Foggy Takeoff,  Part 2, Spatial Disorientation

NTSB accident reconstruction
Credit: NTSB

In Part 1, we discussed the circumstances surrounding the December 2019 crash of a Piper Cheyenne in foggy conditions at Lafayette, Louisiana.

The 51-year-old accident pilot reported 1,530 total flight hours on his most recent medical exam, which took place six weeks before the accident. His most recent logbook was not found, but the NTSB determined that he had about 730 hr. in the Cheyenne. He had a commercial multiengine certificate with private privileges for single-engine land and a second-class medical certificate.

The pilot received his initial private pilot certificate in 2001. His first two attempts to obtain his instrument rating were disapproved before he earned it in 2004. He also made two attempts to complete his commercial certificate in 2005. The instructor who signed off his initial private pilot certificate was the same instructor who had been conducting most of his recurrent training in the Cheyenne.

The Cheyenne was owned by the founder and chairman of Global Data Systems (GDS), who, according to the instructor, was formerly a professional pilot. The aircraft owner, the accident pilot and the instructor had all known each other for a long time.

The flight instructor told the NTSB that he had flown for GDS from 2000 to 2008 and that the accident pilot had been a crew chief for the airplanes at that time. When that pilot took over flying the Cheyenne, he and the owner would fly to Houston, and both would participate in recurrent ground and flight training with the instructor.

The accident pilot’s most recent training in the Cheyenne was on April 22, 2019, eight months before the accident. On the ground, they reviewed flight manuals, systems, departure procedures, ground checks, hot and hung starts, and an stability augmentation system (SAS) test. In flight, they did a stall series, steep turns and a single-engine go-around at altitude. They finished by conducting ILS and VOR approaches.

The instructor said they did not do “hood” or simulated instrument flight. He was aware that Lafayette had “a lot of extreme fog” during the season beginning in October and he said he had flown approaches to minimums with the accident pilot.

The surviving passenger was interviewed about six weeks after the accident. He recalled that the takeoff felt normal, but he had a harder sense of pitching up in the climb than normal, and it felt like the airplane was climbing right up to the point where the impact sequence began.

The passenger’s statement was consistent with the performance analysis, which showed that the airplane’s normal load factor steadily increased as the bank angle exceeded 40 deg., going from 1.0 Gs to 3.2 Gs just before the end of the flight.

The performance study also showed that over the 42-sec. period that the airplane was in a left bank, the roll rate remained at or very near 2 deg. per second. That rate is the threshold for human perception of roll. Without looking at the attitude indicator or the other flight instruments, the pilot would have been unable to tell the airplane was rolling.

Conclusions and Comments
The Safety Board decided the probable cause of the accident was “the pilot’s loss of control due to spatial disorientation during the initial climb in instrument meteorological conditions.”

They arrived at this conclusion by methodically examining and eliminating the other possible causes of the accident, one by one. They did not go into much detail explaining spatial disorientation or why the pilot might have experienced it.

There are many good explanations of spatial disorientation, including one in Chapter 3 of the FAA’s Instrument Flying Handbook. There is more than one type of spatial disorientation. The Aircraft Owners and Pilots Association has an excellent description of “the graveyard spiral” in its “SA17—Spatial Disorientation” bulletin.

According to the bulletin: “This is a high-speed, tight descending turn (not a spin, because the wing never stalls) entered as a result of a failure to detect rolling motion. Since any bank rate of less than 2 deg. per second is not felt, the wing may drop, and the plane may begin a turn without the pilot realizing it. As the plane spirals downward and its descent accelerates, the pilot senses the descent but not the turn. The natural tendency is for the pilot to pull back on the yoke to arrest the altitude loss. But with the bank angle having gradually increased, this control input only tightens the turn and increases the descent rate.”

This describes the Cheyenne accident to a T. As the pilot keyed the mike to transmit, then switch frequencies and transmit again, he took his eyes off the attitude indicator. He didn’t recheck his attitude for 42 sec. because his instrument crosscheck was weak.

There was no evidence that the pilot had ever taken an instrument proficiency check since getting his instrument ratings in 2004. He had not flown in a flight simulator where he could practice low-visibility takeoffs and landings. His flight reviews were almost always conducted by the same personal acquaintance.

There was nothing wrong with his training as long as he adhered to suitable takeoff and landing minimums. I spoke with a flight instructor who conducts initial and recurrent training for pilot owners of high-performance piston and turboprop airplanes. I asked him what minimums he recommends for his clients, and he said 500 and 1.

This instructor adheres to these minimums himself, even though he’s a retired airline pilot. He flies single pilot, and he doesn’t get the rigorous training and high level of currency he got when he was flying an Airbus.

He went on to say that a 500-ft. ceiling gives a pilot time to retract the gear and flaps before entering the overcast, where he needs to settle into flying the gauges. A 500-ft. ceiling on approach gives the pilot time to break out, find the runway, and align himself with the centerline without excessive banking.

I queried the NTSB database to find all cases where the analysis included the phrase “spatial disorientation.” There were 287 such events—266 were on FAR Part 91 flights and 256 of those had fatalities. If you pull up any of these cases and read the reports, you will see the same pattern over and over. GA pilots fly into low-visibility conditions they can’t handle and they die.

How can we avoid this carnage? The answer is simple but unpalatable for many. Maintain high but safe personal minimums or get rigorous initial and recurrent training in low-visibility instrument flight.

Foggy Takeoff, Part 1 Cheyenne Loss of Control,…

Roger Cox

A former military, corporate and airline pilot, Roger Cox was also a senior investigator at the NTSB. He writes about aviation safety issues.