Re: [Flightgear-devel] Re: YASIM Options
On Mon, 28 Jan 2002 09:44:42 -, Richard Bytheway [EMAIL PROTECTED] wrote: I seeing on TV recently that they have only recently added full computer stabilisation to the Harrier. They had the presenter of the program (a qualified military pilot, but not on the Harrier) flying a two-seater. There was a switch to choose hover or normal flight, in hover mode the throttle controlled elevation and the stick was slip/slide direction control (much like the cyclic in a helicopter), in regular mode, the throttle did speed, and the stick did pitch and roll as usual. The comment was that this would leave the pilot more time to see, and deal with, other things like finding targets and staying alive. snip This is the VAAC Harrier and not (AFAIK) anything that's operational. http://beyond2000.com/news/Jun_01/story_1171.html DERA is now the government owned company QinetiQ (who run VAAC on behalf of MOD) and DSTL, the bit that remained in the Civil Service[1]. Rick [1] This is the bit I ended up in. -- David Farrent and Dougie O'Hara on the Cold War role of the ROC: 'What a world of sorrow is hidden in those few words - [Post attack] crew changes would have been based on crew availability.' ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Re: YASIM Options
I seeing on TV recently that they have only recently added full computer stabilisation to the Harrier. They had the presenter of the program (a qualified military pilot, but not on the Harrier) flying a two-seater. There was a switch to choose hover or normal flight, in hover mode the throttle controlled elevation and the stick was slip/slide direction control (much like the cyclic in a helicopter), in regular mode, the throttle did speed, and the stick did pitch and roll as usual. The comment was that this would leave the pilot more time to see, and deal with, other things like finding targets and staying alive. Richard It's really nice to play with it! I once watched a Harrier at an airshow. It didn't really look like it were difficult to fly. ;-) I assume that the real thing is stabilized by a computer, no? Otherwise we would read about crashed Harriers every day. Lifting off in fgfs is already a hairy operation. But turning (yawing) at the place seems impossible. Is this modeled? How is it done in a real Harrier? With steering jets, coupled to the rudder? This e-mail has been scanned for all viruses by Star Internet. The service is powered by MessageLabs. For more information on a proactive anti-virus service working around the clock, around the globe, visit: http://www.star.net.uk ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Re: YASIM Options
Melchior FRANZ wrote: Andy Ross wrote: There's also a complication with the Harrier. You'll need to map a joystick axis to the /controls/thrust-vector[0] property in order to work the thrust vectoring. Works also reasonably well when mapped to the low/high properties of a joystick hat switch. [:-)] I actually found that this wasn't very satisfactory. The problem is that the thrust vectoring is your foward-back control in hovering flight. A typical end to the approach has the aircraft going 30-40 kts as it approaches the pad. You then have to throw the nozzles to max deflection (which is 10 degrees forward) to slow down, then immediately put them back at 85 degrees* or so for hover. Doing this with up/down only is, well, hard. There's no feedback about where the position of the control is. A cockpit gauge could help that a lot, too. * The aircraft sits on its gear at about 5 degrees AoA. You need to land flat on the gear to avoid a nasty bounce on landing. I've been playing/practicing with the Harrier a lot recently. I really should write up a training guide or somesuch, for folks just getting into it. The learning curve on the VTOL stuff is nasty and steep, kind of like being a real life test pilot on the things. Loads of fun. I can *almost* reliably land vertically now -- but hovering still eludes me. It's really nice to play with it! I once watched a Harrier at an airshow. It didn't really look like it were difficult to fly. [;-)] Those damn professional pilots make it look so easy. They have a few advantages, though. In addition to much more sensitive controls and vastly better visual distance cueing (you can see things on the ground in a real aircraft, not so (yet) in FlightGear), they can feel the lateral accelerations as they happen. While hovering in the simulator, it's too easy to turn a degree or two of bank into a 10 kt. sideslip by accident, simply because you don't notice it in time. A real pilot would feel this happening. I assume that the real thing is stabilized by a computer, no? Otherwise we would read about crashed Harriers every day. The Harrier is actually a very old design. The early ones (I've modelled a Sea Harrier FRS.1) don't have anything but a mechanical control linkage. No stabilization systems at all. And they *do* have the worst safety record (by far -- something like a factor of two) of all active tactical aircraft in the U.S. military. Dunno about the record the Brits, Spanish, Italians, Indians or Thai have seen, but I suspect it's similar. Lifting off in fgfs is already a hairy operation. But turning (yawing) at the place seems impossible. Is this modeled? How is it done in a real Harrier? With steering jets, coupled to the rudder? Vertical liftoff works pretty well, *if* you get the nozzles pointed in the right direction. If you just point them all the way down you're actually pushing the aircraft backwards. The sudden reduction of braking force from the wheels at liftoff ends up creating a nose down moment and the aircraft pitches forward as it lifts off. Be careful out there. :) A saner way to get off the ground is the rolling vertical takeoff, which is actually the way it's done in real life. Deploy the flaps and the wheel brakes. Point the nozzles downward. Spool the engines up to 85% RPM or so (no more than that, or else you'll lose ground traction and the wheels will slip). Then, in one quick motion, point the nozzles forward and jam the thottle to maximum. After a few seconds (and ~100m of runway) you'll be at 65 kts; now angle the nozzles down at about 45-60 degrees. You're airborn -- retract the gear and gently ease the nozzles forward, retract the flaps at 240 kts or so. I'm not sure about your problems with yaw. It works for me. What you're probably discovering is that hovering is hard. :) If you're not moving at literally zero speed, the aircraft, being an aircraft, will try to weathervane into the wind. At anything more than 10 kts of sideslip, this yaw force will be higher than that pathetic little jets in the tail and you'll lose controllability. Other than don't allow big sideslips in hover, I don't know how to deal with this. The real aircraft, by the way, has a little weather vane in front of the cockpit for exactly this reason. Hover into the wind, or else you'll die. Andy ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Re: YASIM Options
On Sun, 27 Jan 2002 13:48:44 -0600 (CST), [EMAIL PROTECTED] (Jon Berndt) wrote: It's really nice to play with it! I once watched a Harrier at an airshow. It didn't really look like it were difficult to fly. ;-) I assume that the real thing is stabilized by a computer, no? Otherwise we would read about crashed Harriers every day. Lifting off in fgfs is already a hairy One of the most incredible things I've seen an aircraft do was during some kind of celebration, like an anniversary of the Statue of Liberty, perhaps. Two Harriers (British craft launched from the Invincible?) flew at low speed up to the front of the Statue of Liberty, turned 90 degrees to face it, *bowed* (dropped the nose and returned to horizontal), then turned back and flew off. A very moving and spectacular maneuver. I'm almost certain the early generation (GR1/GR3/FRS1/AV8A) harriers don't have a stabilisation system in the hover and pretty certain the later gen (GR5/GR7/FR2/AV8B) don't either. Which version is the model based on? There are BIG differences between the various marks. Wing size and planform is different, LERX were added to the GR5 after delivery and thrust/weight ratio is improved on the later marks. Even the outriggers are in a different position. Oh, and there were a fair number of crashed Harriers in the early days, esp, I understand, with the AV8A - something to do with different pilot selection and training policies between the RAF and USMC I believe. BTW, one Farnborough airshow (98?) we were treated to a bow by SIX Harriers :) Rick -- David Farrent and Dougie O'Hara on the Cold War role of the ROC: 'What a world of sorrow is hidden in those few words - [Post attack] crew changes would have been based on crew availability.' ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
