Fuel pressure when using external fuel tanks

[AJaromir]

Good day. 

Flight conditions:

- Just when I enter the mission editor and create new mission

Terrain: Caucasus

Airfield: Kobuleti

Take of from runway

Payload:

- 100% gun

- 68% fuel

- both droptanks

-----------------------------------------------

When I did fly using drop tanks, I've noticed the instant drop of fuel pressure bellow redline.

It was like:

In altitude 13400 ft ASL the fuel pressure is on top of green strip - around 16 lbs sq. in

In altitude 13600 ft ASL the fuel pressure is far bellow the redline - around 9 lbs sq. in

The change of fuel pressure is instant.

Is this behaviour correct?

If yes, should I fly in altitude where the fuel pressure is in limits?

 

By the way in DCS:P-51D manual is written that I should fly in normal altitude. But nowhere in manual is written what is normal altitude for P-51D.

Edited October 17, 2022 by AJaromir

[AJaromir]

Here is the video which I've made as reference.  It is clearly visible how the pressure depends on altitude and instantly drops or raises.

 

[NineLine]

Can you please supply the track as well? Thanks.

[AJaromir]

On 10/31/2022 at 9:04 PM, NineLine said:

Can you please supply the track as well? Thanks.

 

Fuel pressure.trk

[Magic Zach]

The external tanks didn't have their own pump per tank, but relied on the exhaust end of the vacuum pressure, as well as the engine driven fuel pump.  The engine driven pump has a relief valve that ensured that the pressure output was always stable, even between itself and the booster pumps (in the main three tanks, not in our combat tanks).  The engine driven pump could supply fuel properly from external tanks, soley on its own without aid of the vacuum pump, only to 10,000ft.
However unless the vacuum pump were to fail, the pressure from the external tanks should be stable throughout all operating altitudes as well.  What I can't find though, is a reference to what the observable pressure was when relying on the engine pump and vacuum system alone.
This doesn't give a yes or no answer to your post, but it should provide some better context.