It is recommended that the total car load be not  allowed to exceed 18,300 lbs., or 2300 lbs. over the design  Under such condition of 2300 lbs. "Design Heaviness"  the factors of safety are reduced to about 2.6 for the car  structure and about  3.5  for the car suspension.  "Flight heaviness" alone is no measure of the factors  of safety of the car structure and suspension.  Under condi tiofls of high lift there may be no  "flight heaviness" but a high "design heaviness."  Under conditions of low lift there may be no  "design heaviness" but a high "flight heaviness."  Preceeding pages show computations of a typical car  load.  It is suggested that similar forms be used for actual  computations before take-off.  NOTE:  "Design heaviness" is the excess of car load over  design load -a.nd should not be confuseq. with "flight  heaviness" which is the excess of gross load over  gross lift.  -21-