NAVWEPS 00-ROT-80 
OPERATING STRENGTH LIMITATIONS 
due to the gust condition are higher. This is 
explained by the fact that essentially the 
same lift change acts on the lighter mass. 
The high accelerations and inertia forces 
magnify the impression of the magnitude of 
turbulence. If this same airplane encounters 
the gust condition at higher than ordinary 
gross weight, the accelerations due to the gust 
condition are lower, i.e., the same lift change 
acts on the gteatet mass. Since the pilot 
primarily senses the degree of turbulence by 
the resulting accelerations and inertia forces, 
this effect can produce a very misleading 
impression. 
The effect of airspeed and altitude on the 
gust load factor is important from the stand- 
point of flying operations. The effect of alti- 
tude is related by the term &, which would 
related that an airplane flying at a given EAS 
at 40,000 ft. (c=O.25) would experience a 
gust load factor increment only one-half as 
great as at sea level. This effect results be- 
cause the true airspeed is twice as great and 
only one-half the change in angle of attack 
occurs for a given gust velocity. The effect of 
airspeed is illustrated by the linear variation 
of gust increment with equivalent airspeed. 
Such a variation emphasizes the effect of gusts 
at high flight speeds and the probability of 
structural damage at excessive speeds in turbu- 
lence. 
The operation of any aircraft is subject to 
specific operating strength limitations. A 
single large overstress may cause structural 
failure or damage severe enough to require 
costly overhaul. Less severe overstress re- 
peated for sufficient time will cause fatigue 
cracking and require replacement of parts to 
prevent subsequent failure. A combat airplane 
need not be operated in a manner like the “little 
old lady from Pasadena” driving to church on 
Sunday but each aircraft type has strength 
capability only specific to the mission require- 
ment. Operating limitations must be given 
due regard. 
THE V-B OR V-g DIAGRAM 
The operating flight strength limitations of 
an airplane are presented in the form of a 
V-‘-n or V-g diagram. This chart usually is 
included in the aircraft flight handbook in the 
section dealing with operating limitations. 
A typical V-n diagram is shown in figure 5.3. 
The V-n diagram presented in figure 5.3 is 
intended to present the most important general 
features of such a diagram and does not neces- 
sarily represent the characteristics of any par- 
ticular airplane. Each airplane type has its 
own particular V-n diagram with specific V’s 
and n’s, 
The flight operating strength of an airplane 
is presented on a graph whose horizontal scale 
is airspeed (V) and vertical scale is load factor 
(n). The presentation of the airplane strength 
is contingent on four factors being known: 
(I) the aircraft gross weight, (2) the configura- 
tion of the aircraft (clean, external stores, flaps 
and landing gear position, etc.), (3) symmetry 
of loading (since a rolling pullout at high speed 
can reduce the structural limits to approxi- 
mately two-thirds of the symmetrical load 
limits) and (4) the applicable altitude. A 
change in any one of these four factors can 
cause important changes in operating limits. 
For the airplane shown, the positive limit 
load factor is 7.5 and the, positive ultimate 
load factor is Il.25 (7.5x1.5)- For negative 
lift flight conditions the negative’limit load 
factor is 3.0 and the negative ultimate load 
factor is 4.5 (3.0x1.5). The limrt airspeed is 
stated as 575 knots while the wing level stall 
speed is apparently 100 knots. 
Figure 5.4 provides supplementary informa- 
tion to illustrate the significance of the V-n 
diagram of figure 5.3. The lines of maximum 
lift capa’bility are the first points of importance 
on the’ V-n diagram. The subject aircraft is 
capable bf developing no more than one posi- 
tive “g” at 100 knots, the wing level stall speed