Flying through various kinds of weather can be stressful for some flyers. However, for many people, it is the landing that is the scariest. So, what if the weather at your destination is really bad? How do the pilots find the runway and land safely when there is weather or a storm? Anyone who has flown to San Francisco knows about delays due to fog. The same goes for people flying through cities like Chicago in the winter time when it comes to snow. Regardless of the type of weather, the scenario for landing is typically the same: As a passenger, you are looking out the window as the plane descends towards the runway. Because of the clouds, rain, or snow, you can’t see anything outside. The ground and sky are completely obscured. And then, ten to fifteen seconds before the plane touches down on the runway, you are finally able to see outside. At this point he plane is only a few hundred feet above the ground and it’s still can be difficult to see clearly! How do the pilots know where the runway is? It’s fairly easy to understand how pilots land planes in good weather. But how do they do it when conditions are less favorable? The short answer is: instruments (and we are not talking about guitars and trumpets).
Normally, pilots land airplanes by using visual references. Basically, they look outside, see the airport, and maneuver the plane by hand all the way down to the runway. However, when visibility is reduced due to clouds, rain, snow, or fog, the pilots must rely on their flight instruments in order to land. These primary flight instruments show various factors like airspeed, pitch, altitude, etc. Using all of these instruments simultaneously the pilots are able to determine their exact location at any point in time.
So how exactly, do the pilots figure out where that two-mile long piece of concrete called a runway is located? The secret is that pretty much all airports used by airlines have at least one runway with an Instrument Landing System (ILS). These systems have two radio transmitters located along-side the runway that emit signals that all airplanes can track. One transmitter emits an invisible beam that extends along the center of the runway for miles along the approach path. This signal provides horizontal guidance all the way to the end of the runway. At the same time, a separate transmitter emits a similar beam along the runway path up into the sky at approximately a 3 degree angle. This creates an artificial descent path for airplanes to use for vertical guidance. Both of these signals are received by the airplanes navigational systems. So, when they are combined, the radio signals create an artificial pathway that extends out from the approach-end of the runway. The pilots then use their flight instruments to follow these two horizontal and vertical paths down the center-line of the runway for a safe landing. Some airliners even have an Auto-Land system that enables the autopilot to land the plane in near zero visibility!
It should be noted that every airliner has three sets of flight instruments. There is one set for the captain, one for the first officer (co-pilot), and one back-up. And each pilot has their own set of controls in the cockpit so that either pilot can land the plane. So, even in bad weather, all airliners and the pilots who fly them are able to fly down to the runway and land safely every single time. While flying in weather with reduced visibility may not make for the best viewing from a passenger’s perspective, as an airline pilot I can tell you that using these instrument systems for navigation is 100% safe and reliable. You can rest easy knowing that even if you can’t see outside, the pilots are always able to tell exactly where the runway is located.
-How do pilots land the plane in bad weather?-