History of Flight
On March 13, 2008, at 0900 eastern daylight time, a Cessna 172S, registration N284SP, operated by Kemper Aviation Incorporated, was substantially damaged when it impacted flat terrain in Indiantown, Florida. The certificated airline transport pilot and three passengers were killed. The aerial observation flight departed Okeechobee County Airport (OBE) at 0802 and was operated under 14 CFR Part 91. Visual meteorological conditions prevailed, and no flight plan was filed.
A witness reported observing the airplane make multiple passes over cattle pastures near Indiantown at an estimated altitude of 200 to 250 feet above ground level (agl). During one pass, the nose dropped, the airplane banked right with increased engine noise, and it descended into the ground.
Handheld GPS units recovered from the airplane showed that after departure, the airplane flew southeast along Lake Okeechobee at about 470 ft agl. Starting around 0815, it flew S-turn patterns and made multiple circling passes at two locations, with groundspeeds between 42 and 100 mph and altitudes between 297 and 615 ft msl. Around 0856, the airplane began a third orbit, then rapidly lost altitude from about 350 ft msl. The final descent rate exceeded 3,000 feet per minute. The last GPS position was recorded at 0900:03, with a groundspeed of 53 mph.
Personnel Information
The pilot, age 36, held an airline transport pilot certificate with single-engine, multiengine, and instrument ratings, as well as a flight instructor certificate. His logbook was not located. Flight records from the operator showed 331.6 hours flown with the operator since January 9, 2007, including 6.3 hours in the accident airplane. On his latest FAA first-class medical application (January 31, 2007), he reported 2,900 total flight hours. He was co-owner of Kemper Aviation Incorporated.
Aircraft Information
The four-seat, high-wing, fixed-gear airplane (serial number 172S8235) was manufactured in 1999 and had accrued 5,240.3 total hours. An annual inspection was completed on January 23, 2008, 72.5 flight hours before the accident. The Lycoming IO-360-L2A engine (serial number L-29492-51A) had 3,421.9 total hours and 72.5 hours since a major overhaul in December 2007.
Maintenance squawk records noted that on February 20, 2007 and June 10, 2007, pilots reported an inoperative stall warning horn. Both times, maintenance inspected the system and found it operative. After the accident, the stall warning horn was visually inspected and found undamaged, but testing with suction did not produce a clearly audible tone. Subsequent disassembly at the NTSB revealed an aluminum reed section detached, with a heavy oxide layer on the fracture surface and no yielding or deformation.
Meteorological Information
The closest AWOS at OBE (17 miles northwest) reported at 0901: wind from 300° at 4 knots, visibility 7 statute miles, clear skies, temperature 15°C, dew point 13°C, altimeter 30.07 inches of mercury.
Wreckage and Impact Information
The airplane was found inverted, oriented on a bearing of 225° magnetic. The initial impact was a 2-foot-wide divot, followed by a 5-foot grass excavation, with a debris path continuing 90 feet to the main wreckage. All flight control surfaces were accounted for. The lower fuselage exhibited accordion crushing. The right wing tip was separated, with a chordwise crease and upward buckling. The flap actuator indicated a 15° flap setting, and the elevator trim tab indicated a 5° up position. Control continuity was confirmed.
The engine separated from its mount and remained partially attached by throttle and mixture cables. Postimpact fire damage was observed. The propeller separated at the crankshaft flange, with one blade showing torsional S-bending and the other slight aft bending. Approximately 5.5 gallons of fuel were recovered from the left tank and 4 gallons from the right. A strong smell of aviation gasoline was detected in soil under the wing roots.
Medical and Pathological Information
Autopsies determined the cause of death for all occupants as blunt force trauma. Toxicological tests on the pilot were negative for all screened drugs and alcohol.
Additional Information
A certified flight instructor from Kemper Aviation stated that the accident flight was a bird survey for Florida Atlantic University. Flights were typically conducted at 500–1,000 ft agl, 85 knots, with flaps 0–10°. Turns around a point were flown at 60 knots with flaps 10–20°, often with a slip condition. The research leader had previously requested descents to 200–250 ft agl and slow flight “on the stall horn.” A previous employee described similar techniques for photography, often hearing the stall warning horn during maneuvers.
Weight and balance calculations showed a basic empty weight of 1,696.2 pounds and a useful load of 861.8 pounds. Occupant weights were 402 pounds (front) and 366 pounds (rear), with 40 pounds of baggage. The airplane had a fuel capacity of 56 gallons; 17.9 gallons were added before departure from West Palm Beach.
According to the POH, at 2,550 pounds gross weight and flaps 10°, stall speeds are 50 knots CAS at 0° bank, 54 knots at 30° bank, 59 knots at 45° bank, and 71 knots at 60° bank.