How do planes land in low visibility?

Touching Down in the Blind: How Planes Land in Low Visibility

The roar of the engines fades as the plane begins its descent. For passengers, the anticipation is palpable, especially when the world outside the window is a swirling grey expanse of fog or a tempestuous curtain of rain. How, in such conditions, do pilots safely land their aircraft? The answer lies in a sophisticated technology known as the Instrument Landing System (ILS).

ILS isn’t some futuristic invention; it’s a tried-and-tested system that has been a cornerstone of aviation safety for decades. It allows pilots to land safely even when visibility is reduced to near-zero. This seemingly magical feat relies on a combination of precisely engineered radio signals and, in some cases, supplemental visual aids.

The system operates on a two-part principle. First, a localizer transmits radio signals along the runway’s centreline. This signal guides the aircraft horizontally, ensuring it stays aligned with the runway’s extended path. The pilot monitors the localizer signal on their instruments, a series of needles and indicators on the flight deck. A centred needle indicates the aircraft is perfectly aligned with the runway.

Secondly, a glide slope transmitter beams radio signals at a precise angle – typically 3 degrees – from the runway’s threshold. This signal provides vertical guidance, ensuring the plane descends at the correct angle for a safe landing. Again, the pilot uses instruments to monitor the glide slope signal; deviations from the ideal angle are clearly indicated.

These two signals, combined, create a “virtual runway” in the sky, guiding the aircraft towards the touchdown point even when the runway itself is invisible. The pilot constantly monitors these signals, making small adjustments to maintain the correct path and descent rate.

While radio signals form the backbone of the ILS, some airports enhance the system with high-intensity approach lighting systems (HIALS). These powerful lights extend along the runway’s approach path, providing visual cues even in dense fog or heavy precipitation. These lights act as a secondary confirmation of the aircraft’s alignment, offering a valuable visual reference for the pilot even when relying primarily on the radio signals.

It’s crucial to understand that ILS is not a completely automated system. The pilot remains in control throughout the landing process, making crucial decisions and adjustments based on the information provided by the instruments and, when available, visual cues. The system acts as a reliable guide, but the skill and experience of the pilot are essential for a successful low-visibility landing.

In conclusion, the seemingly impossible task of landing a plane in thick fog or a storm is achieved through the careful engineering of the ILS and the expertise of skilled pilots. This sophisticated system, along with supplemental lighting, ensures that air travel remains safe and efficient, even in challenging weather conditions.