Today marks the 30th anniversary of the Kegworth air disaster – a crash which has since become a standard in CRM classes.
The story is well-known: Blade failure on the number one engine resulted in the pilots mis-diagnosing the problem, shutting down the number two engine instead. This led to the disastrous outcome, costing 47 of the 118 passengers their lives, with 74 people suffering serious injuries.
Airways Magazine today published an Op-Ed about it, which singles out one of the major lessons learnt – because of the subsequent research into effective brace positions, safety cards and crew briefings, major changes were made to the way passengers are taught to brace for impact. (Click on the link).
While many factors were at play here – and we use many of them in our initial courses as examples of absent CRM – to me one of the most interesting factors is the (then) new CFM-56 engine. These engines were reasonably new in 1989, only being operated on a commercial jet for the first time in 1981. The B737-400 was also a new aircraft, first operated in September 1988. The accident airframe, G-OBME, was only delivered to British Midlands in October 1988 – two-and-a-half months before the crash.
The CFM-56 used on the -400 was an uprated version of the engine used on the earlier -300 variant. (The -300 was launched in 1984).
To uprate the -300 engine from 20 000 pounds of thrust to the 23 500 required for the slightly larger -400 required only an electronic chip to increase the N1 (RPM). However, this modification was never tested in the air, only on a test rig, before being certified for use on the -400. Unknown to the manufacturer and operators, blade stall became a problem above 10 000 feet and this was what eventually resulted in the blade failure on the accident aircraft.
The problem was easily rectified, and the CFM-56 is now probably one of the most reliable engines ever built.
However, it took an accident to lead to this improvement.
Too often this is the case. We learn from each accident and try to understand all the factors involved – in an attempt to avoid similar accidents occurring. But all to soon, it would appear, we become complacent about those lessons learnt – and only yet another crash leads us to question whether we’ve actually learnt anything at all!
Take, for instance, the recent crash of a LionAir B738-Max – to my mind also caused by a design change which caught everyone by surprise. (Although the previous crew to fly the doomed aircraft experienced the same problem, they had the resilience to recover the aircraft by reverting to good old manual flight). However, without the knowledge about the potential problems associated with the MCAS system, the accident crew were clearly confused by the malfunctioning automation and were unable to regain control.
To my knowledge the British Midland crews had been operating B737-200 aircraft before, and only attended classroom differences training before flying the -400. As someone who has flown many of the variants, ranging from the 737-Basic to the B738, I know that the only way to convert from the -200 to the -400 would be proper simulator training – they are quite different aircraft. This lack of training could well have been another link in the Kegworth accident chain.
And now pilots were once again expected to convert to a new B737 model with a little classroom video and a CBT test.
It would appear to me that we’re not inventing new ways to crash, we’re simply repeating the same mistakes over again.
In the same breath I must add that we have certainly come a long way since the Kegworth disaster. The recently published accident statistics bear testimony to the fact we are on a sustained downward trend, and flying is in fact safer than ever.
It’s just such a pity that we always have to remember accidents like Kegworth, to remind ourselves of the potential for disaster.