FA20 altitude excursion from FL410 due to turbulence.

Attributes
ACN	657225
Time
Date	200505
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : den.airport
State Reference	CO
Altitude	msl single value : 41000
Environment
Flight Conditions	IMC
Weather Elements	Thunderstorm Turbulence
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdv.artcc
Operator	general aviation : corporate
Make Model Name	Falcon 20FJF/20C/20D/20E/20F
Operating Under FAR Part	Part 91
Flight Phase	cruise : level ground : maintenance
Flight Plan	IFR
Person 1
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : cfi
Experience	flight time last 90 days : 60 flight time total : 13500 flight time type : 200
ASRS Report	657225
Person 2
Affiliation	company : corporate
Function	flight crew : first officer
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : weather inflight encounter : turbulence
Independent Detector	other flight crewa
Resolutory Action	flight crew : returned to assigned altitude
Supplementary
Problem Areas	Weather FAA
Primary Problem	Weather

Narrative:

I climbed from FL370 to FL410 to get over some thunderstorm activity below and around us. Level at FL410 with autoplt engaged and altitude hold on; I encountered moderate chop. The autoplt started to oscillate on pitch trim until I had to disengage the autoplt. By the time I got the aircraft under pitch control by hand; I was off altitude by 200-300 ft. Turbulence settled down in a couple of mins and I re-engaged the autoplt system. Center (ATC) said nothing. In retrospect; I should have reported the off altitude due to turbulence (mountain wave); etc; in rvsm airspace. In the future when this happens; I will report it. At no time did the altimeters indicate I was under/over 300 ft off assigned altitude; but with the new rvsm rules I should have said something. There was no reported; sighted; or TCASII conflict of traffic during this occurrence.

Original NASA ASRS Text

Title: FA20 ALT EXCURSION FROM FL410 DUE TO TURB.

Narrative: I CLBED FROM FL370 TO FL410 TO GET OVER SOME TSTM ACTIVITY BELOW AND AROUND US. LEVEL AT FL410 WITH AUTOPLT ENGAGED AND ALT HOLD ON; I ENCOUNTERED MODERATE CHOP. THE AUTOPLT STARTED TO OSCILLATE ON PITCH TRIM UNTIL I HAD TO DISENGAGE THE AUTOPLT. BY THE TIME I GOT THE ACFT UNDER PITCH CTL BY HAND; I WAS OFF ALT BY 200-300 FT. TURB SETTLED DOWN IN A COUPLE OF MINS AND I RE-ENGAGED THE AUTOPLT SYS. CTR (ATC) SAID NOTHING. IN RETROSPECT; I SHOULD HAVE RPTED THE OFF ALT DUE TO TURB (MOUNTAIN WAVE); ETC; IN RVSM AIRSPACE. IN THE FUTURE WHEN THIS HAPPENS; I WILL RPT IT. AT NO TIME DID THE ALTIMETERS INDICATE I WAS UNDER/OVER 300 FT OFF ASSIGNED ALT; BUT WITH THE NEW RVSM RULES I SHOULD HAVE SAID SOMETHING. THERE WAS NO RPTED; SIGHTED; OR TCASII CONFLICT OF TFC DURING THIS OCCURRENCE.

Data retrieved from NASA's ASRS site as of January 2009 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.