Aircraft suddenly spirals out of any control

[david.jones]

Hi. I really hope someone can help. Running FSX on Win7 with the Saitek rudder pedals, yoke, 6xinstrument displays, 2 throttle quadrants.

I am flying a 747 quite happily ascending to 36,000 when suddenly without any warning, the aircraft dives, spins relentlessly and no control input makes any difference whatsoever.
This same problem also happens when I am flying Concorde (which is a plugin as opposed to the 747 which is the included software) - same story - in a steady climb, no adverse events - and suddenly uncontrollable disaster.

As no control input effects what happens, this must be a bug as there is no aeronautical reason why this should happen - but I have ABSOLUTELY NO idea what triggers it.

If anybody has any information I would be really grateful for your help.

[gspectre]

Be greatful that was not a real aircraft. I hear that's rare, in that it only happens in a carrer once ;)

As for the problem, I can only guess it might have somethingto do with your USB ports, maybe. It does not really explain the dropping and spinning (what sounds like a stall to a flat-spin) but if it happens again, pause the sim

and remove and replug your USB devices and see if they get re-recognized. Happened to my joystick once but my aircraft kept flying on Auto-Pilot, I just could not look around with the Hat-Switch.

[APUtech]

If this phenomenon usually occurs during climbout (ascent) check to that you're not retracting your flaps too early; many people do that because they don't know their aircraft's minimum no-flaps airspeed. If you're flying the default 747 I wouldn't recommend fully retracting your flaps until your airspeed is at least 230 kts. If your flaps are retracted prematurely during climbout, I guarantee that unless you reduce your pitch to increase airspeed to minimum no-flaps speed you'll end up in a nose-high stall, spin or tumble.

Also, your rate of climb may be too high for the power/speed setting that you're using during your climb, e.g., I fly the 747-400BCF cargo jet and I know that if she's fully loaded with cargo and fuel my initial rate of climb from liftoff shouldn't exceed 1800 fpm @ 200 KIAS. As her speed increases (and airspace speed limits allow it) I may increase my rate of climb to 2000 fpm @ 230 KIAS but usually I leave it at 1800 fpm until I get to around FL100.

I don't know the extent of your aeronautical knowledge, but as far as your saying that "there is no aeronautical reason why this should happen," I just gave you one. ;-)

APUtech

[david.jones]

Hi guys and thanks for your replies.

gspectre - thanks for your advice. you could well be right and I will try pausing during the next "crash episode" to see if there is a device that is somehow triggering this weirdness!

APUtech, again thanks for your advice. I'm a private pilot with a good deal of flying experience albeit in smaller aircraft. However, it's definitely not an issue with flaps or IAS as the strange phenomenon occurs in a controlled and gentle climb at +1000fpm with an IAS of 250ish. When I say there's no aeronatical reason for it happening, I meant that it seems to come "out of the blue" while in a very stable flying state - and there is nothing I can do to stop it or correct it once it happens. You'd think if there was a genuine stall etc that at FL100 that would be recoverable - but nothing I do stops the "descent" and the one notable instrument sign is that the DG just spins.... no control input will stop it spinning.

That's why I thnk this must be a bug rather than my bad flying (or a USB/hardware issue as gspectre points out). Obviously, I keep an open mind that there might be some "human error" here but I really don't think so on this occasion!

I'm definitely not an aviation novice and this event is just plain weird. I'm sort of getting to the point where I think I might just try a fresh install?

I'm guessing that this is not a known bug in FSX steam and that as the software is self-updating, it's perhaps more likely to be related to my setup rather than the software? Does that sound reasonable?

Once again, really appreciate you guys taking the time to help. Anything else you think I could try?

Best wishes from Oz,

Dave

[bobbi]

Perhaps your gross weight is too high for the altitude you're attempting. Try leveling off at a lower altitude for a while and attempting the higher altitude after your engines have consumed a few tons of fuel. You might even have to "step climb" like that more than once before reaching your final cruise altitude. To my understanding this is common and necessary practice on flights approaching the aircraft's maximum range.

Also note that some planes have a gross takeoff weight restriction that doesn't permit simultanious full load of passengers/freight/baggage and completely full fuel tanks. For near maximum range flights you might need to reduce your passenger/baggage/freight weight below 100%.

[JWNoctis]

Maybe switch to VC and check control input at the time - Sounds like something with the controller. They might be resetting or something like that. Used to have that happen to me if my stick's cable came off while on IL-2:1946, but as far as I know FSX is -usually- safe hotplugging controllers.

But also what bobbi said, though there should be some more obvious signs like incresing angle of attack and stick shaker before that.

[gspectre]

One way to confirm if it is indeed a Stall and not your equipment, as was suggested above, make sure you are in Virtual Cockpit view [F9] and if you move your Flight Control stick, the on-screen Yoke too should move. If that happens, learn how to recover from a Stall and Flat-Spin. If nothing on-screen reflects any movement by your controls, quickly press [Ctll]+[K] to toggle your Controller On/Off. If there is no change, Press [P[ to pause and reseat your controllers.

[APUtech]

Remember, too, that FSX is *not* a "true" flight simulator, and that aerodynamic principles have little to do with aircrafts' in-game behavior. I've had a few those catastrophic "out of the blue" moments of uncontrollability with FSX over the years, and more often than not (in my case, at least) they've occurred when I've had AP engaged.

[JWNoctis]

As far as I know, FSX's flight model is not known to be prone to instabilities. I've had exactly 0 loss of control events due flight model instabilities in my ~1000hr both on boxed and Steam. I do remember one time back with FS9, but that's due to me locking the aircraft into v/s climb over ceiling for aircraft weight, without being aware of either at that time. That being said, it's most likely not made for punching envelopes either and behavior at extreme ranges could be significantly off expectation, for all I know.

In fact, most of those full-motion sims they use for training and checkrides aren't, again as far as I know, designed to be fully accurate much beyond the edge of envelope, either.

And APUtech -- What is a "true" flight simulator, then?

[SteveFSX/P3D]

I would be tempted to turn all the realism settings to easy/off to see if this still happens.