Socata TB-9C accident near Cahokia, Illinois, March 18, 1999
On March 18, 1999 at about 9:18 pm local time, a Socata TB-9C, registered N508PC, was substantially damaged in an accident near Cahokia, Illinois (St. Louis Downtown Parks airport). It was an instructional flight under general aviation rules (Part 91). 1 person was seriously injured and 1 person had minor injuries. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
the in-flight loss of control by the student pilot due to wind turbulence. Additional causes were the flight instructor's inadequate supervision of the flight and the flight instructor's decision to continue the touch and go after encountering turbulence on the vfr final approach that had required the flight instructor's intervention to correct.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- March 18, 1999 · about 9:18 pm local time
- Place
- Cahokia, Illinois · St. Louis Downtown Parks · map
- Type
- Accident
- Injuries
- 1 person was seriously injured and 1 person had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft
- Socata TB-9C · all TB-9Cs on the register
- Registration
- N508PC · no longer on the register · serial 1477
- Damage
- Substantial damage
- Flight
- Instructional flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The dual student reported that during final approach to runway 30R, the airplane encountered, 'somewhat severe turbulence'. The dual student stated that, '...the turbulence was severe enough to require the assistance of his instructor...to recover from the turbulence encounter.' The dual student reported that upon completion of the landing and subsequent takeoff, '...they again encountered turbulence on takeoff and the airplane began a rolling maneuver until impact.' Reported winds taken immediately after the accident were wind from 320 degrees at 11 knots gusting to 18 knots. Prior to and during the time of the accident a United States Army Chinook helicopter was operating upwind and parallel to the active runway. A transcript of the voice communications between aircraft and Federal Aviation Administration (FAA) Air Traffic Control (ATC) did not disclose any wake turbulence cautionary advisory or hazardous condition advisory transmissions given by the local controller to any aircraft. Research revealed that rotor wake turbulence, generated by the Army helicopter, had the potential to drift across the runway and the final approach course. A 1996 FAA study, entitled 'Flight Test Investigation of Rotorcraft Wake Vortices in Forward Flight', recommended that ATC separation standards should exist between heavy helicopters and small fixed-wing aircraft to prevent rotor wake turbulence encounters.
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
Pilot
- Certificate: flight instructor, commercial pilot
- Ratings: single-engine land; instructor: airplane single-engine; instrument: airplane
- Flight time: 440 hours in all; 225 in this make and model; 90 in the last 90 days; 36 in the last 30 days; 325 as pilot in command; 90 on instruments
- Medical certificate: Class 1 (valid medical--w/ waivers/lim.)
- Seat: rgt
The aircraft
- Airframe total time: 2,413 hours
- Last inspection: annual inspection, March 17, 1999; 2 hours since
- Maximum gross weight: 2,335 lb
- Seats: 4
- Landing gear: fixed
- Engine: Lycoming O-320-D2A (piston); 0 hours total
The flight
- Departed from: CPS
- Flight plan: none
- Runway 30R, 3,800 ft by 75 ft
- A second pilot was aboard
Weather at the time
- Light: daylight
- Wind: from 320° at 11 knots, gusting 18
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 55°F (13°C), dew point 25°F (-4°C)
- Altimeter: 30.00 inHg
- Observation at 9:18 pm from CPS
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 | 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.
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.