Q400
Maintenance Airframe; Maintenance Powerplant
Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Aircraft; Human Factors; Procedure
Maintenance personnel noted the # 1 ENG Intake Bypass Door actuator head end not connected to lower cowl support clips while they are doing the replacing work of the actuator and I was the one who had worked this actuator installation a year ago.  [Recently]; while the maintenance personnel was replacing the actuator; he noted the bolt was missing the end hole of the actuator. It went through the bearing plate but missed the actuator end hole.It has been almost a year and I honestly can't remember well; but I believe when I was working for this task I had to deal with the limited access view because there were two vertical support channel coming down right behind actuator; in between the actuator and me. And I did wiggled the actuator to line up the holes and slide in the bolt. At one point; it [the bolt] went in smoothly and I thought the bolt finally got in the hole of the actuator end hole and the bearing plate; and it was firmly secured.  Also; I believe I did take a look through the mirror for making sure the bolt in the right location. It did look like went through the bearing plate and actuator end hole. This view was only from limited direction not all around.  Maintenance personnel reworked the actuator installation. Now it is all corrected to the right installation position. I heard this event happened several time before; so I would like to ask; to put some NOTE in between the installation steps in the Aircraft Maintenance Manual (AMM) manual task.
An Aircraft Maintenance Technician (AMT) was informed the # 1 Engine Intake Bypass Door Actuator head end was found not connected to the lower cowl support clips on a Q-400 aircraft. The attach bolt he had installed had gone through the bearing support plate but missed the end hole on the actuator head. This unsecured condition had existed for approximately nine months.