"The surviving engine doesn't "take over instantly". The rotor drive trains are mechanically linked. Unless the drive train breaks, both rotors always stay at the same rpm."

Really? What's all this about then: "Under normal operating conditions, each proprotor gearbox is powered by the nearest engine via the engine output shaft. In the event of engine power loss, the proprotor gearbox associated with the failed engine receives power from the opposite engine through the interconnect drive system." (http://www.globalsecurity.org/military/systems/aircraft/v-22-survive.htm) ?

I agree that the surviving engine won't take over instantly--but that seems to be the hope.

You cheerleaders should see if you can't qualify as aircrew on them. Then it'd be *your* lives on the line too. There's nothing like risking your very own one-and-only personal butt to motivate a re-think about what's 'acceptable'.

Posted by: Mairead at January 30, 2007 5:04 AM

"In an Osprey, Vortex Ring State causes it to roll and crash, as only one prop loses thrust."

How is that different than a Phrog, which also has two rotors? The only difference is front/back versus left/right.

"Moreover, the Osprey's surviving the loss of a single engine during STOL operation depends on the fragile technology of the surviving engine being able to take over *instantly* and drive both propellors strongly enough to prevent a fatal roll."

The surviving engine doesn't "take over instantly". The rotor drive trains are mechanically linked. Unless the drive train breaks, both rotors always stay at the same rpm. This is similar to the system on a Phrog, which as noted above also has two rotors, with all the same issues surrounding maintaining power to both rotors. The fact that the Phrog's rotors are front/back versus left/right provides absolutely no safety advantage (at least not in regards to powering the rotors). If the Phrog lost lift in one rotor, it would flip and crash. If the Osprey lost lift in one rotor, it would roll and crash.

"blackhawk's climb/descent rate, I believe, is 2000 feet/minute"

That sounds at least 50% too high.

Posted by: chuck at January 29, 2007 10:22 PM

Will more soldiers die in Ospreys because the pilot descended too quickly despite additional equipment, software, and training? Yes but not in numbers significantly different than combat helicopter losses.

The osprey is a revolutionary aircraft. It offers the ability to self deploy, use aerial refueling, with longer range and reduced susceptibility en route to the fight at the price of additional vulnerability to ground fire when deploying troops compared to a dual engine heavy copter (IMO). As long as it's used intelligently, it is well worth the trade off and should ultimately save lives.

Posted by: Nathan at January 29, 2007 12:19 PM

Glide? You must be joking. My field isn't aeronautics, but one look at that wingspan tells me it will glide like a rock.

The gliders used as assault transports in WW2 had only a 1:10 glide angle because of their limited wingspan, compared to 1:22 for standard gliders. But even their wingspan was on the order of 2X the Osprey's, and their airframe was much closer to a traditional glider's airframe: fabric-covered wood and light metal tubing stringer construction, no engines.

Moreover, the Osprey's surviving the loss of a single engine during STOL operation depends on the fragile technology of the surviving engine being able to take over *instantly* and drive both propellors strongly enough to prevent a fatal roll.

Don't kid yourself. That thing is nothing but a disaster with engines. If it goes into production, all the contractors and the uniformed program staff will be living off the blood of the Marines it kills.

Posted by: Mairead at January 29, 2007 10:20 AM

The Osprey does both (windmill and glide) however. In a catastrophic failure of both engines (which there is a very slim possibility of happening) it can do either/both. Remember in a autorotation, it is not just a straight down descent!! In fact, that would destroy a helicopter quickly when it hit the ground. There is a forward component to it as well, something the Osprey is better suited to take advantage of because it has wings. The wings dont fall off that easily. Plus as previously mentioned, the Osprey can totally lose one engine and still keep on flying. Again, this is an advantage that most US helicopters do not share. Helicopters also have a very vulnerable tail rotor, unlike the Osprey. If that thing quits, you are in a world of trouble as well. It "guarantees a catastrophic failure". Plus many US Helicopters are vulnerable to a phenomena known as mast-bumping, where literally the rotors do fall off the helicopter. The Osprey does not exhibit this phenomena due to the structure of its rotor hub. So, I do not see what is so catastrophic about failure in the Osprey. Please provide specifics next time, particularily as compared to similar helicopter/plane malfunctions.

Any way you put it, aviation is a dangerous game. Particularily in helicopters where the margin for error is small and the things that can go wrong are multitudinous. Our current generation of helicopters as well are ancient things that are reaching the end of their lives for the most part, and the Osprey represents a much safer alternative. I pay attention to the Class A mishap reports... do you?

Posted by: tz at January 28, 2007 2:26 PM