 |
37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
|
A DC8 freighter diverts to an alternate airport after malfunctions appear in the 3 altimeters and airspeed indicators.
| Attributes | |
| ACN | 424290 |
| Time | |
| Date | 199812 |
| Day | Tue |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : obk |
| State Reference | IL |
| Altitude | msl bound lower : 34000 msl bound upper : 36000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tracon : sav |
| Operator | common carrier : air carrier |
| Make Model Name | DC-8 Undifferentiated or Other Model |
| Flight Phase | cruise other other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Experience | flight time last 90 days : 100 flight time total : 4500 flight time type : 350 |
| ASRS Report | 424290 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Events | |
| Anomaly | aircraft equipment problem : critical other anomaly other |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other flight crewa |
| Resolutory Action | none taken : unable other |
| Consequence | Other |
| Supplementary | |
| Air Traffic Incident | other |
Narrative:
At cruise at FL350 approximately 1 hour into flight first officer's altimeter began fluctuating. As first officer altimeter reached 400 ft low, control of autoplt was switched to the captain's side. Captain's altimeter showed still level at FL350. It was then noticed that the standby altimeter was reading 300 ft high. Over the course of the next 45 mins the first officer's altimeter fluctuated from 1000 ft to +300 ft. Standby altimeter climbed to +800 ft. At this point we were not sure which of our 3 altimeters was correct but we believed it to be the captain's. We advised ATC of our problem. Then the captain's altimeter began to fluctuate like, but not in the same direction as, the first officer's. At this point unsure of which altimeter was reliable but now believing the standby to be correct and in VFR WX we chose to divert to dsm. It is very confusing to have 3 separate altimeters spread by 2000 ft (34000, 35000 and 36000 ft). The aircraft had been deiced with type 1 and anti-iced with 100/90 type 4 ultra prior to takeoff. In addition, airspds on the 3 air data computers (reporter means 'on the 3 airspeed indicators') were also separated by approximately 30 KTS.
Original NASA ASRS Text
Title: A DC8 FREIGHTER DIVERTS TO AN ALTERNATE ARPT AFTER MALFUNCTIONS APPEAR IN THE 3 ALTIMETERS AND AIRSPD INDICATORS.
Narrative: AT CRUISE AT FL350 APPROX 1 HR INTO FLT FO'S ALTIMETER BEGAN FLUCTUATING. AS FO ALTIMETER REACHED 400 FT LOW, CTL OF AUTOPLT WAS SWITCHED TO THE CAPT'S SIDE. CAPT'S ALTIMETER SHOWED STILL LEVEL AT FL350. IT WAS THEN NOTICED THAT THE STANDBY ALTIMETER WAS READING 300 FT HIGH. OVER THE COURSE OF THE NEXT 45 MINS THE FO'S ALTIMETER FLUCTUATED FROM 1000 FT TO +300 FT. STANDBY ALTIMETER CLBED TO +800 FT. AT THIS POINT WE WERE NOT SURE WHICH OF OUR 3 ALTIMETERS WAS CORRECT BUT WE BELIEVED IT TO BE THE CAPT'S. WE ADVISED ATC OF OUR PROB. THEN THE CAPT'S ALTIMETER BEGAN TO FLUCTUATE LIKE, BUT NOT IN THE SAME DIRECTION AS, THE FO'S. AT THIS POINT UNSURE OF WHICH ALTIMETER WAS RELIABLE BUT NOW BELIEVING THE STANDBY TO BE CORRECT AND IN VFR WX WE CHOSE TO DIVERT TO DSM. IT IS VERY CONFUSING TO HAVE 3 SEPARATE ALTIMETERS SPREAD BY 2000 FT (34000, 35000 AND 36000 FT). THE ACFT HAD BEEN DEICED WITH TYPE 1 AND ANTI-ICED WITH 100/90 TYPE 4 ULTRA PRIOR TO TKOF. IN ADDITION, AIRSPDS ON THE 3 AIR DATA COMPUTERS (RPTR MEANS 'ON THE 3 AIRSPD INDICATORS') WERE ALSO SEPARATED BY APPROX 30 KTS.
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.