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
