A Westland Lysander.

ARMED FREIGHTER THE THISTLEGORM met her end in the Red Sea in 1941, when a Heinkel He111 hit her with two bombs.
Read James Tunneys excellent account in DIVER (The Truth Behind The Icon, December 2006) and you will learn that the ships manifest stated simply motor transport and that the cargo included Morris cars, Tilling Stevens and Bedford trucks, Ford 6x4s and Ford 2x4s, BSA M20 and Norton 16H motorbikes, Matchless G3Ls, Bren guns, tanks (or rather 4-ton multi-use tracked vehicles), two small-gauge Stanier 8F locomotives with rail cars, 303 Enfield carbines, mines, hospital equipment, fuel wagons, WW1 armoured cars modified and fitted with radio equipment, two paravanes (mine-sweepers), naval and field artillery, trailers, water-purifiers and much more.
You will also learn that the cargo contained aircraft spares, including wings, cowlings and engines, for delivery to the RAF in Egypt. Beyond this level of information you will draw a blank when it comes to dive briefings.
It was interesting to examine the aircraft parts in good condition on my first dives to the Thistlegorm last year. They were abundant, particularly in holds 1 and 2, but I couldnt identify them. A dive guide suggested that one stack consisted of Spitfire wings, but as these were only a few feet wide, I knew this was not the case.
I photographed every component I could see, and returned to the UK with pictures of wings with exposed ribs and spars, radial engine cylinders and parts of radial engine cowlings.
I then flew from my base airfield at White Waltham to the Imperial War Museum at Duxford to look for a match.
The only aircraft that looked right was a Westland Lysander, the British Army co-operation and liaison aircraft. This high-winged monoplane with fixed spatted undercarriage had a single radial engine. But without detailed drawings of the ribs inside the wings, I could not confirm this identification.

NEXT STOP WAS THE RAF MUSEUM at Hendon, which had a Lysander I could examine more closely. The Department of Research & Information Services staff was very helpful and sent me an extract from the Lysanders technical manual.
The pictures showed the structure of the ribs and helped confirm that the Thistlegorm wings were from a Lysander.
They are in very good condition, and the details of the aluminium internal ribs are clearly visible. Its unique wing shape gave the Lysander remarkable short take-off/landing capabilities, and the photos from the Thistlegorm show this clearly.
The cargo also includes objects that look like engine cowlings. These are in fact exhaust rings, which form a part of the cowling and were connected to a nine-cylinder radial engine.
There is an exhaust collector for each of the two exhaust ports on each cylinder that vent into two exhaust pipes. The stack on the Thistlegorm suggests that they were packed in wooden crates that have rotted away.
The Westland Lysander has an exhaust ring and a nine-cylinder Bristol Mercury radial engine. My photos looked very much like the ring found on the Lysander, but I wanted to check this with expert Colin Swann, an engineer at the Aircraft Restoration Company, based at Duxford.

I FLEW TO DUXFORD AGAIN, parking next to a Hurricane, a Focke-Wulf 190 and a couple of Spitfires!
The ARCO engineers immediately recognised the Thistlegorm wings.
In their workshop was a Lysander undergoing restoration, its uncovered wings looking exactly like those on the wreck.
Those parts of the Thistlegorm wings made of wood and fabric had rotted away, but what was left was a perfect match, with an aluminium-covered leading edge, internal ribs, spars
and braces.
The engineers were certain that the exhaust rings were not from a Lysander, however, but from a Bristol Blenheim IV, a fast, twin-engined light bomber with two radial Bristol
Mercury engines.
They explained that a Blenheim exhaust ring had two exhaust pipes, while the Lysander only had one.
They also agreed that the photograph of what some people had identified as Spitfire wings actually showed several tailplane sections from a Blenheim.
By sheer chance a Blenheim bomber was being restored at Duxford following a recent crash. The section of tailplane already in place matched the photographs of those on the Thistlegorm perfectly.
The ARCO engineers also produced a cylinder from a Bristol Mercury engine. Laid on its back, it matched those on the wreck. They would have been in wooden packing cases originally.
As I was about to leave, sharp-eyed Colin Swann took another look at Steve Cains photograph, and spotted a thick electrical cable with a fist-sized two-pin plug half-hidden under the Blenheim tail planes.
Thats an RAF trolley accumulator, he told me. Thats a trolley containing lead-acid batteries that was used to provide electrical power to aircraft on the ground.
At home, I found that I had taken a picture of another trolley accumulator. These are described as motorcycle sidecars in some dive guides!
Much has been written about the Thistlegorm cargo being destined for the British Army in Egypt.
When you next dive the wreck, look out for the Lysander wings, Blenheim tailplanes and exhaust rings, Bristol Mercury engine parts and the RAF trolley accumulators.
And dont forget the rubber waders used by the ground crew when they refuelled aircraft.
Both the Bristol Blenheim and Westland Lysander are very rare aircraft today. There are only two or three airworthy Lysanders, and no flyable Blenheims. The Thistlegorm probably has more Blenheim exhaust rings
than there are in every aircraft museum put together.
Thistlegorm divers should also spare a thought for the World War Two ground crew and pilots who were left waiting for the spares that now lie at the bottom of the Red Sea.
According to RN Gunner Glyn Owen, interviewed in John Keans SS Thistlegorm, the vessel carried aircraft fuselages in crates. If he was correct, there are even more aircraft parts on the Thistlegorm to be discovered.

Chris Frost
Lysander wing on the Thistlegorm
Blenheim engine in its cowling
interior of Lysander wing in the workshop at Duxford
Tailplane from a Bristol Blenheim being rebuilt at Duxford
cylinder from a Bristol Mercury radial engine
the Lysander exhaust ring had only one exhaust pipe
an RAF trolley accumulator on the Thistlegorm
A Bristol Blenheim in action