B737-800
Flight Crew Air Transport Pilot (ATP)
Communication Breakdown; Time Pressure; Workload
ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Issued New Clearance; Flight Crew Took Evasive Action
Weather
Level at FL380 on the Western slopes of Sierras we encountered a strong mountain wave. As the speed started to roll back I selected max continuous thrust. This didn't help much. I then called OAK Center for lower. I was told unable and to stand by. I then told them we would not be able to maintain FL380 and I started a slow descent 300 FPM to get the speed to increase. As I was doing this OAK called back and gave us FL360. We descended 150 FT while waiting for the clearance. Total airspeed loss was approximately 35 KTS during the event.
A B737-800 flight crew encountered a mountain wave and began descending to recover a 35 KTS airspeed loss while awaiting ATC descent clearance.