B767 flight crew reported during flap retraction after takeoff; the speed indicator jumped above the aircraft speed and the stick shaker activated. Flight crew performed stall recovery and continued flight.
Synopsis
B767 flight crew reported during flap retraction after takeoff; the speed indicator jumped above the aircraft speed and the stick shaker activated. Flight crew performed stall recovery and continued flight.
Narrative
Aircraft X was cleared on the ZZZZZ departure. Threats for the flight were high altitude; high terrain and cargo was loaded to max performance takeoff gross weight. Captain was pilot monitoring. Pratt & Whitney engines.We were on the ZZZZZ departure and had completed the 7500 foot turn at 185 kn and we're proceeding direct to ZZZ [VOR]. We were accelerating to 229 kn and had completed the flap retraction from flaps 5 to flaps 1. Because the pilot monitoring was talking to departure the flap retraction was delayed significantly past flaps five maneuvering speed. The minimum maneuvering; yellow speed; tape fluctuated significantly; but nothing abnormal happened. However; when the pilot flying called for flaps up at approximately flaps1 maneuvering speed +10 to 15 kn; the pilot monitoring retracted the flaps to flaps up. The auto pilot was engaged; and the planes performance was accelerating very slowly. It appeared the second the flat handle was retracted the Minimum maneuvering yellow tape immediately jumped approximately 10 to 20 kn increase. This put the minimum maneuvering speed past the current speed. This caused a one second stick shaker. The pilot flying immediately followed company procedures disconnected the auto pilot. Decrease pitch and increase speed. In the captains opinion; the maneuver was completed perfectly according to our procedures. After reaching cruise the entire crew separately reevaluated the weight and balance And performance. And could not find any flaws in the data.Flight proceeded normally until arrival on the ZZZZZ1 arrival into ZZZ . ZZZ approach was very busy and we were asked to significantly slow to 170 kn. As the crew slowed the aircraft and extended flaps; we noticed with every flap extension; from flaps 1 to flaps 25; the minimum maneuvering yellow bar Increased significantly; approximately 10 to 20 kn with each extension. However; no significant events occurred in performance to the airplane. But we were constantly just above the minimum maneuvering yellow tape. The captain has been flying the 767 for over nine years and has never witnessed such a significant increase with the minimum maneuvering yellow tape before. It is normal to see the minimum maneuvering yellow tape adjusted itself with flap changes in a slow controlled way as the flaps are extend and retract. However; on this flight; the minimum maneuvering yellow tape was almost instantly increasing 10-20 kn at all flap changes. This seemed very abnormal to the captain; so he made a write up in the logbook; addressing what appeared to be this problem. It is not known at this time what maintenance action was taken or what was found.In the captains opinion; one or possibly two things caused the stick shaker. Inaccurate air data information being fed to the speed tape minimum maneuvering yellow bar. Or the crew was given inaccurate cargo weights; and the plane was possibly overloaded. It is the captains opinion after thinking about this while on layover in ZZZ that it appears the plane was overloaded.Because the crew had followed company procedures and only retracted the flaps and extended the flaps well within the safe company operating guidelines it is not known what could have been done differently to prevent the situation. At the time of the stick shaker event it could not have been known that the minimum maneuvering yellow tape was going to increase so significantly with flaps up retraction. As we stated before we were at least flaps 1 maneuvering speed +10.
Second reporter narrative
This report was written approximately 36 hours after the event and is generated as best recalled from memory by the pilot monitoring. We departed out of ZZZZ-ZZZ as Aircraft X off RWY XX on the ZZZZZ [departure]. On climbout; we complied with all departure procedure restrictions. During acceleration as the PF; I called for flap retraction approximately 10 KTS above minimum maneuvering speed for the current flap setting. As the CA moved the flap handle from 5 to 1; it caused the Minimum Maneuvering Speed Amber Bar to increase approximately 10 KTS. As the flap handle was moved to the UP position; the Amber Bar rapidly increased through our current speed to the stick shaker activation point. The stick shaker activated at 218 KTS for one second. As PF; I complied with the stall procedure; we then re-automated the aircraft and had no further issue.We experienced the same issue with the Minimum Maneuvering Speed Amber Bar during our arrival and approach phase into ZZZ. We were slowed early to 170 KTS for sequencing and experienced a rapid 10-20 KT increase in the Amber Bar while extending flaps. Our final target speed on approach put us just a few knots above minimum maneuvering speed.As a high-altitude airport; the aircraft was sluggish to accelerate; but we were well above our minimum flap retraction speed and accelerating when as PF; I called for flap retraction. The movement of the Amber Bar seemed abnormal and aggressive on this aircraft. I have operated out of ZZZZ as PF several times before and have never experienced this issue.Cause: 1. Mechanical 2. Discrepancy between the Weight and Balance and the actual aircraft weight.The CA wrote up the rapid movement of the amber bar as it increased 10-20 KTS with movement of the flap handle.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.