N9774UGrumman American Avn. AA-5A

**This report was modified on September 8, 2021. Please refer to the public docket for this investigation, a link to which can be found at the end of this report, to see the original.**

On September 26, 2019, about 1811 mountain daylight time, a Grumman AA-5A airplane, N9774U, was destroyed when it was involved in an accident near Cowles, New Mexico. The pilot and passenger were fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

The pilot planned to fly to Santa Fe Municipal Airport (SAF), Santa Fe, New Mexico, with a friend to accumulate flight time. Automatic dependent surveillance-broadcast (ADS-B) data showed that the airplane departed Denver, Colorado, at 0949, flew east of the Sangre de Cristo Mountains, and landed at SAF. The pilot requested fuel, and they departed on the return flight about 1745. ADS-B data showed that, after departure, the airplane completed a 180º climbing left turn to a southeasterly heading. At 1751, the airplane turned to the east for about three minutes before adjusting its course to the northeast directly toward the Sangre de Cristo Mountains. The airplane remained on this heading until the track data ceased at 1801, as shown in figure 1. The pilot was not in contact with air traffic control at the time of the accident.

Two hunters located about 13 miles south of the accident site witnessed a single-engine airplane flying north about 1800 on the day of the accident. One of them saw the airplane about 20 ft above the trees and noted that he could not hear any audible noise coming from the airplane, but the airplane was moving quickly. The other witness stated that the propeller was spinning slowly, but the airplane appeared straight and level. He could not hear the engine because he was in his vehicle with the windows rolled up.

The United States Air Force Rescue Coordination Center received an emergency locator transmitter signal from the accident airplane at 1811 on the day of the accident. A Federal Aviation Administration (FAA) alert notice (ALNOT) was issued at 2134 and the Civil Air Patrol (CAP) began a search. The wreckage was located September 28, 2019, at 1429, and the ground team did not arrive at the wreckage until the following night. The search efforts were hindered by terrain.

Figure 1. Flightpath and Topography

The pilot held a commercial pilot certificate with ratings for single-engine land, multi-engine land and instrument airplane. Additionally, he held a commercial pilot certificate for rotorcraft helicopter with a rating for instrument rotorcraft. His most recent first-class FAA medical certificate was issued on March 12, 2019, with no limitations.

The pilot's flight logbook showed combined entries for both his military and civilian flight experience from March 14, 2018, to September 13, 2019. The pilot recorded 668 total hours of flight experience; 289 hours in helicopters and 380 hours in airplanes, 198 of which were in the accident airplane make and model.

Review of the airplane’s maintenance logbooks did not reveal any major anomalies in its recent service history. According to the accident pilot's mother, the pilot informed her about an electrical issue he had experienced in the accident airplane in August 2019. According to a logbook entry dated August 28, 2019, a maintenance facility in Amarillo, Texas, removed and replaced an alternator circuit breaker fuse after the circuit breaker popped and began producing smoke during a flight. The airplane was subsequently returned to service and no further issues with the circuit breaker were recorded.

One instructor employed by the operator reported that he had flown the accident airplane and the company's other Grumman Cheetahs multiple times. He described the accident airplane make and model as a generally underpowered airplane and not one that he would take into the mountains. It was a good training airplane for one pilot and one passenger. Another instructor described similar experiences in the accident airplane make and model, noting that he would not prefer to use that make and model for flights into mountainous terrain.

The pilot's mother reported that her son had previously flown over this mountain range.

The 1753 recorded weather conditions at SAF indicated wind from 250° at 6 kts, visibility 10 miles or more, broken ceiling 10,000 ft above ground level (agl), temperature 26°C, dewpoint 1°C, and an altimeter setting of 30.05 inches of mercury. The density altitude at the time of the accident was 8,983 ft.

The winds aloft for Albuquerque, New Mexico, indicated wind from 250° at 20 kts between 9,000 ft mean sea level (msl) and 12,000 ft msl.

The National Weather Service issued an AIRMET Tango for turbulence that was current over Colorado at the time of the accident from the surface to 18,000 ft msl. No additional advisories were current over the pilot's route of flight. An atmospheric sounding showed a dry low-level environment favorable for thermals up to 2,000 ft agl, with expected cloud bases of 15,000 ft with tops near 19,000 ft. No significant turbulence, low-level wind shear, or icing conditions were identified under 15,000 ft.

The pilot did not obtain a weather briefing from an access-controlled source before the accident flight, and it could not be determined what weather information the pilot may have accessed before the flight.

Review of the airplane’s maintenance logbooks did not reveal any major anomalies in its recent service history. According to the accident pilot's mother, the pilot informed her about an electrical issue he had experienced in the accident airplane in August 2019. According to a logbook entry dated August 28, 2019, a maintenance facility in Amarillo, Texas, removed and replaced an alternator circuit breaker fuse after the circuit breaker popped and began producing smoke during a flight. The airplane was subsequently returned to service and no further issues with the circuit breaker were recorded.

One instructor employed by the operator reported that he had flown the accident airplane and the company's other Grumman Cheetahs multiple times. He described the accident airplane make and model as a generally underpowered airplane and not one that he would take into the mountains. It was a good training airplane for one pilot and one passenger. Another instructor described similar experiences in the accident airplane make and model, noting that he would not prefer to use that make and model for flights into mountainous terrain.

The pilot's mother reported that her son had previously flown over this mountain range.

The airplane was located in mountainous terrain on the slope of a narrow canyon at an elevation of about 10,300 ft msl between two rideglines that were about 12,000 ft and 12,529 ft msl. All major sections of the airplane were accounted for at the accident site. The initial impact point (IIP) was marked by a severed tree and several broken tree branches. A large portion of the left wing was bent about midspan and was collocated with the IIP. Numerous airframe and plexiglass fragments were distributed along the wreckage path, which was oriented on a heading of about 030º magnetic. The main wreckage was located about 60 ft north of the IIP and comprised the right wing and fuselage, which were both consumed by the postcrash fire. The vertical stabilizer and elevators came to rest a few feet forward of the main wreckage and were thermally damaged. Most of the engine was damaged by the postcrash fire and located several feet from the propeller assembly; both were located with the main wreckage.

The left-wing flap separated from the wing and came to rest a few feet from the IIP. The left aileron was located a few feet forward of the tail section.

The propeller blade and hub assembly remained intact, but both blades separated about mid-span. The fracture surfaces were consistent with overload separation. The longer of the blades displayed twisting about mid-span.

Due to weather restrictions, the wreckage was not recovered until about 7 months after the accident. During this time, the wreckage was exposed to several feet of accumulated snow and other environmental hazards.

A complete examination of the flight control system could not be conducted due to postcrash fire damage. The rudder and elevator control cables were continuous from the rudder bellcrank to the cockpit through cuts made by recovery personnel. Aileron control continuity was confirmed from each aileron through separations in the left-and right-wing torque tubes that displayed signatures consistent with overload.

Rotational continuity of the engine and cylinder compression were confirmed when the crankshaft was rotated by hand with a pipe wrench. Examination of internal components revealed no indications of catastrophic engine failure. Cylinder No. 2 was replaced with an overhauled cylinder about two weeks before the accident. The No. 2 cylinder piston face displayed a swirl pattern consistent with normal operation for new cylinders.

The engine accessories were mostly damaged by postcrash fire. Each spark plug electrode exhibited wear consistent with normal operation. The internal components of the magnetos and fuel pump were destroyed.

Performance

The airplane's weight and balance at the time of the accident was computed with an airplane empty weight of 1,495 lbs, combined pilot and passenger weight of 500 lbs, oil weight of 15 lbs, and a fuel weight of 228 lbs. The fuel quantity was derived from a fixed based operator at SAF who reported refueling the airplane to the "tabs" (about 38 gallons) before the accident flight. The airplane’s estimated gross weight at the time of departure was 2,238 lbs, 38 lbs over its published maximum gross takeoff weight. The airplane's estimated center of gravity was outside of the forward envelope (see figure 2).

The airplane's rate of climb was calculated using performance charts derived from the pilot’s operating handbook (POH). Using 2,100 lbs gross weight, the climb figures for SAF from its field elevation to 9,000 ft were based on 26ºC ambient temperature and climb figures from 9,000 ft to 11,000 ft were based on 13ºC ambient temperature. The calculations indicated that, under normal operating limitations (at or below maximum gross weight) the airplane required a minimum of 28 minutes to climb from the departure airport to 12,000 ft, in order to overfly the lowest terrain in the area by about 500 ft. These figures assume that the airplane’s airspeed did not exceed 75 kts indicated airspeed. The airplane is presumed to have crashed about 26 minutes after takeoff based on its airspeed and altitude profile.

As displayed in figure 3, and based on the available ADS-B track, the airplane flew relatively close to the ground as it entered the mountain range, at one point reaching about 370 ft above ground level. Data retrieved from the track also showed that it took the airplane about 5.5 minutes to climb to 450 ft.

Figure 2. Center of Gravity Envelope

Figure 3. ADS-B track

The New Mexico Office of Medical Investigators performed an autopsy of the pilot and reported the pilot's cause of death as blunt trauma and the manner of death as an accident. The autopsy identified severe atherosclerotic stenosis (90%) of the left anterior descending coronary artery. Histology demonstrated significant thermal damage to the heart muscle.

The FAA's Forensics Sciences Laboratory performed toxicology testing on the pilot's tissue samples, which did not detect any ethanol or drugs of abuse.