N55JS

HISTORY OF FLIGHT

On October 15, 2006, approximately 1303 central daylight time, an experimental Aero Commander 690A twin-engine turboprop airplane, N55JS, was destroyed following an in-flight breakup while in cruise flight near Antlers, Oklahoma. The airline transport rated pilot, airline transport rated co-pilot, and both passengers sustained fatal injuries. The airplane was registered to and operated by the pilot. Instrument meteorological conditions prevailed and an instrument flight rules flight plan was filed for the 14 Code of Federal Regulations Part 91 personal flight. The 928-nautical mile cross-country flight departed the Wiley Post Airport (PWA), near Oklahoma City, Oklahoma, approximately 1225, and was en route to the Executive Airport (ORL), near Orlando, Florida. The reported purpose of the flight was for the occupants to attend the National Business Aviation Association's annual convention.

According to line crew personnel, on the morning of the accident they had been instructed to pull the airplane from its hangar and to service the main fuel tanks for an approximate 1000 departure. About 0800, one of the line crew proceeded to the airplane's hangar intending to pull the airplane outside for fueling. When he arrived at the hangar he found 4 or 5 employees, installing the airplane's interior, servicing the landing gear struts with nitrogen, and completing "other miscellaneous orders." He was informed that the airplane was not yet ready to be fueled.

Around 0900 the airplane was brought out to the flight line. About this time the line crew was instructed, by one of the ServiCenter managers, that in addition to servicing the airplane's main fuel tanks, the "slipper" fuel tanks should also be completely filled with fuel. The line crew proceeded by servicing the airplane as requested with 489 gallons of Jet A fuel.

The line crew reported that both pilots arrived around 1000. One pilot performed a preflight inspection of the airplane while the other called flight service for a weather briefing. According to the McAlester Flight Service Station, the pilot contacted them by telephone at 1050 and received a full weather briefing. Following the briefing the pilot filed an IFR flight plan from PWA to ORL. The cruise altitude requested for the flight was 27,000 feet MSL. The pilot stated the flight would take three hours and thirty minutes and there would be four persons on board.

The pilots received their IFR clearance at 1215 and were cleared for takeoff at 1225. Approximately 37 minutes after departure, radar information revealed N55JS was flying on a southeasterly heading at a cruise altitude of 23,100 feet mean sea level (MSL). At 1302, radar control tracking indicated the airplane performed a left 180-degree turn while descending at a rate of approximately 13,500 feet per minute. The last radar contact was at 1303 while at 15,100 feet MSL. The airplane was located the next morning by local law enforcement personnel, scattered across a densely wooded area.

There were no reported witnesses to the accident.

PERSONNEL INFORMATION

There were two airline transport pilots (ATP) onboard the airplane at the time of the accident. According to line personnel, the pilots were occupying the front two seats during departure. The pilot seated in the front left seat had called flight service for the weather briefing and had filed the fight plan. The flight plan listed the individual seated in the right seat as the pilot-in-command for the flight.

A review of information on file with the FAA Airman's Certification Division, Oklahoma City, Oklahoma, revealed the right seat pilot held an airline transport pilot certificate for airplane multi-engine land. The pilot also held a commercial certificate with ratings for airplane single-engine land, and instrument airplane. In addition, the pilot held a flight instructor certificate for airplane single-engine land, multi-engine land, and instrument airplane. The pilot held a second-class medical certificate issued on July 27, 2006, with no restrictions. The pilot's personal flight records were not located during the course of the investigation; however, on August 6, 2006, the pilot reported having logged 6,450 hours total time of which 150 were in the same make and model of airplane, with 80 hours in the previous 90 days.

A review of information on file with the FAA Airman's Certification Division, revealed the left seat pilot held an airline transport pilot certificate with ratings for airplane multiengine land. The pilot also held a commercial certificate with ratings for glider, airplane single engine land, and instrument airplane. The pilot held a third-class medical certificate issued on October 13, 2005, with restrictions. The pilot's personal flight records were not located during the course of the investigation; however, on August 6, 2006, the pilot had reported having logged 6,500 hours total time of which 2,000 were in the same make and model of airplane, with 50 hours in the previous 90 days.

AIRCRAFT INFORMATION

The 1974-model experimental Aero Commander 690A, serial number 11195, was a high wing, semi-monocoque airplane, with a retractable landing gear, and was configured for eight occupants. The airplane was powered by two Honeywell Aerospace TPE331-10T-515K turboprop engines which were driving five bladed composite MT-Propellers.

According to the airframe logbook, the airplane's most recent 150 hour periodic inspection was completed on December 16, 2005, at an airframe total time of 7,923 hours. Investigators were not able to locate the airplane's Hobbs meter during the course of the investigation and were unable to determine the airplane's total time at the time of the accident; however, the airframe logbook listed the total time as 7,943.7 hours on October 6, 2006.

The engine maintenance records revealed that the left and right engines had been last inspected in accordance with a Periodic 150 hour inspection on October 16, 2005. At the time of inspection the left engine had accumulated approximately 4,491.1 hours, and the right engine 4,904.1, since overhaul. At last inspection each engine had accumulated 35 hours since the last hot section inspection.

A review of the airframe maintenance records revealed that "slipper type" external fuel tanks were installed on October 6, 2006, in accordance with a supplemental type certificate (STC). These external tanks consist of two externally mounted fuel tanks attached to the airplane's wing just outboard of both engine nacelles. Each of the two "slipper" tanks can hold 50 gallons of fuel for a combined total of 100 gallons. With both tanks full the added weight of fuel to the airplane would be 670 lbs.

The airplane was awarded an experimental certificate on October 11, 2006, for the purpose of "Market Survey." This was due to the installation of two, five bladed composite propellers that did not meet the airplane's original type design. No pre impact anomalies were noted with either propeller during the investigation.

Along with the experimental certificate, 26 limitations were placed on the airplane by the Federal Aviation Administration (FAA). Limitation number 11 stated, "No person may be carried in this aircraft during flight unless that person is essential to the purpose of flight."

Investigators performed weight and balance calculations using fueling records and the airplane's weight and balance statement dated the day of the accident, October 15, 2006. The calculations were performed using the FAA's standard weight of 170 pounds for each of the four occupants, 200 pounds estimated weight for luggage and loose equipment, and an estimated fuel burn off of 50 pounds consumed before takeoff.

According to the airplane's Type Certificate Data Sheet (TCDS), the airplane's maximum takeoff weight was 10,250 pounds. The total takeoff weight of the accident airplane was estimated at 11,288 pounds. The center of gravity (CG) was estimated to be within limits.

METEOROLOGICAL INFORMATION

At 1252, the weather observation facility at Atoka Municipal Airport (AQR), near Atoka, Oklahoma, located 28 nautical miles northwest from the site of the accident reported wind from 080 degrees at 3 knots, visibility 1.75 statute miles, heavy rain, scattered clouds at 1,600 feet, overcast ceiling at 2,200 feet, temperature 57 degrees Fahrenheit, dew point 57 degrees Fahrenheit, and barometric pressure setting of 29.84 inches of Mercury.

Weather data showed that widespread occasional light to moderate upper-level non-convective turbulence was present through the south-central region of the United States at the time of the accident. This turbulence was due, in part, to a strong jet stream moving eastward. The jet stream, along with an upper disturbance, caused an outbreak of scattered moderate to heavy thunderstorms over Oklahoma and northeastern Texas. Additionally, severe thunderstorms were occurring over the Texas panhandle.

The observed upper air soundings for Norman, Oklahoma, and Fort Worth, Texas, at 1900 indicated vertical wind shear of about 10 knots per thousand feet around 23,000 feet. In addition, analysis of soundings data showed light to moderate turbulence was possible in those areas at and above 23,000 feet.

Around the time of the accident pilot weather reports (PIREP) from Oklahoma and Texas indicated widespread light to moderate upper level turbulence due to wind shear. About 44 minutes after the accident a PIREP from a pilot of an Embraer 145 near McAlester, Oklahoma, about 50 miles north of the accident site, reported moderate turbulence, and moderate mixed icing at FL280.

An AIRMET for occasional moderate turbulence above 24,000 feet was valid for the region at the accident time. A review of the pilot's weather briefing transcript revealed that the pilot was informed of this AIRMET.

COMMUNICATIONS

A review of radio communications b...