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wrbrdmech

HK Models hinting at 1/32 B model P-51!

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My unscientific survey of every single photo in every single P-51 or related book I owned at the time (which IIRC amounted to several hundred photos) showed about 75% of them with the clam shell doors either fully closed, or hanging partly open as in the photo above.  Only around 25% of the time were they completely open.  Which totally squares with what both WWII P-51 crew chiefs and current P-51 owner/mechanics have told me about the hydraulic system of the Mustang.  With power off, **some** bleed down of pressure will allow the doors to eventually drop partly open.  Only by dumping the pressure on the gear system (via a handle in the cockpit) will they open completely.  That was only done if the crew chief needed to be in there for some reason.  As soon as power is turned on and hydraulic pressure is built up, the doors will move to the fully closed position.  They cycle fully open and fully closed during gear extension/retraction.

 

 

Them's the facts.

 

PS:  The flaps DO NOT bleed down.  The first thing a crew chief did with residual hydraulic pressure after the pilot departed the airplane was to drop the flaps so the armorers and fuelers could have better access to the upper wing, and so they wouldn't damage the delicate trailing edge of the flaps.  If the engine were run (by the crew chief), he'd raise the flaps to clean the airplane up.  Flaps deployed and gusts of wind don't do good things for airplanes on the ground.  Even if you dumped all hydraulic system pressure and the flaps were up, their geometry and internal workings would keep them in the up position.  They had no tendency to fall down to the deployed position on their own.

Edited by Jennings Heilig

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My Take on the clamshell door issue (without having looked at the hydrauic system schematic in a while):  Without positive hydraulic pressure (caused by said dump of hydraulic system pressure with the cockpit control) in the clamshell door actuators holding the doors closed, the weight of the doors (mass x gravity) will overcome the static pressure in the actuator which will cause the doors to open albeit very slowly (there are no mechanical uplocks for the clamshell doors when the gear is down and locked) especially if the seals are tight.  The fluid that was in the "upside" of the actuator will be displaced back to the reservoir.  Eventually, if left alone for the right amount of time, those clamshell doors will open most of, if not all the way.  From what Jennings has observed, that amount of time may be longer than the "between sortie time". 

Edited by Juggernut

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I don't want to go into the full argument, but since this thread is about the B/C, isn't it true the B/C had mechanical system so the doors stayed up? Or was that the A I am remembering?

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What I've always understood is that all of the P-51's had their landing gear doors and flaps controlled by a hydraulic system and that when the system was pressurized, the interior landing gear doors would be up. When everything was shut down and the hydraulic pressure would bleed off, sometimes over several hours, the doors would gradually descend. This is why Weser them in all sorts of positions. I don't know for sure about the flaps, but I'm pretty sure the they would descend too with the bleed-off of hydraulic pressure-- I just don't know if it was gradual or not.

Bill M.

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When I converted my Hobbycraft Mustang IA back to a Mustang I (you can see it here, if you like http://forum.largescaleplanes.com/index.php?showtopic=30710&hl=  my research indicated that Allison engine Mustangs had mechanical latches which locked the landing gear doors in the up position when on the ground. This latch could be mechanically released for maintenance, if required.

 

From what I remember this did not apply to B/C/D Mustangs.

 

Dave/Ironman1945

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Yes, the gear doors would bleed.  But it's not an all or nothing thing.  That's why you see them hanging partly open - sometimes barely open and sometimes half open.  When pressure bleeds off, some residual pressure remains.  It won't bleed down to zero unless something is seriously wrong with the system (like it's completely out of fluid).  They reach a certain point and there's an equilibrium and they don't go any further.  If they're hanging completely open, it's because the crew chief dumped all the pressure to them to gain access to the well.  

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When I converted my Hobbycraft Mustang IA back to a Mustang I (you can see it here, if you like http://forum.largescaleplanes.com/index.php?showtopic=30710&hl=  my research indicated that Allison engine Mustangs had mechanical latches which locked the landing gear doors in the up position when on the ground. This latch could be mechanically released for maintenance, if required.

 

From what I remember this did not apply to B/C/D Mustangs.

 

Dave/Ironman1945

That is what my feeble memory was trying to recall! So it was A's then. From B's on it was simply hydraulic. Thanks, Dave!

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It should be clear to HKM that a lot of folks are drooling for the 51B/C. Every day you wait is money lost. BTW I have been working for some time on a Trumpy/ZM Frakenstang. All looks good except for the not laminar flow wing. I am sure that the day after I finish it, the HKM kit will hit the shelves...soooo back to work.

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Personally, I'll wait as long as it takes for a good B model. I have so far. Hopefully I can get a couple, as I have a couple favorites I'd like to represent. You can guess which one I'll do first, just look at my avatar (hint hint)!

 

:whistle:

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Hopefully, the past is no indicator of how things will proceed on the B/C stang for HK............................as in Tamiya coming out with one around the same time. I have a feeling that is NOT the case, as Im firmly in the belief that Tamiya will give us a Jug (hopefully a razorback) in 32nd and not a B/C Mustang, but you never know, as Tamiya-san seems to do whatever his heart desires.

 

As to the HK P-51 B/C, Im really looking forward to this one. Im firmly of the opinion that if the above does not happen, and the model is researched well, and is molded accurately, this could be the biggest gold mine for them ever.  

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