Author Topic: F4u flaps (Read 7475 times)

Knegel · « **Reply #60 on:** November 19, 2006, 11:58:29 PM »

Quote

Originally posted by hitech
Knegel: Not really Disagreeing with you that much. But notice in the piece of your post I disagreed with, you were refereeing to inertia. I.E. heavier plane.

In my posted case, I was analyzing same wing & area different plane weights.

HiTech

Actually i was refering to the influence of inertia at highspeed(speeds around and above Vmax) . In the case of two planes with same engine and wing and different weights the more heavy plane dont will have a disadvantage in a smooth turn, as long as its a decelerated turn.

In this case the more heavy plane of course suffer badly by the more bad powerload, so the real disadvanatge start when the turn get to be sustained. Inertia while turning still work into flightdirection, not only outside the turnradius.
In case of the 190A8 or P47D vs a Zero or HurriII the Power + weight(inertia) should easyly be enough to outzoom the light/powerless planes, at least when the zoom climb start above the Vmax of the heavy planes and so MUCH above the Vmax of the light planes(where the propeller is more a anydycap than a help).
Regarding AH i dont understand that my thoughts work regarding the F4U airframe, but the P47 and FW190 airframe dont follow this rule.

Greetings,

bozon · « **Reply #61 on:** November 21, 2006, 09:16:38 AM »

There's something else that bothers me about flaps in AH - especially the full flaps.

I tested a few planes in AH at full flaps. At full flaps, full power and auto-speed set to 100 mph (minimum of .speed command), planes climb 1.5-2 kfps. I suspect that the rate of climb may be even higher at lower speeds which I will have to test manually. It would be interesting to check climb rate at the no-flaps stall speed. It would give some indication to efficiency by comparing the increase of throttle (MAN or fuel burn in E6B) with the potential energy increase rate (ROC). Or climb rate at full power with different flap settings but constant speed.

I would very much like to know from people who are familiar with real planes how much sense does this makes to them. I was under the impression that at full flaps planes can barely climb. Of course the excess power of F4U is far more than what you get in cessna 172, but sill...

The other thing is that in planes like 190A5 and P47D25, auto trim reaches the limit and can't keep the plane steady at 100 MPH full flaps and a turn left develops due to the torque. On other planes like the F6F and F4U, trim is enough to counter it even at 100 mph. So some planes can't benefit from flaps at very low speeds simply because they can't handle the torque.

stantond · « **Reply #62 on:** November 21, 2006, 12:40:38 PM »

The F4U-1, F3A-1, and FG-1 pilots manual AN-01-45HA-1 dated 1 March 1944 describes full flap use in the F4U for short distance take off, also there is an exerpt that I will quote:

"FLAP SETTINGS- For normal operation it is recommended that a setting of 20 deg be used for take-off. Actually, any setting from 20deg to 50deg ("FULL DOWN") may be used, the higher settings giving shorter ground distance. Take-offs with flaps up are easily accomplished with a small increase in run, dispensing with the inconvenience of retracting the flaps after take-off. In addition, the rate of climb immediately after take-off with flaps deflected is inferior to that with flaps "UP". Take-offs at high flap settings and at full flap should be made only when it is necessary to obtain the shortest possible ground run, and after more experience with settings increased gradually from the recommended setting of 20 deg. When a high flap setting is used, the elevator tab should be slightly more tail heavy (about 1 deg).

NOTE

It has been found with the flaps down, the tail cannot be held on the ground with the stick full back, at manifold pressures greater than 44 inches Hg. Also, when operating a wooden platform, the wheels will start slipping on the deck at about the same manifold pressure. As a result, when making carrier take off it is necessary to advance the throttle through the final portion of its travel as the airplane starts to roll. No difficulty should be encountered in this operation.
(11) Open the throttle gradually and smoothly.

CAUTION
Do not retract the flaps too soon or too rapidly if the speed is very low; otherwise the airplane may settle due to the loss in lift. It should be remembered that the higher the control speed, the better the control. "

Regards,

Malta

F4UDOA · « **Reply #63 on:** November 21, 2006, 01:56:10 PM »

Stantond,

Is there a performance index in you F4U manual? I don't think I have that one.

The POH is an awesome source of information.

Stoney74 · « **Reply #64 on:** November 21, 2006, 05:37:09 PM »

Quote

Originally posted by bozon
I would very much like to know from people who are familiar with real planes how much sense does this makes to them. I was under the impression that at full flaps planes can barely climb. Of course the excess power of F4U is far more than what you get in cessna 172, but sill...

I'm not even sure we can make the comparison. One of the things I'm still trying to figure out about AH is why lowering the flaps makes the nose pitch up. In real life, its the exact opposite.

Knegel · « **Reply #65 on:** November 22, 2006, 01:37:34 AM »

Quote

Originally posted by stantond
NOTE

It has been found with the flaps down, the tail cannot be held on the ground with the stick full back, at manifold pressures greater than 44 inches Hg.

Malta

This is imho the biggest discrepancy to AH and cause the great turn and climb of the AH F4U with flaps.

In AH i need to push the stick rather down to keep the F4U nose down, while full flaps in general lower the nose, this at least count for high flap angles.

The missing need to pull the stick probably also explain why the F4U with flaps have a so smal induced drag.

Greetings,

Debonair · « **Reply #66 on:** November 22, 2006, 02:08:27 AM »

Quote

Originally posted by bozon
There's something else that bothers me about flaps in AH - especially the full flaps.

I tested a few planes in AH at full flaps. At full flaps, full power and auto-speed set to 100 mph (minimum of .speed command), planes climb 1.5-2 kfps. I suspect that the rate of climb may be even higher at lower speeds which I will have to test manually. It would be interesting to check climb rate at the no-flaps stall speed. It would give some indication to efficiency by comparing the increase of throttle (MAN or fuel burn in E6B) with the potential energy increase rate (ROC). Or climb rate at full power with different flap settings but constant speed.

I would very much like to know from people who are familiar with real planes how much sense does this makes to them. I was under the impression that at full flaps planes can barely climb. Of course the excess power of F4U is far more than what you get in cessna 172, but sill...

The other thing is that in planes like 190A5 and P47D25, auto trim reaches the limit and can't keep the plane steady at 100 MPH full flaps and a turn left develops due to the torque. On other planes like the F6F and F4U, trim is enough to counter it even at 100 mph. So some planes can't benefit from flaps at very low speeds simply because they can't handle the torque.

flaps are a real drag, but i've never been in a plane (including many different versions of the 172, even a real dog of a 160hp 172 with a "cruise" prop) that wont climb with them full out, probably some sorta FAA regulation on that

Charge · « **Reply #67 on:** November 22, 2006, 06:16:10 AM »

"The missing need to pull the stick probably also explain why the F4U with flaps have a so smal induced drag."

What do you mean with stick pulling? I think it is logical that for level flight you need to push the stick forward because the profile and thus angle of the wing incidence has changed so radically because of full flaps. Especially in planes with full flaps, not split flaps.

"One of the things I'm still trying to figure out about AH is why lowering the flaps makes the nose pitch up. In real life, its the exact opposite."

I think some planes wanted to pitch down with flaps and some up. I think they generally pitched down.

-C+

Charge · « **Reply #68 on:** November 22, 2006, 12:42:07 PM »

Err, got a brainfart -sry.

Because the flaps try to wrench you nose down you need to pull back the stick some to compensate until the speed has dropped sufficiently.

-C+

Ball · « **Reply #69 on:** November 22, 2006, 12:47:59 PM »

The Spitfire did not have a laminar flow wing, that is why they made a prototype Spiteful.

hitech · « **Reply #70 on:** November 22, 2006, 12:55:33 PM »

Charge: Pitching moment do to flaps can go either direction.

LEADPIG · « **Reply #71 on:** November 22, 2006, 01:08:37 PM »

Where's Widewing in this , he's the only person i'll believe in this discussion, save for GOD.

stantond · « **Reply #72 on:** November 22, 2006, 01:29:26 PM »

Flying around with flaps out is certainly not a standard condition. The best rate of climb I could get was 1500 fpm with mil power using full flaps at 100 ias. I have no idea whether this is correct, but it seems plausable. The stall speed is considerably less than this speed with the vne about 140 mph for full flaps.

Certainly the wing provides more lift with flaps out at very low speeds, per the POH. How that affects climb rate can be debated, but with full ordinance take off from a carrier requires full flaps on a -1D. Full flaps on the other aircraft are used to create drag and produce no lift so they are only used on landing. The flaps on the F4U are unique, but I don't have any specific data on their performance.

Regards,

Malta

F4UDOA: there are some performance charts, describing ROC at various weights and ranges along with aircraft weights based on ordinance loadout. Is that the sort of thing you are talking about? I can post a link to jpg's of charts or tables if that helps.

As an aside:
An interesting option in AH would be the 'light' fighter configuration which has 3/4 tank of fuel and 200 rpg. Of course, an itchy trigger finger can add that configuration.

F4UDOA · « **Reply #73 on:** November 22, 2006, 01:39:49 PM »

Malta,

That would be great. I think I know the chart you are refering to but I would like to see if it is anything new.

I have mentioned to HTC that the "Interceptor Loadout" would be a nice option. There are no points for getting shot down with 750lbs of ammo on board.

BTW, You did a good job explaining the differance between F4U and land based flaps. The AAF fighter flaps for the most part where to be used to assist in reducing speed to land not to generate lift to takeoff from a carrier with a heavy load or to assist in low speed handling around a ship. Of course the P-38 and P-51 had Combat flaps of their own but not for the same design purpose.

gripen · « **Reply #74 on:** November 22, 2006, 01:41:15 PM »

F4UDOA,
Do you have some drag polars for the F4U, preferably with and without flaps?

It would be fairly easy to calculate at which speed or Cl the drag with flaps exceed the clean situation. There is a NACA report (WR-L-440) on wind tunnel tests of the 1/2,75 scale F4U model but the problem with that report is that the flaps configuration appear to be not standard (full span flaps).

gripen