Narrative:

En route from lhr-jfk a correct position of 55N 10W was given to shanwick. In between 55N 10W and 57N 20W at XA55Z the captain's clock stopped. When the clock stopped the times in the FMC and CDU were incorrect, so that when the position report was given for 57N and 20W, an erroneous time was given, and an erroneous estimate for 58N 30W given. The first officer began to doubt the validity of the 58N 30W estimate and discovered the clock problem, and a corrected position report for 57N 20W was made and an updated estimate was made for 58N 30W. The clock was operating correctly on departure and climb out. It is surmised that the clock stopped because when the captain's right foot is on the foot rest, the sole of his shoe can physically touch the GMT set knob located in the lower right corner of the clock and move it to 'hold' position. I recommend a simple spring steel guard be affixed to the instrument panel to cover the set knob. Callback conversation with reporter revealed the following information: the reporter says that now that he has talked to several other pilots at his air carrier he believes that the clock vulnerability may be peculiar to this particular aircraft. It seems that the foot rest below the instrument panel on this aircraft is too close to the panel and this allows ones shoe toe to touch the clock controls and perhaps, as in this case, to stop the clock. Therefore, the reporter thinks that his air carrier should put the standard foot rest into this aircraft and prevent further similar occurrences. This analyst agrees.

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Original NASA ASRS Text

Title: POS RPTING -- THE CLOCK STOPPED BECAUSE THE CAPT PUT HIS FOOT ON THE SET KNOB AND THEREFORE GAVE HIS POS RPT AND ESTIMATE INACCURATELY TO CTR CTLRS.

Narrative: ENRTE FROM LHR-JFK A CORRECT POS OF 55N 10W WAS GIVEN TO SHANWICK. IN BETWEEN 55N 10W AND 57N 20W AT XA55Z THE CAPT'S CLOCK STOPPED. WHEN THE CLOCK STOPPED THE TIMES IN THE FMC AND CDU WERE INCORRECT, SO THAT WHEN THE POS RPT WAS GIVEN FOR 57N AND 20W, AN ERRONEOUS TIME WAS GIVEN, AND AN ERRONEOUS ESTIMATE FOR 58N 30W GIVEN. THE FO BEGAN TO DOUBT THE VALIDITY OF THE 58N 30W ESTIMATE AND DISCOVERED THE CLOCK PROB, AND A CORRECTED POS RPT FOR 57N 20W WAS MADE AND AN UPDATED ESTIMATE WAS MADE FOR 58N 30W. THE CLOCK WAS OPERATING CORRECTLY ON DEP AND CLB OUT. IT IS SURMISED THAT THE CLOCK STOPPED BECAUSE WHEN THE CAPT'S R FOOT IS ON THE FOOT REST, THE SOLE OF HIS SHOE CAN PHYSICALLY TOUCH THE GMT SET KNOB LOCATED IN THE LOWER R CORNER OF THE CLOCK AND MOVE IT TO 'HOLD' POS. I RECOMMEND A SIMPLE SPRING STEEL GUARD BE AFFIXED TO THE INST PANEL TO COVER THE SET KNOB. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR SAYS THAT NOW THAT HE HAS TALKED TO SEVERAL OTHER PLTS AT HIS ACR HE BELIEVES THAT THE CLOCK VULNERABILITY MAY BE PECULIAR TO THIS PARTICULAR ACFT. IT SEEMS THAT THE FOOT REST BELOW THE INST PANEL ON THIS ACFT IS TOO CLOSE TO THE PANEL AND THIS ALLOWS ONES SHOE TOE TO TOUCH THE CLOCK CTLS AND PERHAPS, AS IN THIS CASE, TO STOP THE CLOCK. THEREFORE, THE RPTR THINKS THAT HIS ACR SHOULD PUT THE STANDARD FOOT REST INTO THIS ACFT AND PREVENT FURTHER SIMILAR OCCURRENCES. THIS ANALYST AGREES.

Data retrieved from NASA's ASRS site as of July 2007 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.