‘Alarms and diversions’
This final part of these flight testing reminiscences describes some highs and lows, and finishes with a scrap-book of some of the many types I was professionally involved with.
Diversions (When I couldn’t believe I was getting paid)
Simulators are engineering marvels. However, a little extra magic can be required to help convince pilots they are dealing with an engine fire on take-off on a rough night out of Jo’burg, when deep down they know they are in a shed on a Crawley industrial estate. This was known as ‘fine tuning the motion’ or ‘tweaking the aero model’. To check the magic was in place, clearing a simulator for testing CAA licence holders included a ‘subjective fly-out’ by a CAA test team. The mysteries of airline politics and economics meant these simulators were worldwide. It always struck me as ironic that in Australia, New Zealand, Malaysia, Turkey, Greece, Finland, the Middle East, South Africa and the USA, we flew circuits at, e.g, Manchester.
Aircraft under test are temperamental, and there could be a lot of time waiting for ‘a quick fix’. The trick, rarely achieved, was for this to happen somewhere you didn’t mind being. On a trip to Boeing in Seattle, we waited three days for a serviceable aeroplane, so we gave up and went home, but not before enjoying glorious Washington State. On trip to Hong Kong (looked after by a CAA outpost in those days), an engine failure early in the test grounded the aircraft, for a very pleasant couple of days.
Once, we hitched a ride home from Seattle on an overnight delivery flight of a new B737. There were only a few rows of seats, served by a small cabin crew, and the presence of the airline’s managing director ensured excellent service. A bonus was a view of the Northern Lights over Greenland.
Alarms (When I wasn’t getting paid enough)
I twice added to my gliding hours in work time. First, in a Cessna 208 turbine single when exploring engine failure landings at Cessna’s Wichita base. This was not too stressful, as the entire state of Kansas is pretty well a giant airfield. The other occasion, which definitely was stressful, was in a B737 flying a timed climb with one engine shut down, when the live engine failed at 12,000 ft, above 8/8 cloud. It takes about a minute to restart a CFM56, which seemed a long time, especially when the first attempt failed, and it all had to be done again. An airlock in a fuel cross-feed line was to blame. ‘Procedural changes ensued’.
We didn’t usually get involved in manoeuvres to investigate loads on the aircraft structure. However we once inadvertently did so, on a B737. The planned test was to assess stability and controllability when penetrating Mach buffet under ‘G’ at high altitude. The test aircraft had an experimental composite elevator, which was strain gauged for on-board monitoring of flight loads. After one burst of heavy buffet, the Boeing structural specialist on board advised against more runs, as the strain gauge instrumentation was lost. It wasn’t until after landing that we discovered that by ‘lost’, he meant really lost, as several square feet of each elevator, strain gauges included, were missing. The elevator horns had experienced ±100g in the buffet, before they fell off. With powered elevators, this was not apparent to the pilot. Had we continued to our next planned test, to assess flight with elevator power off, it would have been very apparent, and not in a good way. ‘Structural strengthening ensued’.