F4u flaps

[Benny Moore]

Originally posted by bozon
Flaps, do not "improve" turning where you can sustain a turn without flaps. What they do is extend some of the flight envelope to areas that you can't reach without them due to angle of attack limitation. The price is very much reduced efficiency, meaning for every little extra lift you get, you pay with a much larger amount of drag.

In other words, flaps allow one to convert extra engine power into lift without increasing speed, and where you have passed the normal critical AoA. Yet even this contribution is limited since it has its own new critical AoA, even if you do have the excess power.

You are correct.  Fowler flaps are much more efficient than conventional and split flaps, but all flaps are ultimately less efficient (though obviously not always less effective) than not using flaps.

[Squire]

I also have to say that I feel something is off with flaps in AH in many of the a/c. Its bewildering to see an F4U with full flaps and landing gear lowered doing immelmans in a dogfight.

...I mean, find one real WW2 F4U pilot that wouldnt call that insane, and a ticket to be an oil slick.

Also, wing loading is wing loading, and the F4U had a higher wing loading than many lighter WW2 fighters. Higher wing loading means at a given G, you lose speed faster than a fighter with a lower wing loading. So a Spit IX pulling 5 Gs will say, drop 50mph after one 360 turn, where an F4U would drop 75mph, pulling 5 Gs (assuming same E state and alt). < Just an example, I dont have the data in front of me. The F4U would need to drop to a 4 G turn to remain the same speed, thus the 5 G Spit eventually "out turns" him, thats the mechanics of it.

...and Im not just picking on the F4U, like I say I think the flaps code in AH needs looking at with all of them.

[F4UDOA]

F4UDOA, how do you know that Dean's graph is wrong? And can you post corrections? Aside from that graph, I've seen another NACA graph comparing the F-4U, a few American airplanes, and the Spitfire. Once more the F-4U was on the outside. Unless you can convince me otherwise, I still believe that the F-4U has far too good of turning ability in the simulator.

Dean uses a wing loading divided by the clmax of each airplane to come up with his lift index.

FYI, Dean's information came from the 1944 JFC which was done over days. He calculated the clmax numbers from the 3G stall speeds. However there was no weight,power or flap condition noted.

I don't want to do every aircraft in his list but I will do two for contrast since the information is available.
 
From The POH (Pilots Manual)

1. F4U-1D 1G stall speed= 87Knots IAS or 85Knots CAS 97.8MPH at 11,300LBS

391*11,300LBS/ 97.8^2MPH * 314SQ Ft= Clmax

4418300 /  30033597

Clmax = 1.47  Dean's number is 1.48

The F4U is the only aircraft with the correct Clmax

2. P-51D Stall at 101MPH IAS and 106MPH CAS Note-With Wing racks attached

9,000LBS * 391 /  106MPH^2 * 233.19Sq Ft

3519000 / 26201228

1.34

This is a pretty basic calculation but can be done from any POH listing of WW2 aircraft.

Also Check the NACA reports server for report 829 The F4U is also approximately 1.48 and the P-51 is similar although you have to make sure you are looking at Cl numbers with the prop installed and no flap deployed.

I also have a report from a group of modern pilots in 1989 that has simlar results.

Always make sure you are looking at CAS not IAS (especially with the F6F) because many of these aircraft had huge errors to overcome in instrument readings.

I will post more when I can.

Thx

[Benny Moore]

Originally posted by Squire
Also, wing loading is wing loading, and the F4U had a higher wing loading than many lighter WW2 fighters. Higher wing loading means at a given G, you lose speed faster than a fighter with a lower wing loading. So a Spit IX pulling 5 Gs will say, drop 50mph after one 360 turn, where an F4U would drop 75mph, pulling 5 Gs (assuming same E state and alt). < Just an example, I dont have the data in front of me. The F4U would need to drop to a 4 G turn to remain the same speed, thus the 5 G Spit eventually "out turns" him, thats the mechanics of it.

No, no, no!  You are making the terrible mistake which most flight simulator developers and users always make.  It is the mistake of thinking that wingloading equals turning ability.  Wingloading is a moderately reliable indicator of an airplane's turning and climbing ability, but is far from the only factor or even the only important one.  Liftloading, aspect ratio, and a lot of other factors which I don't really understand (chord ratio, taper ratio, et cetera) all are vital in calculating wingloading.  They (and the Fowler flaps) are the reasons why the P-38 easily outturned the Me-109 in real life.  Ignoring those factors is also why the P-38 doesn't outturn anything in simulators.

[F4UDOA]

I do not buy the "its a gull wing so it works differently" argument. While the gull wing has some interesting properties, it was not such a stellar design. The simple (circumstantial) proof of that is that it hasn't been used since the need of getting the gears low enough to clear the prop has been removed.

Bozon,

I don't buy the gull wing arguement either.

The flaps provide alot of lift and alot of drag. However the drag at slow speed does not account for nearly as much as the lift.

Just look at takeoffs from short runways with heavy bombs. They don't worry about the drag of the flaps just the weight of the bombs. If the drag from the flaps was equal to the lift then the aircraft could not takeoff.

The downside of the drag really starts about 180 to 200MPH. The power available at low speed is overwhelming.

Remember the F4U-1D could take off with over 4,000lbs of ordinance. The drag from the flaps at high power settings is not nearly enough to prevent acceleration.

[F4UDOA]

No, no, no! You are making the terrible mistake which most flight simulator developers and users always make. It is the mistake of thinking that wingloading equals turning ability. Wingloading is a moderately reliable indicator of an airplane's turning and climbing ability, but is far from the only factor or even the only important one. Liftloading, aspect ratio, and a lot of other factors which I don't really understand (chord ratio, taper ratio, et cetera) all are vital in calculating wingloading. They (and the Fowler flaps) are the reasons why the P-38 easily outturned the Me-109 in real life. Ignoring those factors is also why the P-38 doesn't outturn anything in simulators.

Benny,

Wingloading is THE primary indicator of turn ability. Everything else is less than second.

Just look at stunt planes. The power loading is less than average, the aspect ratio's are average (Between 5 and 5.5) but the wing loading is key.

BTW, The P-38 wingloading is poor and that is why it cannot turn well. However with flaps it turns very well in sustained turns in one direction.

Here is a  Sukhoi SU-29 Stunt plane

Dimensions, External
Wing span 8.20 m (26 ft 10½ in)
Wing chord: at root 1.985 m (6 ft 6¼ in)
    at tip 1.04 m (3 ft 4½ in)
Wing aspect ratio 5.5
Length overall 7.285 m (23 ft 10½ in)
Height overall 2.885 m (9 ft 5½ in)
Tailplane span 2.90 m (9 ft 6¼ in)
Wheel track 2.40 m (7 ft 10½ in)
Wheelbase 5.08 m (16 ft 8 in)
Propeller diameter 2.50 m (8 ft 2½ in)
Propeller ground clearance 0.425 m (1 ft 4½ in)


Dimensions, Internal
Cockpit: Length 2.60 m (8 ft 6¼ in)
    Max width 0.82 m (2 ft 8¼ in)
    Max height 1.05 m (3 ft 5¼ in)


Areas
Wings, gross 12.20 m2 (131.4 sq ft)
Ailerons (total) 2.32 m2 (24.97 sq ft)
Fin 0.28 m2 (3.01 sq ft)
Rudder 0.90 m2 (9.69 sq ft)
Tailplane 0.98 m2 (10.55 sq ft)
Elevators (total) 1.56 m2 (16.79 sq ft)

Weights and Loadings (two persons)


Weight: empty 735 kg (1,620 lb)
    empty, equipped 780 kg (1,720 lb)
Max fuel 207 kg (456 lb)
Max T-O weight: pilot only 860 kg (1,896 lb)
    two persons 1,204 kg (2,654 lb)
Max wing loading 98.7 kg/m2 (20.21 lb/sq ft)
Max power loading: M-14PT 4.55 kg/kW (7.48 lb/hp)
    M-14PF 4.01 kg/kW (6.73 lb/hp)
    M-9F 4.78 kg/kW (6.41 lb/hp)

Performance (M-14PT engine)
Never-exceed speed (VNE) 242 kt (450 km/h; 279 mph)
Max level speed 175 kt (325 km/h; 202 mph)
Stalling speed 62 kt (115 km/h; 72 mph)
Max rate of climb at S/L 960 m (3,150 ft)/min
Service ceiling 4,000 m (13,120 ft)
Max rate of roll 345º/s
*T-O run 120 m (395 ft)
*Landing run 380 m (1,250 ft)
Range with max fuel 647 n miles (1,200 km; 745 miles)
g limits +12/-10

*at 914 kg (2,015 lb) AUW

[Benny Moore]

Originally posted by F4UDOA
Wingloading is THE primary indicator of turn ability. Everything else is less than second.

No.  By that argument, the F-15 (weighing about four times your average World War Two fighter) shouldn't be able to turn well at all.  But it does!  In fact, it turns much better than aircraft with far, far lower wingloading.  The reason is powerloading.

Powerloading and liftloading cannot be dismissed as easily as you do.  Dismiss aspect ratio and the others if you must as "less than secondary," but powerloading is easily the most important factor in turning ability.  After all, missiles don't need wings.  Liftloading, a good indicator of climbing ability, also greatly impacts turning ability.

I'm no aeronautical engineer.  I don't know much about aerodynamics.  But I do know enough to know that you're making a big mistake when you calculate turning ability based soley or even just mostly on wingloading.

[humble]

Originally posted by Ball
yet the Spit 14, Typhoon, Mosquito and Tempest all suffer horrendously with torque.

auto takeoff cannot even keep the wings level on the hawkers on climbout, and the mosquito snakes around with its tail wagging like a stoned puppy.

The hog, both IRL and in this sim have exceptional control surface authority. So even though the plane has significant torque the control surfaces all offer exceptional force at both high and low speed. No other plane has anywhere near the "ground loop" potential of the hog. It is the most difficult plane to control on takeoff and landing in the game when control authority is lost due to insufficient air flow.

What seperates the hog from other planes is its exceptional docility in "unusual attitude" situations (as long as the pilot stays withing the flight envelope). It does in fact remind me of the unusual attitude training I had in a T-28. The hogs "seperation" is remarkably like that described in the manual BTW....

[Saxman]

I think a lot of people seem to expect the F4U wants to depart under any significant AoA or Gs. I agree that she may be a LITTLE more forgiving in the game than the historical aircraft, but get too heavy under the wrong conditions and she'll REALLY quickly bite you on the bellybutton (and yes, I HAVE frequently spun in during low-alt, low-speed fights pushing things just a bit too hard).

In particular, too much rudder and elevator at the same time seems to be the magic combination. The Hog snap rolls like MAD (oddly, every time I do it--intentionally for not--I always seem to end up inverted when I recover).

[Squire]

AH models powerloading (weight/hp) as well as wing loading, as well as drag and lift.

The F-15 btw, has a 73lb/ft wing loading, the MiG-21, 77lb/ft and the MiG-23 78lb/ft.

The F-104 Starfighter, which is not known for having a great turn ability, has 105lbs/ft.

So it will out turn them with its wing loading rating.

The P-38 isnt an F-15 as you well know, and it doesnt have anywhere near the advantage in powerloading over its contemporaries as the F-15 had. In fact its powerloading is no greater than its contemporaries. You can crunch the #s yourself if you like, its a simple combined hp vs weight rating.

Regards.

[F4UDOA]

No. By that argument, the F-15 (weighing about four times your average World War Two fighter) shouldn't be able to turn well at all. But it does! In fact, it turns much better than aircraft with far, far lower wingloading. The reason is powerloading.

It depends on what you are comparing it too.

Can an La-7 out turn an A6M2?

All things being equal or close power loading, apect ratio or Clmax might affect the outcome but as long as one aircraft has a clear wingloading advantage I believe it be superior in turn radius.

[F4UDOA]

Benny,

There is one other type of turn that can be executed where wing loading is not the final answer but then either is power loading.

Instantainous turning.

That is a limitation of the airframe that can be improved with powerloading and wingloading but ultimately it is the limits of the aircraft design (not just the wing or wingloading).

[straffo]

Flap up ,flap down in rapid motion give to the F4U the "flapping" hability.

This hability autorise the Corsair to float over the CV desk and some skilled pilot even can take off using this trick.

Now where did I put my Jack Daniels bottle ?

[Bodhi]

I had a discussion yesterday with an experienced Corsair pilot (modern day) and his answer to the the reason that the Corsair turns (in a circle as krusty brought up) so much better than the spit and mustang was that the Corsair's wing is of a high lift design as opposed to the laminar flow wings of the mustang and spit.  The spit was still a good turning airplane, but he said an experienced Corsair driver should be able to keep up or win in a turn competition.  The other thing he mentioned was that Corsair pilots rarely tried to turn their birds to extremes in combat, because if they ended up in a high speed stall, or any stall, the chances of spinning it were so great.  Most spins in a Corsair quickly become unrecoverable.  As for the Mustang, he said that basically it hated slow turns, and it's departure is so nasty that slow mustangs generally meant dead mustangs. ie the spin.  Did not have much bad to say about the spit, actually he rather enjoyed flying the ones he had.

I am not an engineer, but this does make sense

[Captain Virgil Hilts]

Originally posted by F4UDOA

BTW, The P-38 wingloading is poor and that is why it cannot turn well. However with flaps it turns very well in sustained turns in one direction.