On Sunday 23 December 2007 20:28, Hal V. Engel wrote:
On Sunday 23 December 2007 11:13:03 Martin Fenelon wrote:
On Friday 21 December 2007 22:42, Dan Lyke wrote:
[snip]
I took the c172p up to 500 feet, cut the engine, pulled all
the way back on the stick (yeah, I know, it's not authentic,
but I have a stick, not a yoke), and as the speed dropped to
50kts or so the plane started into this sort of kite-like
sink, but the ailerons were still pretty responsive.
The stall 'g' break of the real thing is certainly missing too.
I can't get an 'autorotating' spin either.
Martin
Some of the available models do a better job of modeling
stall/spin/snap characteristics. The PA24-250 is one example.
But most of the models currently available for flighgear do not
do a good job of modeling stall/spin/snap characterisics. Some
aircraft should be particularly difficult to handle during a
stall. For example the P-51D has a very critical wing and should
be very difficult to handle when a stall occurs. But it mushes
stright ahead like a (very fast) trainer when stalled. There is
also no buffeting in most of the models when approaching stall.
On the other hand modern lower performance GA aircraft will in
general have very forgiving stall charaterisics. I have not
piloted a C172 but I have spent some time flying a Piper
Tomahawk. In the Tomahawk if you enter a (non-accelerated) stall
striaght ahead the ailerons will remain affective even after the
stall is fully developed and you are sinking at 1000+ feet per
minute with the yoke all the way back. I suspect that the C152
and C172 are not too much different in this regard. But a P-51D
and most other high performance aircraft should not act this way
when stalled.
Hal
There are a few of significant factors regarding stalls and
uncontrolled flight in flight-sims.
First, I guess, is the fdm itself. JSBSim, which is tables based,
can handle stalls perfectly if the data is available - but usually
it isn't. YASim on the other hand, which incorporates aircraft
geometry, has some capability built in to it and I've certainly
seen it work quite well. I played with an automated spin-recovery
feature in the SU-37 and didn't have any problems getting it to
spin - infact, it was because I was getting into so many spins
while trying some of the manuevers that the vectored thrust SU-30
series aircraft are capable of that I wrote it, so I didn't have to
keep resetting after crashing:)
Another factor is that simulated aircraft are usually perfectly
symmetrical aerodynamically whereas real aircraft are always going
to be slightly out due to slight manufacturing variations and
masses not being perfectly on the centerline. I've found that when
I've incorporated asymmetrical aerodynamic features e.g. an
appropriately sized fuselage element to simulate a wing-mounted
pitot probe, it does have an effect in stalls.
Lastly, the simulated air we fly through is uniform across the
airframe whereas in real life it won't be - there will nearly
always be slight variations which will cause a wing to drop one way
or the other.
LeeE
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