R101 departed from Cardington on 4 October at 6:24 p.m. for its intended destination of Karachi (then part of British India) via a refuelling stop at Ismaïlia in Egypt under the command of Flight Lieutenant Carmichael Irwin. Among the 12 passengers were Lord Thomson, Secretary of State for Air, Sir Sefton Brancker, Director of Civil Aviation, and Squadron Leader William Palstra, RAAF air liaison officer (ALO) to the British Air Ministry. On release from the mooring mast, the nose of R101 dipped alarmingly, forcing the airship to drop four tonnes of water ballast from the nose section to bring the airship back to true. This used all the forward ballast and reduced usable lift by almost half.
In contradiction of reports received from the airship about cruising height, observers both across the UK and in France were amazed and alarmed to see the airship flying so low. Even though the weather was foul, observers reported that it was so close they could see people at the windows of the airship.
In France, the low and erratic flying pattern further alarmed observers with a number concerned that it was going to hit rooftops (from witness reports at the formal inquiry held at the end of 1930).
Over France, R101 close to Beauvais ridge at a height estimated at 800 feet (240 m) went into a dive from which she slowly recovered. Rigger Church, who died three days after from his injuries, was sent forward to release the forward ballast bag but before he could do so the ship went into another dive and hit the ground. The cause of the first dive is not known, but after it, according to the surviving witnesses in the engine cars, the Officer of the Watch [OOW] rang for dead slow. Why he did so is a matter for conjecture because he must have known that without their thrust the ship would dive slowly into the ground, which it did. The enquiry estimated the impact speed at some thirteen miles (19 km) per hour.
The enquiry ascertained that there was no major structural failure in the ship. The only major fracture in the wreckage was at the rear of the new framework extension but it is unlikely this failed in the air: it either was broken in the impact or more likely cracked in the intense heat of the subsequent fire. The enquiry was of the opinion that the forward cover ripped open causing the forward gasbags to fail, but again this is conjecture. As Inspector McWade had pointed out she was very unstable in pitch, and she was badly overloaded and her cover rainsoaked.
Likewise it is not known why R101 caught fire. Several hydrogen airships had crashed in similar circumstances without catching fire. The enquiry thought that it was due to the engines being torn away but these were diesels, hot certainly but with no sparks. Many suggestions have been put forward from the ignition of calcium flares in the control car to electrostatic discharge. What is certain is that she caught fire almost at once and burned fiercely, and that her combustible but supposedly not inflammable heavy fuel oil caught fire too so she took nearly twenty-four hours to burn out.
A total of 47 of the 55 passengers and crew were killed immediately. A man who survived the crash later died at the hospital bringing the total to 48 dead.
The court of inquiry concluded that there was evidence there had been a failure of the outer cover of the upper nose. This, it was postulated, led to the destruction of a gas bag and loss of the flammable hydrogen lifting gas and caused the nose to drop. R101 had exhibited severe longitudinal instability in previous flights, and due to a unique design feature—lack of any wire bulkheads to prevent gas cell surging—they had been seen to move back and forth during flight.
During the inquiry held into the disaster, all reports both from the Air Ministry and the government painted glowing reports of the airworthiness and competence of the airship prior to its flight to India. This was in direct contradiction to the experiences of the technical and support crew who worked on R101 and also the observations of those working on the sister ship, R100. The true state of the construction only came to light in later decades as a number of technicians and also Nevil Shute made public observations and details of the problems that had accompanied the airship's construction.
Scrap contractors salvaged what they could of the R101 wreckage, continuing through 1931. The Zeppelin Company purchased five tons of duralumin from the wreck.
R101 was the end of British attempts to create lighter-than-air aircraft. Its competitor, R100, despite a more successful development programme, and a safe (though difficult) transatlantic trial flight, was mothballed immediately after R101 crashed and sold for scrap in 1931
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