Up up and away!

[Guest Robs]

Hi Guys,Has anyone ever done a helicopter for FU3?(or V22 or Harrier or similar VTO aircraft - not gliders in a headwind!)Would FU3 code even be able to accomodate this? Can you offset the engine thrust from forward?I am not an expert on the res files and flight models so perhap someone who is could answer!Rob.

[Hans_Petter 1]

I can't really give you a good answer but the real problem is in the flight model. Basically, a rotorcraft can't be modelled in any satisfactory way by tweaking the flight dynamics file for a winged aircraft. Even the FS 2002 flight dynamics for helicopters are limited but they're quite OK for the standard Bell. When flying a helicopter you tilt the mast of the rotor to change direction and angle of attack--it's more than a bit like ailerons and elevator combined. The tail rotor counteracts the torque of the main rotor and is controlled with "rudder" pedals. Then there's "translation" and that's a definite rotorcraft specialty. When you start moving forward you go through "translation" and gain more lift for a given collective (throttle) setting. Conversely, hovering requires more power. A layman's explanation is that once the helicopter moves out of its generated downwash the rotor bites into undisturbed air. While being caught in its own downwash the helo must overcome the downward rush of air as well as its weight. But there's more to it. A spinning rotor moving forward takes on wing dynamics, as if the spinning disk were a circular vane moving through the air. It's relatively easy to fly a helicopter, as long as you maintain a steady forward speed. However, once you slow down to a hover the flight dynamics change, with dramatic loss of stability. A typical practice flight will end in a hover that has the helo swaying violently from one side to the other, going backwards and dropping as a rock. The solution is to keep the nose down and creep forward, maintaining a minimal forward speed until you settle down. This is easier if there's some wind since then you'll creep "into" the wind and land with a positive airspeed.I'm a newbie helo pilot in FS2002 but I know enough to state that airplane flight dynamics won't work. We'll need a lot of "handles" in the flight physics file to get this right. Sure, we could always make an aircraft with terrific lift, high drag and low weight (as Captain Bazza's blimp) and float around slowly but it would still be an airplane. For those of you being familiar with the blimp you know that it needs some power / forward speed to stay up--that's because it's really a winged aircraft. BTW, talking of helicopters, we've got some AI helicopters flying around with rotors that are not spinning. These would look better if the non-moving rotor was simply removed. The best solution would be a semi-transparent disk for a rotor. If anyone has the source files for these AI helicopters it would be nice to give this a try.best regards,Hans Petter

[Guest]

Hans: Would this also apply to VTO aircraft, such as the HARRIER ?> Jim

[Guest Rich Wren]

Hi Jim,The answer to your question is "yes and no". Vectored thrust aircraft rely on similar physical principles to helicopters during low-speed flight and are aerodynamic during high-speed flight. The Harrier for instance, transitions to full aerodynamic flight at around 60-80 kts. Below that it is reliant on the thrust generated by its engines to remain aloft. Much like a helo it is effectively sitting on a column of air, except that instead of changing the blade AoA you change the thrust setting and instead of tilting the rotor disc/using the tail fan, you use puffer jets to maintain attitude/direction control. As you transition to full aero flight though, you're using fixed wings instead of the rotor disc to generate lift.The problem with vectored thrust aircraft in FU3 is that to my knowledge there is no accomodation for it. I know of no available control in the sim that will allow you to turn the thrust vector from dead-ahead to straight up. You might be able to perform a basic simulation of minimal forward velocity flight, but you certainly wouldn't be able to replicate the Harrier's signature airshow stunt of nodding to the crowd.The physics involved in simulating helos is particularly evil, I have a colleague at work who studied it for his Aero degree dissertation and he says it's practically impossible to model accurately in real-time.Hope this helps,Rich.

[Guest]

Too bad that it's impossible. It sure would be fun setting a Harrier down on one of them carrier decks. > Jim

[Guest jonpoint]

Hans-Petter,I've tried this and the simple palette (which models must embrace) simply doesn't allow it - for me at least :-( I found that SOME partial transparency occurs but not enough. Maybe as you say, just remove the blades. Something I am trying on the Dash-8 (yep, there's an AI one as well!) is simply putting a couple of unfilled circles where the props are (ie just lines). I did the outer one in yellow and the inner one in black - it looks OK taxiing towards you and can just be seen at a distance. We could do a similar thing with the choppers although, as FU3 still models them as aircraft I'd rather replace them altogether with something more appropriate - like a Dash-8 :-beerchugBTW, from my mistakes with the GeeBee flight model I think you could 'fudge' a chopper but it wouldn't be that realistic. I tried some negative drags somewhere which resulted in the plane taking-off vertically as soon as you applied power! The trick may be to alter the engine orientation to vertical (almost). The torque will have you spinning like a top but a bit of 'opposite rudder' may help. One could presumably do something here with wash effects? Maybe something for a rainy day when I need a break from the Dash-8/racing package/models for Sanfran/737... ;)As you are now familiar with flight model editing, maybe you'd like to try some experiments with it?Jon Point*************************(effyouthree@hotmail.com)*************************

[Guest Robs]

Guys,The upshot of this was that the FU3 is unlikely to accomodate a helo.I wasn't expecting a full on model of the helo in ground effect and out of ground effect, being caught in it's own downdraft on fast descents and unable to regain lift, banking left on high forward speed, being pushed left with the anti torque (most cases!) or being dragged towards obsticles like cliff faces when hovering next to them due to the recirculating air......I was only seeing if a simple FS ish model could do.PS there is a harrier and V22 and helos in xplane- flight dynamics are fairly convincing but graphics in V5.11 (which is the demo I have are not - I don't have a USB joystick !!!)VTO is a tricky business- thats why in the JSF VTO version they need the computers to help make the plane flyable and thats why there ain't many.One thing I never understood was the harriers lack of speed - in a dogfighting situation this is serious because you don't have the run and hide version (or you do noone any favours by dieing today!).The massive engine power require for VTO surely mean plenty of oommpfff for speed?Robs.

[Guest Rich Wren]

Hi Rob,The speed restriction on the Harrier comes from two places, the lack of an afterburner and those huge air intakes.There are relatively few aircraft in the world capable of sustaining supersonic flight without afterburners, Concorde is a notable example, the F22 is another.The intakes need to be that size to get enough air into them at zero airspeed, but this causes real trouble in controlling the airflow as you approach the sound barrier. Jet turbines really don't like sucking in supersonic air so all aircraft designed for these speeds have to slow down the airflow before it reaches the fan. The following page does a far better job of explaining this than I can: http://142.26.194.131/aerodynamics1/High-Speed/Page7.html.There have only been two supersonic VTOL aircraft (to my knowledge). The F35 JSF is effectively a 3/4 scale F22 with a lift fan and greater thrust vectoring ability. The Russians built one too, this relied on the afterburner being rotated to the vertical for takeoff, they melted the tarmac from Farnborough's runway one year...Rich.

[Hans_Petter 1]

Robs wrote: I wasn't expecting a full on model of the helo in ground effect and out of ground effect, being caught in it's own downdraft on fast descents and unable to regain lift, banking left on high forward speed, being pushed left with the anti torque (most cases!) or being dragged towards obsticles like cliff faces when hovering next to them due to the recirculating air......I was only seeing if a simple FS ish model could do.Point taken but there must be a minimum of realism to make it worthwhile the way I see it--translation and ground effect are two of them. Otherwise we'll just be moving about in "slew mode", exploring the maps as we may do in FLED. FS2002 has a quite realistic and challenging Bell helicopter. There's a fair amount of freeware helos for the MS sims but they're all based on the Bell flight dynamics. I've spent hours learning to land the Bell and I've been quite frustrated by how difficult it is to get it right. After reading up on helicopter tutorials I know that it's difficult for a lot of the right reasons. A helo is inherently unstable until it gains forward speed and while it may look quite easy that's because real world helicopter pilots are skilled artisans. The ultimate challenges are to hover in a stable position and to put a helo down on a helipad. If we could get a proper model for FU3 we could have a lot of fun landing on top of buildings. I'm absolutely positive about the idea of getting a helicopter into our plnpile but we really need to have a thorough understanding of the FU3 flight physics to accomplish this. However, one advantage is that FU3 is good at modeling the weather and wind effects. After having floated over a lot runways with a Mustang lately it may seem that we do have ground effect. best regards,Hans Petter

[Guest juvat2]

Hi,I had always felt I was quite prepared for flying helicopters due to my many flt hours with Janes excellent flt models in Longbow Gold and Longbow2. The ms2002 one came easy for me, but the one in Fly!2. Man, that thing kicks my tail everytime. I've gotten better with repeated attempts, but it's been very difficult for me. Is Fly!2 'chopper flt dynamics more realistic? I figure it must be. I'm now able to lift off, and "fly" it but very wobbly. Precise control and maneuvering as I can do with LB and '02pro eludes me.Jim B.

[Guest Robs]

Rich,Seems that Helo's are missed in FU3. I take the point if it isn't fairly close in the flight dynamics then it is unlikely to classed rubbish by most users!I can fly them in FS2002 but I haven't added any wind yet to find out if the weathercock etc - the Jetranger is particularly susceptable to sideway movement on touch down - try a huey - they are more forgiving (not too much!)Anyway lets hope that another far sighted company can product a true open source all flying machines and all scenery flight sim that flys on a modest machine.Rob.