Sukhoi SU-31 N31MX

Summary

On 20 February 1996 at about 16:43 local time, a Sukhoi SU-31 registered N31MX was involved in an accident near Immokalee, Florida, United States. One person was on board and one died. The aircraft was destroyed. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

20 February 1996 at 16:43

Classification

Accident

Location

Immokalee, Florida, United States

Nearest airport

Immokalee (IMM)

Coordinates

Not recorded

Aircraft

Sukhoi SU-31

Registration

N31MX

Category

Airplane

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Unknown

Phase of flight

Not recorded

Aircraft damage

Destroyed

Weather

VMC

Light

Day

NTSB number

ATL96FA051

1 person died.

the manufacturer's improper composite curing process, which resulted in wing spar voids and subsequent failure of the wing during aerobatic flight.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

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. There was evidence that during the curing process, the fibers separated from each other, which resulted in voids in the final composite material.

Quoted verbatim from the NTSB record.