Glaser-Dirks DG-400 accident near Longmont, Colorado, May 4, 1986
On May 4, 1986 at about 10:50 pm local time, a Glaser-Dirks DG-400 (glider), registered N40Z, was substantially damaged in an accident near Longmont, Colorado. It was a personal flight under general aviation rules (Part 91). 1 person had minor injuries. The weather was visual conditions (good weather).
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The NTSB's probable cause their words, unchanged
The NTSB has not yet published a probable cause for this accident. Investigations usually take one to two years; this page updates when the final report is released.
Source: NTSB aviation accident database, copy made October 4, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- May 4, 1986 · about 10:50 pm local time
- Place
- Longmont, Colorado · map
- Type
- Accident
- Injuries
- 1 person had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft
- Glaser-Dirks DG-400 · all DG-400s on the register
- Registration
- N40Z · registry record · serial 4-144
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
THIS EXPERIMENTAL GLIDER HAS A STOWABLE 2 CYCLE ENG MOUNTED BEHIND THE COCKPIT. WHEN THE ENG IS STOWED THE GLIDE RATIO IS ABOUT 40:1. WHEN THE ENG IS DEPLOYED BUT NOT RUNNING, THE GLIDE RATIO IS ABOUT 10:1. WHILE RETURNING AFTER A 4 HR AND 50 MIN FLT THE PLT DECIDED ENG PWR WOULD BE NEEDED TO REACH THE ARPT. HE DEPLOYED THE ENG BUT IT WOULD NOT START. AN OFF ARPT FORCED LANDING WAS NECESSARY AND THE ACFT HIT A TREE.
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: private
- Ratings: multi-engine land; single-engine land; instrument: airplane; rotorcraft: glider
- Flight time: 1,278 hours in all; 43 in this make and model; 79 in the last 90 days
- Medical certificate: Class 3 (valid medical--w/ waivers/lim.)
- Seat: unk
The aircraft
- Airframe total time: 43 hours
- Last inspection: annual inspection, October 31, 1985; 43 hours since
- Maximum gross weight: 1,056 lb
- Seats: 1
- Landing gear: fixed
- Engine: Rotax 2 CYCLE (piston); 0 hours total
The flight
- Departed from: 1V5 Boulder CO at 6:00 pm
- Flight plan: VFR
- Runway 0
Weather at the time
- Light: daylight
- Wind: from 200° at 20 knots
- Visibility: 75 statute miles
- Sky: broken clouds at 10,000 ft; not recorded
- Temperature: 82°F (28°C), dew point 0°F (-18°C)
- Altimeter: 29.00 inHg
- Observation at 10:45 pm from BJC, 19 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 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.
About this page
Everything above comes from the NTSB's public accident database: the narrative, probable cause and findings are the NTSB's own words, and the coded tables behind its report (pilot, aircraft, flight, weather, injuries, sequence of events) are written out in plain English. Pilots' ages, home towns and medical details are left out on purpose. The documents and photographs are the NTSB's docket, the folder of records gathered during the investigation, shown as the NTSB released them (the NTSB redacts some personal details first) and listed under the NTSB's own titles. This site's own text never names pilots, passengers or anyone else involved. A preliminary report describes what is known soon after the event and can change; the final report, with the probable cause, usually follows one to two years later and this page is refreshed when it does. Case number DEN86LA127.