HISTORY OF FLIGHTOn November 16, 2018, about 1546 mountain standard time, an experimental, amateur-built Zenith Zodiac 601XL airplane, N322JL, was substantially damaged when it was involved in an accident near Overgaard, Arizona. The pilot and pilot-rated passenger were fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. According to a family member, the pilot and his son had planned a multileg flight from Fullerton Municipal Airport (FUL), Fullerton, California, to Orange Port, Florida. On the morning of the accident, they departed FUL and flew to Lake Havasu City Airport (HII), Lake Havasu City, Arizona. After landing at HII and refueling, they departed and were planning to stop at Mogollon Airpark (AZ82), Overgaard, Arizona, for the night, where the pilot owned a hangar. The family member stated that the pilot had flown into AZ82 in the past. Flight data shows the airplane’s turn onto the final approach to AZ82. (See figures 1 and 2.) While on runway heading, about 1/2 mile from the approach end of runway 21, the airplane was about 100 ft above ground level at an airspeed of about 62 kts. The remaining flight data showed the airplane track low, with airspeed increasing to about 70 kts. The last two targets of the flight track showed a slight right turn ending near the accident site. Several witnesses in the area stated that they heard a loud thud or felt a vibration about the time of the accident. The wreckage was identified by nearby homeowners about 1 hour after the accident between residential hangars near the approach end of the runway. Figure 1-Flight track data and accident site location. Figure 2-Runway approach end and flight track data. AIRCRAFT INFORMATIONThe airplane is a kit airplane series, optimized for sport-pilot and light-sport categories. The airplane’s published stall speed with the flaps down is about 38 kts (44 mph) and its optimum published best glide speed is about 65 kts (74 mph). METEOROLOGICAL INFORMATIONA privately owned weather station near the approach end of runway 21 recorded peak wind at 6 kts from the south about the time of the accident. AIRPORT INFORMATIONThe airplane is a kit airplane series, optimized for sport-pilot and light-sport categories. The airplane’s published stall speed with the flaps down is about 38 kts (44 mph) and its optimum published best glide speed is about 65 kts (74 mph). WRECKAGE AND IMPACT INFORMATIONExamination of the accident site revealed the first identified point of contact (FIPC) was the top of an 80-ft-tall tree on the direct centerline view of runway 21 and about 1,500 ft from the runway threshold. A broken tree limb and a wingtip light assembly were found near the FIPC. About 226 ft from the FIPC, a wing impact mark and cuts consistent with rotating propeller blades were found on the roof of a house. (See figures 3 and 4). A propeller blade was found in several sections about 170 ft from the house. The airplane then impacted a second tree before impacting the ground in the taxi area between house. The empennage separated from the main wreckage and remained lodged in the second tree about 20 ft above the ground. The main wreckage was found inverted with leading-edge impact damage to the right wing and buckling to both wings. The fuselage was twisted, and the engine remained partially attached. Fuel was drained from the right wing during the recovery of the wreckage. A postaccident examination of the airframe and engine revealed no evidence of preimpact mechanical malfunctions or failures that would have precluded normal operation. Figure 3-Right wing impact marks and runway location. Figure 4-Propeller strike marks and main wreckage. ADDITIONAL INFORMATIONThe Federal Aviation Administration Pilot’s Handbook of Aeronautical Knowledge (FAA-H-8083-25B), chapter 17, Aeromedical Factors, indicates the following: An upsloping runway, upsloping terrain, or both can create an illusion that the aircraft is at a higher altitude than it actually is…. (See Figure 5) The pilot who does not recognize this illusion will fly a lower approach. Downsloping runways and downsloping approach terrain can have the opposite effect. Figure 5-FAA Airplane Flying handbook figure. TESTS AND RESEARCHDuring the investigation, three low approaches were flown into AZ82 to mimic the accident flight. The VAPI was visible to the left of the runway threshold. An airplane performance study was conducted and revealed that the airplane initially intercepted the runway heading slightly above the 3° glide slope. It then increased its rate of descent and descended below the 3° glide slope. About 3,000 ft from the displaced threshold the airplane arrested its descent but did not regain the 3° glide slope before again descending. The final ADS-B return was 1,200 ft from the displaced threshold and approximately level with it. During the final descent the airplane gained speed from 60 kts of calibrated airspeed to over 72 kts. The airplane’s stall speed was reported to be about 38 kts (44 mph)1 [1]. Its reported best glide speed is about 52 kts (60 mph). The airplane was faster than the recommended glide speed throughout the final approach.