Loss of Control After Takeoff, Part 2

In Part 1, we discussed the circumstances surrounding the crash of a Pilatus PC-12 shortly after takeoff in Chamberlain, South Dakota.

An NTSB aircraft performance engineer did a study of the PC-12’s performance using the FDR report data, videos, the location of the crash site and simulation results to determine the flight’s trajectory. In addition to doing a computer-driven “desktop” simulation of the flight, the engineer, the IIC and an FAA PC-12 test pilot conducted an evaluation of the accident flight using a PC-12 Level D training simulator.

One of the objectives of these simulations was to see if differences between the desktop simulation and the LDR data were the result of snow and ice contamination. The desktop simulation predicted a higher rate of climb and maximum altitude than the airplane achieved, indicating icing might have been a factor. However, the model was slightly inaccurate.

The LDR recorded parameters from the airplane’s previous takeoff at Idaho Falls. There was no snow or ice contamination on the airplane during that takeoff. The performance of the accident flight closely matched the earlier flight, indicating that snow and ice did not significantly affect the accident takeoff.

Snow and ice that remained on the horizontal stabilizer may have affected elevator hinge moments and column control forces, but they did not change the aircraft’s performance.

Another objective of the simulations was to evaluate the airplane’s handling with its heavy weight and extreme aft CG.
Investigators who flew the flight simulator programmed with the accident weight and CG found it had even lower stability than the desktop simulation showed. Keeping the PC-12 tracking on centerline took concentration and it was difficult to keep the airplane from over-rotating into the stall region. Pitch oscillations were a common result during the trial runs.
Investigators also compared the rotation rates of the accident pilot with those of another pilot whose flight in N56KJ had been recorded. The second pilot’s rotation rates were around 3 deg. per second, and investigators found the flight simulator was much easier to control using that technique.

The LDR data showed that the accident pilot rotated the nose at 7 deg. per second on the accident takeoff, pitching the airplane up to 15.8 deg. He also rotated early, 4 kt. before the 92-kt. rotation speed that was appropriate for his configuration. The combination of early rotation, rapid rotation and aft CG drove the airplane to a high angle of attack, causing the stall warning, stick shaker and stick pusher to activate.

The graphical presentation of the airplane’s pitch and AOA oscillations in the performance report provides a classic example of the effects of attempting to control an airplane with an extreme aft CG.
The registered owner of the airplane was Conrad & Bischoff Inc., a distributor of fuel, lubricants and antifreeze located in Idaho Falls. The airplane was not maintained on a Part 135 certificate.

The 48-year-old accident pilot had a private pilot certificate and a Class 3 medical certificate. His last medical examination was about 10 months before the accident, and his last flight review was one year before the accident. He attended PC-12 recurrent training at Simcom in 2017 and at Bagley Aviation in 2018.

Investigators obtained his second logbook, which began in 2008, but 1,319 hr. from his first logbook were forwarded and no other record of his early experience was available. The logbook entries beginning in 2008 were quite detailed. Many of his flights were to and from major airports, but there were also many trips noted as “fishing” or “hunting.” Some mentioned customers or conventions.

In 2018, other than one entry for his flight review, there were no specific entries. Instead, he only made a summary entry of 37.7 hr. The log did not show any 2019 flying.

According to an insurance form he filed, the pilot had 2,300 total flight hours and 1,260 single-engine turboprop hours as of February 2019. The NTSB stated he had 10 hr. in the last 90 days and 2 hr. in the last 30 days before the accident, but that time was not documented in his logbook.

The pilot averaged about 100 hr. of flying per year over the last 15 years, but he only flew about 40 hr. in 2018 and probably only about 14 hr. in 2019 before the accident flight.

Conclusions and Comments

The NTSB’s probable cause of the accident was “The pilot’s loss of control shortly after takeoff, which resulted in an inadvertent, low-altitude aerodynamic stall. Contributing to the accident was the pilot’s improper loading of the airplane, which resulted in reduced static longitudinal stability, and his decision to depart into low instrument meteorological conditions.”

The airplane’s slightly excessive weight did not much impair its performance, but the aft CG certainly did. The two unrestrained passengers probably slid or rolled aft when the pilot pitched the airplane up so sharply on takeoff, exacerbating his pitch control problems.

It remains a mystery why the pilot developed the bad habit of doing rapid rotations. It’s something that should have been corrected during his recurrent training. As a private pilot, his periodic training was a flight review, not a check ride. His airplane handling skills were probably not scrutinized as carefully as they would have been if he had been a commercial pilot taking a Part 135 check ride.

A Beech King Air pilot made a similar mistake in 2019 on a parachute drop flight in Hawaii, pitching up and banking sharply immediately after takeoff. That airplane also stalled and crashed.

As a private pilot, the accident pilot was not allowed by FAA regulations to accept compensation for flying. If he was paid for flying, directly or indirectly, he should have had at least a commercial pilot certificate. There was also no evidence that he was instrument current in accordance with 14 CFR 61.57. Recent instrument currency would have been helpful when he attempted the takeoff into a 500-ft. overcast.

The pilot tried to address one safety threat by deicing the airplane, but he missed other threats, including too many passengers, aft-loading the airplane, and his own rusty skills. He didn’t fly enough to be a full-time professional pilot, but he was flying a sophisticated, high-performance airplane that required professional-level skills.

The accident report probably would have been released much earlier were it not for the lengthy examination of the airplane’s performance. Doing a performance analysis and setting up a flight simulator trial can consume many months.

Without the LDR and the performance analysis, the NTSB could very well have determined that the probable cause of this accident was icing. Instead, they were able to go beyond the obvious explanation to get at the underlying issues.

The NTSB has been calling for crash-resistant recorders on passenger-carrying aircraft for years. The fact that the recorder on this airplane survived shows that there is also a place in investigations for LDRs, even though they are not technically crash-resistant.