Cessna 172R stall speed wrong?

[AKar]

Ron,

I'd say our consensus was definite maybe. While I still haven't been able to install A2A planes to my fresh P3D installation, tests done by others seem to suggest that both the actual and indicated speeds differ a little bit from book values. Whether or not this makes any practical difference to anyone's purposes (and how accurate those book values themselves are!) is a topic of its own, so far the discussion has been refreshingly academic.

-Esa

[DHenriques_]

Ron,

I'd say our consensus was definite maybe. While I still haven't been able to install A2A planes to my fresh P3D installation, tests done by others seem to suggest that both the actual and indicated speeds differ a little bit from book values. Whether or not this makes any practical difference to anyone's purposes (and how accurate those book values themselves are!) is a topic of its own, so far the discussion has been refreshingly academic.

-Esa

This for everyone;

Don't forget that at the extreme end of the lift curve at CLmax, as the area just in front of stall is reached, ANY and I emphasize ANY pitch input even the slightest bit applied will raise the stall speed into an above 1g stall wich is in effect accelerated.
Even in real life it is extremely difficult to achieve a true stall at 1g.
In any normal landing or even doing normal stalls at altitude, the actual stall break will usually occur a bit off the painted white line at Vso.

Dudley Henriques

[AKar]

Very true, Dudley. In the sim we've got the luxury of perfectly smooth air also, if wanted. All this is why I brought up the question if any possible discrepancy noted here has any practical consequences whatsoever - in the sim world it is easy to get too clinical in thinking when compared to reality, where all the figures have certain variances around them. In reality, I'd figure any such numbers would get determined from several tests. Though with today's instrumentation one can get extremely well documentated test results, but certain uncertainties must still apply.

-Esa

[DHenriques_]

Very true, Dudley. In the sim we've got the luxury of perfectly smooth air also, if wanted. All this is why I brought up the question if any possible discrepancy noted here has any practical consequences whatsoever - in the sim world it is easy to get too clinical in thinking when compared to reality, where all the figures have certain variances around them. In reality, I'd figure any such numbers would get determined from several tests. Though with today's instrumentation one can get extremely well documentation test results, but certain uncertainties must still apply.

-Esa

I agree. I would only add that with Accusim, Scott and the team have actually created a much closer relationship between the sim aircraft and the sim environment. The guys have worked virtual miracles with this.
With Accusim we actually have variables and random behavior between the airplane, its instrumentation, and the aerodynamics surrounding these elements. The way things interact with the standard atmosphere has been changed by Accusim.
We are not quite there yet but we are getting VERY close to what I call the "Frankenstein" level with Accusim .
Dudley Henriques

[Ron Attwood]

in the sim world it is easy to get too clinical in thinking when compared to reality

This was the very thought that furrowed my brow whilst reading this thread.

It also occurred to me that even in real life these 'numbers' aren't carved in stone.

Nevertheless, an interesting discussion and one conducted with such civility. Makes a nice change.

(I'm not really a pilot )

[Nick - A2A]

Dudley - yes I can definitely see how this will affect our ability to 'get to the bottom of the white arc' which was the original topic of this thread, especially with the rather sensitive (cheap 'n' nasty in my case) flight sim controllers that prevail.

However, if we leave Accu-Sim IAS and airspeed indicator error out of the equation for a moment (and just use the ctrl+z "IAS" = CAS), it does seem that the C172R at full flaps and MTOW is capable of flying just a wee bit slower (~5 knots) than the POH suggests. As mentioned in this post, I tried the same test with flaps up and here the stalling speed was a perfect match for the POH (51 KCAS).

In other words, the full flaps setting in the A2A C172 seems to be slightly too efficient at delaying stall onset: we'd expect it at 47 KCAS but in my tests it didn't happen until about 42 KCAS. However, as mentioned in the other post I linked above, I appreciate that this could be a deliberate compromise to help simulate ground effect/float. If not, maybe it is responsible for any slightly exaggerated tendency for float though?

Thanks,
Nick

... we are getting VERY close to what I call the "Frankenstein" level with Accusim .

Yes - no argument there!

Nevertheless, an interesting discussion and one conducted with such civility. Makes a nice change.

I know Ron - aren't we Accu-Simmers a polite lot!

[AKar]

in the sim world it is easy to get too clinical in thinking when compared to reality

This was the very thought that furrowed my brow whilst reading this thread.

It also occurred to me that even in real life these 'numbers' aren't carved in stone.

Nevertheless, an interesting discussion and one conducted with such civility. Makes a nice change.

(I'm not really a pilot )

Yes, it has been a great topic. And I must add that it is fun and educational to 'challenge' the simulations we've got, but this has also been a good example of topic where no angry sides have been taken. I agree with Dudley in that these simulations of imperfect, man-made machines are really virtual miracles. While perhaps the speeds are off enough for one to notice the difference in the current version if looking for it, it is good to know that these variances noted in this topic are not beyond normal pilot or environment induced variances by that much really. And I've got no reason to believe that they wouldn't be brought closer to the actuals should such a discrepancy get documented. These planes have proved to be great investments. And this is not to say that these findings wouldn't be substantial and backed up by some data, just to say that I don't think that any one of us who've participated the discussion have any intention to blow this out of proportions.

-Esa

[taildraggin68]

This has been a very good discussion.. I really enjoyed the mis-rigging of the initial 182, so any variances in stall speeds in the 172 are just an example of "personality" or "character" you might would find in any aircraft. It is a direct byproduct of accusim. I await the discussions that will surely be had once a twin-engined accusim aircraft arrives