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hydraulic flaps

tcraft128

FRIEND
St. Marys GA; GA36
I remember reading about a plane with hydraulic flaps with a dump. I have searched for some pics. Are there any of how the system works? Thanks for the info.
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I've daydreamed about that before using clutch slave cylinders.
speedway link
556NP102U_L.jpg
 
tcraft128 said:
I remember reading about a plane with hydraulic flaps with a dump. I have searched for some pics. Are there any of how the system works? Thanks for the info.
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Think safety if you are thinking of doing this. Think of the worst case scenario of one flap up and the other one down. Will you have enough aileron control to oppose the split flap? If not, then you should tie the flaps together some how, torque tube?, bus cable? For a certified airplane this is an FAA requirement.
 
I have flown Mikeo's setup. I really liked it. The flap release is a trigger on the stick.. It was very natural to release the flaps and still have your hand on the throttle. I can picture lots of wind related situations where this would come in handy. Liked it alot.

Mark
 
I think it's time for me to add a flap dump system to my existing flap handle. I can't convince myself getting my hand off the throttle on landings...

The only good pic I have comes from DA.
But I can't really understand how his setup really works:

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Here is a simple diagram that I think would also work.






Cylinder is extended flaps up, and closed full flaps
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Does 1/8 npt will dump fast enough if flow control is all the way open???



Any advice would be very helpfull.
 
Dump Valve.png
Funny, i am also working on this right now. This is for my overhead design and uses a 2 way electric valve.
 

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I think it's time for me to add a flap dump system to my existing flap handle. I can't convince myself getting my hand off the throttle on landings...

Does 1/8 npt will dump fast enough if flow control is all the way open???
Probably, that depends on the strength of the return force (spring?) and whether you are on the ground or in the air (air loads against the flap). The word "dump" to me means extremely rapid as in right now, abrupt. Quickly and smoothly would be more desirable.
 
I remember reading about a plane with hydraulic flaps with a dump. I have searched for some pics. Are there any of how the system works? Thanks for the info.
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Talk to DW the last time I saw his plane he had hydraulic flaps with dump system.
 
I considered hydraulic flaps on my experimental Supercub but saw more negatives than positives. Hydraulic flaps need a mechanical connection or they will not extend or retract equally. Dual master & slave cylinders will solve that problem, but is more complex, heavy & nasty (oil). I decided to go with a simple overhead handle with push-pull rods.
 
For sure the only positive is dumping the flaps with the hand still on the throttle. But I think it is worth giving it a try.

Downsides I see are: more complex, 4 pounds max, time and $
 
I considered hydraulic flaps on my experimental Supercub but saw more negatives than positives. Hydraulic flaps need a mechanical connection or they will not extend or retract equally. Dual master & slave cylinders will solve that problem, but is more complex, heavy & nasty (oil). I decided to go with a simple overhead handle with push-pull rods.

Not true. The system to which I was referring uses the stock cables,handle, and pulleys. The mechanism is hidden behind the side panels. Only you know it is there. I had a long discussion with Mike Olsen at JC 2015 about his system. He offered to put me in touch with his guy. Said the cost was around $1000.
 
For sure the only positive is dumping the flaps with the hand still on the throttle. But I think it is worth giving it a try.

Downsides I see are: more complex, 4 pounds max, time and $

The positive for me at 6'4" is that my flap handle is shortened and dumping the flaps requires me to lean forward at a crucial moment. I am not familiar or comfortable with that.

With the hydraulic dump, I can remain in a normal seated position.
 
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Hydraulic flaps need a mechanical connection or they will not extend or retract equally.
Extending or retracting equally is not as important as you imagine. As long as the system is not binding somewhere more on one flap than the other, the air loads will balance the flap position in flight. You'll never be aware that there was a difference. Full down flap would be even. Full up flap would be even unless there is a mechanical restriction (tight hinges maybe or whatever else prevents Cub flaps from fully retracting?) preventing the flap from going full up. To be certified without any mechanical connection you will have to demonstrate full aileron control with one flap down and the other locked up in a crosswind. If it is not controllable in this condition you will need either a flap indicator on each flap or the two flaps must be bused together mechanically. That could be as simple as just one balance cable between the bellcranks in each wing.

A flap hydraulic system could power the flaps in both directions or just down with a spring used for up. With a spring return you would only require one hydraulic line where the other would require two.

Another option which would take up more space due to the large size of the actuator, would be pneumatic vacuum. The Stinson V-77 and Waco VMF-7F had vacuum systems. You could leave the control valve on the Stinson down all the time, not that you'd want to. The air loads would control the flap position. On a go around they would automatically retract. These systems were difficult to modulate to an intermediate setting.

On a Super Cub you could attach one actuator behind the baggage compartment to the existing flap cable. This actuator should have a return spring, either internal or external only for the purpose of returning the piston to the flap up position. One hydraulic line to the actuator pump with a lever/button actuated spring loaded check valve mounted wherever you want it between the pump and actuator. To operate, just pump a handle the desired amount for the down flap. To retract just push the lever on the spring loaded check valve for the desired amount of retract. If the flaps retract faster than desired, a restrictor (full flow in one direction, restricted in the other) check valve can be inserted in the hydraulic line.

Make the area of the actuating piston large enough to provide the force against the full air pressure against the flaps. The pump would have a much smaller area so that the pumping forces are low enough for comfort and finite flap position adjustment. You could jury rig a spring scale to the existing flap cable in order to determine the required force. Then it would just involve a few simple calculations to determine size of components only if you wish to get fussy with your design. Make sure that the actuator has enough travel for full flap operation. Rather more than not enough would be preferred.

Rather simple once you put your mind to it. Just a bit of labor to make it happen. Oli is a clever guy, I'll bet that he could make the entire system in his shop without a great deal of expense.
 
Just remembered, Oli's flap handle is overhead. He could make the entire system to replace the current one with no or minimal hydraulic lines. Just a mechanical link down next to the throttle for retract.
 
I think it's time for me to add a flap dump system to my existing flap handle. I can't convince myself getting my hand off the throttle on landings...

The only good pic I have comes from DA.

Does 1/8 npt will dump fast enough if flow control is all the way open???



Any advice would be very helpfull.
Oli my friend, I have some detailed pictures that I'll post later tonight. The flap dump system in my Cub was an early experiment by Cub Crafters. It was a pneumatic industrial cylinder with a simple electric check valve. Check valve one way, electric open the other. The problem with the system at first is that it raised the flaps TOO fast. It was like the cable broke. They then added fluids of different viscosity to calm the thing down. It is a dirt simple system, connects to your existing flap handle in place of the ratchet and frees up a hand during landing. Very cool, very simple system.
 
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