Original URL: https://www.theregister.com/2010/01/04/mull_of_kintyre_chinook_dead_horse/

Please shut up about the Mull of Kintyre Chinook crash

RAF Chinook fleet is actually a rare MoD success story

By Lewis Page

Posted in Legal, 4th January 2010 14:42 GMT

Analysis New information is said to have emerged in the case of the 1994 RAF Chinook helicopter crash on the Mull of Kintyre. Internal MoD documents, casting doubt on the safety of the engine-control software in the wrecked Chinook, have been leaked to the media.

According to the BBC and venerable IT mag Computer Weekly - which has investigated the Mull of Kintyre crash with almost unbelievable thoroughness (vast pdf here) - today's unpublished documents indicate that the UK military flight-test centre at Boscombe Down had serious concerns about the reliability and safety of the Full Authority Digital Engine Control (FADEC) system used to run the RAF Chinook Mark 2's engines.

The FADEC system, which interposes software between the pilot and direct control of the engine's fuel flow - much as many modern "fly-by-wire" systems eliminate mechanical connection between cockpit controls and aeroplane elevators, ailerons etc - was just being introduced when Chinook ZD576 crashed in poor visibility in June 1994, killing all 29 people on board.

An initial RAF investigation concluded that the pilots had made an error and flown the helicopter into the ground, a mistake which is all too easy to make when flying on instruments at low level in poor visibility. However the pilots' families and campaigners on their behalf have always said that a problem with the FADEC software might instead have caused an engine on the helicopter to go out of control and cause a crash.

Various commentators and analysts examining the Mull of Kintyre crash have suggested that the RAF's decision to go for full digital engine control was unwise, that such systems are somehow inherently dangerous or unusual, and that some kind of analogue electromechanical backup or override should have been retained.

That viewpoint, however, has pretty much been consigned to the dustbin of history. New helicopters are nowadays routinely supplied with FADEC-controlled engines, and most older ones have now been retrofitted with the technology. There are nowadays more than 1,000 Chinooks flying, almost all FADEC equipped. Most other choppers also use such kit nowadays.

Full-authority digital control isn't used just for fun. Helicopter engines are, by the nature of their task, often worked very hard - it's very easy, with a manually controlled turbine, to push needles past red lines and cause serious damage. Pilots don't need the distraction of trying to manually control their engines while at the same time performing difficult feats like landings, or instrument flight. FADEC is actually safer than direct pilot control, and indeed the Chinook Mark 2 and its much larger companion CH47-D fleet in the US have had a good safety record since the Kintyre crash. FADEC is also widely used on aeroplane engines nowadays.

But in 1994 FADEC was fairly new in actual flight service, certainly new to the RAF Chinook fleet. It has long been well-known that test pilots and engineers at Boscombe Down had concerns about the original system fitted to the Mark 2 Chinooks. The software - the worrisome bit - was actually written by British programmers at the company known at the time as Hawker Siddeley, since absorbed into the BAE Systems empire, working for US engine firm Textron.

Several subsequent investigations have said that the FADEC could have caused the crash, though if it did so the resulting sudden power loss or overpower before the crash must have been transient - the engines showed no sign of fuel loss or damaging over-revving at the time of impact, and the crash investigators said "available evidence of instrument indications and control settings in the aircraft suggested normal operation of both engines". Again, if an engine had merely powered down briefly, expert pilots like Flight Lieutenants Cook and Tapper - both selected for operations with special forces - would have been expected to manage a safe landing, or at least a Mayday call. Even in a sudden power runaway, at least a partial call would be likely from pilots of this sort, but none was received.

We're finally buying a lot more FADEC-equipped Chinooks, and a good thing too

Overall, considering the sequence of events, it seems a lot more likely that ZD576 flew out of cloud to find rising ground unavoidably close and crashed within 3 seconds. But it's remotely possible that the FADEC could have chosen to do something bad just at the exact moment the helicopter was about to fly into a hill, or in the immediately preceding seconds, so one could give Cook and Tapper the benefit of the doubt - not that they are being tried for any criminal offence.

In the end, though, helicopter flying is always dangerous, and low-level poor-visibility helicopter flying is very very dangerous no matter who you are, though sometimes necessary in the military. It's no dishonour to a pilot, no stain on his reputation, to say he could have made a mistake under such conditions. It's no slight on Cook and Tapper to say that it's likelier they flew into a hill under those conditions than it is that the FADEC chose that exact moment to play up. (If you want to be nasty to the dead pilots, you would ask why they were flying so low in such terrain and such conditions - a factor that the FADEC can't be blamed for - but that's beyond the scope of this article and we see no reason to be nasty.)

For most of us, who aren't friends or relations of the dead aviators, this isn't a very important issue. The Chinook FADEC system, and FADEC technology in general, has since been conclusively proven to be safe. That might be due only to subsequent modifications in the case of Chinooks, but it is a fact. The view of at least one expert that the system "could never have really been corrected to a 'flight safety critical' standard by subsequent patching" has been disproved.

As for today's "new" 1994 documents, all they say is that Boscombe Down didn't think the FADEC had been proven safe at that point, which was already public knowledge. The "new" documents may not have been seen by news media before, but they've been available to the investigating panels. There's really nothing new to see here.

There have been plenty of real news stories about RAF Chinooks since 1994. The scandal of the MoD ordering 8 custom-modified Mark 3s, and then deciding on its own initiative that they were unsafe to fly, is one of them, though that horse too has been flogged well past the point where it was beginning to rot.

Much more significant, however, has been the fact that the RAF's Chinook fleet has been its main success story of the 1990s and 2000s - and arguably the 1980s too. In Iraq, Afghanistan, Bosnia, Kosovo, Sierra Leone and many other places the Chinook has been the backbone of our forces' frontline airlift. Chinooks cost less to buy and run per ton lifted than any other chopper in British service, and are usually more likely to be serviceable. They are the only helicopters we have which can really cope with the heat and high altitudes of Afghanistan.

The real Chinook scandal has been the MoD's consistent refusal to buy enough of them right up until the end of last year, instead needlessly squandering our cash on ill-judged refits of old Pumas and buys of much smaller numbers of inferior makes like the Merlin HC3 and Lynx "Wildcat" - decisions which will have been made much easier by the constant drip drip of Mull-of-Kintyre and unflyable-Mk3 stories in the UK press.

Britain's pathetic lack of helicopter lift resulting from these decisions - in part resulting from these constant stories - has surely killed a hell of a lot more British servicemen than the 1994 crash did. Our troops may not actually receive the Chinooks finally ordered late last year until most of them have come home from the murderous Afghan fighting - thanks a lot, BBC. In particular, thanks a lot Computer Weekly.

The feelings of the dead pilots' families are understandable, but it is time - so long past time - for the rest of us to forget about the Mull of Kintyre crash, and be pleased that our boys and girls in combat are getting some more FADEC-equipped Chinooks at last. ®