Piper Dakota PA-28-236 Pilot Operating Handbook page 94

PIPER AIRCRAFT CORPORATION
PA-28-236, DAKOTA
Use of the mixture control in cruising flight reduces fuel consumption
significantly, especially at higher altitudes. The mixture should be leaned
during cruising operation above 5000 ft. altitude and at pilot's discretion at
lower altitudes when 75% power or less is being used. If any doubt exists as
to the amount of power being used, the mixture should be in the full RICH
position for all operations under 5000 feet.
To lean the mixture, disengage the lock and pull the mixture control
until the engine becomes rough, indicating that the lean mixture limit has
been reached in the leaner cylinders. Then enrich the mixture by pushing the
control towards the instrument panel until engine operation becomes smooth.
If the airplane is equipped with the optional exhaust gas temperature
(EGT) gauge, a more accurate means of leaning is available to the pilot. For
this procedure, refer to the "Avco-Lycoming Operator's Manual."
The continuous use of carburetor heat during cruising flight decreases
engine efficiency. Unless icing conditions in the carburetor are severe, do not
cruise with the heat on. Apply full carburetor heat slowly and only for a few
seconds at intervals determined by icing severity. Use of partial carburetor
heat is not recommended.
In order to keep the airplane in best lateral trim during cruise flight, the
fuel should be used alternately from each main tank. It is recommended that
one main tank be used for one hour after takeoff, the other main tank used
until nearly exhausted, then return to the first main tank.
Always remember that the electric fuel pump should be turned ON
before switching tanks, and should be left on for a short period thereafter.
To preclude making a hasty selection, and to provide continuity of flow, the
selector should be changed to another tank before fuel is exhausted from
the tank in use. The electric fuel pump should be normally OFF so that any
malfunction of the engine driven fuel pump is immediately apparent. If signs
of fuel starvation should occur at any time during flight, fuel exhaustion
should be suspected, at which time the fuel selector should be immediately
positioned to a full tank and the electric fuel pump switched to the ON
position. Fuel tank selection at low altitude is not recommended, since little
recovery time is available in the event of an error in tank selection. When
switching tanks, make sure that the selector drops into a detent and is lined
up with the desired tank.
ISSUED: JUNE 1, 1978
REVISED: NOVEMBER 20, 1981
SECTION 4
NORMAL PROCEDURES
REPORT: VB-910
4-21