Operating (external) fuel tanks

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Tobus
Posts: 64
Joined: Thu Aug 23, 2012 12:15 am
Operating (external) fuel tanks

Post by Tobus » Sat Jun 15, 2019 12:47 pm

Hi,

question: how do you operate the fuel tanks, internal and external?

It seems left and right internal tanks are only drawn from using the fuel pumps linked to them.
As such, only using pump#1 lets the engine feed of only the left tank. Correct?

Also, when external tanks are added, how does one feed the internal tanks with the externals, as there are both an emergency cover and external cover switch?

Tobus
Posts: 64
Joined: Thu Aug 23, 2012 12:15 am
Re: Operating (external) fuel tanks

Post by Tobus » Thu Jun 27, 2019 1:17 pm

Ok, so set up test flight.
Internal tanks, both 75%
External 1: 50%
External 2: 25%

Upon powering the aircraft, fuel gauges show internal tanks 1 and 2 at 75%

Upon unguarding and activating the Ext fuel enable switch, fuel gauges show external tanks showing 50 and 25%.
So apparently the ext fuel enable switch lets I see external tank capacity instead of internal tank capacity.

Turning fuel pumps #1 and #2 ON after engine running, time compression at 4x.
External tanks lowering, internal getting higher, so externals are pumped into internals.

Turning fuel pumps #1 and #2 OFF after engine running, time compression at 4x.
External tanks staying level, internals getting lower, so pumps off means using internal tanks instead of externals.

Turning fuel pump #1 ON, #2 OFF after engine running, time compression at 4x.
Left external tank lowering, right external level, left internal tank rising, right internal level.

Turning fuel pump #1 OFF, #2 ON after engine running, time compression at 4x.
Left external tank level, right external tank lowering, left internal tank level, right internal tank rising.

I have no clue what the red emergency external fuel cover and switch do.

So my conclusions are:
- disabling (default setting) the yellow striped external fuel enable switch shows the internal fuel tank levels on the fuel gauges
- enabling the yellow striped external fuel enable switch shows the external fuel tank levels on the fuel gauges
- enabling fuel pump #1 empties external tank #1 into internal tank #1
- enabling fuel pump #2 empties external tank #2 into internal tank #2
- In any case the engine feeds on both internal tanks
- no use has been found by me on the red striped emergency external fuel switch

It seems the workings of the externals vs internals has been explained. Although I do find fuel gauge readings from an external tank strange, I can imagine it having been implemented for simulation purposes.

Anyone have an idea what the emergency external fuel switch is for?


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