A corporate aircraft crew reported that after climbing to FL400 at ATC's request they found the temp...

Attributes
ACN	976075
Time
Date	201110
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZZ.ARTCC
State Reference	FO
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Medium Transport Low Wing 2 Turbojet Eng
Operating Under FAR Part	Part 91
Flight Phase	Climb
Route In Use	Direct
Flight Plan	IFR
Person 1
Function	Pilot Not Flying Captain
Qualification	Flight Crew Instrument Flight Crew Air Transport Pilot (ATP) Flight Crew Flight Instructor
Experience	Flight Crew Last 90 Days 50 Flight Crew Total 12300 Flight Crew Type 350
Person 2
Function	First Officer Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 90 Flight Crew Total 5500 Flight Crew Type 300
Events
Anomaly	Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Deviation - Speed All Types Inflight Event / Encounter Weather / Turbulence

Narrative:

On our flight west bound atlantic crossing we were level at FL360 about one hour and thirty-five minutes after departure. We asked for and were cleared to FL380; which we arrived at without issue. The OAT was cold; -52; and the aircraft was performing normal. ATC asked if we could go to FL400 for our ocean crossing. We accepted after reviewing our FMS for performance at that altitude and they indicated we could. As we started up we noticed a significant warming of the OAT above FL390 and when we arrived at FL400 the OAT was -46 with an isa of +11. Due to aircraft weight and OAT; we where indicating a mach of .67 to .68 with a rate of climb of +300 feet. After leveling off at FL400 with max power applied the aircraft would not accelerate. In fact; the indicate airspeed started to decelerate from 205 through 195 at a rather slow rate. After about ten minutes at max power and a slowly decreasing indicated airspeed I asked ATC for a lower altitude to which they responded; 'standby.' within minutes for requesting a lower fl the indicated airspeed started a more rapid decrease with an increasing aoa; indicating back side of power curve; and with the OAT still indicating +11 I told ATC; 'we must descend now' to which we stated; 'roger; maintain FL400.' shortly there after; I felt the wings start a slight buffet and a slight rolling of the wings. I checked the TCAS and seeing no aircraft within a 40NM range I instructed the pilot flying to descend now. I told act 'I am descending and would level off at FL380.' after passing FL390 the OAT decreased again to -52 and isa had cooled to +2. The aircraft again returned to stable flight and we continued. All weather reports we had received from our handler; universal; indicated temperatures at altitude to be -52 or colder. However; we found out that at above FL390 the actual temperature was much warmer and we could not operate at those altitudes and our aircraft weight.

Original NASA ASRS Text

Title: A Corporate aircraft Crew reported that after climbing to FL400 at ATC's request they found the temperature was ISA +11 and the aircraft lost airspeed so they started a descent while waiting for ATC clearance.

Narrative: On our flight west bound Atlantic crossing we were level at FL360 about one hour and thirty-five minutes after departure. We asked for and were cleared to FL380; which we arrived at without issue. The OAT was cold; -52; and the aircraft was performing normal. ATC asked if we could go to FL400 for our ocean crossing. We accepted after reviewing our FMS for performance at that altitude and they indicated we could. As we started up we noticed a significant warming of the OAT above FL390 and when we arrived at FL400 the OAT was -46 with an ISA of +11. Due to aircraft weight and OAT; we where indicating a MACH of .67 to .68 with a rate of climb of +300 feet. After leveling off at FL400 with max power applied the aircraft would not accelerate. In fact; the indicate airspeed started to decelerate from 205 through 195 at a rather slow rate. After about ten minutes at max power and a slowly decreasing indicated airspeed I asked ATC for a lower altitude to which they responded; 'standby.' Within minutes for requesting a lower FL the indicated airspeed started a more rapid decrease with an increasing AOA; indicating back side of power curve; and with the OAT still indicating +11 I told ATC; 'we must descend now' to which we stated; 'roger; maintain FL400.' Shortly there after; I felt the wings start a slight buffet and a slight rolling of the wings. I checked the TCAS and seeing no aircraft within a 40NM range I instructed the pilot flying to descend now. I told ACT 'I AM descending and would level off at FL380.' After passing FL390 the OAT decreased again to -52 and ISA had cooled to +2. The aircraft again returned to stable flight and we continued. All weather reports we had received from our handler; Universal; indicated temperatures at altitude to be -52 or colder. However; we found out that at above FL390 the actual temperature was much warmer and we could not operate at those altitudes and our aircraft weight.

Data retrieved from NASA's ASRS site as of April 2012 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.

A corporate aircraft crew reported that after climbing to FL400 at ATC's request they found the temperature was isa +11 and the aircraft lost airspeed so they started a descent while waiting for ATC clearance.