N9454LAmerican Aviation AA-1A · 1971

On June 9, 2014, about 1115 Pacific daylight time, an American Aviation AA-1A, N9454L, collided with the dry lakebed surface of El Mirage Lake, in El Mirage, California. The airplane was co-owned, and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91. The commercial pilot and 9-year-old passenger sustained fatal injuries. The airplane was destroyed during the accident sequence. The local personal flight departed from the El Mirage Lakebed, about 1113. Visual meteorological conditions prevailed, and no flight plan had been filed.

Members of the Los Angeles Fire Department (LAFD) had organized an off-duty recreation day at the lakebed. The group was composed of about 12 people, and included family and friends. A combination of activities was planned, including camping, along with flying both the accident airplane and powered paragliders. The accident pilot was a helicopter pilot, assigned to the air operations division of the LAFD.

About 0930, witnesses stated that the pilot departed with one of his daughters in the accident airplane to perform a sightseeing flight in the local area. The flight departed from the lakebed in a southerly direction in light and variable winds, and lasted about 15 minutes. A short time later he flew his second daughter on a similar flight, for a similar amount of time.

For the third, and accident flight, the group requested that the pilot perform a "low pass" over the north shore of the lakebed, where everyone had assembled.

According to witnesses, the flight departed again to the south, but this time the wind had increased such that a left (east) crosswind existed during takeoff. The flight progressed and the airplane approached the group from the northwest, at a low altitude for what was presumed to be the low pass. The airplane flew over the group, and after passing, initiated a climbing right turn to the south. Witnesses reported that the airplane then began a right turn to the west, and during the turn the bank angle became "excessive," with some witnesses assuming the pilot was either positioning the airplane to land, or returning for a second low-pass. The airplane did not roll level after the bank, instead the nose "tucked" down, and the airplane descended into the ground.

At the time of the accident the pilot was assigned to the Air Operations Section of the LAFD, and held the rank of Fire Helicopter Pilot II. He had been with the division for about 4 years, and over the last 2 years had completed a 200- hour advanced flight training program, and attained his type rating in the Augusta Westland AW-139 helicopter. He flew between 20 and 30 hours per month in the LAFD AW-139 and Bell 206, and was preparing for his final check ride to achieve his AW139 mission commander certification.

The pilot held a private pilot certificate with an airplane single engine land rating issued in March 2002, along with a commercial pilot certificate with a rotorcraft, helicopter rating issued in July of the same year. He received a certified flight instructor certificate with (helicopter) in June 2011, and added his helicopter instrument rating in August 2013.

The pilot's logbook indicated that as of May 2, 2014, he had a total flight time of about 1,890 flight hours, of which 1,400 were in helicopters, with the majority of the remainder in the accident airplane. According to the co-owner, the pilot had performed 3 takeoffs and landings in the airplane the week prior, but otherwise had not flown it for about 1 year, having recently purchased another airplane. His most recent flight review was accomplished on May 9, 2013.

The pilot was issued an FAA second-class medical certificate on December 17, 2013, with the limitation that he must have available lenses for near vision.

The airplane was co-owned since 2002 by the pilot and a fellow pilot at the LAFD. The co-owner held an airframe and powerplant certificate with inspection authorization, and had performed the majority of the maintenance, along with all inspections, since 1999.

The low-wing, two-seat airplane, serial number AA1A-0254, was manufactured in 1971. The airplane had originally been fitted with a 110-horsepower Lycoming O-235 engine. In June 2012, an overhauled four-cylinder 150-horsepower Lycoming O-320 engine was installed as part of the Air Mods N.W., supplemental type certificate (STC) SA4387NM.

The co-owner estimated that the accident pilot had a total of about 10 hour's flight experience in the airplane since the upgraded engine had been installed.

The airplane had undergone an annual inspection, which was completed on July 7, 2013. At that time it had accrued a total of 2,202.1 flight hours, with the engine accumulating 24.1 hours since overhaul. The airplane then flew for another 7 hours during the 11-month period leading up to the accident.

The closest aviation weather observation station was located at the Southern California Logistics Airport, Victorville, California, about 13 miles east-southeast, and about the same elevation as the accident site. An aviation routine weather report was recorded at 1115. It reported: wind from 130 degrees at 7 knots; visibility 10 miles; scattered clouds at 9,500 and 11,000 ft; temperature 37 degrees C; dew point -2 degrees C; altimeter 29.88 inches of mercury.

The next weather observation, 20 minutes later, indicated a change in wind direction and velocity to 110 degrees at 8 knots, and at 1235, the wind was reported at 120 degrees at 10 knots, gusting to 19 knots.

Local area weather reporting stations reported similar conditions, with a transition to gusting wind in the early afternoon.

The airplane was co-owned since 2002 by the pilot and a fellow pilot at the LAFD. The co-owner held an airframe and powerplant certificate with inspection authorization, and had performed the majority of the maintenance, along with all inspections, since 1999.

The low-wing, two-seat airplane, serial number AA1A-0254, was manufactured in 1971. The airplane had originally been fitted with a 110-horsepower Lycoming O-235 engine. In June 2012, an overhauled four-cylinder 150-horsepower Lycoming O-320 engine was installed as part of the Air Mods N.W., supplemental type certificate (STC) SA4387NM.

The co-owner estimated that the accident pilot had a total of about 10 hour's flight experience in the airplane since the upgraded engine had been installed.

The airplane had undergone an annual inspection, which was completed on July 7, 2013. At that time it had accrued a total of 2,202.1 flight hours, with the engine accumulating 24.1 hours since overhaul. The airplane then flew for another 7 hours during the 11-month period leading up to the accident.

The accident site was located on the western side of the lakebed, with the first identified point of impact including a series of 2-inch-deep ground disruptions. Ground scars continued 10 feet further, on a bearing of 320 degrees magnetic, and included debris consisting of green wingtip navigation lens fragments and the nose landing gear strut. The engine starter ring and alternator belt were located adjacent to the scars. The propeller, nose landing gear, shards of red wing tip navigation lens, along with the pitot tube (mounted at the left wingtip, underside) were a further 30 feet down range.

The main wreckage came to rest about 160 feet beyond the first impact point. The cabin area rested upright on a bearing of 170 degrees and sustained crush damage from the firewall through to the passenger seat bulkhead. All flight instruments had become detached from the panel. The tail section was intact, upright, and undamaged. The engine mount had separated from the airframe, with the engine remaining partially attached to the firewall via control cables and hoses.

Both wings had separated from the center spar, and remained loosely oriented perpendicular to the main cabin. The right wing was inverted, with the outboard section of the leading edge crushed at a 45-degree angle towards the trailing edge of the wing tip. The left wing came to rest leading edge up, and sustained leading edge crush damage along its entire length. The stall warning indictor was crushed at the wingtip, and the Pitot tube had become detached.

Both wing spar fuel tanks were breached, and the odor of automotive gasoline was present at the site. The magneto switch was observed in the both position; additionally, the fuel selector valve was in the right wing tank position. The throttle, and fuel mixture controls were in the full forward position. The flap actuator was set to the fully retracted flap position.

All major components of airplane were accounted for at the accident site, and the airframe was free of any indications of bird strike.

Video

The takeoff and accident sequence were captured on video by a member of the group, located about 1/2 mile north of the accident site. The video revealed that the airplane departed to the south, and began a climbing right turn to the north, leveling off parallel with the group at an altitude of about 300 ft agl. At that time a witness was recorded stating that the pilot should be performing a low pass. The airplane then transitioned to the east, while descending as it approached the camera. The descent progressed, accompanied by an increase in engine tone as the airplane started banking about 25 degrees to the right as it passed about 50 ft overhead, 80 seconds after takeoff. The turn continued with the airplane now banking 30 degrees until it leveled off on a southerly track a few seconds later. Seven seconds later the airplane began a climbing right turn to about 200 ft agl, reaching a bank angle of about 80 degrees as it passed out of the cameras view. One second later, the airplane reemerged, now in a 90-degree right bank, with the entire upper side of the fuselage visible. The nose then yawed about 20 degrees down while the airplane maintained the almost vertical right bank attitude. The airplane then began to rapidly descend, the nose dropped further, and the airplane rolled right and pitched down striking the ground in an almost vertical attitude about 18 seconds after the low pass. The engine could be heard operating throughout the recording, and no smoke or vapor trails were visible.

Weight and Balance

The engine STC SA4387NM provided for an increase in gross weight to 1,579 pounds. The airplane's basic empty weight was 1,130 pounds, and the combined weight of the pilot and passenger was about 240 pounds. The baggage compartment was loaded with about 8 pounds of equipment and tools, and according to the airplane's co-owner, prior to the first flight at the lake, the airplane's right fuel tank was full (capacity 11 usable gallons) and the left tank contained between 3 and 6 gallons.

Based on these values, the airplane would have been about 100 pounds below maximum gross weight, and the center of gravity would have been about 77 inches aft of the datum. The loading graph for the airplane indicated a center of gravity range of between 75 and 80 inches when flown under the normal category.

Performance

An accurate assessment of the airplane's airspeed throughout the flight could not be determined. According to the AA-1A Owner's Manual, the airplane's cruise speed at 65 percent power, and 8,000 ft was 119 mph. Stall speeds in the flaps up, maximum gross weight, and forward center of gravity configuration were 63 mph at 0 degrees angle of bank, and 89 mph at 60 degrees. Maximum approved positive flight load factors in the normal category with flaps up were 3.8 G's.

The FAA Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25A) described the load factors experienced by airplanes in steep coordinated turns, along with the associated changes in stall speed (Figure 4-45. Angle of bank changes load factor). Specifically, the load factor for an airplane in a 60-degree bank is 2 G's, rising to 5.76 G's in an 80-degree bank. Based on the data, the stall speed in an 80-degree banked turn would have been about 132 mph. (Figure 4-46. Load factor changes stall speed).

Spins were prohibited, and according to the Owner's Manual, in the event of an inadvertent spin, "brisk" application of spin recovery techniques are required, otherwise more than one additional turn would be needed for recovery.

An autopsy for the pilot was conducted by the San Bernardino County Sheriff's Department, Coroner Division. The cause of death was reported as the effect of multiple blunt force injuries.

Toxicological tests on specimens recovered from the pilot were performed by the FAA Civil Aerospace Medical Institute, along with the County of San Diego, Office of the Medical Examiner. The results were negative for all screened drug substances and ingested alcohol. Refer to the toxicology report included in the public docket for specific test parameters and results.

Flight Controls

All control cables for the elevator, aileron, and rudder were continuous from the control surface fittings and torque tubes through to their respective cockpit control attach points. The foot pedals and control yoke assembly sustained fragmentation and bending damage consistent with impact overload.

The rudder was still attached to the vertical stabilizer at all of its hinges, and swung freely when moved by hand.

The elevator swung freely when moved by hand, and the trim actuator was in place and moved appropriately in conjunction with movement of the elevator. The elevator trim actuator tube was continuous to forward cabin, where the trim wheel had separated from the cabin frame.

Both ailerons sustained crush damage, and remained partially attached via their hinges at their respective locations on the wing trailing edge.

The flap actuator remained attached to the center spar and torque tube. The actuator was fully retracted, which was consistent with fully retracted flaps.

Control Cable Airworthiness Directive

Airworthiness Directive (AD) 72-06-02 applicable to the AA-1A was issued in August 1974. The directive required inspection of the rudder, aileron, and elevator control cable group, along with their associated pulleys, in the area under the wing center spar. The cables and pulleys were inspected during the investigation in accordance with the AD and no defects were noted; additionally, a maintenance logbook entry from the last annual inspection indicated that AD had been complied with.

The stall warning indicator sustained impact damage, which prevented any assessment of its working condition at the time of the accident.

Engine

The engine's lower cowling area was crushed, impinging the inlet air box, crushing the right-side inlet and exhaust manifold pipes along with the muffler, and separating the carburetor bowl. The engine driven fuel pump remained attached to the crankcase, contained fuel, and was free of internal obstruction. Disassembly revealed that its internal diaphragms and seals were intact, pliable, and free of damage. All fuel fittings were tight at their respective fittings throughout the engine compartment. The engine appeared to have sustained damage limited to the ancillary components, and external examination revealed no evidence of preimpact catastrophic mechanical malfunction or fire.

The two-blade propeller had separated from the crankshaft flange and remained partially attached to the flywheel. The nose cone was crushed, and one blade had bent about 90 degrees midspan, opposite the direction of rotation. The blade exhibited leading and trailing edge nicks; the second blade was bent slightly forward but was largely undamaged.

The left and right magnetos remained securely attached at their respective mounting pads. The ignition harnesses sustained crush damage, and were secure at each magneto and spark plug. The magnetos were removed for examination; each produced a spark at the end of their respective distributor block during hand rotation. The top spark plugs were removed and examined. The electrodes remained mechanically undamaged, coated in light grey deposits, and displayed normal, short service time wear signatures when compared with the Champion Spark Plugs AV-27 Check-A-Plug chart.

The crankshaft was rotated by hand utilizing the vacuum pump output drive. The crankshaft rotated smoothly, and "thumb" compression was observed on all cylinders. Mechanical continuity was established throughout the rotating group, valve train and accessory section, and all rocker arms displayed equal amounts of lift, and were coated in clear oil.

The cylinder combustion chambers were examined utilizing a borescope. The combustion chambers appeared mechanically undamaged, and there was no evidence of foreign object ingestion or detonation. The valves were intact and undamaged, and there was no evidence of valve to piston face contact. The gas path and combustion signatures observed at the spark combustion chambers and exhaust system components displayed light grey deposits and coloration.

The oil filter was removed and cut open. The element appeared wet with clean oil, and free of debris. The oil screen was similarly free of debris.

No evidence of preimpact mechanical malfunction or failure of the engine or airframe was noted during the examination. A complete report is contained in the public docket.