Spitfire's fuel tanks.

[MachFly]

The current order of the way Spitfires drain fuel from their tanks is: Drop, Wings, Bottom, Top. In reality Spitfire pilots would drain the top fuel tank first and then the bottom. The way the Spitfire's fuel system works is the fuel taken from the bottom tank, as you start having extra room in the bottom tank the fuel from the top tank would poor down into the bottom. Bottom fuel tank is self sealing and armored, top is not, so you want to empty your most vulnerable fuel tanks first.
I'm not exactly sure why but I've read that it's also better for weight distribution to drain the top fuel tank first. Also I don't know this for a fact but I don't believe the Spitfire isn't even capable of taking fuel directly from the top tank.
I recommend we change the automated order of draining fuel tanks to: Drop, Wings, Top, Bottom. 

[GNucks]

The way the Spitfire's fuel system works is the fuel taken from the bottom tank, as you start having extra room in the bottom tank the fuel from the top tank would poor down into the bottom.

Why does the order of the fuel tanks need to be changed if all draining from the bottom does is drain the top?

[PFactorDave]

Fly a 109 instead, or one of the Ki's...  Problem solved...   

[Krusty]

Well if it was really 1 tank combined (no pumps, just a straight up gravity drain) shouldn't it only be showing as a single tank? A hole in either one would cause a drain, would it not? You get a hole in the bottom tank and you'd lose the top as well, right?

So why not have HTC model it as a single selectable tank (but keep where HTC has modeled the different bullet proof protection for the different parts of it)?

[MachFly]

Well if it was really 1 tank combined (no pumps, just a straight up gravity drain) shouldn't it only be showing as a single tank? A hole in either one would cause a drain, would it not? You get a hole in the bottom tank and you'd lose the top as well, right?

So why not have HTC model it as a single selectable tank (but keep where HTC has modeled the different bullet proof protection for the different parts of it)?

Technically that works too. Officially they were considered to be different tanks though, and I figured it would be a lot easier to change the order than redesign the whole fuel system.

[MachFly]

Why does the order of the fuel tanks need to be changed if all draining from the bottom does is drain the top?

In AH you normally empty out the bottom tank first and when that's empty you start using the top. In reality you don't run out of fuel in the bottom tank unless your out of fuel in the top tank.  

Fly a 109 instead, or one of the Ki's...  Problem solved...   

lol

[Krusty]

Well, that begs the question: Could you even select the top tank in a Spitfire? Or did you select one setting and it drained automatically for you?

[MachFly]

This should clarify all the specifications.


Took this from Pilot's Notes for SpitIIAII and IIB





Took this from Pilot's notes for Spitfire VA, VB, VC, IB, IIC, III





Took this from Pilot's notes for Spitfire IX, XI, & XVI





Took this from Pilot Notes for Spitfire XII





Took this from Pilot's notes for Spitfire XIV and XIX

[RTHolmes]

(edited - see below)


strange that none of the diagrams show the pressurization line for the drop tank

[MachFly]

if you look at the tank capacities the drain order is actually correct, its just the AH labels that are swapped. (ie. Main should be Top and vice versa)

What do you mean by "main"? A few years ago the top fuel tank on the Spit14 was labeled as main but now they made it like all other Spits, just top and bottom.
In AH's Spitfires the top fuel tanks is the largest, these diagrams show the top fuel tank to be the largest as well (excluding the Spit14).

BTW looking at the Spit14 fuel diagram it looks like the AH Spit14 has a screwed up fuel system. Apparently the real 14's bottom fuel tank was the largest (not the top as in AH) and we don't even have an aft tank.

[RTHolmes]

(edited - see below)

[MachFly]

oops I mean the Top and Bottom labels are swapped

You mean for the 14? Because I think the Merlin AH Spitfires have a properly set up fuel tanks (excluding the order in which they are used).

[MachFly]

strange that none of the diagrams show the pressurization line for the drop tank

I think that's because these diagrams are meant for pilots, not mechanics. Mechanics would have a much more specific diagram.

[RTHolmes]

(edited - see below)

[MachFly]

for our merlin spits the drain order is correct, ie. 48gal (Upper Tank) then 37gal (Lower Tank). Assuming the Pilot's Notes are correct, its just the AH labels which are wrong. In AH the 48gal is incorrectly called Bottom and the 37gal Top.


Havent checked the AH XIV but it should drain 36gal (Upper Main) then 49gal (Lower Main).

I'm pretty sure in all AH Spitfires the top fuel tank is the largest, and they are all programmed to first take fuel from the bottom tank then top. I don't know of a way to find out the exact amount of fuel that each fuel tank holds on AH spitfires, however looking at the time it takes to burn the fuel from each tank I've noticed that the top tank is the biggest.

Actually I just realized of a way to test the amount of fuel each fuel tank holds on AH spitfires. While being leveled and at a constant power setting we can burn off each tank, e6b will give you the fuel burn rate and we can time how long it takes to burn off the whole tank. This will allow us to calculate the amount of fuel in each tank.
Unfortunately I do not have time to do the test right now.