NYC94FA176 · WDL 1B
WDL 1B · Accident: loss of control in flight on approach
From Republic Airport (FRG) to an unrecorded destination
Event
- NTSB case
- NYC94FA176
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Accident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- API-reported fatalities
- 0 · all aircraft and ground
- Ground fatalities
- 0
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- General aviation
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
WDL 1B
- Aircraft type
- WDL 1
- Category
- Blimp
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N317TW
- Operator
- Airship Inernational
- Onboard fatalities
- Unknown
- Route
- From Republic Airport (FRG), Farmingdale, NYTo not recorded
- Aircraft age
- Not recorded
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Part 91: General Aviation
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- Approach
- First occurrenceThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- Loss of control in flight
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Substantial
Cause areas
- Blimp/airship equipment › Collapsed
- Blimp/airship, gas/air pressure/flight control sys › Inoperative
- Manufacturer › Acft/equip, inadequate design
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
AFTER ABOUT 40 MINUTES OF FLIGHT, THE AIRSHIP CREW NOTED THE ENVELOPE PRESSURE BEGAN TO DROP. THEY TURNED BACK TO THE AIRPORT & DROPPED 300 LITERS OF WATER BALLAST 'PER THE FLIGHT MANUAL.' AT ABOUT 700'AGL & 2 MILES FROM THE AIRPORT, WITH THE PRESSURE LESS THAN 15MM, THE CREW REALIZED THEY WOULD NOT REACH THE AIRPORT. THE AIRSHIP WENT INTO A NOSE LOW ATTITUDE & WOULD NO LONGER MAINTAIN ALTITUDE. THE CREW SHUT DOWN THE ENGINES & ELECTRIC SYSTEM & LANDED IN A STREET, BUT THE GONDOLA & FORWARD PART OF THE ENVELOPE WERE DAMAGED. INVESTIGATION REVEALED THE CENTER DAMPER VALVE WAS OPEN. THERE WAS EVIDENCE THAT DURING FLIGHT, THE OPEN VALVE ALLOWED THE FORE & AFT BALLONETS TO EMPTY & THE CENTER BALLONET TO FILL. APPARENT, OVER-FILLING OF THE CENTER BALLONET RESULTED IN CRUSHING OF THE COLLAPSIBLE TUBE (TRUNKING) THAT WAS USED TO FILL THE FORE & AFT BALLONETS. THERE WAS EVIDENCE THAT AS THE AIRSHIP DESCENDED, THE TRUNKING REMAINED CRUSHED, THE ENVELOPE PRESSURE DROPPED, & THE FORE & AFT BALLONETS WOULD NOT CONTROL THE TRIM OF THE AIRSHIP. A POSTACCIDENT CHECK OF THE CENTER DAMPER VALVE REVEALED THAT IT WAS OPERABLE; THIS VALVE WAS FOR MAINTENANCE USE ONLY & SHOULD HAVE BEEN CLOSED FOR FLIGHT. THE CREW REPORTED HELIUM CONTAMINATION DURING SEVERAL DAYS PRECEDING THE ACCIDENT. PURIFICATION OF THE HELIUM HAD NOT BEEN ATTAINED & MORE HAD BEEN ADDED TO KEEP THE TOTAL AMOUNT HIGH, WHICH RESULTED IN LESS SPACE FOR THE FORE & AFT BALLONETS TO EXPAND.
Probable cause
INADEQUATE DESIGN OF THE AIRSHIP, WHICH ALLOWED THE CENTER BALLONET TO OVERFILL AND TO COLLAPSE THE TRUNKING TO THE FORE AND AFT BALLONETS, RENDERING THE AIRSHIP UNCONTROLLABLE. FACTORS RELATED TO THE ACCIDENT WERE: INADEQUATE MAINTENANCE BY THE COMPANY/OPERATOR, WHICH ALLOWED THE PURITY OF THE HELIUM TO DECREASE; AND THE CENTER DAMPER VALVE TO OPEN (OR TO BE LEFT OPEN FOR FLIGHT).
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record NYC94FA176
- Event ID
- 20001206X02328
- Case number
- NYC94FA176
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
Source notes (4)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: 8bb083e7d1ddc97a66e8867ababf9d4f0cd16bf4ced19bb1ec779ad9b6f64727; retrieved 2026-09-23T00:40:08.156Z.