P-51B Fuel Loadouts

[EagleDNY]

Was checking fuel loadouts on the P-51B and noticed something odd - the 25% and 50% fuel loadouts on it are bit "short".

Per E6B (and the fuel gauge):
25% is 62
50% is 123
75% is 202
100% is 269

269/4 = 67.25 so I would have expected the 25% loadout to be 67 and the 50% loadout to be 134 or 135. 

Is this a bug, or some strangeness in the 51Bs tankage arrangements??

[Devonai]

The POL guys are playing a joke on the pilots.  It's hilarious to ditch five miles from the airfield because you thought you had more flight time.

Right?

[MK-84]

No he's saying that 25% fuel should be 1/4 that of 100% fuel, but per E6B weights it is not.

[Butcher]

No he's saying that 25% fuel should be 1/4 that of 100% fuel, but per E6B weights it is not.

Pretty good find, its possible it simply hasn't been noticed till now.

[EagleDNY]

Only reason I found it was that we had 51Bs in FSO and I wanted to know how much flight time we had. 

[SmokinLoon]

Keep in mind that burn rates change with altitude.  This is easily seen in the F4U.  In one of the models you lift (in the MA) with about 35 mins of fuel when %100 is selected.  After 10 minutes of climbing, you still have over 30 mins of fuel.  Check it out.  There are numerous aircraft like this.

Oh, and forget the fuel gauges, watch your E6B.  It doesnt matter how much fuel you have, all that matters is how much air time you have and how far your range is *under the current burn rate and speed*.   

So don't ever lift with X amount of fuel and take the E6B's estimate as %100 accurate.   

[B-17]

35 minutes with 100% fuel???

[MK-84]

Keep in mind that burn rates change with altitude.  This is easily seen in the F4U.  In one of the models you lift (in the MA) with about 35 mins of fuel when %100 is selected.  After 10 minutes of climbing, you still have over 30 mins of fuel.  Check it out.  There are numerous aircraft like this.

Oh, and forget the fuel gauges, watch your E6B.  It doesnt matter how much fuel you have, all that matters is how much air time you have and how far your range is *under the current burn rate and speed*.   

So don't ever lift with X amount of fuel and take the E6B's estimate as %100 accurate.   

Great, but that isnt what the post is about.

If you select 25% of fuel in a P51b  by weight in E6B should 1/4 what 100% selected is.

and it isnt.

[SmokinLoon]

35 minutes with 100% fuel???

Oops... sorry, %100 give 29 min.  Same ratio applies when grabbing alt though.  ! minute of flight time surpassed doesnt always mean 1 minute of flight time LESS, the burn rate changes as the alt gets higher.

The weight differences between %100, 75, 50, and 25 are: 403 lbs, 472 lbs, and 364 lbs (actual P51B weights: %100 = 9843 lbs; %75 = 9440; %50 = 8968; and %25 = 8604).  The biggest eights "savings" or jump rather is between %75 and %50.

Has anyone checked the weight differences in the other aircraft? 

[B-17]

So wait... When at full throttle on the runway, your E6B says you have 35 minutes left when you have chosen 100% fuel from the hangar?

[SmokinLoon]

So wait... When at full throttle on the runway, your E6B says you have 35 minutes left when you have chosen 100% fuel from the hangar?

*points to my previous post*