757 Gpws

[POL.777]

On the 737-NG the input to the EGPWS is the Capt. Radio Altimeter, #1GS, FMC, #1ADIRU, landing gear and flap switches, SMYD. If loosing the Capt. radio alt. no GPWS will work.
Is this also the case in the 757.

(just a student pilot with a huge interest in Boeing systems)

Cheers

[OBK!]

It depends what causes the loss of the captains radio alt. obviously if its the Radio Alt unit itself then your not going to get GPWS as the radio alt unit has a direct feed to the GPWS me thinks.

I might stand corrected tho.

[expedite_climb]

Can't tell you the system specifics but have flown one with the capts rad alt failed (twice actually), and the EGPWS and GPWS were fine.

Our winter sim a while back was also based on this failure :

While gear is not down, effects are :

i) With either throttle at idle EICAS warning GEAR NOT DOWN, with no aural alert.
ii) With either throttle at idle and flap in any position other than up, EICAS warning GEAR NOT DOWN, with aural alert.
iii) With either throttle at any position and flap at either 25 or 30, EICAS warning GEAR NOT DOWN, with aural alert.

[Golden Rivet]

GPWS operation with L/H Rad Alt inop is dependent on whether you have a singe or multi-source datalink.

Later 757/767 aircraft have the multi-source datalink whereby any Rad Alt can supply the GPWS

All 757/767 with EGPWS will have the multi-source datalink.

[POL.777]

Very interesting info. Thank you very much.

Bst rgds POL