126 AEROPLANE PERFORMANCE CALCULATIONS 



V. 



V T . 



Altitude. 



It will be remembered that / = -161 and q = '839 for 

 stationary engines, while / = -262 and q = 738 for rotary 

 engines. 



Then fill up the first two columns with the values V lf V 2 , etc., 

 and V T1 , V T2 , etc., work out the next three columns, and then 

 fill up the last column with the aid of the curve of page 104. 



Now plot altitude against V and note the maximum value 

 of the altitude (which is the maximum ceiling) and the value of 

 V at which it occurs (which is the Air Speed Indicator Reading 

 at the ceiling). 



III. THROTTLED FLIGHT. 



Slowest Flying Speed. The slowest flying speed is differ- 

 ent from the landing speed on glide, already found on page 1 16. 

 The slowest flying speed can be read directly off the machine 

 performance curve if this has been found by the Third Method 

 or the Fourth Method : if the curve has been plotted, the speed 

 can be read off the plotting: if not it can be read off the V 

 column for the case of X = I'O, see page 1 1 1 or page 114. If 

 the minimum flying speed at an altitude is required, reference 

 must be made to the plottings of P' and P T ' on V for that alti- 

 tude, as the P T ' curve sometimes cuts off the slowest part of the 

 P' curve at great heights. 



If the Third Method or Fourth Method has not been used, 

 the only thing is to work along the \ = I'O line of the table of 

 the Third Method till the V column is reached. 



Throttling Curves. A set of throttling curves scribed on 

 celluloid is constantly wanted in performance calculations. If 

 these are not available they should therefore be made. 



