Jump to content

self retracting flaps with NO hydraulic pressure


saburo_cz
 Share

Recommended Posts

Hello,

i have problem with flaps which retract when hydraulic pressure fails to zero during flight.

 

My engine died (propeller stops) during flight, but fortunately i had altitude to glide to home airport.

I lowered flaps to 30 degrease and i still had hydraulic pressure, so i downed landing gear normally and flaps suddenly went UP... My hydraulic pressure was zero when they started to retract.

 

I tried it of-line, and when i stopped engine during flight, i lowered flaps and then downed landing gear, no problem i still had hydraulic pressure thanks to rotating engine.

I had to lose hydraulic pressure by Hydraulic release knob and immediately after i did it, flaps started to retract.

 

It is the same for TF-51D.

 

Now i know why i lost several lives during emergency landing without engine...

F-14A/B

P-51D | P-47D | Mosquito FB Mk VI |Spitfire | Fw 190D | Fw 190A | Bf 109K |  WWII Assets Pack

Normandy | The Channel

F-86 | F-16C | A-10C | FC-3 | Syria | PG | NTTR | CA | SC |

Link to comment
Share on other sites

I don't know for certain, but if there is no hydraulic pressure, could it be air pressure is forcing them up?

if they are so easy to move, they should fall down after landing and stop plane, but they do not...

no, it is not that

F-14A/B

P-51D | P-47D | Mosquito FB Mk VI |Spitfire | Fw 190D | Fw 190A | Bf 109K |  WWII Assets Pack

Normandy | The Channel

F-86 | F-16C | A-10C | FC-3 | Syria | PG | NTTR | CA | SC |

Link to comment
Share on other sites

if they are so easy to move, they should fall down after landing and stop plane, but they do not...

no, it is not that

 

The size of the flap and amount of air pressure being exerted on it in flight would be very large. The fact that that amount of energy could move the flap is NOT an indicator that they are easy to move. In flight pressures on it would be much greater than on the ground relying solely on weight (of a piece no doubt designed to be as light as possible) to push it back down. I don't know for sure that the answer above was correct, but it certainly seems quite plausible/likely to me.

Link to comment
Share on other sites

  • 3 weeks later...
The size of the flap and amount of air pressure being exerted on it in flight would be very large. The fact that that amount of energy could move the flap is NOT an indicator that they are easy to move. In flight pressures on it would be much greater than on the ground relying solely on weight (of a piece no doubt designed to be as light as possible) to push it back down. I don't know for sure that the answer above was correct, but it certainly seems quite plausible/likely to me.

 

but it not seems quite plausible/likely to original flight P-51D manual, where is recommended to lower flaps in case of hydraulic pump failure and there is not any note about possibility to self flaps retract...

It seems to be a bug.

835681203_hydraulicpumpfail.PNG.84a055dad87dde0cb66fa98e4b6ecf80.PNG

F-14A/B

P-51D | P-47D | Mosquito FB Mk VI |Spitfire | Fw 190D | Fw 190A | Bf 109K |  WWII Assets Pack

Normandy | The Channel

F-86 | F-16C | A-10C | FC-3 | Syria | PG | NTTR | CA | SC |

Link to comment
Share on other sites

I don't interpret that extract as saying it recommends lowering the flaps on hydraulic failure, it is saying there is still enough hydraulic pressure to lower them, and that the undercarriage can be allowed to fall down without the need for hydraulics.

 

However, as there is clearly a reserve of hydraulic pressure despite a system failure, that could be why they remain retractable as the original poster states.

 

Have you tried cycling them, and seeing how often they can be retracted, and if in fact at that point they remain down due to a lack of pressure?

Link to comment
Share on other sites

Saburo, the fragment You posted doesn't contradict anything rob10 wrote above, and certainly doesn't support anything You claim. It mentions hydraulic accumulator, though, which should allow emergency operation as long as the pressure in it is above 800 PSI (not surprising, as this is also a minimum normal pressure maintained in the hydro system when the engine pump works). There's no mechanical gearing or lock in the Mustang's flaps system, their position is held by the single hydro actuator only (as seen on the drawing below), so when the pressure drops to zero (for whatever reason), they'll be pushed back by aero forces (just like all other control surfaces, when there's no input force from the pilot).

 

The only thing that could be argued as a potential bug is whether they should drop without pressure when on the ground - some say they should, other say they should, but only a little and very slowly, the others say no. The topic was discussed (amogst other things) on this forum anyway...

https://forums.eagle.ru/showthread.php?t=118488

 

... and the other forums as well:

http://forum.largescaleplanes.com/index.php?showtopic=38436

 

Personally, I was never bothered or patient enough to sit on the ramp with time acceleration on, waiting to see how they'll behave after a while.

hydro.jpg.12144a557dbccdc3adae71cc8554ea21.jpg


Edited by Art-J

i7 9700K @ stock speed, single GTX1070, 32 gigs of RAM, TH Warthog, MFG Crosswind, Win10.

Link to comment
Share on other sites

 Share

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...