04 October 2005

Defining Success Downward

No, this isn't a post about Iraq. It's about the V-22 Osprey, the tilt-rotor combat transport aircraft that has already become infamous for fatal crashes during training. Via Michael Froomkin, I see that POGO has a recent report (warning: non-searchable PDF) on the V-22's shortcomings by acting Director of Operational Test and Evaluation David Duma. One of the most notable observations is that one of the initial requirements for the project, autorotation, was dropped when they found the V-22 didn't meet that requirement. POGO summarizes:
Can't Autorotate. One of the more significant formal V-22 military requirements was that the aircraft be able to land safely in helicopter mode without power, a procedure known as autorotation. But after the Marines discovered that the aircraft can not autorotate like most helicopters, it dropped this requirement, claiming such an emergency had a "low probability of occurrence." The autorotation or soft-landing requirement is one that helicopter pilots claim has saved lives on numerous occasions. But even on those rare occasions when power is lost, the new DOT&E report flatly concludes "emergency landings after sudden dual engine failure in the conversion/VTOL (vertical short takeoff and landing) mode below 1,600 feet above the ground are not likely to be survivable."
Maybe I'm just weird, but it seems to me that the aircraft should be fit to the requirements, not vice versa. The official report goes into more detail, including the reason for the 1,600 foot cutoff (all typos and emphasis mine):
While a V-22 has never experienced a sudden engine failure, flight test and engineering analysis indicate that the V-22 is not capable of autorotation to a safe landing.
In the event of either a sudden dual-engine failure, or a single failure of one engine coupled with a failure of the interconnecting drive train when the nacelles are [at] less than 60 degrees [from parallel to the wings], the recommended emergency procedure is to tilt the nacelles down, attain the best glide speed, and flare to a survivable landing. To convert the nacelles from 60 to 0 degrees requires about eight seconds and the aircraft must be above ground level by at least 1,600 feet in order to complete the conversion prior to impact. Impact-attenuating seats and other survivability features can provide protection for passengers when failure occurs below 100 feet above the ground. Pilots practice the procedure in the simulator because of unacceptable risks in flight.

Emergency landing profiles following sudden dual-engine failure with the nacelles at 60 degrees or higher are more problematic. While the likelihood of such an occurance is mitigated by system design, a portion of assault missions will be accomplished by this mode of flying, e.g., carrying external loads and vertical takeoff and landing in tactical zones. Dependent on altitude, the aircraft manual directs conversions to aircraft mode or autorotation.
Notice a little disconnect there? Now, I'm by no means an expert on this, but it seems to me that defining success downward is a tacit admission of failure.

I should add, perhaps, that this is simply the shortcoming that caught my eye. Others, such as POGO, have criticized the program more for the V-22's vulnerability to VRS during descent, which caused the fatal Osprey crash in April 2000. Reading the official report, it appears they have at least partially addressed that issue by implementing a cockpit alarm to warn when the aircraft is maneuvering in a way that leaves it vulnerable to VRS. But Michael Froomkin says really all you can about the V-22's ongoing vulnerability when operating in dusty conditions: whaaaa..? This is even more bizarre in light of one of their chosen training exercises, a re-enactment of Operation Eagle Claw. For the sake of completeness, they did actually manage to meet a previously-disregarded project requirement, survivability in "medium-threat environments". And it sure works better than any missile defense fantasies.

<< Home