Moving onto my next flying challenge, moving from a fixed landing gear and a fixed pitch propeller to a complex airplane, equipped with a retractable landing gear and constant-speed pitch propeller (aka. variable pitch propeller). The propeller automatically changes its blade pitch (fine/coarse) to maintain a chosen rotational speed.
It varies the pitch to accommodate the different flight phases. A finer propeller pitch for take off and coarser for cruise. The aim is to maximize efficiency and performance through all phases of flight, more on this later.
For the complex endorsement, I have started with a 1975 Cessna Cardinal 177RG (C177RG), apart from being considered a complex airplane, it also has additional horsepower and some extra weight. I am writing the following as the highlights from fight instructor classes I have undertaken, and especially a lot of pattern circuit work (touch & goes) to perfect landing the Cardinal, including many crosswind landings.
Constant-speed pitch propeller (aka. variable pitch propeller)
The first thing you notice is that the there are three knobs, usually : throttle (black lever), propeller (blue knob) or mixture (red knob), the blue knob is sometime is black, but positioned in the centre between the throttle lever and mixture knobs. Both the propeller and mixture knobs are turning knobs for precision.
Throttle (black lever) - for manifold pressure (MP)
Propeller (blue knob) - for RPM
Mixture (red knob) - for fuel mixture
For take off the throttle and propeller knobs should be in the full forward position, and the mixture should also be in full forward position or set for best power (consult POH).
During taxi, use the throttle lever (black) as in a fixed pitch propeller plane, and keep the propeller and mixture knobs in the full forward position. This is also the recommended configuration for takeoff, approach and landing.
During flight (cruise), RPM and MP should be set as required (15-25 MP 2100-2500 RPM),
remember the the propeller should be set to FINE (forward) for take off and climbing, and COARSE (back) during cruise. Any major changes for climbing or descending should be handled as follows:
Increase power (climbing): First: Rev UP
First, the propeller knob to raise the RPM (revs), fine.
Second, the throttle lever to raise the MP
Reduce power (descending): First: Throttle BACK
First, the throttle lever to decrease the MP
Second, the propeller knob to decrease the RPM (revs), coarse.
Rev UP, Throttle BACK.
If you want to climb, you don't want to increase power with the propeller fully coarse, so you put the propeller RPM (revs) to fine, then increase throttle. 'Rev UP' first= move the RPM (revs) knob first to speed up / increase power.
If you want to descend /slow down, then reduce the throttle first, then adjust the propeller RPM (revs). 'Throttle BACK' first = move the throttle lever first to slow down / reduce power.
Starting the Engine When starting the engine, I have not yet experienced any issues with a cold engine start. First, I prime the engine with the fuel pump. I begin with the master on and throttle in 1/4 inch (1/2 if flooded), propeller set to high RPM (pushed inward), fuel pump on and mixture full rich. The fuel flow gauge should show up to 4 - 6 gallons per hour (GPH) in roughly 6 seconds. Fuel pump off and cut-off the mixture. The engine is now primed, the above should be omitted if the engine is warm.
Turn the key in the starter to crank the engine, and as soon as the engine fires, slowly move the mixture to full rich and adjust the throttle to 1000 RPM, and check oil pressure in green within 30 seconds.
TIP: Don’t crank the engine for more than 10 seconds, as the starter heats up and needs to rest before trying again. Each time the engine is cranked; the engine requires more fuel, and the engine may need to be primed again using the fuel pump, always confirming their is sufficient pressure on the fuel flow gauge.
TIP: Never increase manifold pressure (throttle forward), without increasing fuel flow with mixture. You could go from low RPM and medium throttle with mixture lean and work well, but to full throttle and a low RPM causes risk of detonation.
As with all airplanes, it is import to know its limits and especially related to airspeeds. This model Cardinal has its airspeed indicator (ASI) in miles per hour (MPH) opposed to knots (KIAS). I have included a table with the comparison of MPH and KIAS airspeed limits. I keep in mind that I rotate at 65 MPH and landing approach speed for landing at 80 MPH.
Circuit & Landing
Every plane is different, and there is no exception with the Cardinal, the landings are handled differently to its little brother the Cessna 172. The circuit speed also needs to be considered, as the extra horsepower really gets you moving on the downwind leg.
I find it important to start controlling the speed as soon as you turn into downwind (after climbing), moving the throttle (black) lever back until the manifold pressure (MP) reads 21 and slowly rotating the propeller (blue) knob back to 2,300 revolutions per minute (RPM), aiming at 115 MPH, and trimming to 95 MPH at about halfway along the downwind leg seems to work fine for me.
Once in beam with the runway numbers, I start to prepare and configure the plane for landing. First, landing light on, put in 10 degrees of flaps, and move the engine controls to full rich and full RPM. I continue by lowering the landing gear at no higher than 95 MPH. With the confirmation of the green landing gear light I know I am right to go. As the speed stabilizes, I start to turn and descend on base and trim to 80 MPH. On turning on final, I double-check the landing configuration, the landing light, landing gear in green, flaps, full rich, and full RPM (and landing gear again). The full forward propeller RPM is suggested in the event of a go-around.
On landing I find the Cardinal fun, as it is different to both the Piper Warrior and Cessna 172, apart from the retractable landing gear, it is more sensitive on the controls (I assume because of the its huge stabilator).
Once on final, I aim at 80 MPH, and basically glide the Cardinal to the runway, maintaining the correct height from the ground, I may need to throttle a little on a windy day, and never allow the speed to get below 80 MPH.
Once over the runway, I hold its position and allow the plane to settle on the runway, if I balloon during the flare I never push forward on the controls, I just hold it and allow the plane to land. If needed I give a little back pressure on the controls. In case of ballooning too high, and the rate of decent continues to be high, I throttle a little to cushion the landing. Once on the runway, avoid being aggressive on the brakes, avoid them and allow the Cardinal to slow down before using the brakes.
TIP: The doors on the Cardinal are huge, so it is important to keep this in mind on windy days. Be very careful opening the doors as they do not have struts to limit their forward opening motion, and the force generated by wind can certainly damage the door hinges. It is important to avoid any unnecessary repairs.
Many thanks to Airpull Aviation Academy