EGPWS and radar

[Will]

Hardy,

There is frequently a bit of color on the ND's that you post... I'm guessing EGPWS, but for all I know it could be radar.  Do you have the radar functioning yet?  If so, can you post a shot with both kinds of returns visible at the same time?  I'm interested in learning how to tell the difference.

(If you dont have time, no worries, I can wait.)

Will

[John H Watson]

Will...

When EGPWS (Terrain) is in use, it will be annunciated in cyan on the left hand side of the ND ("TERR").
Similarly, WX, WX+T, etc, will be annunciated when the radar is in use.

Regards.
JHW

[Will]

Can they both be used at the same time?

[John H Watson]

No. There are switching relays which only allow one at a time.

The graphics on the real aircraft displays are too close to their limitations to show both at once, but even if they weren't, it would be too confusing with both showing at the same time (Is that mountain really a cloud? ... and vice versa)

Regards.
JHW

[John H Watson]

P.S. Note that there is nothing stopping you from having Terrain on one ND and Wxr Radar on the other ND.

[Lasse]

Thats actually the configuration we normally use. PF has the weather and PM has the terrain presented on the ND.
Even in very good weather we still turn on the weather radar since the windshear logic needs 12 seconds after engines (1 or 2 for 737,777 and 2 or 3 for the 744) are in takeoff range. By turning on WXR at line up we have windshear protection from the beginning of the takeoff roll...

/Lasse

[Jeroen D]

Lasse,
Why does the wind shear logic need 12 seconds to be ready? Something to do with gathering data to recognize patterns or so?
Jeroen

[Will]

I was thinking that weather and terrain could be displayed simultaneously, because the ND on Hardy's post of the KSTL LDA 30L shows the following in blue:

WX+T
-1A
-G3

So how does one interpret the above?  Thanks for the info.

[Lasse]

Yes, the 12 seconds are for the PWS (predictive windshear system) computer to calculate the doppler radar return, inertia data and air data... Honeywell calls it qualifier logic.
For takeoff the PWS will start scanning for WS by either throttles in takeoff range or by pushing theWXR button on the EFIS control panel. PWS turns off automatically when the airplane climbs above 2300 RA.
However all PWS cautions or warnings are inhibited above 1200 RA both for takeoff and landing.
For approach PWS turns on automatically when the airplane descends below 2300 RA. PWS turns off when the airplane lands (60 KIAS) or climbs out of 2300 RA...

For terrain presentation there will be a "TERR" in blue/cyan. The green clutter you see has to be weather. (Unless Hardy is testing something) Terrain can be presented by the WXR radar if we tilt it enough down. However it will show as red due the great reflection. And since we understand red as danger then its bad airmanship to do...:-)

So the logic of the CDS (commen display system) is that you cannot select WXR and TERR at the same time for the same ND...
You can however have windshear caution or warning and "normal" weather presentation at the same time...

Hope it helped a little
/Lasse

[Will]

That's very helpful, thanks. But what about the blue WX+T, -1A, -G3 (see above)?

[Jeroen D]

Thanks
Jeroen

[Lasse]

The WX+T is weather and turbulence is selected on the radar control panel.
Turbulence is shown as magenta, weather is green,amber or red...
The -1A is the tilt of the radar. Here 1 deg down. The A is that its in auto.
When setting up the radar manually you would normally set 80nm range and tilt the radar down until you'll get a weak ground reflection (still shown in green) at the very top of the display then the tilt is set perfectly. Reason is that the top of cumulus nimbus clouds are ice crystals and does not show on radar so you wanna hit the water part of the cloud...
You can get a lot of options from Boeing on the equipment, some panels have a AUTO TILT switch. Then the radar will do the tilting for you...
The -G3 is the gain. Gain is the sensitivity of the radar. Again the options are many and I haven't seen the panel Hardy is simulating. The scale could go from MIN -7,-6,-5,-4,-3,-2,-1 MAX... CAL, if you see that means calibrated witch is the auto function and VAR is variable with means manual control... But again Im not sure what brand/type Hardy is simulating here... But the difference between panels and operating methods are small (different words for the same function)...- the general way of operating them are basically the same...

/Lasse

[John H Watson]

I believe Hardy is modelling the Rockwell Collins WXR-2100 Multiscan Radar system.

http://www.smartcockpit.com/data/pdfs/flightops/aircraft/Collins_WXR-2100_Operator's_Guide.pdf

(747-400 version)

Regards
JHW

[Will]

Hey, that explains everything. Thanks, guys.

Will

[Hardy Heinlin]

Here are some pics with EGPWS Peak Mode active (Ocean inactive):

http://yssyforum.net/will/ezesyd/2.JPG

http://yssyforum.net/will/sydeze/2.JPG


Cheers,

|-|ardy