A line mechanic reports a B767-400 he worked earlier required an air turnback for a left main landin...

Narrative:

A B767-400 departed but did not have safe indication for the left main landing gear door. The aircraft returned to gate where maintenance reported finding the bypass pin installed in the bypass position of the left main landing gear (medium large transport) door safety valve. The compartment itself was found properly closed. I had installed the bypass pin at the conclusion of the aircraft's most recent maintenance event; believing it was properly in place and installed. The safety block on the safety bypass valve door is intended to prevent closing the compartment door with the bypass pin installed in the bypass position. Apparently; this door's safety did not function as intended; and the door was closed with the safety bypass pin installed. This inadvertent action caused the left main landing gear door to remain open in flight.my suggestion for prevention of a recurrence would include but; not be limited to the following: a fleet-wide inspection to determine if any other aircraft's safety device attached to the safety valve compartment door are not effective in their intended function. A caution placard be placed in plain view in the safety valve compartment stating that the design will allow bypass pin to be installed in the valve while any hydraulic pressure is present.

Original NASA ASRS Text

Title: A Line Mechanic reports a B767-400 he worked earlier required an Air Turnback for a left Main Landing Gear (MLG) door unsafe indication. Gear door had not retracted and the Bypass safety pin was still installed in the MLG door safety valve.

Narrative: A B767-400 departed but did not have safe indication for the left main landing gear door. The aircraft returned to gate where Maintenance reported finding the bypass pin installed in the bypass position of the left Main Landing Gear (MLG) door safety valve. The compartment itself was found properly closed. I had installed the bypass pin at the conclusion of the aircraft's most recent Maintenance event; believing it was properly in place and installed. The safety block on the safety bypass valve door is intended to prevent closing the compartment door with the bypass pin installed in the bypass position. Apparently; this door's safety did not function as intended; and the door was closed with the safety bypass pin installed. This inadvertent action caused the left main landing gear door to remain open in flight.My suggestion for prevention of a recurrence would include but; not be limited to the following: a fleet-wide inspection to determine if any other aircraft's safety device attached to the safety valve compartment door are not effective in their intended function. A caution placard be placed in plain view in the safety valve compartment stating that the design will allow bypass pin to be installed in the valve while any hydraulic pressure is present.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	852053
Time
Date	200909
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Light	Daylight
Aircraft 1
Make Model Name	B767-400 and 400 ER
Operating Under FAR Part	Part 121
Flight Phase	Parked
Component
Aircraft Component	Main Gear Door
Person 1
Qualification	Maintenance Airframe Maintenance Powerplant
Experience	Maintenance Technician 17
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Procedural FAR Deviation - Procedural Maintenance Deviation - Procedural Published Material / Policy

A line mechanic reports a B767-400 he worked earlier required an air turnback for a left main landing gear (medium large transport) door unsafe indication. Gear door had not retracted and the bypass safety pin was still installed in the medium large transport door safety valve.