Narrative:

In 20 yrs of flying cpr jets, including 10 in this airframe, I have never held at FL390. On mmu-pie flight, we slowed 50+ NM north of tlh while diverting and expecting delay due to severe thunderstorm line at destination. Discussed holding pattern (direct entry) and speed, input hold in FMS, and planned on 190 KIAS hold. 20 mi legs given at 20 DME outbound aircraft failed to turn, so I reselected heading mode, and initiated turn manually, adding power as KIAS was about 180 KTS. Due to high winds aloft, outbound crab angle was 60 degrees. FMS and DME displays did not agree, and we discussed this as I continued the long turn to intercept inbound, concerned that we stay on holding track: KIAS was about 175 KTS, so I added more power. As the aircraft leveled, I noted airspeed at 170 KTS and felt airframe 'rumble.' I added still more power, yet airspeed slowed to 165 KTS, and there was a second, stronger rumble. Extremely concerned, I alerted sic as I disengaged autoplt, added maximum climb power, and allowed descent so as to maintain airspeed. At start of descent stick shaker activated briefly. At 38200 ft we stabilized, advised center, and climbed to FL390, returning to normal operations. ATC expressed no concern. Calculated stall for conditions 127 KTS. Lowest KIAS seen: 165 KTS. Factors: distraction from FMS. Very long deceleration and acceleration times at FL390. Later realized FMS 'DME' includes holding track distance (not mentioned in manual). Even at sea level takeoff thrust N1% setting may not be sufficient to accelerate at FL390. First time holding/maneuvering at flight level, not covered in afm, operation manual or recurrent training. Staying 'behind power curve' with incremental power advances in a high drag, high altitude state. Did not recognize buffet immediately, felt 165 KIAS too high for it. Possible shear/subsiding area behind strong thunderstorm line. No usable angle of attack system (angle of attack for stall warning only). Too concerned about fuel -- landed 4800 pounds -- (2+24 @ 250 KTS) even after 30 min delay. The one right thing done: flew the airplane first, and did not allow further deceleration. Distraction and atmospheric conditions may have played small roles, but primarily the situation was due to an incomplete understanding of high altitude, lower airspeed flight and maneuvering, and a lack of training and guidance in those areas. On a later flight at 3000 ft MSL, 180 KIAS, I observed the power curve/pitch dynamics, but it is nothing like FL390 due to the larger power reserve available. This really was a blind spot in my knowledge and training, and could have had very dire consequences.

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Original NASA ASRS Text

Title: A CANADAIR CL600 FLIES TOO SLOW AT HIGH ALT FOR A HOLDING PATTERN AND ENCOUNTERS BUFFETING INDICATING ACFT IS APCHING A STALL. FLC DSNDS ACFT TO REGAIN SPD IN ZJX, FL, AIRSPACE.

Narrative: IN 20 YRS OF FLYING CPR JETS, INCLUDING 10 IN THIS AIRFRAME, I HAVE NEVER HELD AT FL390. ON MMU-PIE FLT, WE SLOWED 50+ NM N OF TLH WHILE DIVERTING AND EXPECTING DELAY DUE TO SEVERE TSTM LINE AT DEST. DISCUSSED HOLDING PATTERN (DIRECT ENTRY) AND SPD, INPUT HOLD IN FMS, AND PLANNED ON 190 KIAS HOLD. 20 MI LEGS GIVEN AT 20 DME OUTBOUND ACFT FAILED TO TURN, SO I RESELECTED HEADING MODE, AND INITIATED TURN MANUALLY, ADDING PWR AS KIAS WAS ABOUT 180 KTS. DUE TO HIGH WINDS ALOFT, OUTBOUND CRAB ANGLE WAS 60 DEGS. FMS AND DME DISPLAYS DID NOT AGREE, AND WE DISCUSSED THIS AS I CONTINUED THE LONG TURN TO INTERCEPT INBOUND, CONCERNED THAT WE STAY ON HOLDING TRACK: KIAS WAS ABOUT 175 KTS, SO I ADDED MORE PWR. AS THE ACFT LEVELED, I NOTED AIRSPD AT 170 KTS AND FELT AIRFRAME 'RUMBLE.' I ADDED STILL MORE PWR, YET AIRSPD SLOWED TO 165 KTS, AND THERE WAS A SECOND, STRONGER RUMBLE. EXTREMELY CONCERNED, I ALERTED SIC AS I DISENGAGED AUTOPLT, ADDED MAX CLB PWR, AND ALLOWED DSCNT SO AS TO MAINTAIN AIRSPD. AT START OF DSCNT STICK SHAKER ACTIVATED BRIEFLY. AT 38200 FT WE STABILIZED, ADVISED CTR, AND CLBED TO FL390, RETURNING TO NORMAL OPS. ATC EXPRESSED NO CONCERN. CALCULATED STALL FOR CONDITIONS 127 KTS. LOWEST KIAS SEEN: 165 KTS. FACTORS: DISTR FROM FMS. VERY LONG DECELERATION AND ACCELERATION TIMES AT FL390. LATER REALIZED FMS 'DME' INCLUDES HOLDING TRACK DISTANCE (NOT MENTIONED IN MANUAL). EVEN AT SEA LEVEL TKOF THRUST N1% SETTING MAY NOT BE SUFFICIENT TO ACCELERATE AT FL390. FIRST TIME HOLDING/MANEUVERING AT FLT LEVEL, NOT COVERED IN AFM, OP MANUAL OR RECURRENT TRAINING. STAYING 'BEHIND PWR CURVE' WITH INCREMENTAL PWR ADVANCES IN A HIGH DRAG, HIGH ALT STATE. DID NOT RECOGNIZE BUFFET IMMEDIATELY, FELT 165 KIAS TOO HIGH FOR IT. POSSIBLE SHEAR/SUBSIDING AREA BEHIND STRONG TSTM LINE. NO USABLE ANGLE OF ATTACK SYS (ANGLE OF ATTACK FOR STALL WARNING ONLY). TOO CONCERNED ABOUT FUEL -- LANDED 4800 LBS -- (2+24 @ 250 KTS) EVEN AFTER 30 MIN DELAY. THE ONE RIGHT THING DONE: FLEW THE AIRPLANE FIRST, AND DID NOT ALLOW FURTHER DECELERATION. DISTR AND ATMOSPHERIC CONDITIONS MAY HAVE PLAYED SMALL ROLES, BUT PRIMARILY THE SIT WAS DUE TO AN INCOMPLETE UNDERSTANDING OF HIGH ALT, LOWER AIRSPD FLT AND MANEUVERING, AND A LACK OF TRAINING AND GUIDANCE IN THOSE AREAS. ON A LATER FLT AT 3000 FT MSL, 180 KIAS, I OBSERVED THE PWR CURVE/PITCH DYNAMICS, BUT IT IS NOTHING LIKE FL390 DUE TO THE LARGER PWR RESERVE AVAILABLE. THIS REALLY WAS A BLIND SPOT IN MY KNOWLEDGE AND TRAINING, AND COULD HAVE HAD VERY DIRE CONSEQUENCES.

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.