AIRPLANE PERFORMANCES — HAMLIN AND SPENCELEY 449 



Finally, the total airplane drag vs. true air speed is depicted in fig- 

 ures 15, 16, and 17. These curves, together with those in part A of this 

 paper, provide the necessary data for the performance evaluations 

 given below. 



The drag curves shown are for the highest airplane weights obtain- 

 ing after climbing to the respective altitudes. Gross weight variation 

 has been taken into account wherein performance is affected. 



Figure 17. — Airplane drag at 40,000 feet. 



2. Maximum speeds and best climbing speeds (fig. 18) . — Maximum 

 speed of the propeller airplane is 480 miles per hour at 25,000 feet, 

 indicating that the practical high speed limit for this type of pro- 

 pulsion will not greatly exceed 500 miles per hour. At all altitudes 

 up to 40,000 feet a speed greater than 400 miles per hour is attainable, 

 although 400 miles per hour at sea level seems slow for ground-strafing 

 work. Best climbing air speed is relatively low, being 50 to 55 per- 

 cent of maximum level flight speed between sea level and critical 

 altitude, respectively. 



