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HOTROD_0414
13th Sep 2010, 10:35
HI Guys

Been trying my best to understand it, but without any luck :ugh:. As per the book PWS (predictive windshear) scans on the 320 below 2300ft and ATC ON/AUTO, 1 engine running etc etc. But it gives warnings, cautions only below 1500ft.
My question is what happens if the A/C is below 2300ft and above 1500ft and there is windshear ahead??? Will the PWS still show any thing on the ND??
Secondly, what if the A/C is in actual windshear below 2300ft and above 1500ft?? Will there be any alerts,warnings,cautions on the ND??

There's one diagram as per which below 2300ft and above 1500ft, Windshear mode active, there will be no ALERTS/DISPLAYS. :confused:

jtr
13th Sep 2010, 11:45
As I understand it, you are correct. No warnings till 1,500 RA.

Maybe its just co-incidence all along but one port I fly to you can truck on in and the WX is horrid, get to 1,500 and tadaaaa.... PWS gets all excited (we can ignore under certain circumstances in my company)

bio161
13th Sep 2010, 18:25
Hi guys,
I have been looking in the FCOM and actually itīs not so clear.
What i can understand, but i may be wrong, is that in the FCOM1 1.22.40 P6 in the chapter "WINDSHEAR DETECTION FUNCTION" says that this function is provided between 1300 feet and 50 feet on LDG with at least CONF1.

Despite of this on the FCTM 1.34.60 in the section "WEATHERADAR" says that the predictive windshear is activated below 2300feet and displayed on the ND if below 1500 feet.

So, as far as i understand, below 1300 feet you have the actual warning "WINDSHEAR" allerting you are in the middle of a microburst or something like this. Instead from 2300 feet to 1500 feet you have only the aural predictive windshear function which alerts you of "WINDSHEAR AHEAD", from 1500 feet below you will get it as well on the ND and below 1300 feet you will get the FD orders in case of windshear encounter.

I think that these altitudes reflects the theory that in case of a downdraft the air spreads apart only at low level close to the GND and not in the middle of the air with no surface which phisically diverts the wind. But i wonder then about temperature inversions windshears...

I think thatīs the difference..Hope it can help somehow!:ok:

HOTROD_0414
13th Sep 2010, 22:01
Bio161...
where does this config 1 comes from???sorry couldn't find it.
But my interpretation, after reading the book, if the A/C is between 2300ft and 1500ft, there will be NO ALERTS/DISPLAYS :confused::confused:

bio161
13th Sep 2010, 22:15
CONF1 comes from FCOM1 1.22.40 at P6 there are the activation conditions and one of them is to have CONF1.

In my opinion, but i may be wrong as i said before, between 2300ft and 1500ft you have NO alerts on the ND but you should have only the aural synthetic alert voice from the PWS system as "windshear ahead". This is what i get after reading and comparing FCTM and FCOM1. :ugh:

capt. solipsist
14th Sep 2010, 19:08
bio161, that is correct

TyroPicard
16th Sep 2010, 10:38
Well the way I read FCOM... (my FCTM does not mention a/c height, just what to do in the event of an alert)...
HOTROD is correct if the A/C is between 2300ft and 1500ft, there will be NO ALERTS/DISPLAYS bio161
You are Wrong - have a look again at the diagram on FCOM 1.43.60 p4 where it says

WINDSHEAR MODE ACTIVE
NO ALERTS/DISPLAYS

for flight above 1500 ft. "Alerts" are defined on the previous page as warning, caution, or advisory.

Do not confuse PWS with the Reactive Windshear warning provided by the FAC below 1300 ft.

bio161
16th Sep 2010, 13:42
Hi TyroPecard and thanx a lot for your reply!:ok:
And sorry..it was FCOM not FCTM..my mistake!

Could you please check again where you got this info? Because in my FCOM section 1.43 does not exist. Maybe i have an old version. :confused:

Anyway on the FCOM 1.34.60 P2 reports:

Windshear SW:

AUTO: Predictive windshear function is activated: windshear areas are detected by the antenna scanning below 2300 feet RA, even if the SYS switch (1) is set to OFF, and displayed on the ND below 1500 feet.

So my reading tells me that we get a display below 1500 feet but the predictive warning should be active from 2300 feet on.. :ugh:

Or am i missing anything?

PS: i start to think that we have different WX radars on board our A/C and that's the reason we can not find ONE solution to this..
Rgrds to everybody,
bio161

shortfuel
16th Sep 2010, 16:58
FCOM section 1.43 does not exist

It's just a typo. TyroPicard meant 1.34...


Our 320 are fitted with different radars but all PWS function works the same so I don't think it's a problem of radar manufacturer, but just a problem of comprehension:

http://nsa20.casimages.com/img/2010/09/16/100916055720842174.jpg (http://www.casimages.com)

Antenna start scanning at 2300AGL but you won't get any alert above 1500AGL.

latetonite
18th Sep 2010, 14:28
I do not know about the A320, but in the B737, the figures are 2300 and 1200 feet.
In descent through 2300 ft, the PWS system '`activates`', warms up and starts updating the displays, so as to be ready by 1200 ft to give you warnings..