Dry Rwy stp perf with reverse and CRZ CG
Dear all,
I have been reading about performance for years, and still, there are a few gaps I need to fill, and even people who know much more than I do don't seam to know some specific points.
Recently a Boeing Performane Engineer came to our company for a presentation, It was for me a great opportunity to ask what I always wanted to know, and his answer was not so clarifying.
WHY MANY PUBLICATIONS, AND EVEN BOEING TAKEOFF AND LANDING PERFORMANCE PRESENTATIONS STATES THAT REVERSE THRUST HAVE NO EFECT ON STOPING DISTANCE ON DRY RWY WHEN AUTO BRAKES ARE USED (IT MAY HAVE EFFECT ON SLIPPERY RWY), AND WHEN YOU LOOK AT THE QRH UNFACTORED LANDING REFERENCE TABLES YOU CAN SEE THAT IT DOES, AS THE LAST COLLUM AT THE RIGHT FOR DRY AND WITH SOME AUTO BRAKE SETTINGS (DEPENDING ON ACFT TYPE) IS NOT ZERO.
So far I could not get a definitive explanation.
Is it the same for Airbus performance figures?
By the way, JAA requires the CRZ CG for performance calculation (CDU/FMC input that will generate MAX ALT information) to be in the most fwd figure (8.5 for the B744). We have a default of 20 in my company. What are you using? do you have a procedure to change the CG value in flight? Are you using 8.5 ?
Thanks a lot in advance for all good information and interest.
Ric