Wednesday, October 25, 2017

Night Disorientation in a Caravan

By Armand Vilches
Only days out of training a young pilot was seduced by the black hole syndrome that has claimed too many unwary flyers.
The enthusiasm and awareness that often accompanies a new job can be an exhilarating experience. There were, no doubt, many thoughts running through this pilot’s mind as he lifted off on the next leg of his flight into the black of night. But one thought should have taken precedence—fly the airplane.

Flying Freight

The commercial pilot held ratings for single- and multi-engine land airplane and instrument airplane. He also held a flight instructor certificate with the same privileges. A review of his logbook, after the accident, indicated a young, but experienced pilot, albeit he was light in make and model. His logbook listed 1921 hours of which 142 hours were at night and 47 hours were in actual instrument conditions. But he had only 34 hours in a Cessna 208B Caravan. As a rule of thumb, pilots are generally not considered experienced in an aircraft until they have accumulated at least 100 hours of make and model time.
The pilot joined the company a little over a month before the accident. He successfully completed his training and Part 135 check ride over the course of 10 days. A month after completing his training program, the pilot began an initial operating experience (IOE) period with a senior company captain by his side. This IOE training was completed in five days.
The pilot was then deemed proficient to fly under IFR and he began flying solo until the accident flight just three days later.

The Environment

Although the equipment, by some standards, has improved over what was available in the old piston-powered twin-engine aircraft freight-dog days, feeding the larger city hubs is still predominantly conducted single-pilot, at night, and from rural airports in poorly lit areas of the country. There is a lot of pressure to complete each flight quickly and efficiently. Keeping contracts with the major freight companies is a priority in this highly competitive business.
Three witnesses who spoke with the pilot when he arrived at Pellston Regional Airport (KPLN), in Pellston, Michigan, all said the pilot appeared alert and awake. The pilot wanted 30 gallons of fuel and needed to make a “quick turn.”
It was night and the weather was VFR. The automated report an hour before the accident indicated winds out of the southwest a 10 knots gusting to 16 knots. Visibility was 10 miles and the ceiling was reported as broken at 3600 feet and 4800 feet respectively, and then overcast at 5500 feet.
Another pilot who was also flying a Cessna Caravan, for a competing freight company, began taxing out from the ramp. He noticed and waved to the accident pilot. This pilot noted nothing unusual about the accident Caravan or pilot. He did, however, comment on the weather conditions he encountered during his departure five or so minutes before the accident flight.
A Cessna Caravan launches at night

This pilot described the flight conditions as bumpy. He also noted that when the wind is out of the southwest, as it was that evening, it is usually a turbulent departure to about 1000 feet AGL. This pilot further emphasized that he would not characterize it as being wind shear conditions, just bumpy.
During his interview with the NTSB this pilot also described Runway 23 departures at night as being black hole departures, and he routinely was on the gauges during climb-outs from this particular runway.  The pilot also commented that conditions were VFR all the way to 6000 feet that evening. While this pilot didn’t comment on the ground lights, conditions had to be dark over the sparsely lit northern Lower Michigan terrain.

Vestibular Illusions

Once the cargo was loaded, the accident pilot started the Caravan and began to taxi to Runway 23. The pilot would be departing IFR for a flight to Lansing, Michigan. Nothing unusual was noted by the ramp personnel, who went back inside the FBO as the aircraft rolled away.
Inside the aircraft the pilot had a Garmin 696 handheld GPS. These units have memory chips from which considerable flight information can be gleaned by investigators, but only if the unit is not too severally damaged by the accident. Essentially, some of the modern electronics in general aviation are beginning to act as de facto flight recorders.
In this case the data was recoverable, and a study of the data allowed the NTSB to create an extensive flight simulation model.
The first significant GPS point has the Caravan climbing at 700 feet-per-minute and accelerating to 91 knots through 14 feet AGL. This was on a heading of 223 degrees. The aircraft continued climbing at a rate of 500 to 700 feet per minute to an altitude of 240 feet above the ground while also continuing its acceleration. Then the rate of climb begins to slow as the aircraft reaches 260 feet AGL. At this point the aircraft starts a descent that continues until it impacts wooded terrain a mile away.
Moreover, shortly after liftoff, the Caravan entered a right turn with a bank angle of up to 12 degrees. This bank caused the aircraft to turn 42 degrees right of runway centerline. During this bank the aircraft was also in a nose down pitch attitude of at least two degrees. Based on the GPS information, the NTSB estimated the elapsed time from take-off to impact to be 54 seconds.

The inner ear is the source of our balance. The somatogravic illusion causes the inner ear to tell us that when an aircraft is accelerating it is pitched up and climbing even if it is descending.

The study went further. It investigated the load factor vectors, which would have been present, and then compared this information to the human vestibular system. This allowed the investigators to estimate the apparent sensations of motion being experienced by the pilot. Based on the study, the pilot would not have felt any roll, and he would have believed his pitch angle was always greater than zero. In other words the pilot would have sensed he was holding heading and climbing out straight ahead.
It’s almost certain the pilot succumbed to somatogravic illusion even while the aircraft was descending. This illusion creates a sensation of climb in the vestibular system, when a smooth and rapid acceleration is sensed by the body. A great way to personally experience the sensation is to close your eyes and keep your head motionless the next time you are seated in the back of an airliner waiting for it to begin its take-off roll. As the aircraft accelerates down the runway your vestibular system will indicate a pitch-up sensation well before the aircraft starts to rotate.
Based on the above, it is difficult to disagree with the NTSB’s probable finding: “The pilot’s inadvertent controlled descent into terrain due to spatial disorientation. Contributing to the accident was lack of visual reference due to night conditions.”

Trust Your Instruments

Trusting our instruments is an old aviation adage, but it needs to be followed while we perform hawk-like instrument scans in IMC. This pilot wasn’t a neophyte to flight, even with his low make and model time, and a Cessna Caravan is not overly difficult to fly, so what happened? Perhaps the pilot relaxed his instrument scan because the conditions were being reported as VFR, or perhaps he was distracted from concentrating on the task at hand by his need to quickly depart in order to make the next leg.
Any pilot can be affected by spatial disorientation, regardless of his or her experience level, even when the flying is in an airline crew environment.
Unfortunately, spatial disorientation accidents repeat themselves with regularity in the NTSB reports. A quick and unscientific review of NTSB records, during a recent five year period, listed spatial disorientation as a probable cause in more than 100 accidents. Even more depressing is the fact that over 90-percent of these accidents had a fatality.
These fatality rates are worse than what would be expected when playing Russian roulette with five loaded chambers in a six-round revolver.

Checkpilot Recriminations

The thoughts that may have consumed the company pilot who performed the pilot’s checkride might also be considered. Most certainly he covered all of the pertinent maneuvers and procedures required of the new pilot to demonstrate competency. But how do you evaluate a person’s potential mind-set that prevailed that fateful night.

Your instruments are your friends during climbout following a night takeoff.

No doubt this senior captain may add an awareness factor to subsequent reviews of new pilots and their understanding of the black hole syndrome and the need to maintain focus on the task at-hand.
Let’s do ourselves and others a favor by making a commitment to become and/or remain proficient on the gauges, and to never relax our scan during night VFR departures.

This article appeared on October 2017