<< >> NASA ASRS Report 437522, May 1999

Convective WX activity causes small aircraft pilot to cancel IFR after he or she is unable to maintain assigned altitude.

Attributes
ACN	437522
Time
Date	199905
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : txc.vortac
State Reference	CO
Altitude	msl bound lower : 7000 msl bound upper : 9000
Environment
Flight Conditions	Mixed
Weather Elements	Thunderstorm Turbulence Rain
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdv.artcc
Operator	general aviation : personal
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Route In Use	enroute airway : ns.airway
Flight Plan	IFR Combined VFR
Person 1
Affiliation	other
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : commercial
Experience	flight time last 90 days : 39 flight time total : 1026 flight time type : 316
ASRS Report	437522
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : turbulence inflight encounter : weather non adherence : far non adherence : clearance other anomaly
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance flight crew : exited adverse environment
Supplementary
Problem Areas	Weather Flight Crew Human Performance
Primary Problem	Weather

Narrative:

Flying IFR in IMC near txc at 9000 ft MSL heading approximately 220 degrees. Altitude was assigned by ATC. Picked up lightning on stormscope and requested deviation to left towards some breaks in the clouds. Entered moderate turbulence and substantial downdrafts. Unable to maintain assigned altitude and descended to 7000 ft. Minimum en route altitude 7200 ft. I was told by ATC that I would need to climb to 10000 ft. I climbed to 8500 ft with difficulty but broke out to VMC. I told ATC that I could maintain visual separation from the ground. I was told that I must climb to 10000 ft to stay IFR. But this would put me deep into black storm clouds. I canceled IFR and proceeded in marginal VMC to destination. If I was unable to maintain VMC it would have been necessary to climb into thickening thunderstorm clouds.

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Original NASA ASRS Text

Title: CONVECTIVE WX ACTIVITY CAUSES SMA PLT TO CANCEL IFR AFTER HE OR SHE IS UNABLE TO MAINTAIN ASSIGNED ALT.

Narrative: FLYING IFR IN IMC NEAR TXC AT 9000 FT MSL HDG APPROX 220 DEGS. ALT WAS ASSIGNED BY ATC. PICKED UP LIGHTNING ON STORMSCOPE AND REQUESTED DEV TO L TOWARDS SOME BREAKS IN THE CLOUDS. ENTERED MODERATE TURB AND SUBSTANTIAL DOWNDRAFTS. UNABLE TO MAINTAIN ASSIGNED ALT AND DSNDED TO 7000 FT. MINIMUM ENRTE ALT 7200 FT. I WAS TOLD BY ATC THAT I WOULD NEED TO CLB TO 10000 FT. I CLBED TO 8500 FT WITH DIFFICULTY BUT BROKE OUT TO VMC. I TOLD ATC THAT I COULD MAINTAIN VISUAL SEPARATION FROM THE GND. I WAS TOLD THAT I MUST CLB TO 10000 FT TO STAY IFR. BUT THIS WOULD PUT ME DEEP INTO BLACK STORM CLOUDS. I CANCELED IFR AND PROCEEDED IN MARGINAL VMC TO DEST. IF I WAS UNABLE TO MAINTAIN VMC IT WOULD HAVE BEEN NECESSARY TO CLB INTO THICKENING TSTM CLOUDS.

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.