Friday, October 5, 2012
Reflections on a Career in Flight Testing
When Andrew Strachan, chairman of the Royal Aeronautical Society’s Flight Test Group, said that every politician and journalist should hear Society Fellow David Gibbings’ lecture on “The Helicopter Development Process: from Concept to Service,” he was right.
People on the outside of an aircraft development program rarely get an insight into the sheer volume of work that is involved in an aircraft’s development journey. Gibbings’ lecture covered all the bases, from the initial procurement dilemma of what to buy all the way through to the aircraft’s introduction into service. The creation of the specification documents resulted in a very complex matrix with project compliance at the heart across all areas: from design through to rig demonstrations and flight demonstrations. Any non-compliant features will have to be thrashed out although this may lead to mutual agreement.
Gibbings is an ex-Royal Air Force (RAF) navigator whose career began in the late 1940s. On leaving the service he held positions with Fairey Aviation as a flight test navigator and propulsion development engineer, latterly working on the tip jets of the Rotodyne British compound gyroplane. He even got to fly in it as a flight engineer.
When Fairey became part of Westland (now AgustaWestland) he worked on the military Scout and Wasp helicopters, as well as the Gannet AEW aircraft. In 1967 he was appointed flight test engineer for the Lynx and flew on the prototype’s first flight. Subsequently he became icing trials manager then in 1980 was promoted to deputy chief flight test engineer in 1980 and chief flight test engineer in 1989, retiring in 1993.
Gibbings has much sympathy with those whose job it is to procure equipment. “One of the things you quickly learn is that the new requirement won’t match the one you want to build them,” he said.
Flying rate, said Gibbings, was not necessarily a true measure of progress as some tests are weather dependent (icing, hot and high)—and the right conditions need to be waited for or sought out elsewhere.
Almost a necessary evil are the marketing requirements involving the prototypes putting on demonstrations and displays at air shows. “They say they want it for a week, then something breaks which we have to fix and it invariably costs us another two weeks to put it back to how it was,” he recalled.
By the time the tests have progressed to the avionics, the feeling is “the toy has grown up” into an aircraft. At the first flight we expect the whole factory to turn out—and so they should. One of the key factors should be the telemetry display: “We need to read at a glance what is happening.” Gibbings went on to point out that the design of the test aircraft crew stations was important, as well as a conceived allocation of test parameters to individual test aircraft.
The vehicle flight tests take between 100-150 hours then again the same with the systems tests. “Never design a new aircraft with a new engine,” was a Gibbings’ observation. In terms of testing the avionics he advised using a mature aircraft with the highest available standard of equipment. “Eventually you end up with the mission system tests on the whole aircraft. This is where you have three pilots with 10 opinions between them.”
Deck landing tests are some of the most difficult to run in a good sequence. “Ideally you want a calm day at the start and end up with a force 6 gale to allow for gradual progression in difficulty. That never—well, rarely—happens.”
For most involved directly in testing, Gibbings stated that the “design freeze” usually comes too early for those intimately connected to the program and nearly always causes problems. To the outsider it must be a decision akin to buying a computer—then is never a perfect time, although in this case the customers are waiting. He added that international collaboration can easily double the timescale of any development program: “Everyone wants the lead technology and there is a need to allocate the new/high technology tasks as well as establishing ownership of the design authority.”
I got the chance to ask his impressions of the ever-increasing impact of better computing power and whether, as a test pilot, he considered that the community in general would benefit from greater openness. He answered by saying that technology creates its own problems while solving others, and that sharing testing results would be valuable but he still didn’t see how this could be done without each developer losing their hard and recently won competitive edge.
The final irony, he said, was that when all the testing had been completed and the aircraft was entering service, the process to identify its replacement had usually already begun—at least in theory.