# Accident 19960220002189A: Sukhoi SU31, Immokalee, FL, February 20, 1996

- Type: FAA accident report (Accident/Incident Data System), as reported
- Date: February 20, 1996, 11:43 local time
- Place: Immokalee, FL
- Airport: Immokalee Airport
- Damage: Destroyed
- Phase of flight: Descent
- Operating rules: General operating rules (Part 91)
- Location: 26.4481° N, 81.4019° W: Placed by OpenAirDocs from the FAA’s distance and direction from , within about a mile (OpenAirDocs)
- Nearby events: https://openairdocs.org/map.md?lat=26.4481&lon=-81.4019&mi=10
- Aircraft: N31MX, a cancelled registration (https://openairdocs.org/deregistered/N31MX-2005-02-18) (OpenAirDocs)
- Registry model: Sukhoi SU-31 (registry code 9850105, https://openairdocs.org/model/sukhoi-su-31) (OpenAirDocs)
- Reported make and model: SUKHOI SU31
- Reported engine: VEDENY M14P
- People aboard: 1
- Fatal injuries: 1
- Pilot flight hours: 16,000 total, 10 in this make and model
- NTSB investigation: [NTSB ATL96FA051](https://openairdocs.org/ntsb/ATL96FA051) (OpenAirDocs)
- FAA source: FAA Aviation Safety Information Portal (https://asip.faa.gov/)
- Page: https://openairdocs.org/incident/19960220002189A

## Narrative

As the FAA filed it, in capitals; the FAA replaces private details with ^PRIVACY DATA OMITTED^.

WING SEPARATED FROM AIRCRAFT IN FLIGHT. (.4)THE PILOT WAS CONDUCTING A PRACTICE AEROBATIC FLIGHT, WITH TWO AEROBATIC PILOTS CRITIQUING HIM FROM THE GROUND. ABOUT TEN MINUTES INTO THE FLIGHT, THE PILOT INITIATED A PULL TOWARD THE VERTICAL WITH ABOUT 360 KM/HR AND 7 GS, ACCORDING TO WITNESSES. THIS WOULD HAVE BEEN WELL WITHIN THE MAXIMUM AIRSPEED AND LOAD SPECIFICATIONS OF 450 KM/HR AND 10 GS, RESPECTIVELY. THE RIGHT WING OF THE AIRPLANE SEPARATED DURING THE PULL UP. THE AIRPLANE ENTERED A RIGHT ROLL AND AN UNCONTROLLED DESCENT, THEN IT COLLIDED WITH THE GROUND ABOUT 1 MILE NORTH OF THE AIRPORT. ACCORDING TO WITNESSES, THE ENGINE WAS DEVELOPING POWER UNTIL IMPACT, AND THE PILOT DID NOT ANNOUNCE ANY MALFUNCTIONS OR PROBLEMS, PRIOR TO THE WING FAILURE. A POSTCRASH GROUND FIRE CONSUMED THE FUSELAGE. THE UNBURNED RIGHT WING WAS FOUND ABOUT 3/4 MILE EAST OF THE MAIN WRECKAGE. TESTING OF THE WING SPAR WAS PERFORMED BY THE NTSB AND MAK (RUSSIAN INVESTIGATIVE AUTHORITIES). BOTH AGENCIES FOUND NUMEROUS VOIDS IN THE COMPOSITE SPAR CAPS. THE INVESTIGATION REVEALED EVIDENCE THAT THE CURING PROCESS FOR THE WING SPAR DID NOT PROVIDE ADEQUATE VACUUM PRESSURE. THER                                   E WAS EVIDENCE THAT DURING THE CURING PROCESS, THE FIBERS SEPARATED FROM EACH OTHER, WHICH RESULTED IN VOIDS IN THE FINAL COMPOSITE MATERIAL.

## The NTSB's investigation of this event (1)

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

- [NTSB ATL96FA051](https://openairdocs.org/ntsb/ATL96FA051), Feb 20, 1996: Sukhoi SU-31 (N31MX), Immokalee, FL, destroyed, 1 fatal. Probable cause: the manufacturer's improper composite curing process, which resulted in wing spar voids and subsequent failure of the wing during aerobatic flight.

From the FAA Accident/Incident Data System. Reports are matched to registry aircraft by N-number and event date, checked against the reported make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. For accidents, the NTSB's own investigation is the fuller record.

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