SEA04LA063 · Glasflugel STD Libelle 201B
Glasflugel STD Libelle 201B and Glaser-Dirks DG-400 · Accident: midair collision while maneuvering
Event
- NTSB case
- SEA04LA063
- 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
- 1 · all aircraft and ground
- Ground fatalities
- Unknown
- 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
Aircraft 1 · Glasflugel STD Libelle 201B
- Aircraft type
- Glasflugel STD LIBELLE 201B
- Category
- Glider
- 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
- N161D
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From Arlington Municipal Airport (AWO), Arlington, WATo 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
- Maneuvering
- 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
- Midair collision
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Substantial
Aircraft 2 · Glaser-Dirks DG-400
- Aircraft type
- Glaser Dirks DG-400
- Category
- Glider
- 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
- N400WJ
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From Arlington Municipal Airport (AWO), Arlington, WATo 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
- Maneuvering
- 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
- Midair collision
- 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
- Pilot in command › Clearance, not maintained
- Pilot of other aircraft › Clearance, not maintained
Approximate · Coordinates from the NTSB case API, which marks them as estimated or does not say; no uncertainty radius is established.
NTSB narrative
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.
Probable cause
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.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record SEA04LA063
- Event ID
- 20040414X00461
- Case number
- SEA04LA063
- 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: local date, investigation status, coordinates. Values present in the bulk record are kept.
- The date is the local date; the NTSB stores the UTC date 2004-04-02.
- API snapshot SHA-256: c5cc2b1361bbe13b9e38e9036b3b11bca15170a5a89fd24614bec3ea3915745d; retrieved 2026-09-20T18:30:52.156Z.