Originally Posted by
FlightDetent
The PWS even has an amber memo on the E/WD before take-off. Fursty's argument accepted in general, hiding that particular one from the INOP system does not sound realistic.
Checking the FCOM, my assertion about PWS not being connected to RA (in line with sonic's reasoning) is not true.
Possible solution? In the absence of valid RA signal, the PWS defaults to ON.
Yep very true, but this is for newer MSNs / non retrofitted ones, for older ones :
The weather radars have a Predictive Windshear System (PWS) that operates when:
‐ The PWS switch is in the AUTO position (Even if the weather radar is OFF), and
‐ The aircraft is below
2 300 ft AGL, and
‐ The ATC is switched to the ON, or AUTO, or XPDR, or XPNDR, position (depending on the ATC
panel), and
‐ Either engine is running.
radio height is not mentioned, nor it is mentioned in any other part of the FCOM whereas everything related to the PWS is mentioned as "AGL". My assumption is that the system takes its vertical information from the terrain database, not the RAs. On the other hand I had once engineering resetting both RA C/Bs after a weather radar malfunction during taxi-out, and that fixed it. Did not have enough time back then for a thorough explanation and later forgot about it... so it could indeed have something to do with the PWS too, but then why not list it as inop ?