Lockheed Hudson & Ventura - Self-sealing fuel tanks?

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chris ballance

Airman 1st Class
129
121
Jul 21, 2022
Did the British order the Hudsons and Venturas from Lockheed with self-sealing fuel tanks? Did the Lodestars ever get them?
 
The Hudson and Lodestar had "wet" wings which means they did not have fuel tanks per se.
An area of the wing structure is made fuel proof and that becomes the fuel tank. Because of this the "self sealing" tanks on the Hudson consisted of a layer of self sealing material mounted externally on the lower surface of the wing. As far as I am aware there was no leak protection on the wing spars (the fronts and rears of the tanks) or dry-bay ribs (inner and outer tank skins) or on the top surface of the wing.
I would expect the Lodestar may have had a similar protection.
The PV-2 Harpoon had conventional separate self sealing tanks.
I do not know what the PV-1 Ventura had. It was developed from the Lodestar but the structure was considerably redesigned and that may or may not have included a dry wing and separate fuel tanks. The PV-2 Harpoon is essentially a PV-1 Ventura with a new wing but the reason for that new wing was increased wing area and overcoming structural flexing when fully loaded so the dry wing may or may not have been fitted to the PV-1. As for the B-34 Lexington - I do not know if it was a PV-1 or PV-2 derivative - or both.

I am sure someone out there has a -2 for the Ventura and Lexington. Even the -1 may provide the answer and the -3 definitely would
 
I have a few flight manuals for these aircraft. T.O. 01-75AB-1 is for the RA-29, RA-29A, PBO-1 and Hudson III and IIIA (December 20, 1942, revised Nov.20, 1943) shows 4 wing tanks, no mention of a wet wing but does states "The four fuel tanks, two forward and two aft of the main spar have a total capacity of 643 U.S. gallons."

T.O. 01-75EA-1 for the RB-37 (July 20, 1943) has a fuel system diagram showing 4 main tanks, an auxiliary tank on the outer portion of each wing (drop tank) and a left and right cabin tank. No other description.

The PV-1 Pilot's Handbook (April 15, 1943) similar to the RB-37, more detailed fuel system diagram.
 
Just having internet references I'm assuming the Hudson Mk. IIIA, A-29, A-29A, PBO-1 was the long range version with the Wright R-1820-87. So it would have the additional wing tanks.

I was just interested in what fuel tank protection the Lockheed family of aircraft had given that they sometimes had tangle with aircraft and flak.
 
Just having internet references I'm assuming the Hudson Mk. IIIA, A-29, A-29A, PBO-1 was the long range version with the Wright R-1820-87. So it would have the additional wing tanks.

I was just interested in what fuel tank protection the Lockheed family of aircraft had given that they sometimes had tangle with aircraft and flak.
If there were self sealing tanks installed on any of the mentioned aircraft, that decision would come at the direction of the customer, be it the RAF, USN or USAAF.
 
Thanks for that Flyboy. Somewhere I have a copy of the Erection and Maintenance for the USAAF trainer version of the Hudson series but I cannot find it just now. Will try again after breakfast.
It should cover the fuel tanks in more detail.
 
Okay 01-75KA-2 for the AT-18 shows
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The first section above relates to the "bullet proof" covering on the oil tank
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Tanks maintenance includes the following but unfortunately para 6, e is on one of the 15 odd pages missing from my copy
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I bet that the Hudsons and Lodestars suffered from chronic fuel leaks from the wings. Any information on this subject?
Petrol Tanks Leaking

Being a training unit, Hudsons often suffered heavy and hard landings. The top of the main undercarriage leg was fixed to the side of the petrol tank which was itself built into the framework of the wing and could not be removed. Over time, the large rivets holding the brackets were weakened slightly and they were not tight enough to prevent a very slight trickle of high octane fuel from leaking. This could be fatal being so near the hot engines. To cure this problem, the tanks were emptied and defumed and the access panels on the top of the wing removed so as to allow access to the interior wall where the problem was located. After much thought, some of the rivets were replaced with bolts and the remaining rivets were taken out and replaced with a different type. All the Hudsons received the same treatment and in addition orders went out to all pilots to report heavy landings so that the undercarriage could be inspected. This solved the problem.


 
Only indirect evidence for early Hudson fuel arrangements. I do not have a fuel tank diagram. The RAF says all Hudson I to IV had a maximum fuel load of 536 imperial gallons. The USN says its PBO-1 (Hudson III) had 644 US gallons of protected fuel and 36 gallons of protected oil tanks. If there was a change from unprotected to self sealing tanks you would expect fuel capacity to go down.

RAF, Wright Cyclone G205A, mark III range with 50 minute allowance, 1,465 miles at 155 mph at 10,000 feet, take off weight 20,000 pounds, including 400 pounds of bombs.

USN, Wright R-1820-40, PBO-1 range 1,890 miles at 129 mph at 1,500 feet, take off weight 18,837 pounds. 1,790 miles at 127 mph at 1,500 feet, take off weight 19,230 pounds. 1,750 miles at 131 mph at 1,500 feet, take off weight 20,302 pounds including 1,300 pounds of bombs.

PV-1, US gallons, 115 wing leading edge tank inboard of engine, 133 in wing behind the 115, 40 outboard of engine, where drop tanks attach, fuselage 84+161. Comes to 821 gallons, the USN uses 820 gallons. All protected. Provision for another 161 gallon protected tank in fuselage near starboard wing trailing edge. Bomb bay 210+280 unprotected, or a 189 protected tank plus 3x500 pound bombs. Oil 15 gallons behind each engine, protected, 35 in fuselage, near port wing trailing edge, unprotected. Self sealing cells protection weight 1,285.5 pounds. Oil tanks protected from 0.30 cal by "Armorite"

PV-2, US gallons, 115 wing leading edge tank inboard of engine, 133 in wing behind the 115, 245 outboard of engine, fuselage 161. Comes to 1,147 gallons, the USN uses 1,149 gallons. All protected. Bomb bay 177 protected+237 unprotected. Oil 20 behind each engine protected, 35 outboard of engine unprotected. (PV-2D outboard tanks 25 gallon, protected). Self sealing cells protection weight 1,255 pounds. Oil tanks protected from 0.30 cal by "Armorite"
 
Thanks Geoffrey for clarifying that.

So as suspected the PV-1 did have separate tanks rather than the Hudsons wet wing and the wing redesign was purely for increased rigidity and load carrying ability.

As noted above the Hudson wing was protected by an external layer of Linitex - from memory about 10-12 mm thick - on the lower surface only running from the front to rear spars. Not what I would call aerodynamically clean.
 
The illustration from the T.O. 01-75KA-2 is a tad misleading in that it conveys the impression that there are actual tanks per se. The description of a wet wing is best accurate.

The inboard walls are the fuselage wall, the frontmost and rearmost walls are the front and rear shear beams of the wing, the outboard walls are the walls of the two bays of the nacelle, and the two in the centre between the two tanks are the faceplates of the box spar.

The rubber was applied to the outside of the vertical walls so that means it is inside the wing leading edge for example. It was often covered in fabric secured with metal edge beads but I've seen no evidence of anything being applied to the outside wing skin.

Here for example is the forward shear beam where in just the last couple of weeks I have been removing the remaining rubber, and the inboard wall of a wheel well bay.

Despite now being some 80 years old the rubber is still flexible and has a tenacious grip on the metal but there has been some corrosion occur so off it has to come!
 

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The illustration from the T.O. 01-75KA-2 is a tad misleading in that it conveys the impression that there are actual tanks per se. The description of a wet wing is best accurate.

The inboard walls are the fuselage wall, the frontmost and rearmost walls are the front and rear shear beams of the wing, the outboard walls are the walls of the two bays of the nacelle, and the two in the centre between the two tanks are the faceplates of the box spar.

The rubber was applied to the outside of the vertical walls so that means it is inside the wing leading edge for example. It was often covered in fabric secured with metal edge beads but I've seen no evidence of anything being applied to the outside wing skin.

Here for example is the forward shear beam where in just the last couple of weeks I have been removing the remaining rubber, and the inboard wall of a wheel well bay.

Despite now being some 80 years old the rubber is still flexible and has a tenacious grip on the metal but there has been some corrosion occur so off it has to come!
Excellent! Members take note here - this is real world restoration, I equate this to digging up dinosaur bones! Thanks for this post!!!!

Where is this aircraft at? Can you give us additional information?!?!?
 
Thank you Denys for clarifying that.

My Hudson experience was limited to three aircraft
  • two civil aircraft that had been on the civil register until the 1977 (when I worked on them) and at least one was still flying several years after that. On both of them all traces of the rubber had been removed which is why I did not know about the rubber on the spar webs and tank end ribs - and why I thought that those surfaces were possibly unprotected.
  • one upside down military wreck in PNG that was in relatively good condition and still had the covering on the lower surface of the wing with quite a step (3/8 to 1/2 inch) where it started and finished - tapered front and rear over a short distance - maybe 3 inches. Those dimensions are "flexible" as I am trusting to memory of a wreck last visited in 1973 and my memory is far from perfect (as I keep discovering). There was nothing to suggest any protection on the top surface of the wing.
And I agree with Flyboy - more details please.
 
No problems chaps always happy to publicise our project, here's a thread I post progress to on a local (NZ) forum.


If you go back to the page 1 you can have a good long read, plus you'll see some of our other projects.

It may astound you to know that it is generally accepted that there are 10 complete Hudsons in the world (that is have all four points of the airframe nose, tail, wingtips) and of those 4 are here in NZ and 2 of those are here in Christchurch, ours and the RNZAF Museum's.

The top of the main undercarriage leg was fixed to the side of the petrol tank which was itself built into the framework of the wing and could not be removed.

hmmmmmmmmm...I can't agree with that exactly. There are two vertical members, one each side, at the front of the underwing portion of the nacelle at the front of the oil tank bay..

They are fixed for sure but the leg itself is an inverted L and the crossmember has fittings on it to bolt to said members. Off the same fixture cluster at each end of the cross member are pickup points for other brace struts all of which bolt in as well and then the No2 engine frame hangs off the forward side. You can see all this in the first photo here (taken in a dark age when I was young and foolish enough to embark on this mission), especially the two rows of three bolts fixing the leg cross member in place.

The second photo shows the port oil tank and you can see it is forward of the spar and outboard of the forward wet cell. The third photo shows the leg cross member from inside the oil tank cell, with the oil feed work in progress routing off to the outboard side of the firewall.

Hope you enjoy :)
 

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Thanks Denys - great post and link

If anyone out there has this TO I would love to see a copy posted here to clarify how bad my memory has got on how thick the Linetex was.

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