Why aerial refueling came too late for WWII?

[trurle]

From wikipedia,
https://en.wikipedia.org/wiki/Aerial_refueling#History
seems the ideas and technology for effective aerial refueling was available even before WWII
(in 1938 looped-hose refueling was operational technology, at least for British). The understanding of benefits of aerial refueling seems to be also present, because aerial refueling stunts on shows were common since 192x period.

It seems counter-intuitive to me why obsolete, low-speed bombers of interwar era were not converted to flying tankers, to support some of the following missions:

1) Extension of operational range of fighter escorts
2) Lengthening of loiter time of high-altitude interceptors.
3) Extended-range strategic bombing
4) Long-endurance patrol and rescue aircraft
5) Fighters/ground attack aircraft trading some of fuel tank capacity for extra armour and ordnance.

OTL, cumbersome solutions like long-range fighters, aircraft carriers, hydroplanes refueling from submarines and bomber one-way flights were used instead of aerial refueling. Why? Just mental inertia? Still lack of knowledge? Technological failure? Systemic/political/psychological problems?

 

[Draconis]

Two reasons just off the top of my head.

1. The need for longer ranging aircraft was not as evident pre-WW2. Particularily for fighters as bombers were thought to be able to fight through enemy interceptions.

2. Propellers. Trying to refuel, especially single engine airplanes with that big propeller on the nose would require a long heavy, draggy probe extending from one of the wings.

I think it was the advent postwar of speedy but thirsty jets that really made air to air refuelling a more useful and required procedure.

 

[trurle]

Two reasons just off the top of my head.

1. The need for longer ranging aircraft was not as evident pre-WW2. Particularily for fighters as bombers were thought to be able to fight through enemy interceptions.

Yes, that "fast bomber" concept (discredited by 1942 though). Makes sense.

2. Propellers. Trying to refuel, especially single engine airplanes with that big propeller on the nose would require a long heavy, draggy probe extending from one of the wings.

I agree the fuselage-mounted drogue&probe stability is very bad with single-motor aircraft with tractor propeller. It may be few percents of explanation - looped-hose system connected recipient from tail, and twin-engine fuel recipients would be more forgiving to propeller-caused troubles too.

 

[Post]

Apart from that probably in-air refueling in contested airspace wouldn't be the most fun thing to do. I don't see bf-109s refueling over England in 1940 or Spitfires over France or Germany in 1942.

 

[SpicyJuan]

The German's planned to use aerial refueling for the Amerika Bomber project. From what I remember, aerial refueling was tested with Ju 290/390s around 1943/44.

 

[Riain]

In WW2 there was huge potential for range increases without IFR. The Spitfire went from 90 gal in the MkV to 132 gal in the MkVIII, then there was all sorts of drop and slipper tanks; the Seafires in the BPF had an endurance of 3 1/2 hours compared to 1 1/2 hours of a MkII in the BoB. Its pretty tough on pilots to sit in the cockpit of a fighter from 3 1/2 - 6 hours.

 

[trurle]

Its pretty tough on pilots to sit in the cockpit of a fighter from 3 1/2 - 6 hours.

A6M "Zero" did carry enough fuel for 6-8 hours of cruise, and pilot fatigue was not considered critical. May be because of Japanese pilot`s childhood training to sit without proper chairs.

 

[overninethousands]

I think it was the advent postwar of speedy but thirsty jets that really made air to air refuelling a more useful and required procedure.

+1 The P-51 range remained unmatched by jets until perhaps the late 40's or beyond (F-84) and then supersonic flight cut it again. P-51 could fly to Berlin and back from England, or from Okinawa to southern Japan and back, escorting B-29s ten times heavier. Hell of a range. Think about the XF-88 / XF-90 / XF-93 competition for a long range supersonic fighter to escort B-36s, that failed miserably.

 

[NOMISYRRUC]

Before the war Flight Refuelling Ltd was using converted Harrow bombers to refuel the Empire Flying Boats of Imperial Airways.

IIRC it was suggested that the Harrows be used to refuel RAF Coastal Command's Sunderlands to fill the "Black Gap," but it was decided that the available resources were better used elsewhere.

 

[Gunnarnz]

2. Propellers. Trying to refuel, especially single engine airplanes with that big propeller on the nose would require a long heavy, draggy probe extending from one of the wings.

Why does it have to extend from a wing? Couldn't it extend from the spine of the aircraft instead? That would avoid lateral trim problems, and allow the possibility of a retractable version. If the concern is that the pilot couldn't see it, simply extend it so that it peeks over the top of the cockpit.

 

[Draconis]

Why does it have to extend from a wing? Couldn't it extend from the spine of the aircraft instead? That would avoid lateral trim problems, and allow the possibility of a retractable version. If the concern is that the pilot couldn't see it, simply extend it so that it peeks over the top of the cockpit.

Because with a single engine plane with that big prop up front if there is any droop in the fuel line it sags into the propeller. Pilots are not perfect and air turbulence and the slipstream from the tanker plane are also a factor.

 

[Riain]

The probe must be in a good place for the pilot to conduct the delicate moves needed to push the probe into the basket. A probe on the centreline would have to be up above the cockpit, forward enough where the pilot can see it and high enough that the hose wouldn't swing down into the propellor disc, therefore it would be so massive that it would dramatically reduce the performance of the aircraft.

 

[trurle]

A probe on the centreline would have to be up above the cockpit, forward enough where the pilot can see it and high enough that the hose wouldn't swing down into the propellor disc, therefore it would be so massive that it would dramatically reduce the performance of the aircraft.

More performance penalty than a 1-ton fuel tank? And how about contemporary looped-hose?
In general, i expect light fighter performance penalty from refueling probe on par with additional 20mm gun (may x2 drag and half the deadweight).

 

[Dathi THorfinnsson]

Twin engine fighters like the P38 would deal with it better.

Imagine a Japanese bombing campaign where the b29s need fighter escort.

 

[marathag]

The probe must be in a good place for the pilot to conduct the delicate moves needed to push the probe into the basket. A probe on the centreline would have to be up above the cockpit, forward enough where the pilot can see it and high enough that the hose wouldn't swing down into the propellor disc, therefore it would be so massive that it would dramatically reduce the performance of the aircraft.

With a bigger set of blades to worry about

The Probe can be offset away from the fuselage

 

[tomo pauk]

Usual long-range fighters (Zero, P-51, P-38, Hornet) were more limited by pilot's ability to fly 6-7+ hour missions than by fuel tankage. A reason to why P-82 went with 2 crew members.
In-flight refueling will be much more important for jets since those were using far more fuel to get to same distance.

 

[PMN1]

I think there would be just too may fighters or bombers that need AAR to make it viable.

Using AAR for increasing the range of a maritime patrol aircraft is another matter, the tanker either meets up with the patrol aircraft in the vicinity of the convoy or accompanies the patrol aircraft on its way out, tops it up at a certain time and head back home.

 

[marathag]

Usual long-range fighters (Zero, P-51, P-38, Hornet) were more limited by pilot's ability to fly 6-7+ hour missions than by fuel tankage. A reason to why P-82 went with 2 crew members.
In-flight refueling will be much more important for jets since those were using far more fuel to get to same distance.

Refueling would be more important for Bombers.

With refueling, Bombers could take off with more bombs and less fuel, to get around maximum takeoff weight restrictions.

Once in the air, tanks could be fully filled.

B-29s had enough tankage that could only be completely filled with a light bomb load, and still needed very long takeoff runs

With earlier refueling, shorter airfields could be used for takeoffs with less stress on the engines, and then refuel once at medium altitude for even longer missions than OTL

 

[StevoJH]

Sure, but its one thing to have enough tankers to refill a squadron or even wing size formation.

Its quite another when you are sending raids out that have hundreds or up to a thousand bombers per night.

 

[overninethousands]

The first US raid on Berlin March 6,1944 had over 800 bombers, plus the escort. Waaaay too much for aerial refueling. By contrast patrol aircrafts trying to close the mid-Atlantic gap... shame it was not used.