Today, there are more aircraft modification contracts being awarded then ever before. This paper is being presented so that the problems experienced on some modification programs the author has been involved in can be aired. The hope is that it will be of useful value to others that find themselves in similar situations.

The scope of the weight and center of gravity control exerted on modification programs will vary greatly. Some of the factors affecting the depth of the mass properties control are the size and extent of the modification and the degree of complexity of the present aircraft.

The program schedules for modification contracts, by their very nature, are very tight. There are design decisions that are made on a daily basis which are too often influenced by the program scheduling pressures that exist at that particular moment. These early design decisions can be trend-setters. They can set precedents and establish a mental attitude in the minds of designers and system cognizant engineers that could be harmful to the mass properties effort.

The intent of this paper is not to attempt to give all encompassing rules to be followed but to highlight that a mass properties control awareness, philosophy and strategy should be formulated that is available for a particular program.