Narrative:

After all before takeoff checklists were completed, flight departed lex runway 3. Turn to the north was initiated while climbing to filed altitude of 10000 ft. As autoplt began to capture altitude on first officer's instruments, captain realized a discrepancy in altimeter settings. At that moment lex departure also called to question altitude. First officer's altimeter was corrected and descent was immediately executed to correct altitude. Lex supervisor was contacted via telephone on ground after arrival to cvg. Occurrence was caused by an uncommanded change of altimeter setting on first officer side from 30.27 inches to 29.35 inches. Aircraft is equipped with EFIS system. Upon discussion with company avionics department, captain and first officer were told that this occurrence has happened before and is possible due to moisture or electronic spikes. The event was duplicated on the ground in cvg. Supervisor at lex departure responded that he was 'satisfied on his end' and that no problems had risen. This is the first I had seen this problem with an electronic altimeter, although I since have heard of others having the same problem. I suggest change in checklist for altimeter xchks after second generator comes on line. This will alleviate the electronic problem but manufacturer should address the moisture problems. Callback conversation with reporter revealed the following information: reporter states the aircraft is the canadair regional carrier. It is an all electronic aircraft and when the last of the generators comes on line it puts a spike on the line and this causes the problem in altimeter. It seems to be always on the first officer side and the altimeter always goes high. Reporter's company has put out an operations note but has not made any checklist changes. This is important to the reporter and he also feels the training department should teach about the problem in ground school. Company appears to be working with manufacturer of the aircraft and with collins to attempt to solve the problem but reporter feels not enough has been done to alert the pilots to frequently xchking the altimeters. Reporter is also concerned because lex tower controller said no problem but indicated he had called another facility.

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Original NASA ASRS Text

Title: REGIONAL JET ACFT HAS ALTIMETER CHANGE UNCOMMANDED. ALTDEV RESULTS.

Narrative: AFTER ALL BEFORE TKOF CHKLISTS WERE COMPLETED, FLT DEPARTED LEX RWY 3. TURN TO THE N WAS INITIATED WHILE CLBING TO FILED ALT OF 10000 FT. AS AUTOPLT BEGAN TO CAPTURE ALT ON FO'S INSTS, CAPT REALIZED A DISCREPANCY IN ALTIMETER SETTINGS. AT THAT MOMENT LEX DEP ALSO CALLED TO QUESTION ALT. FO'S ALTIMETER WAS CORRECTED AND DSCNT WAS IMMEDIATELY EXECUTED TO CORRECT ALT. LEX SUPVR WAS CONTACTED VIA TELEPHONE ON GND AFTER ARR TO CVG. OCCURRENCE WAS CAUSED BY AN UNCOMMANDED CHANGE OF ALTIMETER SETTING ON FO SIDE FROM 30.27 INCHES TO 29.35 INCHES. ACFT IS EQUIPPED WITH EFIS SYS. UPON DISCUSSION WITH COMPANY AVIONICS DEPT, CAPT AND FO WERE TOLD THAT THIS OCCURRENCE HAS HAPPENED BEFORE AND IS POSSIBLE DUE TO MOISTURE OR ELECTRONIC SPIKES. THE EVENT WAS DUPLICATED ON THE GND IN CVG. SUPVR AT LEX DEP RESPONDED THAT HE WAS 'SATISFIED ON HIS END' AND THAT NO PROBS HAD RISEN. THIS IS THE FIRST I HAD SEEN THIS PROB WITH AN ELECTRONIC ALTIMETER, ALTHOUGH I SINCE HAVE HEARD OF OTHERS HAVING THE SAME PROB. I SUGGEST CHANGE IN CHKLIST FOR ALTIMETER XCHKS AFTER SECOND GENERATOR COMES ON LINE. THIS WILL ALLEVIATE THE ELECTRONIC PROB BUT MANUFACTURER SHOULD ADDRESS THE MOISTURE PROBS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THE ACFT IS THE CANADAIR REGIONAL CARRIER. IT IS AN ALL ELECTRONIC ACFT AND WHEN THE LAST OF THE GENERATORS COMES ON LINE IT PUTS A SPIKE ON THE LINE AND THIS CAUSES THE PROB IN ALTIMETER. IT SEEMS TO BE ALWAYS ON THE FO SIDE AND THE ALTIMETER ALWAYS GOES HIGH. RPTR'S COMPANY HAS PUT OUT AN OPS NOTE BUT HAS NOT MADE ANY CHKLIST CHANGES. THIS IS IMPORTANT TO THE RPTR AND HE ALSO FEELS THE TRAINING DEPT SHOULD TEACH ABOUT THE PROB IN GND SCHOOL. COMPANY APPEARS TO BE WORKING WITH MANUFACTURER OF THE ACFT AND WITH COLLINS TO ATTEMPT TO SOLVE THE PROB BUT RPTR FEELS NOT ENOUGH HAS BEEN DONE TO ALERT THE PLTS TO FREQUENTLY XCHKING THE ALTIMETERS. RPTR IS ALSO CONCERNED BECAUSE LEX TWR CTLR SAID NO PROB BUT INDICATED HE HAD CALLED ANOTHER FACILITY.

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.