Issue Number 33

November 2012

THE I.W.M. SUNDERLAND MK5 (ML796). Pt 4 0f 4.

By Tod Slaughter.Engines.


Although much work had been done in the interior of the Sunderland there was still a great deal to do.

The aircraft is made up of two decks. On the front lower deck is the anchor stowage department containing the capstan, anchor, anchor winch, front turret and the four fixed .303 machine guns fired by the pilot. Behind this is the toilet, a narrow staircase up to the cockpit and an access door to the wardroom. Aft of this is the galley then the bomb room and further back the waist gunners' positions. Then there is duckboard flooring to the rear turret. On the upper deck from the front is the cockpit with positions for the pilot and co-pilot. To the rear of them are the ASV (Airborne Surface Vessel), GPI (Ground Position Indicator), Wireless Operator, Navigator and Flight Engineer stations. Above the bomb room is the flare stowage along with the de-icing and hydraulic tanks and the mechanism for the bomb traverse.


The team was again split into smaller groups and each was allotted a task. A teammate and I tackled the narrow staircase from the anchor stowage section which exits up through the floor between the pilot and co-pilot. Others worked on the waist gun positions whilst two more fitted up the galley.

My next task were the two bunk beds in the wardroom and the two aft of the bomb room. One had been sent in the ship container so there was a something to copy. The aluminium tube was supplied by the IWM to construct the other three. Although they had a rectangular frame the centre supports were curved to what I measured was a 22inch radius. Try as I might I was unable to get a smooth curve so I searched around and came across the Martin top turret that the lads on the museum's Lancaster Mk10 were working on perched on a trestle. The lower half is curved armour plate and it just so happened that is was the diameter I was looking for! I packed the tubing with sand that I "borrowed" from a fire bucket and with two pulling at either end I got my curve with no kinking! They were cut to length and in no time we had the three remaining bunks riveted together.

The next task was to get the bomb door working on the starboard side. It was decided not to bother with the port side as that was where the general public put their heads in to have a look and we didn't want them to be decapitated!! On earlier marks the bomb doors had to be taken down manually but this proved too slow so the "boffins" came up with another method. It's not easy to explain but a frame was built around the bomb door which was hinged at the top and gripped centrally at the bottom by a bomb release catch. This held the bomb door in place flush to the fuselage under the wing. When the pilot pressed a button in the cockpit the bomb release let go of the lower catch and then bungee cord dragged the frame inboard pulling the door free of the fuselage and allowing it to drop under gravity. Other bungee cord stopped it from crashing too heavily as it reached the bottom of its travel. As you can imagine it was very quick and very, very noisy!! The part that was missing on our a/c was that at the bottom of it's travel the door tripped a micro switch which actuated the motor that made the bombs traverse out from the fuselage to a point out under the wing. When the Duke of Kent paid us one of his visits we showed him and I think that he was quite impressed but not so his equerry and body guard whom we had failed to tell of our intention. The crash and bang made them a bit jumpy!! Our best reaction was from a lady writing an article for a magazine who, when we showed her, actually screamed!! Most gratifying!

One of the jobs that I did proved to be quite a puzzle. It was the camera stowage frame which is situated on the port side halfway along the duck boarding towards the tail. Although I made it precisely to Normans drawing I could not work out how, when it was swung down to the operating position, it fixed to the floor stringers between the frames. To find out Geoff and I went down to the RAF Museum at Hendon to have a look at how it fitted on theirs. To our surprise the stringer positions were completely different!! This proved to us that Rochester built Sunderland's and those built elsewhere (i.e.. Blackburn) could be quite a bit different in fine detail. Anyway I got it fixed in the end!!

Geoff our museum engineer was building the deck over the bomb room but he had been issued fairly soft commercial aluminium to construct it. This would be OK as long as they didn't want to hang "real" bombs on it! Soon after this he retired and we had two IWM engineers join us Dennis and Dave each bringing at higher level of expertise. It was also to help us move things along a bit quicker as we had been on ML796 for almost thirty years!!

Then we had a request from Norman. Could we check the dihedral of the wings! I never even knew there was a dihedral! It was back to trigonometry. We measured the height of the wingtip to the hangar floor (A) then from the centre point of the wing against the fuselage to the floor (B) and subtracted (B) from (A). Then we measured the distance between the two points on the hanger floor. We had Opposite over Adjacent, which if I remember correctly, is Tangent! We did this both port and starboard just in case the aircraft was tilted to one side on the beaching gear. Someone produced a book with logarithms, Sine, Cosine etc. The result on both sides was as close to 3 degrees as makes no difference. With all the messing about that we had done it was still "spot on!"

Why had we been asked? We were soon to find out. I was called to the office to see Norman and the IWM chief Engineer Chris C. They had plans to get the bomb door mechanism working in full with real 500lb bombs!! I gave them the bad news that with the aluminium used there was "no chance" as it would not bear the weight. The next thing was that Dennis and Dave were removing the floor over the bomb room and replacing it with a much higher grade of "ally". They did a brilliant job and I picked up a few "wrinkles" from them. The bombs are supported by a frame which runs out under the wings on roller bearings. The bearings were standard but they were fixed to the upper floor by brackets made from ten gauge aluminium which we needed to bend to a squared off "U" shape. We knew that to prevent it cracking we would have to apply heat but how would we know the temperature? Dennis (IWM) nipped into the toilet and reappeared with a plastic cup containing liquid hand soap which he smeared on the area to be bent. He then heated it up with a blowtorch until the soap dried and turned brown. "You've got five minutes to work on it." he said. We performed the right-angled bends with not the slightest problem!!

The IWM had been putting pressure on the team to discontinue Tuesday evening working because there was no museum supervision. As by that time there were less than a handful of us we reluctantly had to agree to their requirements. In my case it meant that I would only be working every other Sunday as our engineers didn't want to work every Sunday. The biggest loser was George B. who was some fifteen years my senior as it was Tuesday evenings that kept him going. Within a few months he had gone to that great airfield in the sky! But he had the last laugh. As his wife did not approve of his Duxford visits, he choose halfway through the service "The Dambusters' March" and the curtains closed to the strains of the title music from "633 Squadron"!!

Whilst this was going on Dennis and Dave who had access to many flight instruments were busy working in the cockpit fitting up the control panels. Dave searched books for those that could not be found and enlarged to the correct dimensions. Photos taken from them which when fitted into the instrument panels and looked like the real thing unless you peered round behind and there were no innards!!

We then had to move again as "Air Space" was nearing completion and they wished to hang aircraft from the roof. ML796 was destined to go the T 2 hanger, north side, which was closest. To get the Sunderland in it they needed to remove the fin so we told them how we had fitted it. To say that they were taken aback was an underestimation of their reaction. With Health and Safety in mind they hired proper lifting equipment for its removal and in the process damaged it a bit. Not much, but enough for us to be able to "wind them up" a little!

By the time it came to return to Air Space things had changed. The Museum's Chief engineer had retired through ill health and the Museum had a new director. The idea of getting the whole bomb mechanism working was shelved despite Norman offering to fund much of it himself. It was decided that the paint on the aircraft needed freshening up, as it was the anniversary of the Berlin Airlift, but as we were back inside where no spraying was allowed so many volunteers from other projects were roped in to rub it down and then apply a coat of white gloss paint with six inch rollers!! This was a marathon task but the end result was a good thick coat which looks as good as new today.

The aircraft was taken off its beaching gear a put onto steel supports where it sits today. Our very last job was to fit the guns to the turrets and fuselage so that she really looked like a "Flying Porcupine"!