Underwing Slipper Tanks

[Nigel Bunker]

Arew underwing slipper tanks uniquely British? They were carried by Mosquitos, Gnats, Buccaneers, Victors and I've even seen them on Viscounts and Islanders but I don't recall seeing them on any other nationality aircraft.

 

And before anybody mentions it, I am talking underwing, not the above wing ones carried by some Lutwaffe planes in WW2, so they are off topic.

 

I look forward to the comments.

[Giorgio N]

Not uniquely British ad some types from other countries used them (MiG-15, U-2), but sure more widely used in Britain than everywhere else 

[Graham Boak]

The Luftwaffe did have some types (OK, at least some Fw190A night bombers) with fairings between the tank and wing thus giving some of the same benefit of reduced drag.

 

I've a feeling I've also seen them on some US types - what about the B-52's outer tanks?

[stevehnz]

Would you also include the faired in underwing tanks on the 2TAF Tempests with these Graham? I'm guessing too, the weird assymmetrical tank on the Spitfire LR Mk II might come into this, I can never for the life of me see why a smaller one on each side was not tried, it could justr have been the answer to the Spitfire range problems & developed properly, might have obviated the need for the belly slipper tanks.

Steve.

Edited April 13, 2017 by stevehnz

[gingerbob]

One each side was tested on the Spitfire- not necessarily the same size.  Why they thought just the one was a good idea I don't know- it proved NOT to be!

[Graham Boak]

The key difference between the post war ones and most of the wartime ones, is that the wartime ones were intended to be dropped.  The conformal carriage reduced drag but introduces new penalties of difficulty of fit, of ensuring correct linkages, and safe clearance when dropped.  The designs on the jets are usually retained - early MiG 15s excepted but they were replaced by more conventionally-carried ones.

 

The problem with the asymmetric tank on early Spitfires was less the asymmetry, understandably unattractive but really only a nuisance in the cruise out.  It was how carrying weight outboard affected the handling - similar to the problems of carrying 4 cannon which was tried and abandoned until the 20-series wing.  The aircraft becomes too sluggish in roll and yaw.  You'd get much the same problem if the same fuel load was split between both sides, with a greater weight penalty from two small containers/piping/pumps than from one.  (With the benefit of hindsight, I think that the problems would stem from inertia coupling which wasn't recognised at the time.  Possibly this would be worse with the larger asymmetric tank.).  The real answer to the Spitfire range problem was the aft tank(s), when coupled with a larger tailplane to cope with the destabilising effect of the resulting aft cg.  However the demands of production didn't allow significant changes to the rear fuselage before the 20-series.  It's sometimes forgotten that the Mk.VIII not only had small leading edge tanks but also a larger fuselage tank, giving a significant boost in fuel volume over the Mk.IX without cg problems.  However the larger fuselage tank did lead to maintenance problems with access.  A Mk.VIII with aft tanks would have had more than twice the internal fuel of the standard Mk.IX.

 

I do have a small WiF set of (exceptionally) late Merlin Spitfires with big tails and (implicit) aft tanks, just what could have been.  

[iainpeden]

The Boeing plan to upgrade the F-4 had an under fuselage conformal tank - only got to the drawing stage though as the Super Phantom.