Flaps and Carrier takeoffs

[F4UDOA]

Gents,

This has been a sore spot for me going back a ways.

Two issues really.

1. Use of flaps for carrier take off. I have done quite a bit of testing in this department and what I have found is that the flaps IMHO seem to add to much drag relative to the lift provided. According to Bitish AFDU of the F4U use of full flaps should "cause the tail to come up almost immediately". This means to me that at least part of the aircraft has reached flying speed rather quickly which in the case of the F4U with full flaps should be at around 75MPH at 12,000lbs. Even Dolittles B-25 flew off the deck where as our fighter fall off.

A. The problem as I see it is that at speeds below 100MPH the power of the engine and prop should overcome any additional drag caused by having flaps deployed at takeoff. I don't understand the math well enough to display this but I remember something about drag really not making as big a difference at low speed combined with a 25knot headwind and full power propwash from 2,000HP the tail should comeup immediately as stated in the AFDU.

B. Symptom- Making it very difficult for carrier fighters to takeoff with large loads and the result is A/C falling off the carrier deck instead of flying off.

C. A possible answer is the lack of propwash affecting relative stall speeds. Even the smallest increase in engine power should have some affect on lowering stall speeds and making it possible to create enough thrust to get the tail flying amost immediately after applying power.  

2. Flaps used for maneuvering and landing- I have done quite a bit of testing trying to find the best amount of flap used for turning. On the F4U the answer is 1 notch. Never more or you will add time to the radius of your turn. Two notches was the default maneuever setting from the pilots manual.

A. A bi-product of this is the inability to maintain level AOA at close to stall speeds. As soon as you approach stall your nose falls through the horizon. This should not happen. Once again I believe the wing acts as if it is in a vaccum. The thrust from the prop plus the speed of the A/C should combine to be enough to keep the A/C flying and the nose level but it falls through everytime.

B. I think HT/Pyro are changing this based on the past post from them. But I still think the drag from flaps at low speed act to strongly to slow the A/C down while at the same time not assisting in lift for takeoff and slowing acceleration to flying speed.

[Arlo]

One thing that's modeled in AH but seldom used is wind at flight deck level. It appears to be a general default arena setting to have 0 wind there. Perhaps this is done because of the apparent neccessity to maneuver carrier task forces in all different directions to avoid getting sunk by high/level B-17s and Lancasters (of course, nobody seems to realize that a mild, 10 degree zig-zag on an otherwise steady course would defeat that). Of course, it's hard to "park" a CV task force and utilize the aircraft onboard if you're forced to steer a somewhat steady course into the wind. Such would require more effort and thought than most players are willing or able to apply. Ahem.

Since I've yet to experience an actual deckwind in AH, I can only assume and hope that it would make a drastic difference in the take-off performance.

That being the case, I make it a habit of:

1: Backing up on the deck if I have a full load of fuel and ordinance.

2: Utilizing wep on take off.

3: Not dropping flaps until I'm almost past the island .... then two notches as fast as I can. Wheels up!

Still, I'm in agreement that I'd like to see the model tweaked to where we can drop flaps before we even start the engine and receive the benefit of added lift without suffering exaggerated drag from a standstill.

[Imp]

I have a question about carrier take off.

What is the best wind direction to help TO?

[Arlo]

It doesn't matter unless the arena has a wind layer set that low. If it does, turn the carrier directly into the wind for best results. The arrow on the map would show wind direction .... point the ship in the opposite direction. That creates more headwind which results in more lift on takeoff. Sailing "with the wind" (the same direction as the arrow) would serve to negate lift and would be detrimental to takeoff.

[2Hawks]

First thing about taking off with any AC on the carrier, whether you back up or not is to begin putting back pressure on the stick BEFORE you reach the end. Try and lighten the plane at least if not get it slightly off the deck before dropping off. Otherwise, you will have two forces working against you, the weight / lift ratio of the AC at that moment, and the downward inertia to defeat once you have run out of flat-top.

If you remove the downward inertia on takeoff you will find you have a much greater chance of getting airborne.

Begin your roll with no flaps, full power plus wep right away. Apply 3 - 4 knotches of flaps incrementally as you proceed down the deck, begin a gentle back pressure on the stick when you see the guns on the left hand side. (Looking Left Front)

Does it for me nearly every time. F4Ud with Rockets, Bombs & 75% to 100% Fuel - No Problem.

[Imp]

Thanks alot guys.

I thought that having the wind in my back might increase my speed and help me TO.

Your answer makes me glad I asked

Ill have to try pulling the stick before gettin off the flat top too.

[Reschke]

Originally posted by 2Hawks
First thing about taking off with any AC on the carrier, whether you back up or not is to begin putting back pressure on the stick BEFORE you reach the end. Try and lighten the plane at least if not get it slightly off the deck before dropping off. Otherwise, you will have two forces working against you, the weight / lift ratio of the AC at that moment, and the downward inertia to defeat once you have run out of flat-top.

If you remove the downward inertia on takeoff you will find you have a much greater chance of getting airborne.

Begin your roll with no flaps, full power plus wep right away. Apply 3 - 4 knotches of flaps incrementally as you proceed down the deck, begin a gentle back pressure on the stick when you see the guns on the left hand side. (Looking Left Front)

Does it for me nearly every time. F4Ud with Rockets, Bombs & 75% to 100% Fuel - No Problem.

Yes that is correct 2Hawks. However if you look at the F4U series they still do not perform correctly on carrier takeoff. I posted a little while back on the difference in the F4U and F6F max weight. There is not enough difference in the weight and in the engines of the two planes to cause the F6F to literally jump off the deck versus the F4U wallowing around trying to crash. If you take both planes fully loaded and start from the same spawn point (without rolling backwards) you will see what I am talking about. The only plane that even comes close to actually leaving the carrier deck as intended is the F4U-1 and if you add a bomb or drop tank with a full internal fuel load it dips down a good bit.

One other thing is that I have yet to be able to get any aircraft to roll backwards on the flight deck and I have been in and out of this game for its entire life span.

[Gwjr2]

Reschke  with the F4 AC try 2300 rpm and the plane will start to roll back, steer with rudder and if you like wait for refuel to top off the  tanks and away you go.

[1Duke1]

I think the biggest thing effecting CV takeoffs is what Arlo said....wind over the deck.

Wind over the deck gives the aircraft more lift, and it's therefore not relying totally on airspeed to get airborne.  CV's turned into the wind for both launches and landings.  When landing it allowed the aircraft to attain a slower landing speed while maintaining maneuverablility.

A lower approach speed was also needed for the arresting gear.  Too fast, and either a tailhook could break or break the arresting gear.

Sidenote:  A fully loaded F4u-1D (100% gas, 1000#/rockets) can be launched successfully with 1 notch flaps without backing up, and no wep.

  Set elevator trim to just below the 'E' on the trim gauge, one notch of flaps (believe the hog took off with full flaps, but don't have any documentation supporting that fact).  Go to full power while holding the brakes.  As the power stabilizes at full, release the brakes and start rolling. As tail comes up, give a little back stick. Clear of the deck, gear up immediately, and gently...GENTLY feed in right rudder to keep the wings level.  Do not use any lateral aileron to level the wings, or the plane will spin in.  

It will still drop, it shouldn't, but it does, so be gentle with the backstick and the right rudder, and soon you will be flying away from the water. Keep the notch of flaps in until you get a decent flying speed, then raise the flaps.  Still need to be gentle on turns till you get some alt, but you are flying.

[Reschke]

Originally posted by 1Duke1
It will still drop, it shouldn't, but it does, so be gentle with the backstick and the right rudder, and soon you will be flying away from the water.

That is the whole thing there 1Duke1. The F4U drops entirely too much on take off now; whereas the other USN aircraft seem to jump off the deck even fully loaded.

[Tilt]

Originally posted by F4UDOA
think the drag from flaps at low speed act too strongly to slow the A/C down while at the same time not assisting in lift

I could agree with this generally.....  


(sorry I only got la7 data so can only make this comparison)

Safe landing speed in AH for an La7 is circa 100 >120mph yet RL the slats only opened at 130mph.

RL fully flapped reccommended landing speed was 84 mph. Yet in AH  the La7 is in stall at this speed. (and one would expect a zone of safety below this)

Logic could point to either poor lift when flapped or lack of additional lift due to slats or a combination of both.

Its difficult for me to get a "feel" for this because after AW (FR) all the AH AC seemed less stable at lower speeds. (and I know AW measured speed in knots not mph)

[F4UDOA]

Tilt,

I had an ongoing dialog with HT about stalls he was looking at. I think they will address the problem in AH2 based on what I have seen in there recent post.

However it is hard to tell if related to that is the inabilty of flaps to provide enough lift for takeoff especially in an overload condition.

I believe this is because of the lack of prop wash modelling at low speed high AOA.

Here is the best evidence I can show.

The F4U stall speed is at 11,300LBS

Full flap no power 75knots/86MPH

Full flap power on (23"MAP 2400RPM)66Knots/76MPH

23" MAP in the F4U Pilots manual is less than minimum cruise. Basically that is at idle. The lowest power setting shown in the engine chart is 25.5" MAP producing 600HP roughly depending on altitude. Takeoff power is 2,000HP!!

So the F4U stall full flap at 11,300LBS drops 10MPH from no power to idle power. So if the power generated from the idling prop drops it 10MPH then what should the stall be when applying 2,000HP to the wings throught he prop?

I imagine that is why the AFDU says the tail comes up immediately because the power is enough to make the tail fly even at Zero relative ground speed.

Even at 15,000LBS from the Pilots manual the F4U should stall at 86Knots/99MPH with NO POWER. That is full fuel, 8 rockets and 2,000lbs of bombs!!

[hazed-]

One problem is that you start at just the wrong spot for a fully loaded F4u on the spawn.If you allow the aircraft to roll backwards using the light throttle technique you can take off easily.this could point to a simple moving of the spawn point 20 feet back and its fixed.then again in films you see f4u's taking off in what seems even shorter decks.Usually the decks are stuffed almost to the bow with other fighters.Is our AH CV really to scale?

Id have to agree with you f4udoa here concerning the amount of lift that the flaps 'should' provide compared to the drag they 'should' create.
As AH is now I often leave the flaps up until i drop off the carrier and i put them down just before i lift off.This allows me to pick up a tiny bit more speed. If i try to do the same thing but apply flaps full down from the start I find i never gain enough speed.
Also i hit gear up as soon as i leave the deck.

Now if we watch films of F4u's taking off fully loaded we will undoubtedly see that they all have their flaps fully deployed.This suggests it was the best way to launch.This means really that in AH we should have an easier time launching with full flaps from the beginning. Why is it not the case? I think it points to what F4UDOA is saying. Somewhere along the line flaps have become more 'drag' inducing and slow the aircraft down a little too much.Its not by much as far as i can tell as my little trick of deploying flaps late can counter it.

F4udoa have i understood what you mean correctly? Ifthis is the area you mean then id have to agree it seems to be an area where AH doesnt match the WW2 movie clips.

[F4UDOA]

F4udoa have i understood what you mean correctly? Ifthis is the area you mean then id have to agree it seems to be an area where AH doesnt match the WW2 movie clips.

Hazed,

I would never try to match a movie clip. There are to many variables. But I would like to match the pilots manuals, NAVAIR and AFDU data etc.

Also I don't want to "cheat" a little by rolling back or deploy flaps incrementally. What I really want is to have more accurate modelling of trim tabs in degrees and be able to use takeoff power (no WEP) and takeoff with a full load and be flying not falling by the end of the deck.

I believe the culpret is airflow over the wings not creating enough lift while the flaps are creating an enormous amount of drag at low speed.

Correcting this will also by itself affect many other areas of the game especially torque and low speed handling.

[Tilt]

Originally posted by F4UDOA

Full flap no power 75knots/86MPH

Full flap power on (23"MAP 2400RPM)66Knots/76MPH

Sorry to seem dim......... to catch up

Prop wash generates higher pressure under the wing than it does above it? hence lift?

AH does not model prop wash (is it then a theoretical model able to miss bits out?)

At low speed prop wash's  % contribution to lift is greater (higher AoA and lack forward velocity)  hence its absence is more noticable in the AH model v RL "model" at low or near stall speeds?

From this then all AC (except jets) should incurr better low speed handling and lower stall speeds onece prop wash is introduced?

This would vary as a function of power, efficiency and surface areas? (prop and affected wing)

And to a less discernable extent allAC would also enjoy a slightly better turn capability which would be less significant with increased speed?