BAE Systems' Graham Tomlinson, aka "GT", lead test pilot for the STOVL F-35B, says that, with today's first vertical landing, the flight-test team has "joined the dots" on everything the US Marine Corps (and the UK and Italy) need to operate the aircraft: from short take-off, conversion to conventional flight then back to STOVL mode, to vertical landing.
Photos: Lockheed Martin
But on a phone-in press conference following the flight, GT was careful to point out that, so far, the line joining those dots is only "a soda straw ... We've covered the whole gamut of STOVL operation, but only in a narrow part of the envelope." This early in the test program they are flying the F-35B with "velvet gloves" and the next task is to "expand the envelope and fly more aggressively, more carefree", he says.
For the first vertical landing, because what would happen when it entered ground effect was unknown, the aircraft was flown light to ensure there was a good thrust margin, says GT. "But we didn't see any ground effect. That was a miracle, and unexpected." When the aircraft descended below 20ft and entered the fountain effect from the engine, lift-fan and roll-post exhaust flows, GT says he "felt very light cobblestones, far lower than in other [STOVL] aircraft."
Tomlinson had just come from the post-flight debrief, where he says "the loads, thermal, air-data and control-law guys were all smiling." There were no signs of ground effect in the engine or thrust data, he says. Lockheed has previously said that the cool flow from the lift fan acts like a dam, preventing hot gases from the main engine being re-ingested through the inlets.
Today's flight began with an 80kt short take-off, 20kt slower than yesterday's first-ever STO. GT says the take-off was "absolutely solid, and acceleration was excellent" under the influence of 40,000lb-plus of thrust from the engine and lift fan. Rotation was just 6-8sec after brake release, he says.
And GT says the data from today's vertical landing shows the F-35B is on track to achieve the predicted bringback payload of around 5,000lb in unexpended weapons and fuel reserves.