Starting the 3
Thanks for the response. I get the impression it does not much matter. However, Mr. Pratt and Mr. Whitney went to a lot of trouble to fit the primer system (especially the original ‘spider’ type). ‘Prime’ means ‘first’ and the P&W Maint. Manual (1975) is specific, “It is essential that the mixture control remain in Idle Cut-off at all times when the engine is not firing.”
But perhaps, with the advent of electric boost pumps and a redesigned primer discharge into the compressor, things have moved on.
A modern day DC3 school instructs the reverse sequence:
LEFT ENGINE START
C FIRE GUARD.............................................POSTED
C LEFT ENGINE ...........................................CLEAR
C LEFT STARTER.....................................ENGAGE
C LEFT PROPELLER ......................... ........9 - 12 BLADES
C LEFT ENGINE MIXTURE...........................AUTO RICH
C LEFT ENGINE MAGS ...............................BOTH
C LEFT ENGINE THROTTLE.........................ADVANCE SLIGHTLY
C LEFT ENGINE PRIMER.............................AS REQUIRED
C LEFT ENGINE STARTER...........................OFF
Engine Start Sequence
Ensure that the boost pump for the respective
engine is in the ON position. Move and hold the
pre-oiler control ON, and the Starter Control Switch
to the desired position to engage the starter. Turn
the engine over three complete revolutions (9
“blades” - minimum). If the engine has been shut
down for more than four hours, the engine will be
turned over by the starter for at least four full
revolutions (12 “blades”) with the Ignition OFF prior
to start.
When ready for ignition, the Captain will bring the
appropriate mixture control lever out of idle cutoff,
place the magneto switch in the BOTH position,
and advance the throttle slightly.
Priming is not normally necessary. However, if the
engine is cold, the Captain will depress the primer
switch for 5 to 8 seconds after start to aid in engine
acceleration and repeat as necessary.
If the engine does not start within 3 to 5 seconds
select the primer for the appropriate engine. If the
engine does not start in the next 10 seconds, return
the mixture control to idle cutoff and continue
rotation with the starter. An exterior investigation
may be necessary to ascertain why the engine did
not start.
After first indication of engine start, keep the engine
turning with the starter until it can be determined
that the engine will continue to accelerate.
----------------------------------------
The prime first method takes finesse, practice and experience, not easily obtainable these days.
The second method is easy and seems to work ok for the weekend warrior.
What are the ‘nuts and bolts’ issues?
Flooding/backfire, fire – internal engine and on ground from prime drain, hydraulic lock?