King Air Propeller Demonstration

With the cowls off, this video demonstrates how the prop levers and linkages work to command the governors to increase, decrease, or maintain propeller RPM as required by the pilot. Edit: I’ve added the following text to answer some common questions in the comments. ——————— What prop settings do you set during different stages of flight. In essence, regarding prop lever settings, the only pilot action during a “normal” flight in this type of aircraft is as follows: -Props full forward (fine pitch) for taxi and Take Off. See Note 1 below. -Adjust the props to “Maximum Continuous RPM, or Climb RPM shortly after take off. See Note 2 below. -Reduce Prop RPM for the cruise. See Note 3 Below -During the approach phase adjust your props to full forward for the landing (reverse thrust) or for the anticipated “go around”. See Note 4 Below. That’s it. The rest of the time, the governor works to achieve the RPM that the pilot has “asked for”/selected. So when there is excess power, it simply reduces the pitch of the blades to take a bigger “bite” of the air. Notes. Note 1: The props won’t achieve the High RPM you require, until you apply sufficient power using the power (thrust) levers to turn them fast enough. Once you have enough (and excessive) power, the governor will continuously adjust the propeller pitch to maintain the RPM you requested. Note 2: In the C90GTX, the difference between Maximum RPM (time limited) and Maximum Continuous RPM is very small. Just a fine tickle back of the prop levers. If the props are rigged correctly, this is a change of 1,926 RPM to 1,900 RPM. In other King Air models, the difference between Max RPM and Max Continuous is more of an adjustment. (300-400 RPM in the in the models I’ve flown) Note 3: Refer to the Cruise Tables in your Pilot Operating Handbook. In this particular model, you can leave the props at 1,900. We do however tend to adjust them to 1,800 for longer cruises, because it changes the “tone” of the props to a more comfortable one for passenger comfort. Note 4: Pilot technique differs here, based on the types of props you have fitted, runway available and passenger comfort. In the C90GTX, I always adjust the Props to full forward in the final approach phases of a flight. That way, the “Reverse Thrust” is ready on the ground and I simply have to put the power levers in reverse. Same with a go-around... it leaves me less things to do. In the B200 or other models of the 90 that I’ve flown, you could be adjusting the props from 1,600 to 2,200 RPM ready for the reverse or go around. This can have quite a noise increase for passengers. So, many pilot choose to leave the props where they are until after touchdown, when they will then whack prop levers full forward before applying reverse thrust. This of course, is runway length and other conditions permitting. ————————— Another common question is “why do you manually close the gen ties before start”. Lazy but most obvious answer: Because the C90GTX POH says so! Real explanation: the C90 GTX has a “triple fed” electric bus system. The flashing beacon light outside the aircraft, operates off the Left Bus. So until the left generator bus is online... the Beacon light won’t be on and flashing outside, regardless of the Beacon Light switch position. So you manually close the gen ties before start for that reason.