Dornier bomber: The smelly job of saving a unique plane
A year after the only intact example of a German Dornier Do-17 bomber was recovered from the English Channel, work to conserve it is well under way. It is a surprisingly smelly job.
Shot down with the loss of two of its four crew on 26 August 1940 - at the height of the Battle of Britain - aircraft 5K-AR spent more than 70 years buried in the Goodwin Sands off the coast of Kent.
Following an £800,000 salvage operation dogged by bad weather and bad luck, its fragile remains now reside in two polytunnels at RAF Cosford - one for the wings, the other for the fuselage.
The work of conserving this unique aircraft for future generations is proceeding slowly, as staff learn just what it takes to turn a piece of 1930s high technology into a display-ready artefact
The team's first priority was to clean the wreck, which proved a lot more difficult than anticipated.
When it arrived at Cosford it weighed nine tonnes, but only about 5.5 tonnes of that was the aircraft. The rest was sand, seaweed and barnacles.
Once out of the sea and in the warmth and light of the tunnels much of that sea life started to decay and rot.
"In the early weeks it was really unpleasant in here," recalls Mick Shepherd, Cosford's training and development manager.
"It wasn't difficult to be physically sick, it was a sort of reflex action because it was that bad. The smell was appalling.
"One of the girls... when she went home one night her mother wouldn't let her in the house, she smelt that bad, and hosed her down in the garden."
The other problem was a biological one.
The original plan had to been to saturate the plane for 10 minutes out of every 30 with a mixture of water and citric acid, to clean it, dissolve the salts left by seawater and stop the fragile aluminium of the airframe oxidising and decaying.
But as the deposits on the plane washed away they left behind a kind of naturally-occurring adhesive. Meanwhile, seaweed exudes a gel made of algae.
The alginate gel combined with the adhesive to block the pipes of the hydration system.
The pipes had to be periodically flushed out and great piles of gunk accumulated. One (partial) solution was to keep the sprays running continuously.
The plane is now certainly much cleaner and a good deal lighter than when it first came out of the water, but there is still a way to go.
Remarkably, even after all this time, some seaweed is still alive in the inner fuselage.
In March, after nine months of hydration, the fuselage was taken out of the polytunnel for the first time and deep cleaned. The hydration system sprays clean the outside surfaces well enough, but they do not get into the nooks and crannies.
Since then the fuselage itself has been split in two to make future excursions easier. But the team's biggest problems are still biological.
"As soon as we combat one form of algae or debris another one appears to take its place," says Mr Shepherd.
"We're now investigating painting the polytunnels to eliminate UV and reduce light."
The team are learning all the time.
During the winter they found they had to heat the polytunnels to stop the water in the hydration system pipes from freezing.
They had to install a sophisticated filtration system, with the aid of a local swimming pool expert, to clean the constantly recycled water.
And they have been working with experts at Imperial College London to find ways of ensuring the citric acid, which preserves the aluminium by forming a protective film over it, does not damage the aircraft's steel components.
Two of the four crew of Dornier 17 5K-AR died in the crash, two were made prisoner - the pilot Willi Efmert, and his navigator Herman Ritzel.
Herman ended up in a prisoner of war camp in Ottawa, from where he sent his mother a photograph which clearly shows a serious injury to his left hand. He lost two fingers in the crash.
He had joined the Luftwaffe because he had flown gliders before the war, but his daughter Gertrud Nowak says he never spoke about his role and in later life became a pacifist.
His grandson Christian has one memento of Herman's time as a prisoner. "Three or four years before he died he talked to me and said, 'I would like to show you something special that I manufactured while I was in my time as a prisoner of war.'"
It was a wooden picture frame he had made in the camp.
Working a knife gently into a crack in the frame, Christian prises it apart to reveal a hidden compartment in which an iron cross sat snugly.
Medals were banned in the PoW camp. This was Herman's way of ensuring his did not go missing.
The lessons the RAF Museum is learning will be useful for any other museum seeking to preserve an old aircraft rescued from sea water.
Individual items have been taken out and conserved and some are in remarkable condition - brass bullet cases and regulators, drive wheels with drive chains still attached and others with ball bearings still in place.
But it is still too early for anyone to say when the plane may eventually be moved to its final resting place at Hendon.
One thing is clear, it will not have been restored or reconstructed - it is too far gone for that.
And as Ian Thirsk, the museum's head of collections and the man overseeing the whole operation says: "If you were to restore it you couldn't call it a genuine Dornier 17 anymore. It would be a facsimile. There wouldn't be that iconic link to the past, that crucial part of British history."
So, the remains will be turned the right way up - the wreck is still lying on its back, as it was when found.
And the museum plans to reconstruct the lost canopy frame and the glazing assembly in the plane's nose, its beetle eye, which is one of the things that made the Dornier so recognisable.
"We'd like to recreate those to help the visitor interpret the object," Mr Thirsk says.
But in essence visitors will see only what came up from the bed of the English Channel, a battered and poignant relic of World War Two, along with the human story it tells.
"There were human beings involved in this battle on both sides," says Mr Thirsk.
"The Luftwaffe crews were much the same as the RAF pilots and their crew. And we want to get both sides of the story across, tell their side of things. How did they feel? Much the same as their RAF compatriots? What happened on that particular day?
"We want to tell the story of the battle... and why war is so futile."