ECON cruise, LR cruise...
Join Date: Apr 2002
Location: MIRSI hold - give or take...
Age: 52
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Your AFM and/or OM should contain a section on adverse weather, including turbulence. Normally, you want to fly a speed just below Va, since this will give you optimum protection from both stall & overstress.
On the 737, we fly .73 (.76 for the NG) / 280 KIAS - however, when mass is below 50T, we reduce this to 250 KIAS.
I know naught about the MDs, but it sounds a s though the TURB-mode you describe is more minded on being a reactionary mode rather than a preventive mode, i.e. if the turbulence becomes so serious that maintaining speed/atitude might overload the aircraft - we have a (almost corresponding) setting called CWS, where the AP maintains the attitude we have set. Also we have to disconnect the A/T and set turbulence N1 manually - so it sounds as a smart idea to have it all combined in just one push-button.
However, we wouldn't go to CWS/ Turb N1 untill we actually hit turbulence of some severity - up to that point, we'd just fly .76/280/250 with A/T engaged & normal lateral & vertical modes. For descend, if we feel it prudent to limit the vertical speed & have the engines spooled up, we'd use VS & MCP SPEED.
Hope this helps - cheers fm
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