Small transport cruising at FL410 is allowed to stall -- twice!

Attributes
ACN	233830
Time
Date	199302
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : den
State Reference	CO
Altitude	msl bound lower : 40100 msl bound upper : 41000
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Controlling Facilities	artcc : zlc
Operator	general aviation : corporate
Make Model Name	Small Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 6000 flight time type : 600
ASRS Report	233830
Person 2
Affiliation	Other
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	other anomaly
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : regained aircraft control
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We were level at FL410. The angle of attack indicator indicated plus 10 KTS. Approximately 20 mins later, I noticed the aoa and airspeed indicating we were slowing down. I mentioned to the captain what I had observed, he agreed. About 30 seconds later, we encountered a stall. The aircraft lost about 400-500 ft. The captain directed me to request a lower altitude, we were denied. The captain attempted to level off. The altitude was now approximately FL405. With this attempt we encountered a secondary stall, subsequently losing approximately 300-400 ft more. Leveling off at approximately FL400, the aircraft was now stabilized in level flight in VMC. The probable cause of the initial pitch attitude increase and airspeed decrease was a sudden change in outside air temperature and/or a sudden change in our center of gravity moving aft. In the future, I will do my best to prevent the aircraft from getting into such a confign as first mentioned, and make it my own SOP to declare an emergency much sooner, no matter who I fly with.

Original NASA ASRS Text

Title: SMT CRUISING AT FL410 IS ALLOWED TO STALL -- TWICE!

Narrative: WE WERE LEVEL AT FL410. THE ANGLE OF ATTACK INDICATOR INDICATED PLUS 10 KTS. APPROX 20 MINS LATER, I NOTICED THE AOA AND AIRSPD INDICATING WE WERE SLOWING DOWN. I MENTIONED TO THE CAPT WHAT I HAD OBSERVED, HE AGREED. ABOUT 30 SECONDS LATER, WE ENCOUNTERED A STALL. THE ACFT LOST ABOUT 400-500 FT. THE CAPT DIRECTED ME TO REQUEST A LOWER ALT, WE WERE DENIED. THE CAPT ATTEMPTED TO LEVEL OFF. THE ALT WAS NOW APPROX FL405. WITH THIS ATTEMPT WE ENCOUNTERED A SECONDARY STALL, SUBSEQUENTLY LOSING APPROX 300-400 FT MORE. LEVELING OFF AT APPROX FL400, THE ACFT WAS NOW STABILIZED IN LEVEL FLT IN VMC. THE PROBABLE CAUSE OF THE INITIAL PITCH ATTITUDE INCREASE AND AIRSPD DECREASE WAS A SUDDEN CHANGE IN OUTSIDE AIR TEMP AND/OR A SUDDEN CHANGE IN OUR CTR OF GRAVITY MOVING AFT. IN THE FUTURE, I WILL DO MY BEST TO PREVENT THE ACFT FROM GETTING INTO SUCH A CONFIGN AS FIRST MENTIONED, AND MAKE IT MY OWN SOP TO DECLARE AN EMER MUCH SOONER, NO MATTER WHO I FLY WITH.

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.