How To - Taxi Management

[Eddie]

Power Considerations

The F406 engines are free turbines, this means that the turbine itself is not directly connected to the propeller shaft as would be the case in direct drive engines.

From the perspective of the pilot, this is noticeable as a slight delay or lag between power changes and the aircraft accelerating/decelerating. During taxi, anticipation is required with power changes to prevent the aircraft from coming to a standstill if braking.

This is most noticeable when slowing down and initiating a 90 degree turn or greater, the effect of braking plus turning will stop the aircraft halfway through the turn if power is not added with anticipation. It is recommended that power is applied before commencing the turn so the engine speeds up, and in turn accelerates the propeller as the turn commences to counteract the increase in drag.

 

Steering

Nosewheel steering is controlled by the rudder pedals, which in turn can deflect the nosewheel up to 15 degrees left or right by deflection of a bungee spring and cables. The nosewheel can further deflect up to 50 degrees by using differential braking.

This is very different from airliners which have nosewheel steering up to 70 or more degrees.

The pilot of the F406 will have to consider the following:

• The bungee spring assembly can only turn the nosewheel if the aircraft is moving and the rate at which it rotates depends on the speed. The slower the speed the longer it will take for the nosewheel to reach the commanded deflection.
• Start your turn early and use braking and/or differential braking if necessary.
• Differential power will also assist in turning, especially to achieve the smallest radius of turn.

Power adjustments

Power settings for the F406 are achieved by a combination of torque and RPM. The amount of torque delivered by the engine depends on the position of the power levers and the atmospheric conditions. As the aircraft climbs into less dense air, for the same power lever position, the engines will deliver less torque. It is important to monitor this and periodically adjust the power levers to obtain the desired torque setting.

 

Fuel control lever

This is a control that looks just like a mixture lever, it has the same shape and colour, but the functionality is very different. In the F406 the fuel control lever acts as an on or off valve for admitting fuel into the engine.

Despite being a lever (rather than a switch), it does not have intermediate positions like a mixture lever, you can not “lean” the engine as you climb.  As far as the pilot is concerned, this is an ON or OFF control.