Page 21 - July 2023

be aggressive first, then play with the Beta range only when at 40 KIAS or below. Remember that the POH states that Reverse should not be used below 40 KIAS. I suggest that you begin slowly moving the power levers forward from the all-the- way back position when you see 60 KIAS, and make sure that they are at Ground Fine or at the bottom of Beta by the time you see 40. Don’t make the common mistake of thinking you need to be over the Idle Gate by 40 KIAS. No, staying in Beta is the proper procedure, but just make sure you are out of Reverse, back into the dead band Beta, area.
To conclude, let’s see how we can evaluate our Beta and Reverse rigging, from a pilot’s standpoint. The first thing to do is to make sure that your Low Pitch Stop (LPS) begins its travel back into Beta at the proper blade angle. Since it is almost impossible to find a mechanic who will use a protractor on a blade while it is spinning, angle is verified not by an actual angle measurement, but rather by a “Flight Idle Torque” setting. A graph exists in Chapter 76 of the maintenance manual that shows what this torque should be and at what RPM, for any given altitude and OAT. Realize that the value is not the same for most retrofit props, as it is for the standard propeller options. I’ll make it easy for you. The chart (above right) provides most of the values for different King Air models and different propellers, at Sea Level on a Standard (15°C) day.
In a clean run-up area, aim into the wind, make sure the propeller levers are fully forward, then add power until you reach the specified propeller speed. Record both left and right torque values, as well as OAT and Pressure Altitude (29.92 in Hg), and pass them on to your maintenance folks. (If the wind is really howling that day, take both an upwind and downwind reading so that they may be averaged out.)
While still in the run-up area, select High Idle on the condition levers and bring the power levers to Idle. Next, move either power lever
JULY 2023
MODEL
All 3-Blade 90- & 100-Series
C90B (4-Blade)
C90GT
4-Blade McCauley, 90-Series 4-Blade Raisbeck 90- & 100-Series
4-Blade Raisbeck (Magicam) F90 and F90-1, Standard Prop (GLPS)
A100
3-Blade Hartzell, 200-Series 3-Blade McCauley, 200-Series 4-Blade McCauley, 200-Series
4-Blade Hartzell-Raytheon, B200 4-Blade Hartzell-Raisbeck, 200- Series
MODEL
300 (FLPS) 350 (FLPS)
back over the Idle gate – even over the Ground Fine gate, if need be – while watching the propeller speed. As the blade flattens, giving less rotational resistance, the RPM should rise. As the blade angle goes negative, the extra rotational resistance will cause the RPM to fall. Experiment until you find exactly the flattest pitch position and make a mark on the power quadrant where the aft edge of the power lever shaft is now located. (Putting some masking tape next to the slot makes this task easier and less messy.)
Now do the same with the other power lever – find where the RPM is the highest and mark it appropriately. Are both sides close together? I hope so, but the marks will tell the story
TEST TORQUE SPEED VALUE (RPM) (ft-lbs)
2,000 600±40 2,000 605±40 1,800 545±40 2,000 580±40 1,800 505±40 1,800 805±40
1,800 360±40 2,000 440±40 1,800 800±40 1,800 750±40 1,800 660±40 1,800 520±40
1,800 635±40
TEST TORQUE SPEED VALUE (RPM) (Percent)
1,500 42 ± 2% 1,500 36 ± 2%
to your mechanic. Next, while the power levers are still at the flat pitch position, retard the condition levers back to Low Idle. If both left and right N1 speeds do indeed fall back to Low Idle, that’s great! It confirms that your dead band is large enough to kill your residual taxi thrust without adding power.
However, if one or both N1 speeds hang up at something between Low and High Idle, then your dead band is too narrow and your props are candidates for sandblasting ... not good. I have even discovered rigging so out-of-spec that the N1 started to exceed High Idle before we found that flat pitch, peak RPM position. Yuck! This dead band is much too small!
KING AIR MAGAZINE • 19