Fuel Quantities

[Mike Busutil]

Can I get a confirmation on the fuel quantities please.

 

I am looking at some contradicting information between the flight manual, threads and notes.

 

Full fuel, no drop tanks = 2,850 L

Full fuel with 490L centerline tank = 3,340 L.

Full fuel with 490L centerline tank & 2x 490L wing tanks = 4,320L

Fuel fuel with 800L centerline tank = 3,650 L & 2x 490L wing tanks = 4,630L

 

Correct?

 

With the centerline drop tank and both wing drop tanks installed, which will drain first? The centerline drop tank or the wing tanks?

 

Thanks.

[Art-J]

Your math skills are correct allright ;).

 

Looking for actual fuel quantities is more complicated, though. For example the real manual suggests using 2750 internal capacity figure ("usable" fuel without amounts trapped in the system) for range and endurance calculations, while the fuel warning lights table from the same documents says the "external tank(s) empty" will blink when internal capacity goes to anywhere between "2500-2700 L". Pick the one You wish :D. To make things more interesting, other, Russian, systems maintenance manual states the drop tanks capacity was 480 and 780 actually.

 

I stopped bothering long time ago - as long as cockpit indicators in "our" MiG work OK (and they do it seems), You'll be fine. Just remember about fuel consumption being heavily reworked in one of recent patches.

 

The only certain thing is draining order: wing drop tanks -> centerline drop tank -> 1st group of internal tanks -> 3rd group of internal tanks.

[foxtheancient]

I found hard to find official data about fuel management system. I made my picture from pieces here and there scattered in forum and manual. Please can someone confirm to me that I understand it correctly? My understanding follows...

 

Mig 21 has no fuel tank capacity meter. Instead of this fuel quantity is set on indicator manually before start depending on fuel load. Current fuel level is calculated from current level and immediate fuel consumption. Meaning that fuel level indicator is more guess than real status.

 

As all external fuel tanks are dry (or dropped) one need to switch off "fuel tanks 1st group" to save pumps from working with no fuel. Meaning one should not turn 1st group on with no external fuel at the first place. In case of dropping tank before they are empty one need to calculate remaining fuel and modify fuel indicator accordingly (to "burn" fuel that has been dropped with tanks).

 

Fuel flow is managed automatically. First is 1st group burning fuel from external tanks. First are wing tanks if present, then fuselage tank. Inner fuel tanks goes when external tanks are empty or not present.

 

Internal fuel storage is ~2700 L (maybe a bit more but because of guessing instead of measuring it is better to set lower value to be safe). Wing tanks are dropping by button on center dashboard under big yellow cover. Fuselage tank is dropped by button on stick. There are lights at info panel showing empty external wing tanks, empty external fuselage tank and need to turn of 1st and 3rd fuel tank group.

[Frederf]

The fuel total indications are based on the "manual set and automatic subtraction" principal as you say. It gets a little confused because when you refuel a magic invisible hand reaches in and fixes your gauge for you.

 

There are sensors in the other tanks that drive the warning lights so those can be trusted to update your total needle.