History of Flight
On August 27, 2015, at 1206 Pacific daylight time, a Piper PA-25-260, registered as N4369Y, impacted terrain during the landing approach to Crystal Airport in Llano, California. The pilot, an airline transport pilot, sustained fatal injuries and the airplane incurred substantial damage. The aircraft was owned and operated by Southern California Soaring Academy (SCSA), Inc., under 14 Code of Federal Regulations Part 91 as a glider tow operation. Visual meteorological conditions prevailed at the time, and no flight plan had been filed. The flight departed at 1150.
Glider tow operations had commenced at 1025 that day, with 19 flights planned. The accident pilot was scheduled to fly until early afternoon. The procedure for glider traffic required right downwind arrivals for runway 25, with the tow plane landing on a parallel gravel surface adjacent to runway 7 using a right downwind approach for runway 7. The pilot had completed six uneventful launches before the accident, with turnaround times of about 15 minutes. After the sixth launch, the aircraft was refueled with 26 gallons.
For the accident flight, the tow plane and a glider departed, headed south of the airport, and released near the "Second Ridge" in the San Gabriel Mountain foothills. The pilot then flew back to the airport. Multiple witnesses heard the pilot announce on the common traffic advisory frequency that he was entering the right traffic pattern for runway 7. Meanwhile, a glider was approaching from the north for runway 25. The glider pilot landed, and during rollout, he noticed the tow plane north of the airport in a steep 70–80° right bank, then crossing the runway centerline from north to south and descending below trees.
Another witness saw the airplane descend below power lines, then initiate a rapid climb, roll inverted, roll back, and strike the ground nose down. The wreckage was found 900 ft southwest of the threshold of the gravel portion of runway 7.
Personnel Information
The 67-year-old pilot had an extensive background in military and civilian aviation, including experience as an experimental test pilot from the Naval Test Pilot School. He held an airline transport pilot certificate with multiple ratings and a flight instructor certificate. He reported 13,500 total flight hours at his last FAA medical examination six days before the accident. According to SCSA records, he had accumulated 90.8 flight hours in the PA-25, including 424 tows, between July 2013 and June 2015.
Aircraft Information
The single-seat, tailwheel-equipped Piper PA-25-260 was manufactured in 1969. It had accrued 11,789 total flight hours as of its last annual inspection on September 7, 2014. The engine was a six-cylinder Lycoming O-540-G1A5, manufactured in January 2013.
Meteorological Information
At 1153, the automated weather station at Palmdale USAF Plant 42 Airport, 15 miles northwest and 877 ft below the accident site, reported wind from 340° at 5 knots, 10 miles visibility, temperature 94°F, dew point 37°F, and altimeter 30.10 inHg. The temperature rose to 97°F one hour later. Immediately after the accident, the SCSA General Manager recorded a temperature of 94°F with a 4-knot wind from the west.
Wreckage and Impact Information
The cabin sustained crush damage from the firewall to the forward legs of the pilot's seat, while the aft fuselage and empennage had minimal damage. Both wings remained attached; the left wing leading edge twisted upward and sustained aft crush damage along its length; the right wing had leading edge crush damage outboard of the lift strut attachments. The engine was partially attached and shifted downward and right. One propeller blade had a forward 5° bend midspan; the other had chordwise scratches and leading edge nicks. The fuel tank bladder was breached and empty, but the soil under the engine was soaked with a liquid smelling like aviation gasoline.
Additional Information
The pilot had driven from San Diego the night before and slept at the SCSA clubhouse. A club member saw him watching a football game; by sunset the lights were out. An empty water bottle, typical of bottles given to tow pilots during refueling, was found in the wreckage.
Medical and Pathological Information
An autopsy determined the cause of death as multiple blunt force injuries. Hypertrophic heart disease was identified, with a heart weight of 530 grams. The heart was described as somewhat globular with mildly floppy myocardium. No significant coronary artery stenosis was found. The pilot had longstanding high blood pressure treated with lisinopril. A 2013 cardiac evaluation for a VA driver role included an initial stress test stopped early due to shortness of breath and ST depression; a follow-up nuclear stress test showed no anomalies. The pilot's wife reported an episode of dizziness and odd feeling while hiking about a year before the accident. At his last FAA medical, he reported high blood pressure and use of lisinopril and minocycline; he was 71 inches tall and weighed 238 lbs. He was issued a second-class medical certificate with corrective lenses limitation. No heart or vascular trouble was reported at that time. Toxicology tests were negative for carbon monoxide, screened drugs, and alcohol. An NTSB Medical Officer concurred that autopsy results were consistent with hypertrophic cardiomyopathy.
Tests and Research
Security camera footage from two cameras on the airport administration building captured parts of the tow operations. The accident approach showed the tow plane at lower altitude than previous flights, overshooting the runway centerline, initiating a climbing right turn, and then returning across the centerline in a 60° right bank before disappearing. Camera 4 captured the last 9 seconds, showing a climb or left turn, then a dust plume. The aircraft overshot the runway centerline by ¼ mile north, then overshot again south, colliding about 600 ft south. Flight tests using another PA-25 showed that standard patterns kept the airplane above the camera's field of view. GPS data indicated the tow plane was descending from about 500 ft agl while in view. SCSA procedures required a minimum 200 ft clearance above power lines at the approach end.
Postaccident examination of the airframe and engine revealed no anomalies. The JPI EDM-700 engine monitor data showed similar trends across all flights that day.