P-51D drop tank plumbing

[von hahn]

Hi. I know that both the 108gal and 75gal drop tanks used on P-51Ds had a few pipes attached between the drop tank and the wing, but my question is did the pipes detach from the wing with the drop tank when the drop tank was jettisoned or did these pipes, or part thereof, remain attached to the wing after the drop tank fell away?

I've seen original photos that seem to suggest that part of the plumbing stayed behind (a photo of the 356th FG P-51D "Jackie" for example).

Thanks in advance!

 

[Crimea_River]

As far as I recall, there were external break-away fittings between the wing and tank which meant that part of the fuel and pressure lines stayed sticking out of the wing after the tank separated. I could dig some more but am limited for time right now.

 

[MIflyer]

They used glass tubes for breakaway. But the tanks also required tubing to provide air ressure to the tanks, using the vaccum pump exhaust. So it required at least two tubes. Some photos appear to show three. From the book "Mustang at War" by Roger A. Freeman, 1974.

 

[Crimea_River]

The below picture, taken from Britmodeller, shows the remaining lines after jettison. Just ahead of the rack, you can see the fuel line and, inboard of the rack and between the two stabilizers, you can see the pressure line. This line was sometimes located in front of the rack in line with, and just aft of, the fuel line

 

[von hahn]

Thank you all so much for the info, it is greatly appreciated!

 

[Airframes]

I have some detail shots, and I think a drawing, of the "plumbing" arrangement, But I'm having problems up-loading pics at the moment ( not just to the forum), when my PC "freezes" and I have to re-start to get anything to work.
EDIT:- Managed to load one pic, of a restored (static) P-51D at Duxford, just after completion, and before being moved to the American Museum for display.
This shows the 75 gal tank, with the rubber hoses and, at the tank-end of these, the glass "break away" tubes ( one of which appears to be copper here, probably "good enough" for a static, ceiling-hanging display, as it now is ).
The 108 gal steel, and "paper" tanks, had a similar arrangement, although one of the pipes ( from memory, the pressure line) ran towards the rear of the tank, on the portside on each tank, roughly just aft, and slightly outboard of the rear of the pylon.

 

[Crimea_River]

That pic shows the alternate location of the pressure line I talked about. It seems that both styles of tanks had several different entry points for both fuel and pressure. Pics all linked from Britmodeller.

 

[Airframes]

Yep, I believe it depended on the source of the tank. From memory, fuel was the forward pipe, and pressure the aft pipe - I'd need to find the drawings to verify this.

 

[N4521U]

This may help.

 

[von hahn]

Truly some exceptionally helpful info you guys have provided. Thank you for the time and effort you put into helping me answer this question.

 

[Crimea_River]

That's what the forum is for!

 

[MiTasol]

This may help more. Note no mention of glass tubes. There is a mention of breakaway fittings but I would expect those to be a metal tube inserted into a socket with O rings as glass tubes would be very fragile and I would expect warnings in the manual instructing the ground staff to make sure the glass tubes are intact.

 

[MiTasol]

To answer your original question, yes the plumbing all detached with the tank, leaving just the bomb rack and sway braces as drag producers.

If you are an aircorpslibrary.com member you can go to drawing 109-48181 which is one of the two breakaway fittings installed in each wing and you can see where it is installed on drawing 106-14037 sheet 5. It has two O rings to seal where the pipe slips in. The other, similar, fitting is on the leading edge skin.

No glass tubes used anywhere (another one of those myths that keep rearing their ugly heads).

Since the recent site changes you may be able to view the drawing without being a member.

The fittings show in my Parts Catalog but have no part numbers - they are at the wing skin end of pipes 55 & 56

 

[von hahn]

Fascinating and very much appreciated info. Thank you everybody for taking the time to assist me.

 

[Crimea_River]

....No glass tubes used anywhere (another one of those myths that keep rearing their ugly heads)....

Just to be clear. glass break away fittings are not a "myth". While it may be true that there is no mention of them in the P-51 manual, the DH Mosquito B.35 manual makes clear mention of them:

The accompanying detail in figure 6 points to item 1 being the glass tubes for both the fuel and pressure lines.

 

[MiTasol]

Most interesting. The P-51, A6M and Ki43 used self seal couplings so I would have expected the same of other nations. So now I guess the next interesting question is what did the German and Italian aircraft use?

 

[drgondog]

To answer your original question, yes the plumbing all detached with the tank, leaving just the bomb rack and sway braces as drag producers.

If you are an aircorpslibrary.com member you can go to drawing 109-48181 which is one of the two breakaway fittings installed in each wing and you can see where it is installed on drawing 106-14037 sheet 5. It has two O rings to seal where the pipe slips in. The other, similar, fitting is on the leading edge skin.

No glass tubes used anywhere (another one of those myths that keep rearing their ugly heads).

Since the recent site changes you may be able to view the drawing without being a member.

The fittings show in my Parts Catalog but have no part numbers - they are at the wing skin end of pipes 55 & 56
View attachment 611537

FWIIW my father, leading a Sept 12 355th mission to Berlin, had his one and only abort when the glass coupling broke over the Netherlands.

 

[MiTasol]

Very interesting. What sort of aircraft? Maybe early aircraft had glass couplings and later ones the quick disconnect.

 

[drgondog]

Very interesting. What sort of aircraft? Maybe early aircraft had glass couplings and later ones the quick disconnect.

P-51D-10. The 'glass elbow' was common to P-51B/C also.

 

[MiTasol]

Interesting.

Before the P-51 was designed the British and Japanese had self seal couplings on their drop tanks so I would have thought that the P-51 would have had them from day one.

Spitfire

Ki-43

I do not have any photos or diagrams of the wing coupling but the most interesting feature of the Ki-43 drop tank is that it leaves a clean aircraft once it drops free because all the sway braces are on the tank - not hanging out in the breeze under the wing like aerodynamic a**eholes like on the US aircraft of the period. Also the vent is integral with the front attachment whereas on the P-39 and P-40 the vent line was another drag producer.

I cannot find my A6M drop tank photos but again it had a self seal fitting on the mounting tube that went up inside the belly of the aircraft and again left a clean aircraft when jettisoned,