Flaps deployment

[Random]

Think about that for a second. For what reason other than over speed would the flaps move without the pilots command? It would seem quite silly if the flaps simply moved on their own without pilot command. Yet, they are clearly stating that the flaps will NOT move unless the pilot moves them. Seem like a odd thing to be so clear on.

 

As was previously pointed out as well, I cant imagine why youd need to put a placard in the cockpit and manual warning the pilot of over speed if the system was automatic. It says dont deploy flaps at those speed, implying that you can....Why not state: Here are the speeds you cannot do, but the system will take care of it for you so your good.

 

One word : Failure.

 

Automatic system that doesn't fail safe? Best if the person operating it knows the limits.

[Yo-Yo]

NONE.

 

The biggest danger with hydraulic actuators is one blows a seal and other does not resulting in asymmetrical flap deployment.

 

Mechanical linkage like the Bf-109 or FW-190 just let's things break, LOL.

 

I guess that overloaded motor in 190 will cause excessive current, but what kind of damage - flaps structural damage, motor damage or circuit breaker click :) - I do not know exactly.

 

The only thing I know that the frozen car windshild wiper does not break itself but burns a fuze or a motor. :)

[NineLine]

Because it would be a logically unnecessary statement. It stand to reason that any flap system moves the flaps to a desired position and doesn't movie unless something makes it (like in a full blow up system). IE: I move lever, thing happens, and machine doesnt decide for me what flap setting I want(in non-overspeed). If we assume the flaps DO move during over speed, why would any pilot expect the flaps to move in any other condition? If I put flaps down in a plane, withing the normal speeds, I wouldnt expect them to go down on their own. Nor would I expect them to deploy if I didn't intend it.

 

Nothing is automatic, so I think you are confused now... anyways, I am not seeing a reportable issue with the P-51 right now.

[NineLine]

I guess that overloaded motor in 190 will cause excessive current, but what kind of damage - flaps structural damage, motor damage or circuit breaker click :) - I do not know exactly.

 

The only thing I know that the frozen car windshild wiper does not break itself but burns a fuze or motor. :)

 

Perhaps the flaps would be frozen in the position the damage occurred? Eventually break if you continued to over stress them?

Edited January 20, 2015 by NineLine

[Solty]

Nothing is automatic, so I think you are confused now... anyways, I am not seeing a reportable issue with the P-51 right now.

How is it that I can drop my flaps down max (landing) and start a dive that should cause flaps to get damaged or fly off. They are locked in this position... but in DCS they start to retract on their own :huh:

 

Why would there be any limits if there is no danger?

 

Also, it is not only P-51 issue. FW190 stays with flaps open and just looses speed. They work like dive flaps for Dora and in 109 you can just drop them max and nothing happens. How is Pilot of a 109 able to lower them at high speed? I don't know. Super huan probably

Messerschmitt Bf109 flaps operation video

 

Edited January 20, 2015 by Solty

[NineLine]

How is it that I can drop my flaps down max (landing) and start a dive that should cause flaps to get damaged or fly off. They are locked in this position... but in DCS they start to retract on their own :huh:

 

But now you guys are talking about a different issue than originally posted. You are saying the flaps retract on their own. That is not what was stated in the OP.

[Yo-Yo]

Perhaps the flaps would be frozen in the position the damage occurred? Eventually break if you continued to over stress them?

 

Possibly. As the gearbox seems to be of not reverse action.

[Yo-Yo]

How is it that I can drop my flaps down max (landing) and start a dive that should cause flaps to get damaged or fly off. They are locked in this position... but in DCS they start to retract on their own :huh:

 

Why would there be any limits if there is no danger?

 

Also, it is not only P-51 issue. FW190 stays with flaps open and just looses speed. They work like dive flaps for Dora and in 109 you can just drop them max and nothing happens. How is Pilot of a 109 able to lower them at high speed? I don't know. Super huan probably

Messerschmitt Bf109 flaps operation video

 

 

Waht force will freeze the flaps of P-51 against the hinge moment?

[Crumpp]

Super huan probably

 

Mechanical advantage.... You can deploy up to 10 degrees of flap in the Bf-109 to Vne according to Mtt.

 

I guess that overloaded motor in 190 will cause excessive current, but what kind of damage - flaps structural damage, motor damage or circuit breaker click - I do not know exactly.

 

IIRC, the FW-190 landing flaps are linked to the Gear circuit and Vfe is 300kph IAS for landing flaps. It will not allow a pilot to deploy landing flaps unless the gear are down. The take off flap setting can be deployed as the pilot sees fit or at least there are no restrictions in the flugzeug handbuch.

 

Manual Speeds are:

 

Landing flaps position - 300 km/hr to 220km/hr

Gear Extenstion - 300Km/hr

Gear Retraction - 250Km/hr (I think this to give you time to pull the flaps up if you have ot go around)

TO flaps - no speed restriction listed but I have attached to the flap pressure report for you.

 

I would think the circuit breaker would pop for sure if you deployed them at over-speed and the flaps not deploy. In theory, the circuit breaker should pop before any damage occurs...in theory. Personally I am not fan of resetting any circuit breaker in flight. Only reset one in flight before because the troubleshooting checklist called to pull it and reset on the cabin life support processor. I have never reset one that popped on its own and it often turns out badly for those that do. It is great way to go from an electrical problem to a fire.

 

If you deployed flaps and then over-speed with flaps deployed...

 

The motor turns a jack screw so it is pretty strong. I would think the flap would bend or the hinges fail before it forces that jack screw back in.

[Solty]

Waht force will freeze the flaps of P-51 against the hinge moment?

Honestly I have no idea. But why would Grumman make automatic flaps retraction system when pilot goes over 170knt, if normal flaps (of P-51) without that system do it the same way? Also why would there be labels like this if flaps would retract themselves:

 

Flap Restrictions

Angle Down/Max I.A.S

10/400

20/275

30/225

40/180

50/165

 

This is instruction for P-51:

 

 

EMERGENCY WING FLAP OPERATION

1. There is NO emergency wing flap operation provided on the P-51D as the hand pump has been eliminated. On all earlier models of the P-51, emergency operation is as follows:
   
   1. 
      

Put flap selector to desired position and operate the hand pump until it siezes. Flaps will be in desired position and will stay there until another selection is made.

 

http://rwebs.net/avhistory/opsman/pursuit/section7.htm

For comparison this is quoted Grumman instruction. Pilots Handbook of flight operations", for F6F-3 and F6F-5 aircraft. )))

SUMMARY:

A. pilot activates flaps with electric switch or hydraulic switch.

B. at 170 KTS or below the hydraulic system controled by the speed sensor/switch extends flaps out form the wing.

C. Compression springs ensure the flaps are positioned automaticaly to the most efficient angle from 0 to 50 degrees depending on the airspeed of the plane.

D. If speed increases over 170 kts or pilot activates switch to retract the flaps they will hydraulicaly retract back to the wing.

NOTE: The flap switch can be activated at "any speed". The flaps will deploy and begin operations automaticaly at the correct speed.

http://forum.totalsims.com/viewtopic.php?f=11&t=11718

 

I can't see the reason to include additional flaps system that are limited to given speeds if they work at any speed in P-51, and suposedly in any other plane for that matter as P-51 had standard flap mechanisms.:huh:

Edited January 21, 2015 by Solty

[Yo-Yo]

Honestly I have no idea. But why would Grumman make automatic flaps retraction system when pilot goes over 170knt, if normal flaps (of P-51) without that system do it the same way? Also why would there be labels like this if flaps would retract themselves:

 

Flap Restrictions

Angle Down/Max I.A.S

10/400

20/275

30/225

40/180

50/165

 

This is instruction for P-51:

 

 

EMERGENCY WING FLAP OPERATION

1. There is NO emergency wing flap operation provided on the P-51D as the hand pump has been eliminated. On all earlier models of the P-51, emergency operation is as follows:
   
   1. 
      

Put flap selector to desired position and operate the hand pump until it siezes. Flaps will be in desired position and will stay there until another selection is made.

 

http://rwebs.net/avhistory/opsman/pursuit/section7.htm

For comparison this is quoted Grumman instruction. Pilots Handbook of flight operations", for F6F-3 and F6F-5 aircraft. )))

SUMMARY:

A. pilot activates flaps with electric switch or hydraulic switch.

B. at 170 KTS or below the hydraulic system controled by the speed sensor/switch extends flaps out form the wing.

C. Compression springs ensure the flaps are positioned automaticaly to the most efficient angle from 0 to 50 degrees depending on the airspeed of the plane.

D. If speed increases over 170 kts or pilot activates switch to retract the flaps they will hydraulicaly retract back to the wing.

NOTE: The flap switch can be activated at "any speed". The flaps will deploy and begin operations automaticaly at the correct speed.

http://forum.totalsims.com/viewtopic.php?f=11&t=11718

 

I can't see the reason to include additional flaps system that are limited to given speeds if they work at any speed in P-51, and suposedly in any other plane for that matter as P-51 had standard flap mechanisms.:huh:

 

I only ask you, what makes you so confident that P-51 flaps can be deployed against the forces much greater than normal? Or what factor can hold the flaps as they were already deployed against increasing forces? It could be kinematic design like in Yak-18, a latch... did you find something in P-51? Anyway, there are several manuals for P-51 with hydraulics schematics... if you prove using these sources that the pressurized chamber of the actuator cylinder is completely sealed from the entire system with a check valve and there is no releaf valve to this part of tubing - it could be a base to recheck flaps in DCS P-51.

Edited January 21, 2015 by Yo-Yo

[NineLine]

NOTE: The flap switch can be activated at "any speed". The flaps will deploy and begin operations automaticaly at the correct speed.[/size]

[/left]

 

This is the only thing that has me wondering, I can understand the speed force the flaps to retract if you go fast enough, but once you level out, I am wondering if the flaps should then return to the position you have the lever in, right now they don't seem to, everything else seems to be working as one might expect.

 

Also if you are over-speeding the flaps, and forcing them to retract, I assume by forcing some fluid from the system by some relief valve, would you not eventually cause yourself issue if you lost too much fluid? Obviously I see no good reason why a pilot would get to this point, but I wonder how much fluid you could expend before the system didn't operate correctly anymore.

[Crumpp]

I wonder how much fluid you could expend before the system didn't operate correctly anymore.

 

In theory the check valves will lock the pressure in until the system over-pressurized and trips the relief valve. You get to hand pump the gear down and the flaps should retract when pressure relief valve trips as it depressurizes the entire system.

 

The check valves is why the manual solty quotes says:

 

Flaps will be in desired position and will stay there until another selection is made.

 

In a P-51 without the uplock modification, your inner gear doors will deploy.

 

The flaps on the P51 have no mechanical lock system. They are held in position by the hydraulic pressure.

 

 

The hydraulic system has multiple check valves to keep fluid moving in one direction and a pressure relief valve to keep the system from over-pressurizing.

 

1300 psi is what the system is pressurized too. At servicing, a hydraulic mule is required that can deliver 3gph at 2000 psi for 5 minutes to conduct the pressure test for leaks. The pressure relief valve is of course set to unload during this test.

 

So, if you over speed the flaps in the P-51, you would lose your entire hydraulic system. The pressure relief valve would detect the drop in pressure on the system circuit and open the pump circuit to pull fluid from the reservoir attempting to keep pressure until it emptied the reservoir.

 

The flaps would stay locked until the pressure relief valve trips depressurizing the system.

 

 

Hope this is helpful!

[NineLine]

 

Hope this is helpful!

 

Very much, thanks. I guess the question is now, if you put the flaps full down, then force them to retract with speed, then, level out, should the go back to full down on their own, or do you have to move the lever up again and back down again (as it is in the sim right now I think).

[Crumpp]

I only ask you, what makes you so confident that P-51 flaps can be deployed against the forces much greater than normal? Or what factor can hold the flaps as they were already deployed against increasing forces? It could be kinematic design like in Yak-18, a latch... did you find something in P-51? Anyway, there are several manuals for P-51 with hydraulics schematics... if you prove using these sources that the pressurized chamber of the actuator cylinder is completely sealed from the entire system with a check valve and there is no releaf valve to this part of tubing - it could be a base to recheck flaps in DCS P-51.

 

Obviously they cannot overcome physics....

You only have 1300 psi to work with. I got the operation of the check relief valve from the maintenance manual description. The only thing that bothers me is the small valve on the pressure relief valve that is part of flap system circuit. It does not say in the description if it fails to the closed position. I would call the P-51 mechanics and ask them that question as it is not clear in the description. It looks like that valve just returns fluid from the system back to the reservoir when the system is pressurized to prevent over-pressurization and that is what it says in the description. If that is the case, you would lose your hydraulic system as I described.

 

If it does fail in the closed position then it will lock the pressure in the flap system and your flaps are stuck.

 

Overspeeding would then damage the flaps, hinges, wing warping, and ultimately failure of the wing just like a mechanical system.

 

Very much, thanks. I guess the question is now, if you put the flaps full down, then force them to retract with speed, then, level out, should the go back to full down on their own, or do you have to move the lever up again and back down again (as it is in the sim right now I think).

 

Yes...it looks that way. And now you are low on hydraulic fluid or out!!

Edited January 21, 2015 by Crumpp

[MiloMorai]

In a P-51 without the uplock modification, your inner gear doors will deploy.

One would think that P-51s today would have the uplock modification.

[Solty]

One would think that P-51s today would have the uplock modification.

We are talking 1944/1945 here, so it doesn't matter what modern P-51 has.

Also, beautiful painscheme :thumbup:

[Crumpp]

We are talking 1944/1945 here, so it doesn't matter what modern P-51 has.

 

I think ours is a late 1944 model and probably has the modification. The technical order came out on 16 September 1944.

[MiloMorai]

Can we see a photo of this P-51?

[Crumpp]

should the go back to full down on their own, or do you have to move the lever up again and back down again (as it is in the sim right now I think).

 

It looks like you are going to have to move the lever and reset the system. The two check valves on the flap circuit will lock the incoming pressure in and overpressure on the outgoing side of flow to the pressure relief valve.

 

You will have pressure on one side and nothing on the other until you reset it.

[NineLine]

It looks like you are going to have to move the lever and reset the system. The two check valves on the flap circuit will lock the incoming pressure in and overpressure on the outgoing side of flow to the pressure relief valve.

 

You will have pressure on one side and nothing on the other until you reset it.

 

That makes sense.

[Crumpp]

Yo-Yo says:

And the way the flaps are realised in DCS corresponds to his answer. That corresponds my technical consideration, too.

 

Looking at the manual, it is correct.

 

Keep in mind we have a pump trying to equalize the system pressure drawing 2.5 gallons per minute from a 1.86 gallon reservoir so it will empty the reservoir in less than a minute.

[Friedrich-4B]

Also if you are over-speeding the flaps, and forcing them to retract, I assume by forcing some fluid from the system by some relief valve, would you not eventually cause yourself issue if you lost too much fluid? Obviously I see no good reason why a pilot would get to this point, but I wonder how much fluid you could expend before the system didn't operate correctly anymore.

 

There was a restrictor valve governing the flap's hydraulic system, so the pilot could not force the flaps to go down or retract faster than they were designed to. (see pages 283 - 285 of the pdf document) The hydraulic system for the flaps and undercarriage operated at 1,050 lbs in² +/- 50 lbs. According to the pilot's manuals the flaps took 10-11 seconds to move through 50 degrees; the speed restrictions ranged from 400 mph IAS for 10º to 165 mph IAS for the full 50º.

 

 

 

 

Keep in mind we have a pump trying to equalize the system pressure drawing 2.5 gallons per minute from a 1.86 gallon reservoir so it will empty the reservoir in less than a minute.

 

No we don't; the pump doesn't have to try equalising anything because that's what the unloading/relief valve is for. What we have is a pump circulating 2.5 gpm of fluid through the system - the only reason the reservoir would drain is if there was a major leak.

 

As it is, the E & M manual specified a flow rate through the unloading/relief valve of 3.5 gpm@ 1,000 lbs in². The relief valve operated when the pressure went over 1,100 - 1,250lbs in²

 

Edited February 22, 2015 by Friedrich-4/B
Remove duplicated page from pdf

[MiloMorai]

Great pdf F-4/B. :beer:

 

Nice to get the info all together and not in dribs and drabs.

 

I didn't notice any uplocks for the inner gear door.

[Outlaw24]

Nice pdf file great info!