Attempted climb on the 'backside of the power curve.'

Attributes
ACN	291348
Time
Date	199412
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : rmg
State Reference	GA
Altitude	msl bound lower : 29000 msl bound upper : 32000
Environment
Flight Conditions	Marginal
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : ztl
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : cfi pilot : flight engineer
Experience	flight time last 90 days : 210 flight time total : 7200 flight time type : 2300
ASRS Report	291348
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 10000 flight time type : 2400
ASRS Report	291570
Events
Anomaly	altitude deviation : undershoot inflight encounter : weather non adherence : clearance non adherence : far other anomaly other
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance flight crew : exited adverse environment
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Our aircraft was climbing to a cruise altitude of FL330. Both engine anti-ice and airfoil anti-ice were in use. The FMS 'VNAV climb' mode was controling the climb out but approaching FL320, airspeed was decreasing and mach was also rolling back. Both pilots could see that 'climb' thrust was only going to maintain altitude for the moment and that airspeed/mach was continuing to decay. As climb performance continued to deteriorate, and not wanting to increase our angle of attack, the captain disengaged the autoplt and began our descent back down to FL290. As he began the descent out of FL320, the first officer requested the descent with ATC and quickly received it. Aircraft was descended to FL290 where performance was fine. Lesson learned: high gross weight, high altitude, anti-ice on and poor airspeed control (ie, back side of the power curve) can all combine to create a performance barrier which can only be rectified by descending well below the service ceiling and increasing again to cruise mach. The turbulence at FL320 also contributed to our deteriorating climb performance and was a factor in our decision to descend back down to FL290 where it was smooth.

Original NASA ASRS Text

Title: ATTEMPTED CLB ON THE 'BACKSIDE OF THE PWR CURVE.'

Narrative: OUR ACFT WAS CLBING TO A CRUISE ALT OF FL330. BOTH ENG ANTI-ICE AND AIRFOIL ANTI-ICE WERE IN USE. THE FMS 'VNAV CLB' MODE WAS CTLING THE CLBOUT BUT APCHING FL320, AIRSPD WAS DECREASING AND MACH WAS ALSO ROLLING BACK. BOTH PLTS COULD SEE THAT 'CLB' THRUST WAS ONLY GOING TO MAINTAIN ALT FOR THE MOMENT AND THAT AIRSPD/MACH WAS CONTINUING TO DECAY. AS CLB PERFORMANCE CONTINUED TO DETERIORATE, AND NOT WANTING TO INCREASE OUR ANGLE OF ATTACK, THE CAPT DISENGAGED THE AUTOPLT AND BEGAN OUR DSCNT BACK DOWN TO FL290. AS HE BEGAN THE DSCNT OUT OF FL320, THE FO REQUESTED THE DSCNT WITH ATC AND QUICKLY RECEIVED IT. ACFT WAS DSNDED TO FL290 WHERE PERFORMANCE WAS FINE. LESSON LEARNED: HIGH GROSS WT, HIGH ALT, ANTI-ICE ON AND POOR AIRSPD CTL (IE, BACK SIDE OF THE PWR CURVE) CAN ALL COMBINE TO CREATE A PERFORMANCE BARRIER WHICH CAN ONLY BE RECTIFIED BY DSNDING WELL BELOW THE SVC CEILING AND INCREASING AGAIN TO CRUISE MACH. THE TURB AT FL320 ALSO CONTRIBUTED TO OUR DETERIORATING CLB PERFORMANCE AND WAS A FACTOR IN OUR DECISION TO DSND BACK DOWN TO FL290 WHERE IT WAS SMOOTH.

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.