P-39Q Fuselage Aperture

[Tbolt]

Does anyone know what the reason is for the aperture at the back and just below the air intake on the left hand side of P-39Q? Earlier P-39 versions seem to have a squarer access panel here and if the drawings in the Mushroom Model book on the P-39 are correct the change to this aperture came in on the P-39M.

 

 

 

 

 

http://xn--80aafy5bs.xn--p1ai/wp-content/uploads/2017/09/1.Istrebitel-P-39Q-1..jpg

 

 

The only reference I've found to it so far is on this Bell drawing of the P-39Q, where is shows it with a cover fitted so I'm guess it's some sort of vent but I don't know what for. The coolant tank sits just below it. I haven't found anything refference it in the EMI or Pilot's manual yet. Does anyone have a close up picture of it or know what it's for?

 

 

 

[Tbolt]

I found this photo where it's just open into the structure, but is that just because this aircraft isn't complete?

 

[Ray_W]

Seems they originally named the access door for access to the coolant system expansion tank. Prestone being the anti-freeze brand.  Whether it was removed during winter operations (Russian experience? Drain and refill?) or for whatever other reason and then never replaced I do not know. 

 

 

You can see the grey coloured white banded expansion tank in the right of this image.

 

 

I thought the access door may of also allowed access to the oil tank dipstick thereby simplifying checks without the need to remove the topside panel. Dipstick location shown forward (assuming the draughtsman represented it correctly).

 

 

But then, when you see how much room was available,

 

 

This may not be practical. Here is the top of the oil tank with a bulkhead immediately forward and before the expansion tank.

 

 

And here is the expansion tank. 

 

 

And you are correct. Seems some changes going on regarding this access and possibly a system change. I've seen a very poor copy of a later layout with a different system. Apologies not a definitive answer. Hopefully helps in some small way.

 

Ray

 

[Tbolt]

19 minutes ago, Ray_W said:

Seems they originally named the access door for access to the coolant system expansion tank. Prestone being the anti-freeze brand.  Whether it was removed during winter operations (Russian experience? Drain and refill?) or for whatever other reason and then never replaced I do not know. 

 

 

You can see the grey coloured white banded expansion tank in the right of this image.

 

 

I thought the access door may of also allowed access to the oil tank dipstick thereby simplifying checks without the need to remove the topside panel. Dipstick location shown forward (assuming the draughtsman represented it correctly).

 

 

But then, when you see how much room was available,

 

 

This may not be practical. Here is the top of the oil tank with a bulkhead immediately forward and before the expansion tank.

 

 

And here is the expansion tank. 

 

 

And you are correct. Seems some changes going on regarding this access. Apologies not a definitive answer. Hopefully helps in some small way.

 

Ray

 

 

Thanks for that. That first drawing, while the earlier squarer access panel does confirm that it was access for the coolant. Since Bell designed a blank for the aperture I don't think there was a panel after the M and photos of US, French and VVS aircraft all show the same hole.

 

I do have a set of P-39 drawings but the problem is finding the one you want out of the 11,000+ drawings! I'm just not sure what to put in there when I cut the panel out.

[Ray_W]

2 minutes ago, Tbolt said:

11,000+ drawings!

 

This made me laugh 🤣 I think this is a good problem to have,

[Tbolt]

14 minutes ago, Ray_W said:

 

This made me laugh 🤣 I think this is a good problem to have,

 

Sort of, unless you spend hours and hours looking for something only to realise that drawing must be missing 🤪

[Wojtek Bulhak]

It seems that aperture is present i many P-39Qs. I did it in my quickbilt Airacobra:

 

 

Whole building process in described in my post on armahobbynews: link.