DC-8 flight crew described encountering a severe mountain wave and flight upset event that resulted in an engine failure and ATC's initiation of an emergency declaration.
Synopsis
DC-8 flight crew described encountering a severe mountain wave and flight upset event that resulted in an engine failure and ATC's initiation of an emergency declaration.
Narrative
At 37;000 FT and .80 mach; we experienced a severe mountain wave and flight upset. We were in an extreme updraft with an associated airspeed deviation between .78 and .88 mach. Elevator control was ineffective and thrust levers were retarded to idle to facilitate an altitude and speed recovery. There was a period of 15 seconds where any attempt to regain control was ineffective. The mountain wave existed for another 45 seconds at a lesser degree. Once we returned to normal flight conditions; we noticed that the #1 engine was indicating 45% N1. Thrust lever positions had no effect and engine would not accelerate. It appeared to be 'hung' due to a compressor stall. The Abnormal Procedure for an in flight engine shutdown was completed; followed by a descent to 31;000 FT to attempt a restart. A restart was attempted but was unsuccessful. ATC; Flight Control and Maintenance Control were all communicated with during and after the course of this event. We did not declare an emergency. All applicable emergency checklists and abnormal procedures were complied with. Since the aircraft was now stabilized and we were at a light weight; I chose to continue a 3-engine cruise at 31;000 FT rather than descend to a lower altitude to attempt another start which; if it failed; would have required a climb back to a cruise altitude on 3 engines with the associated additional fuel burn. The crew concurred with this decision. We arrived at our destination without further incident and were informed that ATC had declared an emergency on our behalf and had dispatched the CFR. We landed and taxied to the gate without further problem(s). In the future; avoid areas of reported CAT or severe mountain wave. In this case; none had been reported for this area. Center said an aircraft had flown our route 10 minutes earlier and had not reported any problems.
Second reporter narrative
[No additional information was provided.]
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.