Aft c of g = improved TOP
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MMouse,
Interesting point, and I can admit to being partly responsible for giving a loadsheet to a crew that indicated an aft cg position when the ac was loaded from the front; and had in reality a cg near the fwd limit.
The crew consequently trimmed the ac nose down (with a fwd cg) and only just hauled it off the deck according to the F/O.
Interesting point, and I can admit to being partly responsible for giving a loadsheet to a crew that indicated an aft cg position when the ac was loaded from the front; and had in reality a cg near the fwd limit.
The crew consequently trimmed the ac nose down (with a fwd cg) and only just hauled it off the deck according to the F/O.
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FH,
Thanks for that .. and what would be a typical CG/IU co-ordinate for the loading when you would consider rearranging the load to move the cg aftwards ?
I don't have any 800 background .. but on the earlier models .. it gets interesting if the cg is aft and the trim set for forward ... the aircraft wants to leap off the ground at an alarmingly low speed .. gets the chaps' (or ladies' or chap's and lady's) attention very quickly ..
Thanks for that .. and what would be a typical CG/IU co-ordinate for the loading when you would consider rearranging the load to move the cg aftwards ?
I don't have any 800 background .. but on the earlier models .. it gets interesting if the cg is aft and the trim set for forward ... the aircraft wants to leap off the ground at an alarmingly low speed .. gets the chaps' (or ladies' or chap's and lady's) attention very quickly ..
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At close to MTOW of 79t the approximate position would be MAC 25 with 64 index units,interestingly at 78t the aft limit extends to MAC 32 with 82 index units, hope this makes sense.
As an aside to all this we did suffer a 738 tailstrike this week, no damage, and nothing to do with the cg but nasty anyway...
As an aside to all this we did suffer a 738 tailstrike this week, no damage, and nothing to do with the cg but nasty anyway...
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FH,
Just two quick questions of clarification ..
(a) in the earlier post re envelope intersections, could I get you to recheck the weight and MAC information, please ?
(b) in your last post, the 79T/25MAC is before or after you have changed the loading ? .. if, as I suspect, after, what was the original loading IU ?
Just two quick questions of clarification ..
(a) in the earlier post re envelope intersections, could I get you to recheck the weight and MAC information, please ?
(b) in your last post, the 79T/25MAC is before or after you have changed the loading ? .. if, as I suspect, after, what was the original loading IU ?
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OK;
(a) Data is correct but bear in mind that I am taking it from the manual loadsheet specimen and it is not the best basis for manually plotting the c.g envelope.
(b) The target MAC for MTOW 79t will normally be around about mac 18%/38 index units,( I guess it varies according to loading on the day) my original query arose for this post because at certain airports the take off perf. computer would limit me to lets say 78t
due to runway length, assuming MAC of around 18%,I would then input MAC25% (theoretically move c.g. aft) and recalculate the data, and would normally find an extra 500 to 1000kgs.
RGDS FH
(a) Data is correct but bear in mind that I am taking it from the manual loadsheet specimen and it is not the best basis for manually plotting the c.g envelope.
(b) The target MAC for MTOW 79t will normally be around about mac 18%/38 index units,( I guess it varies according to loading on the day) my original query arose for this post because at certain airports the take off perf. computer would limit me to lets say 78t
due to runway length, assuming MAC of around 18%,I would then input MAC25% (theoretically move c.g. aft) and recalculate the data, and would normally find an extra 500 to 1000kgs.
RGDS FH
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I think I would need to look through the AFM and the WB manuals to form a definite opinion. The trimsheet data should be fine as the only envelope changes will be truncations etc. in the envelope to accommodate the error analysis.
My best guess at this stage is that the answer to the first question would end up being just a matter of following the forward limit up to the higher weight .. by moving aft, the limit permits a higher weight ....
regards....
My best guess at this stage is that the answer to the first question would end up being just a matter of following the forward limit up to the higher weight .. by moving aft, the limit permits a higher weight ....
regards....
