P51D flaps use.......what am I doing wrong?

[Sparks]

Well I'm no Pony expert but I certainly use flaps a lot as I have a genetic tendancy to low down knife fighting ( comes from being a Spit dweeb ).  

Once committed to a turn fight I will be popping flaps in and out basically dependant on airspeed - below 200 1 notch - as it goes toward 160/180 2 notches and below 3 notches.  As Grem said though , don't expect to get out quick.

I have even gone to 4 or full going over the top of a real slow loop because as long as you are gentle with the ailerons it will mush over quite nicely with ridiculously low airspeed showing - I'm sure at some point partly stalled but it will start flying again quickly with everything hanging.

The beauty of the 51 I've found is actually it's excellent speed control and roll rate which I find it maintains all the way down to stall you can actually surprise people but don't do it i a crowd

Sparks

[ICKID]

FLS, you stated:

"Flaps change the wing incidence giving you a higher AOA for the same pitch angle. That's why it seems like flaps give you more lift. The lift actually results from the increased AOA. Flaps do increase the coefficient of lift allowing a higher AOA and lower stall speeds. The lower stall speed allows a slower tighter turn."


I think if you check you will find that Flaps produce more life because of increased wing area when depolyed, Angle of incidence, AOI is a constant and would only change if the entire wing moved.    Angle of Attack, AOA, is controled by the pilot with the stick.  Lift is the direct results of Wing Area, Wing area can be increased or decreased with flaps, the end result is your wing area what ever it is produces so much lift, as a result of being moved through the air (airspeed) producing lift.  For the wing to produce excess lift you need to move it at a certain speed. remember thrust vs drag, Lift vs weight. the wing flys because of excess lift, and turns because of excess lift, trun radius (turning rate) is directly related to speed.
The faster you go, the longer the turn radius,  the idea behind a low speed turning fight (rolling sissor) is to slow down to gain positon behind the nme  that is currently parked on your 6.

The purpose of Flaps is to increase your angle of desent without the resulting increase of airspeed from lowering the nose, ie...approach for a landing.

[Blue Mako]

Flaps increase wing CAMBER.  Camber is the amount of curvature of the wing looking from the side (ie. the wing chord).

The AIAA Aerospace Design Engineers Guide states "Generally they are used to increase the wing camber or in some other way to control the flow over the wing...  Wing flaps increase the camber at the wing trailing edge, thus inducing a higher lift due to increased circulation at the same angle of attack as the plain wing."

Trust me, I'm a professional.

[Blue Mako]

From another thread:  http://www.p51.mustangsmustangs.com/p51accidents.shtml

Check this site out if you doubt that WW2 fighters (and ponies in particular) are difficult to fly...

[FLS]

Only Fowler flaps increase the wing area when deployed.

It's certainly true that flaps increase the camber but that doesn't tell Swoop why he stalls when he's riding the stall horn and deploys flaps.

When you change the angle of the flaps it effectively changes the incidence of the wing section as well as increasing the washout. You actually stall at a lower AOA relative to the airframe with flaps deployed. Since the wing has a higher AOA with flaps deployed it's closer to the critical AOA without any pitch change of the airframe. That's why deploying flaps on the verge of a stall, i.e. at the critical AOA, will cause you to stall. If you reduce the AOA from the critical AOA when you deploy the flaps you won't stall.


--)-FLS----
Musketeers

[Blue Mako]

Originally posted by FLS
Since the wing has a higher AOA with flaps deployed it's closer to the critical AOA without any pitch change of the airframe. That's why deploying flaps on the verge of a stall, i.e. at the critical AOA, will cause you to stall. If you reduce the AOA from the critical AOA when you deploy the flaps you won't stall.

FLS,

I was just trying to clear up a misconception rather than answer Swoop's initial post...

Your response is pretty good but not entirely accurate.  The thing you neglected was that when you deploy flaps, the critical AoA of the wing changes because you are changing the properties of the wing aerofoil.  The critical AoA will increase as flaps are deployed, thus it will not necessarily stall the aircraft to keep it at the same AoA relative to the aircraft fuselage.  Most flaps produce a nose down pitch change when deployed (due to the centre of lift moving aft) and are thus stable anyway.

What Swoop describes is not extendinging the flaps when near the clean stall speed but riding the stall horn with flaps deployed.  It is most likely that he is overcontrolling the aircraft, putting it into a stall (and resulting spin) that is unrecoverable.  I have not found it a problem to ride the stall horn in the pony but it is very easy to snatch it into a spin while doing so.

(I know you have been flying for a while Swoop so ignore this section if necessary, maybe newbies will read this though)

My advice to you Swoop (as a dedicated pony driver) is:

Ease up on the stick and avoid turning the pony, it's not designed for that.  The laminar flow aerofoil used on the pony's wing is very prone to accelerated stalls and using a notch of flap makes the wing work a lot more inefficiently; you'll get it to turn but you'll get into the wrong end of the speed range real quick.  In short, stay high and fast and don't try to outturn anything.  If you can't resist the temptation and you do, you'll almost always end up dead unless you have a wingman to save your butt.

If you can't resist the temptation to turn that beautiful silver beast, go offline for awhile and practise max rate turning and spin recovery.

The best method is to climb up to about 10k and enter a spin (throttle closed, nose up, boot the rudder).  Let it develop for a full rotation then practise recovering.  The best recovery technique is to apply about 50% throttle (to get your control surfaces working) almost full forward stick (depending on severity of spin) and opposite rudder.  As the spin recovers, gently release rudder (first) and forward stick (gently or you will snap back into a spin).

Gradually step the start height down until you can recover from a spin at tree top height.  With practise you will recognise the spin as it starts and recover before it develops.

[gavor]

Don't listen to Mako. He's an amateur of such epic proportions he stopped playing AH in disgrace.

[FLS]

Blue Mako

I think you're correct that I was mistaken but I'm not convinced it's for the reason you gave.

I think what I neglected is that when the lower critical AOA with flaps deployed is exceeded the coefficient of lift is still higher than the coefficient of lift at the higher critical AOA of the wing without the flaps deployed.

As far as I know if you combine slats and flaps then the critical AOA is increased but when flaps alone are used the critical AOA decreases.

I believe that whether the nose goes up or down when flaps are deployed generally depends on the aircraft design. Of course I have no idea how HTC models lift and flaps and flight sims don't have to behave like real aircraft.

I may well have misunderstood what Swoop meant when he said " But the second I deploy flaps I spin." I tend to assume pilot error first but I was speculating why flaps might cause stalls. In testing I don't see any tendency to spin when adding flaps while riding the stall horn so I should have taken more time to consider my response.


--)-FLS----
Musketeers

[Andy Bush]

BM

I see nothing in that link to suggest that Mustangs are "difficult to fly". After reading the fatals, I get the impression that inadequate training, pilot errors, and unseen obstacles were the problems...not hard-to-fly aircraft.

If this were the case, how did all those low time WW2 pilots ever make it into combat? One would think they would all be smoking holes long before they ever got to where the action was.

One question...I'm a little unsure what you mean here:

>>The critical AoA will increase as flaps are deployed, thus it will not necessarily stall the aircraft to keep it at the same AoA relative to the aircraft fuselage.<<

Is this a statement regarding the effect of flap extension on the chord line? Or are you saying that flap extension allows a higher stall AOA?

[ICKID]

FLS,

AOA or Angel of Attack is the angel formed by the difference between the Relative Wind and the Cord line of the wing.  The Cord line cannot be changed it is designed into the wing.  The RW is always sticking the wing head on except when the pilot moves the stick and momentarily changes the angel.  That change in angel is what is called the Angel of Attack or AOA.  The wing stalls because the airflow over the wing is disturbed and the wing no longer produces lift.  Flaps and slats, when deployed, help keep the airflow from stalling.  The stall buffet normally produced when a wing approaches a stall, is the buffeting of the wing surface form the disturbed airflow just prior to the stall.  Depending on the stability of the aircraft design and military aircraft of WWII were required to be dynamically stable, not so for modern day fighters.  The movement of the nose of the aircraft at the time that flaps are lowered is predictable in dynamically stable aircraft.  If the pilot makes no control inputs and lowers flaps in a dynamically stable aircraft trimmed for straight and level, the nose will rise.  If that pilot then re-trims for straight and level and raises the flaps, the nose will lower.  The change in pitch is due to COL or Center of Lift, not to be confused with COG or Center of Gravity.  As the wing area changes (Flaps, slats), so does the COL.

Swoopy stalls because he exceeds the Angel of Attack.

[FLS]

I thought Flossy was the Angel of attack.  

IcKid you got a lot of it right, maybe this will help.

The chord line is an imaginary straight line from the leading edge to the trailing edge of the wing. Because the wing is typically twisted the wingtip has a different chord line than the wing root. Since the incidence is the angle of the chord line relative to the fuselage centerline the wingtip has a different incidence than the wing root. This is significant because the wing tip has the ailerons and the wing root has the flaps. It's convenient to consider the root incidence the wing incidence. The root incidence is useful to determine the AOA since the wing is twisted so that the root stalls before the tip. When the camber of the wing is changed by lowering the flaps the position of the trailing edge changes. Since the chord line is just an imaginary line from the leading edge to the trailing edge the chord line also changes when the flaps change the camber. Since the AOA is the angle of the chord line to the relative wind you can say that the flaps change the AOA even though the pitch attitude hasn't changed. The pitch attitude may change as a response to the flaps but the direction and amount of the change depends on the particular aircraft design.

--)-FLS----
Musketeers

[ICKID]

FLS,
None of this mean anything to a pilot in a dogfight, bottom line is Swoop stalled because his control movements exceeded the critial angel of attack , he distroyed the airflow over the leading edge of the wing.

[BigMax]

My cut (without the Physics lessons)...

Buy a Force Feedback Stick, you'll feel the stall before it happens and learn exactly how much applied force you can get away with. The stall horn is not an accurate representation of the airflow or lack-of being experienced by the wings...

'til then....

A Pony is a pure "E" fighter. Fly it any other way and death will find your six.

One other word of advice.  Don't make your Pony kill baddies, let it.

[Blue Mako]

Originally posted by Andy Bush
BM

I see nothing in that link to suggest that Mustangs are "difficult to fly". After reading the fatals, I get the impression that inadequate training, pilot errors, and unseen obstacles were the problems...not hard-to-fly aircraft.

If this were the case, how did all those low time WW2 pilots ever make it into combat? One would think they would all be smoking holes long before they ever got to where the action was.

One question...I'm a little unsure what you mean here:

>>The critical AoA will increase as flaps are deployed, thus it will not necessarily stall the aircraft to keep it at the same AoA relative to the aircraft fuselage.<<

Is this a statement regarding the effect of flap extension on the chord line? Or are you saying that flap extension allows a higher stall AOA?

Hehe Andy, I meant difficult to fly in that it isn't possible for your average Joe with 50 hours flying Cessnas to jump in and fly a high performance aircraft like a P51 safely.  I meant this to illustrate that when we grab a new plane here in AH we shouldn't expect to be able to fly it to the edge of it's envelope in a very short time, we have to train on the virtual planes just like the real ones.

As far as my statement about the critical AoA, I was trying to explain in a simple way (probably didn't accomplish this) that the lift properties of the wing change when flaps are deployed and that we can't expect the same values of critical AoA, maximum lift coefficient etc to stay the same as a clean wing.

I made the reference to the AoA relative to the aircraft in response to FLS's post.

Flaps allow the wing to develop greater lift at the same angle of attack as a plain wing.  Due to the change in wing camber, however, the lift properties of the wing are changed, depending on things like flow separation etc this can mean operation at higher angles of attack...  It all depends on the individual wing and flap setup.

[Blue Mako]

Originally posted by gavor
Don't listen to Mako. He's an amateur of such epic proportions he stopped playing AH in disgrace.

You just envy my pony...