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11/22/2017 10:05:29 PM
Posted: 9/17/2004 7:09:57 PM EST
I know how much you guys like the AH-56.

AH-56A 66-08827 First AH-56A built.

It is going to be restored and placed on the new gate to the polk airfield.
Right where very few people will ever be able to see it.
Typical.














Link Posted: 9/17/2004 8:29:39 PM EST
WOW ! That thing's cool, When did we come up with something like that ? Interesting tail rotor design It ever see actual service ? Sure is a big bastard !
Link Posted: 9/17/2004 8:34:44 PM EST
[Last Edit: 9/17/2004 8:35:24 PM EST by Winston_Wolf]
... I know enough that if the Cheyenne was given the chance in her days, it would put shame to any rotorcraft in our inventory

... I'll also go so far as to say that if given 25 years to mature, there probably would not be a V22 Osprey program now either
Link Posted: 9/17/2004 8:35:22 PM EST

Originally Posted By JB69:
WOW ! That thing's cool, When did we come up with something like that ? Interesting tail rotor design It ever see actual service ? Sure is a big bastard !



www.vstol.org/wheel/VSTOLWheel/LockheedAH-56.htm

Lockheed research into compound rigid rotor helicopters began in the early 1960s using the XH-51. In 1966, Lockheed's design for an operational attack helicopter, the AH-56 Cheyenne, won the contract to build the US Army's Advanced Aerial Fire Support System (AAFSS). The Cheyenne had a 3,435 shp General Electric T64-GE-16 turboshaft engine that powered a rigid 50 ft four-bladed rotor, as well as a 10 ft three-bladed pusher propeller and a four-bladed anti-torque rotor on the tail. In horizontal flight, almost the entire engine output is used to drive the propeller. The AH-56 weighed 12,000 lb empty, had a 55 ft long fuselage and a 27 ft wingspan. Maximum vertical take-off weight was 22,000 lb, but a short take-off could be made at 28,000 lb. First flight was on 21 September 1967. A maximum speed of 277 mph was reached. The third of ten prototypes crashed on 12 March 1969 when the rotor impacted the front and rear fuselage, killing the pilot. The AH-56 was highly agile and a very capable weapon system, but development was halted in 1972, due to defense cutbacks. A production order of 375 AH-56s had been approved in 1968, but canceled the next year, also as a result of budget cuts.

Link Posted: 9/17/2004 9:30:28 PM EST
A gyrocopter...

Hmm... Probably a whole lot faster than most helos....

And what does this have to do with the V-22 (which, everyone keeps sandbagging simply because it has had some fatalities in testing (just like every other 'advanced' or 'innovative' aircraft design, including the F117, XB-70 and Harrier)???

IMHO, though, cancelling the V-22 due to testing fatalities is just as bad as cancelling the XB-70 over the same issue...
Link Posted: 9/17/2004 9:45:52 PM EST

Originally Posted By Dave_A:
A gyrocopter...

Hmm... Probably a whole lot faster than most helos....

And what does this have to do with the V-22 (which, everyone keeps sandbagging simply because it has had some fatalities in testing (just like every other 'advanced' or 'innovative' aircraft design, including the F117, XB-70 and Harrier)???

IMHO, though, cancelling the V-22 due to testing fatalities is just as bad as cancelling the XB-70 over the same issue...




... You a talkin' to me? I say, a you a talkin' to me?

… If you were, my point was this.

… If given the chance, and CRAD funded projects throughout a 25-30 year maturity, the Cheyenne and variants could meet nearly any role currently within the envelop of the Osprey’s mission. Don’t get me wrong, the V-22 pays some of my bills, I love the aircraft. But the V-22 is an expensive platform for VSTOL and transition flight. We could have gotten 4 to 5 as many pusher-rotorcraft for the same cost of the V-22 system.

... No, we could not achieve the 175 knots VNE of the Osprey but C3 battlefield managers would be able to accommodate the relatively low difference between the two.

... But hey, what the fuck do I know?
Link Posted: 9/17/2004 10:08:55 PM EST
Somehow, that belly camera fairing don't look milspec....
Link Posted: 9/17/2004 10:23:34 PM EST
Damn, what a bitchin machine! That thing looks like a cross between the Huey, Apache, Cobra and an Mi-24 Hind! Like so many other impressive pieces of military equipment, too bad it never entered service.
Link Posted: 9/17/2004 10:35:55 PM EST
So what was so special about this thing? It just looks like a pre-Apache to me?
Link Posted: 9/18/2004 2:23:41 AM EST

Originally Posted By Dave_A:
A gyrocopter...

Hmm... Probably a whole lot faster than most helos....




Not a gyrocopter. It's a compound helicopter - so named because it is a mix of helo and fixed wing. In low speed flight the main rotor does the lifting work. At higher airspeeds the pusher prop (behind the tail rotor) provides an increasing share of propulsion and the short wings provide a large percentage of lift. Also, since conventional aircraft propulsion is more efficient than rotary wing, the aircraft will typically have increased range.

This reduces aerodynamic loading on the main rotor which means that the main rotor blades can have a reduced blade angle of attack, which increases the airspeed at which retreating blade stall occurs. Retreating blade stall (when the forward airspeed of the aircraft is high enough that lift is not produced on the blade rotating toward the rear of the aircraft) is a major factor limiting helicopter speed.

The problem is if the load is reduced too much on the main rotor, the blades are free to flap excessively. This flap, if not controlled, may cause fatigue failure to occur in the rotor head or cause the blades to strike the fuselage. Either incident will have catastrophic results. Advanced materials and designs can mitigate the problem.

An additional problem is that the wings that provide lift in high speed flight are detrimental to performance at lower airspeeds because the main rotor wash hits them, reducing the lift provided by the main rotor.

The Navy has done some experimenting with compound helicopters fairly recently as well:



IIRC, the degraded hover/low airspeed performance was too much to trade off for increased range/speed. Also, the compound helo wouldn't fit in the hangars on air-capable ships. Here is some good reading on compound helicopters:

www.geocities.com/tacticalstudiesgroup/piaseckivtdp.htm
Link Posted: 9/18/2004 3:12:40 AM EST
It's not a gyrocopter, it's a helicopter with a pusher prop instead of a tail rotor.



Originally Posted By Dave_A:
A gyrocopter...

Link Posted: 9/18/2004 3:17:14 AM EST
Link Posted: 9/18/2004 3:33:23 AM EST
The Cheyenne rotor system
The Cheyenne had a most remarkable (if not the most remarakable) rotor system. The techniques employed for tilting the rotor were (and remain) unlike anything ever devised.
If you look at the pictures you will see what amounts to a simple gyroscope just above the rotor. This gyro being the 4 'weighted arms' that were a single unit mounted on a gimbal and which spun with the rotor. This gyro was used for two purposes :-

To provide a stabilizing mechanism (not dissimilar the the famous 'bell-bar' gyro)
To directly change the angle-of-attack of the (rigid) rotor blades. The gyro had direct links to the blade pitch horns (these can be seen in some of the pics). So the *only* way to change pitch of the rotor blades was by causing the upper gyro-gimbal to tilt in what ever way it could be made to tilt (or in moving the gyro-gimbal vertically if collective pitch changes were commanded).
Inside the body of the helicopter was the equivilent of a 'swash-plate', the inner ring had 4 control rods that ran up the inside of the rotor shaft - in the picture you will notice that the rotor shaft is short and quite thick - the control rods were directly coupled to the gimbal mounted gyro.
To explain this part of the control system, picture a conventional style swash-plate at the bottom of the rotor shaft. It has an inner and outer ring just like any swash-plate does. At the top of the rotor shaft, picture the gyro-gimbal. The gyro-gimbal in this example resembles a swash-plate in that it can tilt in any direction but, unlike the swash-plate, it has no seperate inner & outer rings that turn independantly. So the gyro-gimbal can tilt but will only spin with the main rotor shaft.

When spinning, the weighted arms become a gyro and of course this gimbal will now resist any tilting force at the point it is applied but will tilt 90 degrees further round in the direction of rotation, and this tilting will be in proportion to the continued force being applied at the original point.

So while the rotor was not spinning, if you were to tilt the lower swash-unit the gyro at the top would tilt in exactly the same directions, it would track the lower swash-plate exactly, but while the rotor was spinning, gyroscopic force would take over and prevent tilting both the upper gyro-gimbal and the lower swash-plate coupled to it, at the point the tilting force was being applied.

This is due to the tilting force being resisted by gyroscopic-precession from the upper gyro-gimbal. Of course this resistance is not there when the rotor (& thus gyro-gimbal) is not spinning.

The amazing part of this whole assembly then is what happened with the lower-swash unit and the upper gyro-gimbal it was coupled to, when the rotor was spinning, and also what actually happened when a tilting moment was applied to the lower swash-plate. The bit we are missing to this point is how the internal tilting control rods that go from the pilot's servos to the lower swash-plate outer ring were physically connected.

Remembering that there are 4 control rods inside the rotor shaft linking the inner race of the lower swash-plate to the upper gyro-gimbal, we now add 4 more control rods, but these go from from the pilot's cyclic servos to the lower swash-plate outer-ring and are connected to it with spring loaded rods. Because of the springs, each pair of these cyclic servo control rods could move against the swash-plate outer ring and and apply a force without the swash-plate having to tilt at the point the spring pressure was applied.

While the swash-plate would not actually tilt at the points the force was applied, the force or spring pressure was still transmitted up the rotor-shaft control rods to the gyro-gimbal at the top which was of course providing powerful resistance (due to gyroscopic-precession) to the applied force.

Being a gyro, the gyro-gimbal would tilt 90 degrees further round in rotation. So the gyro-gimbal at the top precesses and then because of the direct links back down to the lower swash-plate unit, the swash-plate unit would then be forced to tilt in the same direction as the upper gyro-gimbal and this was possible because the lower swash-plate could force itself against the springs on the spring loaded cyclic servo control rods.

Also the upper gyro-gimbal's links to the rotor blade pitch horns, would cause the blades to change pitch. As it was a rigid rotor system and taking into account gyroscopic precession forces, the change in blade pitch would cause the whole craft to tilt 90 degress later than maximum (and minimum) pitch.

--------------------------------------------------------------------------------

So if we look again at the chain of events needed to tilt the craft forward it was ...

that the lower swash-plate would have a moment or 'force' applied at its' rear from the spring loaded rods connected from the pilot's servos to the outer, non-turning part of the lower swash-plate. Because the swash-plate was directly coupled to the upper gyro-gimbal, it would follow the behaviour of the upper gyro-gimbal and would not tilt with the applied force but resist it. The springs pushing on the swash-plate outer ring would compress as the pilot pushed the cyclic stick forward.

The spring pressure force would in turn be 'transmitted' up through the control rods that are inside the rotor-shaft and apply the force at the *back* of the upper gyro-gimbal. The upper gyro-gimbal then behaved like any gyro and precessed 90 degrees later and this of course caused the other pair of internal control rods in the rotor shaft to push down to the lower swash-unit at this later 90 degree position.

At this position the lower swash-plate would tilt. To do so the lower swash-plate outer ring would push against the springs on the other pair of servo to swash-plate control rods.

Restated, because the pilot's servo to swash-plate control rods were spring loaded, the springs that were 90 degrees further from where the original spring load or 'force' was being applied, would 'give' under the precessing push coming back down thru the internal rotor control rods from the upper gyro-gimbal unit.

The pilot, by pushing forward on the cyclic stick applies a spring loaded force up at 180 degrees & down at 0 degrees on the outer-ring of the lower swash-plate. The force is 'transmitted' up the rotor shaft through the control rods inside it that couple the swash-plate to the upper gyro-gimbal, the gyro-gimbal precesses and as it does so, does 2 things, one it directly tilits the rotor blades, and 2 pushes back down thru the control rods in the rotor shaft, to tilt the lower swash-plate in unison with itself. The lower swash-plate can tilt at this position because it is able to push against the other pair of spring loaded servo-to-swash control rods that are at the 90 & 270 degree positions.

Thus in final summary, the tilting push began 180 degrees before the actual tilt occurs as to tilt the helicopter forward, the pilot's cyclic servos apply a spring-loaded force at the 180 and 0 degree positions on the outer non-turning ring of the lower swash-plate. The swash-plate, because it is coupled to the upper gyro-gimbal physically tilts at the 90 degree (port) & 270 degree (starboard) positions. The upper gyro-gimbal which through gyroscopic precession, caused the 90/270 tilt, also applies maximum and minimum pitch to the rigid rotor blades at the 90 & 270 degree position - because the craft has a rigid rotor and due to the effects of gyroscopic precession, the whole craft tilts at the 0 degree (nose down) and 180 degree (tail-up) positions. The tilt of the craft is totally due to gyroscopic precession. This of course is not what tilts a rotor system that is not rigid, i.e. has free teetering blades.

Doug Marker Feb 2000 (with info obtained back in the 1970s from one of the original AH-56A designers)

http://www.balsta.tv/~a8030a/lockheedcheyenneah56a.htm
Link Posted: 9/18/2004 3:35:11 AM EST


Link Posted: 9/18/2004 4:00:08 AM EST

Originally Posted By Da_Bunny:
Somehow, that belly camera fairing don't look milspec....



I think it's the 40mm turret. The thing has two turrets, one in the nose for a mini-gun and one on the belly for a 40mm auto-GL. They could be operated independently, or together, by either crewman. You're right though, it's probably just some sheetmetal rigged up to resemble the original.

Ross
Link Posted: 9/18/2004 4:05:38 AM EST

Originally Posted By KA3B:
It's not a gyrocopter, it's a helicopter with a pusher prop instead of a tail rotor.



Originally Posted By Dave_A:
A gyrocopter...




Actually it has a tail-rotor as well and made a hell of a racket with both those things going in the ass-end.

A gyrocopter doesn't have a powered rotor. It relies on airflow throught he rotor to turn it, similar to an autorotational airflow. You have to maintain motion for the rotor to continue to turn. A gyrocopter can't hover. A helicopter (compound or otherwise) like the AH-56 has a powered rotor, in that the engine actually turns the rotor. It's also why a helicopter has a tailrotor (on a single rotor design). To counter-act the torque of the engine, which the gyrocopter doesn't have (engne torque, nor tailrotor).

Ross
Link Posted: 9/18/2004 4:13:03 AM EST
Thanks Ross.
Fumblefinger typing gets me every time.


Originally Posted By Ross:

Originally Posted By KA3B:
It's not a gyrocopter, it's a helicopter with a pusher prop instead of a tail rotor.



Actually it has a tail-rotor as well and made a hell of a racket with both those things going in the ass-end.

Ross

Link Posted: 9/18/2004 4:13:49 AM EST

Originally Posted By JB69:
WOW ! That thing's cool, When did we come up with something like that ? Interesting tail rotor design It ever see actual service ? Sure is a big bastard !



The size was a direct result of combat experience in Vietnam. Vietnam showed us that the helicopters needed to be bigger, to carry more ordnance, armor, systems, payload, cargo, people, etc. Hence the AH-56 and the AH-64 are close in size. It's because that's the size that works. It's also the reason that the Blackhawk is such a big sucker, and also why the Soviets went with such large aircraft like the Hind, etc. They learned the same thing.

Ross
Link Posted: 9/18/2004 4:24:28 AM EST

Originally Posted By Ross:

Originally Posted By Da_Bunny:
Somehow, that belly camera fairing don't look milspec....



I think it's the 40mm turret. The thing has two turrets, one in the nose for a mini-gun and one on the belly for a 40mm auto-GL. They could be operated independently, or together, by either crewman. You're right though, it's probably just some sheetmetal rigged up to resemble the original.

Ross



The belly turret was supposed to mount a 30mm cannon. The front, chin turret could mount a 40mm-GL or 7.62 mm minigun.
Link Posted: 9/18/2004 4:29:40 AM EST
Amazing Helicopter… watched a Discovery Channel documentary on it… it was way ahead of the curve in 1968… killed by the 'Bean Counters'.

ANdy
Link Posted: 9/18/2004 4:54:24 AM EST

Originally Posted By OLY-M4gery:

Originally Posted By Ross:

Originally Posted By Da_Bunny:
Somehow, that belly camera fairing don't look milspec....



I think it's the 40mm turret. The thing has two turrets, one in the nose for a mini-gun and one on the belly for a 40mm auto-GL. They could be operated independently, or together, by either crewman. You're right though, it's probably just some sheetmetal rigged up to resemble the original.

Ross



The belly turret was supposed to mount a 30mm cannon. The front, chin turret could mount a 40mm-GL or 7.62 mm minigun.



Gawdamnit! Now I'm going to have to look for a book on the Cheyene at the gunshow today just to get my facts correct

I've actually seen a couple of them. They have two now at Rucker. I saw Rucker's in the old museum, and back then you could climb all over the thing. Rucker's second one was up here at Ft Eustis, VA for a long time and was traded by the museum here to Rucker for some other junk, so both are down there being worked on. I've seen the one at Ft Campbell too, when I was in the 101st. Never saw the one at Polk though.

They're VERY interesting pieces, to say the least.

Ross
Link Posted: 9/18/2004 5:09:24 AM EST
If you know about Fort Polk I suppose you could find that hanger in picture #2.

From a friend:

"I was at Fort Polk today. Passing the storage hangar, noticed that these UH-1's were out in the sunshine.
Couldn't resist the Huey's. This lineup included three; UH-1H 70-16488 ex TX NG (rear) UH-1H 71-20326 ex Fort Polk, and UH-1B 61-0727 (front).






Originally Posted By Ross:
Never saw the one at Polk though.
Ross

Link Posted: 9/18/2004 7:31:56 AM EST
When I was stationed at Polk I saw the Cheyenne. It was at the museum in the back under a bunch of pine trees. They didn't make a big deal out of it. I thought it was a shame for this revolutionary aircraft to be relegated to where very few people will see it. It may not be seen by any more people at the airfield but at least it'll be in a place of honor.

jd1
Link Posted: 9/18/2004 7:39:05 AM EST
While I certainly appreciate the presence of "Gate Guards" and other outdoor static displays, I do not think that significant prototypes, like the YAH-56, should be displayed outdoors. It's hard on the airframe and exposed components, particularly in hostile environments like Ft. Polk have to offer.

However, since no one else has come forth with the effort and funding to restore this important aircraft and dsiplay it indoors, I suppose this is better than the thing getting cut up.

Neat helicopter.
Link Posted: 9/18/2004 5:41:09 PM EST
Not sure how much of this is true, but I understood that the Air Force threw a big fit over the AH 56 specifically because of the lift provided by the stubby wings. They were designed to provide significant lift to the aircraft enabling greater loads to be carried and more speed. When the AF became it's own branch, there was a specific agreement that the Army could not have armed fixed-wing aircraft. Hence, the reason the OV10's could not carry HE warhead rockets in VN. My understanding was that this agreement also helped kill the AH56 program.
Link Posted: 9/25/2004 5:59:55 PM EST
Great pics, fellas! Brings back a lot of memories.

IIRC, there was a Cheyenne display down at Mother Rucker. If you ever find yourself in MiddleOfNowhere Alabama, stop by and check out the Museum. Don't stop there, though. Drive over by the ATC school and check out some of the birds that are waiting their turn.
Link Posted: 9/25/2004 6:17:53 PM EST
We have one sitting out in front of the musem here at Campbell. I have always been intriged by it everytime I drive by it.
Link Posted: 9/27/2004 5:09:14 AM EST

Originally Posted By jd1:
When I was stationed at Polk I saw the Cheyenne. It was at the museum in the back under a bunch of pine trees. They didn't make a big deal out of it. I thought it was a shame for this revolutionary aircraft to be relegated to where very few people will see it. It may not be seen by any more people at the airfield but at least it'll be in a place of honor.

jd1


Stationed at Ft Polk in 1979-80. This was one of my favorite displays. Even sat in the cockpit. (None of the displays were locked)

I had assumed that it had been scrapped when they shut down the 5th ID, I'm glad to see it's still around.
Link Posted: 9/27/2004 6:07:03 AM EST

Originally Posted By redleg13a:
Not sure how much of this is true, but I understood that the Air Force threw a big fit over the AH 56 specifically because of the lift provided by the stubby wings. They were designed to provide significant lift to the aircraft enabling greater loads to be carried and more speed. When the AF became it's own branch, there was a specific agreement that the Army could not have armed fixed-wing aircraft. Hence, the reason the OV10's could not carry HE warhead rockets in VN. My understanding was that this agreement also helped kill the AH56 program.



The whole AF/Army pissing match over fixed wing vs. helo has probably done more to set back US military aviation then all the Soviet espionage during the Cold War put together. What bullshit, think how far this technology would be today with 30+ years of development. Would probably be better than using Chinooks as Tactical troop carriers at high altitudes in the mountains in Afghanistan.
Link Posted: 9/29/2004 10:00:15 PM EST

Originally Posted By TomJefferson:
Ah yes, Ft Puke, Lousyanna, nested next to the beautiful city of Diseaseville, my once home!

Tj


Been there, done that...
Link Posted: 9/29/2004 10:10:50 PM EST
[Last Edit: 9/29/2004 10:11:34 PM EST by Da_Bunny]
I went through the Cobra Transition Course in October of 1971, enroute to Vietnam. While I was there, Sikorsky was showing off it's competitor to the Cheyenne.

The S-67 Blackhawk:
Link Posted: 9/29/2004 10:26:04 PM EST
Good pics.
Link Posted: 9/29/2004 11:00:54 PM EST
Link Posted: 9/30/2004 8:11:18 AM EST
I was at Ft Polk 1990-1992. A bud and I restored the IG37 anti-tank gun (the short 75mm in camo) at the museum for use in re-enacting. The museum has some unusual pieces inside. There's a left side feed Stoner 63A and a 3-shot M79. The 3-shot M79 has a sliding breechblock that feeds the rounds sideways.
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