History
On October 29, 2011, at approximately 1021 eastern standard time, an experimental Interplane SRO Skyboy, N58784, was substantially damaged when it impacted terrain during an uncontrolled descent near Richards Field (04FA), Miami, Florida. The commercial pilot and the passenger sustained fatal injuries. Visual meteorological conditions prevailed, and no flight plan was filed for the local flight, which originated from 04FA. The personal flight was conducted under 14 CFR Part 91.
Witnesses stated that they observed the pilot and passenger performing maintenance and installing vortex generators on the wings for the two weeks preceding the accident flight. On the morning of the accident, witnesses observed the pilot preparing the airplane before a brief solo local flight. During that flight, the passenger spoke with the pilot via radio, and the pilot reported the airplane was performing satisfactorily. He returned uneventfully and told witnesses the airplane was "flying fine."
The pilot and passenger then departed on the accident flight. After flying locally, they returned to the vicinity of 04FA. Witnesses observed the airplane overflying the airport at an estimated altitude between 350 and 3,000 feet agl. One witness reported that the airplane appeared to enter an aerodynamic stall, followed by a second stall from which it did not recover, then began spiraling toward the ground in a corkscrew-like descent. Several witnesses responded to the accident site and reported that both occupants were wearing their restraints.
Personnel Information
The pilot held a commercial pilot certificate with ratings for airplane single- and multi-engine land and instrument airplane. He held an FAA third-class medical certificate issued April 28, 2009, with a limitation for corrective lenses. He reported 2,200 total flight hours. He also held a mechanic certificate with airframe and powerplant ratings. His personal flight logs were not recovered.
Aircraft Information
The high-wing airplane featured tube and fabric construction, two-place side-by-side seating, and dual flight and engine controls. It was powered by a Rotax 912ULS reciprocating engine mounted in a pusher configuration behind and above the cockpit and wings.
According to FAA airworthiness records, the airplane was issued a special airworthiness certificate in the experimental category for exhibition. Operating limitations issued April 16, 2004, included requirements for notifying the FSDO before flying after a major change, and for a condition inspection within the preceding 12 calendar months. Other limitations applied to Phase II flights, including geographical restrictions and requirements for program letters. No current or archived program letters could be located. A review of FSDO documents showed no evidence of program letter updates or notifications of major changes.
FAA registration records indicated the pilot purchased the airplane in 2004 and transferred ownership about 6 months before the accident. The new registered owner stated the pilot continued to fly and perform maintenance and held the maintenance records.
Review of the airplane's "Daily Operational Records" showed an entry dated May 12, 2004, certifying completion of required flight test hours. Additional flights were logged through July 15, 2005. Several entries between April 2004 and March 2005 noted installation of a replacement engine, transponder, and altitude encoder, as well as periodic maintenance. No entries after March 26, 2005, were found, nor any documentation of the 12-month condition inspection. No maintenance documentation was found for the installation of vortex generators, and no information documenting their origin or applicability to the airplane was found. No documents or witness statements suggested the pilot had a structured flight test plan for the vortex generators.
Meteorological Information
At 1053, weather at Kendall-Tamiami Executive Airport (TMB), 7 miles northeast, included wind from 200° at 9 knots gusting 16 knots, visibility 10 statute miles, few clouds at 2,000 feet, temperature 28°C, dew point 24°C, and altimeter 29.87 inHg.
Flight Recorders
The airplane was not equipped with flight data recorders, but a Garmin GPSMAP 496 handheld GPS was recovered. Data from the device included 28 sessions from June 11 to October 29, 2011. The accident flight was recorded from 0957 to 1021; the preceding flight from 0917 to 0941.
The preceding flight included slow passes along runway 9/27 at 04FA while on the ground. The airplane then departed west, circled the airport left at about 1,100 feet GPS altitude, completed a second circuit, and landed on runway 27 at 0940. The slowest GPS ground speed recorded was 29 knots during the upwind-to-crosswind phase.
The accident flight departed runway 27 at 1003. The airplane flew about 3 nautical miles northwest, maneuvering at about 1,000 feet GPS altitude. After about 10 minutes, it began a gradual climb back toward the airport from the north, maintaining a groundspeed of about 45 knots at about 1,500 feet. At 10:18:59, it slowed to a low of 21 knots about 1 minute later while climbing to about 2,000 feet, nearly over the runway. The airplane continued southwest for 35 seconds, maintaining 26-35 knots at about 1,900 feet. At 10:20:45, it descended to 1,800 feet and slowed to 23 knots groundspeed on a track of 246°. Given reported winds, approximate true airspeed was 30 knots. The airplane then began a rapid descent to the left, and data ceased at 10:21:01. Average calculated rate of descent exceeded 5,600 feet per minute.
Wreckage and Impact Information
The wreckage was consistent with a nose-low, slight right-wing-down impact, with the fuselage on a 170° magnetic heading. The front was crushed aft into the cockpit. Wings separated from forward fuselage attach points. Vortex generators were found on the top surfaces of both wings. The tail boom was partially separated downward with a slight right bend. One propeller blade was separated at the root, consistent with contact with the tailboom.
Flight control continuity was confirmed from cockpit to all surfaces. Flaps appeared retracted. The pre-impact elevator trim position could not be determined. The left elevator trim tab's upper cable was separated at the control horn interface, and corrosion was present at the separation. The assembly was examined by the NTSB Materials Laboratory.
The Materials Laboratory report stated the control cables were attached via pins through clevis fittings mounted on cylindrical, soldered cable ends. The upper cable was separated at its clevis fitting. The clevis was frozen to the pin, and the pin was frozen to the control horn; all resisted movement. The upper cable exhibited heavy red rust deposits and no lubricant. The cable was a zinc-coated carbon steel wire rope with 7 wires per strand and 7 strands, meeting MIL-DTL-8342M3 Type I Composition A, with minimum breaking load of 270 lbf.
Examination of the cable separation found all wire fractures at the point where the cable passed through the clevis. The cable remained tightly wound with no fraying. Only a few wires had clean fracture faces; most were obscured by rust. Ultrasonic cleaning removed red rust but not darker deposits. After further cleaning, SEM examination revealed severe corrosion damage adjacent to the separation. Most wire ends were obliterated by corrosion; the few remaining features were typical of overstress separations.
The lower trim tab cable also showed surface corrosion, less widespread, but its diameter was reduced as it passed through the clevis.
Medical and Pathological Information
The Miami-Dade County Medical Examiner conducted a postmortem examination of the pilot. The cause of death was multiple blunt traumatic injuries. The FAA Bioaeronautical Sciences Research Laboratory conducted toxicology tests; results were negative for carbon monoxide, cyanide, and ethanol. An unquantified amount of Amlodipine was found in blood and liver specimens.
Additional Information
FAA Advisory Circular 43.13-1B provides guidance on aircraft inspection and repair, including control cable inspection and replacement. The NTSB referenced these guidelines but did not attribute causation. FAA Advisory Circular 90-89A provides flight test guidance for amateur-built and ultralight aircraft; the NTSB noted that similar principles would apply to modifications of experimental aircraft. The accident airplane was not certificated as amateur-built, but the NTSB referenced the guidance in the context of flight testing.