Jump to content
Sign in to follow this  
spartan85

P-51 shut down procedure (hydraulic pressure release)

Recommended Posts

Hey just a quick notice... but on shut down of the P-51.. isn’t the last thing to do is release the hydraulic pressure from the system?

i know it’s automated shutdown.. but those gear doors don’t look right if there not hanging down when the ship is parked...

 

what i’ve Done to work around this little mishap... is cycle the flaps up and down, the pressure will bleed off and eventually zero... 

then if you cycle gear down and up, the gear doors will lower and stay put :)

image.jpg

image.jpg

I know it’s a game... but safety first right!?

  • Like 1
  • Thanks 1
  • Upvote 1

Share this post


Link to post
Share on other sites

You are telling me that, after turning off the engine, you can bleed the accumulated hydraulic pressure by using the flaps until its all gone? And that the wheel doors will then droop down?

 

This game always surprise me. 

 

That being said, shouldn't the flaps also drop down after all the pressure is spent? 

Share this post


Link to post
Share on other sites

When I tried it first time I am sure the flaps just hanging there. And it was the air resistance that made them come up. I might remember wrong 

Share this post


Link to post
Share on other sites

They should, but, meh... 

The ship starts off with everything non-pressurized...

but the shut down just needs to be fixed

Share this post


Link to post
Share on other sites

Please scroll down

 

 

#2

 

Brief description: P-51D Hydraulic pressure release / intended or not? No bug or bug?

 


Detailed description, conditions: After stopping the engine in the P-51D Mustang the hydraulic pressure is not released. This means that the inner gear wheel doors and the flaps are not falling down. The pressure should be released for safety. This safety mechanism  forbids  activating the landing gear while on ground. By releasing the hydraulic pressure flaps and inner wheel doors are falling down.

(There is no pressure in the hydraulic system when starting the aircraft. You can clearly see flaps and inner gear doors are down.)

 

 

 

I have posted this on

 

Graphics, models and maps

By BlackSix, October 27, 2014 in Technical Issues and Bug Reports

  • Thanks 1

Share this post


Link to post
Share on other sites

Was  there actually a step in the check list to release the hydraulic pressure from the system? I have seen many pictures from WW2 of parked P-51s with the gear doors in a variety of states from all the way up, partially down and all the way down.

 

22853304_10211238908623886_1606003533175263274_n.jpg

22769607_10212605280860907_3196603004449568442_o.jpg

22814220_10210410985172236_8534695505524156484_n.jpg

Share this post


Link to post
Share on other sites

I always understood the inner gear door came down over time as the pressure released from the system. It should not release right at shutdown. I've never heard of it being part of the shutdown procedure either.

Share this post


Link to post
Share on other sites

Not in the checklist, but there is the pressure release handle next to the base of the control column in the cockpit. Useful for parking the aircraft for longer durations easing strain on the system. Then IIRC both gear doors open and flaps drop.

 

If you see partially opened gear doors, it would indicate that the aircraft has been stationary for some time and pressure is dropping. This makes the first picture you posted a staged one.

Share this post


Link to post
Share on other sites

After the pressure valve is pulled and releases the system will gradually depressurize, so while the gauge should read zero/nil, in reality the pressure will bleed off over time. The doors that are partially open simply indicate the shut down was more recent and the system is calming down. 

Share this post


Link to post
Share on other sites

I did mention the need to depressurize the hydraulic system after the shut down items by pulling the pressure release handle right after release of the P-51.

It is a safety feature and makes sense, if you don´t put the flaps up and down to depressurize the System it keeps pressurized and you can retract the landing gear on Ground while parked…...try it.

 

Besides this……..there is a need to switch off the magneto switches after engine shut down ( which stays on all the time untill next engine start sequence ) and switching off the fuel booster pump after take off and landing ( it is switched on all the time, which is not correct ), the fuel booster pump is normally only on for take offs and landings.

Edited by spitfirejoe

Share this post


Link to post
Share on other sites
5 minutes ago, spitfirejoe said:

I tried to retract the Landing Gear on Ground while parking with engines off and it does retract.

Well that's exactly what the quote says it would do in the D model!! The WoW mechanism was removed.

Share this post


Link to post
Share on other sites

Oh sorry, then I misunderstood something, now it´s clear. Anyway I wish the hydraulic sytem would get depressurized. 

Share this post


Link to post
Share on other sites

This is a video from Kermit Weeks, at 10:50 he releases the hydraulics as part of shut down 

 

 

 

Share this post


Link to post
Share on other sites

I mention the various states of the gear doors because I build P-51 models and I noticed that most photos I found showed then in the up position for parked aircraft. I wanted to present my model in a typical pose.

I found this link which contains a multitude of stories about flap and gear door procedures. 
https://forum.largescaleplanes.com/index.php?/topic/35864-p-51-landing-gear-doors-a-totally-unscientific-survey/
 


This was an interesting post from the above link:

 

 

hydraulic system.jpg

  • Thanks 1

Share this post


Link to post
Share on other sites
4 hours ago, RadicalFizzbin said:

I mention the various states of the gear doors because I build P-51 models and I noticed that most photos I found showed then in the up position for parked aircraft. I wanted to present my model in a typical pose.

I found this link which contains a multitude of stories about flap and gear door procedures. 
https://forum.largescaleplanes.com/index.php?/topic/35864-p-51-landing-gear-doors-a-totally-unscientific-survey/
 


This was an interesting post from the above link:

 

 

hydraulic system.jpg

Interesting!   

Share this post


Link to post
Share on other sites

The D-5 Flight Manual (April 5, '44) does not mention depressurizing hydraulic system.  All it says is turn off ignition after prop stops then shut off fuel selector followed by 1) turn off all switches, 2) set park brake (not while hot), 3) Lock controls, 4) carb air to alt, 5) disco canopy crank from canopy and push canopy closed manually after exiting.  (Paraphrased in the extreme.)

 

  I think I have seen somewhere where it was recommended to relieve the pressure to make it easier the mount/dismount without stepping on the flap - I think it was a training film.

 

Also, the landing gear will not retract on the ground (the tailwheel will) unless the aircraft is moving as the hydraulic system doesn't have the power to slide the tires sideways across the ground with the weight of the aircraft on them.  The worst that could happen (other than the tail sitting on the rudder) is if there was an inboard preload on a/the gear leg the downlock(s) could unlock without being able to relock with the repositioning of the handle.  If the aircraft was then moved the leg(s) could then creep toward retraction while rolling.  Of course, this wouldn't be likely as someone would probably notice the half retracted tailwheel and damaged rudder/aft fuselage.

 

I've worked on a couple of planes (727 and 757) where handles went up without gear pins and in both cases it was only the nosegear that retracted causing more than enough damage ...

Share this post


Link to post
Share on other sites
On 10/19/2019 at 10:16 PM, chuter said:

The D-5 Flight Manual (April 5, '44) does not mention depressurizing hydraulic system.  All it says is turn off ignition after prop stops then shut off fuel selector followed by 1) turn off all switches, 2) set park brake (not while hot), 3) Lock controls, 4) carb air to alt, 5) disco canopy crank from canopy and push canopy closed manually after exiting.  (Paraphrased in the extreme.)

 

  I think I have seen somewhere where it was recommended to relieve the pressure to make it easier the mount/dismount without stepping on the flap - I think it was a training film.

 

Also, the landing gear will not retract on the ground (the tailwheel will) unless the aircraft is moving as the hydraulic system doesn't have the power to slide the tires sideways across the ground with the weight of the aircraft on them.  The worst that could happen (other than the tail sitting on the rudder) is if there was an inboard preload on a/the gear leg the downlock(s) could unlock without being able to relock with the repositioning of the handle.  If the aircraft was then moved the leg(s) could then creep toward retraction while rolling.  Of course, this wouldn't be likely as someone would probably notice the half retracted tailwheel and damaged rudder/aft fuselage.

 

I've worked on a couple of planes (727 and 757) where handles went up without gear pins and in both cases it was only the nosegear that retracted causing more than enough damage ...

The RNZAF's Pilot's Notes for Mustang P51D stipulated that the pilot release the hydraulic pressure; see 70. Stopping the Engine  Paragraph (e).  Chances are, operational experience led to the procedure being adopted later in the war, which is why it wasn't mentioned in the D-5 Flight Manual. Also note that the flaps were lowered to prevent people standing on them - para (d).

Initially, the P-51D relied on hydraulic pressure alone to keep the undercarriage retracted: after some Ds were lost because the undercarriage started to extend during high speed manoeuvres, landing gear uplocks were field fitted to earlier P-51Ds and factory fitted to later block numbers.

North American P-51D RNZAF PNs1.jpg

North American P-51D RNZAF PNs40.jpg

Edited by NZTyphoon
Flaps lowered.

Share this post


Link to post
Share on other sites
On 10/20/2019 at 7:54 AM, NZTyphoon said:

Also note that the flaps were lowered to prevent people standing on them

 

Its funny how sometimes we look for the technical reasons for a given design choice or procesure, when it can be just a simple human reason like that.

Share this post


Link to post
Share on other sites

If the hydraulic pressure is released on shutdown, then wont that cause loss of control issues should you need to turn off the engine in-flight due to damage?

Share this post


Link to post
Share on other sites

No Kat. The Mustang didn't have hydraulically operated controls. This is 1944, Bud. Simply cables leading to the control surfaces.

15 minutes ago, Kataphrakt said:

If the hydraulic pressure is released on shutdown, then wont that cause loss of control issues should you need to turn off the engine in-flight due to damage?

 

  • Like 1

Share this post


Link to post
Share on other sites
Just now, Poochnboo said:

No Kat. The Mustang didn't have hydraulically operated controls. This is 1944, Bud. Simply cables leading to the control surfaces.

 

Thanks! I'm mostly used to modern jets.

Share this post


Link to post
Share on other sites
On 10/19/2019 at 5:16 AM, chuter said:

The D-5 Flight Manual (April 5, '44) does not mention depressurizing hydraulic system.  All it says is turn off ignition after prop stops then shut off fuel selector followed by 1) turn off all switches, 2) set park brake (not while hot), 3) Lock controls, 4) carb air to alt, 5) disco canopy crank from canopy and push canopy closed manually after exiting.  (Paraphrased in the extreme.)

 

  I think I have seen somewhere where it was recommended to relieve the pressure to make it easier the mount/dismount without stepping on the flap - I think it was a training film.

 

Also, the landing gear will not retract on the ground (the tailwheel will) unless the aircraft is moving as the hydraulic system doesn't have the power to slide the tires sideways across the ground with the weight of the aircraft on them.  The worst that could happen (other than the tail sitting on the rudder) is if there was an inboard preload on a/the gear leg the downlock(s) could unlock without being able to relock with the repositioning of the handle.  If the aircraft was then moved the leg(s) could then creep toward retraction while rolling.  Of course, this wouldn't be likely as someone would probably notice the half retracted tailwheel and damaged rudder/aft fuselage.

 

I've worked on a couple of planes (727 and 757) where handles went up without gear pins and in both cases it was only the nosegear that retracted causing more than enough damage ...

Oh yeah! I did 37 years with American Airlines. Saw it happen more than once! We had two guys up in the cockpit working on the gear lever. They were working it up and down , up and down. A guy on the ground comes along and needed a gear pin to tow a plane down to the hanger. He walks away with it and.....oops! Guys in the cockpit nearly had heart attacks!!

Edited by Poochnboo
  • Like 2

Share this post


Link to post
Share on other sites

I think it would be neat to incorporate this resting state of the P51 in the hangar menu if at all possible. 

Share this post


Link to post
Share on other sites
On 10/20/2019 at 12:54 PM, NZTyphoon said:

Also note that the flaps were lowered to prevent people standing on them - para (d).

 

This was also done with the P-47 for the same reason, see below in official training film from about the 14:10 mark, where the instructor points it out to the pilot during familiarization training. It'd be nice if the P-47 in game was like the P-51, flaps down, when you start from the parking.

 

 

Edited by Pict
Spelling, tweaking etc.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×
×
  • Create New...