N236KMPiper PA-46-310P · 1984

On September 20, 2020, about 1050 central daylight time (CDT), a Piper PA-46-310, N236KM, was substantially damaged when it was involved in an accident near Hilltop Lakes, Texas. The commercial pilot and three passengers sustained fatal injuries. The airplane was operated as a Title 14 Code of Federal Regulations (CFR) Part 91 personal flight.

While in cruise flight at 19,000 ft mean sea level (msl), the pilot declared an emergency to air traffic control (ATC) and stated that the airplane had lost engine power and that he needed to divert. The pilot elected to divert to Hilltop Lakes Airport (0TE4), which was about 5 miles south of his position. Archived Federal Aviation Administration (FAA) automatic dependent surveillance-broadcast (ADS-B) data revealed that when the airplane was about 5 miles west of 0TE4, a descent was initiated from 19,000 ft, and the airplane proceeded directly to and circled the airport one time while descending. ADS-B data was lost about 3 miles northeast of the airport, as the airplane descended below the floor of the ADS-B reception capability.

Commercially available flight track data, which aggregates and geo-references FAA data sources, continued to receive aircraft data as the airplane turned to a final approach segment. The last data point showed the airplane about 1 mile north of the approach end of runway 15 at 0TE4 at an altitude of 1,250 ft, 169 knots groundspeed and on a ground track of 145°. From the cruise altitude of 19,000 ft until the last data point, about 12 minutes and 45 seconds had elapsed, which equated to an average descent rate of about 1,392 ft per minute.

Witnesses located about 1/4 mile south of the end of runway 15 reported seeing what they described as the airplane taking off, before noticing the propeller was not turning. They stated they saw the airplane in a left bank just prior to the nose dropping and the airplane impacting the ground in a near vertical attitude.

The following is a sampling of the winds aloft reported near 0TE4 about 9 minutes after the accident.

Height (ft-MSL)

DD/FF (deg/kts)

1,306

037/15

2,458

051/19

4,861

062/20

7,046

059/21

The airplane came to rest along a road about 200 ft south of the airport property. The airplane impacted the terrain in a nose low, near vertical attitude and sustained substantial damage to fuselage and both wings. A strong odor, consistent with jet fuel, was noted on scene and the left-wing fuel tank was breached.

The cockpit area exhibited extensive aft crushing and tearing around the circumference which resulted in the fuselage being separated. Flight control cable continuity was confirmed from the cockpit controls to the respective control surfaces, with the exception of separations consistent with wreckage recovery cuts and separations consistent with impact forces. The flap actuator rod was found extended about 6”, which is consistent with the flaps being fully extended at the time of the accident.

When moving the right wing during a post-recovery examination, liquid consistent with Jet-A fuel was observed pouring from the vapor return line at the wing root and from the leading edge near the inboard end of the fuel tank.

The engine exhibited severe impact damage and deformation. The center firewall was deformed around the engine and multiple airframe components including: the starter, alternator, air conditioning compressor, wiring, and parts of the mount structure remained attached to the engine. There was no evidence of uncontained engine failure or undercowl fire. The fuel control unit (FCU) and turboprop governor lines were intact. The Py line fittings at the turboprop governor, were secure on both sides of the center firewall but could be backed off without a wrench. The P3 line to FCU fitting was also finger tight. There was no debris accumulation on the engine magnetic chip detector plug or in the fuel or oil filters. There was residual fuel remaining in the fuel filter bowl and a small amount of shiny particulate was visible in the fuel when viewed under light

The accident airplane was equipped with a Shadin Avionics engine trend monitor (ETM), P/N 943200-11, S/N 0200. The ETM was recovered from the wreckage and shipped to the National Transportation Safety Board (NTSB) Recorders Laboratory in Washington, DC for evaluation and download. Recovered data captured the accident flight. Additionally, the unit was programmed to record select engine events including start, engine operating limit exceedances, and power checks. The following were the logged events from the accident flight:

09:36:44

Logon message is consistent with power being cycled on. Pressure Altitude at airport: 970 ft.

09:52:51

09:54:21

Start Max ITT: 732°C, Ng light-off speed: 20.3%, Start Time- 13 seconds. Start cycle was logged but there was no run time before engine off was recorded.

09:57:02

ETM recorded Low Bus Voltage: 327.68V. According to Shadin, 327.68V is recorded when the expected sequence of engine parameters is not met.

10:01:03

Low Bus Voltage: 327.68V

10:02:20

Low Bus Voltage: 327.68V. There was no associated “engine off log” timestamp after start attempt #4 consistent with a successful engine start where the expected sequence of engine parameters was not met. The ETM did not record engine start parameters.

10:03:11

Level 1 Torque Exceedance- 1,460 ft-lb for a duration of 1 second.

10:03:20

10:05:36

Level 1 Torque Exceedance- 1424 ft-lb for a duration of 4 seconds.

10:24:11

Pressure Altitude: 19,090 ft, Indicated Airspeed- 171 kts., Np- 2,141RPM, Torque- 880 ft-lb.,

Fuel Flow-36.1 GPH, ITT- 704°C, Ng- 94.2%

10:38:16

Pressure Altitude: 19,100 ft, Indicated Airspeed- 171 kts., Np- 2,155 RPM, Torque- 866 ft-lb.,

Fuel Flow-35.5 GPH, ITT- 701°C, Ng- 94.2%

10:41:48

Engine off is logged when Ng drops below 48%.

10:51:40

Logon message is consistent with power being cycled on. There was not a subsequent engine start attempt. Pressure Altitude- 3,540 ft.

Checklist Usage

The JetProp LLC AFM supplement for emergency procedures related to engine power loss in flight superseded the original procedures since there was a change in engine type. The first item on the Engine Failure (Mechanical Failure) checklist said to trim for 90 knots indicated airspeed (KIAS). The groundspeed of the airplane, as reported by track data, showed the ground speed varied between 122 knots (KTS) and 172 kts.

The first item on the Power Off Landing checklist said to establish best gliding angle and 90KIAS. Two notes were included in this procedure with the first instructing the pilot to “establish spiral pattern to arrive at 1,500 ft above field at downwind position for normal approach.” The second stated “when assured of reaching the field, use flaps as necessary and slow to 77 KIAS with flaps fully extended for shortest landing. When the airplane was on a downwind leg, the reported altitude was about 5,000 ft above ground level.