Taxi – basic ground operations. Lesson 2

Taxiing. A simple affair, especially for someone who has used the simulator before. But you still ask so the description will be thorough.

I look back to my beginnings – turning on the ground was not entirely obvious, even when I was confident in the air. My excuse is that Chuck Yeager’s Air Combat and Strike Commander in the early 90s did not encourage trips around the airport. But even now virtual pilots often open their simulator with the plane on the runway and don’t bother driving around.

Today you will learn how to move the plane around the airport

The purpose of this lesson is to explain:

  • how to steer an airplane on the ground
  • how to move and maintain a constant speed
  • how to brake
  • how to turn using the front wheel and brakes

Learn how to move the plane around the airport

This lesson explains:

  • ground steering
  • moving and maintaining speed
  • braking
  • turning (nose wheel steering and differential braking)

How do planes move on the ground?

I struggled (and still do on airplanes I’m not used to) with three scenarios:

  • moving from a stop
  • taxiing with a set speed,
  • maintaining low speed in turns without stopping.

I solve these problems today. But let’s start with the basics.

Thrust pushes the plane on the ground and in the air. To move forward, increase the power by opening the throttle. Simple? Well, I’ll complicate it a bit. The force needed to move a stopped plane is greater than the force needed to keep speed on a level surface.

cockpit-eng.jpg

To move, increase power, remembering there is a lag between throttle inputs and plane’s reaction. Increase power gradually until the plane begins to roll. Then reduce it to keep the designed speed. Be precise when reducing power – too much and your plane will stop.

Taxiing – at 20 knots (10 in turns)

Typically, when taxiing in a straight line plane maintain a speed of 10-20 knots. In turns 10 or less. These values are approximate – Boeing 747 goes over the long and straight at speeds of 20, 25 or even 30 knots. Speed depends on the weight of the aircraft – the higher the slower. The surface, conditions and the width of the taxiway change the speed. In the case of Cessna 172 and other small planes, a good idea to keep 10-15 or 20 knots and 5-10 in turns. On narrow taxiways – less. One pilot mentioned that he prefers “jogging speed” for light planes, but it depends on the circumstances (do not taxi at 5 knots on a wide taxiway at an international airport). Engine RPM during taxiing oscillate around 1000.

If the speed increases excessively, reduce power and use brakes. Sometimes braking during taxiing will be unavoidable. In this case, use the brakes regularly and reduce the speed by several knots to keep the speed in a safe range.

Airspeed indicators on small airplanes lack low-speed readings. Use the GPS that displays Ground Speed instead.

More power in turns

Turns, specifically at 90 degrees or more, require more power to overcome the greater resistance. Increase power slightly (!) before turning.

Simulator complicates braking

In general, the brakes are connected to the rudder pedals on the plane (you press toe-brakes and push the whole pedal to steer). To brake, press both. Use right or left pedal to brake one wheel – this is “differential braking”.

In the simulator, the situation gets complicated if the pedals are missing. You can brake at the same time with both brakes (keyboard shortcut is a dot.) or use differential braking (+/- on the numeric keypad). The buttons responsible for the brakes should be pulsed rather than held.

rudder---eng.jpg

If you use the keyboard or if you assigned brakes to a joystick – press the button repeatedly, at a fast rate. To reduce braking efficiency – reduce the rate. In the previous lesson, I suggested assigning a brake to the joystick’s trigger – that makes it easier to brake.

Avoid holding down the button – locking the brakes may cause slipping and increases the wear of the brakes or tires. You will notice the operational nuances in airplanes such as the suggested Cessna A2A. Slip can occur in any aircraft in the simulator.

If you have pedals – press softly. Brakes on the pedals are assigned as an axis and proportionally to the pressure. You may find it difficult to press both equally, but with training, you will get more precise.

Turning – nose wheel steering or differential braking

Airplanes turn in two ways – with nose wheel steering differential braking.

Nose wheel steering

The turning mechanics are similar car’s – pilot just turns the front wheel. In the cockpit it differs from the car – the nose wheel control connects to rudder pedals, so the turn the nose wheel pilot moves the appropriate pedal forward. Larger planes (e.g. Boeing 737) have a separate device (tiller) for this.

Nose wheel steering should be sufficient in most cases. If you need to reduce the turn radius, use differential braking.

Differential braking

This is how airplanes not equipped with a steerable nose wheel (for example Beech 60 Duke) steer on the ground. It can also help on planes with a nose wheel steering in narrow spots.

Light braking of the inner wheel tightens the turn. However, be careful not to block the wheel, because it increases tire wear (again – in A2A aircraft this will be simulated).

rudder---eng.jpg brake.jpg p3d-7.jpg

Brakes and the joystick – ambush and hidden features

Besides the keyboard, brake control is available by linking joystick’s rotation and brakes. It’s an interesting feature, but also a trap.

You can use right or left brakes with a joystick. The trigger activates brakes and vertical axis activates the brake when the joystick is turned. It’s an advantage. Where’s the ambush?

The described function may hamper braking. Directional control during braking will cause differential braking, which results in a sudden change of direction. Remember this to avoid surprises.

Slew – move a badly positioned plane

How to move a badly positioned airplane? For example when taxiing out of a position is impossible? A plane sits in front of the hangar. Slew mode is the answer. Press Y and control the plane using the arrow keys on the keyboard and the joystick. There is complete freedom of movement – forward, backward, sideways, etc. Rotating the joystick will rotate the plane. Use this if you need to reposition your plane. It’s a little cheat, but it’s useful and circumvents the lack of precise towing methods.

Exercises

Any airport with over one taxiway is sufficient for these exercises. I took my pictures in Heringsdorf – freeware scenery.

Preparation

Run the simulator and set the flight:

  • aircraft – Cessna 172
  • airport – Heringsdorf (EDAH)
  • location at the airport – active runway
  • weather – fair weather
  • time – day

After loading the simulation set the parking brake (Ctrl +. [Dot]) and auto-start the engine (Ctrl + E). On A2A plane, use Shift-3 panel auto-start option.

Exercise 1 – taxi on the runway

p3d-1.jpg

Practice speed and directional control.

Release the parking brake, increase power and stabilize speed at 15 knots while driving along the centerline. Use joystick (vertical axis) or pedals (if you have them) to correct direction. Stop several times and move again, to feel the power needed to roll and to keep the speed of 15 knots. Try to change the speed – keep 10 knots for some time.

Evaluation criteria:

  • maintain speed with 3-4 knots accuracy for 20-30 seconds,
  • do not exceed 20 knots,
  • no unintended stops,
  • stick to the centerline.

Exercise 2 – turning

route.jpg

It will help you control the turns.

When finishing exercise 1, vacate the runway (turn into a taxiway) at 5-knot speed (5-10 will be ok). Then another turn, and another and back to the runway. If you have doubts about where to go – stop the plane and open the top-down view (right-click anywhere on the screen and select Outside -> Top Down from the menu.) Return to the cockpit using the same method (Cockpit -> Cockpit).

Try to use only the nose wheel steering for turns. Look around before turning. Use HAT to turn your head in the simulator.

Evaluation criteria:

  • maintain the speed of 15 knots with a 3-4 knot accuracy,
  • do not exceed 20 knots,
  • do not exceed 10 knots in turns,
  • do not stop in turns
  • follow taxiway line.

Exercise 3 – U-Turns

turn.jpg

Master tight turns.

Move slowly (5-10 knots) to the edge of the runway. Use differential brakes (gently) to turn (+ / – [plus and minus on the numeric keypad] – plus left, minus right) to decrease the turning radius. While turning – keep your nose wheel turned.

Do a few turns and compare their radius and the use of brakes.

If you need more power to keep 5 knots – open throttle slightly (!).

Evaluation criteria:

  • do not exceed 10 knots,
  • do not stop.

How long should you exercise?

Do exercises twice.

Donate