ASN Wikibase Occurrence # 195094
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| Date: | Friday 28 April 2017 |
| Time: | 23:48 |
| Type: |  Pilatus PC-12/45 |
| Owner/operator: | Rico Aviation Llc |
| Registration: | N933DC |
| MSN: | 105 |
| Year of manufacture: | 1994 |
| Total airframe hrs: | 4407 hours |
| Engine model: | P&W Canada PT6A-67B |
| Fatalities: | Fatalities: 3 / Occupants: 3 |
| Aircraft damage: | Destroyed |
| Category: | Accident |
| Location: | 2 km S of Amarillo-Rick Husband International Airport, TX -
 United States of America
|
| Phase: | Initial climb |
| Nature: | Ambulance |
| Departure airport: | Amarillo, TX (AMA) |
| Clovis, NM (CVN) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The pilot and two medical crewmembers departed on an air ambulance flight in night instrument meteorological conditions to pick up a patient. After departure, the local air traffic controller observed the airplane's primary radar target with an incorrect transponder code in a right turn and climbing through 4,400 ft mean sea level (msl), which was 800 ft above ground level (agl). The controller instructed the pilot to reset the transponder to the correct code, and the airplane leveled off between 4,400 ft and 4,600 ft msl for about 30 seconds. The controller then confirmed that the airplane was being tracked on radar with the correct transponder code; the airplane resumed its climb at a rate of about 6,000 ft per minute (fpm) to 6,000 ft msl. The pilot changed frequencies as instructed, then contacted departure control and reported "with you at 6,000 [ft msl]" and the departure controller radar-identified the airplane. About 1 minute later, the departure controller advised the pilot that he was no longer receiving the airplane's transponder; the pilot did not respond, and there were no further recorded transmissions from the pilot. Radar data showed the airplane descending rapidly at a rate that reached 17,000 fpm. Surveillance video from a nearby truck stop recorded lights from the airplane descending at an angle of about 45° followed by an explosion.
The airplane impacted a pasture about 1.5 nautical miles south of the airport, and a postimpact fire ensued. All major components of the airplane were located within the debris field. Ground scars at the accident site and damage to the airplane indicated that the airplane was in a steep, nose-low and wings-level attitude at the time of impact. The airplane's steep descent and its impact attitude are consistent with a loss of control.
An airplane performance study based on radar data and simulations determined that, during the climb to 6,000 ft and about 37 seconds before impact, the airplane achieved a peak pitch angle of about 23°, after which the pitch angle decreased steadily to an estimated -42° at impact. As the pitch angle decreased, the roll angle increased steadily to the left, reaching an estimated -76° at impact. The performance study revealed that the airplane could fly the accident flight trajectory without experiencing an aerodynamic stall. The apparent pitch and roll angles, which represent the attitude a pilot would "feel" the airplane to be in based on his vestibular and kinesthetic perception of the components of the load factor vector in his own body coordinate system, were calculated. The apparent pitch angle ranged from 0° to 15° as the real pitch angle steadily decreased to -42°, and the apparent roll angle ranged from 0° to -4° as the real roll angle increased to -78°. This suggests that even when the airplane was in a steeply banked descent, conditions were present that could have produced a somatogravic illusion of level flight and resulted in spatial disorientation of the pilot.
Analysis of the performance study and the airplane's flight track revealed that the pilot executed several non-standard actions during the departure to include: excessive pitch and roll angles, rapid climb, unexpected level-offs, and non-standard ATC communications. In addition to the non-standard actions, the pilot's limited recent flight experience in night IFR conditions, and moderate turbulence would have been conducive to the onset of spatial disorientation. The pilot's failure to set the correct transponder code before departure, his non-standard departure maneuvering, and his apparent confusion regarding his altitude indicate a mental state not at peak acuity, further increasing the chances of spatial disorientation.
Probable Cause: The pilot's loss of airplane control due to spatial disorientation during the initial climb after takeoff in night instrument meteorological conditions and moderate turbulence.
Accident investigation:
 |
|
Sources:
NTSB
FAA register: http://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?NNumbertxt=933DC
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 29-Apr-2017 14:29 | gerard57 | Added |
| 29-Apr-2017 14:34 | harro | Updated [Location, Source] |
| 29-Apr-2017 14:36 | harro | Updated [Aircraft type, Registration, Cn, Source, Narrative] |
| 29-Apr-2017 15:31 | gerard57 | Updated [Date, Time] |
| 29-Apr-2017 16:13 | Aerossurance | Updated [Time, Phase, Source, Embed code, Narrative] |
| 29-Apr-2017 21:23 | wf | Updated [Operator, Embed code, Narrative] |
| 01-May-2017 06:45 | Iceman 29 | Updated [Embed code] |
| 01-May-2017 17:15 | Geno | Updated [Registration, Phase, Source, Embed code, Narrative] |
| 16-May-2017 16:10 | wf | Updated [Location, Phase, Departure airport, Source, Narrative] |
| 09-Aug-2018 19:27 | Aerossurance | Updated [Date, Time, Location, Destination airport, Source, Narrative] |
| 09-Sep-2018 17:26 | ASN Update Bot | Updated [Time, Operator, Departure airport, Destination airport, Source, Embed code, Narrative, Accident report, ] |
| 09-Sep-2018 17:59 | harro | Updated [Source, Embed code, Narrative] |
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