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An Ingenious Blend of Airplane and Helicopter
November 11, 2009 1:28 PM   Subscribe

What does an aircraft company do when military contracts dry up? Fairey’s answer was to reinvent the helicopter and revolutionize the short-haul airline industry. After 15 years of effort, its unique project, the Rotodyne, came within an inch of achieving that goal. The Fairey Rotodyne, which first took to the air more than 50 years ago, was billed as the world's first vertical take-off commercial passenger aircraft. Fairey talked up expressions of interest from BEA in the UK, New York Airways and the US Army, but the crucial launch order never came. British government policy to rationalize the industry saw the end of the Rotodyne and Fairey as an airframe maker in 1962.
posted by veedubya (27 comments total) 8 users marked this as a favorite

 
That's a really beautiful ugly aircraft.
posted by WPW at 1:37 PM on November 11, 2009


That is awesome.

A question, though, for the flight-physics crowd. In case of a total engine failure, does there look to be enough wing surface area for a (relatively) safe glide-type landing? Or would it basically just sort of plummet? I realize that the same consideration probably applies to regular helicopters, but then again, not as many folks travel that way on a daily basis...
posted by jquinby at 1:43 PM on November 11, 2009


As an amateur WWII historian, static modeller, and former hobby shop manager/owner, the Fairey Rotodyne was one of the first plastic kits I ever assembled.
Ugly as sin.
An the Airfix kit was (is) horrendous!
posted by Drasher at 1:46 PM on November 11, 2009


In case of a total engine failure, does there look to be enough wing surface area for a (relatively) safe glide-type landing?

I imagine a standard Auto rotate helicopter landing would work, but that would go directly against having any lift that the stubby wings produced, but I'd suspect the glide path of that thing would be, as you suspect, close to 90 degrees without the main rotors...
posted by Brockles at 1:49 PM on November 11, 2009


It's awesome!
But I do question the wisdom of equipping a passenger aircraft with a nose-mounted 37mm cannon.
That calibre of gun will just generate too much recoil - an array of heavy machine guns would be much more effective.
posted by Flashman at 1:50 PM on November 11, 2009


A question, though, for the flight-physics crowd. In case of a total engine failure, does there look to be enough wing surface area for a (relatively) safe glide-type landing? Or would it basically just sort of plummet? I realize that the same consideration probably applies to regular helicopters, but then again, not as many folks travel that way on a daily basis...

Assuming it's a true helicopter, and that's it's high enough in the air, the rotors would autogyrate backwards as the craft descended. It would significantly slow the fall, but the landing would still be very rough.
posted by Benny Andajetz at 1:51 PM on November 11, 2009 [1 favorite]


Assuming it's a true helicopter, and that's it's high enough in the air, the rotors would autogyrate backwards as the craft descended. It would significantly slow the fall, but the landing would still be very rough.

Designed correctly, you'd have an envelope in which you could survive the crash, which is strangely better the higher up you are. You can be low enough for the landing gear to brace the impact by itself, or you can be high enough to allow for a slowed descent. But you can't be in the middle, where autorotation wouldn't get enough rotational speed to provide enough lift to slow your descent speed to a survivable range.

Each helicopter has a graph that shows this, for its particular weight and autorotation properties, that pilots are supposed to commit to memory, so in the case where failure is about to happen, they can try to either gain or lose altitude as needed.
posted by Cool Papa Bell at 2:02 PM on November 11, 2009 [3 favorites]


So it's essentially an autogyro with VTOL capability? That is, it's an autogyro when in full flight, with an unpowered rotor providing lift in the usual autogyro way; and a helicopter when in VTOL mode, the lift rotor getting power more directly from the engines. Brilliant in theory, it's the transitions between the flight modes that make me a little nervous.
posted by George_Spiggott at 2:20 PM on November 11, 2009


Watch the videos, guys. The thing produces the majority of its lift through autorotation of the helicopter blades. The stubby wings are a nod towards stability & steerability and do provide some lift, but not all of it. In the case of main plant failure during cruise forward flight, the thing will simply glide down slowly, as any autogyro will. I imagine it would be quite manoueverable doing so. Main plant failure during STOL would be, as others have said, sort of splatty if the rotors weren't up to speed -- but given that they're never motionless during flight and must support its weight (and thus be up to speed) in order for it to be off the ground at all, I imagine the area of the "splat failure modes" doesn't overlap too much with the practical flight envelope.

Autogyros are one of the safest aircraft going; the only thing that can make one fall down is if the rotors just plain fall off (or if you do something stupid like filp it).

It's UGLY, yeah, but an awesome machine.
posted by seanmpuckett at 2:23 PM on November 11, 2009 [1 favorite]


The wings aren't that much stubbier than a Shorts 330

You could even use this thing for similar terrifying commuter jumps between minor airports.
posted by poe at 2:42 PM on November 11, 2009


But you can't be in the middle, where autorotation wouldn't get enough rotational speed to provide enough lift to slow your descent speed to a survivable range.

Yeah, helicopter pilots refer to this as the "deadman's zone". The amazing thing is that most helicopter rescue operations operate almost solely in that zone.
posted by Benny Andajetz at 2:49 PM on November 11, 2009


The V22 is roughly the same size but outperforms the Rotodyne in most areas. A variant could be developed to carry more passengers, even. The safety record is spotty, however.
posted by Burhanistan at 2:53 PM on November 11, 2009


Just asking, do any of you know why it would be desirable to have a passenger aircraft that took off and landed vertically? Would it be to get rid of the need for runways? If so, any likelihood one of us non military types will some day get a ride home for the holidays in an Osprey or something like it?
posted by bearwife at 3:10 PM on November 11, 2009


For all you technical illustrators:
Rotodyne cutaway illustration 1.
Rotodyne cutaway illustration 2.
Concept sketch by member of the flight development team.
posted by Kabanos at 3:12 PM on November 11, 2009


I like autogyros.
posted by exogenous at 3:15 PM on November 11, 2009


Would it be to get rid of the need for runways?

Yes. You could have a lot more of these everywhere.
posted by Cool Papa Bell at 3:36 PM on November 11, 2009


Man, this future we are living in was supposed to be awesome. I'm disappointed it is merely very cool.
posted by chairface at 3:45 PM on November 11, 2009


Outside of London -> Paris and maybe a handful of cities in New England, this really isn't viable. Most cities in America saw their boom at the cusp of commercial airline travel and are well suited for the current car -> highway -> plane infrastructure. You're never going to be able to compete with that economically.
posted by geoff. at 4:15 PM on November 11, 2009


If this machine were in our future, I'd be worried that we were sucking too much lifeforce from the planet to make Materia. It's bad enough with that lighter than air thing buzzing about the Bay Area now adays... yeah I'm looking at you Airship Ventures zeppelin! Grow some wings like a proper air transport!

Ever get a longing for a universe that never was? That first illustration in Kabanos comment makes me feel that way for some reason. Maybe because I associate stuff like that with the Star Wars ship cutouts? I don't know.
posted by Mister Cheese at 4:23 PM on November 11, 2009


That thing looks positively Soviet.
posted by dhartung at 5:16 PM on November 11, 2009


If you haven't clicked the link, you're probably thinking, How ugly could it really be? Ten kinds of ugly, that's how ugly.

Now if you'll excuse me, I have to go bleach my eyes.
posted by Civil_Disobedient at 5:50 PM on November 11, 2009


the rotors would autogyrate backwards as the craft descended.

The rotors do not turn backwards during auto-rotation -- they will continue to rotate in the normal direction. The flow of air is "reversed" in that it is now coming from below the bottom of the disc rather than being sucked from the top.

To enter auto-rotation in a conventional helicopter, however, a collective control is required to have negative pitch (or angle of attack, which is close enough to pitch). Gyrocopters typically have very low angles of attack for the blades and use their elevator control surfaces to pull out of autorotation (translating airspeed for altitude), while a conventional rotorcraft will use its collective to translate rotor inertia into lift.

The original Rotodyne prototype did not have a manual collective, but instead varied blade pitch proportional to shaft torque. The second prototype was built with tip-jets, which is an even weirder control setup. Neither of them would have very good autorotation characteristics (likely survivable, but with high risk of damage to the airframe), but the FB-1 was capable of single engine hover so the autorotation requirements would be lessened.
posted by autopilot at 6:06 PM on November 11, 2009


Designed correctly, you'd have an envelope in which you could survive the crash, which is strangely better the higher up you are. You can be low enough for the landing gear to brace the impact by itself, or you can be high enough to allow for a slowed descent. But you can't be in the middle, where autorotation wouldn't get enough rotational speed to provide enough lift to slow your descent speed to a survivable range.

Just to clarify the Height-Velocity (HV) curve, there are two regions of danger in most conventional rotorcraft. There is a low-altitude, high-speed section that is dangerous (too fast to slow down in the altitude available), and mid-altitude, low-speed section in which there is insufficient altitude to build up enough forward airspeed to maintain autorotation at a safe descent rate.

The airflow is not just straight up through the rotor disk, but also created through forward airspeed. Typical light civilian helicopters need 60 kts or so of forward speed to have a descent rate of less than 1500 fpm while maintaining a main rotor RPM of 100-105%. As the aircraft approach the ground, the cyclic pulled back to "flare" and translate the airspeed into rotor inertia, then the collective is increased to translate that inertia into lift to slow the descent rate to zero just as the skids touch down.

(With sufficient main rotor inertia, it is possible to eliminate the mid-altitude section of the HV curve. But the heavier rotors then require hydraulics, which then make for a much larger aircraft)

(And with some light aircraft, it is possible for the two "no-go" regions of the HV curve to intersect at some density altitudes. This indicates that an engine failure during climbout could be fatal...)
posted by autopilot at 6:16 PM on November 11, 2009 [3 favorites]


There is a low-altitude, high-speed section that is dangerous (too fast to slow down in the altitude available)

That's interesting. I guess if you slowed down by climbing, you're screwed. But what if you had a mile of runway in front of you: couldn't you slow down while keeping in ground effect, and then land? I realize the mile of extra runway is not a realistic scenario, but that section of the graph just seems a little odd to me coming from a fixed-wing background.
posted by exogenous at 9:10 PM on November 11, 2009


Autorotational aerodynamics are tricky at best, but here's my understanding.

Upon entering the autorotation, you have three areas of the rotor disk: stalled, driving, and driven. The stalled area is due to the large angle of attack (due to blade twist) and low linear velocities near the blade roots. The driven area is near the blade tips and mostly contributes drag and controllability to the rotor system due to the high linear velocities. The driving area is in between the stalled and driven areas, and keeps the main rotor turning. It does so in the same manner that a leaf will fall slower to the ground if it acts like an airfoil and spins.

I've never seen a negative pitch while autorotating, however - not even a flat pitch unless I was calibrating the rotor system. Some pitch is required to keep the rotor system near 100%.

As for the low-altitude, high-velocity portion of the H-V diagram, two factors come into play for that portion: reaction time and rotor RPM. When going that fast, you may not have the reaction time to enter an auto. Additionally, at extremes of temperature, speed and/or weight, you may actually not have the engine power to fly at 100% RPM, resulting in a decrease in it with possible effects on the tail rotor (if applicable) or even catastrophic damage to the rotors due to extremely low RPM.
posted by squorch at 6:24 AM on November 12, 2009


@autopilot: As far as I know, jet tips were just a way of powering the rotor, nothing to do with control surfaces. And why does jet tip mean poor auto-rotation characteristics?

@squorch: Is auto-rotation not also partly due to combination of cyclic and collective creating negative pitch? IE. If you are at zero degrees with the collective, then pulling back on the cyclic will create a negative pitch on the rear part of the rotor disc. It's never been clear to me how much, if any, this plays a role in most auto-rotations.
posted by Soupisgoodfood at 1:20 AM on November 14, 2009


Just wanted to step back in and express my thanks to the propeller-heads (ha!) for the discussion. This is fascinating stuff. All the same, I believe I'll be skipping the helicopter rides.
posted by jquinby at 6:17 PM on November 14, 2009


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