Narrative:

Flight was approximately 275 mi from las at FL400; when the first officer needed to go to the restroom. We went through the appropriate steps and after about a 10 min wait; the flight attendant told us that it was clear to come out. Prior to his departure; ATC had issued us a descent clearance to FL360. The first officer was the PF and he initiated a cruise descent using vertical speed at 1000 FPM and reducing power to maintain airspeed. He departed the flight deck when the aircraft was approximately out of FL380. Before he departed; the first officer xferred control of the aircraft and I acknowledged same. He departed and the flight attendant entered the flight deck. The aircraft leveled at FL360 but I failed to notice the leveloff. I'm sure that my attention was directed somewhat aft; to the flight attendant. After a few mins; I noticed that the airspeed had decayed. I advanced the T/left and requested a lower altitude. The stick shaker activated. The controller cleared me to FL320 and I disengaged the autoplt and started a descent to FL320. The aircraft recovered relatively quickly and the first officer and the flight attendant exchanged position as the aircraft was out of FL330 for FL320. The aircraft proceeded to las without further incident. Contributing factors: 1) cruise descent; done for fuel conservation; feels and sounds like cruise; idle dscnts would not. 2) xferring control and then leaving the flight deck during a descent that the PF (vacating) initiated. 3) the requirement of the flight attendant to enter the cockpit. He/she may be viewed as a possible distraction. My feelings are split between: 1) I can't believe it happened; and 2) I can't believe it never happened to me before. It was that insidious. What can be done to prevent it: 1) avoid bathroom breaks during dscnts. 2) couple the xfer of control with a short brief; eg; 'the aircraft is descending; 2000 ft to go to leveloff.' supplemental information from acn 695150: we discussed the event; and this is what I perceived to have occurred: I left cockpit in descent with some power set. Flight attendant entered; engaged the captain in conversation which distraction his primary attention away from the instruments. The aircraft descended and leveled off at FL360 as commanded; but full cruise power was not re-established. Aircraft continued to slow while level until stick shaker occurred. Captain recognized this; applied full thrust to no avail; had presence of mind to see that there was an aircraft below us at undetermined distance; requested a descent from center; which was immediately granted to FL320. No TCAS alert occurred; no comment from center; no perceived need to declare emergency (which I agree with). Nose was smoothly lowered and airspeed rapidly restored. Neither flight attendants nor passenger were alarmed by this incident. I made a PA to passenger to explain descent and vibration; explained that we had encountered turbulence and mountain wave activity; which we truly had crossing rockies and subsequently encountered further on our route and descent into las. Analysis: several contributing factors included descent; xfer of controls while in descent; strong distraction of flight attendant in cockpit wanting to talk and get a break from busy activities in cabin. For my personal knowledge and experience gain from this incident; I will endeavor not to xfer controls if not in stabilized; level flight. If I have to do so; I will fully brief phase of flight (climb or descent; etc); power set or not; what altitude cleared to next; etc; before xferring controls. This event also illustrates in vivid detail how distracting flight attendants can be in cockpit (through no fault of their own); and how we must strictly concentrate on maintaining focus and situational awareness on the mission at hand; namely flying the airplane first before all else. Aviate; navigation; communicate!

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Original NASA ASRS Text

Title: B737-700 FLT CREW RECEIVES STICK SHAKER WHEN PWR WAS NOT RESTORED FOR LEVEL FLT AFTER A CRUISE DSCNT.

Narrative: FLT WAS APPROX 275 MI FROM LAS AT FL400; WHEN THE FO NEEDED TO GO TO THE RESTROOM. WE WENT THROUGH THE APPROPRIATE STEPS AND AFTER ABOUT A 10 MIN WAIT; THE FLT ATTENDANT TOLD US THAT IT WAS CLR TO COME OUT. PRIOR TO HIS DEP; ATC HAD ISSUED US A DSCNT CLRNC TO FL360. THE FO WAS THE PF AND HE INITIATED A CRUISE DSCNT USING VERT SPD AT 1000 FPM AND REDUCING PWR TO MAINTAIN AIRSPD. HE DEPARTED THE FLT DECK WHEN THE ACFT WAS APPROX OUT OF FL380. BEFORE HE DEPARTED; THE FO XFERRED CTL OF THE ACFT AND I ACKNOWLEDGED SAME. HE DEPARTED AND THE FLT ATTENDANT ENTERED THE FLT DECK. THE ACFT LEVELED AT FL360 BUT I FAILED TO NOTICE THE LEVELOFF. I'M SURE THAT MY ATTN WAS DIRECTED SOMEWHAT AFT; TO THE FLT ATTENDANT. AFTER A FEW MINS; I NOTICED THAT THE AIRSPD HAD DECAYED. I ADVANCED THE T/L AND REQUESTED A LOWER ALT. THE STICK SHAKER ACTIVATED. THE CTLR CLRED ME TO FL320 AND I DISENGAGED THE AUTOPLT AND STARTED A DSCNT TO FL320. THE ACFT RECOVERED RELATIVELY QUICKLY AND THE FO AND THE FLT ATTENDANT EXCHANGED POS AS THE ACFT WAS OUT OF FL330 FOR FL320. THE ACFT PROCEEDED TO LAS WITHOUT FURTHER INCIDENT. CONTRIBUTING FACTORS: 1) CRUISE DSCNT; DONE FOR FUEL CONSERVATION; FEELS AND SOUNDS LIKE CRUISE; IDLE DSCNTS WOULD NOT. 2) XFERRING CTL AND THEN LEAVING THE FLT DECK DURING A DSCNT THAT THE PF (VACATING) INITIATED. 3) THE REQUIREMENT OF THE FLT ATTENDANT TO ENTER THE COCKPIT. HE/SHE MAY BE VIEWED AS A POSSIBLE DISTR. MY FEELINGS ARE SPLIT BTWN: 1) I CAN'T BELIEVE IT HAPPENED; AND 2) I CAN'T BELIEVE IT NEVER HAPPENED TO ME BEFORE. IT WAS THAT INSIDIOUS. WHAT CAN BE DONE TO PREVENT IT: 1) AVOID BATHROOM BREAKS DURING DSCNTS. 2) COUPLE THE XFER OF CTL WITH A SHORT BRIEF; EG; 'THE ACFT IS DSNDING; 2000 FT TO GO TO LEVELOFF.' SUPPLEMENTAL INFO FROM ACN 695150: WE DISCUSSED THE EVENT; AND THIS IS WHAT I PERCEIVED TO HAVE OCCURRED: I LEFT COCKPIT IN DSCNT WITH SOME PWR SET. FLT ATTENDANT ENTERED; ENGAGED THE CAPT IN CONVERSATION WHICH DISTR HIS PRIMARY ATTN AWAY FROM THE INSTS. THE ACFT DSNDED AND LEVELED OFF AT FL360 AS COMMANDED; BUT FULL CRUISE PWR WAS NOT RE-ESTABLISHED. ACFT CONTINUED TO SLOW WHILE LEVEL UNTIL STICK SHAKER OCCURRED. CAPT RECOGNIZED THIS; APPLIED FULL THRUST TO NO AVAIL; HAD PRESENCE OF MIND TO SEE THAT THERE WAS AN ACFT BELOW US AT UNDETERMINED DISTANCE; REQUESTED A DSCNT FROM CTR; WHICH WAS IMMEDIATELY GRANTED TO FL320. NO TCAS ALERT OCCURRED; NO COMMENT FROM CTR; NO PERCEIVED NEED TO DECLARE EMER (WHICH I AGREE WITH). NOSE WAS SMOOTHLY LOWERED AND AIRSPD RAPIDLY RESTORED. NEITHER FLT ATTENDANTS NOR PAX WERE ALARMED BY THIS INCIDENT. I MADE A PA TO PAX TO EXPLAIN DSCNT AND VIBRATION; EXPLAINED THAT WE HAD ENCOUNTERED TURB AND MOUNTAIN WAVE ACTIVITY; WHICH WE TRULY HAD XING ROCKIES AND SUBSEQUENTLY ENCOUNTERED FURTHER ON OUR RTE AND DSCNT INTO LAS. ANALYSIS: SEVERAL CONTRIBUTING FACTORS INCLUDED DSCNT; XFER OF CTLS WHILE IN DSCNT; STRONG DISTR OF FLT ATTENDANT IN COCKPIT WANTING TO TALK AND GET A BREAK FROM BUSY ACTIVITIES IN CABIN. FOR MY PERSONAL KNOWLEDGE AND EXPERIENCE GAIN FROM THIS INCIDENT; I WILL ENDEAVOR NOT TO XFER CTLS IF NOT IN STABILIZED; LEVEL FLT. IF I HAVE TO DO SO; I WILL FULLY BRIEF PHASE OF FLT (CLB OR DSCNT; ETC); PWR SET OR NOT; WHAT ALT CLRED TO NEXT; ETC; BEFORE XFERRING CTLS. THIS EVENT ALSO ILLUSTRATES IN VIVID DETAIL HOW DISTRACTING FLT ATTENDANTS CAN BE IN COCKPIT (THROUGH NO FAULT OF THEIR OWN); AND HOW WE MUST STRICTLY CONCENTRATE ON MAINTAINING FOCUS AND SITUATIONAL AWARENESS ON THE MISSION AT HAND; NAMELY FLYING THE AIRPLANE FIRST BEFORE ALL ELSE. AVIATE; NAV; COMMUNICATE!

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