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“G” stands for “GAS.” Check the left and right fuel gauges for

adequate fuel onboard, verify that the fuel selector is on “both”

and the fuel shutoff is pushed all the way in. We’ll leave the aux-

iliary pump off for the moment.

“A” stand for “ATTITUDE.” For once, this doesn’t mean how you

feel, or if you intend to get in my face later on; it’s your cue to

check pitch attitude, or, in this case, to verify that you have the

pitch trim set properly for takeoff. If it were mis-set, you’d either

have to exert a mighty heave to get the airplane off the ground;

or you might find the airplane leaping into the air before it, or

you, were really ready to fly.

“R” stands for “RUNUP,” and since there are several steps to this,

we’ll take them one at a time:

• Hold the brakes, or set the parking brake. Now, gradually

increase the throttle until you reach 1800 rpm.

• What we’re going to do now is check the engine’s two com-

pletely independent ignition systems. Each cylinder has not

one, but two spark plugs, and they’re fired by separate mag-

netos (often simply called “mags”). What’s a magneto? It’s very

similar to the ignition system of a car, and even includes a dis-

tributor - but instead of having points and an external coil (or,

in modern cars, an electronic ignition system), the magneto

generates its sparks internally, using a rotating permanent mag-

net (hence the name). This makes it entirely independent of the

airplane’s electrical system - the mags, and the engine, will

continue to run even if the airplane system fails altogether. (In

fact, old-fashioned airplanes don’t even have electrical sys-

tems, which is why they have to be started by the

"Hemingway” method of swinging the prop by hand - as in

A Farewell to Arms

• Move down to the ignition switch. While watching the

tachometer, move the switch two “clicks” to the left, paradox-

ically labeled “R.” What you’ve just done is switched off one

of the engine’s two magnetos - in this case, the left one. The

engine should continue to run, but since it’s not quite as effi-

cient with only a single spark to ignite the fuel/air mixture in

the cylinders, its RPM should drop slightly (50 to 100 RPM).

• Now switch back to BOTH, verify that the RPM comes back

up to 1800, then switch only one click to the left, to “L.” Once

again, the RPM will drop slightly. What you want to see here

is (a) that the drop is no more than 150 RPM on either mag,

and (b) that the difference between the two mag drops is no

more than 50 RPM. Make sure you finish by switching back to

BOTH once again.

• The final runup item in Cessna’s checklist is to check the vac-

uum gauge in the green arc. You might also glance at the

annunciator panel to ensure that it’s dark.

Thoughts differ as to how to handle the auxiliary fuel pump

on injected Lycoming engines like this one. The fact that the

engine performed normally during runup indicates that the

engine-driven fuel pump is working properly, so we should be

able to count on it from here on. On Lycomings, however, you

can also run the aux pump with no adverse effects (unlike on

Continentals, the other major brand, in which running the aux

pump along with the engine-driven one will flood out the engine

and kill it). If the engine-driven pump should fail right after take-

off, the engine will quit, leaving you with a busy situation at low

altitude - so in Lyc-powered airplanes, my personal practice is to

verify during runup that the engine-driven pump is okay, then

switch on the aux pump just as a backup for takeoffs and landings.

“S” is for “SAFETY”! Seatbelts on, doors latched, objects

stored, etc.

Flight Instruction