It's not so much about GS angle than about sink rate. ACN rw 14 at max LWT on 744 can quite easily trigger the GPWS sink rate warning. At Vapp ~ 165 KIAS, the sink rate required to stay on the glide is about 900 fpm. Approx 300ft agl, there's quite often an updraft which can start to get you a little high if you're not anticipating it. At that point if the sink rate is increased, you easily exceed 1000 fpm & often get the sink rate alert too.
Dont know who you work for but we have an SOP call on 744 from the PNF if ROD is 1000fpm or more in the latter stages of the approach. Its not to do with the GPWS. 1000fpm over the threshold is quite tricky to recover from without either burying it of wasting runway.
Edited to say, Think we work for same bunch, check out standard calls in the Flying Manual. Your Oppo was probably being a little nervy.
With a Vref at Max Landing weight of 160Kt plus say 10Kt wind correction, giving 170Kts ... say the wind is all accross, 5xGS = ROD on a 3deg slope ... so ROD would be around 850ft/min ...
So it's would not be unreasonable to see on occasions 1000ft/min correcting for rising air, going slightly into the whites etc ...
I've always felt, even on the 744, looking out at 50ft a rapid ROD can be easily seen and recovered from so long as one doesnt wait to flare at 30ft! Also in these scenarios delaying closing the throttles helps ...
I quite agree. Esp on steep slopes like CPT or recovering from a VOR 22L into JFK onto the Papis. However it is only a call and i see no requirement about correcting if its necessary. Think its just for awareness as high sink rates develop quite easily.
Draw a line on a graph from 0ft RA/500 ft/min descent to 2500ft RA/4250 ft/min descent. Breaching this line will trigger "Sinkrate". The "Pull Up" line is parallel to it for the bottom 250 ft and diverges from there up. Two other considerations if a valid glideslope signal is recieved the boundary is adjusted to desensitize the alerts (doesnt say by how much though!) also EGPWS offers a "Steep Approach" option for given aircraft types which alter the above to allow steeper than normal approaches and I dont know if this will be the case for you 744! Hope this helps
I've been flying the 744 F for 9 years and have yet to receive a "sink rate" callout even with numerous landings in Prestwick, VOR JFK 22L, Mexico City, Bogota, Quito, and Campinas. This despite most landing weights at max allowable 302.0 thousand kilos (except Quito) and 163 knots approach speed. Yet on almost every simulator ride someone gets a "sink rate" callout on almost every non precision approach flown in the "dive and drive" method. Some checkrides have been busted on more than two sinkrate callouts on a non precision approach, despite visual conditions.
Yep it may well not be 74 specific, its the Allied Signal EGPWS handbook which covers some of the sims I work on here, none of which are 74's! we have from bizjet up to 772 here! So I may well be wrong! Its possible that the figures you give are the desnsitized option but I would be speculating as I have no solid data!
Empty 744F/min fuel. FL450. Approx 100nm out of TLV over Med. No-one lets you down until TLV speaks to you. Being an -F its ok to go down 6-7000fpm without screaming pax selling their story to the Daily Whatever. I have seen GPWS inhibit (by F/O's left knee) being pushed.
Edit: Just studied the graph above properly - so no big deal.