Flight spoilers will not raise to within limits with speed brake handle fully deployed. 737-3/4/500

Problem: Flight spoilers will not raise to within limits with speed brake handle fully deployed

Background: While performing Op’s checks on the spoilers and speed brakes due to removing the aileron mixer for ratio changer “No Back” check we could not get the 38 plus or minus 2 degrees on the #2,3,6 & 7 flight flight spoilers when the speed brake lever was fully deployed.

Situation: The aileron system including the trim and flight spoiler cable were correctly rigged and cable runs OK. The system was correctly rigged and we tried a new mixer but it did not work so we tried a new ratio changer but it still did not work. We made numerous adjustments to the SBA & SBB (speed brake) cables but without results. We found a reference in the AMM to a “stop” on the ratio changer so we pulled the upper I/B cover on the ratio changer and noticed the input pulley/quadrant for the SBA & SBB cable was not contacting the stop nor it had the freedom to do so. We installed another ratio changer and reinstalled the original aileron mixer – problem solved. The newly overhauled ratio changer was defective. There is an easy way to see if the SBA & SBB input quadrant on the ratio changer is traveling far enough: When the quadrant is turned counter clockwise (looking fwd) the lower cable retainer on the pully will come within a few thousands of an inch (ours was about .250)

Thanks to David A. for his input !


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