Narrative:

During descent into frankfurt, the altimeters were incorrectly set at 29.99 hg instead of 0999 hp, resulting in frankfurt approach control issuing an altitude alert. The reason I believe this happened is that the ATIS was copied by the relief pilot using 3 digits with a decimal point. Since frankfurt normally issues both hp and hg on the ATIS, I incorrectly assumed that the decimal denoted the hg scale and announced '2999,' and set my altimeter. The first officer did the same. In retrospect, I should have asked for the missing information as a xchk. In the future I will insist that all ATIS information is to be copied, and particularly both altimeter settings. Safety would also be greatly enhanced if ICAO standards were complied with by the controllers -- ie, stating the units when giving the altimeter setting. I also feel that political correctness aside, that 'millibars' is easier to say than 'hectopascals.' also, being a careful, conscientious pilot, I am concerned with the subtlety of this mistake. I believe this could happen to almost any pilot given similar circumstances. I feel that stating units by all concerned would eliminate most of the problem. The industry has carried abbreviation too far. An abbreviation by its very nature requires the user to assume the missing data and fill in the blanks. Therein lies the problem. Not stating the units exacerbates the problem. Reading over this report, it may appear that I am trying to shift blame elsewhere. Nothing could be further from the truth. I will greatly increase my awareness and briefings in this area (which I failed to do on this flight). However, self-criticism will not get to the heart of the problem, which is 2 altimeter settings in this industry. This is the real problem, and the mistake will continue to be made by other pilots until the system is changed or at least the units included in the altimeter setting. I recommend the following phraseology: 'altimeter zero 999 millibars' for hp scale. 'Altimeter 2999 inches' for hg scale.

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Original NASA ASRS Text

Title: ALTDEV -- MISSED ALT.

Narrative: DURING DSCNT INTO FRANKFURT, THE ALTIMETERS WERE INCORRECTLY SET AT 29.99 HG INSTEAD OF 0999 HP, RESULTING IN FRANKFURT APCH CTL ISSUING AN ALT ALERT. THE REASON I BELIEVE THIS HAPPENED IS THAT THE ATIS WAS COPIED BY THE RELIEF PLT USING 3 DIGITS WITH A DECIMAL POINT. SINCE FRANKFURT NORMALLY ISSUES BOTH HP AND HG ON THE ATIS, I INCORRECTLY ASSUMED THAT THE DECIMAL DENOTED THE HG SCALE AND ANNOUNCED '2999,' AND SET MY ALTIMETER. THE FO DID THE SAME. IN RETROSPECT, I SHOULD HAVE ASKED FOR THE MISSING INFO AS A XCHK. IN THE FUTURE I WILL INSIST THAT ALL ATIS INFO IS TO BE COPIED, AND PARTICULARLY BOTH ALTIMETER SETTINGS. SAFETY WOULD ALSO BE GREATLY ENHANCED IF ICAO STANDARDS WERE COMPLIED WITH BY THE CTLRS -- IE, STATING THE UNITS WHEN GIVING THE ALTIMETER SETTING. I ALSO FEEL THAT POLITICAL CORRECTNESS ASIDE, THAT 'MILLIBARS' IS EASIER TO SAY THAN 'HECTOPASCALS.' ALSO, BEING A CAREFUL, CONSCIENTIOUS PLT, I AM CONCERNED WITH THE SUBTLETY OF THIS MISTAKE. I BELIEVE THIS COULD HAPPEN TO ALMOST ANY PLT GIVEN SIMILAR CIRCUMSTANCES. I FEEL THAT STATING UNITS BY ALL CONCERNED WOULD ELIMINATE MOST OF THE PROB. THE INDUSTRY HAS CARRIED ABBREVIATION TOO FAR. AN ABBREVIATION BY ITS VERY NATURE REQUIRES THE USER TO ASSUME THE MISSING DATA AND FILL IN THE BLANKS. THEREIN LIES THE PROB. NOT STATING THE UNITS EXACERBATES THE PROB. READING OVER THIS RPT, IT MAY APPEAR THAT I AM TRYING TO SHIFT BLAME ELSEWHERE. NOTHING COULD BE FURTHER FROM THE TRUTH. I WILL GREATLY INCREASE MY AWARENESS AND BRIEFINGS IN THIS AREA (WHICH I FAILED TO DO ON THIS FLT). HOWEVER, SELF-CRITICISM WILL NOT GET TO THE HEART OF THE PROB, WHICH IS 2 ALTIMETER SETTINGS IN THIS INDUSTRY. THIS IS THE REAL PROB, AND THE MISTAKE WILL CONTINUE TO BE MADE BY OTHER PLTS UNTIL THE SYS IS CHANGED OR AT LEAST THE UNITS INCLUDED IN THE ALTIMETER SETTING. I RECOMMEND THE FOLLOWING PHRASEOLOGY: 'ALTIMETER ZERO 999 MILLIBARS' FOR HP SCALE. 'ALTIMETER 2999 INCHES' FOR HG SCALE.

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.