Never-before-seen footage of Hindenburg disaster revealed

Footage of the 1937 Hindenburg disaster, never before seen by the public, has been shared for the first time by a photographer's nephew.

While it's unclear why the film was never collected as evidence in the original investigation, documentarians believe it may provide fresh insight into what caused the fatal explosion which saw 35 people killed as it attempted to land in a New Jersey airfield.

The Hindenburg air disaster is one of the most famous in history, but it has never been confirmed what caused the German airship to catch fire.

READ MORE: MH370 'made many turns to avoid detection' before vanishing

Amateur photographer Harold Schenck happened to be on the ground with a Cine-Kodak 8 wind-up movie camera on that fateful May 6 day in 1937.

As he ventured around the Lakehurst airfield, filming the excited crowds and the airship getting closer, he could never have anticipated the terror that was about to unfold.

The Hindenburg had arrived in the US state after a three-day trip from Frankfurt, Germany.

The airship dropped its ropes at 7.17pm and four minutes later, witnesses on the ground saw flames erupt, according to historians.

The Royal Society of Chemistry says airships like the Hindenburg had metal frames covered in a varnished cotton that was then inflated with hydrogen, which is extremely flammable if it mixes with oxygen.

The airship was completely engulfed in just 32 seconds.

Unlike the newsreel footage that was analysed in the original investigation, Mr Schenck's footage shows more of the accident from an earlier stage.

"It was publicly put out at the time that he had (the footage) but nobody ever asked for it," Mr Schenck's nephew Bob says in a new PBS documentary, Hindenburg: The New Evidence.

"There was plenty of footage taken by the newsreels and nobody really cared, I guess, about angles."

READ MORE: Last survivor of Hindenburg airship disaster dies

Documentarians say Mr Schenck's footage captures a full broadside view of the ship from its nose to tail capturing its final seconds of flight as flames engulf it.

News crews who were already there filming the ship's arrival rushed to capture the explosion and crash, but all the best-known footage of the disaster is from similar angles.

Because of the placement of the aperture plate on Mr Schenck's camera, his footage shows the entire ship as it erupts, at an angle not seen before.

Mr Schenck also had time to rewind the roll and capture the aftermath, showing details of the girder structure, where the gas cells were and detail on how the flames progressed.

"As it exploded, he had the camera at his side and it was a wind-up camera, so he had the presence of mind to switch it on and pick it up at that moment," Bob Schenck said.

Because the newsreel photographers were closer to the chaos, their footage is very close to the bow or the nose of the airship, limiting investigators in determining the cause of the explosion.

Mr Schenck's footage shows the dropping of the landing ropes, with the new documentary theorising the ropes may have generated electricity that ignited the blaze.

READ MORE: First batch of Chernobyl-made vodka seized by secret service

In the documentary, archival technician Pat Doyan confirms the film is original as far as she can tell.

"If it was a print, you wouldn't see the circles or the squares because the printer blacks that off," Ms Doyan said.

"It's a little shrunken and it's got some aging – a little silver marring which tells me that it's old film.

"I can't say with 100 per cent certainty, but everything points to this film being authentic – that it was shot at that time."