MD-11
Flight Crew Air Transport Pilot (ATP)
Confusion; Human-Machine Interface
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented
Aircraft; Human Factors
While attempting to adjust volume of Captain's overhead speaker; I inadvertently turned off the #1 IRU. This occurred at about N43.00.0; W40.00.0. the middle crossing of the North Atlantic. Switched control to #2 autopilot ensured that FMS mode was NAV continued to destination. In my opinion; the current location of the Captain's overhead speaker is poor. Due to the HUD (Heads Up Display) installation; the speaker is blocked by the HUD projector and flood light. It is hard for the captain to hear and too loud for the First Officer. It is also very easy (as I have just demonstrated) to mistake the IRS switches for the speaker volume due to their proximity and that they are partially obscured by the redesign of the overhead panel. In the future I will positively identify the volume knob.
An MD11 Captain inadvertently turned off the number one IRU while attempting to adjust his speaker volume.