Jeff Posted July 16, 2005 Posted July 16, 2005 Well it's taking a big step towards full production and IOC. U.S. Navy Finds Tiltrotor Osprey Aircraft “Suitable”By JIM WOLF, REUTERS, WASHINGTON A revolutionary troop transport aircraft that killed a total of 23 U.S. Marines in flight-test crashes five years ago has been found to be “suitable and effective,” an important step for the nearly $50 billion program, the Navy said July 13. The finding followed a revamped operational evaluation of the Marine Corps’ MV-22 Osprey, a hybrid with engines that can tilt 90 degrees to take off and land like a helicopter and to fly like a plane. Textron Inc.’s Bell Helicopter unit and Boeing Co. co-developed the Osprey, which still would have to be found operationally suitable by U.S. Defense Department testers before it could enter full production, said Ward Carroll, a Navy spokesman. The Defense Acquisition Board, a high-level Pentagon panel that must approve key stages in the purchase of major U.S. weapons, is to consider whether the aircraft is ready for full production at a scheduled Sept. 27 meeting, Carroll said. The Osprey is designed to replace the aging workhorse CH-46 Sea Knight helicopter. It can fly twice as fast at more than twice the altitude, with three times the payload and six times the range, according to the Navy. The Marine Corps wants to buy 360 Ospreys, which currently cost $71 million each. The Department of the Navy, which includes the Marine Corps, is aiming to knock that price down to $58 million by fiscal 2010 in then-current dollars, Carroll said. In November 2000, naval testers similarly declared the aircraft suitable and effective despite a fatal Osprey crash in April of that year. A second crash occurred in December 2000, bringing the total of Marines killed in fight tests to 23 and leading to a rigorous new flight-evaluation program after a 17-month grounding. Carroll said the Navy’s operational testers had found three remaining MV-22 problem areas involving radios, troop seat comfort and electronic warfare warning gear. “All have been addressed and will be corrected before the aircraft reaches the fleet,” he said from New River, North Carolina, where the Marine Corps hosted Osprey rides for reporters to publicize the findings. Currently, Osprey production is capped at a “minimum sustaining” level of 11 per year. The Bell/Boeing output would gradually rise to a peak of 48 a year once full production was approved by the Pentagon. The Air Force version of the Osprey, called the CV-22, is scheduled to undergo a separate operational testing phase late next year.http://www.defensenews.com/story.php?F=973091&C=america
Samson Posted July 16, 2005 Posted July 16, 2005 Praying to God this think works and realy is ready for the real world...
Burncycle360 Posted July 16, 2005 Posted July 16, 2005 I hope it does work as advertised. The bad boy costs more than an F-15 and will probably be just as mantinence intensive even new, with all those articulating and folding parts. It's almost a transformer....
Paul in Qatar Posted July 16, 2005 Posted July 16, 2005 I wish them the best of luck, but I will reassured when Marine Corps One is an Osprey. The article in Wired magazine says they have got it fixed, but with its troubled history, I want to be shown the darn thing is OK.
Slater Posted July 16, 2005 Posted July 16, 2005 I've always wondered, if a V-22 is in a hover over an LZ and one engine fails (or gets shot out), supposedly there's some measure to keep both rotors turning and avoid an instant disaster?
Ivanhoe Posted July 16, 2005 Posted July 16, 2005 I've always wondered, if a V-22 is in a hover over an LZ and one engine fails (or gets shot out), supposedly there's some measure to keep both rotors turning and avoid an instant disaster?196269[/snapback] Yes, there is a cross-shaft running thru the wing that connects both trannies.
Kenneth P. Katz Posted July 18, 2005 Posted July 18, 2005 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. Yes, there is a cross-shaft running thru the wing that connects both trannies.196270[/snapback]
Rickshaw Posted July 18, 2005 Posted July 18, 2005 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] So what happens? Does it slowly or quickly descend?
Kenneth P. Katz Posted July 18, 2005 Posted July 18, 2005 I don't recall the exact performance data. It doesn't drop like a rock when hovering on one engine, but it will is definitely descending. So what happens? Does it slowly or quickly descend?196685[/snapback]
gewing Posted July 18, 2005 Posted July 18, 2005 I don't recall the exact performance data. It doesn't drop like a rock when hovering on one engine, but it will is definitely descending.196692[/snapback] I supsect it could try to translate into forward flight, where it might need less power?
Ken Estes Posted July 18, 2005 Posted July 18, 2005 I supsect it could try to translate into forward flight, where it might need less power?196694[/snapback]Nope, remember it does not land in forward flight. These are crashworthiness features, not impared operating capabilities. Since blade vortex problems do not go away, the solutions to the fatal crashes probably amount to more stringent flight envelope definitions, and the flight testing presumably demonstrated sufficient reserve through the required maneuvers and mission profiles. Hope it works, as too much treasure has gone into this.
Guest aevans Posted July 18, 2005 Posted July 18, 2005 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.
Ivanhoe Posted July 18, 2005 Posted July 18, 2005 Single engine hover OGE cannot be done at max gross weight, but it can be done at lighter weights (ISTR iits closer to empty wet than max gross). If the vehicle is in ground effect at say 80% of MGTW it probably can continue hovering but won't be able to climb out of ground effect vertically. If terrain permits, it can start flying forward to get to the "power bucket" speed (typically around 60 KTAS for conventionals, probably closer to 90 for the V-22) in which case a slow climb and transition to airplane mode may be possible. But IMHO trying to fly out of mechanical problems is usually worse than setting the thing down, even on ugly terrain*. Given a successful climb and transition to airplane mode, if a base or FARP can be reached, with skillful flying the aircraft can be landed. Enter into a descent and rotate the pylons to about 60 degrees, and execute a short run-on landing with a flare at the end. Just like with conventional helicopter autorotation, you trade potential energy (altitude) for kinetic energy (rotor power). * Recall the recent rescue op in Afghanistan, where the RPG hits didn't kill the Chinook, but the crash ensuing from attempted flight.
Ol Paint Posted July 18, 2005 Posted July 18, 2005 The aircraft is designed to be able to land with the nacelles in the horizontal position--the proprotor blades are supposed to "broom-straw" on impact with the ground, rather than break chunks off. I'm a little surprised that the engines do not provide the ability to hover OEI given that they provide ~6,150shp/ea for a power loading of 8.4lb/shp (max VTO weight) or 6.8lb/shp (at 1/2 way between full load and empty weight) while we don't seem to have the same doubts about the CH-46E with its power loadings of 13.0lb/shp (max weight) and 11.2lb/shp (halfway between max gross weight and empty weight). While Kenneth has flight experience in the machine and indicates that there is not sufficient power to maintain a hover, I find the situation a little odd, to say the least. Douglas
Slater Posted July 18, 2005 Posted July 18, 2005 So when are we supposed to see the first operational V-22 squadron?
Ol Paint Posted July 18, 2005 Posted July 18, 2005 (edited) So when are we supposed to see the first operational V-22 squadron?196882[/snapback]Flight International says March 1, 2006 with IOC in Feb/March 2007: http://www.flightinternational.co.uk/Artic...rne+trials.html Douglas [Edited for misunderstanding question.] Edited July 18, 2005 by Ol Paint
Corinthian Posted July 18, 2005 Posted July 18, 2005 I wish them the best of luck, but I will reassured when Marine Corps One is an Osprey. The article in Wired magazine says they have got it fixed, but with its troubled history, I want to be shown the darn thing is OK.196239[/snapback] Now that'd be cool - a Marine One Osprey. Would really love to see this working properly. I hope it's armoured enough too
Ivanhoe Posted July 19, 2005 Posted July 19, 2005 Early on in the Osprey development, the Marines considered using it as a POTUS taxi. The problem of course was that even if it had been fielded by 1995, they would just now have the decade plus of flight experience required to satisfy their own requirements for reliability, maintainability, etc for the VIP fleet. I guess by 1990 or so it was pretty obvious the funding/political terrain was way too rocky to even consider making any such plans.
Kenneth P. Katz Posted July 19, 2005 Posted July 19, 2005 The VV-22 (tentative designation for the Marine One variant of the V-22) underwent some preliminary design work in the early 1990s. Early on in the Osprey development, the Marines considered using it as a POTUS taxi. The problem of course was that even if it had been fielded by 1995, they would just now have the decade plus of flight experience required to satisfy their own requirements for reliability, maintainability, etc for the VIP fleet. I guess by 1990 or so it was pretty obvious the funding/political terrain was way too rocky to even consider making any such plans.197033[/snapback]
Kenneth P. Katz Posted July 19, 2005 Posted July 19, 2005 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) Nope, remember it does not land in forward flight. These are crashworthiness features, not impared operating capabilities. Since blade vortex problems do not go away, the solutions to the fatal crashes probably amount to more stringent flight envelope definitions, and the flight testing presumably demonstrated sufficient reserve through the required maneuvers and mission profiles. Hope it works, as too much treasure has gone into this.196776[/snapback]
Kenneth P. Katz Posted July 19, 2005 Posted July 19, 2005 What your analysis is missing is that the relevant issue in hover is not power but thrust. The V-22 has high disk loading on its proprotors (lots of weight spread over a small area) so it converts power to thrust quite inefficiently. That's the catch with a tiltrotor: compared to a helicopter it is fast and efficient in cruise but for VTOL and hover it is a marginal machine. The only reason why the V-22 can do VTOL and hover at all is that it has very high power loading. The utlimate case of high disk loading is an AV-8B or an X-35B. Extremely high disk loading so it takes extremely high power to generate enough lift to do VTOL and hover. The aircraft is designed to be able to land with the nacelles in the horizontal position--the proprotor blades are supposed to "broom-straw" on impact with the ground, rather than break chunks off. I'm a little surprised that the engines do not provide the ability to hover OEI given that they provide ~6,150shp/ea for a power loading of 8.4lb/shp (max VTO weight) or 6.8lb/shp (at 1/2 way between full load and empty weight) while we don't seem to have the same doubts about the CH-46E with its power loadings of 13.0lb/shp (max weight) and 11.2lb/shp (halfway between max gross weight and empty weight). While Kenneth has flight experience in the machine and indicates that there is not sufficient power to maintain a hover, I find the situation a little odd, to say the least. Douglas196873[/snapback]
Ol Paint Posted July 19, 2005 Posted July 19, 2005 What your analysis is missing is that the relevant issue in hover is not power but thrust. The V-22 has high disk loading on its proprotors (lots of weight spread over a small area) so it converts power to thrust quite inefficiently. That's the catch with a tiltrotor: compared to a helicopter it is fast and efficient in cruise but for VTOL and hover it is a marginal machine. The only reason why the V-22 can do VTOL and hover at all is that it has very high power loading. The utlimate case of high disk loading is an AV-8B or an X-35B. Extremely high disk loading so it takes extremely high power to generate enough lift to do VTOL and hover.197044[/snapback]Thanks for the explanation, Ken. I'll have to ruminate on this when I have more time--and read up on it. As an enthusiast, not an aerospace engineer, it is still surprising to me that the V-22 can't hover on one engine when its power loading on one engine is nearly the same as a CH-46E on two. I knew there was an efficiency sacrifice, I just didn't realize that it was that great. Douglas
JOE BRENNAN Posted July 19, 2005 Posted July 19, 2005 (edited) Re rotor lift and power, an empircal formula I found on webhttp://www.heli-chair.com/aerodynamics_101.htmlis Lift=Thrust loading*powerThrust loading=8.6859*Power loading^-.3107Power loading=Power/areaFrom the examples, sq ft and hp are the units. From Francillon's "World Military Aviation 1997-98" (just for arguments sake, not necessarily up to date)MV-22: max VTO Wt=55,000; 2*6150 hp, total disk area 2268sq ftCH-46E: MTO Wt=24,300, 2*1870hp, total disk area 2043sq ft Per the formula lift to weight ratio's single and twin engine (not assuming any higher temporary rating for engine out ops*) are similar, 71% and 115% for the MV-22, 69 and 111 for the CH-46. I don't know if that formula is universally accepted, simplistic theory would have that exponent as -.5, I think. Anyway though the CH-46 has 13lb/hp loading engine out v. 8.9 for the MV-22 given those wts and powers, the efficiency in lb thrust/hp is 40% better per the formula or 70% better per pure theory for the CH-46. *I don't know the CH-46/T58 engine out rating, MV-22/T406 is 3584hp or 16.5% extra, applying to both numbers would be 79% and 76%. Joe Edited July 19, 2005 by JOE BRENNAN
Ol Paint Posted July 19, 2005 Posted July 19, 2005 (edited) Re rotor lift and power, an empircal formula I found on webhttp://www.heli-chair.com/aerodynamics_101.htmlis Lift=Thrust loading*powerThrust loading=8.6859*Power loading^-.3107Power loading=Power/areaFrom the examples, sq ft and hp are the units. From Francillon's "World Military Aviation 1997-98" (just for arguments sake, not necessarily up to date)MV-22: max VTO Wt=55,000; 2*6150 hp, total disk area 2268sq ftCH-46E: MTO Wt=24,300, 2*1870hp, total disk area 2043sq ft Per the formula lift to weight ratio's single and twin engine (not assuming any higher temporary rating for engine out ops*) are similar, 71% and 115% for the MV-22, 69 and 111 for the CH-46. I don't know if that formula is universally accepted, simplistic theory would have that exponent as -.5, I think. Anyway though the CH-46 has 13lb/hp loading engine out v. 8.9 for the MV-22 given those wts and powers, the efficiency in lb thrust/hp is 40% better per the formula or 70% better per pure theory for the CH-46. *I don't know the CH-46/T58 engine out rating, MV-22/T406 is 3584hp or 16.5% extra, applying to both numbers would be 79% and 76%. Joe197178[/snapback]Joe, I think you have a typo there (bold). The AE1107C engine is rated at 6,150shp continuous/6,980shp intermittent per this site. The USMC data sheet for the CH-46E gives engine ratings as 1,770shp continuous/1,870shp intermittent. Again, that's a per-engine rating. 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... [Edit: 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 & 5,877lb at 1870shp & 1770shp, respectively. Gross weights would be 24,300lb max and 19,830lb at the halfway mark. For the V-22, the thrust figures are 13,818lb & 12,664lb at 6,980shp & 6,150shp, respectively. Gross weights are 51,690lb and 42,415lb for the same relative conditions. The ratios between the weights (V-22/CH-46E) are on the order of 2.13:1 with the ratios between the thrust numbers at 2.15-2.26:1. I'll have to try to remember to look at this issue again in a couple of weeks, when I have time to figure out where I am going wrong. Something is screwy, since these hypothetical numbers aren't even close, so I don't feel comfortable drawing any conclusions from my analysis so far. ] [2nd Edit to clarify ratios.] Douglas Edited July 19, 2005 by Ol Paint
Samson Posted July 19, 2005 Posted July 19, 2005 So... Assuming it will be reliable and perform as advertised... Will this have a major impact on airborn troop operations? Will the V22(and furture possible offspring) end up replacing the majority of military helicopters?
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