A350 VMU test: finding the slowest safe speed for take-off . “We brought several tail bumpers but we only needed one to do all of tests.” Video

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Velocity Minimum Unstick (VMU) test, it´s a critical test for aircraft certification. What it does is measure the slowest safe speed an aircraft can go and still achieve take-off, or “unstick” itself from the runway.

 

Prior to the test, a metallic “tail bumper” was attached to the bottom of the aircraft, towards the rear. This prevents damage as the angle of take-off would otherwise cause the fuselage to drag along the runway.

The test crew found the needed calm conditions at a little-used airport outside Paris on 28/September. Going as slow as 130knots (about 250km/h- the flight crew made 12 test runs over the course of 3 and a half hours.

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Teamwork.

Hugues Van Der Stichel sat in the right-hand seat of the cockpit and was responsible for controlling the aircraft´s pitch or angle of attack.

Frank Chapman sat in the left-hand seat and was responsible for controlling the aircraft´s roll, it´s side to side motion.

Pascal Verneau test engineer worked the thrust control.

Philippe Séve was responsible for the test preparation and was monitoring flight test instrumentation data for the tail bumper.

They performed the test 12 time because they used 4 different settings for the wing flaps and then had 3 different speeds for each flap setting. “With the higher speeds, we had less time to stabilize the pitch”, said Hugues. “But the lower speeds were a bigger challenge because there wasn´t uch runway left if something went wrong.”

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