I love flying when the weather is gorgeous. These days when the weather is "clear and a million" - takeoffs and landings are relatively stress-free. But, we all know we have low clouds, rain, and fog either locally or at our destination. This is where an instrument rating comes in. First of all, all airline pilots have instrument ratings and highly capable aircraft that can get you in and out of most anything nature has to offer with just a few exceptions. Of course, nasty weather can slow down entire flying process resulting in delays.
What about people like me who spend a good bit of time flying much smaller aircraft? Believe it or not, we handle reduced visibility and low cloud ceilings the same way the pilots flying the "Big Iron" do it. Let me take you through an ILS or Instrument Landing System approach. This is the most precision of instrument approaches. It's the same system a 777 pilot flying for your favorite airline uses. It's the same system I use in my personal Piper Archer.
If you're aviation enthusiast, you may have noticed some antennas around the airport - especially larger airports. This antenna array located near the threshold of a runway is called a Localizer Antenna.
It transmits a radio signal that keeps the aircraft aligned with the extended centerline of the runway miles away from the airport. There's another antenna that is part of the ILS system called a Glideslope. This vertical antenna is mounted to the side and near the midpoint of the runway.
The glideslope antenna transmits vertical guidance to the airplane and keeps the airplane descending on the proper angle (usually 3 degrees) down about 200ft above the runway threshold. There are specialized ILS approaches that can get you all the way to the runway.
I'll give you an example of when an ILS approach would come in handy. Let's say you're flying above the clouds, but need to get down to the airport and the clouds are very low. Of course, you will not be able to see the airport and it might be a bit before the runway comes into view.
As you descend down toward the airport, the visibility goes away. It's pretty useless as you can see to look out the window. At this point, you are truly depending on instruments to keep the airplane under control. This is the view outside as you drop into the cloud cover.
Once you're established on the ILS approach and doing it right. This is what your instrument will look like in the cockpit. The vertical line is showing your deviation from the centerline of the runway and the horizontal line shows the deviation above or below the glideslope. The idea is to keep both needles centered in the "donut." as you fly the approach. If the needle moves left - you fly left. If the needle moves low - you fly low. You get the idea, right? In many modern aircraft, the autopilot can handle the approach almost all the way down to the runway. The instrument below is showing me lined up and on glideslope with Runway 36L at Huntsville International.
You can watch the approach and landing below. I broke out about 800ft above the ground with the runway in front of me.
Besides the ILS approach, these days the GPS approach is becoming increasing common - especially at smaller airports that do not have ILS facilities. Many GPS approaches now allow you almost the same level of accuracy as the ground-based ILS. So what happens if you don't see the runway and the weather is just too bad? You have several options, you can go missed approach and try again or you can shoot for an alternate airport where the weather is hopefully a bit better.
WBRC First Alert Chief Meteorologist