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UP, UP AND AWAY
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Forget James Bond's Aston Martin DB5 — its ejector seat was only a special effect.
To see the real thing join Colin Barnett for a jaunt in a Leyland Boxer...
If we told you that the fastest working truck in Britain was a humble Leyland Boxer, you might think we'd finally lost our grip. If we went on to reveal that it plays a vital role in saving the life of one military flier almost every week, while helping prolong the active life of two of the oldest operational jets in the world, you'd believe we were talking balderdash. But you'd be wrong.
Commercial Motor was recently invited to visit the Martin-Baker test site at Chalgrove Airfield in Oxfordshire to see this remarkable vehicle.
It might seem obvious that attention to every detail is critical when considering throwing a pilot or crew member out of an aircraft travelling at 650mph or more, but it's not that simple.
Martin-Baker's pair of Gloster Meteor jets is kept operational to carry out test ejections at flying speeds, but ejector seats also have lobe capable of safe operation throughout nearly every aspect of a sortie, including at ground level during take-off and landing. And this is where the Boxer has had its part to play in recent years.
Ever since its ejector seat division was formed just after the Second World War, the Martin-Baker company has operated its own fleet of trucks.At Chalgrove we saw the current Volvo FL curtainsider performing typical fetch-and-carry duties that had once been handled by the Boxer we'd come to see.
Inside the hangar where the two Meteors and the company Beech King Air transport aircraft are hangared, a Carmichael crash tender vehicle was on stand-by. Its predeces sor, a Bedford MK with the unusual luxury of powersteering, is stored nearby awaiting a new home.
Only three trucks have been elevated to the role of ejector-seat test rigs. The first was a Leyland eight-wheeler, almost certainly an Octopus, and it appears this truck was once taken to sea to test underwater ejection seats required by two Royal Navy aircraft many years ago.The second was an AEC— and both were pretty slow.
When the Boxer came into the frame a new set of circumstances were coming into play; not least cost-effectiveness. Until the Boxer came on line one of the Meteor fighter/trainer hybrids was used for test runs on the Chalgrove runways, minus its outer wing sections. However, with fuel consumption of around 240gal/hr it soon became apparent that it would be much cheaper to use a truck for these duties, leaving the aircraft to do what it was designed for. To cut a long story short, a couple of Martin-Baker's bog-standard Leyland Boxer 'drop & stop' trucks were sitting in the yard at the firm's main Martin-Baker factory at Denham awaiting disposal when the nearby Croft Brothers operation said it could adapt one to do the job.
The answer was really quite simple. Croft Bros enlisted the help of specialists at the Stuartihrner Gearbox factory to help build a unique gearbox.The exact spec of the driveline is unknown, but the gearbox has fairly close lirst and second ratios, then a huge step up to third.A pair of 14.00x20 rear tyres don't just give the truck a dragster-like stance; they increase the overall gearing by nearly 25% compared with the standard 10.00x20.
The engine, originally rated at 140hp, remains fairly standard, apart from the lack of any form of govemor.The resulting extra revs help bridge the large gaps between gears and increase top speed.
Big red button
Its emissions don't bear scrutiny; apparently Croft Brothers advised changing the engine oil and filters after every test run programme. The cab is fairly normal and,it has to be said, rather tatty. Only a couple of extra instruments and two sets of full harness seat belts mark it out as unusual. Oh, and the big red button strapped to the crewman's thigh that fires the seat!
The bodywork amounts to no more than a plate on top of the chassis to which the ejector seat is attached.
With a payload similar to an Astravan, the Boxer isn't highly stressed when it comes to moving away, but the high gearing still needs a bit of clutch slip to get going. Acceleration is pretty brisk, but top speed is limited by the length of the runway. During our test run, fifth gear was engaged with just over 70mph showing on the (correctly calibrated) tachograph, and it was still pulling strongly when the boundary hedge loomed up. Apparently,it just about reaches a ground speed of 100mph within the confines of Chalgrove.
But while tachographs may be reasonably accurate, ground speed is irrelevant for the Boxer's duties. Martin-Baker's test programme requires accurate measuring of air speed, which explains the length of telescoping tubing across the back of the cab.This carries a pitot tube to operate those extra instruments they are air-speed indicators.What might be felt as a gentle summer A Ready for take-off. The test bed prior to a launch breeze could in fact be a 15 knot wind, producing a difference between air and ground speed way outside the parameters needed for test firing.
You'd think the Boxer's calibrated tachograph would accurately measure its speed,but not so. To explain this. and exactly why a pitot tube is necessary,youneed to understand-as we certainly did-what atypical test run involves.
You've probably heard the slang term `bang seats',but this is a rather derisory phrase for a highly sophisticated piece of technology that has been painstakingly developed for more than half a century.Towards the end of the war, the founders of the Martin-Baker company were aware of some primitive work done by the Germans in developing ejection seats.
They convinced the powers-that-be that they could provide a working product, and were even the task together with sole access to a redundant airfield at Chalgrove in Oxfordshire. The company soon established a world leading role in this essential and lifesaving sector of military aviation; a position it still maintains. Although every example built is specific to its intended aircraft type, the basic MartinBaker ejector seat is now the MUCVI.The seat fitted to the Boxer during our visit is destined for a NASA T38 trainer.
After the pilot decides to get out, his seatbelts and leg restraints are tensioned, rapidly followed by being pushed upwards and clear of the cockpit on a telescopic pole before the rocket motors fire.
These produce 5,500lb of thrust for a quarter of a second, hurling the seat some 50m. At a safe height the seat is automatically jettisoned and the pilot's parachute deploys.
Simulated ejection
The planning and lead-in time to a test run or simulated ejection can run to weeks or even months. A vast array of sensors and measuring devices beyond our ken are installed,including within the dummy 'pilot'.
Martin-Baker has its own film and photographic unit on hand to record the event, which takes place so quickly that it's over before the human witnesses have registered the 'bang'.
Of the 70,000 or so seats built to date, around 10% have been used in emergencies.The company website at www.martin-baker.co.uk keeps a tally; and at the time of writing it stood at 7,085, including 45 so far this year.
Consider that most firings save a life and you can see why there is a thriving club of ejection survivors, who proudly wear a special tie as a membership badge. •