History of Flight
On February 13, 2008, at approximately 1255 central standard time, a Piper PA-23-250, registration N62793, owned and operated by Storm Flying Service, Inc., was destroyed when it struck terrain 7.5 miles southwest of Sterling, Kansas. Visual meteorological conditions prevailed. The positioning flight was conducted under 14 CFR Part 91 on an instrument flight rules flight plan. The airline transport certificated pilot was fatally injured. The cross-country flight departed Wichita, Kansas, around 1230 and was en route to Hays, Kansas.
According to the operator, the flight was repositioning from Wichita to Hays for a daily cancelled check run. The planned route continued from Hays to Great Bend, Salina, Kansas City, and back to Wichita.
At 1249:30, a Kansas City Air Route Traffic Control Center controller directed the pilot to turn to a heading of 280 to avoid the BISON military operations area (MOA), which was active. The pilot acknowledged and altered course. At 1252:47, the controller requested a radio check; the pilot responded "loud and clear." No further transmissions were recorded.
National Track Analysis Program radar data showed the airplane on a northwesterly track at 1252:52 at an encoded altitude of 6,000 feet msl with a groundspeed of 190 knots. At 1253:40, altitude was 6,100 feet msl; at 1254:28, it was 6,200 feet msl, with groundspeed slowing to about 170 knots. Three primary targets recorded a right turn, the last at 1254:52, without altitude data. The final target was 50 feet from the main wreckage.
Several ranchers heard the airplane overhead. One described the sound as "choppy like a helicopter"; another reported a loud rumble, silence, then a soft rumble. One rancher observed the airplane in straight and level flight at a lower altitude than usual but did not continue watching.
Personnel Information
The 27-year-old pilot held an airline transport pilot certificate with multiengine land rating, a commercial pilot certificate with single-engine land and instrument ratings, and a flight instructor certificate. He held a second-class medical certificate issued October 12, 2007, with a limitation requiring corrective lenses. At his last medical application, he estimated 2,700 total hours, with 500 in the previous six months.
According to the operator's report, the pilot had logged 3,050 total hours, including 1,320 in the make and model and 1,450 in multiengine airplanes. His last flight review and Part 135 check flight occurred September 30, 2007, in a Piper PA-23 with satisfactory results.
The pilot's personal logbook showed 3,011 total hours, with 1,265 in the make and model, 340.8 in the accident airplane, and 1,411 in multiengine airplanes. Neither the flight review nor the Part 135 check flight was recorded.
Aircraft Information
The accident airplane, a 1977 Piper PA-23-250 (serial number 27-7754030), held a standard airworthiness certificate for normal operations. It was powered by two Lycoming IO-540-C4B5 engines rated at 250 horsepower each, equipped with two-blade Hartzell controllable-pitch propellers.
The airplane was maintained under a 100-hour/annual inspection program. The last 100-hour inspection was completed January 18, 2008, at an airframe total time of 10,852 hours (tach 2,254). The last annual inspection was August 1, 2007, at 10,653 hours (tach 2,055). The airplane flew about 73 hours between the last inspection and the accident, with an estimated total time of 10,924 hours.
On May 16, 2002, the rod end and bolt on the upper stabilator trim actuator were replaced by Hinman Aviation using Piper-supplied parts, as Piper sought samples for corrosion evaluation. No corrosion was found on the returned part.
Meteorological Information
The closest official weather observation station was Hutchinson Municipal Airport (HUT), 26 nautical miles southeast of the accident site at 1,543 feet msl. A METAR at 1252 reported wind from 200 degrees at 14 knots, visibility 10 miles, clear sky, temperature 12°C, dewpoint -2°C, and altimeter 29.87 inches.
Wreckage and Impact Information
The accident site lay in an open, dormant wheat field at 1,707 feet msl. Debris extended 668 feet along a magnetic heading of 050 degrees from the initial impact point, marked by a narrow ground scar with red and white paint chips and fiberglass slivers.
Multiple ground scars and debris continued 465 feet to the main wreckage. A 35-foot-long, 5-foot-wide area was discolored with vegetation heat exposure, consistent with a flash fire.
The debris path contained torn metal, insulation, Plexiglass, engine hoses, accessories, cowling portions, and cabin instruments. Both ailerons and several wing segments were found, some charred and partially consumed by fire.
The left stabilator separated from the empennage and lay left of the debris field, with dark aft streaking from leading edge rivets. It was crushed aft and inboard at the outboard tip, with the leading edge partially separated and bent aft.
The right stabilator separated and was adjacent to the main wreckage, also exhibiting dark aft streaking.
The main wreckage (fuselage, vertical stabilizer, rudder, and left wing portion) came to rest 468 feet from initial impact. The left wing was inverted and partially attached, with heat and fire damage near the fuel tank. The fuselage lay on its left side; the cabin and instrument panel were destroyed.
Cabin instruments showed: artificial horizon destroyed; airspeed indicator at 230 knots; altimeter needles separated; Kollsman window at 29.79; HSI heading bug set at 295; needles separated.
Both engines separated and came to rest north of the main wreckage. Examination revealed normal operational signatures with no anomalies.
A section of the right wing, including the landing gear, came to rest north. The landing gear was down. The wing separated at the root; aft trailing edge skin was torn up and outboard; leading edge skin inboard of the nacelle was torn aft and crushed; remaining structure outboard showed heat exposure.
The left aileron follow-up cable separated at the bell crank; the cable from the bell crank arm to the chain and sprocket assembly was continuous. The bell crank arm separated in overload. The roll bridal cable was frayed at the autopilot servo capstan.
The right aileron bell crank separated from the wing; both aileron and follow-up cables remained attached. The right aileron cable attached to the chain and sprocket assembly. The right aileron balance cable separated from the left.
The flap actuator was fully extended, consistent with flaps fully retracted.
Both rudder cables remained attached to the rudder horn and were continuous forward to the rudder bar. The rudder trim jackscrew exhibited four threads; neutral is five to six, zero is full nose left.
The stabilator cables were attached at the horn tube and continuous to the control column sprocket and chain. The pitch servo cable separated from the servo drum; the follow-up cable was tangled. The stabilator trim jackscrew showed two threads, consistent with slight nose down trim (zero = full nose down, five to six = neutral).
Medical and Pathological Information
An autopsy performed February 14, 2008, determined the cause of death as multiple blunt impact injuries. Toxicological testing by the FAA's Civil Aerospace Medical Institute was negative for carbon monoxide, cyanide, ethanol, and screened drugs.
Tests and Research
The wreckage was relocated to Lancaster, Texas, for examination. The Safety Board IIC, Piper Aircraft, and Lycoming Engines examined it on March 25–26, 2008.
The stabilators are twin-spar, eight-rib box structures. The right stabilator (part number 15658-23, serial number 27-0256) separated in one piece. Upper skin had two punctures; leading edge separated from spars. Heavy dark streaking on the inboard eight inches of lower skin, with numerous rivets exhibiting streaking. Lower skin faying surfaces had very little primer and dark corrosion/fretting products. The trim tab was intact with slight downward deformation; the tab hinge was clean with no corrosion. The trim tab attach bracket had scratching, missing rivet heads, and damaged button heads. Deformation indicated separation forward and down; all fractures were overload.
The left stabilator (part number 15658-22, serial number 27-0256) separated in one piece. Outboard tip crushed aft and inboard. Similar streaking and corrosion findings. Trim tab hinge clean; attach bracket scratched with missing rivet heads. Deformation indicated rearward separation; overload fractures.
The tailcone separated into two pieces. The right piece had a semi-circular deformation consistent with the trim rod diameter. The stabilator trim bell crank remained attached; trim cables were in full nose down position. Both attach bolts were intact with cotter pins, but the left attach point exhibited significant movement and slop, while the right was firm. The left hole was significantly elongated. The stabilator trim pushrod forward rod end fractured in the threaded portion; the aft jam nut was damaged, not seated. The rod had circumferential scratching and a longitudinal scratch.
The stabilator up and down stops showed impact damage and bolt head impressions.
Additional Information
Pilots who flew the accident airplane in the weeks prior reported no mechanical anomalies. The chief of maintenance at Hinman Aviation could not recall any recent maintenance issues.
Piper Aztec Service Manual specifies torquing the nut on the stabilator trim control rod bolt to 50–75 inch-pounds. Airworthiness Directive 79-26-01 and Piper Service Bulletin 606 address bonding between ribs and skin but were not applicable to the accident airplane's stabilator serial numbers.