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V-22 Osprey "ground effect" question
In the publicity photo's of ship landing's the V-22 looks like one prop is
in "ground effect" and the other one is hanging over the side of the ship so it's NOT in "ground effect" Does anyone know how big of a problem this is? Does it limit the cross-wind performance? So even though it's vtol the ship has to be pointed into the wind etc? |
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V-22 Osprey "ground effect" question
Robert wrote:
In the publicity photo's of ship landing's the V-22 looks like one prop is in "ground effect" and the other one is hanging over the side of the ship so it's NOT in "ground effect" Does anyone know how big of a problem this is? Does it limit the cross-wind performance? So even though it's vtol the ship has to be pointed into the wind etc? It depends on the ship, but the Osprey has to deal with the same sorts of problems when hovering over buildings on land. The trick is that the pitch of the two props isn't fixed to be the same value so it can adjust for uneven lift. -HJC |
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V-22 Osprey "ground effect" question
"Henry J Cobb" wrote in message ... Robert wrote: In the publicity photo's of ship landing's the V-22 looks like one prop is in "ground effect" and the other one is hanging over the side of the ship so it's NOT in "ground effect" Does anyone know how big of a problem this is? Does it limit the cross-wind performance? So even though it's vtol the ship has to be pointed into the wind etc? It depends on the ship, but the Osprey has to deal with the same sorts of problems when hovering over buildings on land. The trick is that the pitch of the two props isn't fixed to be the same value so it can adjust for uneven lift. -HJC Navy Ch-46's deal with this many times a day as they resupply all the ships in the fleet from the biggest to the smallest. Not a problem. |
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V-22 Osprey "ground effect" question
"Robert" wrote in message ... In the publicity photo's of ship landing's the V-22 looks like one prop is in "ground effect" and the other one is hanging over the side of the ship so it's NOT in "ground effect" Does anyone know how big of a problem this is? Does it limit the cross-wind performance? So even though it's vtol the ship has to be pointed into the wind etc? Greetings Robert, We looked at this pretty hard, on the first sea trials back on the WASP, many years ago now with the FSD aircraft. As predicted by all the work-ups to the event(s), it's just a matter of a gentle cyclic input against the roll, with the rate of the input being proportional to the rate at which you're crossing the deck edge. The test pilots involved did it without having to think about it. In hover over the deck, at least in the old FSD birds, you could expect abut 1/4 inches of stick trim to cancel out the roll. It does not limit the effective cross-wind performance, as there is more control margin left even with that little off-set than required for all rated cross-wind conditions. Every knot of forward ship is a bonus, works just fine with zero knots ships speed. But your observation is correct, sticks centered on the deck will produce a roll-off to the left if not corrected for. Erk |
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V-22 Osprey "ground effect" question
Greetings Robert, We looked at this pretty hard, on the first sea trials back on the WASP, many years ago now with the FSD aircraft. As predicted by all the work-ups to the event(s), it's just a matter of a gentle cyclic input against the roll, with the rate of the input being proportional to the rate at which you're crossing the deck edge. The test pilots involved did it without having to think about it. In hover over the deck, at least in the old FSD birds, you could expect abut 1/4 inches of stick trim to cancel out the roll. It does not limit the effective cross-wind performance, as there is more control margin left even with that little off-set than required for all rated cross-wind conditions. Every knot of forward ship is a bonus, works just fine with zero knots ships speed. But your observation is correct, sticks centered on the deck will produce a roll-off to the left if not corrected for. Erk Speaking of V-22 FSD aircraft, I posted some pics of the #3 FSD aircraft. Photos were taken at the American Helicopter Museum in West Chester, PA. http://s20.photobucket.com/albums/b2...0Osprey%20FSD/ Includes exterior and some cockpit detail photos. Comments welcome. Don McIntyre Clarksville, TN |
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V-22 Osprey "ground effect" question: Cockpit stuff
"Don McIntyre" wrote in message oups.com... Greetings Robert, We looked at this pretty hard, on the first sea trials back on the WASP, many years ago now with the FSD aircraft. As predicted by all the work-ups to the event(s), it's just a matter of a gentle cyclic input against the roll, with the rate of the input being proportional to the rate at which you're crossing the deck edge. The test pilots involved did it without having to think about it. In hover over the deck, at least in the old FSD birds, you could expect abut 1/4 inches of stick trim to cancel out the roll. It does not limit the effective cross-wind performance, as there is more control margin left even with that little off-set than required for all rated cross-wind conditions. Every knot of forward ship is a bonus, works just fine with zero knots ships speed. But your observation is correct, sticks centered on the deck will produce a roll-off to the left if not corrected for. Erk Speaking of V-22 FSD aircraft, I posted some pics of the #3 FSD aircraft. Photos were taken at the American Helicopter Museum in West Chester, PA. http://s20.photobucket.com/albums/b2...0Osprey%20FSD/ Includes exterior and some cockpit detail photos. Comments welcome. Don McIntyre Clarksville, TN Brings back a lot of memories, thanks for posting the pictures. At the risk of droning, I'll point out some of the flight test unique items are clearly visible in the pictures. Starting with the picture of center console: The console is pretty different in the a/c today, one of the most obvious changes are that the two little screens in the center middle console (Tac/Nav control heads) have been replaced by a single large display, and the two keysets with a single one below the screen. The LCD display to the left of the attitude ball was the only back-up instrumentation in aircraft in the event the displays failed, along with the attitude ball. This aircraft, 13, I think was the one that flew back from a test flight with only these instruments working, up at Philly. Peasly, I think was the pilot on that flight, but that's going back a long time. On the LCD display itself is a maintenance sticker (round white dot) probably states that this unit is INOP. To the left of the LCD display is the flap handle, currently set it 'auto'. It pretty much stayed there unless you had a malfunction. Auto, 0, 20, 40, Full. Full was 67 degrees, down, mostly to get out of way of the downwash from the props. The small box with yellow lights and small knobs mounted on top of the glareshield is the Flight Test Instrumentation Panel, or FTIP panel. This turned on and off all of the data recorders on the sled in the back. It's right above the three fire-pull handles (LEFT/APU/RIGHT). To the left and right of the FTIP panel are the ABEC (Analog Backup Engine Controller) panels and status lights, one rubber on/off button with two 'FADEC FAIL' status lights to the left of the button, and a single 'ABEC ENGAGE' button to the left. Full Authority Digital Engine Controllers were new and unproven in the late 80's early 90's for this application, and there was much gnashing of teeth over their reliability. If both FADECS were to fail, (both lights illuminated) the crew could select the ABEC to cut the FADEC out of the loop and go to a analog command. As I recall it basically firewalled the engine. Never knew it to be used other than test to see if it worked on the ground. Now on to the 'Blottle', or, the TCL (Thrust control lever), clearly seen to the right of the center console. It's twin is just off-screen to the left. In the first couple of aircraft this controller moved much like the collective in a H-47, but the sense was reversed, so that pulling the grip up/back in a little arc was no power, down/forward was power. This caused some confusion with helicopter pilots, worked just fine with the AV-8 guys. A little elbow was rapidly milled for the junction of the Blottle and cockpit floor, that put a 22(? i think) degree twist into the linkages, and turned the movement into a nearly pure fore/aft movement, without the up/down. This helped a great deal. The modern aircraft have a completely different grip on the Blottle, (looks like the head from the monster in Alien, and the movement is a pure fore/aft motion, along a slight tilt, moves like a motor-boat controller). Nacelle control is the knurled knob in the thumb-slot, various other comm buttons, hook jet., etc. The really interesting thing on this control is the LTM wheel, set horizontally in the face of the grip. Rolls left, right, with a detent in the center (white line). This was the Lateral Translation Mode controller, a feature which I do not think made the production aircraft. It used the fly-by-wire system to command coordinated lateral cyclic inputs in both proprotor systems, and the a/c would slide in pure translation right or left, without body roll, at a rate proportional to the movement of the LTM wheel. It could also be used to trim the a/c at a fixed roll angle, for slope landings. A really neat trick to see the a/c hovering at a stable, set point of, say, 5 degrees bank angle, with the pilots sticks centered and feet on the floor. I think it got canned because it was not that useful, and added a lot of complexity to the control system. But it was fun to play with. Things to see in the Right Side Instrument Panel: Heck, still can't see if the elbow joint on the PCL is an add-on or a production run. It's hidden just behind the gray inertial reel for the harness protruding from the seat-pan. The empty instrument rack bolted on to the right side of the console looks like an afterthought, and it is. That's where the nose boom instrumentation displays went, airspeed, attitude, altitude, etc. These were used to calibrate and validate the digital system values. The T-handle protruding from the lower right of the center console is the parking brake, and I can't recall for certain what went into the well-worn hole just below it. I am going to say that's where the pin that safed the canopy jettison pryos was stored when it was removed, but I could have sworn there were two. I may be mixing that up with the ejection seat pins, which had different storage locations, on the first two aircraft. Yep, those went on overhead holders, that's the canopy pin holder. Overhead: Closest to us in the picture are the cabin light intensity controllers, the Night/NVG switch is visible between the knobs. Forward of that is the APU controller, with run/start/off/purge positions for the rotary. It's in stop. Forward of that is the Digital Flight Control system panel, with DFCS OFF select in the center, system A/B selects left and right. Forward of that is the Analog Back-Up Nacelle Controller, with which the pilot could override the Digital Controllers on the huge jackscrews that rotate the nacelles in event of a malfunction or failure. The ABNCs would move the nacelles at 2 degrees/sec as compared to the maximum rate of 7.5 deg/sec when digital. I don't think these were ever used other than to test their functionality. Forward of that panel are the engine control levers. Off/Crank/Start/Fly. Crank was to turn them for cooling, without fuel to purge them after un-starts. Pretty much just put the engines in START until they hit, oh heck, this is firing off way to many decayed brain cells, 88% rpm, then push them to FLY. Really automated. The rotorbrake is the small lever between the two levers. All the way forward are the hook controller for sling loads, and contingency power system. The crew could select contingency power and the DFCS would allow engine and transmission operations in excess of 100% for short amounts of time. Below that is the lonely wet compass, a relic of a different age. Erk |
#7
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V-22 Osprey "ground effect" question: Cockpit stuff
Erk,
Thanks for the great info. Really puts some life into my photos. Don McIntyre Clarksville, TN |
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