Extra Range in a B-25H or J

[earl1937]

  Ok, here is a good question to research: How was the B-25's in the South West Pacific area of operation, able to extend their range by up to 40 minutes?

[DaveBB]

A single notch of flaps would allow the aircraft to change its AoA so that the remaining 40 gallons of fuel could be collected by the fuel pickup.

[colmbo]

A single notch of flaps would allow the aircraft to change its AoA so that the remaining 40 gallons of fuel could be collected by the fuel pickup.

I've read about that.

Yeesh!  I wouldn't want to be cutting it so close that technique was needed.

I've unported the tank on a Cessna hauling jumpers when fuel is very low and steeply spiraling down.

[Arlo]

How many miles were gained from 40 minutes of additional flight time with a notch of flaps and increased AOA?

[Ack-Ack]

In the books "WWII Diaries" and "A Young Man In The Wild Blue Yonder", author and former B-25H pilot David K. Hayward mentioned that the B-25 flew at a slight nose up angle and would cause the fuel to pool at the end of the fuel tank.  A notch of flaps would change the angle and allow the fuel that had pooled at the end of the fuel tank to be used.

[Serenity]

How many miles were gained from 40 minutes of additional flight time with a notch of flaps and increased AOA?

I would guess something verging on 100 miles at least.

[DaveBB]

A much bigger problem that B-25s faced was getting hit in an engine and losing all the oil before the prop could be feathered.  If all the oil was lost, the engine would windmill and the aircraft could not maintain altitude even with full power on the opposite engine. 

Source: Warpath across the Pacific.

[earl1937]

I would guess something verging on 100 miles at least.

Ok, we have 40 gallons left of fuel, that is 20 gal for each engine! The 25's engine burned fuel at the rate of about 40 gallon per hour. That would give you roughly an additional "run" time for the engine of 30 minutes. The 25's maximum speed with 10 degrees of flaps is 180 knots IAS. Based on that, you would gain about 90 miles, with no head wind. With headwind, of course, you have less time you can stay in the air! with a tailwind of course, you might extent your air time a few minutes.

[Serenity]

Ok, we have 40 gallons left of fuel, that is 20 gal for each engine! The 25's engine burned fuel at the rate of about 40 gallon per hour. That would give you roughly an additional "run" time for the engine of 30 minutes. The 25's maximum speed with 10 degrees of flaps is 180 knots IAS. Based on that, you would gain about 90 miles, with no head wind. With headwind, of course, you have less time you can stay in the air! with a tailwind of course, you might extent your air time a few minutes.

Well, I wasn't far off for a WAG!

[colmbo]

A much bigger problem that B-25s faced was getting hit in an engine and losing all the oil before the prop could be feathered.  If all the oil was lost, the engine would windmill and the aircraft could not maintain altitude even with full power on the opposite engine. 

Source: Warpath across the Pacific.

Not just a B-25 problem.  I don't know about the B-25 but both the B-17 and B-24 oil reservoirs had a sump area that reserved enough oil to feather.  A leak would have to be in that sump to prevent feathering --- or severe one of the oil lines feeding the feathering pump.  

[DaveBB]

I just checked. The B-25 does have an oil sump for each engine.  It is supposed to allow prop feathering even if the main oil system is dry.  However there is also a drain with a bulb located below the oil system. If it leaks everything will run out.

I imagine the B-25s that couldn't feather the prop of a dead engine probably had massive shrapnel damage. 

I highly recommend "Warpath across the Pacific".  It is chock full of first hand accounts of low-level B-25 combat in the Pacific.  The book is worth it alone for the pictures.  Photos of Zeros attacking the B-25s, bombing ships at 100 feet, and most somber stuff, like B-25s crashing and exploding.

[eddiek]

I just checked. The B-25 does have an oil sump for each engine.  It is supposed to allow prop feathering even if the main oil system is dry.  However there is also a drain with a bulb located below the oil system. If it leaks everything will run out.

I imagine the B-25s that couldn't feather the prop of a dead engine probably had massive shrapnel damage. 

I highly recommend "Warpath across the Pacific".  It is chock full of first hand accounts of low-level B-25 combat in the Pacific.  The book is worth it alone for the pictures.  Photos of Zeros attacking the B-25s, bombing ships at 100 feet, and most somber stuff, like B-25s crashing and exploding.

Great book!  I've had my copy since 1995.  Gives a different perspective on the combat, their methods, and how they dealt with life in a combat unit, losing close friends, sometimes never knowing what happened to them, when they went down, etc.

[Soulyss]

IIRC one of the common field mods in the SW pacific was the installation of an extra drop tank in the bomb bay.  I'll poke through the books here and see I can find a reference.