NAVWEPS OD-ROT-80 
APPLICATION OF AERODYNAMICS 
TO SPECIFIC PROBLEMS OF FLYING 
speed, the distance necessary to continue take- 
off with one engine inoperative is equal to the 
stopping distance. The critical engine failure 
speed is generally referred to as the “I’,” 
speed and it is a function of the same factors 
which determine the takeoff performance, e.g., 
density altitude, gross weight, temperature, 
humidity, etc. 
(3) &t&l jield kngrh: The runway length 
necessary to accelerate with all engines opera- 
tive to the critical engine failure speed (VJ 
then continue accelerating to the takeoff and 
initial climb speed (VJ with one engine 
inoperative and achieve safe takeoff or refuse 
takeoff. By this definition, critical field 
length describes the minimum length of run- 
way necessary for safe operation of the multi- 
engine airplane. Obviously, the critical field 
length is a function of the same factors affect- 
ing the takeoff distance of the airplane. 
The conditions of Vi, V,, and critical field 
length are illustrated by figure 6.13. The 
first illustration of figure 6.13 depicts the 
case where the runway length is equal to the 
rritical jield kngth. In this case, the airplane 
could accelerate to Vi with all engines opera- 
tive then either continue takeoff safely with 
one engine inoperative or refuse takeoff and 
decelerate to a stop on the remaining runway. 
For this condition, an engine failure occurring 
at lefs than I’, speed dictates that takeoff must 
be refused because inadequate distance remains 
to effect a safe takeoff at V, speed. However, 
at or below V, speed, adequate distance re- 
mains to bring the airplane to a stop. If 
engine failure occurs at some speed greater 
than Vi speed, takeoff should be continued 
because adequate distance remains to accelerate 
to V, speed and effect a safe takeoff with one 
engine inoperative. If engine failure occurs 
beyond Vi speed, inadequate distance remains 
to brake the airplane to a stop on the runway, 
The second illustration of figure 6.13 depicts 
the case where the ranway length is 1~s than 
the titical field length. In this case, the term 
of “V,” speed is not applicable because of 
inadequate distance and the refusal speed is 
less than the minimum speed necessary to 
continue a safe takeoff with one engine inoper- 
ative. If engine failure occurs below refusal 
speed, the takeoff must be refused and adequate 
distance remains to effect a stop on the runway. 
If engine failure occurs above refusal speed 
but below the minimum speed necessary to 
continue takeoff with one engine inoperative, 
an accident is inevitable. Within this range 
of speeds, the airplane cannot effect a safe 
takeoff at L’s with one engine inoperative or 
a safe stop on the remaining runway. For this 
reason, the pilot must properly plan the 
takeoff and insure that the runway available 
is equal to or greater than the critical field 
length. If the runway available is less than 
the critical field length, there must be sufficient 
justification for the particular operation be- 
cause of the hazardous consequences of engine 
failure between the refusal speed and the 
minimum speed necessary to continue takeoff 
with one engine inoperative. Otherwise, the 
gross weight of the airplane should be reduced 
in attempt to decrease the critical field length 
to equal the available runway. 
SONIC “BOOMS’ 
From the standpoint of public relations 
and the maintaining of friendly public support 
for Naval Aviation, great care must be taken 
to prevent sonic booms in populated areas. 
While the ordinary sonic boom does not carry 
any potential of physical damage, the disturb- 
ance must be avoided because of the undesirable 
annoyance and apprehension. As supersonic 
flight becomes more commonplace and an 
ordinary consequence of flying operations, the 
prevention of sonic booms in populated areas 
becomes a difficult and perplexing job. 
When the airplane is in supersonic flight,