Studies In Ornithopters

weileong writes "This should be of especial interest to fans of Frank Herbert's Dune (or maybe only those who preferred House Atreides) - a genuine, flexible, flapping-capable winged aircraft (by which I don't mean passenger-carrying. Yet.) has been produced by the University of Toronto's Institute for Aerospace Studies and SRI International (Washington Post article, free reg required). Advantages include everything from low speed control to efficiency. Once these things really hit "real world" usage, the V-22 Osprey really HAS no reason to exist (and all the army personnel at risk of dying in one should rejoice)."

Comments

Wrong branch

[benj_e]

It's the Marines that use the Osprey, not the Army.

The V22?

[Realistic_Dragon]

No need for the V22? Hardly.

The V22 is _finally_ getting to the mature design stage. They removed the problems that killed people (mostly, no a/c is perfect) like the inability to handle the loss of ground effect under one rotor.

Now they have an a/c which can not only take off vertically (or very sharply with high load), fly at 400mph and carry a ton of stuff. For it's role it beats the shit out of any helicopter (fast enough to do the job more fuel efficient, heavier loads,) and and cargo plane (no need for a JATO unit, can't run a C5 off a carrier).

This new technology is (like the tilt rotor concept was) unproven, and requires a complex set of engineering decisions to be made to get it to fly safley (like the tilt rotor). In 20 years, with a few deaths, it might be great - but the tilt rotor is here now.

FWIW there is now a commercial version of the V22 in prototype, the BA commuter aircraft. Small enough to land on helipads, but fast enough for intercity (and in Europe) international work. There have also been plans for a gunship version of the V22, with a massive rotary cannon and the ability to fly very slow it's even going to make the A-10 look a bit lightweight :oD

Re:The V22?

[bbaskin]

The cause of the Arizona accident that killed 19 Marines was a form of vortex ring state that formed around one proprotor that caused an imbalance of lift from one side to the other. The ship rolled sharply and nosed in. All helos are susceptible to VRS and it forms when you are travelling down too fast in combination with low forward airspeed. At the time, the Osprey had a vertical descent rate limit of 800 ft/min at low forward airspeeds. The ship in question was descending at ~2100 ft/min, almost three times the recommended rate. Pilot error. The other crash later that year was due to a combination of hydraulic and software failures that reduced the redundancy of some control systems.

The VRS has now been shown to not be a symptom of tiltrotors only, its boundaries have been mapped out, warning sensors have been installed, and VRS exit strategies developed. In a helo, you just gain some forward speed or sideward speed. In a tiltrotor you have the additional option of tilting the nacelles a few degrees. In addition, plenty of improvements have been made to all sorts of subsystems and the computers have been through the cleaners to check for more bugs.

The commuter ship, the BA609, will also benefit from these studies. It's target certification date is late 2007. That date is so distance for a variety of reasons, most of them non-technical.

Tiltrotors are complicated, but I've flown the BA609 sim, and it's by far the easiest VTOL aircraft I've flown and the capabilities are impressive.

Re:The V22?

[Martin Blank]

For it's role it beats the shit out of any helicopter (fast enough to do the job more fuel efficient, heavier loads,) and and cargo plane (no need for a JATO unit, can't run a C5 off a carrier).

First point correct, second point misses the mark. The C-5 (and the C-17 and C-141) are entirely different classes of aircraft than the V-22. The V-22 is designed more to set troops into action like a conventional helicopter such as the Black Hawk does, though I believe it's possible to parachute from them. The other three are primarily cargo aircraft with secondary airborne capacity. Their ranges also beat out the Osprey's.

There have also been plans for a gunship version of the V22, with a massive rotary cannon and the ability to fly very slow it's even going to make the A-10 look a bit lightweight

That's also going to require putting a lot of armor onto an Osprey, and I don't know if it can handle that. Your performance statistics seem to be off of the real mark, judging by the Navy's version of things. With a max speed of only 275mph, and what looks to be a fairly small difference between the empty and various max-takeoff weights, I don't see this becoming a challenge to the A-10 anytime soon, since that plane not only carries the GAU-8/A (with its weight of 281kg plus a kilo for every round), but also up to 7250kg of payload underneath it. I've seen pictures of them with a bevy of Mavericks slung underneath, and it's a menacing sight.

Getting back to the original story topic, though, I can't see yet how this idea would translate into a usable large aircraft as the submitter is hoping. The forces are significantly higher at the wingtip than at the root which is going to stress the wings in an increasing fashion the longer they are, not to mention the material fatigue from a material that is constantly changing directions. I can see this used as they envision now, with small drones or perhaps as a new ultralight, but I can't see how the increased lift would be generated efficiently for a replacement to even a small troop transport like the Osprey.

Re:No pictures??

[Anonymous Coward]

Click a bit further ;-) home page and movie can be found here.

related article with picture

[BoosterToad]

This article has a picture of the ornithopter:

Mentor Micro-Air Vehicle

Wow, it looks weird.

V-22

[Ribald]

The Osprey's had trouble for a reason--it's horribly complex, and there's never been an aircraft like it before (outside the X-planes, that is). An aircraft that transitions from a conventional airplane to a would-be helicopter has a lot of control issues to work out.

The poster's theory that the ornithopter will somehow make this superfluous is a bit ludicrous. An ornithopter large enough to carry troops will likely be even more complex. Taking the output from a turbine engine and gearing it down to spin a prop is trivial--we've been doing it for decades. Even with the complicated transmissions and crosslinks and control systems on the V-22, it's still basically just a combinatinon and evolution of previous aircraft.

Taking output from a turbine and translating it to drive a piston is another matter. It can be done, of course, but entails much higher losses. The researcher says enormous amounts of energy are required for the small one, and it's, um, small.

The strength of the parts is another issue. Making wings and linkages that will drive them is going to be a challenge. As will performance after an engine failure.

Don't get me wrong, this is quite an achievement. For the unmanned aerial vehicle trade. I don't think we'll have the technology to make a troop transport, or even a one-man aircraft, out of an ornithopter for a long time.

Trying to foist this as a replacement for the Osprey is a bit ludicrous. Replacing a complicated aircraft with a more complicated one does not lend itself to safety or reliability, right out of the box.

Absurd

[SuperBanana]

No need for the V22? Hardly. The V22 is _finally_ getting to the mature design stage. They removed the problems that killed people (mostly, no a/c is perfect) like the inability to handle the loss of ground effect under one rotor.

Your argument is all and well, except that aircraft ARE virtually perfect- it's the ones that are NOT perfect that we hear about. Second, when an aircraft is NOT perfect, you're supposed to fix it. The contractor involved and the armed forces instead outright lied through their teeth and ignored the problems while soldiers continued to die. Lastly, the problems were far more extensive than just one issue with ground effect.

There have also been plans for a gunship version of the V22, with a massive rotary cannon and the ability to fly very slow it's even going to make the A-10 look a bit lightweight

One of the warthog's best features is its heavy armour- some jokingly call it the 'flying bathtub' because of the cockpit reenforcement. I believe most hydraulic and electrical systems are also heavily armoured. It takes more than just a plane to make an effective way to shoot at people. Nevermind that the V22 looks to be completely intolerant of failure in either engine- and as any pilot knows, twin engined planes have twice as many engine failures because, surprise, you've got two of 'em :-) I'd be curious to hear your thoughts on how someone would eject from the V22 without standing a good chance of being sliced to pieces.

As for the original poster's comment that this will replace the V22- I hardly see how. Ever notice that 'Ornithopters' in nature don't really exist above a dozen pounds or so? Sure, we had some big flying dinosaurs a while back, but even those weren't nearly big enough to weigh as much as a small plane.

Re:Absurd

[bbaskin]

The V-22 or any other Bell twin engined tiltrotor to date can fly on one engine. The two rotors are cross shafted together so that both rotors remain in synch and powered at all times. A quad tiltrotor has been considered and that aircraft (C-130 sized) would have all four engines and rotors cross-shafted so that several engines could be lost without losing the aircraft.

That said, the V-22 will not be a A-10 replacement. That simply makes no sense. A gunship version has been proposed but it's more along the lines of an AC-130 gunship. Orbit higher and a little futher away from the targets. More of an area weapon for softer targets not getting down and dirty with heavy armor. The 'Hog is tops for that.

Early test V-22s did have ejection seats. The rotors do not pass above the cockpit so there is a small path in VTOL mode and obviously a larger path in airplane mode for a safe ejection. Current production ships no longer carry this feature and like any other cargo ship, there were never plans to eject all the passengers.

More Ornithopter info...

[c_king]

ornithopter.org

Re:Assumption is the mother of all f**k-ups...

[WIAKywbfatw]

VTOL planes always seem to be plenty risky - the Harriers are also quite widely known for killing their pilots, aren't they?

Err, no. Harriers have an excellent safety record and an even better combat one. During the Falklands War, British pilots of the Royal Air Force and Royal Navy lost none of their Harriers to enemy aircraft (one was shot down by ground-based anti-aircraft fire) whilst managing to shoot down twenty Argentine aircraft - this despite the fact that the subsonic Harriers were matched up against supersonic opponents.

VIFFing (vectoring in forward flight), a strategy limited to the Harrier and other VTOL aircraft capable of redirecting their thrust mid-flight, is a favourite dog fight strategy of Harrier pilots. One minute you're on his tail, lining him up for a shot, then next minute the Harrier's no longer in front of you because its pilot has "jumped" vertically. And, by the time you've worked it all out, he's dropped back down behind you and is about to missile lock your aircraft.

Next time, do your research.

Re:Assumption is the mother of all f**k-ups...

[bluntmanspam]

OK, how bout next time you do your research, too. A quick google search turned up this story from the LA Times (mirror here)

Quote from the story:

The lifetime accident rate for the Marines' AV-8B is 11.44 per 100,000 hours of flight, well over the combined rates for other attack and fighter planes flown during those years by the Marines, the Navy and the Air Force.

And before you go off about untrained or unskilled American pilots again, check the author's Q&A here, where he points out this:

The AV-8B had 12 major accidents per 100,000 hours flown during the decade. The three similar Harrier models flown by the Royal Air Force during that time had accident rates ranging from 12 to 19 when the U.S military standard is applied.

and this:

Because there are fewer Harriers in Great Britain, and they fly fewer hours, they've had fewer crashes and fatalities.

The Harrier is not a safe aircraft. The RAF knows it, that is why they are part of the Joint Strike Fighter program. That program aims to create a VTOL aircraft without the problems of the Harrier.

Re:Assumption is the mother of all f**k-ups...

[weileong]

Hi, read this article some time back:

Harriers - the Widowmaker (from the LA Times)

Some excerpts:

Far From Battlefield, Marines Lose One-Third of Harrier Fleet
The corps, pursuing its long-held dream of a unique flying force, pays a heavy price: 45 of its elite officers killed.

Many of the Harrier's ailments can be traced directly to its innovative vertical-thrust technology. But despite the investment of tax dollars, aircraft and pilots' lives, there is little evidence that the Harrier's noncombat deaths have been redeemed in any significant way on the battlefield

In the Persian Gulf War in 1991, the hot thrust-producing nozzles in the heart of the fuselage -- the devices that allow the Harrier to rise and balance in the air -- made the plane a magnet for heat-seeking missiles. Its loss rate was more than double that of the war's other leading U.S. combat jets. Five Harriers were shot down and two pilots died.

"It's the most vulnerable plane that's in service now," said Franklin C. "Chuck" Spinney, who evaluates tactical aircraft for the Pentagon.

Next time, do your research

I actually did, you'd be pleased to know.

Re:Material Fatigue ?

[G4from128k]

Yes and no. Fatigue WAS a major issue in the early years of aviation, but now it is well understood. As long as you have a proper understanding of the material's properties and the stresses induced by the application, then you can design to forestall or eliminate fatigue cracking. Some materials (certain types of steel) actually have infinite fatigue resistance as long as the stresses are below a critical threshold. Stress cracks are not an issue where one can employ a combination of good design, good "life" testing, good operator training, and good inspection/maintenance procedures. I'm not saying that bad things can't happen, just that they are preventable.