back to "BOTH" position to clear the other set of plugs. Then move
switch to "L" position and note RPM. The difference between the two
magnetos operated individually should not be more than 75 RPM. If
there is a doubt concerning the operation of the ignition system, RPM
checks at higher engine speeds will usually confirm whether a deficiency
exists.
An absence of RPM drop may be an indication of faulty grounding of
one side of the ignition system or should be cause for suspicion that the
magneto timing is set in advance of the setting specified.
TAKE-OFF.
POWER CHECKS.
It is important to check full-throttle engine operation early in the take-
off run. Any signs of rough engine operation or sluggish engine accelera-
tion is good cause for discontinuing the take-off. If this occurs, you are
justified in making a thorough full-throttle, static runup before another
take-off is attempted. The engine should run smoothly and turn approx-
imately 2375 to 2475 RPM with carburetor heat off.
Full throttle runups over loose gravel are especially harmful to pro-
peller tips. When take-offs must be made over a gravel surface, it is
very important that the throttle be advanced slowly. This allows the air-
plane to start rolling before high RPM is developed, and the gravel will
be blown back of the propeller rather than pulled into it. When unavoid-
able small dents appear in the propeller blades, they should be immediate-
ly corrected as described in Section IV.
Prior to take-off from fields above 5000 feet elevation, the mixture
should be leaned to give maximum RPM in a full-throttle, static runup.
FLAP SETTINGS.
Normal and obstacle clearance take-offs are performed with flaps up.
The use of 10° flaps will shorten the ground run approximately 10%, but
this advantage is lost in the climb to a 50-foot obstacle. Therefore the
use of 10° flap is reserved for minimum ground runs or for take-off
from soft or rough fields with no obstacles ahead.
If 10° of flaps are used in ground runs, it is preferable to leave them
2-8
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