Fuel & Exhaust

[Willy]

Cool! Could be some really interesting stuff going on in here.

Just a couple of tips/pet peeves........

1) don't use the Imperial gallons for older British aircrafts specs, convert 'em to US ones that FS goes by. My favorite payware Spitfire came using with the old Imperial gallons in the fuel capacities. Really hurts the range when you do that. Yes, I converted it and added the missing internal wing tanks while I was at it!

2) Yes, piston aircraft do leave contrails at low enough temps and FS9 will do them by a simple line in the aircraft.cfg file. (a lot of designers don't put that one in there)
Yall have fun!

[Henry]

Cool! Could be some really interesting stuff going on in here.

Just a couple of tips/pet peeves........

1) don't use the Imperial gallons for older British aircrafts specs, convert 'em to US ones that FS goes by. My favorite payware Spitfire came using with the old Imperial gallons in the fuel capacities. Really hurts the range when you do that. Yes, I converted it and added the missing internal wing tanks while I was at it!

2) Yes, piston aircraft do leave contrails at low enough temps and FS9 will do them by a simple line in the aircraft.cfg file. (a lot of designers don't put that one in there)
Yall have fun!
a good point what does the sim use?
imperial or us
im guessing US
so should we convert when making a Eorpean plane?
H

[paulb]

Hi Willy

Well, going VERY slightly off topic........................

I think that FS9 takes a whole lot of notice of fuel load. I wonder how many members -

Check their fuel load before take off?

Ensure that their fuel load is low enough for a landing?

OK - please start a debate! :)

Cheers Paul

[Henry]

but is fuel load US or imperial?
H

[flightsimmer]

but is fuel load US or imperial?
H

It is definitely U.S. gallons in FS.

Bruce

[Willy]

From what I've been told by folks (think I remember who, but not sure so I won't mention names) who should know, the fuel load as used by FS is in US gallons. With the Imperial gallons being roughly 1/5th larger, it makes quite a bit of difference.

The Spitfire XIX that I'm flying.....

Original in Imperial gallons (with incorrect wing tanks):
Center1 = 0, 0, 0, 48, 0
Center2 = 0, 0, 0, 36, 0
LeftMain = 0, -6, -1, 12.75, 0 //Mains should be 66gl Imp per wing
RightMain = 0, 6, -1, 12.75, 0 //12.75 is for smaller aux internal wing tanks

Total: 109.5gl Imp or 131.5gl US

Now in US gallons (with wing tanks corrected):
Center1 = -0.4, 0, 1.148, 59, 0
Center2 = -0.4, 0, -1.05, 43, 0
LeftMain = 0, -2.2, -1.67, 79, 0
LeftAux = 0, -2.2, -1.67, 15, 0
RightMain = 0, 2.2, -1.67, 79, 0
RightAux = 0, -2.2, -1.67, 15, 0

Total: 290gl US

(Actually, I'm glad I was rechecking my figures on this. I'd made a math error originally and was quite a bit over over on the capacities in the wings myself. Fixed now here and in the aircraft.cfg :redf: )

I kept finding sources that claimed the PR Spits had much larger fuel capacities than the standard ones and with some help from some of the SOH race team members we chased down "correct" figures. Not saying they are 100%, but as close as we could come up with, including contacting the RAF BOBMF who operate a Mk XIX.

As for landing light or heavy, I wouldn't do this in real life except in an emergency, but I do practice near full fuel load landings in FS. My thought is that if I can land it with a full load, then a light load should'nt be a problem ;)

[fliger747]

Some of the external tanked birds can be a handfull to land when full of gas! I once landed (real) a 747-400 with 117 metric tons of fuel on board, the roll inertia was significant!

Some planes such as the P-51 with an aft fuselage tank were notoriously bad handling till that tank burned off, due to the aft CG. I am not sure FS changes the pitch inertial moment with the weight and CG change? Any experience with this in FS. It doesn't seem to be as pronounced an effect as I have seen in rela aircraft. Working on this one!

[Willy]

One of the more recent P-51 releases from what I understand models that quite well.

Also in my playing around with Spitfire fuel tanks, some of the "high back" later Mks also had a tank behind the pilot and when I add that to the aircraft.cfg, they could get a bit "squirrely" as well.

Oh well, the trials and tribulations of a tweaker........ :D

[fliger747]

It can get bad enough that you can have negative pitch stability, good practice for flying helicopters I guess!

[paulb]

Yes, as already said, the fuel load in FS is definitely in US gallons. I discovered this when doing some flight testing a while back. I loaded imperial gallons but found that my weight was different (higher) to the real aircraft weight data that I had. As soon as I converted form imperial to US gallons then the weight was accurate.

The handling in FS seems to depend on the number of fuel selectors, with only one it seems (going from memory here) to take fuel in equal proportions from the different tanks.

BTW, I find a huge performance difference depending upon fuel load. :)

Cheers Paul

[von Bek]

Just a tip for understanding the conversion.

Fluid ounces are the same in both systems.

A US Gallon is 8 pints of 16 floz. each (thus it weighs 8lbs when composed of water)
An Imperial Gallon is 8 pints of 20 floz. each (thus it weighs 10lbs when composed of water)

US Gallon = 128floz.
Imp Gallon = 160floz.

Conversion factor (Imp. to US) is 160/128 = 5/4

[Henry]

thanks VB
i was going to ask:)
H

[Willy]

I just use a little conversion calculator program that will convert most anything. At just over 530kb zipped it's a bit much to attach to a post, but if anyone's interested, I'll upload it to the downloads section.


Hmm, the British pint is 20oz? No wonder I was getting so smashed in the pubs in Dunoon & Glasgow. I was drinking Tennants like it was a 16oz pint.... :costumes:

:ernae:
Willy

[paulb]

Hi Willy

Yes, we have some great beers over here :) .

One local pint is called S.A. (ie strong ale) but we know it as 'Skull Attack' :D .

Cheers Paul

[fliger747]

Tomorow, on to the land "Down Under", who's folks well leaned the value of a good brew from their forefathers!

More on topic; then there is the continual conversion between mph, Knots and kph. Being a modern US aviation based simulation, FS likes knots, which is what most planes fly on these days, however most of the vintage planes of interest here in FS9 and CFS were originally created in mph and have specs listed as such. They sure sound faster in mph, darn hard to break that 400 barrier in knots though! Is there a way to get data to show up in FS in mph instead of knots? Sometimes in our Raushaus Racer's discussions the units in question have been left off, to ocassional confusion.

Most of us have become multilingual with these things, but as Willy originally pointed out, lack of specification of the exact units, even in references has led us astray a time or two.

Now then a 'fifth' of Scotch is 4/5 ths of a US Gallon, or five to a gallon. Are they called something else closer to the land of origin? An external tank could be quoted as having a capacity in fifth's...... I understand that was an ocassional use.