Surely the point of the CDL penalty is that you start with normal planning and then simply apply the weight and fuel penalty. That does not need a computer, even though it will be done on one. The penalty is crude and conservative, therefore the penalised aircraft will in reality perform better but less efficiently than one dispatched at normal weight/configuration.
Fuel Penalty application is crystal clear but weight is not. I am not mentioning FMS calcualtion, I am talking about planning calculation. How to use weight penalty for planning purpose? Adding CDL penalty weight to actual weight is
not a solution, That only helps to figure out what will be the capability of gross ceiling with this CDL penalty, which new gross ceiling is always less than the actual weight. But this has "
NO RELATION" with NET CEILING. This calculation never gives an idea about driftdown NET CEILING path and NET CEILING VALUE, therefore we may not be aware whether this new NEt CEILING path and vaue is conflicting with enroute terrain/obstacles or not.