Ventral external fuel tank and quantities

[ramtsi]

Hi. After reading the guide I still have a problem understanding the quantities before and after the ventral external fuel tank runs out.

 

The guide says:

1. 3000-3200 L remaining if plane has a ventral external tank.

2500-2700 L if not.

2. If plane had ventral (central external), remaining fuel is 2700-2500 L.

If plane doesn't have ventral tank, remaining fuel is 2700 L.

 

This is regarding the fuel warning lights and the weapons and ordnance lights.

 

So I still don't understand:

 

a. What fuel quantity should I set when fuel is full (internal tanks + ventral external tank)..?

b. What light will turn on when the ventral external tank is empty?

c. What fuel quantity should I set after the external ventral tank is empty?

 

Cheers.

[rossmum]

Fuel quantity is automatically set when rearming/refuelling (it will happen after rearming is complete). Full internal + ventral will set to about 3800L. When the ventral tank is full, the "SUSPENDED TANK/PODVESN. BAK." light will come on (right of the fuel gauge, top light). You'll see it flicker for a minute or so as the last of the tank empties, when it comes on steady, the tank is drained.

 

There is no need to adjust fuel quantity after the ventral tank drains. If you need to get rid of the ventral tank before it's empty, wind the fuel gauge back to about 2800-2900 (to give yourself some safety margin) before you jettison it.

 

When the 450L light comes on, you want to be relatively close to a friendly airfield. The next light below that signals about 250-300L total remaining. Consider it your "you need to land within the next few minutes" warning.

 

The final light ("SERVICE TANK/RASKHOD. BAK.") top right of the main warning panel, indicates the 80L service tank is being drained. If this light comes on it means you have a dire situation on your hands and have anywhere between 5 seconds and 2 minutes of flying time left depending on your power setting and altitude, before the engine is starved of fuel.

[ramtsi]

Thanks Ross. This helps a lot.

 

Ppl give this bird a lot of bad rep. But I find it a lot more intuitive than I thought.

[Frederf]

The real airplane has a slightly complex fuel schedule in that at the moment of external tank exhaustion the internal fuel isn't 100.000000% full. There are also various quantities of unusable fuel and some variability, safety margin built into the gauge settings.

 

The DCS module is not that complex. It uses every single drop in the external tank before the internal tank is touched. While the concept of unusable fuel exists in the DCS in that the engine quits at a fuel level >0 but the fuel gauge is auto-set according to total fuel exactly and not usable fuel. So if you don't adjust the default you will have the engine quit sooner than 0 on the gauge. If you knock off ~80-100L off the automatic needle setting you bridge the gap between usable and total fuel so you won't starve with some fuel left on the clock.

 

There's no way to exactly square the real flight manual says with the DCS module but it's pretty close and completely workable. Basically when the signal lights come on solid (not flicker) at the total fuel (not usable) according to the manual except for external tank lights which come on exactly when they are empty.

[rossmum]

Yep. DCS simplifies it (like the amount being auto-set by the ground crew) but for most purposes it's close enough, and fully trusting the fuel gauge in pretty much anything in the real world is a bit dicey at the best of times.

[Buzzles]

Unless I'm very much mistaken, the fuel gauge in the Mig-21 isn't a normal fuel gauge.

 

It's not checking levels in the tanks.

 

 

It's a "starting value - fuel flow" gauge. Hence why you set it with a knob.