Narrative:

Regarding the pilot seats in the 777 aircraft; there is an original equipment headrest that is obviously designed with a cutout area on the bottom to allow the pass-through and free movement of the shoulder harness straps. These are being replaced by a part that does not have this cutout; and in fact does cause the shoulder harness straps to rub against the bottom of the (replacement) headrest; increasing friction on the shoulder harness straps and interfering with their free movement and inertia reel recoil function. The captains on two previous flights have written this up in the logbook; but the maintenance response was that this headrest was an approved replacement part. (The captain's seat on this aircraft had the replacement part; but the captain on this flight did not elect to write it up). I find this added friction/tension on the shoulder harness an unnecessary additional distraction during critical phases of flight; i.e. Takeoff and landing; when shoulder harness use is mandatory. As you are well aware; distraction is cited as a causal factor in a significant percentage of aviation mishaps. There is also the question of performance. I do not believe that the shoulder harness inertia reel take-up function can perform as well as it was designed to with additional friction against the straps. In case of an impact; there would very likely be more strap-extended than necessary; possibly causing increased injury upon impact and subsequent rebound of the occupant. I do not believe this is an acceptable replacement part; and I doubt the veracity of the claim that it is. Discontinue using the replacement 777 pilot seat headrest that does not have the cutout on the bottom for the shoulder harness straps to pass-through. Investigate the replacement part being used on the 777 aircraft for quality and approval status.

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Original NASA ASRS Text

Title: A B777 pilot reported that the replacement headrests do not have a shoulder harness strap pass through slot and the constrained strap space now requires more effort to move the upper body when the harnesses are required causing a distraction.

Narrative: Regarding the pilot seats in the 777 aircraft; there is an original equipment headrest that is obviously designed with a cutout area on the bottom to allow the pass-through and free movement of the shoulder harness straps. These are being replaced by a part that does not have this cutout; and in fact does cause the shoulder harness straps to rub against the bottom of the (replacement) headrest; increasing friction on the shoulder harness straps and interfering with their free movement and inertia reel recoil function. The Captains on two previous flights have written this up in the logbook; but the maintenance response was that this headrest was an approved replacement part. (The Captain's seat on this aircraft had the replacement part; but the Captain on this flight did not elect to write it up). I find this added friction/tension on the shoulder harness an unnecessary additional distraction during critical phases of flight; i.e. takeoff and landing; when shoulder harness use is mandatory. As you are well aware; DISTRACTION is cited as a causal factor in a significant percentage of aviation mishaps. There is also the question of performance. I do not believe that the shoulder harness inertia reel take-up function can perform as well as it was designed to with additional friction against the straps. In case of an impact; there would very likely be more strap-extended than necessary; possibly causing increased injury upon impact and subsequent rebound of the occupant. I do not believe this is an acceptable replacement part; and I doubt the veracity of the claim that it is. Discontinue using the replacement 777 pilot seat headrest that does not have the cutout on the bottom for the shoulder harness straps to pass-through. Investigate the replacement part being used on the 777 aircraft for quality and approval status.

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.