Savage Cub Australian Flight Manual © X-Air Australia 2008 Release 1.2 Page 36 of 40
Weight in
Kg Arm in cm
Moment
1 Left Landing Gear
133
154
20482
2 Right Landing Gear
132.5
154
20405
3 Pilot
120
170
20400
4 Fuel
45
193
8615.52
6 Baggage Compartment
10
307
3070
7 Tail Wheel
25.5
593
15121.5
Total Weight
465.64
88094.02
C.G.
189.2
Acceptable range of CG from 188 cm to
205cm
Load Factors Information for Pilots
It is necessary that every effort be made to determine in advance the worst loads likely to be
put on an airplane during its lifetime. Any pilot can make a very hard landing or an extremely
abrupt pull-up from a dive resulting in loads that might be called abnormal. For that matter, he
might even fly the airplane into a brick wall. These abnormal loads must be ignored entirely if
we are to build airplanes that will take off quickly, land slowly, and carry a good payload. We
must decide that the ~ airplane will sustain certain loads and that the pilots are aware of the
fact that abnormal loads are not provided for in the design of the airplane. These
requirements must be carefully calculated so as to produce efficient as well as safe airplanes.
An efficient airplane must be light while a safe airplane must be strong. Extra strength means
extra weight which means reduced payloads. An airplane, unlike a bridge or building, cannot
afford to have any excess structural weight beyond that which is essential for safety.
In level flight, the net result of all air pressure acting on the wing is an upward load just about
equal to the entire weight of the airplane (it would be exactly equal if there were no air loads
acting on the fuselage or tail surfaces ). Instead of giving this value in pounds, the term load
factor is used. The load factor, is simply the ratio between the total airload on the wing and
the design gross weight of the airplane. Thus, when the wing is producing a "lift" equal to
twice the weight of the airplane, the load factor is 2. In the case of the Piper Special Trainer,
the design wing load factor is 6.16. This means that the airplane is designed to take a flight
load 6.15 times the weight of the airplane. Loads greater than this will cause the structures to
break. The maximum safe load factor for occasional application of loads is 4.1 ; loads greater
than this may cause permanent deformation of structural members.
Now to consider how such load factors might be obtained in actual flight, and what they mean
to the pilot. Let us assume that the load factor of 3 is the maximum we will achieve; this gives
us a slight margin of safety. A pilot flying level pulls back on the stick thus increasing the
angle of attack of the wing and producing additional wing lift which causes the airplane to
accelerate upward and follow a curved flight path. The acceleration depends on the amount
of lift of the wing. Since the wing is lifting 3 times the design gross weight of the airplane in
this accelerated flight condition, it is the same as saying the wing is loaded to a load factor of
3. We could just as well think of this load factor as representing the centripetal force required
to keep the airplane in this curved path. If you tie a heavy object to a string and swing it in an
arc, you will notice a stronger pull on the string than when the object was as at rest. This is
