Aircraft Operating Characteristics

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Airport Operations and Management Course (MSc ITA,2007)

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Aircraft Operating Characteristics

  1. 1. INSTITUTO TECNOLÓGICO DE AERONÁUTICA DIVISÃO DE ENGENHARIA DE INFRA-ESTRUTURA AERONÁUTICA DEPARTAMENTO DE TRANSPORTES “Aircraft Operating Characteristics” Chapter 4 - Airport Operations Ashford,N. et.al. IT 204 Análise Operacional e Gerencial de Aeroportos José Alexandre T.G.Fregnani 21/03/2007
  2. 2. AO4 - Aircraft Operating Characteristics Index 1. General Considerations 2. Departure Performance 3. Approach Performance 4. Operations in inclement weather 5. New Large Aircraft GENERAL / DEPARTURE / APPROACH / INCLEMENT WEATHER / NLA 1/24
  3. 3. AO4 - Aircraft Operating Characteristics General Considerations : Characteristics •The function of the design and operation of runways and their approaches must allow safe transition between flight and ground maneuvering. • Aircraft operations close do the ground : Low speeds (80 to 150Kt). Extremes of lift and control envelopes. Expose the aircraft to risk of contact with ground. • Aircraft Performance must match carefully with airport´s infrastructure: Ground Maneuvering. Capability to climb and descent over obstacles. GENERAL / DEPARTURE / APPROACH / INCLEMENT WEATHER / NLA 2/24
  4. 4. AO4 - Aircraft Operating Characteristics General Considerations : Aircraft Performance • Aircraft Performance has a huge impact on airline economics. • Reductions of payload ( indireclty weight) indicate large reductions in potential profit. GENERAL / DEPARTURE / APPROACH / INCLEMENT WEATHER / NLA 3/24
  5. 5. AO4 - Aircraft Operating Characteristics General Considerations : Aircraft Performance •Aircraft performance is primarly a function between the excees of thrust to drag and excess of lift to weight. LIFT – L THRUST -T LIFT L θ γ DRAG – D DRAG D W•cos γ WEIGHT - W W•se T − D 1 dv nγ tan (γ ) = climb gradient = − • W g dt THRUST - T T D = W L WEIGHT - W • At a given speed drag is a function of lift and therefore weight. • Weight is the principal variable for Field lengh and Climb capability (WAT and Obstacle clearance). Therefore weight is the most important factor for both Performance and Economics ! GENERAL / DEPARTURE / APPROACH / INCLEMENT WEATHER / NLA 4/24
  6. 6. AO4 - Aircraft Operating Characteristics General Considerations : Matching Infrastructure • Operators will not use airfields where significant reduction of payload is required or are not adequate for the aircraft size. • There is an economic limit to the airport operator´s ability to: Extend Field Lengh and Protect Obstacle Clearance Surfaces. Principles in matching aircraft to the infrastructure: 1. 2. 3. 4. Demonstrated Performance of the aircraft; Use of Net Performance; Assesment of Probability of failure (safety assesment); Regulation of operations (JAR-OPS1/FAR 121) and performance (JAR/FAR 25). GENERAL / DEPARTURE / APPROACH / INCLEMENT WEATHER / NLA 5/24
  7. 7. AO4 - Aircraft Operating Characteristics General Considerations : Takeoff Field Lenght Required • • All Worldwide takeoff Regulations are based on FAR25 or JAR 25. Takeoff distance demonstration is based on OEI or AEO configurations. • Acel-Go distance Acel-Stop distance 1 sec. from Vef to V1. • All Engines distance Takeoff Field Lenght Required is the maximum of: • • • 1.15 x All Eng.Distance Acel-Go distance. Acel-Stop distance. GENERAL / DEPARTURE / APPROACH / INCLEMENT WEATHER / NLA 6/24
  8. 8. AO4 - Aircraft Operating Characteristics General Considerations : Takeoff Field Lenght information • Runway dimensions Information may be found in AIP (Aeronautical Information Publication) and NOTAM (Notice to Airman). • When limited by climb capability (WAT or Obstacle), the excess of ASDA may be used to increase energy and improve climb gradient. Higher takeoff speeds are expected (V1.VR andV2). → this is called IMPROVED CLIMB or OPTIMUM V2 technique. GENERAL / DEPARTURE / APPROACH / INCLEMENT WEATHER / NLA 7/24
  9. 9. AO4 - Aircraft Operating Characteristics General Considerations : Risk Analysis • Risk of na accident per flight is acceptable, cathegorized and quantified. • Under and Overshoot analysys (Monk 1981). • RESA of 1000 ft beyond runway strip would contain half of the under/overshoot accidents. • Better to Go-Around !!! GENERAL / DEPARTURE / APPROACH / INCLEMENT WEATHER / NLA 8/24
  10. 10. AO4 - Aircraft Operating Characteristics General Considerations : Risk Analysis • It is possible to construct protected airspace surfaces to limit the probability of aircraft outside them to the remote risk category (10-7). •Safety requirements and economical operations may not go in the same direction(Ex: OEI perf. x minimum Fuel Climb). • More severe operational limitations are set once the risk increases. GENERAL / DEPARTURE / APPROACH / INCLEMENT WEATHER / NLA 9/24
  11. 11. AO4 - Aircraft Operating Characteristics Departure Performance : Takeoff facts • Takeoff performance is based on on screen height of 50 ft over threshold, in case of Acel-GO condition. • 2 seconds added for pilot´s reaction time between V1 and initial braking action. • JAR 25 requires wet runway performance accountability for all aircraft models. This states 15 ft screen height (Acel-GO) , V1set 4 secs earlier and one thrust reverser credit is allowed (Acel-STOP). •.Until 1998 the FAA did not require wet runway accountability, but it is now required for airplanes certified post FAR 25 Amendment 25-92. • Takeoff Overrun incidents : • Related to pilot´s training and V1 concept (see slide 11). • Moving the Airport Operator for provision of RESA (Runway Excursion Safety Area) in addition to strip and prepared stopway. GENERAL / DEPARTURE / APPROACH / INCLEMENT WEATHER / NLA 10/24
  12. 12. AO4 - Aircraft Operating Characteristics Departure Performance : Takeoff Safety Training Aid ( Boeing,1998) • Analysis of all Jet Transport overrun incidents/accidents statistics between 1950 and 1997. • Results: In more than 75% of the events, aircraft were able to fly with all engines operating. Most of overruns occurred above 80 KIAS, with high energy and therefore difficulty on braking for complete stopping. Less than 25% of the incidents were related to OEI or Fire. • Actions: V1 seen as an action speed ( the decision must be made before). FirstPilot´s action to braking the aircraft must occur at V1. Only reject takeoff above 80 kt in case of OEI, Fire or Aircraft broken. Pilot´s training: V1 callout made 5kt earlier. Change in regulations : FAR/JAR 25. GENERAL / DEPARTURE / APPROACH / INCLEMENT WEATHER / NLA 11/24
  13. 13. AO4 - Aircraft Operating Characteristics Departure Performance : Takeoff Climb Gradients • One Engine Inoperative Climb requirements (FAR 121 and 135 aircraft): Gross Climb Gradient Required Climb Segment 1st 2nd 4th 2 ENG 0.0% 2.4% 1.2% 3 ENG 0.3% 2.7% 1.5% 4 ENG 0.5% 3.0% 1.7% • All engines Climb: Gross gradient reduced by 3.2%. JAR requires minimum of: 5.2% (2nd) 4.1% (4th) CON thrust • Light aircraft (general aviation) : “See and avoid obstacles below clound base” GENERAL / DEPARTURE / APPROACH / INCLEMENT WEATHER / NLA 12/24
  14. 14. AO4 - Aircraft Operating Characteristics Departure Performance : Special Takeoff Procedures • “Get them high early” technique (ATA). Derivative from recommended ICAO NAP procedure. Close monitoring of pitch angle with V2+10. Thrust reduction at 1500ft AGL. • “Full Clean-up” technique (ATA): Maintain Takeoff thrust until flaps retracted. Fuel economy (159kg B737) but reduction on engine´s life. GENERAL / DEPARTURE / APPROACH / INCLEMENT WEATHER / NLA 13/24
  15. 15. AO4 - Aircraft Operating Characteristics Departure Performance : Takeoff Limitations • Any margin between the MTOW and Actual Takeoff Weight may be used for Fuel Tankering or; • Other economic or environmental considerations : noise, emissions,etc.. GENERAL / DEPARTURE / APPROACH / INCLEMENT WEATHER / NLA 14/24
  16. 16. AO4 - Aircraft Operating Characteristics Approach Performance : Landing factors • FIELD LENGTH LIMITS (FAR 121.195 and JAR-OPS-1.515.): ACTUAL LANDING DISTANCE demonstrated in flight test as follows: V/S < 6 ft/sec at 3 deg glide slope. Zero slope, smooth, DRY, hard surface runway. Manual Wheel braking. Other braking devices: auto spoilers deployment. All data reduced to ISA Temperature. Vref at 50 ft over threshold. Vref = 1.23Vs1g No reverse thrust credit. GENERAL / DEPARTURE / APPROACH / INCLEMENT WEATHER / NLA 15/24
  17. 17. AO4 - Aircraft Operating Characteristics Approach Performance : Landing characteristics • Correct conditions at the threshold are important to provide the predicted landing performance. • Stabilized Approach Concept is necessary: Correct height (52ft for a glide path of 3 deg). Correct Speed : Vref. Adequate rate of descent: from 500 to 1000 ft/min. Adequate thrust. On glide path. Decision Height(DH) and Runway Visual Ranges (RVR) for Precision Approaches. CAT DH (ft) RVR (m) I 200 800 II 100 400 IIIa N/A 200 IIIb N/A 50 • Ground aids must be satisfactory to provide adequate performance : PAPI and VASIS systems for visual. • Full precision approach (ILS CAT I/II and III) are the best aid to accurate flying. Autoland and Head Up Display guidance may be used. GENERAL / DEPARTURE / APPROACH / INCLEMENT WEATHER / NLA 16/24
  18. 18. AO4 - Aircraft Operating Characteristics Approach Performance : Missed Approach performance In Cruise Configuration Required a Positive Net Gradient at 1500ft AGL with OEI. GENERAL / DEPARTURE / APPROACH / INCLEMENT WEATHER / NLA 17/24
  19. 19. AO4 - Aircraft Operating Characteristics Approach Performance : Obstacle Clearance • Approach path must maintain obstacle clearance on expected flight path. • ICAO Doc. 8168 defines how to design approach procedures, defining MDA/MDH and DA/DH. • ICAO Annex 14 defines airport protection areas. GENERAL / DEPARTURE / APPROACH / INCLEMENT WEATHER / NLA 18/24
  20. 20. AO4 - Aircraft Operating Characteristics Approach Performance : Special Approaches • Reductions on noise/ fuel are obtained avoiding unecessary drag on delaying flaps and gear selection as much as possible. (Lufthansa : B737 / 200 kg). • Two Segment Approaches. • “High and Fast” , unconfottable for pilots (R/D higher than1000 ft/min on final approach). • NASA CDA (Continuous Descent Approach) : tailored arrivals.pdf • Constant Mach/IAS • Decel at 15000 ft to Initial Approach speed. • Continuous descent down to FAF. GENERAL / DEPARTURE / APPROACH / INCLEMENT WEATHER / NLA 19/24
  21. 21. AO4 - Aircraft Operating Characteristics Inclement Weather • Inclement weather conditions have direct impact on runway capacity, due to the increased occupancy time. Runway Capacity reduction is function of: Wake turbulence (vortex systems). IFR Operations. Autoland (requires extended flare). Increasing braking distances on wet,contaminated and slippery runways and thus decreasing values of high speed exits (15 kt on slippery / 40 kt on dry rwy) • Author suggests the design of exit locations based on poor landing performance. • Croswind Effect : limitations on Flight Manuals depending on runway conditions (10 kt limitation is usually set for WET runways). Critical for STOL aircraft. • Performance dificulties may arise with standing water, snow, slush or ice. Large reductions on V1 and payloads are expected. GENERAL / DEPARTURE / APPROACH / INCLEMENT WEATHER / NLA 20/24
  22. 22. AO4 - Aircraft Operating Characteristics Inclement Weather : Braking friction • Airport authorities report the friction characteristics of the runways using friction measuring devices (skidometer, mu-meter, friction tester, etc…) •These reported friction characteristics, however, do not represent the actual aircraft braking friction, as many variables like aircraft weight, speed, braking mechanism, tire and undercarriage characteristics are not considered on its determination. • The measured characteristics are reported by the airport authorities as "Reported Braking Action“. • “GOOD” means no directional difficulties ( as in a WET runway) Reported Braking Action Reported Friction Coefficient (ICAO) Good (wet runway) 0.40 and above Medium to good 0.39 to 0.36 Medium 0.35 to 0.30 Medium to poor 0.29 to 0.26 Poor ( wet ice) 0.25 and below GENERAL / DEPARTURE / APPROACH / INCLEMENT WEATHER / NLA 21/24
  23. 23. AO4 - Aircraft Operating Characteristics Inclement Weather :Windshear • Windshear is defined as a rapid and strong variation of wind speed/direction in a given altitude within a short distance. • Most of the times is associated to variable winds near surfaces due to thunderstorm cells (called Microbursts). • Strong variable gusts may invert tail to headwinds almost immediately, leading the aircraft to AOA variation near to stall. • Low Level anemometers system may me installed at periphery of airport area, in order to provide warning alerts to pilots. • Windshear scape guidance on aircraft´s F/D. GENERAL / DEPARTURE / APPROACH / INCLEMENT WEATHER / NLA 22/24
  24. 24. AO4 - Aircraft Operating Characteristics New Large Aircraft • In recent years there have been considerable discussion concerning the introduction of aircraft capable to carry 800 to 1000 PAX. • A380 operational in 2Q/2007 and B747-8 in 1Q/2009 are real examples. Larger dimensions and weights than current heavy aircraft are expected. • Some problems are evident to Airport Infrastructure and capability: Vortex systems : runway ocupancy time extended due to larger separations. Increased taxiways, runways, aprons lateral separations; Cleaning and servicing. Loading passengers and cargo. GENERAL / DEPARTURE / APPROACH / INCLEMENT WEATHER / NLA 23/24
  25. 25. AO4 - Aircraft Operating Characteristics New Large Aircraft : Are the airports prepared ? GENERAL / DEPARTURE / APPROACH / INCLEMENT WEATHER / NLA 24/24
  26. 26. AO4 - Aircraft Operating Characteristics THANK YOU ! José Alexandre T. Guerreiro Fregnani jose.guerreiro@embraer.com.br xanlu2@terra.com.br

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