Like a bad stain, it seems the V-22 Osprey can’t wash away the stigma that it’s crash-prone. The main culprit: so-called vortex ring state, a circulating, donut-shaped air flow that can cut a copter’s lift, almost instantly. VRS helped down a pair of Ospreys seven years back, killing 23. And those blood spots should be hard to get out. But how accurate is the recent criticism that the V-22 remains dangerously and uniquely susceptible to VRS and blade stall?
After months of flight testing, the Marine Corps and Osprey’s makers, Boeing and Bell Textron, said VRS is no more of an issue than for other rotorcraft: something that pilots need to be aware of, but not something they should freak about. And it’s not something that only test pilots are qualified to avoid. Contrast that with Lee Gaillard’s critical report which depicts VRS as a monster waiting to devour any distracted pilot who wanders outside of a very narrow arrow of the flight envelope.
What’s the objective bystander to think? Gaillard makes much ado about how the Osprey is limited to vertical descents of 800 feet per minute (only 9.1 mph, he emphasizes). He says such a slow descent would make the Osprey a fat target in a hot landing zone. But 800 fpm is a meaningless number when separated from horizontal speed; and the report never mentions that the 800 fpm limitation only applies when forward airspeed is less than 40 knots.
Above 40 knots, the limit on vertical descent grows dramatically until, in full airplane mode, the Osprey can, like any airplane, drop like the proverbial brick. NAVAIR says the 800 fpm-descent limit at less than 40 knots applies to ALL Marine Corps helicopters, and that flight testing showed that the V-22 doesn’t get close to VRS until 2000 fpm. Furthermore, the V-22 can swoop in from high altitude at more than 200 knots and not start slowing down until it’s a minute and a half from the landing zone, minimizing its exposure, says NAVAIR. And it’s 75 percent quieter in aircraft mode than the CH-46 and CH-53 it’s supposed to replace.
But what does the Navy know? For comparison, look at the UH-60 Black Hawk. A Black Hawk pilot told me he sometimes sees 2500 fpm descents when coming into an LZ doing 60 or 70 knots. That’s a vertical speed of 28 mph (only!), but apparently it’s no problem for the ubiquitous, beloved and combat-proven Black Hawk. Why would anyone think a V-22 carrying 60 knots forward airspeed would be any worse?
So while critics are all hung up on 800 fpm, it’s really no big deal. The Gaillard brief has lots of information, but, in the end, creates more heat than light. At least on this issue. For his work mapping the V-22’s VRS envelope, Boeing test pilot Tom Macdonald was honored by the Society of Experimental Test Pilots in 2003. Macdonald wrote the book on VRS and how fleet pilots can avoid it. I met Macdonald, an ex-Navy helo pilot, at Patuxent River Naval Air Station. He didn’t seem like the kind of guy who would hide facts that would endanger other pilots or Marines. Ditto for his testing partner, Marine Col. Kevin Gross, who has written a detailed piece about the V-22 and VRS.
Is the Osprey perfect? No, but what aircraft is and who defines perfection anyway? Is it a widow maker as its critics claim? If yes, than it seems doubtful that VRS will be the culprit. But the jury is out. While it seems Osprey critics may be wrong about VRS, that doesn’t mean their other criticisms are off the mark. Make no mistake: the Osprey is a historic achievement. But it is crazy expensive and still has flaws such as its lack of defensive firepower and a pressurized cabin, which will seriously reduce its advertised range and speed while carrying troops. The question is whether those issues can be fixed or whether operators can find practical ways to work around them. We’ll wait and see what the guys who fly and fight in it have to say.
–Ron Laurenzo, cross-posted at War Is Boring
Glad to see this.
However, I think a figure would be worth 1000 words, and would probably HELP the osprey case:
On the Y axis, have “Descent rate (FPS)”.
On the X axis, have “Forward Rate (MPH)”.
Graph both the Blackhawk’s flight envelope and the Osprey’s, for both the recommended “Do not exceed” profile and where vortex ring state kicks in (the “you’re F@#)($*ed”) profile. Yeup, basically the “descent” portion of the flight envelope.
The typical helicopter has no such restriction on its rate of descent at low speeds, and would certainly not flip upside down should a pilot chose to descend faster. The comparison of TR VRS to helo VRS is a chilling one. The TR loses control, flips upside down and creates a disaster when it is flown into the VRS region, which is close to its operating regime. Close enough so that it was found by the earliest OTE flights, disasterously.
Regarding helicopters and descent rate limits, no helicopter has such restrictive limits on approach. The “limits” that TR folks have quoted for helos to say they have “similar” limits are the landing gear structural limits based on ground contact, and have nothing to do with this discussion. They are a distraction that TR folks use to cover for the obviously poor capabilities of the TR.
I have flown at thousands of feet per minute descents in many helicopters at speeds near zero knots, and so have most helo pilots. To say that this is a forbidden zone is absurd. To know that doing so will flip you upside down should be a warning that the air vehicle that has this limit is not fit for combat insertions.
Furthermore, the small maneuver capability of the TR at lower speeds, less than 1.3 g’s in helo mode, is a severe impediment to combat landings, and makes the TR a sitting duck on any contested landing. Helos have a much larger envelope, and are much more nimble at the close-in approach and departure regimes.
I agree that such a diagram would be invaluable in understanding the phenomenon, but fortunately detailed plots of military aircraft performance are generally classified. I say fortunately because that information is just what an enemy wants to have to find out where the vulnerabilities of a system are. All the armchair Quarterbacks will just have to pontificate without all the data as usual and pooh-pooh the decisions of those who both have all the information and will have to bear the cost of any error. The fact that the Marines are so hot to get this bird into service ought to indicate to any reasonable person that they believe that whatever drawbacks the design may have are more than made up for by the increased capabilities that come with it as well.
It’s going to be a PR disaster the first time the V-22 crashes into an Afghan mountain, or is shot down in Iraq. I would only be impressed by the V-22’s performance, if it could rescue people on the top of Mt. Everest, or is armored like an A-10. Since that is not the case, I think it’s waste of money; it’s a good idea, but not for combat ops.
A quick correction first off…VRS was responsible for the April 2000 crash. The Dec 2000 was in part, caused by a hydraulic leak. After the April 2000 crash, the VRS envelope for the V-22 was thoroughly tested as well as procedures for avoiding and if necessary flying out of VRS
As for VRS and the V-22, the article above said it best…it is less of an issue than critics are making it out to be, a lot of smoke and no fire.
Having been a crewmember on a USAF special operations helicopter for eight years prior to coming to the CV-22 three years ago, I remember having VRS warnings in my Dash-1 for the MH-53M that I was a flight engineer on. In particular, it highlighted the conditions for VRS as being a vertical velocity of more than 800fpm, airspeed less than 40 KIAS, and power applied to the rotor system. The procedure to exit VRS in a helicopter was to INCREASE AIRSPEED, while decreasing power to the rotor system.
In contrast, the V-22 does have the same issues with a vertical velocity at or above 800fpm and airspeed below 40 KCAS. However, the difference between helicopters and the V-22 lies in both crew alerting of VRS and the procedure to fly out of it. The procedure for the V-22 to fly out of VRS involves “beeping” the nacelles forward for two seconds. What is unique for the V-22 is that power does not need to be decreased and the aircraft attitude does not need to change. We can in essence, fly out of VRS, with out trading anything for it. .
The V-22 has four tools for combating VRS; extensive flight testing following the 2000 crash, training, visual cues of the dynamic VRS threshold and finally an audible warning of SINK RATE. At 40 KIAS and above the limit is 800 fpm. Additionally, with an air data system failure the crew warning system defaults to 800 fpm as the VRS limit. At airspeeds above 40 KCAS, the VRS threshold is dynamic with the limit increasing with airspeed, topping out at 1100fpm. The absolute edge of the VRS envelope for the V-22 has been determined to be 1800fpm.
All of this said, I fly on the CV-22 at least three times a week. Having been doing so for three years I am very comfortable with the safety factor of the V-22. Additionally, I believe that for the both USMC and the USAF the V-22 will meet and exceed expectations that we currently have for the aircraft.
rjsquirrel couldn’t be more wrong. All helicopters have a similar power settling limit related to VRS. I’ve not only flown them for over two decades, but I’ve conducted flight tests on them, graduated from USNTPS, and like Tom (who I know) am a member of SETP. The average restriction is 800 FPM below 40 knots. Use you RFM/NATOPS/-10 for individual discussion on the machine you happen to be guiding through the air on any given day.
rjsquirrel said
“The typical helicopter has no such restriction on its rate of descent at low speeds, and would certainly not flip upside down should a pilot chose to descend faster.“
…I don’t know what you fly but for the past 15 years of flying RW aircraft I’ve been taught to stay out of VRS. Having spent 14 of those years flying USMC helicopters I can tell you that EVERY USMC helicopter NATOPS limits them to 40kts, 800 fpm rate of descent in order to stay out of VRS, so no, the V-22 is no different. Yes most helicopters can exceed that limit, just as the V-22 can, it is a conservative number which doesn’t affect your approach into a landing zone. A well executed tactical approach won’t have you doing 20 kts and a 1000 fpm rate of descent close to the ground and most approaches into a hot LZ aren’t very vertical in nature.
At altitude VRS is recoverable by BOTH a TR and helicopters. Close to the ground getting into VRS in either platform can be deadly. That’s why you train, plan and execute.
As far as maneuverablilty is concerned, I’m sure you think you’re laying on the g’s at slow speed but you’re lucky to get 1.3 g and that’s with very large control displacements.
It is always sad to see technolgy overwhelm common sense. There are so many reasons to NOT go forward with V-22 they could probably fill a few college blue books.
From its lack of ability to protect itself, to its cost, to its questionable ability to survive a combat environment, the stresses of combat on its components, its maintenance cost/component costs and a litany of other problems, it is difficult to imagine the 22 becoming a successful combat aircraft.
Why would DOD want to develop a multi-billion dollar aircraft that will be utilized for troop insertion/extraction, med-evacs, and resupply missions? Granted, its speed is an advantage but it appears to be the only advantage the 22 has over a standard helicopter. The claimed altitude advantage was a canard as it does not have a pressurized cabin. Consequently, its speed advantage and claimed reduced fuel operating expenses are out the window.
I certainly do not want to anger anyone but sometimes, people involved in developing a widget become so determined, so adamant they lose sight of what they are actually trying to accomplish and consequently begin to ignore relevant evidence. I hope this is not the case and I do hope the 22 does succeed…God knows, enough Marines have paid the price to get this bird in the air. Let’s all hope the disciples of the 22 are correct and we doubters wind up with egg on our faces.
S/F Gordon
You guys are not seeing the big picture. The political winds are shifting. Massive budget deficits in conjunction with ever increasing entitlement expenditures will soon have a crushing effect on defense bugets. Forget VRS. Forget the fact that the H46 has done a fantastic job in Iraq (even if senior Marine leadership has it flying around at unacceptably high altitudes making it vulnerable to MANPADS). Forget the fact that H-53 operations are restricted in the Sunni Triangle do to its vulnerability to MANPADS (makes me wonder what the V-22 will be relegated to). The simple fight for scarce defense dollars will kill the V-22. Someday when we are starving to feed that beast, the Marines will awaken to a catastrophic mistake. So argue over VRS if you like. The almighty dollar killing the V-22 will be the best thing that ever happens to the Marines.