Can the newly contracted Bell V280 Valor operate on one engine?
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1$\begingroup$ Bloody well better or you won't get me in the thing. The Osprey has cross linked transmissions, so I can't believe this one doesn't. Tilt rotors can technically autorotate, but you can't really land them in one piece from an autorotation, so you better hope a double engine failure never happens. $\endgroup$– John KCommented Mar 7, 2023 at 3:03
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$\begingroup$ @John K cross linked transmissions suggests a single point of failure, although hopefully much more reliable than an engine. Still, that’s not entirely reassuring. $\endgroup$– FrogCommented Mar 7, 2023 at 5:07
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2$\begingroup$ According to Wikipedia: "A driveshaft runs through the straight wing, allowing both prop rotors to be driven by a single engine in the event of engine loss." $\endgroup$– sophitCommented Mar 7, 2023 at 7:17
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1$\begingroup$ @Frog You overcome single-points-of-failure by over-building and robustness such that components are immune to fatigue, and/or have mechanical overdesign that result in obvious detectable degradation before something lets go. For ex you may design a drive shaft system with redundant bearings, and, say, a dual-wall shaft where a secondary load path takes over when one fails, AND a way to detect such failure when it happens to minimize dormancy. Stabilizer trim jacks on airliners do this. $\endgroup$– John KCommented Mar 7, 2023 at 13:28
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1$\begingroup$ @U_flow it depends on the failure mode - if the shaft snaps cleanly and the two parts continue to rotate freely then all is well but if the fragments flail around causing collateral damage then it could be much worse. And if part of the mechanism were to seize then it’s likely to end badly for both engines/rotors. $\endgroup$– FrogCommented Mar 9, 2023 at 18:53
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1 Answer
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Yes, the V-280 Valor is equipped with a driveshaft which distributes the engine power from the nacelle with the inoperative engine to the one which still does. This system allows the aircraft to continue to operate in case of a single engine failure (but obviously not both :D).
A similar approach was taken with the predecessor of the Bell V-280 Valor, the Bell Boeing V-22 Osprey. A nice aviation stackexchange question about this system can be found here.
In this source is is stated, that this system also contributed to the design decision of the V-280 to have fixed nacelles and tilting rotors:
The straight wing also greatly simplified the mechanisms needed to connect the rotors with a driveshaft to keep them coordinated and, in case of an engine failure, both rotating. That, in turn, eliminated the need for a mid-wing gearbox, a device that adds 292 lb (132 kg) to the Osprey’s weight and expense to its price.
Which again emphasizes, that the driveshaft between the two nacelles distributes engine power in case of an engine failure.
