Under the influence

A direct correlation between an accident and the fact that the pilot had taken some medication is a difficult connection to make. Pilots make bad decisions all the time, with or without impairment, but where do mistakes end and impairment begin? But with one study showing 25 per cent of fatally injured pilots having an impairing substance in their system, it would appear that there are some real risks to consider.

Accident 1

Witnesses saw the aeroplane flying over a frozen lake at a low altitude and low airspeed. One witness saw the aeroplane ‘listing’ left and right before it entered a left turn, then the witness lost sight of it. Others saw the aeroplane turn left, nose dive into the ground, where it was consumed by a post-impact fire.

In fact, damage to the wreckage indicated that the aeroplane impacted the ground in a nose down attitude. The examination did not reveal evidence of any pre-impact anomalies with the airframe, engine or the control system of the aeroplane. A witness reported that at the time of the accident the wind was from the south about 30mph.

“Chlorpheniramine may slow psychomotor functioning and cause drowsiness”

However, a burnt area extending east from the aeroplane’s impact point indicated the wind was from the west.

Additionally, although wind information from nearby weather stations varied in direction and intensity, one station about 14 miles west-north-west of the accident site reported calm wind.

However, another station located about 11 miles south of the accident site, recorded wind from the west at 11kt with gusts to 27kt about the time of the accident, and wind from the west at 33kt with gusts to 48kt about an hour after the accident.

Further, the forecast for the accident area called for wind gusts to 40kt from the west-north-west. Therefore, it is likely that strong gusty west winds prevailed in the accident area at the time of the accident.

Although some witnesses speculated that the pilot may have been trying to land the aeroplane on the frozen lake, the aircraft was not equipped to land on ice, and the reason as to why the pilot was manoeuvring at a low altitude in strong gusty winds could not be determined.

Based on the witness observations and the damage to the wreckage, it is likely that the pilot allowed the airspeed to decrease to a point where the critical angle of attack was exceeded, and the aeroplane entered an aerodynamic stall/spin.

Although the pilot was known to have heart disease, it is unlikely that his medical condition contributed to the accident. The witness observations indicate that the pilot was actively flying the aeroplane before the loss of control.

Toxicology testing showed the presence of chlorpheniramine in the pilot’s blood at a level that was likely in the therapeutic range. Chlorpheniramine is a sedating antihistamine available in a number of products that can be bought over the counter. As such it comes with the warning: ‘May impair mental and/or physical ability required for the performance of potentially hazardous tasks (e.g., driving, operating heavy machinery)’. Because of its sedating effect, chlorpheniramine may slow psychomotor functioning and cause drowsiness. It has also been shown in a driving simulator (after a single dose) to suppress visual-spatial cognition and visual-motor coordinating functions when compared to a placebo. Such functions would have been necessary for the pilot to maintain control of the aircraft while he was manoeuvring close to the ground in the strong gusty wind conditions.

Therefore, it’s likely the pilot’s ability to safely operate the aircraft was impaired by the chlorpheniramine effects.

Accident 2

A Cessna 177B was substantially damaged when it impacted the ground following the pilot’s loss of aeroplane control during climb out from an aborted landing at Cherry Ridge Airport (N30), Honesdale, Pennsylvania. The certificated private pilot was fatally injured.

Several witnesses stated that the aircraft completed three traffic pattern approaches to the 2,986ft-long, 50ft-wide Runway 18. Two of the witnesses, a student pilot and a flight instructor, had just finished traffic pattern work to Runway 36, and all of the witnesses who observed the windsock about the time of the accident stated that it indicated winds from the north or north-west. The flight instructor estimated wind velocity to be about 10kt, and another witness stated that the windsock was mostly ‘straight out’.

The witnesses also noted that the aeroplane completed the first two traffic pattern approaches to low approaches that resulted in go-arounds. During the second go-around, the flight instructor saw that when the aeroplane was about 200ft above the runway, it was climbing at an ‘unusually high’ angle of attack.

The flight instructor further stated that as the aeroplane approached the runway a third time, it appeared to be ‘unusually fast’. It commenced a landing flare past the runway identification numbers, and ‘floated a long way’ until it ‘forcefully’ touched down nosewheel first, then porpoised several times. Just past the windsock, engine power was applied and the aeroplane’s nose pitched up in excess of 20°. The aeroplane subsequently stalled and began a spin to the left, completing a 180° rotation before hitting the ground with no adjustments to engine power.

Another witness noted that during the accident sequence, the nose of the aeroplane pitched up about 45° or greater until it reached an altitude of 200 to 300ft above the runway. It then appeared that the left wing stalled, and the aeroplane turned to the north-east, descending to the ground with power on.

An autopsy was performed on the pilot with the cause of death noted as ‘multiple traumatic injuries secondary to (an) aeroplane accident’. Toxicological testing was subsequently performed by the FAA Forensic Toxicology Research Team, Oklahoma. Anomalies noted included: Diphenhydramine detected in liver. 0.353 (ug/ml, ug/g) Diphenhydramine detected in blood.

The FAA Civil Aeronautical Medical Institute website reports that diphenhydramine ‘is a common, over-the-counter antihistamine used in the treatment of the common cold and hay fever. It carries the warning: May impair mental and/or physical ability required for the performance of potentially hazardous tasks (e.g., driving, operating heavy machinery)’.

According to the National Highway Transportation Safety Administration Drugs and Human Performance Facts Sheet, laboratory studies indicate that diphenhydramine can: ‘Decrease alertness, decrease reaction time, induce somnolence, impair concentration, impair time estimation, impair tracking, decrease learning ability, and impair attention and memory within the first 2-3 hours post dose. Significant adverse effects on vigilance, divided attention, working memory, and psychomotor performance have been demonstrated. It is important to note that impairment has been shown to occur even in the absence of self-reported sleepiness or sedation’.

Accident 3

The instrument rated airline transport pilot was manoeuvring the aeroplane from about 14,500ft msl while descending to the destination airport.

“Use of diphenhydramine likely contributed to the accident by degrading the pilot’s judgement”

Throughout the flight, the pilot was texting his son asking about the weather conditions at the destination airport, which was near to where his son was located. The son described a broken cloud layer and advised that if the aeroplane stayed above the clouds it could then ‘drop in over the valley’. About two minutes before the accident, the pilot told an air traffic controller that he was, ‘going to orbit here to the south… south over the airport I can see it, manoeuvring through a hole’. GPS data showed that as the aircraft continued to turn to the right, its airspeed increased rapidly, and the right turn tightened.

After completing a full revolution, the aeroplane exceeded its maximum structural cruising speed and never-exceed speed. The aeroplane’s flight load increased throughout the turn, exceeding the aeroplane’s maximum flight load factor. Immediately afterward, the flight data became unreliable, this point was likely when an inflight break-up occurred.

The location of the separated components in the debris field and the damage to them were consistent with a tail-first, inflight break-up. The aeroplane flight path before the inflight break-up was consistent with a graveyard spiral caused by spatial disorientation. The pilot’s statement to the controller regarding his intent to ‘manoeuvre through a hole in the cloud layer’ indicated operation near instrument meteorological conditions (IMC). The aeroplane’s excessive bank, pitch and load factor coincided with the height of the reported cloud tops (13,000ft). This further indicates that the pilot was likely flying in and out of the clouds as he was attempting to spiral down to the airport. Given the reports of ceilings at 9,500ft, the inflight break-up probably occurred in IMC or within seconds of the aeroplane exiting IMC, precluding the pilot from taking recovery action upon re-entering visual meteorological conditions.

The investigation could not determine whether the pilot was using supplemental oxygen while operating the aeroplane above 14,000ft msl, as required by federal regulations. However, the comms between the controller and the pilot revealed that the pilot had no appreciable change in speech rate, coherence, or response time, indicating that the pilot was not experiencing hypoxia while in contact with air traffic control.

Although the pilot’s coronary artery disease placed him at an increased risk for a sudden cardiac event, no evidence indicated that such an event occurred.

Toxicology testing identified diphenhydramine in the pilot’s cavity blood and liver specimens.

Because experienced instrument rated pilots should be able to identify spatial disorientation, the pilot’s use of diphenhydramine likely contributed to this accident by degrading the pilot’s judgement and slowing his responses.