Airborne refuelling before WW2

I was thinking about practical minor technical PODS for WW2 and was wondering about airborne refuelling. Now, my cursory understanding of the topic, as supplemented by Wikipedia, suggests that there had been a few experiments in the West (US, France and Britain) from the end of WW1 to the start of WW2 but none of the powers had a useful system in place that was operational at the start of the war, or indeed, during the war.

Now, to my general POD - Britain completes the trials earlier in 1939 and has in operation by the start of the War enough units that high command/government appreciates that it is worthwhile and necessary, so isn't put on hiatus for the war.

Now if this happens, what kind of changes could we see? I would imagine it would take a year or two, with a late POD, for the process to become widespread enough to have much of an impact, but it could have all sorts of useful changes from mid war onwards.

Any ideas, thoughts?

http://www.flightglobal.com/pdfarchive/view/1940/1940 - 1219.html?search=Flight Refuelling
 

Ian_W

Banned
If you combined it with Bomber Command accepting that ASW and convoy escort is important, then the Battle of the Atlantic is won much sooner.
 
France Fights On used this one; the main difference was in antisubmarine warfare, allowing existing patrol types, mainly Sunderlands, to close the mid- Atlantic gap two years earlier than OTL, greatly reducing merchant losses to U-boats.

Which to be honest seems reasonable enough. Apart from a few bomber operations to peripheral targets at maximum stretch, oh and ferry flights like Takoradi, it's not easy to find targets that need aerial refuelling to attack and also don't involve trying to pass gas over enemy territory.

At least in Europe. In the Pacific theatre, on the other hand, it could change everything, because the island hopping campaigns may no longer be necessary, the Americans could be flying superfortress strikes on Japan from Midway- or British India- from mid 43 onwards.
 
A different technique for airborne refueling could conceivably have been based on hook-on technology such as was used in the 1930's in the USA with airships or a bit later in the USSR with large landplanes acting as the tankers.
 
Any ideas, thoughts?
Well whilst you're still using propeller driven aircraft it's going to be more complex, I'd say that it's probably going to be limited to larger two- or four-engine aircraft such as bombers, transports or patrol aircraft. Single engine fighters are going to be right out. Assuming that they continue experimenting and the probe-and-drogue method comes into service earlier it's going to be a major bonus for the early jet aircraft which had rather short legs, likewise it would help extend the range of the maritime patrol aircraft to reduce the size of or possibly even close the mid-Atlantic gap helping protect the convoys.
 
Well whilst you're still using propeller driven aircraft it's going to be more complex, I'd say that it's probably going to be limited to larger two- or four-engine aircraft such as bombers, transports or patrol aircraft. Single engine fighters are going to be right out. Assuming that they continue experimenting and the probe-and-drogue method comes into service earlier it's going to be a major bonus for the early jet aircraft which had rather short legs, likewise it would help extend the range of the maritime patrol aircraft to reduce the size of or possibly even close the mid-Atlantic gap helping protect the convoys.

Probe and drogue methods are not the only possibility. If an aircraft can actually hook on to the tanker that could be another approach, one that would actually work best with single-engine aircraft. Hook on trapeze techniques were perfected in the 1930's. There may be a reason the technique was not widely used operatoinally, but from what I've read flying a hook-on airplane required less skill than mating and flying with a tube or hose in a funnel.

Zveno-5.jpg
 
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Well whilst you're still using propeller driven aircraft it's going to be more complex, I'd say that it's probably going to be limited to larger two- or four-engine aircraft such as bombers, transports or patrol aircraft. Single engine fighters are going to be right out. Assuming that they continue experimenting and the probe-and-drogue method comes into service earlier it's going to be a major bonus for the early jet aircraft which had rather short legs, likewise it would help extend the range of the maritime patrol aircraft to reduce the size of or possibly even close the mid-Atlantic gap helping protect the convoys.

Maritime patrol is where I see the greatest potential. It wouldn't help stretch the range of fighters for bomber escort. There would just be too many aircraft requiring refueling to make it operationally possible. But Maritime Patrol/Convoy escort are lower in volume but critical missions that can offer great gains with a minor investment The basic technology had been worked out and with some actual use the now standard 'probe and drogue' system would probably have been developed faster.
 
1) it's most useful for single engine fighters (bombers already have the range), and it's least practical for them.

2) Early techniques really required a second crew member (not the pilot) to deal with capturing the hose, connecting it, etc. Again, this limits use for fighters - having to haul a second guy is going be a problem. OTOH, for long flights in the Pacific, you might have the second guy be a back up pilot (so the first can nap), be radar operator on target, etc.

3) as pointed out, it's really tough with single engine propeller planes.

4) even with twins, you probably have guns in the nose. If the fuel leaks on the nose during (or before or after) refueling, that's going to be interesting when the guns fire. (Set your self on flame? OK, with all metal planes, that's more likely to be a brief excitement, rather than a danger).

5) can't fly superfortresses from Midway in '43, they weren't operational then. Could you fly Flying Fortresses, probably refueling both on the way and on the way back?

6) Even in Europe, you could get planes near the Danish / Frisian coast, refuel, and proceed with a heavier bombload on to e.g. Romania, or someplace else that was only barely in reach.

7) While it wouldn't be a game changer, it would be useful, and would have opened all sorts of options.
 
With prop planes probe and drogue is the way to go. For multis you can have a fixed probe (for a visual look at the A-6). A retractable probe also works, lots of a/c have these. For single engine prop a/c you could go with a probe mounted well out towards the wing tip, you'll need plumbing to transfer the fuel from there equally amongst all the fuel tanks - the extra weight should not be too bad. Another possibility is a retractable probe behind the cockpit, the pilot needs a mirror +/- coaching from the refueler to hook up - this is a bit dicey at best.

IMHO for single engine, best thing is to have drop tanks widely available much earlier on.

Another key point, refuelers are not to be used where you have a likelihood of encountering enemy fighters - its bad enough when they are flying containers of jet fuel (kerosene) but when filled with high octane AVGAS just one spark/incendiary round and kaboom. In Europe this means refueling anywhere near where the Luftwaffe can operate is crazy- it won't take long for radar operators to figure out the pattern of refueling and directing fighters that way. Furthermore, mid-air refueling at night takes a lot of skill/practice, and just not feasible in WWII except in very permissive environments like mid-ocean.
 
2) Early techniques really required a second crew member (not the pilot) to deal with capturing the hose, connecting it, etc. Again, this limits use for fighters - having to haul a second guy is going be a problem. OTOH, for long flights in the Pacific, you might have the second guy be a back up pilot (so the first can nap), be radar operator on target, etc.

I'm sure Britain can sell the USN some Fairey Fulmars ;)

Seriously, for bombers and escort fighters, a lot of fuel would be used in take-off and climb to cruising altitude, so refuelling done over home territory could still extend range/payload by a worthwhile amount. Defensively it might also be useful for keeping interceptors orbiting at altitude for extended periods, if it could be used for single-seat, single-engined fighters.
 
Since British Airways experimented with air-to-air refuelling during the 1930s, the logical next step is topping-off Sunderlands near the coast just as they head out for anti U-boat patrols. Sunderlands carried enough spare crewmen that one could always be spared to stick his head out a top hatch and grab a hose. In the long run, they would probably develop some sort of fork or hook to grab the hose. Early in the war u-boats learned to fear any airplane over a convoy.

By mid-war, RAF Bomber Command enjoyed a surplus of second-rate Stirlings that couldne pressed onto tanker duty. Similarly, the USAAF had tired early-model B-17s that could be stripped of guns and converted to tankers.

The next logical step is Ferry Command stationing tankers orbiting over Gander, the southern tip of Greenland, south of Iceland and above the most Northerly Scottish Islands.

A third role is topping-off heavily-laden RAF and USAAF bombers over the English Channel. The challenge is fly tankers high enough to make them difficult for LW to intercept. Tanker orbits would need to constantly shift to confuse interceptors. Probably best to top-off at sunset.

Finally, more range would always be welcome while island-hoping across the Pacific. Even if the tanker orbit was only an hour off-shore, it could top-off returning aircraft leaking fuel from bullet holes. Tankers could also serve as aerial lighthouses guiding incoming friendly aircraft to newly-plowed runways.
As long as tanker orbits were beyond single-engine range from Japanese-held islands, there would be little risk of casualties.
 
4) even with twins, you probably have guns in the nose. If the fuel leaks on the nose during (or before or after) refueling, that's going to be interesting when the guns fire. (Set your self on flame? OK, with all metal planes, that's more likely to be a brief excitement, rather than a danger).

Wouldn't the majority of the fuel evaporate off before it had the chance to catch fire?
 
Another point to bear in mind is weight. Nowadays its nothing for a plane to haul around a few hundred kilos of refuelling gear to allow it to take on a few thousand litres of fuel when convenient. In the early days of Ww2 even a hundred kilos was a significant chunk of the payload of e.g a single engined fighter. If the fuelling gear weighs 30% of the max fuel load the whole thing is rather impractical.

Also reciprocating engines burned a lot of oil, especially radials. Late model skyraiders could haul enough fuel internally and in drops that they were duration limited by their oil tanks. So you might end up having to mid-air the oil, or more likely reconfigure the planes to haul aloft larger heavier oil tanks in addition to all the refuelling gear. Add in the aforementioned safety issues (which IMO mandate self-sealing tanks, built-in extinguishers etc) and I think its really only practical for large heavy aircraft. Which would usually have plenty of range anyway.....
 
Another point to bear in mind is weight. Nowadays its nothing for a plane to haul around a few hundred kilos of refuelling gear to allow it to take on a few thousand litres of fuel when convenient. In the early days of Ww2 even a hundred kilos was a significant chunk of the payload of e.g a single engined fighter. If the fuelling gear weighs 30% of the max fuel load the whole thing is rather impractical.

Also reciprocating engines burned a lot of oil, especially radials. Late model skyraiders could haul enough fuel internally and in drops that they were duration limited by their oil tanks. So you might end up having to mid-air the oil, or more likely reconfigure the planes to haul aloft larger heavier oil tanks in addition to all the refuelling gear. Add in the aforementioned safety issues (which IMO mandate self-sealing tanks, built-in extinguishers etc) and I think its really only practical for large heavy aircraft. Which would usually have plenty of range anyway.....

I hadn't thought about the weight of the refueling equipment being an issue. It makes sense though. There would also be performance issues with that extra weight.

Mid-air refueling doesn't seem to have been given serious consideration by anyone during the war, despite the earlier experiments, and the potential of it. That has me thinking there must have been good practical reasons for mid-air refueling to not have been used.

Hmm, 15 posts and I get to be the first to suggest mid-air refueling for the Battle of Britain? You guys are slipping! :) Germany could have also sent medium bombers and Me-110s out into the Eastern Atlantic.

Oh, for Pacific bombing missions by B-17s and B-24s, how many bombers could one tanker support? Islands like Midway can support only so many big planes. Would the tankers would also have to refuel the bombers on the return leg?
 
As I said earlier I don't think in flight refueling would be operationally feasable for most large scale bombing missions fighter sweeps or escort missions during WWII. The size of the missions (hundreds of aircraft) are just too large to orginize the meetups required for AAR. Even forming up the bombers into the combat boxes took time and an rganized effort that took an hour or so out of mission time before penetrating enemy air space.

However Antisubmarine missions were conducted by single or low numbers of aircraft that could have been refueled by a small, almost experimental force. It would have allowed the testing of methods and the building of skills.

I have actually been thinking about an Alternate Battle of the Atlantic where the experience of the British commercial flying boats is transitioned to Sunderlands then other ASW aircraft. It opens the possibility of closing the Mid Atlantic Gap much earlier. For this effort I am estimating less than 50 tankers and 100 modified Patrol aircraft would be needed to make a major difference. This is much different than the hundreds of aircraft that would be needed to support the bomber offensive.
 

marathag

Banned
Wouldn't the majority of the fuel evaporate off before it had the chance to catch fire?

The B-24 was notorious for a leaky fuel system, enough that some crews flew with bomb bays slightly open, to remove fume buildup, if not let actual liquid fuel drain out.
The C-109 Tanker version, was nicknamed the Exploder
 
British Airways experimented with AAR during the inter-war period, but it was not really needed until early jets were introduced. The early jets had such notoriously short range/endurance that they NEEDED AAR.

Early post-war, airlines stuck with pistons (Lockheed Constellation alongside Douglas Commercial 4, 6 and 7). They routinely landed to re-fuel in Ireland and Newfoundland. I doubt if civilian airlines could afford tankers.
As late as 1990 Aeroflot routinely re-fuelled in Gander, Nwfld during tourist flights from Russia to Cuba.
 
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