Accident Briefs: August 2018

These are official summaries from the NTSB. They are printed in their entirety and verbatim.

Duette, Florida

Injuries: 2 Fatal

The private pilot, who had recently purchased the airplane, and the flight instructor were conducting an instructional flight in the multi-engine airplane to meet insurance requirements. Radar data for the accident flight, which occurred on the second day of 2 days of training, showed the airplane maneuvering between 1,000 ft and 1,200 ft above ground level (agl) just before the accident. The witness descriptions of the accident were consistent with the airplane transitioning from slow flight into a stall that developed into a spin from which the pilots were unable to recover before the airplane impacted terrain. Examination of the wreckage did not reveal evidence of any preexisting mechanical malfunctions or anomalies that would have precluded normal operation of the airplane.

After the first day of training, the pilot told friends and fellow pilots that the instructor provided nonstandard training that included stall practice that required emergency recoveries at low airspeed and low altitude. The instructor used techniques that were not in keeping with established flight training standards and were not what would be expected from an individual with his extensive background in general aviation flight instruction. Most critically, the instructor used two techniques that introduced unnecessary risk: increasing power before reducing the angle of attack during a stall recovery and introducing asymmetric power while recovering from a stall in a multi-engine airplane; both techniques are dangerous errors because they can lead to an airplane entering a spin. At one point during the first day of training, the airplane entered a full stall and spun before control was regained at very low altitude. The procedures performed contradicted standard practice and Federal Aviation Administration guidance; yet, despite the pilot's experience in multi-engine airplanes and in the accident airplane make and model, he chose to continue the second day of training with the instructor instead of seeking a replacement to complete the insurance check out.

The spin encountered on the accident flight likely resulted from the stall recovery errors advocated by the instructor and practiced on the prior day's flight. Unlike the previous flight, the accident flight did not have sufficient altitude for recovery because of the low altitude it was operating at, which was below the safe altitude required for stall training (one which allows recovery no lower than 3,000 ft agl).

Probable cause(s): The pilots' decision to perform flight training maneuvers at low airspeed at an altitude that was insufficient for stall recovery. Contributing to the accident was the flight instructor's inappropriate use of non-standard stall recovery techniques.

Point Mugu, California

Injuries: 1 Fatal, 1 Minor

The two pilots, who were both qualified to fly the experimental light sport airplane, were conducting a local flight with two other similar airplanes from the same flight club. After takeoff, the three airplanes proceeded to the ocean shoreline and then flew slightly offshore along the coast. The flight was conducted at a low altitude, which, once over the ocean, was about 300 ft. Soon after reaching the ocean, both pilots noted a "skip" in the engine. They decided to climb for safety and turn around to return to their departure airport. Despite moving their respective throttles to the full throttle position, neither pilot was able to obtain full power from the engine to effect a climb, and the engine rpm began slowly decreasing. Because the airplane was no longer able to maintain altitude, control of the airplane was transferred to the pilot who held a flight instructor certificate. Due to the rocky coastline and traffic on the road along that coastline, the pilots determined that they would have to ditch in the ocean. After the ditching, both pilots escaped from the airplane, and, when the airplane began to sink, they began to swim to shore, which was about 200 ft away. Neither pilot appeared injured. No personal flotation devices were aboard the airplane or worn by the pilots. One pilot successfully swam to shore, but the other pilot drowned.

The airplane washed ashore the following morning and was heavily damaged by wave action, contact with rocks, and the saltwater immersion. Postaccident examination did not reveal evidence of any pre-accident mechanical failures but obscuration or destruction of such evidence due to the ditching and subsequent environmental damage could not be ruled out.

The examination revealed several maintenance-related discrepancies. The type of fuel line clamps used and the installation of the fuel pumps were not in accordance with the engine manufacturer's specifications, and this could have affected fuel delivery to the carburetors. After the accident, the throttle cable was found disconnected from the cockpit control, and it could not be determined whether that was a result of a partial slippage during flight, which would have limited or eliminated pilot control of the engine rpm and power.

Although a similar airplane in the flight did not report any carburetor icing, the symptoms described by the surviving pilot were consistent with carburetor icing, and the ambient temperature and dew point values allowed for the possibility of carburetor icing. Despite such equipment being recommended by the engine manufacturer, the lack of carburetor heat provisions on the accident airplane prevented the pilots from being able to prevent carburetor icing, or counter carburetor icing if it did occur.

Finally, although the engine manufacturer specified an overhaul interval of 300 hours, the flight club elected to adhere to a 450-hour overhaul interval advocated by a repair facility that was not approved by the engine manufacturer. At the time of the accident, the engine was about 127 hours beyond the manufacturer-recommended 300-hour overhaul interval. Although none of these discrepancies discovered during the investigation was able to be definitively linked to the accident, all were potential factors, and all were maintenance-related.

The low glide ratio of the airplane (about 5:1) limited its range in the event of a loss of engine power, reducing the forced landing site options available to the pilots. The forced landing site options were further reduced by the pilots' decision to operate at 300 ft, a very low altitude. The pilots' over-water route and low cruise altitude were reported to be common for pilots in the flight club. Even though the altitude and route combination increased the likelihood of an ocean ditching in the event of a loss of engine power, neither the pilots nor the airplane were equipped for an ocean ditching. Precautions such as higher over-water cruise altitudes and water-ditching equipment, such as personal flotation devices, may have prevented this event from becoming a fatal accident.

Probable cause(s): A partial loss of engine power for reasons that could not be determined during the postaccident examination in combination with the low cruise altitude selected by the pilots, which resulted in an ocean ditching. The lack of personal flotation devices likely contributed to the drowning of one of the pilots.