Are You Properly Seated?

Regulations require that the aircraft manufacturer provides a means which will aid the pilots to position themselves with precision and allowing them to have the best point of view from their seat. This is defined by the EASA CS 25.773 and FAA FAR 25.773.

A pilot who is between 1.58 m (5ft 2 inches) to 1·91 m (6ft 3 inches) tall shall have easy access to all of the aircraft’s controls in the cockpit and this is stipulated by EASA CS 25.777. This requirement ensures that the design fits to the vast majority of pilots.

These requirements are taken into account when a reference point is provided for the design of any cockpit. It is often referred to as the design eye position and also called eye reference point.

Modern aircraft cockpits are built around the eye reference point. It is used to size the cockpit windows and define the location of all the controls, displays and instruments.

When the pilots align themselves with the eye reference point, they will have adopted the optimum position to operate the aircraft.

The cockpit is designed so that when the pilot has aligned themselves to the eye reference point; all of the instruments and displays on the front panel are in their field of view (fig.1).

(fig.1) Eye reference point principle

A pilot needs to have good situational awareness during a flight. Alignment using the eye reference point enables the pilots to have an optimal field of view through the cockpit’s windows to see what is around them outside the aircraft. The eye reference point position ensures the pilot can maintain the best cut-off angle that will provide the longest visual segment (fig.2). This is especially important to get visual references during Low Visibility Operations (LVO).

Having a consistent viewpoint gives several operational advantages such as easing the handling of the aircraft by providing pilots with a consistent visual reference, repeatable at every flight. This is especially useful during final approach to be familiarized with the final approach path angle and also for the flare phase.

Since the A300 Airbus has provided an eye reference indicator on the centre structure of the windshield in all Airbus aircraft (fig.3). It enables flight crew to adjust their seat position so that their eyes position matches the eye reference point. The indicator is a device that is fitted with 3 balls painted red or white. To achieve a correct seating position, pilots must align the red and white ball meaning that the white ball is hidden when in the correct position.

Using Head Up Display (HUD)

HUD symbols are fully visible when the pilot’s eyes are closest to the eye reference point. An “eye box” is defined as an area around the eye reference point that gives a position tolerance range (fig.4). Hence the pilot correctly sees indications on the HUD when their eyes are positioned inside this virtual box. The HUD eye box area extends further aft than forward to allow HUD readability when seated in a more reclined position for comfort.

A pilot properly seated with their seat harness fastened is able to reach and operate all of the aircraft’s controls through their full range of motion or deflection as it is defined by the design certification requirements (fig.5).

A pilot seated in a position that is too low may have difficulties to reach all of the system controls located on overhead panel.

On ground, if seated too low while taxiing the aircraft, the pilots’ situational awareness can be impaired to an extent where it may increase the risk of collision with airbridges, buildings, ground support vehicles or other aircraft on the ramp.

In flight, if pilots position themselves too low, during final approach their perception of the flight path angle may be inaccurate.

Being seated too low can also create a blind area due to the glareshield, reducing the cut-off angle and thus limiting the visual segment (fig.6) & (fig.7). Such reduced visual segment during approaches with poor visibility conditions, including Low Visibility Operations (LVO), impairs the ability of the flight crew to obtain the proper visual references for landing, increasing the likelihood of a go-around.

The flight crew must adjust their seating position before the aircraft moves, typically before the pushback or engine start according to the FCOM SOP.

How does a pilot adjust their seat to position themselves correctly?

Step 1: Adjust the seat longitudinal and vertical position to align your eye-level with the eye reference indicator and also check that the glareshield does not obstruct the view the upper PFD and ND (fig.9).

Step 2: Adjust the armrest to a position where your hand can grip the sidestick naturally without stretching the forearm and with a straight wrist. If the armrest is correctly adjusted, your forearm should rest comfortably on the armrest and you will only need to move your hand and fingers to give the appropriate inputs to the sidestick (fig.10).

Step 3: Adjust the pedals position using the adjustment lever. Ensure the pedals can be moved through their full range of motion with your feet they can be fully deflected and that full manual braking can be applied.

Take a note of the positions of both the armrest and pedals on their associated position indicators when your adjustment settings are correct and comfortable to save time when making seat adjustments for your next flights (fig.11).