Narrative:

I feel I am being harassed by air carrier X to accept aircraft with maintenance discrepancies. Over my last 3, 3-DAY trips, I have been charged with crew delays for items that were maintenance related. Captain stated altitude at 540 ft, and chart company showed ramp altitude at 488 ft. Airport altitude is published at 542 ft. All maintenance checks ok change aircraft. I flew flight into austin on schedule with only 42 mins of scheduled ground time before I was to fly another flight back to dfw. Our changeover request showed we were to change aircraft in aus. I called ahead to aus operations and questioned this move to a new aircraft. They had no reason for the change. I told them to have the agent pull up aus departure flight paperwork for me to minimize my time on the ground in aus. After landing, I secured my aircraft and rushed over to the new gate. My first officer reported to me that not only was this an aircraft change, but the new aircraft had not been flown that day, and thus, an origination preflight was required. The 2 of us completed the complete origination preflight as rapidly as possible. I noted the captain's, first officer's, and standby altimeters were all 3 reading high by about 50 ft. Normally, this means the barometer has changed since the ATIS was set up. I called the tower for the most current barometric setting. It was the same as the ATIS. The instrument tolerances are listed in the air carrier X DC9 operating manual, in the system section. I quote: field elevation, ft MSL, tolerance, 2000 ft MSL, pilots (CADC), altimeters 30/40, standby altimeter 20/50 -- these tolerances take into account the height of the altimeter sensing device above the ground. As published, field elevation is the highest point on usable surface runways -- allowance should be made for any difference in elevation of ramp or point at which check is made. The operation manual further states 'if any altimeter is not within limits specified above, it must be entered in log and requires corrective action prior to takeoff.' the airport elevation on company X's chart for kaus gives airport elevation as 542 ft MSL. That point is at the approach end of runway 17R. The closest point to the ramp chart company reported is the approach end of runway 17L at 491 ft MSL. The airport continues to slope downward slightly to the lowest point of 473 ft MSL at the southern end of runway 17L. The air carrier X official flight manual for aus publishes the ramp elevation as 488 ft MSL. That officially reported height is consistent with the 491 ft at the end of runway 17L, and is reasonable. Since the actual ramp elevation is published, this check of various airfield elevations is not necessary, but is included to show the reasonableness of the officially published 488 ft. The standby altimeter was reading just a little short of 540 ft MSL. It appeared to be barely within the -50 ft tolerance specified in the operation manual. Both the captain's and the first officer's CADC driven altimeters were reading higher still. I do not have the log in front of me now, but I remember that both were reading about 55 ft high, or out of tolerance by 15 ft. Since all 3 altimeters are driven by 3 separate system, I found it suspect that all 3 were about 50 ft too high. A call was made to maintenance controller so the mechanics and I could get a feel for how to proceed. Maintenance controller simply said that since all 3 were on separate system, and since all 3 were almost uniformly 50 ft high, the published 488 ft elevation must be wrong and the altimeters must be right. This answer, although logical, did not seem prudent to me to accept. I went over to the aircraft I had just flown in from dfw and looked at the 3 altimeters in it. With the most current barometer settings I found that the 2 CADC driver altimeters, the captain's and first officer's both read 490 ft MSL, and the standby altimeter read about 500 ft -- a little high, but well within tolerance. From my investigation, I found the 488 ft ramp elevation officially published by air carrier X to be correct and reasonable, and the explanation by maintenance controller to be unreasonable. I pointed out to the air carrier X mechanics that the altimeters on the airplane we brought in were correct and matched the published ramp elevation. We weregiven permission to remove the passenger from the aircraft in question and place them on the working aircraft. We then got a new flight plan and completed all required checks of the aircraft and departed aus. From the message to me quoted above, it appears maintenance said the aircraft was within limits. Based on the official DC9 operating manual and the official air carrier X, it is absolutely crystal clear that for whatever reason the aircraft in question had all 3 altimeters reading at least 50 ft too high, and that 2 of them were out of tolerance. I hope it wasn't flown with that write-off in the log.

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Original NASA ASRS Text

Title: MD80 CAPT FOUND ACFT ALTIMETERS THAT WERE NOT WITHIN MANUAL TOLERANCES AT AUS.

Narrative: I FEEL I AM BEING HARASSED BY ACR X TO ACCEPT ACFT WITH MAINT DISCREPANCIES. OVER MY LAST 3, 3-DAY TRIPS, I HAVE BEEN CHARGED WITH CREW DELAYS FOR ITEMS THAT WERE MAINT RELATED. CAPT STATED ALT AT 540 FT, AND CHART COMPANY SHOWED RAMP ALT AT 488 FT. ARPT ALT IS PUBLISHED AT 542 FT. ALL MAINT CHKS OK CHANGE ACFT. I FLEW FLT INTO AUSTIN ON SCHEDULE WITH ONLY 42 MINS OF SCHEDULED GND TIME BEFORE I WAS TO FLY ANOTHER FLT BACK TO DFW. OUR CHANGEOVER REQUEST SHOWED WE WERE TO CHANGE ACFT IN AUS. I CALLED AHEAD TO AUS OPS AND QUESTIONED THIS MOVE TO A NEW ACFT. THEY HAD NO REASON FOR THE CHANGE. I TOLD THEM TO HAVE THE AGENT PULL UP AUS DEP FLT PAPERWORK FOR ME TO MINIMIZE MY TIME ON THE GND IN AUS. AFTER LNDG, I SECURED MY ACFT AND RUSHED OVER TO THE NEW GATE. MY FO RPTED TO ME THAT NOT ONLY WAS THIS AN ACFT CHANGE, BUT THE NEW ACFT HAD NOT BEEN FLOWN THAT DAY, AND THUS, AN ORIGINATION PREFLT WAS REQUIRED. THE 2 OF US COMPLETED THE COMPLETE ORIGINATION PREFLT AS RAPIDLY AS POSSIBLE. I NOTED THE CAPT'S, FO'S, AND STANDBY ALTIMETERS WERE ALL 3 READING HIGH BY ABOUT 50 FT. NORMALLY, THIS MEANS THE BAROMETER HAS CHANGED SINCE THE ATIS WAS SET UP. I CALLED THE TWR FOR THE MOST CURRENT BAROMETRIC SETTING. IT WAS THE SAME AS THE ATIS. THE INST TOLERANCES ARE LISTED IN THE ACR X DC9 OPERATING MANUAL, IN THE SYS SECTION. I QUOTE: FIELD ELEVATION, FT MSL, TOLERANCE, 2000 FT MSL, PLTS (CADC), ALTIMETERS 30/40, STANDBY ALTIMETER 20/50 -- THESE TOLERANCES TAKE INTO ACCOUNT THE HEIGHT OF THE ALTIMETER SENSING DEVICE ABOVE THE GND. AS PUBLISHED, FIELD ELEVATION IS THE HIGHEST POINT ON USABLE SURFACE RWYS -- ALLOWANCE SHOULD BE MADE FOR ANY DIFFERENCE IN ELEVATION OF RAMP OR POINT AT WHICH CHK IS MADE. THE OP MANUAL FURTHER STATES 'IF ANY ALTIMETER IS NOT WITHIN LIMITS SPECIFIED ABOVE, IT MUST BE ENTERED IN LOG AND REQUIRES CORRECTIVE ACTION PRIOR TO TKOF.' THE ARPT ELEVATION ON COMPANY X'S CHART FOR KAUS GIVES ARPT ELEVATION AS 542 FT MSL. THAT POINT IS AT THE APCH END OF RWY 17R. THE CLOSEST POINT TO THE RAMP CHART COMPANY RPTED IS THE APCH END OF RWY 17L AT 491 FT MSL. THE ARPT CONTINUES TO SLOPE DOWNWARD SLIGHTLY TO THE LOWEST POINT OF 473 FT MSL AT THE SOUTHERN END OF RWY 17L. THE ACR X OFFICIAL FLT MANUAL FOR AUS PUBLISHES THE RAMP ELEVATION AS 488 FT MSL. THAT OFFICIALLY RPTED HEIGHT IS CONSISTENT WITH THE 491 FT AT THE END OF RWY 17L, AND IS REASONABLE. SINCE THE ACTUAL RAMP ELEVATION IS PUBLISHED, THIS CHK OF VARIOUS AIRFIELD ELEVATIONS IS NOT NECESSARY, BUT IS INCLUDED TO SHOW THE REASONABLENESS OF THE OFFICIALLY PUBLISHED 488 FT. THE STANDBY ALTIMETER WAS READING JUST A LITTLE SHORT OF 540 FT MSL. IT APPEARED TO BE BARELY WITHIN THE -50 FT TOLERANCE SPECIFIED IN THE OP MANUAL. BOTH THE CAPT'S AND THE FO'S CADC DRIVEN ALTIMETERS WERE READING HIGHER STILL. I DO NOT HAVE THE LOG IN FRONT OF ME NOW, BUT I REMEMBER THAT BOTH WERE READING ABOUT 55 FT HIGH, OR OUT OF TOLERANCE BY 15 FT. SINCE ALL 3 ALTIMETERS ARE DRIVEN BY 3 SEPARATE SYS, I FOUND IT SUSPECT THAT ALL 3 WERE ABOUT 50 FT TOO HIGH. A CALL WAS MADE TO MAINT CTLR SO THE MECHS AND I COULD GET A FEEL FOR HOW TO PROCEED. MAINT CTLR SIMPLY SAID THAT SINCE ALL 3 WERE ON SEPARATE SYS, AND SINCE ALL 3 WERE ALMOST UNIFORMLY 50 FT HIGH, THE PUBLISHED 488 FT ELEVATION MUST BE WRONG AND THE ALTIMETERS MUST BE RIGHT. THIS ANSWER, ALTHOUGH LOGICAL, DID NOT SEEM PRUDENT TO ME TO ACCEPT. I WENT OVER TO THE ACFT I HAD JUST FLOWN IN FROM DFW AND LOOKED AT THE 3 ALTIMETERS IN IT. WITH THE MOST CURRENT BAROMETER SETTINGS I FOUND THAT THE 2 CADC DRIVER ALTIMETERS, THE CAPT'S AND FO'S BOTH READ 490 FT MSL, AND THE STANDBY ALTIMETER READ ABOUT 500 FT -- A LITTLE HIGH, BUT WELL WITHIN TOLERANCE. FROM MY INVESTIGATION, I FOUND THE 488 FT RAMP ELEVATION OFFICIALLY PUBLISHED BY ACR X TO BE CORRECT AND REASONABLE, AND THE EXPLANATION BY MAINT CTLR TO BE UNREASONABLE. I POINTED OUT TO THE ACR X MECHS THAT THE ALTIMETERS ON THE AIRPLANE WE BROUGHT IN WERE CORRECT AND MATCHED THE PUBLISHED RAMP ELEVATION. WE WEREGIVEN PERMISSION TO REMOVE THE PAX FROM THE ACFT IN QUESTION AND PLACE THEM ON THE WORKING ACFT. WE THEN GOT A NEW FLT PLAN AND COMPLETED ALL REQUIRED CHKS OF THE ACFT AND DEPARTED AUS. FROM THE MESSAGE TO ME QUOTED ABOVE, IT APPEARS MAINT SAID THE ACFT WAS WITHIN LIMITS. BASED ON THE OFFICIAL DC9 OPERATING MANUAL AND THE OFFICIAL ACR X, IT IS ABSOLUTELY CRYSTAL CLR THAT FOR WHATEVER REASON THE ACFT IN QUESTION HAD ALL 3 ALTIMETERS READING AT LEAST 50 FT TOO HIGH, AND THAT 2 OF THEM WERE OUT OF TOLERANCE. I HOPE IT WASN'T FLOWN WITH THAT WRITE-OFF IN THE LOG.

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.