Cessna 305A and Burkhart Grob G-103 TWIN II mid-air collision near Hilltown, Pennsylvania, May 1, 1999
On May 1, 1999 at about 5:34 pm local time, 2 aircraft, Cessna 305A (N5171G) and Burkhart Grob G-103 TWIN II (N47938), were involved in a mid-air collision near Hilltown, Pennsylvania (Philadelphia Glider Counc airport). 3 people were killed. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The inadequate lookout of the pilots-in-command of the glider and the towplane.
The inadequate lookout of both pilots, and the pilot of the other aircraft.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- May 1, 1999 · about 5:34 pm local time
- Place
- Hilltown, Pennsylvania · Philadelphia Glider Counc
- Type
- Accident · mid-air collision
- Injuries
- 3 people were killed.
- Weather
- visual conditions (good weather)
- Aircraft 1
- Cessna 305A · all 305As on the register
- Registration
- N5171G · no longer on the register · serial 23222
- Damage
- Destroyed
- Flight
- Flight of an unrecorded kind · general aviation rules (Part 91)
- Aircraft 2
- Burkhart Grob G-103 TWIN II G-103 TWIN · all G-103 TWIN IIs on the register
- Registration
- N47938 · no longer on the register · serial 3841-K-87
- Damage
- Destroyed
- Flight
- Instructional flight · general aviation rules (Part 91)
The NTSB's narrative for the Cessna 305A final · quoted from the NTSB record
The Cessna was in an approximate 10 degree right bank climbing turn, towing a glider. As the Cessna reached approximately 1,000 feet; the pilot (witness) of the glider being towed saw another glider, a Grob, approaching from his 11:00 position. The Grob was in an approximate 15 degree right bank descending turn. The pilot being towed believed that the Cessna and Grob were on a collision course, and he released from the tow airplane. He saw the two aircraft collide, and the Cessna spin to the ground. He did not see the Grob after impact, but saw fluttering debris. Both the Cessna and Grob were equipped with communication radios.
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 NTSB's narrative for the Burkhart Grob G-103 TWIN II final · quoted from the NTSB record
The Cessna was in an approximate 10 degree right bank climbing turn, towing a glider. As the Cessna reached approximately 1,000 feet; the pilot (witness) of the glider being towed saw another glider, a Grob, approaching from his 11:00 position. The Grob was in an approximate 15 degree right bank descending turn. The pilot being towed believed that the Cessna and Grob were on a collision course, and he released from the tow aircraft. He saw the two aircraft collide, and the Cessna spin to the ground. He did not see the Grob after impact, but saw fluttering debris. Both the Cessna and Grob were equipped with communication radios.
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 for the Cessna 305A from the NTSB's investigation tables, in plain English
Pilot
- Certificate: private
- Ratings: single-engine land; rotorcraft: glider
- Flight time: 2,300 hours in all
- Medical certificate: Class 3 (valid medical--w/ waivers/lim.)
- Seat: frt
The aircraft
- Airframe total time: 12,000 hours
- Last inspection: annual inspection, March 25, 1999; 20 hours since
- Maximum gross weight: 2,100 lb
- Seats: 2
- Landing gear: fixed
- Engine: Continental O-470-11B (piston); 0 hours total
The flight
- Departed from: 0PA0 PA at 5:27 pm
- Flight plan: none
- Runway 7, 2,600 ft by 100 ft
Weather at the time
- Light: daylight
- Wind: from 050° at 12 knots, gusting 17
- Visibility: 7 statute miles
- Sky: scat at 25,000 ft
- Temperature: 64°F (18°C), dew point 34°F (1°C)
- Altimeter: 30.00 inHg
- Observation at 5:55 pm from NXX, 10 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 |
The factual record for the Burkhart Grob G-103 TWIN II from the NTSB's investigation tables, in plain English
Pilot
- Certificate: flight instructor, commercial pilot
- Ratings: multi-engine land; single-engine land; single-engine sea; instructor: airplane single-engine; instructor: glider; instrument: airplane; rotorcraft: glider
- Flight time: 3,750 hours in all
- Medical certificate: Class 2 (valid medical--w/ waivers/lim.)
- Seat: rgt
The aircraft
- Airframe total time: 1,810 hours
- Last inspection: annual inspection, March 13, 1999; 10 hours since
- Maximum gross weight: 1,279 lb
- Seats: 2
- Landing gear: fixed
- Engine: (type not recorded); 0 hours total
The flight
- Departed from: 0PA0 PA at 5:20 pm
- Flight plan: none
- Runway 7, 2,600 ft by 100 ft
- A second pilot was aboard
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 2 |
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.
Other NTSB records under N5171G the same tail number, which may have belonged to a different aircraft at the time
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.