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Emergency flap brake valve...set or not?


ShadoFE
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Ok, I have a question regarding the emergency FLAP brake valve. After takeoff the flaps stopped retracting at 40%. C/B checked good so I went to the emergency flap brake valve. (Don’t worry I didn’t reset it). The valve reset lever was full forward (to the right when looking at it) and had no “free playâ€. I took this to mean it was engaged, however, after shutdown MX ran the flaps through and the valve was in the same position…flaps working fine. (FYI, water in the switches was not a factor)

My question is… What does the emergency brake valve look/feel like when it is engaged?

Thanks for the help!

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It will be rigid "no free play" sounds like the emergency flap brakes were engaged. When you say the valve was in the same position was it still "no play" or did they move the lever?

If you shutdown (no electrical) and the valve lever is moved the valve will be reset.

If this happens again have them try and move the flaps with electrical power still on the aircraft. (the hyd pressure is held in place by check valves)

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The lever was found to be "hard right" with "no free play" in flight during the malfunction. After landing we have to shutdown before MX can board (part of the radiation checking procedures here for the Japan earthquake relief) but power did remain on. When I did make it to the back again after shutdown (power still on) the valve lever had its usual preflight "free play". (someone may have reset it before I got there) As soon as MX tied the ground test valve and turned on the aux pump the lever shot to the right and had no free play anymore (just as it was in flight), but the flaps ops checked good. This is what has me questioning what I thought I've known all along. I'm not suprised the flaps ops checked good, flase asymetric indications do happen sometimes. I'm just suprised the valve was "hard right" again. I've always thought when the valve was hard right with no free play anymore...it's engaged and must be pushed left to reset it. If that was true then I just watched the flaps move with the emergency flap brake "engaged"...with would indicate a bad emergency flap brake...but it DID work in flight by stopping the flaps at 40%. Soo...I don't think there is any malfunction here...I just want to be sure I know what I'm looking for when checking the lever during a malfunction because these things have a habit of coming back if water is not involved.

How "stiff" is the lever suposed to be inflight when it is unset vs set?? When I check it I'm just seeing if there is any free play (like preflight). I don't use much force because I don't want to acidentaly reset it in flight.

Thanks again for the help!

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The quickest and best way to identify if your emergency flap brake valve has been energized is to follow your procedures under "Overriding Flap Selector Valve (Electrical Malfunction)". If the emergency flap brake valve has been energized to the locked position there will be no hydraulic pressure available to the flaps selector valve for override operation. When the flaps stop moving and the CB is not open this does not indicate there is no electrical problem. This is why the hydraulic overriding is the first step for flap system failures.

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The emergency flap selector valve has hyd pressure to both sides during normal operation so it may appear to be tripped (not as wiggly as in preflight w/ no hyd pressure on the valve).

We have a trainer for the flight controls I will put a scale on the lever to see how much force is applied and how much you would need to put on it to make it move "untripped".

You cannot move it if it is tripped as the 3000 psi will push the valve to one side and the other side (of the valve) is ported to return.

3000 vs 0, pretty easy to see which will win....

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Thanks for the replies...

I'm seeing that the answers so far fall into one of two categories...

1. If the valve is "hard right" it is set. (This is what I believed for about 10 yrs. I believe I've now found this to be false...I've found the valve to be "hard right" during normal operation. Either something is not working correctly or I've been wrong!)

2. There is no way to visually verify the position of this valve. Attempt to move the flaps via another method to confirm. (e.g. hydraulic override)

The theory here being IF the valve is energized it is bypassing all fluid away from the flap selector valve and applying 3000psi to the emergency flap brakes. Now both sets of flap brakes are engaged to hold them in place. No pressure will be available to the flap selector valve...so if nothing happens...the valve is indeed set. Also, to take it one step farther, even if someone were to pull the manual drive engaging handle this would only disengage the normal spring applied brakes leaving the emergency flap brakes applied and the flaps still should not move. To put it simply, if the valve is energized the flaps WILL NOT move by any means. If it is not, the flaps will move via the normal manual override procedures.

I agree with this method, however, I have a few trouble spots to get past.

1. The flight manual clearly states that if the flaps stop moving before reaching their desired position you are to "position the flap lever to correspond to the position of the flaps and NO FURTHER INFLIGHT MOVEMENT OF THE FLAPS SHOULD BE ATTEMPTED" (Probably not written by a FE!!)

2. Did someone REALLY design this valve with no means of visually determining whether or not it is set or not!?!?!? (poor design if that's true)

Let me be clear, as the FE, I have no trouble trying to move the flaps to verify if the emergency flap brakes are set. I understand that IF it is set...nothing will happen...good or bad. If it is not and the flaps stopped moving due to another electrical malfunction...then we get our flaps back and there will be much rejoicing!! On this particular day I did recommend to the AC that we try just that. However, we were close to home with good weather and plenty of fuel so he preferred to just not mess with it. Sound logic I felt no reason to argue with.

I sure hope there is a way to visually determine if this valve is set or not. If not, be prepared to explain your systems knowledge to the AC because they will not want to attempt further movement of the flaps.

Thanks again for the discussion!

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May I suggest a simple test in order to clarify the issue?

Aircraft power applied, ground test valve tied, flaps operating normally. Check the brake valve lever to see how it feels. (on an aircraft other than the one in question).

Up behind the aileron boost pack at the testing terminal board, while flaps are moving, jumper the test terminals as the maintenance manual states and trip the assemetry brakes. When the flaps stop, remove the jumper wire and go back and check the brake valve lever. See if it now feels different and actually reset it. Notice the difference.

That will hopefully clear up any questions that you may have. Only takes a couple minutes to do, and it will leave all interpretations of schematics and system diagrams out of the equation.

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OK, just came back from the plane. With the utility pressure at 3000 PSI, the lever is pushed to the right. Turning the pumps off releases the lever. When the flaps lock up, the lever will be pushed to the right as well. The difference is that when the pumps are turned off, but pressure is not bled down, the lever stays "hard right." However, is you bleed off the hydraulic pressure after turning the pumps off, the lever releases and the flaps will move again.

The only way to know, in flight, if your assymetry brakes locked up the flaps is to have the co-pilot turn off the pump switches and see if the lever moves easily. If they are locked, the lever stays "hard right." Once on the ground, if you happen to bleed off the utility system pressure, you cannot prove that they were locked when you landed.

If it were my problem, I'd reindex the brake switches at that point if the flaps appear to be good.

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Thanks for trying this out!

I think this definitively answers the original question….

Q. What does the emergency brake valve look/feel like when it is engaged?

A. It looks like it always does! The lever is pressed hard right anytime the utility system is pressurized.

It seems there is no way to visually determine if this valve is energized.

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  • 5 years later...

So i read and understand all the insight to these Qs and As. Giving that after reading thru the FI and GS we have a plane that flaps locked up in flight. After trouble shooting the A brakes are rigged good, and the signal coming from them is good at the cannon plug. But with power and hyd pres. The manual switch moves with some force but will not reset. The flaps move manually but the hyd brake is locked and they will not move with hyd. The FI does not specify this problem and i am only 3 yrs into this plane. Im thinking bad brake valve. Any thoughts?

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Anytime you have utility pressurized, the handle with be pushed to the right and will have resistance to move it to the left.  It will feel like it is spring loaded.

IF, the emergency brake valve is tripped (electrical/asymetry issue), the handle will stay to the right even after you depressurize.  The check valve above the brake valve locks in that pressure so that asymetry brakes will stay fired even if you also lose utility system.  In order to reset the valve, utility must be depleted AND then the valve must be pushed to the left (will feel like initial spring pressure and then it will go loose)

You should not (in proper working system) be able to reset brake valve when pressure is applied.  If you trip the brake valve and deplete utility, the asymetry brakes can stay set for days depending on how good the check valve is.   Its only once you deplete and reset handle that the valve will internally shift.

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hehe,

There's more than one type of e valve.  There are some that have a knurled knob that resembles the wheel brake accumulator relief valve in the nose.  So not all have the old flapper-type of valve lever.

In my opinion, the true way to verify is to see if the e valve is bypassing utility pressure to the flap control valve by trying to move the flaps manually at the flap control valve with utility pressure.

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AMPTestFE,

I'm a hydraulic troop, worked everything from 1961 to 2013.  The odds of him having the old style with knob is slim to none.  The knob style operates the same anyway, just a different style manual reset.

And I agree that manually operating the flap control valve is quickest way to check for a set brake valve (in a proper working system anyways), I have seen brake valves bypass internally and send pressure to both the flap control valve and to the brakes at same time.

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  • 5 years later...

@hehe thanks for sharing your comments, found it very valuable in understanding the assymetric brake system.

we also had a case of flaps being stuck at 40% during landing, using the knob style emergency flap brake valve.

Upon landing and during our ground test, the flaps worked normally.

You mention that you ever experienced internal leakage of brake valves.
Would such a leakage cause the brakes to activate, but yet not "latch" the valve/button and trap pressure?

We suspect that because they were not latched, the hydraulics that activated the brakes in-flight was allowed to return to the utility reservoir when pressure was depleted,
hence the system worked fine during our ground test.
 

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On 10/10/2021 at 3:53 PM, benjamin92 said:

@hehe thanks for sharing your comments, found it very valuable in understanding the assymetric brake system.

we also had a case of flaps being stuck at 40% during landing, using the knob style emergency flap brake valve.

Upon landing and during our ground test, the flaps worked normally.

You mention that you ever experienced internal leakage of brake valves.
Would such a leakage cause the brakes to activate, but yet not "latch" the valve/button and trap pressure?

We suspect that because they were not latched, the hydraulics that activated the brakes in-flight was allowed to return to the utility reservoir when pressure was depleted,
hence the system worked fine during our ground test.
 

When you say you had flaps stuck at 40%............

Handle could still move from full up to 100%?  Utility pressure was solid around 3k when trying to move flaps?   Did it trip when flaps were going up or down?   Did you find water in the asymmetry brake switches?

Reason I ask these things is because 40% is a very specific range where a lot of crews induce their own "flap failure" issue that is just operator error.

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18 minutes ago, hehe said:

When you say you had flaps stuck at 40%............

Handle could still move from full up to 100%?  Utility pressure was solid around 3k when trying to move flaps?   Did it trip when flaps were going up or down?   Did you find water in the asymmetry brake switches?

Reason I ask these things is because 40% is a very specific range where a lot of crews induce their own "flap failure" issue that is just operator error.

Yes the handle, utility pressure was good.

Flaps were coming down from 0% on approach.

No water was found, but the switches did look worn probably due to long hours of installation.

I became quite curious too after noticing that other operators had the flaps stuck at the same specific point.

Could you elaborate more what is meant by operator error and how it could have induced the defect?

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2 hours ago, benjamin92 said:

Yes the handle, utility pressure was good.

Flaps were coming down from 0% on approach.

No water was found, but the switches did look worn probably due to long hours of installation.

I became quite curious too after noticing that other operators had the flaps stuck at the same specific point.

Could you elaborate more what is meant by operator error and how it could have induced the defect?

So they went from zero to 40% flaps and the handle stopped or flaps stopped?

If the handle stopped moving, I know exactly what caused it.

If flaps stopped, the handle would be at 100% but flaps would only be at 40%.

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16 hours ago, hehe said:

So they went from zero to 40% flaps and the handle stopped or flaps stopped?

If the handle stopped moving, I know exactly what caused it.

If flaps stopped, the handle would be at 100% but flaps would only be at 40%.

The handle was working fine but it was the flaps that stopped.

Although, do you mind sharing what could have caused the handle to stop?

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4 hours ago, benjamin92 said:

The handle was working fine but it was the flaps that stopped.

Although, do you mind sharing what could have caused the handle to stop?

If the handle locks up at 40% it is almost always because someone pulled the UP lock lever while lowering flaps.  The lock and flap lever interfere with each other in this state and lock the handle up.

What model of C-130 was this? 

 

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