Pilatus B4-PC11 accident near Sterling, Massachusetts, May 20, 2021
On May 20, 2021 at about 8:00 pm local time, a 1976 Pilatus B4-PC11 (glider), registered N65317, was substantially damaged in an accident during approach (VFR pattern final) near Sterling, Massachusetts (Sterling airport). It was a personal flight under general aviation rules (Part 91). 1 person had minor injuries. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The pilot’s misjudged approach angle which resulted in impact with trees and terrain.
Source: NTSB aviation accident database, copy made October 4, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- May 20, 2021 · about 8:00 pm local time
- Place
- Sterling, Massachusetts · Sterling · map
- Type
- Accident
- Injuries
- 1 person had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft
- Pilatus B4-PC11, built 1976 · all B4-PC11s on the register
- Registration
- N65317 · registry record · serial 190
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The pilot reported that once on final approach for the runway, he miscalculated his approach angle and found the glider low on altitude and airspeed. The glider then struck trees on the edge of the airport and impacted on the airport surface resulting in substantial damage to the fuselage. The pilot reported no mechanical malfunctions or anomalies that would have precluded normal operation.
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
- Controlled flight into terrain or object (CFIT) during approach (VFR pattern final) defining event
- Miscellaneous/other during approach (VFR pattern final)
The NTSB's findings
- Personnel issues › Task performance › Use of equip/info › Aircraft control › Pilot
- Personnel issues › Action/decision › Info processing/decision › Identification/recognition › Pilot
- Aircraft › Aircraft oper/perf/capability › Performance/control parameters › Descent/approach/glide path › Not attained/maintained
Pilot
- Certificate: private
- Ratings: single-engine land; rotorcraft: glider
- Flight time: 250 hours in all; 2 in this make and model; 5 in the last 90 days; 4 in the last 30 days; 150 as pilot in command
- Last flight review: April 12, 2021
- Medical certificate: Class 3 (with waivers/limitations)
- Seat: sngl
- Injury: minor injuries
The aircraft
- Airframe total time: 3,589 hours
- Last inspection: annual inspection, May 2, 2021
- Maximum gross weight: 770 lb
- Seats: 1
- Landing gear: fixed
- Operator: Greater Boston Soaring Club INC
The flight
- Flight plan: none
- Runway 16, 3,086 ft by 40 ft
Weather at the time
- Light: daylight
- Wind: from 130° at 6 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 81°F (27°C), dew point 32°F (0°C)
- Altimeter: 30.44 inHg
- Observation at 3:52 pm from KFIT, 8 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 |
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.
About this page
Everything above comes from the NTSB's public accident database: the narrative, probable cause and findings are the NTSB's own words, and the coded tables behind its report (pilot, aircraft, flight, weather, injuries, sequence of events) are written out in plain English. Pilots' ages, home towns and medical details are left out on purpose. The documents and photographs are the NTSB's docket, the folder of records gathered during the investigation, shown as the NTSB released them (the NTSB redacts some personal details first) and listed under the NTSB's own titles. This site's own text never names pilots, passengers or anyone else involved. A preliminary report describes what is known soon after the event and can change; the final report, with the probable cause, usually follows one to two years later and this page is refreshed when it does. Case number ERA21LA266.