Corsair Turning Ability in AH

[SgtPappy]

This thread is still alive?
Bump! heheh.

[dtango]

Knegel:

"The definition of insanity is doing the same thing over and over again and expecting different results."  

I now realize that I'm stuck in this loop thinking if I try to reason with you with all the different ways that I know how you will see the aerodynamics.

I would continue try to answer your questions and objections but I'm convinced now that you really aren't interested in understanding the aerodynamics.  Instead you have an agenda which presupposes that the AH flight model is wrong and are looking for anything to grasp in order to prove this.

You are demonstrating the classic signs of selection bias:
[list=1]

• You are cherry picking concepts that you think support your position vs. trying to understand the whole.  I have purposely avoided dissecting the thrust angle issue because I'm not out to discredit you by pointing out where you're wrong about this.  Now you bring up rudder drag to offset sideforce as another "proof".  This only shows that you don't understand the fundamental relationships for turn rate in this equation

and how the variables in the equation themselves change.

I could bring up a bunch of other things like the impact of viscous separation, lift degradation due to compressibility effects at moderate airspeeds with high aoa, differentials in airspeeds between the outboard and inboard wings in a turn, etc etc.  

I don't because they wouldn't serve any purpose but to confuse people.  I enjoy posting about aerodynamic topics because I like to understand the "why?" and want to help others to understand the "why?"  too.  It serves no purpose to drill into details that only obscure the central principles.

• You are misinterpreting the F2A-3 report by only picking parts of it that (you think) support your argument but have ignored and continue to ignore the parts that don't.

Aerodynamically the bottom line is that we cannot conclude anything about turn-rate performance from steady climb performance which was your central point in believing something is wrong with the AH flight model.  I've tried to explain why in the best ways that I can.

And BTW, I'm glad you found the Naval Flight Test Manual.  There's great information there!  I've used it as a reference for years :).

Cheers!

Tango, XO
412th FS Braunco Mustangs

[nooblet187]

Originally posted by Knegel
Hi,

at a climb speed of 100mph, the full flaps AH F4U-4 elevator is absolut level, so the drag is perfect regarding this and also the wingtips stand good in the "wind".  At max AoA(around 75mph), the climb is worse.
The slower climb speed with full flaps result in a rather similar drag, like the same plane without flaps at 170mph, despite the drag coefficient got increased by the flaps and at same time the effective thrust is better at slow speed than at higher speeds.

One reason for the so much worse climb with full flaps must be the smaler thrust lift due to a disadvanced angle between airfoil and engine, while flying with full flaps. The engine points relative more downward in combination with fhe "full flaps airfoil", this is wanted to provid a better sight while landing. And the max AoA is also worse with full flaps.
Roundabout like this:

While climbing and turning at max AOA the discrepancy is most big, resulting in a smaler thrust lift.

Greetings,

Knegel

While full flaps are down, if you do not input any elevator control you will continue to do circles/loops until you stall and/or crash. This means the elevator while climbing must constantly push the nose down, this causes drag on the elevator. Which means a significant amount of lift from the flaps is being fought against.

Also with full flaps in a climb the plane is near horizontal which seems very inefficient when climbing, meaning airflow is going downwards on the wings causing drag.

[Knegel]

Hi Tango,

this was my initial argumentaion:
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"Another risk factor of steep turns is that bank angles beyond 30° rapidly increase the load factor and stall speed. For example, the load factor in a 30° bank is only 1.15 G with a 7.5% increase in stall speed. However, a 60° bank imparts a 2G load factor and a 41% increase in stall speed".

But our AH F4U-4 turn with less than 100mph, with full flaps and around 60 degree banking, absolutly alone, without the need to pull the elevator, only with a very smooth correction with the alerons.
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Another point of my argumentaion regarding the climb/turn-comparison was/is that weather the climb or the turn relation is wrong, but of course both could be wrong and lead to the discrepancy i still see.

Although the climb/turn results dont allow a exact conclusion, the different results give a good hint to the drag/lift relation at give speed. Since we can find the position of the max AoA in a graphic(look below) and cause we need a rather similar CL at same speed to overcome the gravity and cause the thrust is similar at same speed, we can see how the drag at this speed should look like.  



If its like this graphic show, then the F4U w/o flaps with 100mph climb at "C", while the full flaps F4U climb at roundabout where the both lines cross, resulting in a smaler drag for the full flap F4U and this should then result in a better climb ratio.
Now we have the disadvanced thrust angle with full flaps, resulting in a smaler thrust lift, but will this help the no flaps F4U so much, to overcome the full flap F4U by 30% regarding the climb ratio?

The turn in AH seems to follow the logic of this graphic rather close, whats about the climb??

The climb test with 100mph make me belive its rather this curve for full flaps:


Will it be possible to keep the turn ratio with full flaps with the relation of this curves??

My main point, a discrepancy between climb and turn, still remain from my point of view.

Believe me, i wanna see the whole and of course i pic the parts out of the F2A test that support my assumtion, the other parts already got offered here by you and others, to support your point of view.

So maybe its not only the turn that is not correct, but also particular the climb?


nooblet187,

with 100mph the AH F4U-4 100% fuel and full flaps provide a nice exact steady climb. The tail wing and elevator stand almost exact in one line then.

Of course i dont wanna climb with 170mph, at this speed there is a big nose up moment.

With 100mph, the no flap F4U-4(close to max AoA, big elevator input) climb better than the full flaps F4U-4.

Greetings,

Knegel

[nooblet187]

I already said in 100 mph climb with no flaps, you are limited by lift and power. Your using 100% power and 100% lift or close to it.
 
With full flaps at 100 mph you are using 75%( just a guess) of lift and 100% power. Therefore the flaps are adding drag, and lift you cannot use since your already at 100% power(well you could use the lift, just pull back on the elevator more even though you would slow down..).

In a turn you use 100% or close to it of the additional lift that the flaps add.

[TequilaChaser]

Originally posted by nooblet187
While full flaps are down, if you do not input any elevator control you will continue to do circles/loops until you stall and/or crash.

why would you continue to do circles/loops? what is causing it to loop?  trim?  Combat Trim?

Originally posted by nooblet187
This means the elevator while climbing must constantly push the nose down, this causes drag on the elevator. Which means a significant amount of lift from the flaps is being fought against. [/B]

if the elevator is constantly pushing the nose down, then how could you be doing loops as you stated in the 1st sentence?

the 1st sentence , sounds like you are using CT ( Combat Trim   turned on ), yet your second sentence cancels this out.........


 where are you getting your #'s? , data?, information? got any charts/URL links? NEVERMIND THIS QUESTION - NOTICED U USING X-Plane to find knowledge

looking for something to explain your statements, just reading it without pictures or  charts is hard to visualize.......

[nooblet187]

Originally posted by TequilaChaser
why would you continue to do circles/loops? what is causing it to loop?  trim?  Combat Trim?

The flaps cause the airplane to turn on its own.

if the elevator is constantly pushing the nose down, then how could you be doing loops as you stated in the 1st sentence?

It was just to say what the flaps are doing, and what you must do when climbing.

the 1st sentence , sounds like you are using CT ( Combat Trim   turned on ), yet your second sentence cancels this out.........

It was just explaining what you must do in a high speed climb because the full flaps keep pushin the nose up, just tested and even at 100 mph, the flaps are pushing up on the nose past the max climb rate with full flaps, meaning you gotta keep using elevators to point nose down.

[SgtPappy]

TC is like the God of aerodynamics math here, sooo I would not advise you saying anything against him.. but then again being wrong is one way of learning.

[Saxman]

Nooblet:

If you're having to manually push the stick forward something's not right. You should be able to trim the nose down to cancel out the tendency of the nose to pop up when you begin dropping flaps. I'm no aerodynamics guru and far from a math whiz, but I fly the F4U in here almost exclusively, and at no airspeed do I ever have to push the stick forward to keep the plane from flopping over on its back.

Now if you have COMBAT TRIM enabled as TC suggested, THAT will cause you problems. Combat trim tries to automatically trim your plane for level flight, one of the little allowances HTC has made to account for the fact that a real pilot would have trimming so second-nature he can trim without thinking, and also because we don't have the capability of "feeling" how the plane is handling and trimming accordingly. However if you're near stall speeds with full flaps deployed this will cause you problems because the aircraft's natural tendency is to lose altitude, so combat trim is trying to compensate by continuously trimming the nose up, which will generate the exact same effect you're describing. This is why using combat trim while trying to land the F4U is IMO a BAD thing.

However at low speeds once you have full flaps deployed, you can actually trim the nose so far down that you need BACK PRESSURE on the stick to maintain a nose-high attitude for landing.

This is the flaw in what you describe, because the elevators on the REAL aircraft wouldn't come into play keeping the nose down at all, only the trim tabs.

[TequilaChaser]

Originally posted by SgtPappy
TC is like the God of aerodynamics math here, sooo I would not advise you saying anything against him.. but then again being wrong is one way of learning.

ROFLMAO............that right there is the funniest thing I have ever read......

you must have me mixed up with the Elite engineers group

all I everwas,  was simply an  Aviation Machinist ( AD ) jet mechanic.......in my Navy career. different engine types I worked on were TF-34-GE-400B's, F-110-GE-400's, F404-GE-400's, TF-30P-414A's, TF41-A-400's, J-52-P-408A's, J79-GE-8B/-8C's  mainly the "O" level but had time in both "I" & "D" levels of maintenance as well.....
and I learn things everyday concerning the aero engineering , and I learn from this particular forum as well as other areas, but I am no aerodynamic mathmatical god by no means.......ROFL.......

dtango, Widewing, Brooke,  Hitech,  Badboy,  gripen, among some others are the  "gods of aerodynamics math" as far as Aces High is concerned.......

I simply could not understand his statement,  it was canceling itself out 1st sentance to 2nd setance.......

[nooblet187]

As my name suggests, its true when it comes to aerodynamics.

I never considered trim, but it should still be true that theres not enough power to use all the extra lift while it adds more drag.

[SgtPappy]

heh, well TC, your doing very well and a little idiot like myself who hasn't taken his gr 11 physics course yet needs a helluva lot to learn.  

I meant however, that you were our mathematician (in addition to Tango, of course) in this particular thread. Also that the 'being wrong and learning' applied to those who question you and Tango