Final Flight: 690A broke up in flight

 - February 8, 2008, 11:01 AM

Aero Commander 690A, Antlers, Okla., Oct. 15, 2006–The NTSB blamed the
in-flight breakup of the experimental Aero Commander on the pilot’s failure to reduce airspeed in moderate turbulence. Contributing factors were his decision to exceed the maximum takeoff weight, and the prevailing turbulence.

N55JS was on an IFR flight from Wiley Post Airport to Orlando, Fla., when it broke up in flight near Antlers. All four occupants were killed and the airplane was destroyed.
About 37 minutes after the Aero Commander departed, radar information revealed it was flying at 23,100 feet msl.

It made a left 180-degree turn, descending at a rate of approximately 13,500 fpm. The last radar contact was at 15,100 feet msl. The airplane crashed in a densely wooded area. An examination of the airframe revealed that the airplane’s design limits had been exceeded, and that the examined fractures were due to overload failure.

Four days before the flight the airplane was awarded an Experimental certificate after the installation of two MT-Propellers five-blade composite propellers. The FAA placed 26 limitations on the airplane.

Limitation number 11 stated, “No person may be carried in this aircraft during flight unless that person is essential to the purpose of flight.” The aircraft was
1,038 pounds over mtow at takeoff.

There was widespread light to moderate upper-level turbulence due to wind shear
in the area. Airspeed determined from radar data ranged from 275 to 307 ktas. A 1995 service bulletin reported “two accidents involving Model 690 series aircraft resulting in loss of the aircraft, due to encountering turbulence while descending at high airspeed. Excessive airspeed in turbulence can cause structural damage or loss of the aircraft.” Placards in the airplane warned of structural damage in moderate turbulence with speeds of more than 180 knots.