Ummm, is the possible?

[FLS]

Hmmmm hmmm hmmmm. Just quivering with anticipation aren't you. Oh yeah, this is really a serious question and not a screaming rule number 4 violation 

What is the .5g stall speed of the F4U-1 on the deck with 25% fuel and 3 notches flaps?

[Skyyr]

He's not flying sideways. He flick stalled it, slid sideways, recovered the stall and flew off. He was flaps out at less than 1g. What do you think his stall speed was?

As BnZs said, it's the extremes that are hardest to model, and it's the extremes of flight envelopes that show where discrepancies in the flight model exist.

I'm just as giddy as the next guy for fully-realistic aerodynamic simulations, but the torque modeling and spin characteristics are so out of whack that they almost don't resemble flight at all. It's simply not realistic. I could go into aerodynamics ad-naseum, but it'd be a waste of time for all parties involved. You think it's fine, years of flight experience say otherwise for me - we'll have to agree to disagree.

Also - that "G" meter is actually an airframe LOAD meter; it is not an actual G-meter. In unusual attitudes and orientations, it's all but completely irrelevant to stall speed.

[FLS]

As BnZs said, it's the extremes that are hardest to model, and it's the extremes of flight envelopes that show where discrepancies in the flight model exist.

I'm just as giddy as the next guy for fully-realistic aerodynamic simulations, but the torque modeling and spin characteristics are so out of whack that they almost don't resemble flight at all. It's simply not realistic. I could go into aerodynamics ad-naseum, but it'd be a waste of time for all parties involved. You think it's fine, years of flight experience say otherwise for me - we'll have to agree to disagree.

Impossible unrealistic flying that we see regularly at airshows.  

The load factor,  as shown on the accelerometer,  actually determines the stall speed, which so far nobody has bothered to figure out. Why is that?   




 

[nrshida]

What is the .5g stall speed of the F4U-1 on the deck with 25% fuel and 3 notches flaps?

The stall speed is irrelevant.

[nrshida]

The load factor,  as shown on the accelerometer,  actually determines the stall speed, which so far nobody has bothered to figure out. Why is that?   

Because it's irrelevant.

[FLS]

You don't know.  

If you want to criticize, do the math. 

[Skyyr]

You don't know.  

If you want to criticize, do the math.  

The burden of proof is on the person bringing the claim that what appears to be impossible and deviates from accepted parameters is, indeed, possible. You do the math.

[FLS]

I did the math Skyyr. Didn't you read page 1?  I posted an approximation but I know the speed I asked nrshida for.

I'm just curious who else can do it.    Waiting on nrshida and BnZs.  And Skyyr. 

And the burden of proof is always on the person criticizing the flight model. Based on his speed when he recovered the stall should he have been able to continue flying? Obviously the answer involves the stall speed. Did you all say it was wrong without even knowing the stall speed?

[nrshida]

You don't know.  

No I don't know. I dare say I could find the equation and do the sums quite easily if I had the data. Not rocket surgery is it.

I'm just curious who else can do it.    Waiting on nrshida and BnZs.  And Skyyr. 

Judas Priest could you be any more full of yourself? Not really here to discuss things in a helpful way are you. You get your jollies from quite a different activity. Is your trolling endorsed by the official Aces High Training Corps? I'm just wondering.

Anyway, once again the stall speed is irrelevant. You have nothing to contribute to this argument since all you can do is transcribe information, what with your crippling lack of imagination and bias. Let me guess, the Corsair is one of your favourites is it?

[mechanic]

I think that is a bit unfair Shida, being a trainer does not mean losing all sense of self and individual natures. All the trainers were their own person before being a trainer and the good ones continue being their own person while simultaneously offering their time to help anyone in any way possible.

I see nothing wrong with poking fun at each other in a friendly way, trainer or not.

[FLS]

No I don't know. I dare say I could find the equation and do the sums quite easily if I had the data. Not rocket surgery is it.

Judas Priest could you be any more full of yourself? Not really here to discuss things in a helpful way are you. You get your jollies from quite a different activity. Is your trolling endorsed by the official Aces High Training Corps? I'm just wondering.

Anyway, once again the stall speed is irrelevant. You have nothing to contribute to this argument since all you can do is transcribe information, what with your crippling lack of imagination and bias. Let me guess, the Corsair is one of your favourites is it?

Do you feel it's inappropriate to post in a thread just to vent some personal animosity?

[nrshida]

I think that is a bit unfair Shida, being a trainer does not mean losing all sense of self and individual natures. All the trainers were their own person before being a trainer and the good ones continue being their own person while simultaneously offering their time to help anyone in any way possible.

I'm allergic to people persistently bending the forum rules so they can forward their agenda of divine condescension while ensuring nothing they like ever gets changed even if it might be incorrect. If he's going to troll then he should expect the same treatment everyone else gets.

Do you feel it's inappropriate to post in a thread just to vent some personal animosity?

It isn't personal, I don't know you or care about you. It is a 'professional' objection to your consistent conduct and agenda on this forum which prevents progress through any constructive discussion. I think it's inappropriate for you to continue do this, doubly so since you are a trainer who is supposed to contribute constructively and actually be interested in a faithful representation of modeling instead of taking the default argument it is perfect as it is without enquiring what people might have found out or thought of. I refer you to GScholz's recent P-38 dive flaps discussion for the previous example of your monkey business.



So in answer to your question:

What is the .5g stall speed of the F4U-1 on the deck with 25% fuel and 3 notches flaps?

I did the following sums. I had to make an assumption and might indeed have made a schoolboy's. No doubt corrections with considerable laughter will follow but who cares if being corrected by you is the only way to get more accurate data, since you never come forward with it only to correct someone.

This is the equation I used:

V = sq root (W x 9.81/(1/2p x S x Cl_max))

Where:
V = Stall speed m/s
p (rho) = air density kg/metre^3
S = wing area metres^2
Cl_max = Coefficient of lift at stall
W = weight kilogrammes

I couldn't find Cl_max for an F4U1 with three notches. I tried to determine it through flight testing and got a power off stall speed of 74 mph with three notches based on an average of 12 samples but the units weren't specified for the equation and the data spurious when I tried.

I found two different values for it with full flaps (that's five notches in AH). I also didn't know how to allow for a 0.5G load so I made an assumption. I took an estimated weight with 25% fuel to be 4351kgs. At 0.5G I assumed it to be reduced by the sine of 45 degrees so 4351 x 0.707 = 3076.157 = 3076 kgs. It just felt right because I didn't feel it would be a linear value between 1.0 and 0.


Version I - Brooke's Cl_max 2.74
V = sq root (W x 9.81/(1/2p x S x Cl_max))
V = sq root (3076 x 9.81 / ( (1.225 / 2) x 29.17 x 2.74) )
V = sq root (3076 x 9.81 / ( 0.6125 x 29.17 x 2.74) )
V = sq root (3076 x 9.81 / 48.9545525 )
V = sq root (30175.56 / 48.9545525)
V = sq root (616.39946560639074)
V = 24.82739345171762 m/s
V = 55.5372974 miles per hour

Version II - Some random site citing some manual Cl_max 2.30
V = sq root (W x 9.81 / (1/2 p x S x Cl_max))
V = sq root ( 3076 x 9.81 / ( (1.225 / 2) x 29.17 x 2.30) )
V = sq root ( 3076 x 9.81 / ( 0.6125 x 29.17 x 2.30 ) )
V = sq root ( 3076 x 9.81 / 41.0932375 )
V = sq root ( 30175.56 / 41.0932375 )
V = sq root ( 734.31936337456984 )
V = 27.09832768593977 m/s
V = 60.6172327 miles per hour


So with full flaps at sea level with a 0.5G loading the stall speeds are either 56 mph or 61 mph depending on which Cl_max value you use.

And?

[mechanic]

I'm allergic to people persistently bending the forum rules so they can forward their agenda of divine condescension while ensuring nothing they like ever gets changed even if it might be incorrect. If he's going to troll then he should expect the same treatment everyone else gets.

Fair enough mate, I think I was only looking at the small picture in reference to the bit you quoted with the smiley faces or whatever. I wasn't paying attention to any on going disputes. Which is unlike me actually, I'm usually a big picture kind of guy. This is one big picture situation I'm going to stay clear of. 

[FLS]

When the stall speed is 60 mph, recovering a stall at 68 mph doesn't look like a flight model problem. 

[FLS]

Fair enough mate, I think I was only looking at the small picture in reference to the bit you quoted with the smiley faces or whatever. I wasn't paying attention to any on going disputes. Which is unlike me actually, I'm usually a big picture kind of guy. This is one big picture situation I'm going to stay clear of. 

The dispute is simply nrshida harassing me with baseless accusations that ironically fit his own behavior.
I try to keep him on topic.