Cg
 

Hi all,

On the B737NG FMC Perf Init page you can enter a cg percentage. Ongoing discussions haven't made it clear what to use (5%, 12%, 18%) and why.

Any thoughts?

The figure for T/Off CofG from the loadsheet. On the NG with the correct Flap setting entered it produces trim setting.

I reckon you may be a little mixed up there, my learned colleague.

The CG entry on the Takeoff Ref page is to provide a takeoff Stab Trim setting, but the Perf Init CG is a CRZ CG and in turn affects the calculations of the buffet margins and therefore Optimum/Maximum Cruise Alts displayed on the CRZ page.

You can interpolate a Top of Climb CG from your trim sheet.

Absolutely, Yusef, but in the absence of any other figure......it will not be far adrift? I often have a look at max cruise altitude before push-back.

I'm (obviously) not sitting in the cockpit right now, but I recall the trim scale has (had?) MAC points on it that you could use in the cruise?

For Killroy - be aware that your company SOPs should dictate what you do. A lot of companies say to leave the perf init value alone, although it will (always?) improve cruise altitude and therefore fuel burn if set away from the 'default'. If in doubt, ask 'the mangement'.