Lear 36 first officer reports temperature increase climbing from FL390 to FL410 that engine performa...

Attributes
ACN	775030
Time
Date	200802
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	msl single value : 41000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zzz.artcc
Operator	general aviation : corporate
Make Model Name	Learjet 36
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : multi engine pilot : cfi pilot : commercial
Experience	flight time last 90 days : 250 flight time total : 2000 flight time type : 250
ASRS Report	775030
Events
Anomaly	inflight encounter : weather other anomaly
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance flight crew : exited adverse environment flight crew : declared emergency
Supplementary
Problem Areas	Flight Crew Human Performance Weather
Primary Problem	Weather

Narrative:

Eastbound we just leveled at 39000 ft. We accelerated to .78 mach with engine power to spare. We decided to climb to FL410 and level off. We then noticed we were not accelerating beyond .71 mach. We realized there had been a temperature inversion and had gained about 20 degree temperature RAT during the climb. Speed was stable at .71 mach. We asked center for a descent back to FL390. The controller advised there would be a 4 min delay for traffic which we complied with because our airspeed was stable with power to spare. About 3-4 mins later speed began to deteriorate rapidly and we were unable to regain speed with a power adjustment. I called center requesting a vector for an immediate descent to FL390. He replied unable and asked if we were declaring an emergency. I told him no that we encountered an inversion and will be unable to maintain FL410 much longer without a descent. The controller then asked me to call him and began giving me a number. At that point we could no longer maintain FL410 we declared an emergency and descended to FL370; leveled off; and advised the controller the emergency was over. We continued to our destination without incident.

Original NASA ASRS Text

Title: LEAR 36 FO REPORTS TEMPERATURE INCREASE CLIMBING FROM FL390 TO FL410 THAT ENGINE PERFORMANCE COULD NOT OVERCOME. EMERGENCY IS DECLARED FOR DESCENT TO FL370.

Narrative: EBOUND WE JUST LEVELED AT 39000 FT. WE ACCELERATED TO .78 MACH WITH ENG PWR TO SPARE. WE DECIDED TO CLB TO FL410 AND LEVEL OFF. WE THEN NOTICED WE WERE NOT ACCELERATING BEYOND .71 MACH. WE REALIZED THERE HAD BEEN A TEMP INVERSION AND HAD GAINED ABOUT 20 DEG TEMP RAT DURING THE CLB. SPD WAS STABLE AT .71 MACH. WE ASKED CTR FOR A DSCNT BACK TO FL390. THE CTLR ADVISED THERE WOULD BE A 4 MIN DELAY FOR TFC WHICH WE COMPLIED WITH BECAUSE OUR AIRSPD WAS STABLE WITH PWR TO SPARE. ABOUT 3-4 MINS LATER SPD BEGAN TO DETERIORATE RAPIDLY AND WE WERE UNABLE TO REGAIN SPD WITH A PWR ADJUSTMENT. I CALLED CTR REQUESTING A VECTOR FOR AN IMMEDIATE DSCNT TO FL390. HE REPLIED UNABLE AND ASKED IF WE WERE DECLARING AN EMER. I TOLD HIM NO THAT WE ENCOUNTERED AN INVERSION AND WILL BE UNABLE TO MAINTAIN FL410 MUCH LONGER WITHOUT A DSCNT. THE CTLR THEN ASKED ME TO CALL HIM AND BEGAN GIVING ME A NUMBER. AT THAT POINT WE COULD NO LONGER MAINTAIN FL410 WE DECLARED AN EMER AND DSNDED TO FL370; LEVELED OFF; AND ADVISED THE CTLR THE EMER WAS OVER. WE CONTINUED TO OUR DEST WITHOUT INCIDENT.

Data retrieved from NASA's ASRS site as of May 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.

Lear 36 first officer reports temperature increase climbing from FL390 to FL410 that engine performance could not overcome. Emergency is declared for descent to FL370.