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Accidents · NTSB WPR11FA392 · Final report

Briegleb BG-12B accident near Moore, Idaho, August 18, 2011

On August 18, 2011 at about 10:40 pm local time, a Briegleb BG-12B (glider), an amateur-built aircraft,, registered N559Y, was substantially damaged in an accident during approach near Moore, Idaho (King Mountain airport). It was a personal flight under general aviation rules (Part 91). 1 person was killed. The weather was visual conditions (good weather).

The NTSB's probable cause their words, unchanged

The pilot’s decision to perform a low pass over the runway in the opposite direction of his intended landing, and his subsequent failure to maintain airspeed and glider control during the reverse-course maneuver. Contributing to the accident was the effect of the pilot's failure to take his prescribed medications.

Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.

What the record shows

Date
August 18, 2011 · about 10:40 pm local time
Place
Moore, Idaho · King Mountain · map
Type
Accident
Injuries
1 person was killed.
Weather
visual conditions (good weather)
Aircraft
Briegleb BG-12B, amateur-built
Registration
N559Y · no longer on the register · serial HFT1
Damage
Substantial damage
Flight
Personal flight · general aviation rules (Part 91)

The NTSB's narrative final · quoted from the NTSB record

The pilot of the experimental amateur-built glider was returning to land after a 2-hour flight. Witnesses located on the airfield were startled as the glider flew inbound with a tailwind 75 feet over the runway at a high speed. The glider then began a smooth pitch up and a wingover-type maneuver in a presumed effort to return for landing. During the maneuver, the glider stalled and spun to the ground. The pilot had arrived at the airfield earlier in the week for a fly-in, and had flown the glider uneventfully twice since arriving. Witnesses, who were also friends of the pilot, expressed astonishment that he performed the low pass and wingover maneuver, stating that such a flamboyant maneuver was completely out of character. The pilot purchased the vintage glider about 4 years before the accident, and the fly-in was the first time he had flown it. He held a commercial pilot certificate for gliders and powered airplanes, and had accumulated extensive experience flying hang gliders and paragliders. Additionally, he owned a modern glider, which would have had markedly different performance characteristics than the accident glider. Although the most recent condition inspection had been performed on the glider 4 years before the accident, examination of the wreckage did not reveal any anomalies with the airframe that would have precluded normal operation. About 2 years before the accident (and after his most recent FAA medical certificate application), the pilot’s personal physician described signs of depression, including mood swings, elevated mood, compulsive behaviors, obsessive thoughts, and poor insight. As such, he prescribed medication to control these conditions, as well as medication for hypertension, which had been diagnosed previously. About 6 months before the accident, the pilot was also diagnosed with and prescribed medication for hyperlipidemia; he was still under treatment for prior diagnosed conditions. At that time the physician noted that his depression was under “fair control.” However, postmortem toxicological analysis revealed that he had not been taking any of his prescribed medications at the time of the accident. As such, it is possible that he was experiencing symptoms of his medical conditions, including compulsive behavior, at the time of the accident. Although the pilot’s judgment could have been affected by the symptoms of hypoxia or dehydration, it was not possible to determine if he was experiencing these conditions.

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 from the NTSB's investigation tables, in plain English

What happened, in order

  1. Abrupt maneuver during approach defining event
  2. Loss of control in flight during landing
  3. Aerodynamic stall/spin during landing
  4. Collision with terrain or object (not controlled flight into terrain) during uncontrolled descent

The NTSB's findings

  • cause Aircraft › Aircraft oper/perf/capability › Performance/control parameters › Airspeed › Not attained/maintained
  • cause Aircraft › Aircraft oper/perf/capability › Performance/control parameters › Directional control › Not attained/maintained
  • cause Personnel issues › Task performance › Use of equip/info › Aircraft control › Pilot
  • cause Personnel issues › Action/decision › Info processing/decision › Decision making/judgment › Pilot
  • factor Personnel issues › Physical › Impairment/incapacitation › Prescription medication › Pilot
  • Personnel issues › Experience/knowledge › Experience/qualifications › Total experience w/ equipment › Pilot

Pilot

  • Certificate: commercial pilot
  • Ratings: multi-engine land; single-engine land; instrument: airplane; rotorcraft: glider
  • Flight time: 4,267 hours in all
  • Medical certificate: Class 2 (with waivers/limitations)
  • Seat: sngl
  • Injury: fatal

The aircraft

  • Airframe total time: 290 hours
  • Last inspection: condition inspection, March 7, 2007; 286 hours since
  • Maximum gross weight: 900 lb
  • Seats: 1
  • Landing gear: retractable

The flight

  • Departed from: ID36 Moore ID at 10:36 pm
  • Destination: ID36 Moore ID
  • Flight plan: none
  • Runway 16, 3,900 ft by 120 ft

Weather at the time

  • Light: daylight
  • Wind: from 200° at 8 knots, gusting 12
  • Visibility: 10 statute miles
  • Sky: clear
  • Temperature: 82°F (28°C), dew point 36°F (2°C)
  • Altimeter: 30.07 inHg
  • Observation at 10:47 pm from KSUN, 51 miles away

Injuries

FatalSeriousMinorNone
Flight crew1

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.

Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.