CHICAGO, IL, USA
N244AA
McDonnell Douglas MD-80
DURING DESCENT A COMPLETE HYDRAULIC SYSTEM FAILURE OCCURRED. DURING THE LANDING ROLLOUT THE AIRPLANE RAN OFF THE SIDE OF THE RUNWAY & COLLIDED WITH A MANHOLE COVER COLLAPSING THE NOSE GEAR. THE POWER TRANSFER UNIT SHUTOFF VALVE, P/N 240695, FAILED; ONE OF THE DUAL VALVE BODY HALVES SEPARATED AT THE MOUNTING PLATE. THE VALVE HAD A KNOWN HISTORY OF FAILURES, AND A KIT VERSION OF A 'FIX' TO THE VALVE HAD BEEN AVAILABLE BY THE MANUFACTURER. THE FLIGHT MANUAL CAUTIONS THAT FOR LANDING WITH NO HYDRAULIC POWER, INCREASING AMOUNTS OF REVERSE THRUST SIGNIFICANTLY REDUCES RUDDER EFFECTIVENESS, AND IN THE EVENT OF DIRECTIONAL CONTROL PROBLEMS TO REDUCE REVERSE THRUST AS REQUIRED AND SELECT FORWARD IDLE IF NECESSARY TO MAINTAIN OR REGAIN CONTROL. DFDR READOUT SHOW THE APPLICATION OF THRUST GREATER THAN IDLE REVERSE DURING THE THE LANDING ROLLOUT.
A LOSS OF HYDRAULIC SYSTEM PRESSURE DUE TO THE OPERATOR'S FAILURE TO REPLACE A SYSTEM COMPONENT THAT HAD A KNOWN HISTORY OF FAILURES, AND THE PILOT'S IMPROPER USE POWERPLANT CONTROLS RESULTING IN A DEGRADATION OF RUDDER EFFECTIVENESS. A CONTRIBUTING FACTOR WAS THE FAILURE OF THE POWER TRANSFER UNIT SHUTOFF VALVE.
Source: NTSB Aviation Accident Database
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