Cause of Aero Vodochody L-39 Air Crash in Tracy, CALIFORNIA, USA on 5/30/2003





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Final Report on Probabable Cause of Crash

HISTORY OF FLIGHT

On May 30, 2003, at 1914 Pacific daylight time, an Aero Vodochody L-39C Albatros, N139RH, collided with terrain while performing team aerobatic maneuvers in the vicinity of Tracy, California. The airplane was operated by Redstar Air Shows, Inc., under the provisions of 14 CFR Part 91. The pilot was fatally injured and the airplane was destroyed. Visual meteorological conditions prevailed and a visual flight plan had not been filed. The flight originated at Byron, California, about 1655.

A flight of three Aero Vodochody L-39's were practicing low level team aerobatics in a designated box area in the vicinity of Tracy, California. The team's aerobatic coach said that the hard deck for this practice session was 1,000 feet. The majority of the witnesses reported that the airplane appeared to "rock" and the nose pitched down on the backside of a low altitude loop just before it impacted the ground. The pilot did not appear to attempt to eject from the airplane.

PERSONNEL INFORMATION

The pilot held an Airline Transport Pilot Certificate with single engine land, multiengine land, and instrument airplane ratings. She had type ratings in the Boeing 737, DC-9, and DHC-7. The Pilot/Operator Aircraft Accident Report (NTSB Form 6120) submitted by the operator indicated the pilot had about 14,000 hours of total flight time, 10,000 hours in multiengine airplanes, 4,000 hours in single engine airplanes and 16 hours in the L-39. The date of her last biennial flight review was in January, 2003. She held a first class medical certificate dated December 20, 2002, with no limitations or restrictions.

The team's aerobatic coach told the Safety Board Investigator-in-Charge (IIC) that the pilot had extensive aerobatic experience and that she had owned a number of aerobatic airplanes including a Pitts Special and Cap232. She did not participate in competitive aerobatics. She had been a US Navy pilot for 4 years with flight time in the A-4 Skyhawk as an aggressor pilot. Federal Aviation Administration (FAA) records show she obtained her commercial pilot certificate in December, 1977, through military competency. Her check out in the L-39 was the first time flying a single engine high performance jet since flying the A-4. Aircraft logbooks recorded her as flying this L-39 nine times within the last 20 days accumulating about 5.7 hours of flight time.


AIRCRAFT INFORMATION

The tandem seat jet airplane was powered by a single 3,792 pound thrust, Motor Sich, AI-25L, turbojet engine. The airplane and engine underwent it last FSDO-approved L-39 required inspection on March 24, 2003, at a total aircraft time of 1,224 hours. The engine had a total time of 1,157 hours with 407 hours since last overhaul.

The airplane was manufactured by Aero-Vodochody of Czechoslovakia and categorized by the FAA as experimental with operational limitations of an exhibition-group II aircraft.

WRECKAGE AND IMPACT INFORMATION

The wreckage was located about a half of mile west of the New Jerusalem Airport, California, in a freshly plowed field.

Two distinct sections of wreckage were identified. An approximately 5 foot deep impression area of disturbed earth embedded with metal fragments, plexiglass shards, and black discolored cratered earth surface. A long thin earth impression extended outward from the crater area and at end of this impression the pitot tube was embedded into the ground at about a 60 degree angle. Immediately surrounding this disturbed area were pieces of metal, landing gear, and wire bundles. Debris fanned out from this point in a cone shape about 100 yards to the southeast. About 70 feet to the south was the second area of wreckage, which consisted of the tail section containing the engine.

MEDICAL AND PATHOLOGICAL INFORMATION

The Sheriff-Coroner of San Joaquin County conducted an autopsy on the pilot. According to the coroners report the pilot died of multiple blunt force injuries.

A toxicology test for ethanol and drugs were negative.

A review of the FAA medical records revealed no abnormal medical findings, limitations, or waivers throughout the history of the pilot.

FIRE

Witnesses reported a post impact fire. Large sections of the wreckage exhibited areas of black soot, ash, and thermal damage. Fire crews arrived on scene and extinguished the wreckage fire.

TESTS AND RESEARCH

The wreckage was relocated to Plain Parts in Sacramento and examined by the FAA and Safety Board investigators.

All flight control bell cranks, carry-thru bell cranks, control linkages, rods and rod ends were identified as being present within the wreckage. None of these components showed signs of preimpact failure or corrosion.

The pilots ejection seat was examined. The rocket pack had not been fired. The pilots ejection seat handle was found close to the pilots body. The rocket pack activation lanyard was found severed. The rod used to push the seat out of the cockpit was extended. The canopy latch was in the middle position. The drogue chute was fired and partially extended. The aft ejection seat was examined, found to be pinned, and the firing primers were not activated.

All the compressor blades on the first stage of the engine compressor were sheared off at their bases. Blades in the additional compressor sections were bent in the clockwise direction.

ADDITIONAL INFORMATION

Witnesses

Five of the seven witnesses interviewed clearly described the airplane as being in the last half of a loop when the airplane collided with the ground and that it did not appear that the pilot attempted to eject from the airplane. An initial statement taken by the San Joaquin Sheriff from the team aerobatic coach on scene clearly states that the pilots airplane was on the back half of a loop when the airplane appeared to rock and the nose drop towards the ground prior to impact.

The operator and team aerobatic coach stated in the Pilot Operator Accident Report (NTSB Form 6120) that the airplane was doing a series of level aileron rolls at 1,500 feet when the plane leveled off and started a gradual left descending turn until impact with the ground.

Loop Maneuver

A loop is a 360 degree turn done in the vertical plane. Executing a loop will normally subject the pilot to +3 g's or more when entering or exiting the maneuver.

Aileron Roll Maneuver

An aileron roll is the rolling of the airplane about the longitudinal axis using coordinated control inputs. The ailerons are the primary controls for this maneuver. The maneuver typically will subject the pilot to +1 g throughout the maneuver.

G Induced Loss of Consciousness (GLOC)

The average threshold of a pilot to blackout is 4.7 g's and laps in to unconsciousness at 5.4 g's. The rate of g on-load is a significant factor in establishing the amount of g load a pilot can withstand (AC-91-61).

Initial Report

The single engine, two seat, jet airplane impacted the ground while pulling out of a low level loop. The airplane was practicing low level team aerobatics with two other similar jet airplanes. The established hard deck for the practice was 1,000 feet. The lead jet entered a loop maneuver at about 1,500 feet and impacted the ground while pulling out at the bottom of the maneuver. During the end of the maneuver the wings rocked and the nose pitched down. Examination of the ejection seat mechanism disclosed no evidence that the pilot attempted to eject from the airplane. No evidence of a control system malfunction was found and the damage to the engine was consistent with it developing significant power at ground impact.
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2003 - Aero Vodochody CALIFORNIA

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