Range drop tanks and declining returns

[slaterat]

Just thought I would post this info on hurricane 2 range. Notice how the increase from 45 to 90 gallon tanks doesn't get a large increase in range the increased weight and drag seems to use up most of the extra fuel capacity.

Also notice how much fuel is used at higher boost rates. At 9 lbs boost fuel consumption is 100 gal per hr. That's about 16 gallons for 10 minutes of combat!

I suppose the hurricanes effective combat range while carrying the two 45 gal tanks would be a bit over 400 miles?

Slaterat

 

[RCAFson]

Just thought I would post this info on hurricane 2 range. Notice how the increase from 45 to 90 gallon tanks doesn't get a large increase in range the increased weight and drag seems to use up most of the extra fuel capacity.

Also notice how much fuel is used at higher boost rates. At 9 lbs boost fuel consumption is 100 gal per hr. That's about 16 gallons for 10 minutes of combat!

I suppose the hurricanes effective combat range while carrying the two 45 gal tanks would be a bit over 400 miles?

Slaterat

Those ranges are at 20K ft with the allowance for warmup, TO and climb (at normal climb power) subtracted. The TO and climb fuel consumption is higher with the larger DTs and the 20K ft altitude increases fuel consumption at high weight.

EDIT: Also those ranges appear to be with the DTs retained for the entire mission.

This is from Mason's the Secret Years:

An uncontrolled landing Whitley destroyed Z2905 on
8 June 1942 after only a few but busy weeks at A& AEE,
starting with trials of two 44 gal drop tanks and then two
larger (90 gal) tanks. The latter gave a total capacity of
274 gal and all up weight of 9130 lb. Even the smaller
tanks enabled a 5 hr 45 min endurance flight to be flown,
and the larger tanks gave a maximum range of 1,500 miles
provided the tanks were jettisoned when empty. Handling
after take-off (taking a run of 348 yd from a concrete
runway) was unpleasant due to instability, and the pilot
was unable to see the tanks.

 

[RCAFson]

See my edit above.

 

[Admiral Beez]

I often wondered why external tanks weren't considered for the Doolittle Raid. Or any multiple engine bombers for that matter. I suppose gas is weight that would otherwise be bombs.

 

[Shortround6]

I often wondered why external tanks weren't considered for the Doolittle Raid. Or any multiple engine bombers for that matter.

Most of the time bombers were weight limited, not volume limited.
They could find more space for fuel than they could get off the ground without very long airstrips.

Drop tanks did show up on the Mosquito, the B-26 and the Lockheed Ventura. maybe a few others during the war.

 

[Greg Boeser]

Most of the time bombers were weight limited, not volume limited.
They could find more space for fuel than they could get off the ground without very long airstrips.

Drop tanks did show up on the Mosquito, the B-26 and the Lockheed Ventura. maybe a few others during the war.

The B-26 Marauder did not carry drop tanks. It could be fitted with auxiliary tanks in the bomb bay(s).
B-25s maybe?
I know that the PV-1s flying out of the Aleutians were fitted with drop tanks. They learned that flying at higher cruise settings actually improved range.
I have seen pilot manuals that have different settings for max endurance and max range.

 

[Shortround6]

The B-26 Marauder did not carry drop tanks. It could be fitted with auxiliary tanks in the bomb bay(s).
B-25s maybe?
I know that the PV-1s flying out of the Aleutians were fitted with drop tanks. They learned that flying at higher cruise settings actually improved range.
I have seen pilot manuals that have different settings for max endurance and max range.

Thanks for the correction, It may have been A-26s but I can't remember if that was during the war or post war. Later rebuilds got tip tanks and drop tanks.

 

[RCAFson]

I often wondered why external tanks weren't considered for the Doolittle Raid. Or any multiple engine bombers for that matter. I suppose gas is weight that would otherwise be bombs.

The Doolittle B-25s had bomb bay aux tanks installed to increase fuel capacity by ~500usg.

 

[special ed]

If my memory is correct, they also carried additional 5 gallon cans of fuel to add to the aux tanks with the caution to not throw empties out, as they could lead back to carrier.

 

[Simon Thomas]

I found this paper to be a rather amusing way to extend range.

 

[Snautzer01]

found this paper to be a rather amusing way to extend range.

Well take a look at Heinkel He177 Greif then.

 

[GreenKnight121]

I often wondered why external tanks weren't considered for the Doolittle Raid. Or any multiple engine bombers for that matter. I suppose gas is weight that would otherwise be bombs.

The B-25Bs were already at the max take-off weight... and that was after removing some equipment to reduce the airframe weight!

The Doolittle Tokyo Raid

Certain modifications had to be made to the B-25Bs to make them suitable for the mission. Since the raid was going to be made at low level, the retractable ventral turret was removed, saving about 600 pounds of weight. More fuel was added to the plane, bringing the total fuel load to 1141 gallons--646 gallons in the wing tanks, 225 gallons in the bomb bay tank, 160 gallons in a collapsable tank carried in the crawlspace above the bomb bay, 160 gallons in the ventral turret space, and ten 5-gallon cans for refills. The still-secret Norden bombsight was removed, lest it fall into Japanese hands. It was replaced by a makeshift bombsight that proved more satisfactory for low level operations. The bomb load consisted of four 500-pound bombs. As a deterrent against Japanese fighters making stern attacks, a pair of dummy guns in the form of wooden sticks painted black were attached to the extreme rear fuselage, protruding out the back of the transparent tail cap. Takeoff weight was about 31,000 pounds.

North American B-25B Mitchell

Weights: 20,000 pounds empty, 28,460 pounds loaded, 31,000 pounds maximum.

 

[drgondog]

I often wondered why external tanks weren't considered for the Doolittle Raid. Or any multiple engine bombers for that matter. I suppose gas is weight that would otherwise be bombs.

Drag. Parasite drag because of greater form drag and Induced drag for flying at hgher angle of attack to maintain speed with greater gross weight.