If you push those rudder pedals to taxi on and off the runway, and for little else, then perhaps you’re a fighter jet pilot. But if you’re flying a single engine aircraft with a propeller, then you might want to use them in other phases of flight too (and actually, this is especially important if you fly a multi engine aircraft!).
Chances are that your propeller rotates in a clockwise direction when viewed from the cockpit (if it spins the other way, then this article will confuse you – read it in a mirror!). Before opening the throttle on the runway, just have a little think about possible rudder use. Anticipation helps. Ensure the rudder trim is set correctly, if your aircraft is fitted with it. Lets have a think about some of the yawing forces on a typical configuration aircraft;
- Look at the windsock. Any crosswind will push the vertical tail surfaces, and your nose will tend to point into the wind.
- Slipstream from the prop will spiral around the fuselage and strike the tailplane, yawing you to the left.
- Advancing prop effect (generally in a Tailwheel type) means the downward moving blade creates more lift than the upward moving blade, yawing you left.
- Lowering the nose on takeoff (in a Tailwheel aircraft), will encourage gyroscopic precession and will also yaw you to the left.
- The torque of the propellor will attempt to rotate the aircraft to the left, but your wheels in contact with the runway will resist this. But the extra force and weight and drag on your left wheel will yaw the aircraft left too. Right aileron is a great tool for minimising this force. But you’ll need some right rudder too.
Like I said, anticipation helps, but look out the front and squeeze or push as much rudder that’s needed to keep pointing down the runway centreline.
Once you’ve lifted off- you can forget about the rudder until you touchdown. Actually that’s not true… read on.
Your aircraft is generally designed with a little right tailplane incidence to allow you to fly ‘feet off’ at the cruising speed and power. That makes long Nav trips easier on your thigh and calf muscles. Unfortunately at high climb power and a slower climb speed, you will need to balance the aircraft with right rudder. Don’t just look at the ball, but ensure your wings are level too. Keep that right rudder in, or else you will climb to the left.
If the weather conditions are smooth and you decide to descend faster than your cruise speed, that inbuilt right incidence will take effect, and will start yawing you to the right. Hence you’ll probably need left rudder to keep straight…
What about turning? Depending on your aircraft type, you may not need to add much rudder when rolling into or out of the turn. But if you are rapidly rolling, or pulling into a steep turn, then the issue is more noticeable. Remember Adverse Aileron Yaw? When you apply aileron and the Up Going wing develops more Lift than the Down going wing? The increased Lift also comes at a cost of increased Drag? And that Drag actually yaws the nose the wrong way, opposite to the roll? And you spill your coffee everywhere?
The answer is RUDDER.
Landing? Align that nose with the centreline. Use enough aileron to fight the crosswind, then use rudder to track down the centreline during the flare.
Going around? It’s likely you will use high power at slow speed- so keep straight with those footrests.
Whilst I won’t go into it now because it is incredibly complex, Rudder is a life saving control surface when it comes to flying multi engine aircraft during engine failures. During my experience flying jet engine tankers, we needed to train extensively on asymmetric flight conditions – including double assymetrics (when two engines on the same side fail!)
We use the rudder to ‘keep the aircraft straight’ and actually allow the aircraft to sideslip through the air in order to maintain control, slightly raising the dead engines (5 degrees or so) to reduce drag and improve performance. In some aircraft the rudder pressure force (even with rudder hydraulic boost) can be above 50kg – talk about a leg workout!
And actually, fighter pilots do use rudder in their jets sometimes, especially during crosswind landings and flat scissor manoeuvres in air combat. So please accept my apologies for the generalisation in my first paragraph. Check Six!