The accident case that we will be reviewing today is NTSB accident number NYC05MA039 which occurred in Oxon Hill, Maryland during the winter of 2005. The approach that we will take will be to first review some basic facts about the accident flight, the pilot, and the aircraft and then we will look at several key points along the accident route and explore how HTAWS might have broken the accident chain at each of these points along the way.
Quickly review the mission summaryAs we can see from the informationon this slide, the flight was a seemingly routine night repositioning flight in advance of a HEMS mission.The total flight planned distance was a relatively short 38 nautical miles.
Quickly review the weather observationThe weather observation above was from the DCA automated surface observing system located approximately 3.5 NM north of the accident site and was reported at 2251 local time.
Here we can see the pilot’s ratings, medical status, and total flight time.Question:By a show of hands:How many pilots in our group today have qualifications and total flight time similar to the pilot in this report?
At the time of the accident, this was a relatively new aircraft having accumulated 166.6 airframe hours. The inspection status was current and the aircraft was flying with a properly deferred inoperative radar altimeter.Question:By a show of hands:How many fly a helicopter that is not equipped with a radar altimeter?
Even before lift off, the pilot would have had a distinct advantage had his aircraft been equipped with an HTAWS system. Depending on the system, it might have provided the pilot with a display of surrounding airports, nearby traffic, a flight plan display, and a graphical depiction of terrain (including water bodies) and obstacles - possibly even transmission lines.With this information available, the pilots situational awareness is already at a higher level: In this case with the route the pilot is following being primarily over the river, the water depiction would be an aid to his positional awareness. With display of airports, the pilot can see areas that he needs to remain clear of. An airport display may help the pilot gain an expectation of where he may encounter traffic arriving and departing from a given airport. A flight plan display might allow for a detailed multi-leg flight plan line to be displayed which depicts the exact route to be flown.
At approximately 2311:20 ATC advises “Washington tower traffic on a ten mile final is an Airbus”. Use of an HTAWS incorporating a TCAS display might have enabled the pilot to more readily determine the position of the traffic called out by ATC with a minimal interruption of the pilot’s instrument scan by presenting the relative position, altitude, and vertical trend information of the traffic. Additionally, an HTAWS with a radar altimeter display, a display of water bodies, and a flight plan line display would all contribute to reducing the overall work load and at the same time help the pilot to fly this route precisely. This sort of information could have contributed to an overall increase in situational awareness lowering the risk of the mission.
The pilot may have observed traffic on the HTAWS display, much like in the example shown above.
At 2311:30 near the Woodrow Wilson bridge, the pilot responds to ATC “Roger, we have him in sight and will be out of his way. This is the last transmission made by the pilot. The controller replies with “…maintain visual separation from traffic. The NTSB report states that a helicopter pilot familiar with the route flown stated: “Flying at night North to South over the Woodrow Wilson bridge is very similar to going into actual instrument conditions. A pilot flying low-level North of the bridge is typically flying VFR due to the intense amount of ground lights available along the river. Once the pilot crosses the bridge, he is now flying into a black void. At this point an instrument scan must be established to maintain altitude. Because of the close proximity to water…a radar altimeter is necessary to ensure altitude awareness”. The FAA Airplane Flying Handbook FAA-H-8083-3A states the following about night flying: “Night flying requires that pilots be aware of, and operate within, their abilities and limitations. . . . Night flying is very different from day flying and demands more attention of the pilot. The most noticeable difference is the limited availability of outside visual references. Therefore, flight instruments should be used to a greater degree.” Flying an aircraft equipped with an HTAWS incorporating a traffic display, the pilot might have been able to reduce his time scanning for traffic and maintain a more vigilant instrument scan possibly preventing this accident.
At point C the aircraft entered the fatal descent. Whether it was caused by disorientation due to the lack of ground references or because the pilot was still scanning for traffic or perhaps for some other reason, the aircraft entered a gradual descent and right bank and shortly thereafter impacted the water.The eyewitness account of the surviving passenger indicated that because of the traffic, the pilot made a change in flight path and started to descend. This correlates to the statement in the NTSB report that the aircraft entered the descent almost coincident with the report that the pilot made that he was looking for the approaching aircraft.HTAWS may have been crucial at this point in a number of ways:As previously mentioned, the traffic that the pilot was watching for may have been displayed on the HTAWS allowing the pilot to maintain a closer instrument scan.The HTAWS may have provided altitude callouts giving the pilot a clue that the aircraft was descending.The HTAWS may have provided a “SINK RATE” or “PULL UP” alert.
Point D is the point of impact. The airworthy aircraft was flown into the water by a qualified pilot with inadequate awareness on the part of the pilot of the impending collision. This is the definition of CFIT.
The CFIT case that we have just reviewed did not have to happen. Had the aircraft been equipped with an HTAWS, the outcome may have been much different – we would probably be reviewing a different accident scenario.HTAWS may have helped to prevent this accident in several ways:By providing the pilot with a terrain display.By providing the pilot with a display of nearby airports – this could prove to be beneficial because it might give the pilot an expectation of where he might encounter increased air traffic due to arrivals/departures.By providing a display of nearby obstacles (including transmission lines in some models).By providing a display of nearby traffic.By providing an altitude awareness using callouts and a MINS annunciation/callout.
NAG – not your wifeCertification: Airframe specific STC, ACO assisted field approval, complex AML STC (Gap Analysis)Liability - loss of life, availability of equipment & man power to perform installations as end of mandate nearsDisplay Mode: Relative & TOPOHover display – heading input
In Apr 2, 2012, FAA released draft guidance outlining the technical requirements for a widely expected mandate that will require the installation of terrain awareness and warning systems (TAWS) on all helicopter EMS (HEMS) aircraft.Accordingly, the release of draft AC 27-1B and AC 29-2C is a clear signal that the final ruling could be released by the end of this year. The final hurdles are reviews by both the US Dept of Transportation and Office of Management & Budget—steps that typically result in delays of up to 12 months.The draft documents state that a helicopter TAWS (HTAWS) is required for helicopter air ambulance operations under 14 CFR Part 135 (Subpart L–CFR 135.605). Compliance is assured by employing systems that meet or exceed the minimum standards set forth in the existing FAA TSO C194 and RTCA DO309 documents. First published in Dec 2008, TSO C194 is the helicopter equivalent and more general version of fixed-wing TSO C151b. RTCA DO309 outlines minimum operational performance standards (MOPS) for HTAWS.Once the rule is finalized, nearly 1000 HEMS aircraft will be required to be TAWS-equipped within 3 years. FAA documents indicate that 41% of the current HEMS fleet has TAWS equipment. Retrofitting aircraft with TSO-compliant HTAWS equipment costs anywhere from $19,000 to $55,000 per aircraft—not including installation and down time—depending on the system selected.
Breaking the Accident Chain: HTAWS
Breaking the Accident Chain IHST Safety Workshop March 4, 2013
Agenda• Breaking the Accident Chain Overview – FAA Case Scenario• HTAWS Truths and Myths• HTAWS – What you need to know• Mandate Update
Breaking the Accident ChainNTSB Accident Number: NYC05MA039
Breaking the Accident ChainMission: HEMS repositioning flightDeparture point: Washington HospitalCenter Helipad (DC08) – Washington DCDestination: Stafford Regional Airport (RMN)Stafford, VAFlight distance: 38 NM
Breaking the Accident ChainWeather at the accident site (DCAAutomated Weather Observation):Winds calm, Visibility 10NM, Broken cloudsat 13,000’ and 20,000’, Temperature 45° F,Dew point 36° F, Altimeter 30.25**************************************************Moon Illumination: None
Breaking the Accident ChainPilot Information: Commercial Pilot – ASEL,AMEL, Rotorcraft Helicopter, InstrumentHelicopterMedical: Current, Second ClassPilot Experience: 1500 hours total time42 hours in the last 90 days12 hours in the last 30 days1 hour in the last 24 hours71 night landings total
Breaking the Accident ChainAircraft: Eurocopter EC-135 P2AFTT: 166.6 HoursMaintained IAW FAA approved aircraftinspection program.This aircraft was being flown with a properlydeferred inoperative radar altimeter.
Breaking the Accident ChainDeparted DC08@ 2304FollowedHelicopter Route1 along theAnacostia Riverto HelicopterRoute 4 and thenflew south alongthe PotomacRiver.
Breaking the Accident ChainPOINT A“Washington tower traffic on a ten milefinal is an Airbus”
Breaking the Accident Chain HTAWS with Traffic Display
Breaking the Accident ChainPOINT B“Roger, we have him in sight and will beout of his way”
Breaking the Accident ChainPOINT C FATAL DESCENT
Breaking the Accident Chain Benefits of HTAWSIncrease Situational Awareness by:• Provides a display showing surrounding terrain, airports.• Provides a display of obstacles (not all HTAWS display transmission lines).• Provides a display of nearby traffic.• Provides altitude awareness through the use of altitude callouts and GPWS alerts.
Breaking the Accident ChainSummary:The best trained pilot can’t see everything.HTAWS contributes to situational awarenessby helping the pilot to avoid dangers he maynot see when he looks outside.
Issues and Options• Issues Options – Nuisance Alerts – – Wire Database Pilots turn the system off – 3 arc data vs. 6 arc data – Certification – what is required? – Radar Altimeter – Installation – Traffic Display – Safety vs. Budget – Display options – Liability in waiting – NVIS to comply
What to ask before you purchase• What companies/OEM are using the manufacture’s HTAWS and what have been the results?• How does the HTAWS system qualify for certification, technically?• What is the cost of waiting to install – Liability – Availability and time limits – Certification headache – waste time and money
FAA Mandate Update Milestone Originally New Actual Scheduled Projected Date Date DateTo OST 1/04/2012 4/03/2012 4/03/2012To OMB 2/06/2012 12/14/2012OMB 5/03/2012 3/15/2013ClearancePublication 5/21/2012 3/29/2013Date
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