Rotor and Wave: Do Not Want!

If you are a power plane, that is. If you are a glider, wave can be your long-sought friend.

One of the local weather guessers was pointing to “neat clouds” the other night, and called up a visible satellite image that showed them streaming off of Pikes Peak in Colorado and flowing in a wave-like pattern as far as the Panhandle. Anyone who has flown the Front Range is probably wincing right now, and maybe reaching for the “bag-in-the-back-of-the-seat-pocket.”

Rotor and wave are what happens when the wind encounters certain kinds of obstructions, leading to a hydraulic jump. Water does the same thing, but we don’t fly through water. The flowing air is forced up, over and around the thing in the way. In some cases, as last week, it is a lone summit (Pikes Peak.) In other cases it is part of a mountain range, such as the Manzano Mountains in New Mexico, or the Eifel region in Germany, or the Appalachians. What goes up will come down, then back up, forming waves. Because the air is constantly flowing, the waves don’t move relative to the ground, becoming “standing waves.”

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The swirling bit is not, repeat not where you want to be. If you are lucky, you will get shaken around and spit out a little worse for wear, but intact. If you are not lucky, your plane will get torn apart. If you look at the picture, you see that there is a big dip in the airflow on the lee (downwind) side of the mountain. That will slam you into the ground if it is strong and you are not paying attention. Rotor and wave is not a happy thing for power planes to see. Colorado Springs airport has had to close on occasion because the bottom of that wave set up right at or very close to the airport. It wasn’t safe for planes to come or go.

If, however, you are in the top of the wave in a power plane, you will ride along, smoothly gaining and losing altitude like in an elevator (assuming that the air traffic controllers will give you a wave block. Occasionally they will, since everyone is rising and falling at the same rate, keeping separation.). If you are in a glider? Wheeeee! You can get into the wave and ride it for hours and hours, and miles and miles, or linger over one spot for a while, lurking in a designated “wave window.” It’s great fun, albeit a little disconcerting for a power plane pilot to hover while showing air speed. You see, the glider is stationary relative to the ground, but the air is moving past. Airliners were going under me on their way into and out of Albuquerque.

Mt. Ranier is another peak infamous for rotor and wave. There are dozens of aircraft buried on the glaciers, slapped down by the wind for getting too close when the conditions were just right. Rotor and wave often come in clear air, or with just a leeeeeeeetle lens-shaped cloud (lenticular, or lennie), or a small cap that happens to be churning and swirling, constantly torn apart and re-formed. That means “airplane go home.”

So when the weather dude was rhapsodizing about the cool clouds, I was wincing at the thought of the turbulence. And wondering if anyone had had a chance to hop into a glider and go play.


8 thoughts on “Rotor and Wave: Do Not Want!

  1. Egad, that brings back a long-suppressed memory. I didn’t quite need the little bag, but when the commuter plane landed at DFW the terminal building kept swaying and pitching.

  2. Minnesota, being Mostly (but NOT Completely) FLAT doesn’t much likely to cause that.

    Still, I recall back when $HOOTERVILLE had commercial airline service, after a fashion. And often there’d be an email about someone who had flown in from The Cities (MSP) *BEGGING* for surface transport to MSP rather than flying on the “puddle jumper.” Me? I’d have *LOVED* to have been able to ride on the “puddle jumper” (after a J-3, not much fazes a creature, in most conditions… “Where’s the fuel gauge?” “See that wire sticking out of the cowling? It’s got a cork on the end of it.”)

    • Type “Gimli Glider” into your search bar to find out why a cork with a wire can be *way* better than electric fuel level senders and gauges.

      There would be practical problems using corks and wires on a jumbo… but if the flight crew had been able to do a visual on fuel level instead of taking someone’s word for it, they would never have left the ground.

      • Ah yes, the Gimli Glider. Such makes me think of the alleged comedian I saw on TV years ago going on about there was a guy using a stick to dip into the tank (top of wing fill…) and he wanted gauges. And my reaction was pretty much, “No, you don’t. The guy with a stick knows how much is in the tank. The guy with a gauge only believes he knows how much is in the tank.”

  3. What is this “Piles” Peak, and where exactly is it? Anywhere near PIKES Peak? I notice that L and K are next to each other on my keyboard…

  4. Oh yeah… and being held down to 280 by ATC because we were at maneuvering speed of 220kts to keep from getting the wings ripped off… That was a LONG hour to get clear of that stuff. Apparently they don’t give block altitudes anymore. Sigh…

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