Articles, Operations, Safety
Posted on Mar 29, 2021
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IF YOUR AIRCRAFT IS CATEGORY A, should you always use those minimums?
According to FAR 97.3, an aircraft’s approach category is based on a published speed called VRef. It’s the approximate speed for flying a stabilized final approach. When VRef is not specified for an airplane (which is the case for most light aircraft), VRef equals 1.3 X VS0 or the stalling speed of the aircraft in a landing configuration.
Each approach category corresponds with the minimums you’ll find at the bottom of an instrument approach (shown below).
If your airplane is certified as “Category A,” that doesn’t mean you should always use Category A approach minimums. According to the AIM, if it becomes necessary to fly faster than the aircraft’s published category, the minimums for the higher category must be used.
Example 1 (Cessna 172 Skyhawk, Category A): If you fly the final approach segment at 95 knots (indicated), you must use Category B minimums.
Example 2 (Cirrus SR22, Category A): If you fly the final approach segment at 125 knots (indicated), you must use Category C minimums.
Sometimes minimums don’t change across categories, like in the ILS shown on the opposite page.
In years past, the AIM suggested that pilots choose straight-in minimums based on the certified approach category of the aircraft flown. That’s not the case anymore.
Today, it’s all based on your indicated airspeed flown (circling and straight-in). This update makes sense because higher minimums correspond with higher speeds. When you fly faster, you have less time to react to a missed approach as you bring yourself closer and closer to the ground. Higher minimums give you a higher safety margin when you’re flying fast.
Approach minimums for all categories on this ILS are all the same.
There’s nothing more frustrating than getting stuck flying along a 10- or 20-mile-long ILS course at approach speed in a light, single-engine airplane. It can feel like you’re hovering, and the long wait results in many pilots flying much faster than the “normal” approach speed for their light airplane.
But there are several reasons why it’s a good idea to fly your recommended speed along a final approach. First off, you develop good habits for the future. If you ever plan to fly a larger aircraft, they can be difficult to slow down. If you fly too fast in a jet (and even a fast prop) on final approach, you’re much more likely to overshoot your landing point.
Another reason for flying at the appropriate approach speed on final is so you have a better chance of descending from MDA to the runway on a non-precision approach. The faster you fly, the harder it is to make a safe descent as you approach the runway. Higher descent rates are always required when flying faster.
It’s the same reason why ATC isn’t allowed to ask you to change your speed on the final approach segment in IMC. When you’re in the final stages of an instrument approach in the clouds, ATC can’t request that you fly faster. Again, this is to ensure that you can get configured and stabilized well before you reach approach minimums.
Higher descent rates are required when flying faster.
There are certain times when it makes sense to fly a fast final approach.
With ice accumulation of 0.25 inches or more on your wings or tail, you should plan to fly with higher power settings, less flaps, and higher approach speeds. Many aircraft manufacturers will publish a minimum icing speed for these instances.
If you have 0.25 inches or more of ice accumulated on your wings or tail, it makes sense to fly a fast final approach.
If you have a flap malfunction and need to fly with reduced flaps, you’ll increase your approach speed as well. Based on your new speed, it might be appropriate to use the next highest approach category of minimums.
The next time you’re shooting an approach, make sure you compare your speed on the final approach segment to the category you should be flying (see approach plate, lower left).
This article was initially published in the February 2021 issue of COPA Pilot.
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