Feasibility of in-flight refuelling during WW2

An interesting history of in-flight refuelling:

http://www.afhso.af.mil/shared/media/document/AFD-100929-015.pdf

RCAFson said:

An interesting history of in-flight refuelling:

http://www.afhso.af.mil/shared/media/document/AFD-100929-015.pdf

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I was just reading that!

syscom3 said:

There were some serious studies that were being done by the engineering staff's in the PTO "Air forces" for mid air refueling for the B24's. Their perceptive was that a few hundred gallons of fuel in air could greatly help their operations that were long ranged anyway. A couple more hours of range, a bigger bomb load, lower takeoff weights, or better fuel reserves was what they wanted and were willing to get.

Since most of the operations in the PTO were over water, war weary B24's would be converted to tankers, and escort the bombed up B24's part way and top off their tanks after a few hours of flying. There was no need to escort them.

I think the 30th BG even proposed a system like that for a B24 to fly on a one way mission from Midway, bomb Japan and land in China.

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Just after Pearl Harbor, the U.S. Army Air Forces began working on an air refueling solution. With the help of Hugh Johnson, the man who had been in charge of FRL's Gander operations, they studied three primary concepts. First, planners looked at launching B-17 Flying Fortresses from Midway Island against Japan, with the idea of using modified B-24 Liberators as tankers. Second, they considered using B-24s from Hawaii with tanker support from U.S. Navy seaplanes. The third concept called for B-17s to tow fuel-laden gliders to serve as tankers.

Testing -- using a variation of the looped-hose method -- began in the summer of 1943 at Eglin Field, Fla. A B-17E served as the receiver and a modified B-24D as the tanker. The successful tests extended the B-17's range (with three tons of bombs) from 1,000 to 1,500 miles.

The problem now was how would the country's taxed manufacturers build the equipment for squadrons of B-24 tankers and B-17 receivers? Added to this dilemma was the time required for the aircraft modifications and crew training. Additionally, by mid-1943, Boeing began rolling out the B-29 Superfortress. The B-29 had a combat radius of 1,500 miles and carried twice the bomb load of the B-17.

In 1944, the U.S. Army Air Forces began studying the feasibility of equipping B-29s with an air refueling capability. The engineers at Wright Field, Ohio, determined it was possible to modify the aircraft, but the 1,500-gallon capacity of a B-24 tanker only

http://www.amc.af.mil/news/story.asp?id=123133645

Flyboy, I did not mean to imply that inflight refueling would have been easy, just that it was doable, had been done, and was planned to be done on a relatively large scale with technology that was available during the war.

As far as "experienced" RAF aircrews I did not have any particular hour figure in mind, I was just thinking that the RAF was demobbing most of Bomber Command and Coastal and that Tiger Force would have had their pick of aircrew who wanted to make a career in the RAF or keep their hand in the game until commercial jobs opened up.

Yes I understand the refueling is difficult but as you point out so are carrier ops and thousands of pilots were qualified for this during the war after relatively quick training. Many of these pilots wouldn't have qualified under peacetime standards but higher operational casualty rates we acceptable at the time.

I also believe that the difficulties of converting bombers into tankers has been overstated in this thread. We are not talking about really good tankers just wartime expedients. Think about the fuel systems on the Doolittle raiders and how low the standard for usability was.

Junglerot said:

Flyboy, I did not mean to imply that inflight refueling would have been easy, just that it was doable, had been done, and was planned to be done on a relatively large scale with technology that was available during the war.

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I think we're in somewhat agreement there. My point "doable" but not practical or efficient.

Junglerot said:

As far as "experienced" RAF aircrews I did not have any particular hour figure in mind, I was just thinking that the RAF was demobbing most of Bomber Command and Coastal and that Tiger Force would have had their pick of aircrew who wanted to make a career in the RAF or keep their hand in the game until commercial jobs opened up.

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Perhaps, but again there would have been training required, and even if you had a pilot with flight hours in the low four digits, it's not a matter of a few hours and you have effective air to air refueling capability. It took the USAF years to evolve it's tanker force where air to air refueling could have been done effectively and more importantly, safely...

Junglerot said:

Yes I understand the refueling is difficult but as you point out so are carrier ops and thousands of pilots were qualified for this during the war after relatively quick training. Many of these pilots wouldn't have qualified under peacetime standards but higher operational casualty rates we acceptable at the time.

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And the same situation could have happened for air refueling crews. I think the war planners at the time knew this, more reasoning why it never happened.

Junglerot said:

I also believe that the difficulties of converting bombers into tankers has been overstated in this thread. We are not talking about really good tankers just wartime expedients. Think about the fuel systems on the Doolittle raiders and how low the standard for usability was.

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Again, I don't know how much aircraft experience you have - first would you want to regularly fly and place your and your crew's life on an aircraft that had a system designed as a "wartime expedient?" The Doolittle raid was a "one shot" deal and the crew accepted the risk to complete the ONE mission. I guarantee that even by WW2 standards, operational practices would not have been allowed in the matter conducted during the raid, engineering officers would have been pounding on Arnold's door daily!

I worked on a 707 that had a "bolt on" drogue system so the aircraft's capability could be hidden. That mod took quite a long time to design and implement. Again, I don't know if you have worked on aircraft but I could tell you first hand that converting bombers into tankers is not and easy undertaking, and I think the link I posted clearly shows the consideration and the reasons why air to air refueling was not adopted during WW2.

I agree.

Peacetime trained crews (i.e. late 1930s) could conduct in flight refueling but it's asking too much from typical green WWII trained pilots.

davebender said:

I agree.

Peacetime trained crews (i.e. late 1930s) could conduct in flight refueling but it's asking too much from typical green WWII trained pilots.

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And look into some of the systems used in the 1930s when compared to the post war years. In the 30s air to air refueling was being done at low speeds and altitudes. Just compare some of the equipment - the reels, hoses and the drogue connectors.

What would be the point of extending the range of the bombers, if you couldn't do the same for the escorts.
The bombers already could outrange their escorts, and proved they couldn't survive without protection.
And the looped hose method wasn't doable by a single engine fighter, no matter how much training.

Aerial refueling might have been useful in a few situations, extending patrol distances , but at it state of the art in WW2, I don't see a use for it in combat situations.

In Luftwaffe Over America page 154, one of the approaches Germany played with was a simple method. A tanker would real out a hose, to be caught by a fork shaped device on the receiving aircraft. This fork would be retracted and a crew member would manually attach the hose to the fuel tank and refuel. There was minimal changes to the receiving aircraft. The downside is it's not exactly the safest way of doing it. Germany had converted Ju-86s and Ju-290 as tankers during the tests.

vikingBerserker said:

In Luftwaffe Over America page 154, one of the approaches Germany played with was a simple method. A tanker would real out a hose, to be caught by a fork shaped device on the receiving aircraft. This fork would be retracted and a crew member would manually attach the hose to the fuel tank and refuel. There was minimal changes to the receiving aircraft. The downside is it's not exactly the safest way of doing it. Germany had converted Ju-86s and Ju-290 as tankers during the tests.

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Basically introducing open fuel into the cabin area. That used to happen on the B-24 and on the Martin Mariner, the end result wasn't pretty.

I've noticed even on modern aerial refueling when they disconnect, you see a spray of fuel. A little residual fuel left in the line I guess.
Not something you'd want floating around the cabin for the rest of a mission.

tyrodtom said:

What would be the point of extending the range of the bombers, if you couldn't do the same for the escorts.
The bombers already could outrange their escorts, and proved they couldn't survive without protection.
And the looped hose method wasn't doable by a single engine fighter, no matter how much training.

Aerial refueling might have been useful in a few situations, extending patrol distances , but at it state of the art in WW2, I don't see a use for it in combat situations.

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The 5th, 7th and 11th Air Forces didnt see it that way. They saw a way to reduce the dangerous gross overloaded takeoff weights of their bombers while extending the range at the same time.