it.11.If pilot doesn’t use landing gear by 5.5 nm remind them to use it.12.At end of practice remind pilot that the goals are on a piece of paper nextto the training manual on the table and then give a breakNotes: Pay attention for how long it takes pilots to do tasks asked by pilot
  • 76. 69Appendix F: Pilot ResponsibilitiesPilot ResponsibilitiesThe three goals for CDA starting with highest priority are:1. Achieve all of the Descriptive Waypoints (DW) at the specified altitude(range of +/- 300 feet) and IAS targets (range +/-5 IAS) A restriction to IAS is that the pilot must keep speed under 250 IASbelow 10,000 altitude2. Achieve last DW at RTA within 30 seconds.3. Attempt to keep aircraft power below 10%, but keep it as close to 0% aspossible From 10,000 altitude to last Descriptive Waypoint power should bemonitored more closely Be careful not to leave speed brakes on when preferred speed is metto avoid power spikes LNAV will be turned on so navigation is not required VNAV will be turned off: vertical navigation by pilot will be required Pilots must use flaps as required as is indicated on PFD Pilots must have the landing gear down by 5.5 nm from SDF
  • 77. 70Appendix G: Debrief/ QuestionnaireThere are two main elements examined today. These are1. Descriptive Waypoints (DW)2. Wind ConditionsThe DW examined today was to help give extra guidance to the pilot while landing continuous descentapproach. Also it was important to not only see if the DW helped out in an optimal environment, but ifthey help out during different wind conditions. For each question below, please assess your level ofcomfort and explain any reservations you might have.1. How do you feel your work load was on the one DW Scenario? (circle one)1 2 3 4 5 6Very Low Low Moderately Low Moderately High High Very High2. How do you feel your work load was on the three DW Scenario? (circle one)1 2 3 4 5 6Very Low Low Moderately Low Moderately High High Very High3. How do you feel your work load was on the five DW Scenario? (circle one)1 2 3 4 5 6Very Low Low Moderately Low Moderately High High Very High4. How do you feel your work load was on the Slow Wind Scenario? (circle one)1 2 3 4 5 6Very Low Low Moderately Low Moderately High High Very High5. How do you feel your work load was on the Normal Wind Scenario? (circle one)1 2 3 4 5 6Very Low Low Moderately Low Moderately High High Very High6. How do you feel your work load was on the Fast Wind Scenario? (circle one)1 2 3 4 5 6Very Low Low Moderately Low Moderately High High Very High
  • 78. 717. Today you flew multiple scenarios varying the wind and number of DW’s. What number of DWhelped you fly the CDA the most for each wind conditions? (circle one)a. Slow Wind 1 DW 3 DW 5 DWb. Normal 1 DW 3 DW 5 DWc. Fast 1 DW 3 DW 5 DW8. How would different wind conditions affect how you fly CDA with DW?9. How comfortable would you feel flying CDA using DW implemented into an approach flight chartsimilar to the one you used today in a real life scenario?1 2 3 4 5 6Very Uncomfortable Somewhat Somewhat Comfortable VeryUncomfortable Uncomfortable Comfortable ComfortableWhy?10. What DW information would you want incorporated into an approach flight chart for CDAapproaches?
  • 79. 7211. Did the vertical profile view on the CSD screen help you stay on the flight plan?1 2 3 4 5 6Very Uncomfortable Somewhat Somewhat Comfortable VeryUncomfortable Uncomfortable Comfortable ComfortableWhy?12. What would you want the Navigation Display and or Vertical Display screen to show you when youfly CDA? How would you integrate DW into these Displays?13. Were you comfortable with the locations of the DW’s?1 2 3 4 5 6Very Uncomfortable Moderately Moderately Comfortable VeryUncomfortable Uncomfortable Comfortable ComfortableWhy?14. a. How many DW would you feel would be optimal to help you fly CDA? (could be any number)and why?b. How does DW help you fly CDA? Why
  • 80. 73c. How much distance should be between each DW? Why?d. Did the DW help you manage your vertical speed? Why?e. Did the DW help you mange IAS speed during CDA? Why?f. Did the DW help with making the RTA target? Why?g. Did the DW help you keep the power of your aircraft low? Why?
  • 81. 7415 a. How many nm from airport is a good place to start CDA? Why?b. What altitude?16. What was your strategy and priorities (power/fuel, Descriptive Waypoints, RTA, etc.) while flyingCDA? Please give a rank list and then list your technique for flying CDA.Strategy:1.2.3.4.5.Techniques17. a. What is your rule of thumb for managing vertical speed during CDA? Did DW help with your ruleof thumb?b. What is your rule of thumb for managing deceleration during CDA? Did DW help with your rule ofthumb?
  • 82. 75c. How did you make an adjustment to your vertical speed or deceleration when you intercept DW ifyou are too fast/slow? Or at the wrong altitude?d. If you were behind or ahead of RTA how did you adjust for it?e. What was your strategy for using speed brakes and flaps during CDA?18. What do you think of the realism of these scenarios?
  • 83. 7619. Today you flew CDA with the LNAV on and the VNAV off, what functions do you think thePilot Flying and Pilot Not Flying would be responsible for while flying this procedure in a realscenario?20. Any other feedback you have about the DW’s and flying CDA today?