Incident Overview
Description
Lost control after encountering clear air turbulence at FL430. The Learjet had exceeded its Mach limits when the pilots responded to the encounter. The Mach overspeed warning horn had been disconnected with an unauthorized cut-off switch. PROBABLE CAUSE: “An unexpected encounter with moderate to severe clear air turbulence, the flightcrew’s improper response to the encounter, and the aircraft’s marginal controllability characteristics when flown at and beyond the boundary of its high altitude speed envelope, all of which resulted in the aircraft exceeding its Mach limits and a progressive loss of control from which recovery was not possible. Contributing to the accident was the disconnection of the Mach overspeed warning horn with an unauthorized cut-out switch which resulted in the absence of an overspeed warning that probably delayed the crew’s response to the turbulence encounter, and the insonsistencies in aircraft flight manuals and flightcrew training programs regarding the use of spoilers to regain control.”
Primary Cause
Improper response to moderate to severe clear air turbulence, combined with the aircraft’s marginal controllability characteristics when flown at and beyond its high altitude speed envelope.Improper response to moderate to severe clear air turbulence, combined with the aircraft’s marginal controllability characteristics when flown at and beyond its high altitude speed envelope.Share on:
