Narrative:

After the inbound aircraft arrived at the gate; a quick turn was performed. During the preflight inspection; some residual ice was observed on the wings. The decision was made to deice the aircraft after push. Using the new ACARS hot method; type 1 fluid was used to remove the residual ice. As no current icing conditions existed; only type 1 fluid was used. During the climb; the selected vertical navigation mode was VNAV; as annunciated on the FMA. During the climb; engine anti-ice was used through most of the climb; until in clear air. Some light rime ice had also built up on the leading edge of the wings. The decision was made to utilize the wing anti-ice; as we climbed through FL330. Although the air was smooth; some mountain wave had been experienced throughout the climb. The VNAV had been climbing at 335 KIAS due to the high cost index from the delayed departure. Several times; the VNAV had created a situation where it leveled off to keep the high airspeed; and pitched up to climb rates of 1500 feet/min. At one point; in the mid 30;000 foot area; VNAV actually initiated a 300 ft/min descent to accommodate the airspeed. Climbing through FL370; max altitude was checked; and verified at 39;300. ATC had advised that the ride had been good for previous aircraft at that altitude. At approximately FL380; the mountain wave caused the VNAV to level off again; and increase speed. The climb shortly resumed. At about FL383; the opposite side of the mountain wave was experienced; and the aircraft pitched up drastically. The vsi showed about 1900 FPM. In the drastic upward rotation of the nose; the aircraft continued to accelerate. With the increased G loading; the low speed awareness tape; (red and black barber pole tape) rapidly increased upward toward the current aircraft's speed. The captain manually pushed the control yoke; in order to unload the aircraft's increasing angle of attack. In this moment; a buffet was felt in the airframe. The overspeed tape; nor underspeed tape were not intruded into; and the stall shaker was not activated. The buffet appeared to last 1-2 seconds; then disappeared. Previous mountain wave activity had been light. This was moderate; near the aircraft's calculated max altitude. During the event; the high speed and low speed barber poles were within about 20 KIAS of one another. Further moderate mountain wave was experienced; and ATC was notified that an immediate descent to FL370 was required for mountain wave. The throttles were still in climb mode; and put back there once 'crz' had been achieved. Mountain wave was +/- 15 kts; but the low speed awareness tape never came back as close as before; nor was another buffet experienced. The current procedures and new memo regarding mountain wave were discussed; as they pertain to throttle position. Descent was accomplished; and FL370 had light mountain wave for a short duration. ATC and dispatch were notified; as well as a PIREP submitted via ACARS. The rest of cruise was uneventful. However; during descent; VNAV was unable to keep up with the aircraft. Crossing restrictions with appropriate atmospheric conditions (wind; altimetry; and tai) were assured well before TOD point. As VNAV initiated the descent; it was unable to keep the pre-programed path; and subsequently went into 'VNAV spd' mode; and VNAV disconnected. These descents were not changed at the last minute before TOD; and were programmed well in advance. This overspeeding phenomenon happened 5 times. The initially programed descent speed was 280. Even at a 320-330 kts descent; the aircraft was still unable to recapture the programmed descent path. Speed brakes and 'level change' were used to meet crossing restrictions. On the ground; VNAV was written up and hub maintenance notified.

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Original NASA ASRS Text

Title: B737 First Officer reported encountering moderate mountain wave activity during climbout and cruise.

Narrative: After the inbound aircraft arrived at the gate; a quick turn was performed. During the preflight inspection; some residual ice was observed on the wings. The decision was made to deice the aircraft after push. Using the new ACARS HOT method; type 1 fluid was used to remove the residual ice. As no current icing conditions existed; only type 1 fluid was used. During the climb; the selected vertical navigation mode was VNAV; as annunciated on the FMA. During the climb; engine anti-ice was used through most of the climb; until in clear air. Some light rime ice had also built up on the leading edge of the wings. The decision was made to utilize the wing anti-ice; as we climbed through FL330. Although the air was smooth; some mountain wave had been experienced throughout the climb. The VNAV had been climbing at 335 KIAS due to the high cost index from the delayed departure. Several times; the VNAV had created a situation where it leveled off to keep the high airspeed; and pitched up to climb rates of 1500 feet/min. At one point; in the mid 30;000 foot area; VNAV actually initiated a 300 ft/min descent to accommodate the airspeed. Climbing through FL370; max altitude was checked; and verified at 39;300. ATC had advised that the ride had been good for previous aircraft at that altitude. At approximately FL380; the mountain wave caused the VNAV to level off again; and increase speed. The climb shortly resumed. At about FL383; the opposite side of the mountain wave was experienced; and the aircraft pitched up drastically. The VSI showed about 1900 FPM. In the drastic upward rotation of the nose; the aircraft continued to accelerate. With the increased G loading; the low speed awareness tape; (red and black barber pole tape) rapidly increased upward toward the current aircraft's speed. The captain manually pushed the control yoke; in order to unload the aircraft's increasing angle of attack. In this moment; a buffet was felt in the airframe. The overspeed tape; nor underspeed tape were not intruded into; and the stall shaker was not activated. The buffet appeared to last 1-2 seconds; then disappeared. Previous mountain wave activity had been light. This was moderate; near the aircraft's calculated max altitude. During the event; the high speed and low speed barber poles were within about 20 KIAS of one another. Further moderate mountain wave was experienced; and ATC was notified that an immediate descent to FL370 was required for mountain wave. The throttles were still in climb mode; and put back there once 'crz' had been achieved. Mountain wave was +/- 15 kts; but the low speed awareness tape never came back as close as before; nor was another buffet experienced. The current procedures and new memo regarding mountain wave were discussed; as they pertain to throttle position. Descent was accomplished; and FL370 had light mountain wave for a short duration. ATC and dispatch were notified; as well as a PIREP submitted via ACARS. The rest of cruise was uneventful. However; during descent; VNAV was unable to keep up with the aircraft. Crossing restrictions with appropriate atmospheric conditions (wind; altimetry; and TAI) were assured well before TOD point. As VNAV initiated the descent; it was unable to keep the pre-programed path; and subsequently went into 'VNAV spd' mode; and VNAV disconnected. These descents were not changed at the last minute before TOD; and were programmed well in advance. This overspeeding phenomenon happened 5 times. The initially programed descent speed was 280. Even at a 320-330 kts descent; the aircraft was still unable to recapture the programmed descent path. Speed brakes and 'level change' were used to meet crossing restrictions. On the ground; VNAV was written up and hub maintenance notified.

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.