G-BEBP

My morning routine begins, like many other people, with a quick catch-up on what’s happened overnight from a short list of bookmarked websites. Inevitably, my list has a few (rather esoteric) variations in addition to the usual BBC/FT/Economist locations. One of these is the Aviation Safety Network website, where a small panel marked “This Day In History” provides a daily link to an instance their database summary of a particularly significant aviation event, usually with far-reaching consequences, for those who are interested.

Yesterdays’ was particularly poignant.

G-BEBP.

I probably need to make a couple of points here for everybody’s benefit.

Firstly, an explanation. www.aviation-safety.net is a reliably factual and highly educational website, run by the Flight Safety Foundation, dedicated to improving aircraft operations safety and reducing accident rates for any and all operations. While it may not cover every incident or accident world-wide on a daily basis, it certainly covers the majority. Contributions are voluntary and (mercifully in this day and age) brief, objective and unbiased, irrespective of the scale or tragedy of the event which has transpired. It is a credit to the Foundation. For anybody – let alone those concerned with aviation and specifically improving the quality of aerospace product design - it should be a must-read bookmark on what can happen and how to avoid it.

Secondly, the significance of the resource. It is, without doubt, the single most useful source of global information on aviation safety that I’m aware of, and I’ve used it extensively in design analysis and safety assessments. I’ve had cause to rely on it for several presentations to ICAO, IATA and EUROCAE, where its data has come through some critical cross-examinations with flying colours. I trust it.

Thirdly, the personal touch. That little “This Day In History” panel on the right-hand side is a subtle “Lest We Forget” reminder of the scale and scope of tragedies that can take place. It also, very usefully, provides links to the accident report and any other accident information that would be relevant. In other words, they’ve minimised the effort you have to expend to get to the information to learn those lessons and prevent re-occurrences in the future. It is a useful and convenient prompt to those who are interested. Which is the whole point behind the website.

May 14th marked 43 years since G-BEBP – a Dan-Air Cargo 707-321C - crashed just short of Lusaka Airport in Kenya in 1977 with the loss of all on board. The tailplane came off just after the crew selected full flap on base leg.

At the time, I was an aeroplane-mad teenager interested in finding out how the aerospace industry worked. Flight International, which I had just started reading as THE world-class technical magazine in those days, carried an article on this tragic accident, but I didn’t attach any special significance. However, over the succeeding weeks from the initial report, there were an increasing number of references to the accident which seemed to imply this was more than just another air transport incident (which were much more frequent back then), but without any background knowledge, the degree of significance was lost on me at the time. However, I was intrigued enough to order a copy of the accident report from my local branch of Her Majesty’s Stationary Office (remember those??!!) when the publication date was announced.

I had none of the background knowledge at that time to be able to comprehend the depth and quality of the analysis set out in the report. But it was my first exposure to the real world of aircraft accident investigation that hadn’t been distorted by media reporting. The report was clearly significant, and gave me an early insight into – and fascination for – the intricacies of aircraft design and flight data analysis. Little did I know then that it would subsequently develop into a skill set that would take me round the world on a wonderful series of great aircraft projects with some fantastic people.

It was the first – and only - accident report I ever bought. It was also struck me at the time as one of the driest documents I’ve ever read.

So when I came across that ASN “This Day In History” link for G-BEBP yesterday, I was on another trip down memory lane, again intrigued to see what I would make now of the report that was so instrumental to starting me on this career path. In particular, now that I have that all important background knowledge in spades, I would know what it meant. And to assess the impact, I tried to frame up mentally from my historical knowledge what it must have meant to the industry when this report was published in 1978.

Having re-read it today, there is only one phrase that comes to mind.

Earth-shaking.

Far from being a dry read (especially since I’ve had to wade through tons of really dull, much worse stuff over the years), this is a beautifully succinct, expertly phrased, highly focused, unbiased assessment (in 1978, remember) of what happened and why, clearly targeted at a very specific audience to make sure this message got across clearly. It was an AAIB masterpiece, not a term I use lightly for an aerospace document.

To cut a long story short, the 707-300 series was a development of the 707-100/KC-135 airframe where they encountered a few problems. One of them required making the tailplane stronger, which was done by changing the skin material. Which involved making a few design assumptions that were okay’d at the time, based on a “failsafe” configuration of the structure so that if one part failed, other load paths could take up the strain safely.

The aerospace industry, as mandated by the regulators, has a system of regular, extensive and thorough checks to catch problems, which are administered religiously. Very, very rarely, one particular failure sneaks through. Even more rarely, it results in a catastrophe. This was one of those incredibly rare cases where the checks were properly administered but didn’t catch the significance of the developing crack until the tailplane separated at Lusaka. Almost twenty years after the design was approved.

The design assumptions, which correctly applied the existing knowledge and regulations of the time, had over-estimated the fatigue strength of the modified structure when approved back in the late 50's.

The analysis in the accident report noted that“…there must be a point in the evolutionary process when the manufacturer or the airworthiness authority (or both) should decide that a complete review is necessary because the basic design can have changed sufficiently for doubts to arise as to the validity of extrapolation of data from the earlier model”.

“Persuasive arguments are regularly put forward both by aircraft manufacturers and the airlines that a modern aircraft designed to failsafe principles should not be arbitrarily limited to a given service life, as the feedback of service experience from the fleet together with thorough inspection procedures would isolate the problem areas before they became in any way critical. The circumstances of this accident have reduced the weight of these arguments for two reasons….”

In other words, anybody who had stretched a decision by making a big assumption on old analysis had better reconsider and re-check the results. And if new evidence came to light casting doubts on old assumptions, you’d better go back and reconsider.

Throughout the aerospace industry at the time, there were a lot of "stretched" designs that had been leveraged from old, original aeroplanes. They all needed checked and any findings acted on accordingly and quickly. Bar none. It took an extensive global joint effort to implement the lessons at no small expense, but both the industry and the regulators moved quickly in the subsequent years from the accident.

Existing aircraft were fixed. New aircraft designs were greatly improved. Airline inspection techniques significantly updated. And reporting was much better co-ordinated. And as a result, air transport today is significantly safer and continues to improve. The Flight Safety Foundation are a contributor in a small but highly significant way by continuing to highlight where things go wrong to remind you that accidents still happen, and to prompt those interested to do something about it.

Aerospace, by the nature of the business, operates on finer margins than terrestrial businesses. So safety has a higher importance, and maintaining safety is uppermost in those directly involved. The effects of failure carry a higher consequence. To paraphrase that old Transport Canada slogan, “If you think safety is expensive, try an accident”. The consequences of fudging it are too severe.

Some observers consider the G-BEBP accident report to be one of the significant points in the subsequent evolution of global harmonisation for aerospace regulations, a process that is still going on today. This process is important in that the harmonisation of regulations has made life easier for all concerned in getting products approved while improving the quality of the product.

But it has not dropped standards one iota. Quite the contrary. Integrity remains paramount in this unglamorous but vitally necessary work. People rarely get kudos for preventing an accident through good design or operating principles, especially when they cost more money. But the accidents of the past – for those who remember them and what they taught us – remind us of the potential consequences of those few instances of bad practise in the midst of all that is good.

The fall-out from G-BEBP has many parallels with the present earth-shaking events. I’ll leave it at that.

Dedicated to the memory of the G-BEBP crew.

Lest we forget.