Casualties unknown

Experimental Glider with Stowable Engine Strikes Tree During Forced Landing after Engine Fails to Start (N40Z)

Longmont, CO, US

On May 4, 1986, a Glaser-dirks DG-400 (registration N40Z) was involved in an aviation accident near Longmont, CO. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.

Sourcesthe U.S. National Transportation Safety Board (NTSB) historical archivePrimary reportUpdated 2026-07-04Data APIEditorial standards

An experimental glider with a stowable two-cycle engine made a forced landing after the engine failed to start when deployed, striking a tree during the landing.

Incident Overview

An experimental glider equipped with a stowable engine was involved in an accident during a return flight after a 4-hour and 50-minute flight. The pilot, needing engine power to reach the airport, deployed the engine, but it would not start. This necessitated an off-airport forced landing, during which the aircraft struck a tree.

Aircraft Details

The aircraft is an experimental glider with a stowable two-cycle engine mounted behind the cockpit. When the engine is stowed, the glide ratio is approximately 40:1. When the engine is deployed but not running, the glide ratio reduces to about 10:1.

Flight and Engine Deployment

The pilot had been flying for 4 hours and 50 minutes and decided that engine power would be required to reach the airport. Upon deploying the engine, it failed to start. The pilot then executed a forced landing off the airport, and the aircraft hit a tree during the landing.

Frequently asked questions

What happened in the 4 May 1986 Glaser-dirks DG-400 accident near Longmont, CO?

An experimental glider with a stowable two-cycle engine made a forced landing after the engine failed to start when deployed, striking a tree during the landing.

What aircraft was involved and where did it happen?

The accident on 4 May 1986 involved a Glaser-dirks DG-400, registration N40Z, at Longmont, CO.

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001213X33532. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.