AUSA --- The SB>1 Defiant is back in the air, reaching speeds of 20 knots on its fourth test flight. It should reach the Army-mandated minimum speed of 230 knots by the end of March, “if we have no other significant things we learn along the way,” Boeing program manager Ken Eland said here this morning.
He’s referring to a less-than-pleasant surprise earlier this year when the Sikorsky-Boeing team discovered unexpected “bearing creep” in a test gearbox, leading them to ground the actual aircraft for almost two months to make preventive changes.
That was the second major delay for the Defiant after losing multiple months to unexpected difficulties building the large, ultra-rigid rotor blades required – although that hold-up was in part the fault of the Army, which asked the companies to try out some novel manufacturing techniques.
But the bottom line is that the Defiant has only made four test flights – three in March and April before the gearbox fix, one after on Sept. 24th – for a total of three hours of flight time – a third of that from the most recent flight.
By contrast, rival Bell Flight’s V-280 Valor tiltrotor first flew in December 2017, 15 months before Defiant. Valor surpassed 100 flight hours and 300 knots airspeed in April, just as Defiant was making its first flights. Bell is now doing extra-credit testing like flying the Valor in unmanned mode. (end of excerpt)
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