# NTSB DEN93LA080: Glasflugel Standard Libell, N4362, Boulder, CO, July 16, 1993

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Limited investigation · Final report
- Date: July 16, 1993, 13:30 local (19:30 UTC)
- Place: Boulder, CO
- Coordinates: 40.019802, -105.24945 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=40.0198&lon=-105.2494&mi=10
- Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 1 minor
- Status: Completed, report June 30, 1994
- Report: Approved by Office Director
- NTSB case key (mKey): 11095
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN93LA080
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/11095/pdf
- Page: https://openairdocs.org/ntsb/DEN93LA080

## Probable cause

IMPROPER RIGGING OF THE SPOILER SYSTEM BY MAINTENANCE  PERSONNEL, WHICH CAUSED AN UNCOMMANDED SPOILER DEPLOYMENT AND PREVENTED SPOILER RETRACTION BY THE PILOT.  A FACTOR WAS UNSUITABLE TERRAIN FOR A FORCED LANDING

## Analysis

ACCORDING TO THE PILOT, DURING INITIAL CLIMB FOLLOWING TAKEOFF, WHILE UNDER TOW ON A GLIDER FLIGHT, THE SPOILERS DEPLOYED AND COULD NOT BE RETRACTED. THE PILOT RELEASED FROM THE TOW AND ATTEMPTED TO RETURN TO THE AIRPORT. THE GLIDER IMPACTED IN A FIELD APPROXIMATELY 1/2 MILE SHORT OF THE RUNWAY. THE PILOT STATED THAT THE SPOILERS HAD BEEN MISRIGGED.

## Factual narrative

On July 16, 1993, at 1330 mountain daylight time, a Glasfugel Standard Libell glider, N4362, impacted the ground near the Boulder, Colorado, Airport.  The pilot received minor injuries and the glider sustained substantial damage.  Visual meteorological conditions prevailed for this personal flight which originated at the Boulder Airport.

According to the pilot, the spoilers deployed during takeoff and could not be retracted due to improper rigging.  The pilot said he released from the tow and attempted to return to the airport.  The aircraft impacted in a field across the street from the landing area.

The wings had been removed prior to examination of the aircraft and verification of spoiler rigging could not be conducted.

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Airframe/component/system failure/malfunction, takeoff - initial climb
  - flt control syst,wing spoiler system - deployed inadvertently
  - spoiler retraction - not possible, pilot in command
  - maintenance,installation - improper, unknown (cause)
- Altitude deviation,uncontrolled, takeoff - initial climb
- Forced landing, descent - emergency
  - terrain condition - none suitable (contributing factor)

## Aircraft

- Registration: [N4362](https://openairdocs.org/aircraft/N4362), registered now, S/N 216, built 1971 (OpenAirDocs)
- Reported make and model: GLASFLUGEL STANDARD LIBELL (STANDARD L)
- Registry model: [Glasflugel STANDARD LIBELLE](https://openairdocs.org/model/glasflugel-standard-libelle) (registry code 3800341) (OpenAirDocs)
- Registry engine: [NONE](https://openairdocs.org/engine/none) (registry code 00000, none) (OpenAirDocs)
- Category: Glider
- Serial number: 216
- Engines: unknown
- Damage: Substantial damage
- Flight: Personal, Part 91
- Registered owner: Valas, Harry R.
- Airworthiness certificate: Standard, Normal
- Last inspection: Annual, April 16, 1993

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 66; private; airplane ratings: single-engine land; seat: center; flight hours: 372 total

## Weather

- Conditions: Visual (VMC), Day
- Wind: 10° at 6 knots
- Visibility: 75 statute miles
- Lowest ceiling: 20,000 ft broken
- Temperature: 84 °F, dew point 57 °F
- Altimeter: 29.00 inHg
- Observed at: BJC, 10 nm away

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Accident 19930716024229A](https://openairdocs.org/incident/19930716024229A), Jul 16, 1993: Glasfl LIBELLE, Boulder, CO, Substantial damage. Gliders spoilers deployed under tow unable to retract released from tow. Impacted field. Spoilers were misrigged.

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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