Investigation Summary
NS11 was a North Sea class non-rigid airship, one of 14 ordered by the Royal Navy for the Royal Naval Air Service (RNAS). However, by its delivery in September 1918, the RNAS had amalgamated with the Royal Flying Corps to form the Royal Air Force (RAF), which operated the craft at the time of the accident. The airship was a record-breaker, having previously set a world record for non-rigid airships by completing a voyage of over 1,000 miles. On the night of the accident, the airship departed RAF Pulham around midnight. By 01:15, weather conditions near the Norfolk coast had deteriorated. Local residents near Cley next the Sea observed the airship flying low under a 'greasy black cloud' and noted that the engines sounded as if they were struggling. Shortly thereafter, the airship was consumed by fire. The Sheringham lifeboat was deployed but found only small fragments of aluminium wreckage and personal effects, including a coxswain's chair and a propeller blade. The disaster occurred just two days after the R34 airship had successfully completed the first double-crossing of the Atlantic, highlighting the volatile nature of early hydrogen-filled flight.
Final Conclusions
The official Court of Enquiry into the loss of NS11 returned an inconclusive verdict. However, the report noted that a lightning strike was a primary possibility given the meteorological conditions at the time of the explosion. Other factors considered included potential engine failure, as suggested by witness reports of abnormal engine noise shortly before the disaster.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Systems & Failure Modes
Hydrogen Envelope
The lifting gas used was hydrogen, which is highly flammable and susceptible to ignition from static discharge or lightning.
Fiat Engines
Two 260hp engines provided propulsion; witnesses reported they were working poorly or making abnormal noises just before the explosion.
Interesting Facts
- 01NS11 held a world record for non-rigid airships for a voyage exceeding 1,000 miles.
- 02The airship was powered by two 260hp Fiat engines.
- 03The envelope had a hydrogen capacity of 360,000 cubic feet.
- 04The accident occurred less than 48 hours after the R34 completed the first east-west Atlantic crossing.
- 05All nine crew members were killed; no bodies were recovered by the initial search party.
Safety Actions & Advisories
Inconclusive Court of Enquiry
Source ↗The official Court of Enquiry into the disaster was unable to determine a definitive cause, resulting in no specific safety mandates or design changes being issued immediately following the event.
Known Controversies & Unanswered Questions
Uncertainty of Mission Nature
Reference ↗While officially recorded as a routine mine-hunting patrol, contemporary reports and local accounts have questioned the exact nature of the mission, with some sources suggesting the 'official' designation may not have told the full story.
Alternative Ignition Theories
Reference ↗Although a lightning strike is the most common explanation, some experts and contemporary officers suggested the disaster might have been caused by engine failure or the airship's wireless equipment sparking and igniting valved hydrogen in the electrically-charged atmosphere.