Light transport business jet encountered severe up and downdrafts.

Attributes
ACN	409250
Time
Date	199807
Day	Mon
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : cae
State Reference	SC
Altitude	msl bound lower : 36000 msl bound upper : 38000
Environment
Flight Conditions	IMC
Light	Dusk
Aircraft 1
Controlling Facilities	artcc : zjx
Operator	general aviation : corporate
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 91
Navigation In Use	Other Other
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : instrument pilot : cfi pilot : atp
Experience	flight time last 90 days : 90 flight time total : 5500 flight time type : 2000
ASRS Report	409250
Person 2
Affiliation	Other
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : weather non adherence : clearance other anomaly
Independent Detector	other flight crewa
Resolutory Action	flight crew : regained aircraft control flight crew : exited adverse environment other
Consequence	Other
Supplementary
Primary Problem	Weather
Air Traffic Incident	other

Narrative:

Inability to maintain altitude and airspeed due to severe up and downdrafts, +/-1000 ft from assigned altitude and +20, and -70 KIAS. Through each subsequent oscillation, the autoplt, flight director, electric pitch trim fell farther behind aircraft. Turned off these system for manual control. Able to maintain +/-100 ft and +/-20 KTS. No radar returns and no reported anomalies in area. Assuming manual control of aircraft helped the situation and I suspect that we had also exited the region of unstable air. Obviously, the crew had little control over the situation and alerted ATC as soon as possible. We also added a PIREP to help others avoid the area. My belief is that we simply flew into an unknown region of unstable air which exceeded the limits of our automated system. In order to keep within the operating envelope we were forced to trade altitude for airspeed.

Original NASA ASRS Text

Title: LTT BUSINESS JET ENCOUNTERED SEVERE UP AND DOWNDRAFTS.

Narrative: INABILITY TO MAINTAIN ALT AND AIRSPD DUE TO SEVERE UP AND DOWNDRAFTS, +/-1000 FT FROM ASSIGNED ALT AND +20, AND -70 KIAS. THROUGH EACH SUBSEQUENT OSCILLATION, THE AUTOPLT, FLT DIRECTOR, ELECTRIC PITCH TRIM FELL FARTHER BEHIND ACFT. TURNED OFF THESE SYS FOR MANUAL CTL. ABLE TO MAINTAIN +/-100 FT AND +/-20 KTS. NO RADAR RETURNS AND NO RPTED ANOMALIES IN AREA. ASSUMING MANUAL CTL OF ACFT HELPED THE SIT AND I SUSPECT THAT WE HAD ALSO EXITED THE REGION OF UNSTABLE AIR. OBVIOUSLY, THE CREW HAD LITTLE CTL OVER THE SIT AND ALERTED ATC ASAP. WE ALSO ADDED A PIREP TO HELP OTHERS AVOID THE AREA. MY BELIEF IS THAT WE SIMPLY FLEW INTO AN UNKNOWN REGION OF UNSTABLE AIR WHICH EXCEEDED THE LIMITS OF OUR AUTOMATED SYS. IN ORDER TO KEEP WITHIN THE OPERATING ENVELOPE WE WERE FORCED TO TRADE ALT FOR AIRSPD.

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.