Saturday, March 19, 2011

Mechanical nostalgia

Here's a few old friends of mine that I happened to run into recently at the RAF Cosford Museum.

The first old buddy is a small training aeroplane (American sp: "airplane") called the Scottish Aviation Bulldog. These were operated by RAF Leeming and RAF Church Fenton during the 1970s and 1980s, on behalf of the Royal Navy.

The reason for this strange inter-service organization was that it was considered necessary that Navy pilots, who were later expected to fly helicopters and SVTOL aircraft such as the Harrier "jump jet," be trained in lighter, more aerodynamically vulnerable, piston-engined trainers. The RAF at the time still operated a large number of other piston-engined aircraft, notably the Chipmunk and Ventura powered gliders used then for giving Air Cadets flight experience, and the Avro Shackleton fleet used for submarine hunting. The Navy had no other piston-engined requirements.

Therefore it was considered more cost-effective for the RAF to maintain the stable of piston-engine savvy flying instructors and aircraft technicians needed to run the training schemes for Navy pilots.

I was lucky enough to become one of the piston engine technicians, as part of Aircraft Servicing Flight at RAF Leeming. I say lucky, because it gave me a lot of useful training and experience working on piston engines. Jet engines are fun, and I worked on those too, including the Jet Provost trainer fleet and the F4 Phantom fast jet fighter/attack fleet. But there isn't a lot of useful purpose in civvy street for jet engine experience, unless you want to work in civilian aviation.

Piston engines, on the other hand, are ubiquitous, even on a small farm in Maine. Especially on a small farm in Maine. There's not a week goes by around this farm that I don't have to use my piston engine training for some purpose or another.

So, long story short, when I visited the museum on my recent trip home, I smiled to myself quite happily to turn a corner and see the Bulldog Fleet 3 sitting there. I may even have worked on this particular aircraft, because although the notes said it was from RAF Church Fenton, those kites were often flown up for the RAF Leeming ASF people to take care of. There was also a Chipmunk and even a Jet Provost Mk 3 cockpit set up for kids to scramble in and out of. (I didn't get in myself, but I thought about it.)

So the Navy, slanged (or slagged) as "matelots," were a part of the scene at RAF Leeming in the late '70s and early '80s. Famous Navy "middies" (midshipmen -- officer trainees) who came through this scheme included Princes Andrew and Edward. Andrew, of course, went on to do at least one useful thing in his life, in the battle of San Carlos.

I was chosen to be the fitter to give the middies a walk round of the engine. They'd troop a dozen or so pimpled middies into our hangar and, using whichever stripped-down aircraft was handy, I'd explain how the engine worked, and show them the different parts. They always listened pretty respectfully. I was about their age, but they'd been to university, whereas I'd been on my fitter's course. But I guess you should be respectful to the guy who's working on your aircraft. This went on for a couple of years, and was perhaps the start of my teaching career, this and instructing mountain rescue for the MRTs.

The best thing about working on small piston-engined trainers was the outdoor life. These aircraft were so easy to move around that two or three of us could push them in and out of the hangers easily. The first stage in a scheduled servicing was always a test run of the engines. We'd run them until they were hot, check the "mag drop" and for any rough running, then shut them down, strip off all the cowlings and drain the oil, checking the magnetic drain plug and oil filters for debris. Then we'd spray them clean with gas in spray bottles (today's health and safety rules would never permit this: spraying hot engines with leaded gasoline!), let them cool, and push them into the hangers for a scheduled service.

This was a time-honored routine and probably dated back to the World War I roots of the service in the Royal Flying Corps.

So my memories of the Bulldogs are of long sunny summer days at the edge of the airfield, the smell of 118 octane Avgas and hot oil, and long tea breaks waiting for engines to cool.

It was a nice life.

The servicing work included top-end rebuilds on the American-made Lycoming 360 engines, essentially a giant VW engine, a "flat four" configuration, as well as various routine filter checks and inspections. Everything was on a proper schedule. The engines were sent back to the factory before the bottom end bearings wore out. The variable pitch propellers were removed and replaced, the old ones sent back to the factory.

The cowlings were prone to cracking, and could be repaired using rivets and metal patches, or replaced. The starter motor bracket had to be dismantled and checked for cracks. The mag-drop routine, running the engine first on the left-hand, then the right-hand magneto, to see if the rpm rose or dropped, was a useful way to check the timing was right on. Timing was set using a static light and mechanical contact breaker points, just like an air-cooled VW.

The Chipmunks were also fun to work on, a tail-dragger airframe, with the famous Gypsy Major engine. This engine was an in-line six cylinder, but upside down, with the sump at the top. With this design, the engine was bound to use oil, and it did, draining a huge oil tank, but the engines lasted a long time. Some of the airframes and engines we worked on were already forty years old in the 1980s.

The "Chippie's" starting system was a wonder to behold. The Chipmunk used a cartridge starter, which was essentially a revolver's cylinder filled with giant shotgun shells (blanks). The pilot pulled a string in the cockpit to operate the hammer of the starter, the shell would fire with a crack and a puff of smoke, and the hot gasses from the shell would turn the engine over. You could also swing the prop to start the engine, another time-honored ritual.

I don't know which method was more dangerous!

RAF fighter pilots skipped the Bulldog stage and typically went straight to the BAC Jet Provost trainer, and on to the BAE Hawk. The small jet engine at the bottom is a Rolls-Royce Viper, the engine for the Jet Provost. I did a good deal of ASF work on these aircraft too, including deep strips on the Viper engines, usually for diagnostic purposes. The engines went back to the factory long before they wore out, and were refitted there, but we would occasionally tear one down after a bird strike, or to change a turbine shroud. These shrouds were prone to cracking. Later, after promotion, I became a supervisor of flight line mechanics ("flems") on the Jet Provost line at RAF Linton-on-Ouse, a satellite station for Leeming. That was fun work too, always outdoors, always walking the half-mile long flight line.

The RAF seemed to have an awful lot of Jet Provosts in those days. A lot of them were sold off to civvy enthusiasts and are still flying today as private jets. Expensive to operate, though, because those engines drank fuel. We'd put in a thousand pounds or more of Avtur each time, just for these short one- and two-hour training flights. At seven pounds to the gallon, I can't imagine the fuel bill just for one civvy-street jaunt in a JP.

One very big day while I was still on the piston crew at ASF Leeming, one of the famous Spitfires of the Battle of Britain Memorial Flight came to visit for some reason, and was entrusted to our particular crew for care because we were the piston engine guys. They taxied it over to our corner of the airfield, and I was given the task of doing the After Flight/Before Flight service and filling the gas tanks. It took me a good hour, using the manual, to do all the different checks because it was an unfamiliar aircraft, mechanically speaking.

But, I can now quite honestly say, "I once worked on a Spitfire!"

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