Working at the limits of your mental capacity can test a pilot’s ability, particularly when there’s added stress from a problem. FLYER’s new Flight Safety Editor Steve Ayres looks at a couple of accidents where two very different pilots had their capacity stretched…
Steve Ayres
7 July 2020
Having spent much of my early instructional career training hard to expand the mental capacity of students, it came as a bit of a blow later in life to be told that our mental capacity is pretty much fixed at birth, and no amount of training will expand it.
That said, of course, what training does is free up some mental space to be able to deal with those curveballs life throws at us. The following are two examples where the pilots involved were working at the limits of their mental capacity, testing their knowledge and experience with differing degrees of success.
The pilot reported that just after take-off, around midnight at Merredin Airfield in Australia, as the aircraft was climbing through 1,400ft agl at 140kt, the following occurred without any apparent precursors:
The pilot recalled hearing and seeing those warnings, and that the aircraft pitched nose-down violently shortly afterwards. With both hands pulling on the control column to raise the nose, the pilot found that the force required to move the control column was extremely high and required maximum effort. The pilot was unable to counteract the nose-down force and the aircraft developed a high rate of descent at approximately 2,000ft/min. In response to the warnings, the pilot initiated the pitch trim runaway emergency procedure from memory.
“ The pilot needed help from a passenger to overpower the force on the elevator”
The pilot recalled:
Following those actions the pilot was concerned that there was no change to the condition of the aircraft, which was contrary to his expectations from training. According to the recorded data, the pitch trim continued to operate in the runaway condition until it reached full nose-down position 16 seconds after the warnings were issued, during which the following data was recorded:
Over the next six seconds the situation continued to deteriorate until the pilot reduced engine torque when he noted control forces eased somewhat. At about that point, the airspeed had reached 210kt and the height was down to 1,100ft.
Nonetheless, after a further sequence of climbs and descents, he decided it was not possible to overpower the elevator force alone and requested the assistance of a passenger. The passenger pulled on the right control column, which had a positive effect on the variation of pitch attitude, associated airspeed and altitude parameters, although full control was not established.
As the aircraft was now in the Merredin circuit area, the pilot concentrated on preparation for landing.
When the flaps were selected to 15°, the pilot noticed the ‘flap’ caution on the crew alerting system (CAS), and realised the flaps were not available.
On the downwind circuit leg for Runway 28 the pilot extended the landing gear. This was followed by a rapid descent to 350ft agl with a ground proximity warning system (GPWS) alert. In response, the pilot (with the passenger’s continuing assistance) pulled on the control column to raise the nose, and increased engine torque. Height was recovered to a maximum of 900ft.
The pilot turned onto the base circuit leg and allowed the aircraft to descend. As the pilot turned onto the final approach, the aircraft overshot the runway centreline and required adjustment. On short final, the aircraft was high and the pilot was coordinating with the doctor to adjust the pitch attitude for landing. At one point, the pitch attitude was too high and activated the aural stall warning.
At about 30ft above the runway, the pilot asked the passenger to let go of the control column and reduced engine torque to idle. The aircraft touched down firmly at 1715. The pilot applied full reverse thrust and normal braking to bring the aircraft to a stop about 200m from the end of the runway. He taxied the aircraft to the parking area and shut down.
The pilot initiated the applicable emergency procedure, but inadvertently selected the flap interrupt switch rather than the trim interrupt switch.
Consequently (before the next checklist item was actioned), the pitch trim continued to runaway until it reached full nose-down with associated serious control difficulties. The pilot did not identify the mis-selection and continued to address the emergency procedure without resolving the full out-of-trim condition.
With the assistance of the passenger, the pilot managed to return to Merredin for a flapless landing. The aircraft was undamaged and the occupants uninjured.
The ATSB found that the pitch trim runaway occurred because of a malfunctioning relay in the manual (main pilot-engaged) stabiliser trim system.
As the (uninterrupted) pitch trim runaway progressed, the reinforcing cycle of increasing control loads, forced descent and increasing airspeed was initially exacerbated by high engine torque. The airspeed reached 210kt with increased risk of descent into terrain before the pilot reduced engine torque and airspeed to partially alleviate the control loads and arrest the descent.
After the pilot addressed items (2) and (3) of the emergency procedure, the malfunction was neutralised and the alternate stabiliser trim system was available to adjust the trim. However, the pilot did not identify those positive conditions and continued with items (4) to (8) of the procedure, which disabled the alternate stabiliser trim system, prevented pitch trim adjustment and prolonged the serious control difficulties.
The similarities between the trim interrupt and flap interrupt switches and the proximal location of the two switches, unnecessarily increased the risk of mis-selection and contributed to the excessive out-of-trim condition.
After first flying a circuit dual the student departed for three supervised solo circuits.
Following full-stop landings from the first two circuits a final approach was made from which the aircraft bounced before rolling along the runway.
“A contributing factor could have been the fatigue mentioned by the pilot”
Estimating that he no longer had sufficient runway remaining, the pilot applied full power for the go-around. The aircraft deviated left from the centreline and struck a tree on the edge of the airfield as it began to climb, rolled left and ended on its back in a field.
The student pilot had accumulated about 94 hours of flight time on dual control aircraft in the previous five years, which included a 10-minute supervised first solo flight with a full-stop landing a month earlier. In the month before the accident, he flew 2 hours 15 minutes dual.
The student had flown some 40 sorties with the same instructor in the 12 months before the accident.
The length of the sorties was on average less than 30 minutes and consisted of some 40 landings, most of which were full-stop.
The student pilot reported that the approach to the last landing was stabilised but that he bounced on landing. When on the ground, he felt he did not have enough runway ahead of him and decided to get airborne again.
According to aeromodellers close to the upwind threshold who saw the aircraft pass a few metres from the ground at the upwind end of the runway, the engine was not delivering all its power.
The instructor added that full-stop landings were generally made on dual sorties because the runway is short.
The pilot indicated that his concentration may have been dulled after the three solo circuits.
French BEA conclusions On his last landing, after a bounce, the pilot estimated that he would not be able to stop the aircraft before the end of the runway and decided to abort the landing.
He took off with the flaps in the landing configuration and carb heat applied, thus degrading the climb performance. The climb gradient did not allow the aircraft to clear obstacles around the aerodrome and uncontrolled engine effects caused the aircraft to turn left with a high incidence.
A contributing factor could have been the fatigue mentioned by the pilot, plus there appeared to have been insufficient understanding of the technique required on the go-around from an aborted landing.
These two accidents involved aircrew at opposite ends of the experience spectrum. One on his first solo circuit consolidation sortie, and one with a CPL and more than 2,000 hours of flight time. However, in both instances they were confronted with situations for which they were insufficiently prepared to cope effectively.
In both cases, the pilots would have been working to the limit of their capacity, and at times beyond, in highly dynamic and rapidly evolving situations. Sometimes there are limitations in our training which create these extreme situations from what should be relatively benign situations, sometimes we just don’t have the skill set to cope.
In the first instance the sequence of events must have been terrifying for all those on board, especially as it was in the middle of the night. However, what should have been a perfectly controllable situation following a relatively minor failure, a mis-selection had near fatal consequences. Being located next to each other and appearing similar in design, the pilot selected the flap interrupt rather than the trim interrupt. Struggling to control the aircraft in the darkness with seemingly nothing working ‘as advertised’, a proper analysis was always going to be difficult. Thankfully the aircraft was landed safely, however, without the passenger’s physical assistance the outcome would probably have been very different.
With many modern GA types from homebuilts upwards being equipped with electric trim, it’s worth having a trim runaway drill committed to memory. A well-rehearsed drill should include being able to identify and pull the associated CB or switch – in the dark if required. If trim and flap interrupt switches are fitted, are they mounted close together and do they look similar? If so, perhaps your drill should be to operate both in the heat of the moment and then ‘un-interrupt’ one of them once you have your heart rate and the aircraft back under control. Airspeed as well as thrust can be critical in many trim/flap failures, so setting a ‘ball park’ figure early on should ease some of those troublesome stick forces.
In the second instance the pilot was again in unfamiliar territory. It would appear he had little experience of going around from an aborted landing roll and in the panic of the moment missed a couple of actions which would have almost certainly prevented the accident.
While most of us don’t have the benefit of simulators, we can rehearse many of these life-saving drills over and over in our head or in the cockpit, which will help free up some of that mental capacity to allow us to analyse properly and to make sound judgements when they are needed.
