Now, here’s the important part about how this was missed — Page 322, Lesson 524

Let’s start with the medical condition of the captain at the time of the accident. Captain Key was suffering from arteriosclerosis — that’s a condition where the walls of your arteries thicken and lose elasticity, narrowing the passage for blood flow. In his case, many of the arteries in his heart had narrowed to around 50% of their normal width. That’s a severe restriction. Now, here’s the important part about how this was missed. His annual ECG — that’s an electrocardiogram, a recording of the electrical activity of the heart — was conducted at rest, meaning while he was sitting still. A resting ECG did not show the problem. What would have caught it is a stress ECG, which records the heart’s activity while the person is physically exerting themselves, like on a treadmill. But the regulatory authority at the time was not using stress ECGs for routine screening. Why? Because trials had shown that stress ECGs produced too many false positive results — meaning they would flag a problem that wasn’t actually there, leading to unnecessary grounding of healthy pilots. So, because of that reliability issue, the defect in Key’s arteries went undetected. The consequence was stark: at the time of the accident, Captain Key’s life expectancy was already quite short — measured in months, not years. Now let’s move to the other crew members. Jeremy Keighley was a Junior Second Officer with BEA — British European Airways. He was very inexperienced, both as a pilot overall and specifically on the Trident aircraft. He was one of the pilots affected by an industrial dispute, and as a result, he was only qualified to fly in the P2 position — that’s the co-pilot’s seat on the right-hand side. He had still not completed his training as a Flight Engineer. Personality-wise, he was described as shy and retiring, not someone who would readily speak up with his opinions. During his training, he had been criticised as being slow to react and lacking initiative. His training reports suggested he would need careful, patient coaching to get the best out of him and that he should not be pressured during his training. There’s also a relevant personal detail: Keighley shared a house with another Junior Second Officer who had recently flown with Captain Key and had been subjected to one of Key’s outbursts when he made a mistake on the flight deck. So Keighley was aware of Key’s temper. Simon Ticehurst was occupying the Flight Engineer’s position, which is the P3 seat. He had 1,000 flying hours total, of which 750 hours were on the Trident. He was described as a very capable and thoroughly reliable young pilot. Now, let’s turn to the aircraft itself — the Trident. The Trident had several ‘interesting’ design characteristics that were probably involved in the sequence of events leading to the accident. The most critical of these was a tendency to deep stall. The Trident was a three-engine aircraft, with all three engines mounted in a group around the tail. This configuration had aerodynamic advantages: it allowed for a very clean, aerodynamically-efficient wing, and it also reduced the aircraft’s tendency to swing during take-off if it lost an engine — because the engines are close to the centreline, the asymmetric thrust effect is smaller. However, this same tail-mounted engine layout also created the possibility of a deep stall. Here’s why: as an aircraft approaches a stall, it flies with an increasingly nose-up attitude. In a deep stall, the turbulent air from the stalled wing flows back and blankets the tail, making the elevators ineffective. The aircraft then becomes uncontrollable and irrecoverable — you cannot push the nose down to recover. So, to summarise what we’ve covered: Captain Key had severe undetected heart disease, the co-pilot Keighley was inexperienced and hesitant, the flight engineer Ticehurst was capable, and the Trident aircraft had a dangerous tendency to enter an irrecoverable deep stall due to its tail-mounted engine configuration.