Aft CoG Take Off Performance
Join Date: Sep 1998
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Age: 55
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TO performance is calculated with the most restrictive CG. This is normally full forward as it requires the most trim load.( downforce from the stab). Some manufacturers will offer (for a fee) take off data calculated with a more aft cg. Less stab trim down force will give better performance. If this option is used there will be a maximum forward cg restriction imposed for take off.
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I don't know whether this is implemented on any large aircraft but a constraint on forward CG will see a reduction in stall speed which could be used to effect a lower takeoff speed schedule with an associated RTOW increase for a short to medium runway.
Certainly, I have seen several light aircraft where a constraint on the upper forward CG has been made to keep stall speeds acceptable for the AFM.
Certainly, I have seen several light aircraft where a constraint on the upper forward CG has been made to keep stall speeds acceptable for the AFM.
Join Date: Mar 2001
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The 737 offers two different alternate forward CG settings for greater performance margin or more thrust reduction.
As long as we did our w&b ourselfs on our EFBs and the w&b program directly interfaced into the take off performance and the correct alternate forward CG option was automatically chosen. Now that we get ACARS loadsheets we usually don't bother with it as the difference in performance is rather small, but in a real limiting situation i would check what difference it makes. On our 700s option 1 is at or above 15% MAC and option 2 at or above 20% available, on the 800s it is 20% and 25%.
As long as we did our w&b ourselfs on our EFBs and the w&b program directly interfaced into the take off performance and the correct alternate forward CG option was automatically chosen. Now that we get ACARS loadsheets we usually don't bother with it as the difference in performance is rather small, but in a real limiting situation i would check what difference it makes. On our 700s option 1 is at or above 15% MAC and option 2 at or above 20% available, on the 800s it is 20% and 25%.
