NTSB CAROL · Event
Event FTW94FA044
Registry · N4YP
FAA Aircraft Registry record.
Make / Model
PIPER PA-28-181
Year of manufacture
1999
Engine
LYCOMING 0-360-A1D (180 hp)
Seats / Engines
4 seats · 1 engine
Last airworthiness date
19991015
ADS-B equipped
Yes — Mode-S A4AA23
Registrant of record
BOBS BIZ LTD
Source: FAA Aircraft Registry (releasable master file).
Aircraft involved
Probable cause & findings
WAS THE IN FLIGHT FAILURE OF THE LEFT AILERON FOR REASONS UNDETERMINED.
Factual narrative
HISTORY OF FLIGHT
On December 5, 1993, approximately 1040 central standard time, an Upton Mustang M-II, N4YP, was destroyed during an uncontrolled descent approximately 6 miles southwest of Guthrie, Oklahoma. The private pilot was fatally injured. Visual meteorological conditions prevailed for the personal flight. The pilot's wife said her husband departed Downtown Airpark in Oklahoma City between 0930 and 1000 for a local personal flight. The only known witness to the accident, a farmer in a field, said he heard a loud noise, looked up, and saw the airplane diving towards the ground.
AIRCRAFT INFORMATION
According to the airplane's designer and the kit's manufacturer, Mustang owners and builders were cautioned several years ago to remove the pop rivets from the aileron counterweights and to replace them with a stronger type of rivet. There were no entries in the aircraft records to indicate this modification had been accomplished.
WRECKAGE AND IMPACT INFORMATION
Both wings and the left wing tip, left elevator, and left aileron were located 1, 2, and 3 miles south of the main body of wreckage, respectively. The right wing tip and both aileron counterweights were not recovered. The right side of the wing carry-through spar was bent down and twisted aft at the fracture point. Both control sticks remained attached to the aileron torque tubes, and one of the torque tubes remained attached to the right aileron. Fracture surfaces were examined by a metallurgist from the University of Denver. All failures were found to be overload. The leading edge of the left aileron was torn at the rivet line and the aluminum skin was spread out and flattened. The outboard portion of the left elevator leading edge was similarly torn at the rivet line, and the hinge attachment was bent to the right.
MEDICAL AND PATHOLOGICAL INFORMATION
An autopsy (case no. 9305339) was performed on the pilot by the Oklahoma State Medical Examiner's Office in Oklahoma City, Oklahoma. The results of the toxicological examination, performed by the Armed Forces Institute of Pathology, are attached to this report.
ADDITIONAL INFORMATION
According to the pilot's wife and corroborated by his logbook, the pilot had never taken aerobatic instruction nor logged any aerobatic flights. A WITNESS HEARD A LOUD NOISE AND OBSERVED THE AIRPLANE DIVING TOWARDS THE GROUND. BOTH WINGS AND THE LEFT WING TIP, LEFT ELEVATOR, AND LEFT AILERON WERE LOCATED 1, 2, AND 3 MILES SOUTH OF THE MAIN BODY OF WRECKAGE, RESPECTIVELY. THE RIGHT SIDE OF THE WING CARRY-THROUGH SPAR WAS BENT DOWN AND TWISTED AFT AT THE FRACTURE POINT. THE LEADING EDGE OF THE AILERON AND THE OUTBOARD PORTION OF THE ELEVATOR LEADING EDGE WERE TORN AT THE RIVET LINE. THE AILERON SKIN WAS FLATTENED. THE AILERON COUNTERWEIGHTS WERE NOT RECOVERED. THE AIRPLANE DESIGNER AND KIT MANUFACTURER CAUTIONED OWNER/BUILDERS TO REPLACE THE AILERON COUNTERWEIGHT POP RIVETS WITH A STRONGER TYPE OF RIVET. MAINTENANCE RECORDS DID NOT DISCLOSE WHETHER THIS HAD BEEN ACCOMPLISHED. Source: NTSB Aviation Accident Database (Pre-2008 Archive) Retrieved: 2026-02-12
Verbatim from NTSB's published report. Source file
NTSB_1993_FTW94FA044.txt.
Findings + structured fields enriched from FAA avall.mdb.
Full investigation docket on
data.ntsb.gov ↗.
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Related research
What the literature says.
Academic papers and agency reports matching this event's aircraft type or causal vocabulary (maintenance). Sourced from NASA NTRS, NTSB Safety Studies, FAA CAMI, AOPA Air Safety Institute, Embry-Riddle Scholarly Commons, arXiv, and the Semantic Scholar academic graph.
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- Embry-Riddle Scholarly Commons 2024 · Journal article (IJAAA)
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