Gust Fronts

June 19, 2013 by Bruce Landsberg

airplaneLast week was the Air Safety Institute’s annual Storm Week. We only do it once a year despite some TV channels celebrating atmospheric mayhem weekly, gusting to daily and sometimes hourly. The webinar that we recorded for posterity was attended by over 900 pilots who had some interest in learning more about boomers from a controller’s perspective, and with some guidance on datalink thrown in. An area we did not spend much time on but deserves more attention is gust fronts. This phenomenon, which does not accompany every thunderstorm, can really make a hash out of your arrival or departure.

To misquote Forrest Gump, “Thunderstorms are like a box of chocolates…”, etc. What looks the same may not be, and benign can turn ugly really fast. The gust front is on the leading edge of the storm and forms when the storm hits maturity. A ripping good downdraft descending at, say, 3,000 feet per minute, has nowhere to go when it hits the ground—except out—usually to the front of the storm. The winds can go from practically nothing to 40 knots in the blink of an eye.

I was in the back seat of a Cessna 172 some decades ago with a new private pilot up front as PIC and an Air Force pilot friend, who was getting his checkout at McConnell Air Force Base in the F105 (affectionately known as the Thud). We’d flown to an airport east of Wichita and it had begun to cloud up, so we decided to return to Cessna Field on the east side of the city. On the west side, about 15 miles away, a pretty healthy thunderstorm had set up shop and shut down operations at the airline airport.

The winds were five knots or so from the northwest as we lined up on short final to Runway 35 but rapidly increased to about 15 -20 knots from the west—close, if not beyond,  the demonstrated crosswind capability of the Skyhawk and well beyond the demonstrated crosswind capability of the pilot. We were about 10 feet off the ground when my Air Force friend strongly suggested a go-around. It was a good call! We headed out east and he turned to me, as senior Cessna driver, and said something to the effect of, “You get your posterior up here and land this thing!” I’m still not quite sure how we managed the seat transfer, but he came aft, I went forward to the right front seat, and we came back around for a second try. By that time the gust had passed and the winds were fairly steady from the west at about 12 knots. I’d like to say it was a heroic save on my part, but it wasn’t—just a normal  Kansas crosswind, and that’s what Cessnas are built to handle.

But there were several good lessons: Don’t judge a thunderstorm by its looks, sitting in the back seat makes it a long stretch to the controls, and when in doubt—go around! I remember all three to this day.

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Bruce Landsberg
Senior Safety Advisor, Air Safety Institute

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  • Walt Woltosz

    Weather started turning bad just as we were letting down from FL340 to 12,000 approaching Borger, TX (KBGD). A large winter storm was well to the northwest, but some low stratiform clouds were in the area ahead of it. First Borger went below minimums (400′). Then Moore County (KDUX) looked good, but within less than 10 minutes it went to just above minimums and was getting worse. So we tried to go to Tradewinds (KTDW) and were only a few miles away and in clear air when a wall of haze materialized in front of us a couple miles away and we got a couple of very strong vertical pops. We started to turn back to the main Amarillo airport when all hell broke loose. The turbulence was extreme – we had things flying around the cabin, and the plane was pitching and rolling like we were in a thunderstorm, but we weren’t. We were in clear air. I’ve never been in such extreme turbulence in my life, including two actual thunderstorms about 30 years ago in Cessna 210s (no weather equipment back then, just forecasts and ATC radar, which was about useless). There was no warning of any kind that this nastiness was out there. I was in the right seat on this leg. The PIC and I both hit our heads and he hit the window next to him in the left seat, knocking his headset off. We declared an emergency and no one else was in the area anyway, so Amarillo tower cleared us to land anywhere we wanted. And we did – landing downwind (on a looong runway) because it was the quickest way to get on the ground before the stuff moved over the airport.

    A Marine Citation was getting ready to take off, as well as an Osprey. We told them about our experience and they decided to spend the night, too.

    It was a very high alert situation, potentially life-threatening, but we dealt with it (and had some luck as well, I’m sure – if we had waited much longer to start our turn, things could have gotten worse.

    Afterwards, we learned that there had been three low pressure centers very close together just southwest of KAMA. We believe we got caught in the counter-rotating flow between two of them. There were no cumulus clouds in sight or other evidence of convective activity. Just that wall of haze (which may have also been dust, in hindsight).

  • Lem Lewing

    Flying in the mountains, 13,000, perfect wx. One gigantic bump out of nowhere. Headsets are underrated as crash helmets. Saved both of us from nasty bumps on the top of the head.

  • Bruce Landsberg

    Wow! Not quite the convective issue we were discussing here but proving the point that weather is where you find it. Many thanks for your thoughts.

  • http://AOPA Jim Borger

    With cold fronts moving in from the northwest and warm moist air coming in from the gulf, gust fronts aren’t that rare through Texas, Oklahoma and Kansas. The military built a lot of airports for training there during WWII in the shape of a triangle so you can land in almost any winds. Taxiing to the ramp is a whole other story. Obviously landing or taking off in the face of a gust front should not be attempted.