Wdl 1B accident near Farmingdale, New York, September 11, 1994
On September 11, 1994 at about 3:11 pm local time, a Wdl 1B (airship), registered N317TW, was substantially damaged in an accident near Farmingdale, New York. It was an aerial observation flight under general aviation rules (Part 91). No one was hurt; 3 people were on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
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).
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- September 11, 1994 · about 3:11 pm local time
- Place
- Farmingdale, New York · map
- Type
- Accident
- Injuries
- No one was hurt; 3 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Wdl 1B
- Registration
- N317TW · registry record · serial 105
- Damage
- Substantial damage
- Flight
- Aerial observation flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
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.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
Pilot
- Certificate: commercial pilot
- Ratings: rotorcraft: airship
- Flight time: 3,200 hours in all; 1,642 in this make and model; 205 in the last 90 days; 54 in the last 30 days; 1,107 as pilot in command
- Medical certificate: Class 2 (valid medical--no waivers/lim.)
- Seat: left
The aircraft
- Airframe total time: 3,965 hours
- Last inspection: approved inspection programme, September 6, 1994; 23 hours since
- Maximum gross weight: 7,000 lb
- Seats: 6
- Landing gear: fixed
- Engine: Continental IO-360-CB (piston); 0 hours total
The flight
- Departed from: FRG Farmingdale NY at 2:20 pm
- Flight plan: none
- Runway 0
- A second pilot was aboard
Weather at the time
- Light: daylight
- Wind: from 300° at 12 knots
- Visibility: 30 statute miles
- Sky: clear
- Temperature: 61°F (16°C), dew point 0°F (-18°C)
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 2 | |||
| Passengers | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.