NAVWEPS 00-801-80 
AIRPLANE PERFORMANCE 
will cause these approximate increases in 
takeoff distance: 
3% percent for the supercharged recipro- 
cating airplane when below critical 
altitude 
7 percent for the turbojet with high thtust- 
to-weight ratio 
10 percent for the turbojet with low 
thrust-to-weight ratio 
These approximate relationships show the 
turbojet airplane to be much more sensitive to 
density altitude than the reciprocating powered 
airplane, This is an important fact which 
must be appreciated by pilots in transition 
from propeller type to jet type airplanes. 
Proper accounting of pressure altitude (field 
elevation is a poor substitute) and temperature 
is mandatory for accurate prediction of takeoff 
roll distance. 
The most critical conditions of takeoff 
performance are the result of somecombination 
of high gross weight, altitude, temperature 
and unfavorable wind. In a11 cases, ir be- 
hooves the pilot to make an accurate prcdic- 
tion of takeoff’ distance from the performance 
data of the Flight Handboo& regardless of the 
runway available, and to strive for.2 polished, 
professional takeoff technique. 
In the prediction of takeoff distance from 
the handbook data, the following primary 
considerations must be given: 
Reciprocating powered airplane 
(1) Pressure altitude and temperature- 
to define the effect of density altitude on 
distance. 
(2) Gross weight-a large effect on dis- 
tance. 
(3) Specific humidity-to correct cake- 
off distance for the power loss associated 
with water vapor. 
(4) Wind-a large effect due to the wind 
or wind component along the runway. 
Turbine powered airplane 
(I) Pressure altitude and temperature- 
to define the effect of density altitude. 
(2) Gross weight. 
(3) Temperature--an additional correc- 
tion for nonstandard temperatures to ac- 
count for the thrust loss associated with 
high compressor inlet air temperature. 
For this correction the ambient tempera- 
ture at the runway conditions is appro- 
priate rather than the ambient temperature 
at some distant location. 
(4) Wind. 
In addition, corrections are necessary to ac- 
count for runway slope, engine power defi- 
ciencies, etc. 
LANDING PERFORMANCE. In many 
cases, the landing distance of an airplane will 
define the runway requirements for flying 
operations. This is particularly the case of 
high speed ‘jet airplanes at low altitudes where 
landing distance is the problem rather than 
takeoff performance. The minimum landing 
distance is obtained by landing at some mini- 
mum safe velocity which allows sufficient mar- 
gin above stall and provides satisfactory, con- 
trol and capability for waveoff Generally, 
the landing speed is some fixed percentage of 
the stall speed or minimum control speed for 
the airplane in the landing configuration. As 
such, the landing will be accomplished at 
some particuIar value of ~lift coefficient and 
angle of attack. The exact value of CL and 
P for landing will depend on the airplane 
characteristics but, once defined, the values are 
independent of weight, altitude, wind, etc. 
Thus, an angle of attack indicator can be a 
valuable aid during approach and landing. 
To obtain minimum landing distance at the 
specified landing velocity, the forces which 
act on the airplane must provide maximum 
deceleration (or negative.acceIeration) during 
the landing roll. The various forces actin~g. 
on the airplane during the landing roll may 
require various techniques to maintain landing 
deceleration at the peak value. 
Figure 2.34 illustrates the forces acting on 
the aircraft during landing roll. The power- 
plant thnrJt should be a minimum positive 
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