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Helicopter simulation

2005-10-27 19:27:31.758641+00 by Dan Lyke 4 comments

I've built the helicopter controls and started flying the FlightGear Bo105 helicopter. Gotten pretty good at it, too, my hovering's a little shakey, and I'm having trouble holding forward flight altitude at speed at better than +/- 50 feet or so, but within the limits of my hovering I can do rudder turns, and fly sideways, and I'm starting to feel like I have some control.

At least in that flight model. And the FlightGear helicopter flight model is missing some critical bits, there's no downwash calculation, so there's no ground effect (and, less importantly but still an issue, no vortex ring state (VRS) issues), there's no engine model so you're blessed with 100% rotor speed all the time, but this also means that there's no autorotation, and the helicopter is powerful enough that I've hovered straight up 2,000 feet, which means that a whole set of issues with climb rate and such don't exist.

So I downloaded the X-Plane demo (6 minutes, then all the joystick inputs go to 0, with amusing results...), fired it up with their model of the Bell 206, tried to reset the controls and...

The problem here is that I've never been at the controls of a real helicopter. It's been many years, but I've felt the buffet of a stall in several different light fixed wing aircraft, I've felt rotation and the wheels getting light during take-off, I know what an approach and flare should feel like, I've held an altitude and direction with rudder turns and with the ailerons. And, frankly, most of the airplane simulators I've ever played with have been, to the limits of their model, relatively true to that fixed wing experience.

But every helicopter simulation I see starts with some basic similarities, and then is radically different from all of the other ones. I've done a lot of reading, I've been a passenger in a real helicopter once, but when the thing leaps off the ground with a very minimal collective input, and the cyclic lag doesn't seem to mesh with the numbers on the helicopters I've read, I start to wonder what's going on.

Everyone raves about X-Plane's fidelity to aerodynamics, and I can accept that it's my technique or something about how my controls are trimmed out or whatever, but parts of the experience are so completely different from those of FlightGear that I've realized I need to find an authority.

One of the reasons I stopped playing video games was that at some point in the last few levels of Tony Hawk's Pro Skater 2 I realized that I'd gotten all of the general purpose dexterity with a controller I was ever going to get, and the only thing that continued play gained me was getting better at Tony Hawk's Pro Skater 2. And I was one hidden area away from having seen everything in the game.

There is a lot more that I can learn about helicopter flight from any simulator that's applicable to the real world, but at some point many of the more difficult reflexive skills, like maintaining a hover, or being able to make the axis of a rudder turn around the mast, or the tail, or the nose, feel like they start to become more an exercise in learning a simulator than in learning flight.

And what I haven't found is anywhere that a real world pilot compares the helicopter flight model of, say, Microsoft Flight Simulator to that of X-Plane and FlightGear. I've seen several pilots talk about tuning the "reality settings" of MSFS to be fairly realistic (and I think most of those are using a third party model, like the Dodosim RealStart 206), I've seen comments which indicate that the X-Plane aerodynamics simulation is more true-to-life...

So, anyone got a suggestion about how to proceed? I don't, right now, have the budget to go drop a couple of grand on real world flight training so that I can then evaluate each of these simulators. The Hovercontrol.com folks have a community built around Microsoft Flight Simulator, which I've wanted to stay away from for reasons of future platform (I'd hoped to not maintain a Windows XP box for very much longer), but there are real pilots over there who seem happy with that. I could add basic ground effect calculations to FlightGear fairly simply, although I'm not up to more complex rotor downwash aerodynamics yet.

And, frankly, I'm seeing enough code during the day that if I'm going to be building stuff to chase this as a hobby I'd rather spend that time working on something physical, like further improving my flight controls.

[ related topics: Games Microsoft Aviation Software Engineering Machinery Aviation - Helicopters ]

comments in ascending chronological order (reverse):

#Comment Re: made: 2005-10-28 01:29:45.775514+00 by: meuon

Option 1: It's time to 'hang' with some real helicoptor pilots, maybe tell them of what you are doing at home, show them pix, etc.. I've been on lots of chopper rides, even been under the Walnut Street Bridge in LifeForce, (a stunt George B. the Pilot lost his license for later) just by being in the right place at the right time.

Tell em you got the bug and ask honest questions and tell em you can't afford it right now, but maybe someday. Maybe they'll take you for some interesting rides, maybe 'feel' the controls a little (while they have full control).

Option 2 (more possible): Better Simulator Time. Can you swap some experience with other helicoptor sim builders? ie: Other nuts like you? See what they have going on, geet some feedback from them, and their simulators as well. In fact.. anyone got a professional level helicoptor simulator for rent by the hour? I found lots of places that do 'live' training..

Option 3: approx $10k for 45 flight hours and 40 hrs ground school for private license. Gotta dream.

#Comment Re: made: 2005-10-28 15:21:28.535737+00 by: Dan Lyke

Yeah, life's been hectic recently, but I've been meaning to go down to the seaplane dock in Sausalito where one of the local traffic helicopters flies from and gen up some conversations down there. Don't know if I can get a ride out of that, but I can probably get some cockpit measurements and discussions about control throws and such that'd help me build more realistic controls.

Option 3 is on the radar. Charlene's the one who's really got the bug, but doesn't really have the coordination, and one of the things that it'd be nice if this can do is train some of the hand-eye coordination that'd help with hovering. I'd love to have a barn with a pair of Helicycles in it at some point...

The other thing that's coming out of this is that I'm learning enough that I may be able to take incremental steps to add the additional features to the helicopter flight model in FlightGear. I've got a couple of big papers to read, and I still haven't dug into the source, but I think I'm getting a handle on the simplifications that people generally do to solve the downwash issues (short of a full fluid dynamics solver).

I've known one guy who claims to have flown the bridges in 'nooga in a Smith Mini (small aerobatic biplane), and he went out of his way to fly out to Bledsoe or somesuch, land at the far end of the field and tape over the numbers before doing it. Doing it in a large easily identified commercial aircraft whose owners have lots of reasons to cooperate with the authorities seems like... yeah, that'd end up in some discussions with the FAA.

#Comment Re: made: 2005-10-28 16:06:42.92589+00 by: Larry Burton

Check on a "discovery flight" with one of the helicopter schools. While I'm hearing prices of $500/hr for lessons around here discovery flights are usually much less and allow you to get a feel of the controls.

#Comment Re: made: 2005-10-28 16:29:41.850145+00 by: Dan Lyke

Thanks, Larry, I'll ask around. I have one friend who was well on his way to having his helicopter license before he groundlooped one of his other planes, and then got married, so I'll have to ask him where he was training. $500 sounds excessive, a JetRanger runs sub $300/hr, plus capital costs (which, for an aircraft like that is pretty high, but it's not like they lose much in resale) and an instructor... well... maybe, but I'm sure there's someone out there with an R22 who could train for at least $250 an hour less.