B737 MAX flight crew reported the trailing edge flaps did not retract properly during departure. After running checklists; it was determined that the aircraft needed to burn off fuel and divert for a precautionary landing.
Synopsis
B737 MAX flight crew reported the trailing edge flaps did not retract properly during departure. After running checklists; it was determined that the aircraft needed to burn off fuel and divert for a precautionary landing.
Narrative
After takeoff from ZZZ we realized the flap gauge showed the left indicator less than the 'UP' position. The right indicator showed up. The left indicator was slightly below the right indicator meaning both flaps were up. At no point in time were the indicators between up and one meaning not extended. We did not think this was possible and thought it was a gauge anomaly; very similar; that we sometimes see on the -700s and old -300s. No roll; abnormal trim; adverse yaw or increased fuel burn were present. Neither Pilot had ever seen that before. No checklist exists. I have never seen anything in our manuals and there has never been any Flight Operations communication about this; to my knowledge. While preparing to land I called for flaps 5; but the flaps did not extend. We performed a go-around and ran the Flap Trailing Edge Disagree Checklist. Due to the slight asymmetry; we believed that might be the issue. We followed The Trailing Edge Flap Asymmetry Checklist. The flap lever was now set to 'UP' to match the flap setting. This checklist directed us to go to the Trailing Edge Flaps Up Checklist. The checklist directs the Alternate Flaps Master Arm switch to ARM. It then directs the Alternate Flap switch to be positioned; momentarily; to down. The leading edge devices were now full down and could not be raised. After this step in the checklist; it directs us to compute non-normal performance data landing data. After computing our landing data; we realized that we did not have enough runway at ZZZ1 and then diverted to ZZZ2 for a long runway. By following the checklist; computing performance data landing data after extension of the leading edge devices; put us in a lower than desired fuel state. If the flap gauge anomaly is known by Boeing or the Company; then we believe it should be known to the Pilot group. By moving the compute performance data non-normal checklist step ahead of extending the leading edge devices would help Flight Crews make a more appropriate decision if a diversion is needed. Running the performance data; you can determine if you are capable of landing or need to divert; prior to extending the leading edge devices. This will then give you a more fuel-efficient divert with more fuel buffer.
Second reporter narrative
After takeoff from ZZZ; we realized the flap gauge showed the left flap more than the 'up' position; not extended; but above zero. I don't believe this is possible and we believed this to be a flap gauge anomaly. No roll; abnormal trim; adverse yaw or higher than normal fuel burn was noticed. Neither Pilot had ever seen that before; no checklist exists; I have never seen anything in our manuals about this and there has never been any flight operations communication about this; we therefore believed it to be an anomaly and we treated it as such.While preparing to land approximately five hours later in ZZZ1; I selected flaps 5; but the flaps remained in the UP position; so we went around and ran the Flap Trailing Edge Disagree Checklist. Due to the slight asymmetry that we then believed may be an issue; we elected to follow the Trailing Edge Flap Asymmetry Checklist. As the lever was set to 'UP' to match the flap setting; the checklist directed us to go to the Trailing Edge Flaps Up Checklist.This checklist directs to go to step X if an asymmetry exists. Step X directs the ALTERNATE FLAPS master arm switch to ARM. Step Y directs the ALTERNATE FLAPS switch to be positioned momentary DOWN. This extends the leading edge devices to full down and they cannot be raised. All devices indicated full EXT. After ensuring they are all down; the checklist directs to consider burning off fuel to reduce landing weight. Our fuel state was fairly low; so we didn't need to do that. Step Z directs to compute non-normal performance data landing data. It was at that point after computing our landing data; we realized that we did not have sufficient runway and could not land in ZZZ1. We diverted to ZZZ2 for the longer runway. By following the checklist; computing performance data after extending the leading edge devices; we put ourselves into a lower than desired fuel state.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.