Glasflugel STD Libelle 201B and Glaser-Dirks DG-400 mid-air collision near Oso, Washington, April 2, 2004
On April 2, 2004 at about 1:00 am local time, 2 aircraft, Glasflugel STD Libelle 201B (N161D) and Glaser-Dirks DG-400 (N400WJ), were involved in a mid-air collision near Oso, Washington. 1 person was killed and 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 pilot of the Glaser-Dirks (lead glider) failure to maintain clearance form the Glasflugel (trailing glider) resulting in a mid-air collision while maneuvering.
The pilot of the Glaser-Dirks (lead glider) failure to maintain clearance from the Glasflugel (trailing glider) resulting in a mid-air collision while maneuvering.
Source: NTSB aviation accident database, copy made October 4, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- April 2, 2004 · about 1:00 am local time
- Place
- Oso, Washington · map
- Type
- Accident · mid-air collision
- Injuries
- 1 person was killed and 1 person had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft 1
- Glasflugel STD Libelle 201B · all STD Libelle 201Bs on the register
- Registration
- N161D · registry record · serial 22
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
- Aircraft 2
- Glaser-Dirks DG-400 · all DG-400s on the register
- Registration
- N400WJ · no longer on the register · serial 4-91
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative for the Glasflugel STD Libelle 201B final · quoted from the NTSB record
While flying in trail along a ridgeline at the same altitude, the pilot of the Glaser-Dirks (lead glider) made a left turn, while the pilot of the Glasflugel (trailing glider) remained on course over the ridgeline. The Glasflugel pilot reported that he recalled that the Glaser-Dirks was at his 10:00 position when he encountered turbulence and he looked down to check his airspeed. When he looked back up, he lost sight of the Glaser-Dirks and assumed that he had rolled out to run the ridgeline to the south. The Glasflugel pilot continued along the ridgeline to the north when the Glaser-Dirks pilot transmitted to the Glasflugel pilot to "watch out/it." The Glasflugel pilot looked around to his left and spotted the other glider about 80 feet away at his 8:00 position and converging at the same altitude. The Glasflugel pilot reacted by making a right banking turn. During this maneuver, the left wing tip of the Glasflugel glider came up under the right wing of the Glaser-Dirks glider. The left wing tip of the Glasflugel contacted the underside of the right wing of the Glaser-Dirks about 13 feet 5 inches outboard of the wing root resulting in the outboard section of the right wing separating in flight. The pilot of the Glaser-Dirks was fatally injured, while the pilot of the Glasflugel was able to bail-out and deploy his parachute.
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 NTSB's narrative for the Glaser-Dirks DG-400 final · quoted from the NTSB record
While flying in trail along a ridgeline at the same altitude, the pilot of the Glaser-Dirks (lead glider) made a left turn, while the pilot of the Glasflugel (trailing glider) remained on course over the ridgeline. The Glasflugel pilot reported that he recalled that the Glaser-Dirks was at his 10:00 position when he encountered turbulence and he looked down to check his airspeed. When he looked back up, he lost sight of the Glaser-Dirks and assumed that he had rolled out to run the ridgeline to the south. The Glasflugel pilot continued along the ridgeline to the north when the Glaser-Dirks pilot transmitted to the Glasflugel pilot to "watch out/it." The Glasflugel pilot looked around to his left and spotted the other glider about 80 feet away at his 8:00 position and converging at the same altitude. The Glasflugel pilot reacted by making a right banking turn. During this maneuver, the left wing tip of the Glasflugel glider came up under the right wing of the Glaser-Dirks glider. The left wing tip of the Glasflugel contacted the underside of the right wing of the Glaser-Dirks about 13 feet 5 inches outboard of the wing root resulting in the outboard section of the right wing separating in flight. The pilot of the Glaser-Dirks was fatally injured, while the pilot of the Glasflugel was able to bail-out and deploy his parachute.
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 for the Glasflugel STD Libelle 201B from the NTSB's investigation tables, in plain English
Pilot
- Certificate: private
- Ratings: rotorcraft: glider
- Flight time: 72 hours in all; 13 in this make and model; 15 in the last 90 days; 14 in the last 30 days; 35 as pilot in command
- Last flight review: October 23, 2003
- Medical certificate: Class 2 (valid medical--w/ waivers/lim.)
- Seat: ctr
- Injury: minor injuries
The aircraft
- Airframe total time: 3,147 hours
- Last inspection: annual inspection, August 8, 2003; 14 hours since
- Maximum gross weight: 770 lb
- Seats: 1
- Landing gear: retractable
The flight
- Departed from: AWO Arlington WA at 7:20 pm
- Flight plan: none
Weather at the time
- Light: daylight
- Wind: from 310° at 8 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 54°F (12°C), dew point 36°F (2°C)
- Altimeter: 30.40 inHg
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 |
The factual record for the Glaser-Dirks DG-400 from the NTSB's investigation tables, in plain English
Pilot
- Certificate: private
- Ratings: rotorcraft: glider
- Flight time: 204 hours in all; 1 in the last 90 days; 1 in the last 30 days
- Last flight review: March 21, 2004
- Medical certificate: Class 3 (valid medical--w/ waivers/lim.)
- Seat: ctr
- Injury: fatal
The aircraft
- Maximum gross weight: 1,014 lb
- Seats: 1
- Landing gear: retractable
- Engine: Rotax 505 (piston); 0 hours total
The flight
- Departed from: AWO Arlington WA
- Flight plan: none
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 SEA04LA063.