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FLIGHT INSTRUCTOR'S MANUAL 203

With modern control surfaces it is easily possible to build up actual acceleration values of from 10 to 20 gravities in sharp pull-outs or equivalent maneuvers at the limiting speed. It is obviously impracticable to design commercial airplanes to withstand any such conditions. Therefore, again the necessity for the gentle handling of aircraft at or near limiting speed cannot be overemphasized.

GUST LOAD FACTORS

The load factor added by striking a gust or bump of given intensity is directly proportional to the speed of the airplane.  The design factors are based on the assumption that the aircraft will not be flown at speeds above the normal high speed of level flight in very rough air; therefore it is always advisable to reduce air speed in very rough weather.
 In this connection, it should be noted that sudden severe gusts encountered at high speeds may cause structural failures. Airplanes having a high wing loading are not as likely to be critical in this respect as airplanes with low wing loading but relatively high speeds.

AIRCRAFT WITH CRITICAL REARMOST "C. G." POSITION

There is a very definite relation between the relative location of the center of gravity and the center of lift of an airplane and its spinning characteristics. It is therefore necessary to check on the original characteristics of the ship before making any changes in stagger which would affect the position of the center of lift, or in equipment or loading, which would affect the center of gravity. This relationship of the two locations is very critical when the C. G. is too far to the rear, and will result in uncontrollable spins becoming not only possible, but very likely. A difference of a fraction of an inch in the rear C. G. position has been known to change the spinning characteristics of a ship entirely.
 For this reason the probable results of all such changes should be thoroughly investigated before they are made.
 Some ships are so designed that with light gas loads, an extremely heavy person in the rear and a very light instructor or no one in the front, may cause the rearmost C. G. limit to be exceeded.
 In such cases the heavy person or student  should occupy the front seat, or an accurate determination of the extent C. G. position made, before spin practice is allowed. If either is impossible, another ship should be used.

150310 [[degree symbol]]-39-14

Transcription Notes:
I did not know how to do the degree symbol, so just noted it in brackets.