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A cpr PA31 pilot encounters a thunderstorm and the associated turbulence causes him to descend briefly below his assigned altitude. The excursion was noted by an ARTCC controller.
| Attributes | |
| ACN | 431875 |
| Time | |
| Date | 199902 |
| Day | Wed |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | navaid : atl.vortac |
| State Reference | GA |
| Altitude | msl bound lower : 4550 msl bound upper : 5000 |
| Environment | |
| Weather Elements | Thunderstorm Rain Turbulence |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tower : atl.tower |
| Person 1 | |
| Affiliation | company : corporate |
| Function | flight crew : single pilot |
| Qualification | pilot : multi engine pilot : commercial pilot : instrument |
| Experience | flight time last 90 days : 180 flight time total : 8500 flight time type : 5000 |
| ASRS Report | 431875 |
| Person 2 | |
| Affiliation | government : faa |
| Function | controller : radar |
| Qualification | controller : radar |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude inflight encounter : weather inflight encounter : turbulence non adherence : far non adherence : clearance |
| Independent Detector | other controllera other flight crewa |
| Resolutory Action | controller : issued advisory flight crew : returned to original clearance |
| Consequence | other |
| Supplementary | |
| Problem Areas | Flight Crew Human Performance Weather |
| Primary Problem | Weather |
| Air Traffic Incident | Pilot Deviation |
Narrative:
I was cruising at assigned altitude of 5000 ft MSL IFR. ZTL was very busy due to traffic and WX. As I approached a thunderstorm, I began to encounter turbulence. I turned off the autoplt in order to maintain altitude. I encountered a downdraft, slow at first. I was unable to maintain altitude. Since ZTL was so busy, I couldn't contact them to explain my situation. After losing approximately 450 ft altitude, ZTL asked my altitude. At this time the aircraft was slowing its descent. I encountered an updraft (1000-1500 FPM) and returned to 5000 ft assigned altitude. I was asked to call ZTL by peachtree ground control on landing. I don't know how to prevent this type of incident. Callback conversation with reporter revealed the following information: the pilot said that he has not heard from the FAA, but he does not know what else he could have done. The turbulence was too strong for him to maintain his altitude within normal tolerances and the frequency was too congested for him to advise ARTCC of his problem before the controller noticed his altitude excursion on his radar.
Original NASA ASRS Text
Title: A CPR PA31 PLT ENCOUNTERS A TSTM AND THE ASSOCIATED TURB CAUSES HIM TO DSND BRIEFLY BELOW HIS ASSIGNED ALT. THE EXCURSION WAS NOTED BY AN ARTCC CTLR.
Narrative: I WAS CRUISING AT ASSIGNED ALT OF 5000 FT MSL IFR. ZTL WAS VERY BUSY DUE TO TFC AND WX. AS I APCHED A TSTM, I BEGAN TO ENCOUNTER TURB. I TURNED OFF THE AUTOPLT IN ORDER TO MAINTAIN ALT. I ENCOUNTERED A DOWNDRAFT, SLOW AT FIRST. I WAS UNABLE TO MAINTAIN ALT. SINCE ZTL WAS SO BUSY, I COULDN'T CONTACT THEM TO EXPLAIN MY SIT. AFTER LOSING APPROX 450 FT ALT, ZTL ASKED MY ALT. AT THIS TIME THE ACFT WAS SLOWING ITS DSCNT. I ENCOUNTERED AN UPDRAFT (1000-1500 FPM) AND RETURNED TO 5000 FT ASSIGNED ALT. I WAS ASKED TO CALL ZTL BY PEACHTREE GND CTL ON LNDG. I DON'T KNOW HOW TO PREVENT THIS TYPE OF INCIDENT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE PLT SAID THAT HE HAS NOT HEARD FROM THE FAA, BUT HE DOES NOT KNOW WHAT ELSE HE COULD HAVE DONE. THE TURB WAS TOO STRONG FOR HIM TO MAINTAIN HIS ALT WITHIN NORMAL TOLERANCES AND THE FREQ WAS TOO CONGESTED FOR HIM TO ADVISE ARTCC OF HIS PROB BEFORE THE CTLR NOTICED HIS ALT EXCURSION ON HIS RADAR.
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.