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Predictive windshear warning

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Predictive windshear warning

Old 27th May 2022, 03:47
  #21 (permalink)  
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[QUOTE=FlyingStone;11235651]It's still predictive, as you aren't in windshear conditions just yet.

Why are you flying approaches at 270 kts?

What if within 1.5 miles or 5 miles is just clear air and there is vicious weather in the go around path.
My point is that the system design has a flaw and 1.5 miles does not qualify to be called a prediction imho.
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Old 27th May 2022, 03:52
  #22 (permalink)  
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However, if i do get a ĄGo Around, Windshear Aheadď i will continue to follow it. Not doing so will probably get me on No Fly status if not fired.[/QUOTE]

That's my point, job pressure can cause an accident. In my experience the PWS system is flawed. i would follow a reactive warning if I were in or close a CB but nothing else. There are flaws in the PWS system.
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Old 27th May 2022, 03:55
  #23 (permalink)  
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Originally Posted by Qwark View Post
It may commence as an ADVISORY, become a CAUTION and then become a WARNING. It unlikely to be an instant WARNING. But could be depending on the aircraft altitude and whether climbing or descending. The alerts are only available for a narrow altitude range.
That's how it should be, i agree but it's not.
It's a warning and is mostly false. Pilots though react to it just to avoid losing their jobs.
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Old 27th May 2022, 15:08
  #24 (permalink)  
 
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If there’s vicious weather on your standard published go-around path then either you advise ATC that, in the event of a go-around, you require an alternative ATC approved track (of your preference), or runway (if available) or you don’t carry out the approach in the first place and divert. For example, Milan 36 go-around paths are frequently entirely coloured in red on the Wx radar during the Cb season.
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Old 27th May 2022, 23:00
  #25 (permalink)  
 
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Originally Posted by bobdazzle View Post
Why is a warning issued within 1.5 NM called a predictive warning. That's 20 seconds lead time in a airplane at approach speed. Hardly predictive imho.
Its predicting in a short space of time you will encounter windshear. Therefore it is ďpredictiveĒ.

The amount of time given is plenty to avoid it.
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Old 28th May 2022, 09:46
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Would you ignore a TCAS RA if you couldn't see the intruder? (who might be above you, below you or behind you. Or in IMC).

Can you see a microburst ? Can you see wind-shear?

The doppler RADAR can detect fast moving wet air, i.e. wind-shear or a microburst, so the PWS issues a warning or an action. Why would you ignore that?

What have you got to lose by following a PWS - even if it turns out later to have been false? (as said above, if there is a CB in your go-around path, you should have already told ATC that you will be delaying your approach, or at the very least, turning to avoid it.

Better to follow PWS than assume it is a false warning.

From Airbus FCTM:

WINDSHEAR PHENOMENON
Windshear is a sudden change in either wind speed or direction, or both, over a relatively short distance. Windshear occurs either horizontally or vertically at all altitudes.

Windshear can result from a microburst. Microbursts occur close to the ground and are a possible hazard to the safe flight of the aircraft for the following two reasons:
  • The downburst of a microburst can result in strong downward winds (40 kt can be reached)
  • The outburst of a microburst can result in both a large horizontal windshear and a wind component shift from headwind to tailwind (horizontal winds can reach up to 40 kt).
An aircraft that approaches a microburst will first encounter a strong headwind. This can result in an increase in the indicated airspeed. This may cause the aircraft to fly above the intended flight path and/or accelerate. With a fixed speed on approach, the flight crew’s reaction may be to reduce power. This will cause the aircraft to fly with reduced energy through the downburst. The wind will then become a tailwind. The indicated airspeed and lift will drop and the downburst may be sufficiently strong to force the aircraft to lose a significant amount of altitude. The degraded performance, combined with a tailwind encounter, may cause the aircraft to stall.

AWARENESS AND AVOIDANCE
Awareness of the weather conditions that cause windshear will reduce the risk of an encounter. Studying meteorological reports and listening to tower reports will help the flight crew to assess the weather conditions that are to be expected during takeoff or landing.

If a windshear encounter is likely, the takeoff or landing should be delayed until the conditions improve, e.g. until a thunderstorm has moved away from the airport.

And

When the airshaft of a microburst reaches the ground, it mushrooms outward carrying with it a large number of falling rain droplets. The radar can measure speed variations of the droplets, and as a result, assess wind variations. This predictive capability to assess wind variations is performed by the Predictive Windshear System (PWS). The PWS automatically operates below a given altitude (Refer to FCOM/DSC-34-SURV-30-20 General), if the radar is ON or OFF, provided that the PWS sw is in the AUTO position.

Last edited by Uplinker; 28th May 2022 at 09:56.
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Old 28th May 2022, 16:10
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Originally Posted by Uplinker View Post
Would you ignore a TCAS RA if you couldn't see the intruder? (who might be above you, below you or behind you. Or in IMC).
Totally agree with everything else. But, just to clarify, we are trained to always follow RAs, even if you have the other traffic in sight, and I think most companies do.
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Old 28th May 2022, 20:56
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That was my point
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Old 28th May 2022, 23:09
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Originally Posted by Uplinker View Post
Would you ignore a TCAS RA if you couldn't see the intruder? (who might be above you, below you or behind you. Or in IMC).
Yes. When thereís traffic the TCAS canít see. Itís happened before.
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Old 29th May 2022, 02:56
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Originally Posted by Check Airman View Post
Yes. When thereís traffic the TCAS canít see. Itís happened before.
When TCAS can't see the traffic it can't trigger RA. You see it and avoid. The question is when TCAS RA is telling you to descend will you ignore it climb instead? Then how do you know what will the guy do? Not following RA is dangerous.
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Old 29th May 2022, 04:27
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Delta191 Lockheed 1011 fatally crashed at Dallas FW while going through a single CB on ILs path. That triggered the research to identify the vertical movement inside a CB. It triggers the warning when it crosses a certain threshold.
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Old 29th May 2022, 08:39
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Originally Posted by Check Airman View Post
Yes. When thereís traffic the TCAS canít see. Itís happened before.
Oh dear, I truly hope youíre not serious.

If it canít see the other traffic, it will not issue an RA.

It RELIES on all aircraft following the coordinated advice itís giving.

Follow the RA and then sort yourself out.
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Old 29th May 2022, 09:16
  #33 (permalink)  
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Originally Posted by vilas View Post
Delta191 Lockheed 1011 fatally crashed at Dallas FW while going through a single CB on ILs path. That triggered the research to identify the vertical movement inside a CB. It triggers the warning when it crosses a certain threshold.
Quite so, added Dr Tetsuya "Ted" Fujita's name to our lexicon. (he passed away in Nov 98... )

The geometry of DL191's encounter is a major badness to the day at Dallas.
The alert inhibiting is quite smart in ir's own way, it should avoid the sort of question that has arisen in this thread... further out from the threshold increases the potential for getting a downflow to increasing tailwind event in a microburst. strategically, taking a hold is not a bad idea, but stuff happens to best-laid plans. Making a decision to continue while having a PWS blaring at the warning level would look pretty interesting at the subsequent court of inquiry. Assuming that you have a QAR type program you are guaranteed to be getting tea and biscuits from management who may not ascribe to your point of view. Reminds me of a discussion around the bar once when a newly minted driver was telling all 'n sundry around the table which of the companies policies he declined to follow by choice, which led to the laconic and polite comment by the Director of Standards, "then, pray tell, what other company policies do you wilfully disregard?". The standard that would apply to a deviation from a trained response would be unless a greater emergency exists. To that end, describing the morning after that the landing with the raucous noise until inhibiting occurred was the lesser emergency would probably get the grey-haired guys at the table busy with their eyebrows... muppet style!

The conversation would be even more interesting if they are digging the gear out of the mud off the side of the runway...

Old Guys



runway offs come in various flavors and varieties... the one below had the crew asking for a tow truck... needed a bunch of bulldozers and angle grinders.

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Old 29th May 2022, 09:30
  #34 (permalink)  
 
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From Airbus FCTM:
I tried to upload this explanation of a microburst earlier, but the drawing didn't upload. Here is a screen shot:

I have seen aircraft flying under huge CBs as they approach a runway, and hoped for their sake that a microburst did not suddenly descend on them.........


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Old 29th May 2022, 09:55
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The main point of having a detection and alerting system is to improve the level of safety above that based on unaided human performance (thus EGPWS, ACAS, Windshear).

Pilots who believe that they know better - ‘its false warning’, are deluding themselves and depriving the industry of its improved safety record for these type of accidents.
‘False’ is like ‘error’ it can only be determined after the event, which is based on outcome. All alerts and warnings should be considered real and acted on.
The safety statistics indicate that modern technology has far superior performance - error rate / false warning, than the human for those specific tasks.

The analysis of an encounter - Captains in Command, #19, compares that event with the FAAs training model #4 (fig 2, and 3), which was derived from the DFW accident. Although event severity is normally associated with big storms, this is not always correct.
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Old 29th May 2022, 10:14
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Our Company says that a Windshear Ahead can be ignored if ‘no signs of windshear are present’ which basically means it is all your fault if it goes wrong.
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Old 29th May 2022, 11:19
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But can you see wind-shear? Can you see a microburst?

No, but your weather radar and PWS can measure it and warn you.
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Old 31st May 2022, 03:37
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Originally Posted by Ollie Onion View Post
Our Company says that a Windshear Ahead can be ignored if ‘no signs of windshear are present’ which basically means it is all your fault if it goes wrong.
Not sure about the latest FCOM but before when PWS warning was still a memory item it was written that if the crews make a positive verification that no hazards exist then the alert may be disregarded. Alerts can be spurious. It's all about common sense. If it's clear weather outside, and you have a PWS alert then obviously you can assess the situation and ignore it. Now if there are CBs activities on final then it's a no brainer IMHO, follow the PWS warning. We are pilots after all we should not follow blindly what a computer is telling us to do. I have seen a guy asking me to request weather deviation cause the weather radar was showing a predictive overflight Icon, new feature on the latest weather radar indicating the risk of a fast growing cells ahead of the aircraft. It was during day time and there was absolutely nothing!! I was like: Are you trolling me right now? Pilots don't even look outside anymore...

Last edited by pineteam; 31st May 2022 at 04:07.
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Old 31st May 2022, 06:11
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Originally Posted by vilas View Post
When TCAS can't see the traffic it can't trigger RA. You see it and avoid. The question is when TCAS RA is telling you to descend will you ignore it climb instead? Then how do you know what will the guy do? Not following RA is dangerous.
In the situation Iím familiar with, there were 2 intruders, and TCAS issued the RA without knowing about the 2nd aircraft. The crew could not comply with the RA.

An outlier, yes, but technology doesnít always have the full picture.
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Old 31st May 2022, 06:12
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Originally Posted by ScepticalOptomist View Post
Oh dear, I truly hope youíre not serious.

If it canít see the other traffic, it will not issue an RA.

It RELIES on all aircraft following the coordinated advice itís giving.

Follow the RA and then sort yourself out.
See my reply to Vilas above.
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