Armed Polite Society
Main Forums => The Roundtable => Topic started by: MillCreek on October 12, 2008, 10:43:03 PM
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Paging Leatherneck and other knowledgeable parties.......
On another forum I frequent, there is some discussion about the V-22 Osprey's capabilities. I just read the Wikipedia article, and it looks as if the Osprey is actually deployed in the field now. So how is it working out?
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Overall, not bad.
The pro's: They're mainly being used for cargo/people moving between bases/FOB's. They've done a bunch of scouting missions, with pretty good success.
The con's: Parts, Lack Of. Some of the field maintenance is overly difficult. Ask a VMM-263 wrench turner how they repair the hydraulic piping.
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The Air Force is using theirs pretty much on a regular basis now.
You've all heard about that freighter that lost power during Hurricane Ike - Hurlburt Field sent two Ospreys out for the rescue, but conditions on-scene were just too much, with 20 foot seas and 80 knot winds.
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Yup. The MV-22 is operating in Iraq--pretty much as a flying truck, which was its original purpose (replacing the venerable Phrog). The third MV squadron-VMM-266-just arrived, headed by my old friend Mongo and staffed by a lot of old hands from the long test program..
The CV-22 is done with IOT&E and we're analyzing the tons of data from the Western electronic warfare test ranges. The first CV-22 Det is about to go operational.
As in all things, the USAF has provided for spares and the logistics pipeline better than the Marines. So in Iraq, they wait and wait for parts. In fairness, one of the worst unexpected failure items in-country has been the engines. But the Marines bought "power-by-the-hour" from Rolls, so RR is having to suck up most of the cost of accelerated engine removals.
Have you seen the artist's concept for the Quad tiltrotor candidate for the next-generation heavy lifter? It resembles two V-22s mating. =D
Supposed to lift 40,000 pound payload, with 50,000 desired. It will replace the Chinook in the Army and the CH-53K (still in development) in the Corps.
TC
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So, after initial problems, they have for the mos part worked out? The predictions of the Osprey-o-phobes not quite accurate?
If so, that is a good thing.
If they can apply the lessons learned from the Osprey to that new monster, so much the better.
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The big thing was to realize it was an aircraft that could hover/vtol, NOT a helicopter. If one takes a V-22 and tries to do certain helicopter manuvers with it, it will fall out of the sky. If one flies it like a V-22, your survival odds get much better.
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Overall, not bad.
The pro's: They're mainly being used for cargo/people moving between bases/FOB's. They've done a bunch of scouting missions, with pretty good success.
The con's: Parts, Lack Of. Some of the field maintenance is overly difficult. Ask a VMM-263 wrench turner how they repair the hydraulic piping.
I have read of it. 6000psi hydraulic tubing, wasn't it?
From what I read, the only way to fit in the new titanium tubing is to dip the tubing in liquid nitrogen to make it shrink, put it in place and let it expand. Where do they get liquid nitrogen in the field?
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Not quite, MW. Some of the factory installations are tricky, but field replacements are straightforward, although the nacelles in particular are very crowded. That was one of the lessons learned from the December 2000 crash: ensure every line and wire bundle clears obstacles by the necessary separation--an extremely challenging task especially in the nacelle. Since then, factory assembly procedures and checks have reduced faults on delivery to a handful, down from literally hundreds of squawks per aircraft on early production aircraft.
The tiltrotor is not really that different in helicopter mode, except that got a very high disk loading. The V-22 actually enjoys a greater margin of sink rate between authorized (800 fpm below 40 knots) and loss of control (somewhere in the area of 2200-2300 fpm) than most helicopters (they enter vortex ring state or "power settling" at 1200-1300 fpm). But the consequences of VRS in a side-by-side tiltrotor are pretty drastic and deadly at low altitude. A tandem-rotor helo like the CH-46 or Chinook series would usually simply experience a hard/catastrophic landing from which survival might well be possible. A V-22 couples the roll into pitch and dives into the ground accelerating. Impact will always be catastrophic. But, that being the case, the caution among aircrews about screwing with the sink rate limit is almost religious. And the V-22 now has a Bitchin' Betty voice and a visual warning about sink rate at slow speed. Hard lessons.
TC
PS: Mongo tells me that whenever the heavies over there request transport, they ask for an Osprey first. Acceptance has pretty much been accomplished.
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Have you seen the artist's concept for the Quad tiltrotor candidate for the next-generation heavy lifter? It resembles two V-22s mating. =D
Supposed to lift 40,000 pound payload, with 50,000 desired. It will replace the Chinook in the Army and the CH-53K (still in development) in the Corps.
I've seen the drawings for the 53K. Big. Very friggin big. It is supposed to haul 27,000 pounds. 32 Marines fully equipped under normal conditions, or 48 Marines maximum. An S92 is big. A 53E is huge. The K will be ... impressive.
If you want to see weird, check out the X2 candidate (http://www.sikorsky.com/sik/Attachments/MISSION%20DOWNLOADS/X2_Technology_MissionBrief.pdf) for the Joint Heavy Lift. We did the first test flight of our tech demonstrator a month ago. Considering we're paying for the R&D out of pocket, kinda glad it's working as expected. Assuming it scales as expected, it'll be interesting.
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How goes the V-22 Osprey?
See, it's got these two really big propellers...
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Is the plane in which the X2's tail rotor rotates parallel with the airframe or perpendicular to the airframe? From the image it appears to be perpendicular to the airframe, a bit different than an ordinary helicopter.
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Is the plane in which the X2's tail rotor rotates parallel with the airframe or perpendicular to the airframe? From the image it appears to be perpendicular to the airframe, a bit different than an ordinary helicopter.
Perpendicular.
For the non mechanical engineer types of APS, any non coaxial rotor helicopter needs something to counter the conservation of angular momentum caused by the exerting torque on the rotor blades by the engine. Usually a tail rotor, but sometimes something novel like NOTAR (using Coanda effect to counteract the torque of the main rotor by routing fan exhaust through slots in the tail boom).
Another point of the coaxial design is to drastically reduce dissymmetry of lift, which causes one of the most fundimental speed limits on helicopters. Your advancing blade is moving into the wind, causing faster than normal airflow (thus greater lift). Your retreating blade has the opposite problem, it's moving with the wind, so less lift. Once you get enough of an imbalance, you get "retreating blade stall". In layman's terms, when you want to go faster than the warning labels tell you, the bird wants to flip itself onto the 'weaker' side and pancake the bird. That's bad.
BUT, when you have two blades going in opposite directions, they cancel out the dissymmetry. Well, they're supposed to. When Mr Rotor Tip takes a drive to Supersonic Aerodynamic Lane, unstability can occur. Tis why we're tossing a nifty FBW package. So that's why we think we can make this thing go 287.5 mph.
(Not to nitpick, but it technically doesn't have a tail rotor. It's a six-bladed pusher-type propeller, classed as "auxiliary propulsion") :angel:
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(Not to nitpick, but it technically doesn't have a tail rotor. It's a six-bladed pusher-type propeller, classed as "auxiliary propulsion") :angel:
Wasn't quite sure what to call it, so I went with familiar helicopter terminology. Thanks for the explanation... pretty interesting.
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I'd call it a Soviet Hormone on steroids, that's what. =D
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RevDisk:
Do the V-22 rotors/props turn toward the centerline or out ?
IOW, is the advancing rotor blade outboard or inboard?
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Article on Yahoo today:
ASAD AIR BASE, Iraq – After a troubled history, the V-22 Osprey — half-helicopter, half-plane — has been ferrying troops and equipment across Iraq for just over a year without a major incident.
Critics say the Osprey, which was designed to replace transport helicopters, lacks firepower for defense in heavy combat.
But pilots say the Osprey makes up for that in speed, which one of them says can take the plane "like a bat out of hell" to altitudes safe from small-arms fire...
http://news.yahoo.com/s/ap/20081020/ap_on_re_mi_ea/ml_iraq_bats_from_hell
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RevDisk:
Do the V-22 rotors/props turn toward the centerline or out ?
IOW, is the advancing rotor blade outboard or inboard?
Sorry, don't know re V-22. Tis a Bell product. I think I know someone who worked on the production line, I can ask.
I don't know tiltrotor aircraft as much as I do ordinary rotor aircraft. Oh, and the standard disclaimers. I am not a mechanical or aeronautic engineer, just a computer geek that works for an rotorcraft manufacturer. =D
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One of my guys who was just over there liked the aircraft but wasn't thrilled with the "tail gunner" concept of a guy on the ramp with a suspended MG. Apparently it is a risky place to be in a crash.
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The V-22 proprotors counter-rotate, with each rotor blade arcing downward next to the cockpit. That was a survivability consideration: in a crash landing in airplane mode, the proprotors "broomstraw" on impact, thus avoiding the unpleasant phenomenon of shrapnel slicing the nose off.
The ramp-mounted SAW was an interim measure in the face of estimates upward of $1M per aircraft to equip it with any one of several concepts for a defensive weapon with 360-degree coverage. Since the tactic when encountering unexpected hostile fire in an LZ is to turn away, go to full power, rotate nacelles and scoot like the proverbial bat, the rear-aspect ramp gun is not totally useless. In ant event, the V-22 will pretty rapidly open the range plus creating a changing azimuth/elevation sight picture for bad guys.
AFSOC is testing right now a palletized gun system that "plugs in" to the hellhole and is operated indirectly by a gunner in the cabin.
TC
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So now the Marines can exit the field of combat at a high rate of speed -- just like the Air Force. :lol:
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Doesn't the Chinook use a ramp mounted saw or '60, too?
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Doesn't the Chinook use a ramp mounted saw or '60, too?
M240, usually. We don't use M60's that much anymore.
You can also mount a M134 or a M240 in the door just behind the cockpit.
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History channel did a show or two on the Chinook fire support aircraft used in Vietnam. I wonder if someone is trying to see how that would fit in an Osprey.
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History channel did a show or two on the Chinook fire support aircraft used in Vietnam. I wonder if someone is trying to see how that would fit in an Osprey.
Somewhere (I think it was wikipedia) I read that they were thinking about putting a GAU-19 turret on the nose of the plane to provide better defensive firepower, but the project was canceled. Don't know if anyone is thinking about reviving those plans or something similar.
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BAE is developing and testing for AFSOC a palletized GAU-2B for their CV-22s. See here: http://www.freshnews.com/news/defense-west/article_42132.html?Aerospace (http://www.freshnews.com/news/defense-west/article_42132.html?Aerospace)
The testing is ongoing at Eglin, and they've run into some glitches mainly in the area of software and human factors. Part of the challenge is getting a gunner who is strapped into a fixed seat to operate the gun via joystick over a 360-degree field of fire. In a moving aircraft. Day, night, bad weather. Not a simple problem.
TC
Edit to add: the pallet goes into the "Hellhole" in the belly of the cabin.
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I am not a mechanical or aeronautic engineer, just a computer geek that works for an rotorcraft manufacturer.
Same sort of deal with me - I wrote ground maintenance software for jet engines, both fixed and rotary wing a/c. Now doing support for testing/certification (traceability and coverage analysis).