A night flight can pose its own sets of challenges, which are quite different from a day flight.

Because our human senses are adapted for ground use, sensory input during a night flight may not accurately reflect the movement of the aircraft. This inaccurate reflection can cause something known as a sensory illusion.

Ever wondered why getting your Diploma of Aviation (Instrument Rating) is so crucial? Over 90 percent of a take-off at night, is all based on reading instruments! Here we cover three critical sensory illusions which pilots may experience during a night flight.

Black-hole approach illusion

A black-hole illusion, occurs during the final approach of a night flight over unlit terrain, to a lightened runway, in which the horizon is not visible. With nothing to see between the aircraft and the runway, the pilot’s visual is a “black-hole”.

This is where instrument ratings play a crucial role. Relying on a solely visual approach can lead to the pilot experiencing a lack of peripheral visual cues, especially below the aircraft, known as glide path overestimation (GPO). GPO causes pilots to initiate an aggressive descent and wrongly adjust to an unsafe glide path.

Autokinetic illusion

If you’ve ever been stuck in traffic, staring down the barrel of stationary cars ahead of you, you may have noticed the car next to you moving, only to turn your head and realise it has been stationary the whole time. Autokinetic illusion is similar to this; however, occurs at night or in poor visual conditions. This illusion gives pilots the impression that a stationary object is moving in front of the airplane’s path and occurs by staring at a fixed point of light, such as ground light or stars, in a dark background.

Autokinetic illusion occurs when small eye movements in poor visual conditions, such as during night flying, are interpreted by the brain incorrectly, giving the impression of movement of the object being viewed.

Somatogravic illusion

These are a group of three various illusions caused by linear accelerations. The inversion illusion is caused when abrupt change from climb to straight-and-level flight stimulates the otolith organs in the body, creating an illusion of tumbling backwards. As a response to this illusion, pilots may push the aircraft into a nose-low altitude intensifying the illusion.

The head-up illusion involves a sudden forward linear acceleration during a level flight. In this situation, the pilot perceives that the nose of the aircraft is pitching up and as a result would push the yoke or the stick forward to pitch the nose of the aircraft down. During a night flight, from a well-lit airport into a dark sky the chance of the head-up illusion occurring is significantly increased, increasing the danger for a crash.

The head-down illusion is the opposite of the head-up illusion and occurs when a sudden linear deceleration occurs such as air braking or lowering of the flaps, during level flight. In this instance, pilots perceive the illusion that the nose of the aircraft is pitching down. Pilots will respond by pitching the nose of the aircraft up, causing the aircraft to stall if occurring during a low-speed final approach.

These illusions can can be extremely dangerous for pilots, emphasising just how critical an instrument rating is when it comes to flying. If taking to the skies and flying at night excites you, why not completeThe Diploma of Aviation (Commercial Pilot Licence – Aeroplane) or the Diploma of Aviation (Instrument Rating)!