NAVWEPS DD-8OT-80 
APPLICATION OF AERODYNAMICS 
TO SPECIFIC PROBLEMS OF FLYING 
later portions of takeoff if the airplane is un- 
able to become airborne or if insufficient margin 
above stall speed prevents successful initial 
climb, In no circumstances should a formation 
of ice or frost be allowed to remain on the air- 
plane wing surfaces prior to takeoff. 
ENGINE FAILURE ON THE MULTIENGINE 
AIRPLANE 
In the case of the single-engine airplane, 
power-plant failure leaves only the alternatives 
of effecting a successful power-off landing or 
abandoning the airplane. In the case of the 
multiengine airplane, the failure of a power- 
plant does nor necessarily constitute a disaster 
since flight may be continued with the remain- 
ing powerplants functioning. However, the 
performance of the multiengine airplane with 
a powerplant inoperative may be critical for 
certain conditions of flight and specific tech- 
niques and procedures must be observed to 
obtain adequate performance. 
The effect of a powerplant failure on the 
multiengine turbojet airplane is illustrated by 
the first chart of figure 6.8 with the variation 
of required and available thrust with velocity. 
If half of the airplane powerplants are inoper- 
ative, e.g., single-engine operation of a twin- 
engine airplane, the maximum thrust available 
at each velocity is reduced to half that avail- 
able prior to the engine failure. The variation 
of thrust required with velocity may be 
affected by the failure of a powerplant in that 
there may be significant increases in drag if 
specific procedures are not followed. The 
inoperative powerplant may contribute addi- 
tional drag and the pilot must insure that the 
additional drag is held to a minimum. In the 
case of the propeller powered airplane, the 
propeller must be feathered, cowl flaps closed. 
etc., as the increased drag will detract con- 
siderably from the performance. 
The principal effects of the reduced available 
thrust are pointed out by the illustration of 
figure 6.6. Of course, the lower available 
thrust will reduce the maximum level flight 
speed but of greater importance is the reduc- 
tion in excess thrust. Since the acceleration 
and climb performance is a function of the 
excess thrust and power, the failure of a power- 
plant will be most immediately appreciated in 
this area of performance. As illustrated in 
figure 6.8, loss of one-half the maximum avail- 
able thrust will reduce the excess thrust to less 
than half the original value. Since some 
thrust is required to sustain flight, the excess 
which remains to accelerate and climb the 
airplane may be greatly reduced. The most 
critical conditions will exist when various 
factors combine to produce a minimum of 
excess thrust or power when engine failure 
occurs. Thus, critical conditions will be com- 
mon to high gross weight and high density altitude 
(and high temperatures in the case of the 
turbine powered airplane) as each of these 
factors will reduce the excess thrust at any 
specific flight condition. 
The asymmetrical power condition which 
results when a powerplant fails can provide 
critical control requirements. First consid- 
eration is due the yawing moment produced 
by the asymmetrical power condition. Ade- 
quate directional control will be available 
only when the airplane speed is greater than 
the minimum directional control speed. Thus, 
the pilot must insure that the flight speed never 
falls below the minimum directional control 
speed because the application of maximum 
power on the functioning powerplants will 
produce an uncontrollable yaw if adequate 
directional control is unavailable. A second 
consideration which is due the propeller 
powered airplane involves the rolling moments 
caused by the slipstream velocity. Asym- 
metrical power on the propeller airplane will 
create a dissymmetry of the slipstream veloc- 
ities on the wing and create rolling moments 
which must be controlled. These slipstream