Section III -- Curtiss Electric Propeller and Mag Check
- Pre-Flight Propeller and Mag Check. This check should be made prior to each flight to
determine that the propeller is functioning properly.
- Open the throttle (P-47 to 2000 RPM) (Allison 2300 RPM) with the propeller in full high
RPM selector switch and automatic.
- Using the selector switch, manually decrease the RPM 200 RPM. At this point release the
switch and observe the tachometer, which should hold steady at the new RPM. If it remains
constant that indicates that the brake is functioning properly. If it fluctuates, it
indicates a running or surging engine or a faulty tachometer. If the tachometer gradually
shows an increase it indicates that the propeller brake is slipping or is not functioning
properly. In that case the propeller is not safe for flight.
- Using the selector swich manually, increase the RPM to full high and observe that the
tachometer return to the original RPM.
- Check the magneto at this point with the selector switch in the OFF or FIXED PITCH
- Place the selector switch in the automatic position.
- Move the prop quadrant control slowly back to obtain a 200 RPM decrease. Observe the
tachometer to see if a steady RPM is held. This is a double check on the propeller brake
and the governor sensitivity. If a fluctuating tachometer is observed in the manual check
and a steady reading is observed in the automatic check, then the fluctuation was caused
by the surging of the engine. If the tachometer fluctuates in both checks, the tachometer
- Return the prop quadrant control to the full high RPM position and observe that the
tachometer returns to the original RPM.
- We are now ready for take-off if this check has been satisfactory, and that you know
your propeller is in automatic because your last check was made with the prop quadrant
control, which is operative only when the propeller selector switch is in automatic.
- Pre-Flight Check for Curtiss Prop with Coordinated Controls.
- With RPM at 1000 to 1200 put selector switch in OFF or FIXED PITCH position. Increase
throttle to 2300 RPM. Take normal mag check.
- Put selector switch in automatic, open throttle to 2300.
- Manually decrease RPM with selector switch 200 RPM.
- Selector switch to automatic to regain lost 200 RPM
- Selector switch to increase RPM to gain 100 RPM.
- Selector switch to automatic to lose 100 RPM.
You are now ready to take-off, but as a final check prior to starting the take-off run,
see that the selector switch is in automatic. Remember that in checking any electrical
propeller the last thing you do is check the propeller in automatic. If this procedure is
followed you have eliminated the greatest and most dangerous aspect of this propeller,
namely, taking off in fixed pitch.
- WITH COORDINATED CONTROLS (P-39Q-10 and Subsequent P-39s) Aero Products Propeller
- Since the prop and throttle controls are coordinated, a slightly different prop and mag
check must be made. The prop check is as follows:
- Move throttle from 20" Manifold Pressure to 37" Manifold Pressure and back to
original 20" setting.
- Prior to the first flight in the morning, this cycle (20 to 37 and back to 20) must be
repeated three (3) times to completly purge the prop hydraulic system of all air.
- Open throttle to 2300 RPM and make mag check. This magneto check must be made
principally by feel as the governor and prop operating mechanism will pick up a part of
the mag drop and extreme care must be used in checking this drop. The allowable drop with
these controls should not exceed 75 RPM. It is much better to make this mag check by feel
as a rough running engine on either mag is not safe for flight.