Narrative:

While reports of moderate turbulence were being issued for the mid FL300 altitudes, no reports of mountain wave activity were broadcast at our time of sierra nevada crossing. Performance charts showed FL410 to be an adequate altitude for moderate turbulence or less under mach .80 cruise conditions. Actually, an altitude higher than FL419 was attainable under present weight conditions. Approximately 30 NM west of the coaldale VORTAC, we encountered what can be described as moderate to severe mountain wave activity with little associated turbulence. While climbing through FL400, the aircraft's climb rate began to slow and at times went to zero rate of change. At approximately FL415, the aircraft would no longer climb and 'altitude hold' was selected on the autoplt to maintain proper climb/cruise speed. Shortly thereafter, airspeed began to rapidly decay and as the speed approached 220 KIAS, we requested and received a 'block' altitude of FL410-FL390 so as to use a lower altitude to protect airspeed. Minimum airspeed was noted at 215 KIAS, but then began a rapid rise back toward mach cruise and then continued rapidly toward mmo ( M .860). Power was reduced with airspeed continuing to rise to M .850. At approximately M .855, power was reduced to close to idle with the autoplt disconnected and a manual climb begun to maintain airspeed less than M .860. With power near idle and a rate first officer climb of approximately 1500-2000 FPM, speed held at approximately M .850. The aircraft climbed to FL416-FL417 before airspeed began to slow below M .850. We were switched to ZLC and asked if there were any traffic conflicts. We were told no conflict existed and issued a 'block' altitude of FL430-FL390 after requesting such altitude. Upon advising ATC of the wave encountered, slc informed us that severe wave activity was being reported in the area at the lower altitudes (mid FL300 altitudes). Note: we received no preflight information nor any en route information or advisories concerning the wave activity prior to our encounter.

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Original NASA ASRS Text

Title: FLT AT 410 ENCOUNTERED MOUNTAIN WAVE, POWER AT IDLE, CLIMB RATE 1000 FPM, FLT OVERSHOT ASSIGNED ALT.

Narrative: WHILE REPORTS OF MODERATE TURBULENCE WERE BEING ISSUED FOR THE MID FL300 ALTS, NO REPORTS OF MOUNTAIN WAVE ACTIVITY WERE BROADCAST AT OUR TIME OF SIERRA NEVADA XING. PERFORMANCE CHARTS SHOWED FL410 TO BE AN ADEQUATE ALT FOR MODERATE TURBULENCE OR LESS UNDER MACH .80 CRUISE CONDITIONS. ACTUALLY, AN ALT HIGHER THAN FL419 WAS ATTAINABLE UNDER PRESENT WEIGHT CONDITIONS. APPROX 30 NM W OF THE COALDALE VORTAC, WE ENCOUNTERED WHAT CAN BE DESCRIBED AS MODERATE TO SEVERE MOUNTAIN WAVE ACTIVITY WITH LITTLE ASSOCIATED TURBULENCE. WHILE CLIMBING THROUGH FL400, THE ACFT'S CLIMB RATE BEGAN TO SLOW AND AT TIMES WENT TO ZERO RATE OF CHANGE. AT APPROX FL415, THE ACFT WOULD NO LONGER CLIMB AND 'ALT HOLD' WAS SELECTED ON THE AUTOPLT TO MAINTAIN PROPER CLIMB/CRUISE SPEED. SHORTLY THEREAFTER, AIRSPEED BEGAN TO RAPIDLY DECAY AND AS THE SPEED APCHED 220 KIAS, WE REQUESTED AND RECEIVED A 'BLOCK' ALT OF FL410-FL390 SO AS TO USE A LOWER ALT TO PROTECT AIRSPEED. MINIMUM AIRSPEED WAS NOTED AT 215 KIAS, BUT THEN BEGAN A RAPID RISE BACK TOWARD MACH CRUISE AND THEN CONTINUED RAPIDLY TOWARD MMO ( M .860). POWER WAS REDUCED WITH AIRSPEED CONTINUING TO RISE TO M .850. AT APPROX M .855, POWER WAS REDUCED TO CLOSE TO IDLE WITH THE AUTOPLT DISCONNECTED AND A MANUAL CLIMB BEGUN TO MAINTAIN AIRSPEED LESS THAN M .860. WITH POWER NEAR IDLE AND A RATE FO CLIMB OF APPROX 1500-2000 FPM, SPEED HELD AT APPROX M .850. THE ACFT CLIMBED TO FL416-FL417 BEFORE AIRSPEED BEGAN TO SLOW BELOW M .850. WE WERE SWITCHED TO ZLC AND ASKED IF THERE WERE ANY TFC CONFLICTS. WE WERE TOLD NO CONFLICT EXISTED AND ISSUED A 'BLOCK' ALT OF FL430-FL390 AFTER REQUESTING SUCH ALT. UPON ADVISING ATC OF THE WAVE ENCOUNTERED, SLC INFORMED US THAT SEVERE WAVE ACTIVITY WAS BEING REPORTED IN THE AREA AT THE LOWER ALTS (MID FL300 ALTS). NOTE: WE RECEIVED NO PREFLT INFO NOR ANY ENRTE INFO OR ADVISORIES CONCERNING THE WAVE ACTIVITY PRIOR TO OUR ENCOUNTER.

Data retrieved from NASA's ASRS site as of July 2007 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.