B737-800 first officer reports being dispatched with inoperative autothrust with the captain as pilo...

Narrative:

We departed with the auto throttles MEL'd. I was the pilot monitoring on this leg. In cruise flight at M.78; the captain went back for a lavatory break. In his absence; I inadvertently allowed the airspeed to decay to a few knots above the top of the yellow bar. When he returned; he noticed our airspeed and immediately increased power to maximum con and initiated a very shallow descent (approx 200-300 feet) to regain airspeed. He accelerated to M .76 and then climbed 200 feet back to cruise altitude. I'm not sure what caused my inattention. I may have been setting up my ipad for the arrival or getting ready for the next position report. I knew the auto throttles were inop; but because I hadn't been fly until the captain went to the lav; I guess it slipped my mind. I didn't touch the throttles while he was gone. The captain was gone for probably less than 3 minutes. In future auto throttle inop situations; I think the pilot flying should brief the pilot monitoring what power setting was holding the airspeed before he/she leaves the seat; as a reminder that the auto throttles are off.

Original NASA ASRS Text

Title: B737-800 First Officer reports being dispatched with inoperative autothrust with the Captain as pilot flying. In cruise the Captain takes a lavatory break and returns to find the airspeed dangerously low. The Captain uses maximum thrust and a shallow descent to regain the lost airspeed.

Narrative: We departed with the auto throttles MEL'd. I was the Pilot Monitoring on this leg. In cruise flight at M.78; the Captain went back for a lavatory break. In his absence; I inadvertently allowed the airspeed to decay to a few knots above the top of the yellow bar. When he returned; he noticed our airspeed and immediately increased power to MAX CON and initiated a very shallow descent (approx 200-300 feet) to regain airspeed. He accelerated to M .76 and then climbed 200 feet back to cruise altitude. I'm not sure what caused my inattention. I may have been setting up my iPad for the arrival or getting ready for the next position report. I knew the Auto Throttles were inop; but because I hadn't been fly until the Captain went to the Lav; I guess it slipped my mind. I didn't touch the throttles while he was gone. The Captain was gone for probably less than 3 minutes. In future Auto Throttle inop situations; I think the pilot flying should brief the pilot monitoring what power setting was holding the airspeed before he/she leaves the seat; as a reminder that the Auto Throttles are off.

Data retrieved from NASA's ASRS site 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.

Attributes
ACN	1208890
Time
Date	201409
Place
Locale Reference	ZZZ.Airport
State Reference	US
Aircraft 1
Make Model Name	B737-800
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	Throttle/Power Lever
Person 1
Function	First Officer Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Published Material / Policy Deviation - Speed All Types

B737-800 first officer reports being dispatched with inoperative autothrust with the captain as pilot flying. In cruise the captain takes a lavatory break and returns to find the airspeed dangerously low. The captain uses maximum thrust and a shallow descent to regain the lost airspeed.