Engine failure during cruise
If an engine failure occurs at cruise altitude, it may be necessary to descend. The autothrottle should be disconnected and the thrust manually set to CON. On the FMC CRZ page select the ENG OUT prompt, followed by the prompt corresponding to the failed engine. This displays the engine out cruise data and the FMC calculates engine out target speed and maximum engine out altitude at the current gross weight. The fields are updated as fuel is burned. Do not execute the page if VNAV is required for any arrival procedures. If any ENG OUT page is executed then FMC will not transition to descent.
Set the maximum altitude in the MCP altitude window and the engine out target airspeed in the MCP IAS window. Allow airspeed to slow to engine out speed then engage LVL CHG. If the "Engine Out Target Airspeed" and "Maximum Continuous Thrust" are maintained, the airplane levels off above the original MAX altitude. However the updated MAX altitude is displayed on the ENG OUT CRZ page. After viewing the engine out data, select the ERASE prompt to return to the active cruise page.
After level off at the target altitude, maintain MCT and allow the airplane to accelerate to the single engine long range cruise speed. Maintain this speed with manual thrust adjustment. Entering the new cruise altitude and airspeed on the ECON CRZ page updates the ETAs and TOD predictions.
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the above is from the 737 flight crew training manual.
From what I understand is, first I should disengage Autothrottle then select MCT from the FMC and then adjust thrust manually to MCT rating.
but how can I allow the airspeed to decrease to the driftdown speed while in level flight and thrust at MCT? (isnt it necessary to maintain MCT while descending?)