1.09 : Get Rid of Autoretracting Flaps...

[Tac]

... or make it an option in the SETUP, just below the Combat Trim.

Gripe: The one plane that heavily relies on its flaps (P38) is getting KILLED because they retract automatically the instant the speed ticker hits 250mph. Any kind of prolonged loop fight in which the 38 does not pull hard will make the plane go beyond 250mph for a second b4 the plane goes nose up again and bleeds the speed down to 120'ish.. but before that, the flaps retract, and you're pulling while they retract, SPIN, and the happy con you were following turns on your 6.

And lo if you have more than 1 notch deployed, 250mph mark reached, retract one, spin, while trying to recover plane goes below 250, flaps stop retracting, recover ( IF the con hasnt shot you down by then:  plane quickly goes to 250, ANOTHER flap is retracted, SPIN again! . Oh joy.

Can we please have the option to not make them autoretract? If the flaps are down at 250mph make the plane start to shake, the higher above 250mph the worse it shakes until maybe 320mph at which point you could have the flaps ripped out and some kind of damage to the wings.

[Seeker]

Seconded!

[Tilt]

Thirded!

Quite happy if the auto retract dissappeared when switching off the auto combat trim............

Further what about deleting the speed threshold for lowering the flaps............

Why cant they act like the gear.......... lower it when too fast..........loose it!!!


Tilt

[funkedup]

It's not autoretracting, it's backdriving.  If somebody wants to present evidence that a particular plane had non-backdriving actuators then they might change it.

I think the maximum flap extenstion speeds are based on actuator force/torque limits too.  It's not that the flaps would break off the airplane, it's that the actuator didn't have enough power to extend flaps above a certain speed.

[Tilt]

Originally posted by funkedup
It's not autoretracting, it's backdriving.  If somebody wants to present evidence that a particular plane had non-backdriving actuators then they might change it.

I think the maximum flap extenstion speeds are based on actuator force/torque limits too.  It's not that the flaps would break off the airplane, it's that the actuator didn't have enough power to extend flaps above a certain speed.

The La 7 & La5 FN had split hydraulically operated flaps.

See flaps here


So yes there would be a pressure at which the force was too high for the actuator to push them down........ I do not know what it is.

I am sure that there was no pressure operated return valve in the circuit ( I have the circuit at home and will check and post)

The pilot had a simple 3 position hand valve. Item 10 on this drawing

and the handle to the left here

and here with the handle pushed forward

My understanding is that the centre blocked the circuits, pushing one way raised flap, pushing the other lowered flap. Hence flaps would not auto retract unless the valve was left in the forward position which would risk bleeding the air/oil accumulator. (air from which also drove down the gear)

Given that there was an IAS which provided enough back force to stop full deployment I would profer that various degrees of partial deplyment could have been executed at various IAS.


Tilt

[Guppy]

Originally posted by funkedup
I think the maximum flap extenstion speeds are based on actuator force/torque limits too.  It's not that the flaps would break off the airplane, it's that the actuator didn't have enough power to extend flaps above a certain speed.

Lt. Col. (then-Lt.) Besby Holmes, 347th FG (Guadalcanal, P-38Gs):

"I tripped my maneuver flaps, which was illegal, for when I looked at the airspeed I was still doing 350, I think the tech order said 260 indicated was the maximum speed to trip a maneuver flap. At that stage of the game I didn't care about that as long as the wings stayed on me. Unless I got there fast, Barber was a dead duck."

[Eagler]

I say set them up to break off or jam - even better - instead of auto retraction, then again I don't use them

As soon as HTC were to make the change, more ppl would be complaining about them breaking/jamming than are now complaining about the auto retraction..

[BigCrate]

Was flying the P-47d-30 yesterday offline.. and was playing around with it.. I did a split-s at 200 with 3 notches of flaps down and by the time a finished the move.. I was at 300mph with one notch of flap still down.. I was thinkin to my self wish the 38 could do this... So I rolled over did a swallow dive and the min. I pasted 300mph the flaps went up.. the rest of the way.. And i stayed with dive and the 47 dives damn good!  So HTC jus needs to model the flap retraction after the 47d-30 atleast.. 1 notch of flaps stay down until u get past 300mph.. and in AW if you left your flaps down in a 38 and went into a dive and got some speed up say 300 or 325 mph. The nose would tuck and your pitch control got real sluggish like in a dive but with the buffeting. maybe HTC could modeled it like that.. HMmm I dunno. and HTC needs to redo thedive flaps on the 38 to they suck.. Plain and simple.

CW

[Toad]

Not all flap systems are the same. I think we need to remember that.

There are different designs.  Some have strong linkages, some are not so strong. I think some had the capability of "blowing up" to some degree in an overspeed; some did not.. probably most. Some were manually deployed, some used hydraulics and there were probably even some electrics. Some aircraft really buffetted when flaps were oversped; some didn't buffet all that much. Some generated a need for high stick forces to counter flap over speed (force feedback); others weren't as bad (usually depending on where they were on the wing).

Point is, if you're going to do it RIGHT, flap modeling is going to have to be a whole lot more complex and airplane specific.

So, while I'm speaking neither for nor against, I am pointing out that to do this RIGHT all across the planeset... it's going to be a BIG project.

Thank you... and goodnight.  

[HoHun]

Hi everyone,

it seems to me that auto-retracting is a kludge introduced for ease of modelling.

As far as I know, manual, hydraulic and electric flaps were not subject to auto-retraction, and I'd think it would have required quite some sophisticated system to implement it in real life. (Post-war Gloster Meteors had one.)

In WW2, there were pneumatically operated flaps as well, and these could actually be auto-retracting. The FM-2 Wildcat manual describes this process, which sounds like a great feature for go-arounds. However, I believe that despite its advantages the auto-retraction really was a side-effect of the kludge Grumman used for lowering the flaps :-)

Regards,

Henning (HoHun)

[Sachs]

Tac.  I hear ya on this one.  I do not like the auto retract myself either, granted I never use it in the Dora  but for those that do use them it should not retract Auto.

[Tilt]

Originally posted by Tilt

The La 7 & La5 FN had split hydraulically operated flaps.

I have just read in another publication that the hydraulic actuating cylinder for the Lagg3 flaps had an inbuilt pressure relief valve that allowed oil to flow (in both directions) across the piston in the event of over pressure.

I have every reason to believe that this was the same cylinder used in later La5 and La7 variants.

This is in line with the hydraulic plan I have, which is more pictural than schematic. (just shows the pipe going to the cylinder)

Hence as airspeed increased it is possible that the flaps lifted pushing the actuating cyliders piston down the cylinder whilst the control valve was still closed.

My assertion that they would be held in position by the operating valve was incorrect.

AH's modeling of them able to be pushed back by air pressure is correct. (at what airspeed I have no idea)


we live and learn

Tilt

[funkedup]

Nice research Tilt.

I will try to find hydro schematics for US planes.  If they all used cylinders I wonder if they had pressure relief valves too.  

A more modern setup is to use a rotary hydraulic motor driving a gearbox and shaft system, or driving a jackscrew.  These would probably not backdrive due to the gear ratios and/or friction in the jackscrew.  But I don't know if this was used in WWII aircraft.

I think most of the UK planes used pneumatics, which I'm pretty sure would backdrive as well.

P-39 and Fw 190 used electric flap actuator.  I don't know details of the Cobra but I think the 190 had an electric motor driving a jackscrew.  In general jackscrews will not backdrive so that system shouldn't "autoretract".  I'll look into this further.

[Sorrow[S=A]]

Tilt-

In a discussion with Oleg on this during the Il-2 beta he indicated that the design of the Lagg flaps would not do this. In fact he indicated that the flaps had enough pressure to open at almost any extreme speed, to the point where the cylinders would actually warp the frame supports and the flaps would not later retract.

[Tilt]

Originally posted by Sorrow[S=A]
Tilt-

In a discussion with Oleg on this during the Il-2 beta he indicated that the design of the Lagg flaps would not do this. In fact he indicated that the flaps had enough pressure to open at almost any extreme speed, to the point where the cylinders would actually warp the frame supports and the flaps would not later retract.

I think it it is pretty certain that there was a pressure bypass valve  in the flap actuating cylinder.

The question I cannot answer is at what IAS would the back pressure be high enough to to lift this pressure relief valve.

The hydraulics were generally limited to 30 / 35kg/cm^2. What the flap pressure relief valve was set at  I do not know. Even that data is worthless without the actuator piston dia and any linkage MA.

BTW looking at the design its the linkages between actuater and (most probably starboard) flap that would fail first (one actuator located in the port wing operated both sets of flaps)

So if you can fish up "OLEGs" notes to help us......................


Tilt