Hello modelers, i was reading an article regarding the P-51D and says that when the engine was stopped the flaps would slowly drop due to a lack of pressure in the hydraulic system, but my question is, if i want to build a more-less accurate P-51B or an A-36 or an F-6B should i cut the flaps and glue them in the dropped position[%-)]?? thanks in advance, i am sure that someone out here may help me out[:D]
thanks a lot!
My best regards
Me.
[X-)]
Both the flaps and wheel bay doors would slowly droop as hydraulic pressue bled down. If you drop the flaps, you should pose the wheel bay doors down as well. If you leave the flaps up, the doors should also be up. Either would be correct, just depicting a different point in time.
That would be up to you if you “want” the flaps down. Who is to say the aircraft didn’t just shut down? Then this happens over a periof of hours not minutes. Also the main gear doors “droop” and if one actuator has a small leak one will drop faster than the other. So you could have a bird with with the flaps half way down, one gear door further open than the other. If you are modeling a particular “moment in time” and using a picture of the aircraft you need to depict it as accurately as possilbe. But just to sit on the shelf build it like you want it! It’s your model! It’s supposed to be “fun”! I seem to forget that a lot myself!
Great but then doesnt matter if its an F-6B or a P-51B or an A-36 the flaps and wheel bay doors after the engine shut down would slowly drop?? i want to model A-36 in 1/48 that i just got but i was wondering what would be more accurate, i want to build it as if it had been standing for a long time so thats why i wonder[;)]
thanks for your help fellas!
my best regards
Hector [{(-_-)}]
If it had been standing a long time, then it’s likely flaps and gear doors would have dropped fully, especially if it was a slightly war weary bird. My own inclination would be to do it with everything down, but it’s your model so you’ve got to build it the way that makes you happy with it. One point though. If it has been stood a long time, I would suggest using bulged tyres as well to help the illusion
Good advice Chris. My sentiments exactly.
On most WW ll aircraft, the hydraulic systems contained what were refered to as thermal relief valves - If you shut the aircraft down and don’t bleed the hyd pressure off, the system will maintain that pressure. After setting in the sun, the pressure (usually 1000 psi) will build up due to heat. When the pressure reached aprox 1500 psi, the thermal relief valve opened, passing fluid back to the hyd resevoir until the pressure on the system was back down to 1000 psi and then closed. This prevented cracked or broken hydraulic lines. (A B-25 has about a dozen in its system and can drive you crazy if one of them sticks open - you don’t get any pressure after you start the thing up)
The P-51 didn’t have any thermal relief valves in its system so they installed a manual relief valve which the pilot opened after shut down by pulling a T handle located at the bottom center of the control panel and locking it in the open position. When he started up, he had to push the handle in to close the valve. If you didn’t , you had no hydraulic pressure, The Flight Manual is pretty specific about its operation. Depending on the airplane It would take anywhere from 1/2 hr to 5 or 6 hrs before the gear doors and flaps were all the way down. By the way, the flaps came down together usually but the gear doors usually came down one before the other.
Thanks a lot Quincy, that was very helpful, now i can build my A-36 with the bulged tyres as Chris suggested and with the flaps and gear doors open, hey by the way, how do you know about that? if you read it from a book i would like to know the name of the book, i have been very concerned about the systems in those WW2 birds…
thanks a lot fellas!
my best regards
Hector.
I would really check out a few pictures if building an Allison powered Mustang. Most Allison powered versions Ive ever seen had the gear doors and flaps up even after sitting a while. I also seem to remember reading that the Allisons had a different hydraulic system and that if the gear doors and flaps were dropped they were dropped on purpose.
Ill agree though that the Merlin equipped P-51 hydraulics would definately bleed down and drop the flaps and gear doors.
Here are some sites with Allison engined P-51 pics
This one shows a shot of a maintenance crew working on a P-51 with the gear door dropped but the flaps up… but includes another aircraft with the doors and flaps up.
http://www.ipmsstockholm.org/magazine/1999/11/stuff_eng_p51early.htm
Up http://www.wpafb.af.mil/museum/research/p51-7.jpg
Up on skis too!! http://www.wpafb.af.mil/museum/research/p51-9.jpg
So really to me its your call. For certain they would come down on a Merlin but on an Allison I do have some doubts.
my favorite quote here is “build what you like and like what you build”
I once gave a cousin an F-14 to build and he insisted on hanging it from the celling with the wings swepts and the landing gear down. Drove me nuts to no end but in the end I had to tell myself its his model and he likes it accurate or not. Then for some modelers half the fun is making it as accurate as possible and they do go to extremes… 
Thanks a lot for your kind responses fellas, i just got the Squadron Signal book “Allison powered Mustangs” the thing is that i havent had the time to sit down and analize it so, as soon as i have a chance i will be starting my A-36 and of course as soon as it is done will be my pleasure to show the pics around here [:D]
thanks a lot!
my best regards
Me.[{(-_-)}]
Hector - Sorry I didn’t get back to you but was at the other end of the state at work. Don’t really remember where I first learned about it (some time in the late 50s I believe) but really learned about it in the early 80s when I was working for a gentleman who happened to own a P-51D (amongst some other warbirds). Got to maintain it for about 4 years. First time I cranked it up for a maintenance check - no hydraulic pressure. Ran it for about 3 minutes and shut it down - then spotted the t-handle pulled out at the bottom of the panel. Started it up again and pushed handle in - voila! 1000 psi on the guage. Wouldn’t have been so bad except that there were a half dozen people watching. (Its in the flight manual - but at the time I was operating under the second rule of the aircraft mechanic - when all else fails - read the manual)
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