using the belly tank

[peachmonkey]

hi, guys,

Question:  how do I use the belly tank? 

I feel a bit dumb as I'm not sure if I'm doing something wrong, although there's very little to do. I have no problems using the wing tanks, however when I equip the belly tank (metal one) the engine chokes and stops running as soon as I switch the fuel selector to External Tank.

1) in Rearm/refuel menu I add a Belly tank

2) I select 100% fuel

3) once fueling/arming is completed I simply switch the Fuel Selector to "External", the External Fuel Tank Selector is already set to "Belly". And the engine starts coughing/dying.

If I use wing tanks, then everything works as it should, I select "External" and then either Left or Right on the external selector.

Am I missing something?

Edited September 13, 2023 by peachmonkey

[saburo_cz]

Did you use that belly tank on ground at lower engine power?

In that case, you did have insufficient air pressure to get fuel from external tank.
To get enought air pressure you need some RPM above idle.

Edited September 14, 2023 by saburo_cz

[peachmonkey]

2 hours ago, saburo_cz said:

Did you use that belly tank on ground with lower engine power?

In that case, you did have insufficient air pressure to get fuel from external tank.
To get enought air pressure you need some RPM above idle.

Thank you for the hint! Yup, I did the basic tests while running the engine at idle on the ground. I'll try it out with the higher rpm to see if there's a difference.

If you don't mind, can you share the source of the info about the higher rpm requirement? It's strange that the idle works for the wing tanks but not the belly...

[saburo_cz]

Low RPM did not work for all external tanks, belly and wings.

Fuel from external tanks is forced by pressured air and source for that air is the vacuum pump, its exhaust. The vacuum pump just does not produce enough air pressure at low RPM.

 

I do not know if it is somewhere written exactly in the P-47 documendation, but i think it was in one manual for the P-51 which use the same system.
We had here the same debate about the P-51 external tanks years ago.

[DD_Fenrir]

For what it's worth, this fuel pressure issue from jettison tanks is a common feature across aircraft of all nations from this era and is why it is common for SOPs to say to switch to drop tanks only once airbourne and to operate from internal tankage during all taxi/takeoff/landing regimes.

[peachmonkey]

@saburo_cz and @DD_Fenrir  - thank you for solving my issue, indeed the belly tank works when the RPM's are sufficiently high enough!

cheers.