# NTSB FTW94FA044: Upton Mustang M-II, N4YP, Guthrie, OK, December 5, 1993 - Type: NTSB accident investigation - Classification: Accident · Fatal · Field investigation · Final report - Date: December 5, 1993, 10:40 local (16:40 UTC) - Place: Guthrie, OK - Coordinates: 35.840415, -97.420555 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=35.8404&lon=-97.4206&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: Fatal - Injuries: 1 fatal - Status: Completed, report September 13, 1994 - Report: Approved by Office Director - NTSB case key (mKey): 18873 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=FTW94FA044 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/18873/pdf - Page: https://openairdocs.org/ntsb/FTW94FA044 ## Probable cause WAS THE IN FLIGHT FAILURE OF THE LEFT AILERON FOR REASONS UNDETERMINED. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, cruise - normal - flight control,aileron - failure,total (cause) - reason for occurrence undetermined (cause) - In flight collision with terrain/water, descent - uncontrolled ## Analysis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actual 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. ## Aircraft - Registration: [N4YP](https://openairdocs.org/deregistered/N4YP-1994-02-23), registration cancelled 1994-02-23, S/N MII301 (OpenAirDocs) - Reported make and model: UPTON MUSTANG M-II (MUSTANG M-) - Registry model: [Upton MUSTANG M-II](https://openairdocs.org/model/upton-mustang-m-ii) (registry code 1690425) (OpenAirDocs) - Category: Airplane, amateur-built - Serial number: M-II-301 - Airframe hours: 1088 - Engines: LYCOMING O-360-A1A 180 horsepower reciprocating - Damage: Destroyed - Flight: Personal, Part 91 - Registered owner: Cammack, Kevin J. - Airworthiness certificate: Special, Experimental (Special) - Last inspection: AAIP, June 1, 1993, 77 hours before - Departed: 2DT, OKLAHOMA CITY, OK ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 35; private; airplane ratings: single-engine land, single-engine sea; medical: class 3, valid medical--w/ waivers/lim; seat: front; toxicology performed; flight hours: 806 total, 269 in this make and model, 751 as pilot in command, 34 in the last 90 days ## Weather - Conditions: Visual (VMC), Day - Wind: 360° at 17 knots, gusting 26 - Visibility: 15 statute miles - Lowest ceiling: none - Temperature: 54 °F, dew point 27 °F - Altimeter: 29.00 inHg - Observed at: PWA, 17 nm away ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 19931205045959A](https://openairdocs.org/incident/19931205045959A), Dec 5, 1993: Amtrbb MUSTANG2, Guthrie, OK, Destroyed, 1 fatal. Came apart in air no witnesses. Pop rivets not replaced for better type on aileron counterweights per manufacterer. From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.