Altitude deviation altitude overshot by the flight crew of a B737-800 during descent after experienc...

Attributes
ACN	608636
Time
Date	200402
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : pie.vortac
State Reference	FL
Altitude	msl bound lower : 28400 msl bound upper : 29000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zjx.artcc
Operator	common carrier : air carrier
Make Model Name	B737-800
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : flight engineer pilot : commercial pilot : cfi pilot : atp pilot : multi engine
Experience	flight time last 90 days : 180 flight time total : 9800 flight time type : 4400
ASRS Report	608636
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	aircraft equipment problem : critical altitude deviation : overshoot inflight encounter : turbulence non adherence : clearance other anomaly other
Independent Detector	atc equipment other atc equipment : mode c aircraft equipment other aircraft equipment : cdw other controllera
Resolutory Action	controller : issued advisory flight crew : overrode automation flight crew : returned to assigned altitude flight crew : overcame equipment problem
Consequence	faa : reviewed incident with flight crew other other
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation
Situations
Publication	EFIS Failured Chklist

Narrative:

During cruise at FL350 we received an 'indicated airspeed disagreement' light on the CDU. It was noted and verified by xchking the standby airspeed against the captain's and first officer's airspeed that the captain's airspeed was the incorrect one (+/-5-10 KTS). The captain assured I was flying the aircraft, and then called our maintenance control via cockpit air phone to troubleshoot the problem. (We had previously accomplished the 'indicated airspeed disagreement' and 'airspeed unreliable' checklists.) while on the phone, we began to encounter moderate turbulence at FL350. It was determined that we should try and descend to a lower flight level that was smoother. I called ZJX and we were given clearance to descend to FL290. I initiated the descent using the autoplt in level change mode. While descending through approximately FL330, I experienced a loss of the first officer's airspeed indicator and altimeter followed by a loss of my map display and a 'single FMC operation' annunciation on the FMC. At this point, I disconnected the autoplt and began to hand fly the aircraft. I shallowed the descent rate and tuned pie VOR into the #2 VHF navigation as a manual backup for the captain's map display. The captain saw what was occurring and asked if I needed his assistance. The conditions were VMC and the situation with the descent and navigation appeared stabilized, so I told him I was ok. He continued to troubleshoot our problems with maintenance and I continued to fly the aircraft. For the descent I was utilizing the captain's side instrument display. I crosschecked the standby airspeed indicator against the captain's airspeed indicator to ensure I was flying a safe airspeed. I was using the captain's altimeter for altitude reference, because it is more easily readable than the standby display. There was also no reason to think it inaccurate since we had crosschecked it at FL350 against the standby and first officer's side and found it to be alright. Leveling at FL290, I actually overshot by 100 ft to FL289. ZJX called and told us to maintain FL290. I corrected to FL290. ZJX called again and told us to maintain FL290. At this point, I thought something might be wrong and crosschecked the captain's altimeter against the standby altimeter and found the standby at FL284. I then flew the aircraft to FL290 on the standby altimeter. Before we were handed to the next controller we verified that jax showed us at FL290. They confirmed that they did and we informed them of our instrumentation problem. We repeated this process with the next controller as well. During the remainder of the flight we were able to restore the first officer's instrument displays and restore dual FMC operation. If I were to do this over, I would have asked the captain to discontinue the troubleshooting call with maintenance, and had him back me up. I also would have disregarded the captain's instrument display, and flown the aircraft purely by the standby airspeed indicator and standby altimeter.

Original NASA ASRS Text

Title: ALTDEV ALT OVERSHOT BY THE FLT CREW OF A B737-800 DURING DSCNT AFTER EXPERIENCING AN 'INDICATED AIRSPD DISAGREEMENT' PROB WITH THEIR EFIS SYS ON FREQ WITH ZJX, FL.

Narrative: DURING CRUISE AT FL350 WE RECEIVED AN 'INDICATED AIRSPD DISAGREEMENT' LIGHT ON THE CDU. IT WAS NOTED AND VERIFIED BY XCHKING THE STANDBY AIRSPD AGAINST THE CAPT'S AND FO'S AIRSPD THAT THE CAPT'S AIRSPD WAS THE INCORRECT ONE (+/-5-10 KTS). THE CAPT ASSURED I WAS FLYING THE ACFT, AND THEN CALLED OUR MAINT CTL VIA COCKPIT AIR PHONE TO TROUBLESHOOT THE PROB. (WE HAD PREVIOUSLY ACCOMPLISHED THE 'INDICATED AIRSPD DISAGREEMENT' AND 'AIRSPD UNRELIABLE' CHKLISTS.) WHILE ON THE PHONE, WE BEGAN TO ENCOUNTER MODERATE TURB AT FL350. IT WAS DETERMINED THAT WE SHOULD TRY AND DSND TO A LOWER FLT LEVEL THAT WAS SMOOTHER. I CALLED ZJX AND WE WERE GIVEN CLRNC TO DSND TO FL290. I INITIATED THE DSCNT USING THE AUTOPLT IN LEVEL CHANGE MODE. WHILE DSNDING THROUGH APPROX FL330, I EXPERIENCED A LOSS OF THE FO'S AIRSPD INDICATOR AND ALTIMETER FOLLOWED BY A LOSS OF MY MAP DISPLAY AND A 'SINGLE FMC OP' ANNUNCIATION ON THE FMC. AT THIS POINT, I DISCONNECTED THE AUTOPLT AND BEGAN TO HAND FLY THE ACFT. I SHALLOWED THE DSCNT RATE AND TUNED PIE VOR INTO THE #2 VHF NAV AS A MANUAL BACKUP FOR THE CAPT'S MAP DISPLAY. THE CAPT SAW WHAT WAS OCCURRING AND ASKED IF I NEEDED HIS ASSISTANCE. THE CONDITIONS WERE VMC AND THE SIT WITH THE DSCNT AND NAV APPEARED STABILIZED, SO I TOLD HIM I WAS OK. HE CONTINUED TO TROUBLESHOOT OUR PROBS WITH MAINT AND I CONTINUED TO FLY THE ACFT. FOR THE DSCNT I WAS UTILIZING THE CAPT'S SIDE INST DISPLAY. I XCHKED THE STANDBY AIRSPD INDICATOR AGAINST THE CAPT'S AIRSPD INDICATOR TO ENSURE I WAS FLYING A SAFE AIRSPD. I WAS USING THE CAPT'S ALTIMETER FOR ALT REF, BECAUSE IT IS MORE EASILY READABLE THAN THE STANDBY DISPLAY. THERE WAS ALSO NO REASON TO THINK IT INACCURATE SINCE WE HAD XCHKED IT AT FL350 AGAINST THE STANDBY AND FO'S SIDE AND FOUND IT TO BE ALRIGHT. LEVELING AT FL290, I ACTUALLY OVERSHOT BY 100 FT TO FL289. ZJX CALLED AND TOLD US TO MAINTAIN FL290. I CORRECTED TO FL290. ZJX CALLED AGAIN AND TOLD US TO MAINTAIN FL290. AT THIS POINT, I THOUGHT SOMETHING MIGHT BE WRONG AND XCHKED THE CAPT'S ALTIMETER AGAINST THE STANDBY ALTIMETER AND FOUND THE STANDBY AT FL284. I THEN FLEW THE ACFT TO FL290 ON THE STANDBY ALTIMETER. BEFORE WE WERE HANDED TO THE NEXT CTLR WE VERIFIED THAT JAX SHOWED US AT FL290. THEY CONFIRMED THAT THEY DID AND WE INFORMED THEM OF OUR INSTRUMENTATION PROB. WE REPEATED THIS PROCESS WITH THE NEXT CTLR AS WELL. DURING THE REMAINDER OF THE FLT WE WERE ABLE TO RESTORE THE FO'S INST DISPLAYS AND RESTORE DUAL FMC OP. IF I WERE TO DO THIS OVER, I WOULD HAVE ASKED THE CAPT TO DISCONTINUE THE TROUBLESHOOTING CALL WITH MAINT, AND HAD HIM BACK ME UP. I ALSO WOULD HAVE DISREGARDED THE CAPT'S INST DISPLAY, AND FLOWN THE ACFT PURELY BY THE STANDBY AIRSPD INDICATOR AND STANDBY ALTIMETER.

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.

Altitude deviation altitude overshot by the flight crew of a B737-800 during descent after experiencing an 'indicated airspeed disagreement' problem with their EFIS system on frequency with ZJX, fl.