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Posted
That's not quite true. The V-22 can do rolling landings and takeoffs with nacelles at 60 degrees. In fact that is the only way to take off at very high weights because it can't do a vertical takeoff in that situation.

 

With regard to vortex ring state (VRS), according to Lt Col Kevin Gross (former V-22 flight test director at Pax):

 

"Pilot recovery procedures from a VRS roll off are easy, immediate, and effective. The pilot fixes the thrust-control lever and simultaneously pushes the nacelle-control thumb wheel forward for two seconds. This two-second beep forward moves the nacelles 12 degrees to 15 degrees lower, which immediately takes the rotors out of the VRS condition as the aircraft accelerates rapidly. If required, the pilot then uses lateral stick to level the wings and then adds power to stop the rate of descent." (taken from his article in USNI Proceedings)

197041[/snapback]

 

Well, I think that 'rolling' landings and takeoffs are still hovering/OGE evolutions vice wing-aerodynamic in the main, and "landing" in wing-aerodynamic forward flight mode with the rotors breaking off is still crashlanding. I just think that single engine operation for these buggers remains quite different from, say, a nice Beech C-12. I do not think it amounts to an operational capability and if one engine is gone, how are the necessary transitions going to be so easy, especially with payloads? These seem more in the realm of crashworthiness/personnel-survival features long advertised as a strong suite of the A/C program. Single engine MV-22s are likely to look for setdowns.

 

Helicopters, we must remember, are in the air not by nature but by modified brute force. We had an AH-1T auger in on our tank range in '80, just 'cause he lost his minimums, had no energy reserve, etc. VRS is just one more thing for these guys to handle, and when the shooting starts will come yet another set of challenges.

 

It is not armored [exc for pilot seats/glass], by the way, and there were some radical opinions on just how good the fuselage/wing laminates resist bullets way back in the late 80s, with talk of it opening up like onion skin. I wonder if we did the destructive testing that one of the first 4 prototypes were supposed to do.

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Posted
Correct. However, the V-22 does not have enough power to hover on one engine because of its high disk loading rotor. This was true 15 years ago when I was flight testing it; I assume it is still true today.

196674[/snapback]

 

Hi Kenneth,

 

I thought that all of the weight saving efforts since then had helped eliminate this problem ...

 

--Garth

Posted
Will this have a major impact on airborn troop operations?

 

Yes, and no. For conventional air assault, it will have an impact mainly because the Marines are hamstrung with the CH-46 being their prime people mover. Any new people mover will improve their large scale air assault capability. And the increased speed and range will have an evolutionary effect. But there is the limitation of the Osprey outrunning the Cobras, which will take some changes in operations to get the Cobras out to the LZs first, and/or get the Hornets on orbit. And there is the task of getting arty and ground vehicles out to the LZs as well, the Osprey doesn't help too much with that.

 

Where things will appear revolutionary is spec ops (which is what the Osprey was designed for in the first place) and reaction forces, where the combo of higher speed and longer range can really leverage those troops.

 

Will the V22(and furture possible offspring) end up replacing the majority of military helicopters?

 

Nope, there will always be a need for medium and heavy lift which are better served with conventional helos.

Posted (edited)
1. I think you have a typo there (bold).

 

2. The Bell-Boeing V-22 Pocket Guide printed in June 2001 claims "...Interconnect driveshafting provides safe one-engine-out flight in all modes of operation."  It doesn't say whether this means the aircraft will hover, or just crash more slowly... ;)

 

3. I tried using your formulas and I must be losing units somewhere because I am getting thrust figures for the CH-46E of 6,103lb at 1870shp

197185[/snapback]

1. Yes typo in source and compounded by my getting confused and dividing it by half of 6150 (so like I said I applied 16% additional power to both)

 

2. I think what Ivanhoe and others mentioned before is the probable capability: at high GW in low hover "safely" bump back down or be stuck IGE and let down; some higher hovers transition to 60deg position and "safely" find a short field pronto; really high hover or already airplane mode fly on in airplane mode and land short field. Lot's of snippets of official stuff imply the latter two (eg. a returning single engine would require some wind over deck at sea) explicit statement of the first I haven't seen but with all the controversy, I think they'd say it could climb in hover at any hovering weight, if it could. The USMC official info site gives 47.5k as *vertical* MTOW, 55 as rolling. The formula gives 42.8k lift at 6980hp, presumably that's OGE (again assuming it's basically right, it doesn't look wildy wrong, see 3, but I can't say it's very close, the thing that's certain either from that formula or momentum/energy theory is that the MV-22 gives up most or all the advantage in hover of its lower power loading than a CH-46 by its high disk loading). I guess actual operational profiles would assume that high GW TO's would tend to be followed by relatively longer flights and fuel burnoffs before hovering over rough terrain, or alternatively jettisoning a heavy sling load if necessary to avoid crashing.

 

3. For that example,

PL= 1870/2043=.915321

TL=8.6859*(.915321)^-.3107=8.927997

T=8.927997*1870=16,695lb

Lift to weight ratio=16,695/24,300=69%

 

Joe

Edited by JOE BRENNAN
Posted (edited)
Yes, and no. For conventional air assault, it will have an impact mainly because the Marines are hamstrung with the CH-46 being their prime people mover. Any new people mover will improve their large scale air assault capability. And the increased speed and range will have an evolutionary effect. But there is the limitation of the Osprey outrunning the Cobras, which will take some changes in operations to get the Cobras out to the LZs first, and/or get the Hornets on orbit. And there is the task of getting arty and ground vehicles out to the LZs as well, the Osprey doesn't help too much with that.

 

Where things will appear revolutionary is spec ops (which is what the Osprey was designed for in the first place) and reaction forces, where the combo of higher speed and longer range can really leverage those troops.

 

Will the V22(and furture possible offspring) end up replacing the majority of military helicopters?

 

Nope, there will always be a need for medium and heavy lift which are better served with conventional helos.

197335[/snapback]

 

I was under the imperssion that new airframes of Osprey decent might be on the way eventualy.

 

V44 for heavy lift: http://www.popularmechanics.com/science/av...html?page=2&c=y

 

 

Also I belive in one or both of these articles the gunship version is mentioned.

 

http://www.ausairpower.net/TE-V-22A-Osprey.html

 

http://www.globalsecurity.org/military/lib...rt/1990/LLM.htm

 

 

Gunship applications are just one of several ideas being explored. A joint panel is looking at all of the rotorcraft possibilities. "They're looking at joint common lift replacement aircraft, to include a medium assault, a utility and an attack and anti-armor aircraft," explains Marine Corps Capt. Aisha Bakkar-Poe. "The Marine Corps' view is that tiltrotor is the way of the future because it has such a longer range and goes so much faster that it almost makes a helicopter obsolete."

 

 

Edited by Samson
Posted

No, the FSD aircraft were terribly overweight. The subsequent redesign and weight reduction simply brought the weight down to roughly where it should have been.

 

Hi Kenneth,

 

I thought that all of the weight saving efforts since then had helped eliminate this problem ...

 

--Garth

197240[/snapback]

Posted

Rolling T/O and landing is definitely not hovering. I don't know the relative contributions of the wing and the rotor at a nacelle angle of 60 degrees but both are substantial. Landing with the nacelles at 60 degrees is definitely not crashing. Landing with nacelles at 0 degrees (airplane mode) is going to trash the aircraft, but the only reason to do it would be if the nacelle conversion actuators are all inop which is unlikely due to their ballistic tolerance, fail-safe design and redundancy. One engine flight in cruise mode is an emergency but not an unmanagable one.

 

Key V-22 systems such as gearboxes are ballistically tolerant. There is a high degree of redundancy of critical systems. The fuel cells are inerted with nitrogen-enriched air and there are fire suppression systems. It ought to be pretty survivable but it is no tank. IIRC, aircraft #1 was shot up as part of live fire testing a while back.

 

I think that there is no fundamental reason why the V-22 Osprey can not be a successful weapon system, but the cost is a major issue.

 

Well, I think that 'rolling' landings and takeoffs are still hovering/OGE evolutions vice wing-aerodynamic in the main, and "landing" in wing-aerodynamic forward flight mode with the rotors breaking off is still crashlanding.  I just think that single engine operation for these buggers remains quite different from, say, a nice Beech C-12. I do not think it amounts to an operational capability and if one engine is gone, how are the necessary transitions going to be so easy, especially with payloads?  These seem more in the realm of crashworthiness/personnel-survival features long advertised as a strong suite of the A/C program. Single engine MV-22s are likely to look for setdowns.

 

Helicopters, we must remember, are in the air not by nature but by modified brute force. We had an AH-1T auger in on our tank range in '80, just 'cause he lost his minimums, had no energy reserve, etc. VRS is just one more thing for these guys to handle, and when the shooting starts will come yet another set of challenges.

 

It is not armored [exc for pilot seats/glass], by the way, and there were some radical opinions on just how good the fuselage/wing laminates resist bullets way back in the late 80s, with talk of it opening up like onion skin. I wonder if we did the destructive testing that one of the first 4 prototypes were supposed to do.

197224[/snapback]

Posted

Here are the equations for helicopter performance in OGE hover, with zero vertical or translational velocity.

 

P_installed = installation efficiency * P_uninstalled

 

The installation efficiency factor is generally around 85%, which means that 15% of engine power is dissipated by things such as engine inlets, tail rotors, transmissions and aerodynamic download. The V-22 does not have a tail rotor but loses about 9% of engine power due to rotor wash impingement on the wing and fuselage.

 

P_installed = P_induced + P_profile

 

Induced power is the power used to pull the air through the rotor. Profile power is the power expended to overccome the viscous drag of the rotor blades as they move through the air.

 

P_induced for zero velocity OGE hover = Weight * SQRT (Disk loading / (2 * air density))

 

This can be derived from fairly simply momentum theory but I'm not going to do it here. As you can see, the general trend is that higher weight, higher disk loading and lower air density (meaning hot and/or humid and/or high altitude) all require more power.

 

Also note that a turboshaft engine will produce less power when the air density is lower. That means that hot, humid and/or high is a double whammy for hover performance. That is why in sea level standard conditions, the V-22 engines can put out more power than the transmissions can handle. The V-22 needs engines which are too powerful at high air density to be sufficient at low air density.

 

P_profile is very complicated to calculate but in practice is less than P_induced. Rough general rule of thumb: P_profile = 0.5 * P_induced.

Posted
My concern about the MV-22 -- beyond mechanical and dispatch reliability -- it that the envelope restrictions due to vortex ring state may be more drastic than those imposed on standard rotary wing aircraft (I've heard rumors that this is in fact the case). That just makes the Osprey more vulnerable in peri-LZ operations -- which is already the most dangerous part of any mission profile to begin with.

196800[/snapback]

 

 

Very interesting piece on MV22 in current issue of Air & Space. Considerable discussion of this issue. Testing found not to be a serious as originally thought. As I recall vert. decent of more than 4000ft/min before an issue. I'll dig out my mag from pile ____.

Posted

Why bother with a tilt-rotor gunship, or worry about AH-1s being able to keep up? The OV-10 has sufficient performance to be launched from LHA/LHD-type ships, keep up with the V-22, and provide the necessary attack capability. After all, if you are going into a hot LZ, you aren't planning to land you attack heloes in the LZ.

 

Douglas

Posted

And I recall seeing pics of a foreign OV-10 COIN variant (Malaysian?) which replaced the cargo space in the back with a quad .50 mount, allowing strafing of a target on the way in, and on the way out. Tres schweet.

 

Of course you know, the OV-10 ain't coming back, no way, no how. They'll find some fast movers to do the job, which will provide at LEAST 2 minutes loiter time over the target... And which will be too expensive to risk in low altitude CAS missions anyway. <_<

 

Why bother with a tilt-rotor gunship, or worry about AH-1s being able to keep up?  The OV-10 has sufficient performance to be launched from LHA/LHD-type ships, keep up with the V-22, and provide the necessary attack capability.  After all, if you are going into a hot LZ, you aren't planning to land you attack heloes in the LZ.

 

Douglas

197650[/snapback]

Posted
Would an V-22 AEW&C be worth pursuing for helicopter carriers?

197802[/snapback]

Boeing-Bell-Textron would say Jawohl!

 

In the early days of exuberance over the V-22 program, there was no shortage of applications, including the gunship variants to escort the troop/cargo birds. I bet the Secret Service will never allow a POTUS to fly in one though, however plush a VIP version becomes.

 

Remember, the classic stages of a project:

1. Exhilaration

2. Extravagant goals

3. Panic

4. Search for the guilty

5. Punishment of the innocent

6. Praise and Promotion for the non-participating

Posted (edited)
Would an V-22 AEW&C be worth pursuing for helicopter carriers?

197802[/snapback]

 

It should have better transit speed & time on station than the helicopter AEW some countries use.

Edited by swerve
Posted

There are only two stages to a project: Too soon to tell & too late to cancel. ;)

 

Yeah, the OV-10 is gone, but it does point the way to the rational solution to the problem. I've done enough tilting at windmills to know that the rational solution is unlikely to be pursued. There are too many egos and fiefdoms to be protected. Still, a fixed-wing STOL light attack aircraft compatible with LHDs has a lot going for it when paired with the V-22. The PA-48 Enforcer, OV-10, and AD Skyraider would all fit this niche nicely, but the hardware is less important than the capability. I am sure that it would be relatively easy to develop a new aircraft based on the performance requirements, but the final answer will probably be a $100 million UAV... :blink: Hmm, I've never run the numbers to determine whether a A-10 would be capable of launch from an LHD-length deck. Slap folding wings on that bad boy... :) :P

 

Here's an interesting point of view on the development of the OV-10. http://www.volanteaircraft.com/ov-10.htm I don't know enough about the history of the aircraft to say whether this is accurate, or not, but it is interesting, all the same.

 

Douglas

Posted

This was considered by Bell-Boeing.

 

Would an V-22 AEW&C be worth pursuing for helicopter carriers?

197802[/snapback]

Posted
Why bother with a tilt-rotor gunship, or worry about AH-1s being able to keep up?  The OV-10 has sufficient performance to be launched from LHA/LHD-type ships, keep up with the V-22, and provide the necessary attack capability.  After all, if you are going into a hot LZ, you aren't planning to land you attack heloes in the LZ.

 

Douglas

197650[/snapback]

 

Years ago there was a great article (maybe in A&S, irrc) that proposed a heavily redesigned (turboprops, modern avionics etc) F7F Tigercat as being the optimal V-22 escort. While capable of unassisted deck launches, such would require the addition of arresting gear to the LHA/LHDs.

 

--Garth

Posted

Ah yes, everything will be redesigned to accomodate the V-22. Shit, we'll reorganize the rifle squad around it. It's going to make bread itself obsolete, let alone slicing it, fire is a thing of the past now that the Ospery is here :angry:

 

Do all these V-22 Albatross guys sit around and fellate one another in a giant circle? We would be on the follow on generation to CH-46 replacement if we hadn't got tied into this POS. S/F....Ken M

Posted
There are only two stages to a project:  Too soon to tell & too late to cancel.  ;)

 

Yeah, the OV-10 is gone, but it does point the way to the rational solution to the problem.  I've done enough tilting at windmills to know that the rational solution is unlikely to be pursued.  There are too many egos and fiefdoms to be protected.  Still, a fixed-wing STOL light attack aircraft compatible with LHDs has a lot going for it when paired with the V-22.  The PA-48 Enforcer, OV-10, and AD Skyraider would all fit this niche nicely, but the hardware is less important than the capability.  I am sure that it would be relatively easy to develop a new aircraft based on the performance requirements, but the final answer will probably be a $100 million UAV... :blink:  Hmm, I've never run the numbers to determine whether a A-10 would be capable of launch from an LHD-length deck.  Slap folding wings on that bad boy... :)  :P

 

Here's an interesting point of view on the development of the OV-10.  http://www.volanteaircraft.com/ov-10.htm  I don't know enough about the history of the aircraft to say whether this is accurate, or not, but it is interesting, all the same.

 

Douglas

197840[/snapback]

 

 

I always liked the OV10. Lately I have been wondering if it would make a VERY effective UAV gunship...

 

A gunship derived fromt eh BA 609 might be another option. give it a slimmer fuselage similar to the Cobra...

Posted
Years ago there was a great article (maybe in A&S, irrc) that proposed a heavily redesigned (turboprops, modern avionics etc) F7F Tigercat as being the optimal V-22 escort.  While capable of unassisted deck launches, such would require the addition of arresting gear to the LHA/LHDs.

 

--Garth

197969[/snapback]

 

 

 

I never saw that! I think I'd vote for it! I really never learned enything about the Tigercat until the last year or so. what a beauty!

 

Replace the 4x.50s and 4x20mms with something a little more modern? Maybe 2x Mauser BK27s or 30mm guns (I'm growing to like the French one) in the wing roots? One Gau19 in the nose for lighter targets?

 

Ok, that is probably silly. No, that is Definately silly, but fun nonetheless. ;)

Posted

Way back when I was flight testing the V-22 for Boeing, we didn't do that sort of thing. Now that the weapon system has been turned over the Marines, I don't know for sure. Maybe they are into that stuff. :)

 

Do all these V-22 Albatross guys sit around and fellate one another in a giant circle?

198015[/snapback]

Posted

Ken, I generally don't hammer the techo-wonks, they're just doing their jobs. Yep, I am blaming the USMC in this case. I constantly hear all about being a careful steward of the taxpayer's dollar and we generally do a decent job. The V22 has brought out a new low in dishonestly and corruption. People should be shot for this bullshit. S/F....Ken M

Posted
Here's an interesting point of view on the development of the OV-10.  http://www.volanteaircraft.com/ov-10.htm  I don't know enough about the history of the aircraft to say whether this is accurate, or not, but it is interesting, all the same.

197840[/snapback]

 

Interesting read.

 

"In spite of these successful operations in three services, the light attack component was overshadowed more and more by the Air Force's opposition to anything that would give the "Grunts" on the ground anything airborne except what was left over after Air Force priorities were met. This eventually forced the Army into the development of the armed helicopter as the only way it could get the timely and dependable support needed....Thus the development of the armed helicopter, not only for the Army and Marines who followed their lead, but for practically every Army of consequence in the world. In spite of the fact that practically everything an attack helicopter could do, could be done cheaper and better with a fixed wing aircraft of proper design, Air Force politics overruled it"

 

I'd heard that before somewhere, armed helicopters are essentially a result of politics.

Posted
Interesting read.

 

"In spite of these successful operations in three services, the light attack component was overshadowed more and more by the Air Force's opposition to anything that would give the "Grunts" on the ground anything airborne except what was left over after Air Force priorities were met. This eventually forced the Army into the development of the armed helicopter as the only way it could get the timely and dependable support needed....Thus the development of the armed helicopter, not only for the Army and Marines who followed their lead, but for practically every Army of consequence in the world. In spite of the fact that practically everything an attack helicopter could do, could be done cheaper and better with a fixed wing aircraft of proper design, Air Force politics overruled it"

 

I'd heard that before somewhere, armed helicopters are essentially a result of politics.

198344[/snapback]

It seems to be a thread you find when reading about the AH-56 Cheyenne, as well. Basically, that helo was designed as a rotary-winged airplane because the Key West agreement doesn't permit armed fixed-wing with "US Army" painted on the side. On paper, it makes a nice idea to split the USAF along the lines of the old SAC/TAC divide and hand the TAC portion over to the Army, along the lines of USMC air, but there are probably a lot of problems with this thought.

 

Douglas

Posted
Ok, that is probably silly.  No, that is Definately silly, but fun nonetheless.  ;)

198142[/snapback]

 

I'll see if I can find the article. It was a loooooong time ago, but I do remember discussing it hear on this grate sight.

 

It's actually not that silly ... iirc the writer made a VERY convincing case that it would substantially outperform the AV-8B in the CAS role.

 

--Garth

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