Unintended Consequences

Unhappily, the accident record bears out this articles main point: Combining STCs and performing untested modifications can have lethal effects.

Editorial Staff

Tuesday, November 25, 2014 at 12:00 AM ET

Verified

Key Takeaways:

Combining multiple Supplemental Type Certificates (STCs) or performing untested aircraft modifications can dangerously alter flight characteristics, leading to lethal outcomes.
One accident involved a Beechcraft Baron with combined STCs that increased its VMCA, but an outdated airspeed indicator contributed to a fatal spin during a low-speed maneuver.
Another incident featured a KR-2 Experimental modified with a heavier, untested engine, resulting in an uncontrollable spin after an intentional maneuver.
These cases underscore the critical need for thorough testing and correct instrumentation updates when aircraft modifications are introduced to prevent accidents.

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Unhappily, the accident record bears out this articles main point: Combining STCs and performing untested modifications can have lethal effects.

August 7, 2010, Saltsburg, Pa., Beechcraft Model 58 Baron
The accident aircraft was modified by one STC that installed vortex generators (VGs) and by another for more powerful engines, different propellers, winglets and modified engine cowlings, which also increased the airplanes VMCA. However, the airplanes airspeed indicator remained marked to indicate a lower VMCA.