 |
37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
|
Pilot of an atx C421, descended below assigned altitude after switching fuel tanks on the left engine during cruise. ARTCC radar controller inquired of his altitude and the reporter noticed he had lost 500 ft and found the autoplt altitude hold not engaged, but indicating it was.
| Attributes | |
| ACN | 400940 |
| Time | |
| Date | 199804 |
| Day | Fri |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | atc facility : uin |
| State Reference | IL |
| Altitude | msl bound lower : 16500 msl bound upper : 17000 |
| Environment | |
| Flight Conditions | Marginal |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tower : sfo |
| Operator | common carrier : air taxi |
| Make Model Name | Golden Eagle 421 |
| Operating Under FAR Part | Part 135 |
| Flight Phase | climbout : intermediate altitude |
| Route In Use | enroute airway : zkc |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air taxi |
| Function | flight crew : single pilot |
| Qualification | other other : other pilot : instrument pilot : atp pilot : cfi |
| Experience | flight time last 90 days : 200 flight time total : 4030 flight time type : 700 |
| ASRS Report | 400940 |
| Person 2 | |
| Affiliation | government : faa |
| Function | controller : radar |
| Qualification | controller : radar |
| Events | |
| Anomaly | aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other |
| Independent Detector | other controllera |
| Resolutory Action | flight crew : returned to intended course or assigned course |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | Pilot Deviation |
Narrative:
Upon switching fuel tanks on the left engine, the left engine lost some power. For a few seconds, after the engine went back to normal operations, I went back to reading the instrument charts, while everything appeared working properly, and the autoplt was flying the airplane. Shortly after that, I was warned from ZKC to check my altitude. When I did that, my altimeter showed 16500 ft instead of 17000 ft. The autoplt still showed the green light to the altitude mode. I believe that upon switching tanks, due to the vibration of the left engine, the autoplt got disengaged, without however, giving any warning (the green light to the altitude mode should have changed to white). After being warned from ZKC I went immediately back to 17000 ft and I believe there was no traffic conflict at that time. I believe pilots need to be warned of how old cessna autoplts are and they may be unreliable.
Original NASA ASRS Text
Title: PLT OF AN ATX C421, DSNDED BELOW ASSIGNED ALT AFTER SWITCHING FUEL TANKS ON THE L ENG DURING CRUISE. ARTCC RADAR CTLR INQUIRED OF HIS ALT AND THE RPTR NOTICED HE HAD LOST 500 FT AND FOUND THE AUTOPLT ALT HOLD NOT ENGAGED, BUT INDICATING IT WAS.
Narrative: UPON SWITCHING FUEL TANKS ON THE L ENG, THE L ENG LOST SOME PWR. FOR A FEW SECONDS, AFTER THE ENG WENT BACK TO NORMAL OPS, I WENT BACK TO READING THE INST CHARTS, WHILE EVERYTHING APPEARED WORKING PROPERLY, AND THE AUTOPLT WAS FLYING THE AIRPLANE. SHORTLY AFTER THAT, I WAS WARNED FROM ZKC TO CHK MY ALT. WHEN I DID THAT, MY ALTIMETER SHOWED 16500 FT INSTEAD OF 17000 FT. THE AUTOPLT STILL SHOWED THE GREEN LIGHT TO THE ALT MODE. I BELIEVE THAT UPON SWITCHING TANKS, DUE TO THE VIBRATION OF THE L ENG, THE AUTOPLT GOT DISENGAGED, WITHOUT HOWEVER, GIVING ANY WARNING (THE GREEN LIGHT TO THE ALT MODE SHOULD HAVE CHANGED TO WHITE). AFTER BEING WARNED FROM ZKC I WENT IMMEDIATELY BACK TO 17000 FT AND I BELIEVE THERE WAS NO TFC CONFLICT AT THAT TIME. I BELIEVE PLTS NEED TO BE WARNED OF HOW OLD CESSNA AUTOPLTS ARE AND THEY MAY BE UNRELIABLE.
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.