Cloud Clearance: The Point and Wait Trick

Cloud-Avoidance

It’s a good idea to avoid the clouds as much as possible. For IFR pilots, you’ll typically find a smoother ride in the clear. VFR pilots have no choice on the matter: per cloud-clearance rules, it’s the law! But what about that cloud out on the horizon? You don’t need a Sporty’s sight-level to tell if you’re going to hit that puffy cumulus up ahead. All you need is a finger!


Here’s the trick:

Point at the top of the cloud.

Point at the top of the cloud.

Step 1: Point
Take your pointer finger and literally point at the top of the cloud. Reach forward and physically touch the window at the top of the cloud.

Step 2: Wait
Keep your head and finger in the same position while maintaining unaccelerated flight: straight & level or steady & stabilized climb or descent.

Step 3: Observe
Observe the cloud’s motion relative to your finger.
If the cloud appears to move below your finger, you will pass above the cloud. But if the cloud moves above the finger, you can expect to go IMC in a few moments.

If cloud moves below your finger you will pass above.

If cloud moves below your finger you will pass above.

If cloud moves above finger, you'll fly into the cloud.

If cloud moves above finger, you'll fly into the cloud.

This whole trick is based on the old collision-avoidance rule that any airplane with no apparent motion must be on a collision course. It’s easy to “eyeball” another airplane and detect relative motion.. Because of the slower closure rates and enormous size of some clouds, it is a lot more difficult to judge motion.

If you don’t mind writing on the windows, you can also use a dry-erase marker to free up your hand.


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About the author
Pat Flannigan is a professional pilot and aviation blogger. He has been flying for fifteen years and is currently working as an airline pilot in the United States.

11 Replies to Cloud Clearance: The Point and Wait Trick

  1. NozeDive says:

    I wouldn’t recommend marking on the windscreen.

    • With how scratch-happy those windows are, thats probably the best plan. But I have seen other CFIs use dry-erase markers to demonstrate a bunch of things (such as drawing a horizon reference point) to great effect. Let’s see, what’s the disclaimer on that? I am in no way responsible if you mess up your window! :-)

      • Julien says:

        Great tip! If your window is the well-used type with plenty of existing scratches on the perspex, you can do without the grease pencil or finger, as long as you remember which scratch the cloud aligned with a few seconds ago. Smashed bugs work quite well too.

        Fingers can come in quite handy for judging angles in a number of in-flight situations, such as slope angles on a visual approach. There’s a nice little explanation here. Incidenly, this may well be where the expression “rule of thumb” comes from: a thumb at arm’s length covers about 4 degrees.

        • So a thumb is about four degrees? I’ll have to play around with that. I’m holding my thumb up at arms length and it looks about right, we’ll see what the attitude indicator says next time I go flying!

  2. I have found that an old fashioned grease pencil works very well and is erasable.

  3. Nice tip, but beware of those clouds with rapid vertical development, they are not so funny to fly in.

  4. Sylvia says:

    Wow, I’m totally taking a grease pencil with me next time!

  5. Ben says:

    Another way to check this is to use a half-full water bottle. Assuming you are in straight-and-level unaccelerated flight, the water in the bottle will be perfectly horizontal. Just look across the top of the water and see if the cloud/airplane is above or below the water’s “horizon.”

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