What a wet microburst looks like

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Craig Good

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Sep 4, 2015, 6:25:16 PM9/4/15
to Ipse Dixit

Brian Howell

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Sep 14, 2015, 11:30:20 AM9/14/15
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Let's hope we get a bunch of these: they look like they dump a big dollop of rain!

I was on an aircraft years ago that flew through a dry microburst as it was taking off from Newark. It was mid-evening. There'd been thunderstorms in the area—our departure was delayed an hour because of the weather. Just a few seconds past take off, the plane surged strongly downward for several seconds, slamming us against our seat belts; the pilots pitched the plane up sharply. The was followed by a sharp uprush that sank us deep into our seats for probably six more seconds; we could feel the gees. A number passengers shouted in fear. Others shrieked. Then we simply resumed our normal departure climb. 

The pilot came on the PA to acknowledge the "bumpy ride" we'd just had and to assure us that the plane was okay; he tried, but did not complete succeed, in hiding the stress in his voice. The flight attendants then passed through the cabin to check out the passengers; they looked rather shaken—literally.

I've been through bad turbulence and this was a far worse experience. Perhaps, though, it was more intense in part because we were just a few seconds clear of the ground and it felt like we were going to be smashed into it. I think most of the passengers—and I'm even betting some of the flight crew—were thinking we were going to crash. There'd been a microburst-induced fatal Delta airliner crash at Dallas/Ft. Worth (DFW) just a few weeks before: https://en.wikipedia.org/wiki/Microburst#Danger_to_aircraft.

The woman sitting next to me in the middle seat had just days before completed a "frightened flyer course." This was her first actual flight: an hour's hop up to Syracuse, accompanied by her very supportive husband. After our ordeal, the stress showing in every limb, every joint, and every line of her tear-soaked face, she turned to her husband on the aisle and simply said "We. Are. Taking. The. Train. I am never getting on an airplane again." I think she left finger marks in the armrests, she was gripping them so hard up until the moment we safely, and gently, landed in Syracuse. 

A few weeks after the DFW crash—and our little adventure—the FAA mandated the installation of Doppler RADAR and other instrumentation at commercial airports. Three years later the FAA required that all commercial aircraft have windshear (microburst) detection equipment on board: http://www.nasa.gov/centers/langley/news/factsheets/Windshear.html. 


I find it interesting that Wikipedia's first illustration of a microburst is one occurring over a pair of airport runways: https://en.wikipedia.org/wiki/Microburst

On Friday, September 4, 2015 at 3:25:16 PM UTC-7, Craig Good wrote:

jack saunders

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Sep 14, 2015, 12:23:03 PM9/14/15
to Brian Howell, Ipse Dixit
What exactly are we looking at in the video?  Does micro refer to the small territory covered by a sudden downpour of rain.....therefore highly concentrating the water's mass on one small patch of dirt?  That would roil the air big time, one supposes....like dumping a bucket at your feet, rather than sprinkling from a watering can.
 


From: Brian Howell <bdho...@gmail.com>
To: Ipse Dixit <Ipse-...@googlegroups.com>
Sent: Monday, September 14, 2015 8:30 AM
Subject: [Ipse Dixit] Re: What a wet microburst looks like

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Craig Good

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Sep 14, 2015, 12:59:08 PM9/14/15
to jack saunders, Brian Howell, Ipse Dixit
A Microburst refers mostly to the wind. It’s a rapidly descending column of air that spreads out in all directions when it slams into the ground. It does usually have a lot of water in it as well. The danger for aircraft comes from flying through one and changing rapidly from a high headwind to a high tailwind. This can leave the plane without sufficient airspeed to remain aloft.

The canonical accident was Delta 191: https://en.wikipedia.org/wiki/Delta_Air_Lines_Flight_191

The data from that flight were used in the Boeing 727 simulator at NASA Ames to develop a recovery technique. Even the check pilots kept crashing in their first attempts. They finally arrived at what is, to pilots, a counter-intuitive technique which involves pulling back on the yoke right into the “stick shaker”, which is how the plane warns that it’s about to stall. Trust me, being near a stall near the ground is uncomfortable. But it works. It sounds like that’s exactly what the pilot on Brian’s flight did, and would explain any agitation in the cockpit.

Years ago some friends and I got to fly that simulator around for a night. Lots of stories in case anybody’s interested. But our contact at NASA showed us the best thank-you letter ever. It was from one of the check pilots that was part of the microburst recovery program. He had encountered a microburst in real life, and the technique saved the airplane.

Microburst encounters are much more rare now because of better detection technology at large airports, and the knowledge that they are just a Bad Idea. It’s SOP to divert or hold aircraft if that kind of storm is stomping around an airport.


On Sep 14, 2015, at 09:22 AM, jack saunders <jack...@pacbell.net> wrote:

> What exactly are we looking at in the video? Does micro refer to the small territory covered by a sudden downpour of rain


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--Craig WWJGD?
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"I get up every morning determined both to change the world and to
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Brian Howell

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Sep 14, 2015, 1:24:50 PM9/14/15
to Ipse Dixit
On Mon, Sep 14, 2015 at 9:59 AM, Craig Good <clg...@me.com> wrote:
The canonical accident was Delta 191: https://en.wikipedia.org/wiki/Delta_Air_Lines_Flight_191

Yep, that's the one I cited. I'm sure it was on a lot of minds that evening, including mine. I did think we were going to crash. 
 
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jack saunders

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Sep 14, 2015, 1:33:23 PM9/14/15
to Craig Good, Brian Howell, Ipse Dixit
So a small plane without power to spare is....what?  Toast?
 

From: Craig Good <clg...@me.com>
To: jack saunders <jack...@pacbell.net>
Cc: Brian Howell <bdho...@gmail.com>; Ipse Dixit <Ipse-...@googlegroups.com>
Sent: Monday, September 14, 2015 9:59 AM
Subject: Re: [Ipse Dixit] Re: What a wet microburst looks like
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Brian Howell

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Sep 14, 2015, 1:44:21 PM9/14/15
to Ipse Dixit
It was the kind of event you never, ever forget; what psychologists call a flashbulb memory. The details are vivid. 

Do you remember where you were when Loma Prieta struck? Or when you heard/saw that the Challenger exploded? Or when you saw one of the Twin Towers fall on 9-11? Those are flashbulb memories. Some of us remember where they were when Kennedy was shot. And probably MLK. Those are flashbulb memories, too. 

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jack saunders

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Sep 14, 2015, 1:55:57 PM9/14/15
to Brian Howell, Ipse Dixit
Oh, I remember Loma Prieta well.  I was under the bay in the BART tube, heading home to catch the World Series.  Felt absolutely nothing except the rollicking lickty-split speed of the train I wanted to go as fast as possible.

As we emerged from the water on the east side, the train slowed to a walk.  Then came an announcement:  "We have had an earthquake, and it's our policy to check the tracks, so we'll have a bit of a delay." 

"Goddam fools," I grumble.  "We have earthquakes all the time.  I'm going to miss the first pitch for this bullshit?!?!"

Moments later as we inched up toward West Oakland I looked out to see the clover leaf freeway absolutely vacant on all loops....at 5:10 pm on a Monday afternoon. 

"Oh.  That kind of earthquake.  Like the end of the world."

BART said leave the train, leave the station, game over.  And have a nice day.

 

From: Brian Howell <bdho...@gmail.com>
To: Ipse Dixit <Ipse-...@googlegroups.com>
Sent: Monday, September 14, 2015 10:44 AM

Subject: Re: [Ipse Dixit] Re: What a wet microburst looks like
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Craig Good

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Sep 14, 2015, 2:04:43 PM9/14/15
to jack saunders, Brian Howell, Ipse Dixit

On Sep 14, 2015, at 10:33 AM, jack saunders <jack...@pacbell.net> wrote:

> So a small plane without power to spare is....what? Toast?


Light aircraft are more susceptible to turbulence due to low wing loading, but actually have an advantage in wind sheer conditions. They respond almost immediately to power changes, and can change their airspeeds much quicker than the heavy iron. Jets not only have inertia working both for and against them, but jet engines take a long time to spool up. A propeller on the front yanks you along almost immediately. It also blows air right along the control surfaces. The airliner has to wait for the engines to produce more thrust, and then for that to translate into airspeed.

So the little guy avoids microbursts because they can just slam him into the ground, but has a better chance of making it through a wind sheer event.



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