WPR20LA004 · Glaser Dirks DG500 TRAINER
Tucson Soaring Club Glaser Dirks DG500 TRAINER · Accident: flight control system malfunction/failure while maneuvering
From El Tiro Gliderport (AZ67) to El Tiro Gliderport (AZ67)
Event
- NTSB case
- WPR20LA004
- 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
- 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
Glaser Dirks DG500 TRAINER
- Aircraft type
- Glaser Dirks DG500
- 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
- N600TT
- Operator
- Tucson Soaring Club
- Onboard fatalities
- Unknown
- Route
- From El Tiro Gliderport (AZ67), Tucson, AZTo El Tiro Gliderport (AZ67), Tucson, AZ
- Aircraft age
- About 25 years (built 1994)
- 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 · aerobatics
- Defining eventThe 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
- Flight control system malfunction/failure
- 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
- Aircraft › Aircraft oper/perf/capability
- Aircraft › Aircraft structures
- Personnel issues › Action/decision
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The pilots were performing aerobatic maneuvers in the glider. While recovering from a maneuver, the glider’s airspeed increased past the never-exceed speed (Vne) and the elevator began to flutter. The right air brake (spoiler) deployed fully, though the spoiler control was in the locked position. After assessing the controllability of the glider, the pilots chose to land at the gliderport rather than perform an emergency egress. The glider landed hard and impacted brush, resulting in the separation of the empennage at the tailboom. Postaccident examination revealed a separation of the right-wing air brake control drive system at the rod end, which resulted in the asymmetrical spoiler extension. The manufacturer stated that it should have been possible to deploy the left-wing air brake normally to compensate for the asymmetric behavior and have some (reduced) control over the approach glidepath. The manufacturer also stated there is no emergency procedure described in the flight manual for air brake malfunctions. It is likely that the air brake control separation was the result of the pilots’ exceedance of Vne during recovery from the aerobatic maneuver.
Probable cause
The pilots’ exceedance of the glider’s never-exceed speed (VNE) during recovery from an intentional aerobatic maneuver, which resulted in a failure of the right-wing air brake control drive, asymmetrical air brake deployment, and a subsequent hard landing.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record WPR20LA004
- Event ID
- 20191007X04618
- Case number
- WPR20LA004
- Dataset
- full-current
- Source SHA-256
- 5cf380f0061817c0331a6b2d8cc7e0ee3a79bea469a1001dc5c10e56f35f5ab3
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, cause areas. 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: 20066f1720379cbfbb5b8d5e1fb9eb67dbdb90562450c6e118757e6db8eb3427; retrieved 2026-09-16T10:18:28.098Z.