Windshear Warning
 

When aproaching ORD from the east in a A320 yesterday, we suddenly begun climbing shortly after coming over land from the lake.

Later the annuncement was made, that because of windshear warning, they decided to land at a different runway. Can I trust that explanation?

Are all planes eqipped with Windshear warning system? If the answer is no, I would be kind of scared to fly any plane without the system.

I also wonder, if other planes behind us also were diverted to a different runway.

Windshear measurement equipment is on the ground, and available to the controllers in the tower.

They are the one who elected to redirect traffic to a new runway.

windshear alerts (i.e. alerts before it ouccrus) is frequently ground based. Lots of wind meters around the airport can detect wind at different directions. ATC can realy that message.

Not sure if some planes these days have built in windshear detection. Maybe they link into a ground based system. Anyway, if the crew senses the windshear, shovs in the power, and goes around, then you'll be OK.

About 3-4 years ago I was sitting in the first row of a Swissair A320 flying ZRH-NCE, the cockpit door was open as we were landing.......

As the rear wheels touched down, the plane jinked to the side and a computer voice started screaming PULL UP, PULL UP, PULL UP (continuously). The pilot increased power and pulled up, we circled for another 20-30 minutes and then landed. We were told later that it was wind shear-----this leads me to believe that some part of the system is in the plane as the voice came from the console.

Major airports in the US now have doppler radar installations to detect windshear. It is much more accurate than the old set of anemometers placed around the field. The controllers issue alerts to flight crews and the pilot makes the decision whether to continue or abort the landing. Very few continue.

The Ground Proximity Warning System (GPWS) has a number of warning modes, one of which is windshear. The "Pull Up" alert is not the windshear mode.

Here are the seven modes:

Mode 1: Excessive sink rate
Mode 2: Excessive terrain closure rate
Mode 3: Altitude loss after takeoff
Mode 4: Unsafe terrain clearance
Mode 5: Excessive deviation below glideslope
Mode 6: Advisory callouts
Mode 7: Windshear alerting

Each has it's own specific audio alert(s).

WHich one is "pull up" then?

Most newer aircraft have built in Windshear warning sensors. They look like little wings near the nose on each side of the aircraft.

Pull up, Pull up is actually only modes 1 and 2, BUT all of the other modes (except 6 and 7) are interwined. Ie, If you get a glideslope deviation (usually low) you are "usually sinking to fast" (mode 1) and are too close to the ground (mode 2) (TERRAIN aural warning) . The intial callout will be a "glideslope" Aural warning twice, it can be a combination of "glideslope, PULL-UP" twice

Mode 4 will flash RED on the TCAS and have GROUND on the screen, it will be followed by PULL-UP twice )(mode 2)

Winsdhear DOES not call pull up, pull up.. Because in certain windshears you need to dive to regain airspeed. The Aural warining is Windshear twice followed by command bars indicating the path of travel to take as well as a visual warning (in yellow) on the EFIS of "Windshear".

If there is Windshear in the vicinity of the airport, it is reported well in advance of landing or takeoff (landing is more critical) and it is ground based. Secondly, upon landing a pilot will report airspeed deviation and altitude of deviation to the tower who will report it to all other aircraft. Ie, An A320 reported +/- 15 kts, 250-350'. Not all airports have windshear advisory systems, so each aircraft upon landing can and will usually report windshear advisories.

Mode 6... gives the pilots a call out at specific heights above ground, the minimum altitude and several others.

Generally, ANY PULL UP or TERRAIN aural warnings that are not in visual conditions automatically warrant a go around. If a crew are in visual conditions (usually DAY only) they can choose to ignore and continue the approach. At some airports you will get "false" warnings on some approaches.

Windshear is how the FA described it. Doesn't mean that that is what it was. The voice was however very spooky.

Thanks for the extremely informative post, dondk, and welcome to FlyerTalk.

Does the GPWS get switched off, either automatically or manually, at some point in the landing process? That is, during a normal landing when the a/c is about to touch down just beyond the runway threshhold, does GPWS complain about being too close to Terrain?

I seem to recall hearing warning bells and "wind shear, wind shear" while sitting in F waiting for a pilot to complete his checklist. I can't remember which aircraft.

As for the reason for an aborted landing, I don't much care. Get me safely on the ground and tell me you were dodging Santa's sleigh - works for me!

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"I will not be pushed, filed, stamped, indexed, briefed, debriefed or numbered. My life is my own."

This is exactly what happened to our flight from Casablanca to London, as it was making its only stop in Gibraltar. There was a horrible windshear (I guess Gibraltar's small airport doesn't have a windshear warning system), and the stupid pilot attempted to land, but couldn't and pulled up and landed at Malaga. Thank God BA saw his incompetence and after we landed in Malaga, ordered him to evacuate the plane, and was unexpectedly replaced by a different pilot. I remember even the flight attendant saying to another passenger, "on a scale from one to ten, that was a nine."

Speaking of which, did anyone see "White Squall"? Is that windshear? Has anyone ever experienced this?

More recent systems will give one of the two windshear warnings:

"Windshear! Windshear! Windshear!"

or

"Windshear! Caution."

If you hear "Pull up." or "[whoop whoop] Pull up," then that is something completely different.


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daniel baker -- [email protected]
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