CT156115 Harvard II - Epilogue

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Report / February 12, 2016 / Project number: CT156115 Harvard II - D Category

Location: Hillsboro, Oregon
Date: 2016-02-12
Status: Investigation Complete

Two Harvard II Instructor Pilots (IP) from 15 Wing Moose Jaw (IP1- front seat and Aircraft Commander, IP2 - rear seat) were conducting a night cross country proficiency flight to Hillsboro Airport in Oregon, USA.

On final approach to Hillsboro Airport, IP2 selected the landing gear down and noticed the Nose Gear (NG) and Right Gear (RG) indicated down and locked, but the Left Gear (LG) did not indicate down and locked.  A low approach was flown, and a climb was initiated in order to trouble shoot the landing gear problem.

With the landing gear selected down the pilots noted that the Angle of Attack (AOA) indexer lights did not illuminate, (a secondary way to confirm gear down and locked).  The pilots were not able to ascertain if the landing light or taxi light were illuminated (a tertiary way to confirm gear down and locked).  The pilots did confirm the landing gear circuit breakers (CB) were in.  The pilots then performed a landing gear lamp test for the NG, LG and RG, and observed all landing gear lights tested serviceable (three green) in both front and rear cockpits.  The landing gear was cycled up, then down, resulting in the same unsafe LG indication. 

The Landing Gear Malfunction Checklist (LGMC) was completed in its entirety with IP2 reading the LGMC while IP1 flew the aircraft and carried out the actions, but at no time did the LG indicate down and locked.  As per the LGMC, the landing gear was then cycled up, and all gear did indicate up and locked.  In such situations, the LGMC recommends a gear up landing.

IP2 made an emergency call to Portland Approach Control who then alerted emergency services.  IP1 flew the gear up landing in a full flap configuration, and during the flare the Power Control Lever (PCL) was selected to off to reduce both propeller and engine damage.  The landing was completed successfully at Hillsboro airport.  The aircraft slid 1050 feet down the runway before coming to a stop.  IP1 and IP2 egressed the aircraft while emergency services arrived on scene.

The investigation determined that the LG uplock switch failed internally, preventing completion of the electrical circuit to ground.  A failure of this switch in the open position would not allow a LG down and locked indication, even though all gear were down and locked. 

Harvard II main landing gear uplock switches are not tested periodically for electrical continuity via a resistance check, nor are they replaced after a specified period of time or number of landings.  The investigation recommends that the Senior Design Engineer develops a strategy to address main landing gear uplock switch failures.

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