B777 Reject T/O due to PWS
 

Dear all,

This is pertaining to conditions above 80 kts & prior to V1 where B777 RTO should be initiated for following reasons-
As per QRH - eng fail, fire or fire warning, Predictive windshear warning, a/c unsafe / unable to fly.

The PWS 'warning' is inhibited from 100 kts to 50' RA (as per FCOM)
So technically I will never receive a new warning after crossing 100 kts so what is the QRH referring to till V1 with respect to windshear?

What flight deck annunciation am I suppose to get to enable me to Reject for windshear after 100 kts & before V1?

If I am missing something too obvious, apologies for that.

tou can still use your own, built in, human windshear detection system. The criteria are actually given in the Fcom somewhere as to what a winshear looks like. If you've passes 100kts and are having big jumps in wind speed and speedtrend and the likes, you are rotally in a windshear scenario. Captain's judgement and worth balancing with the risks of a high energy STOP. but that's what you're payed for.

You mean Airspeed I hope.

You'll still get the bumble bee visual warning on your map as it's only the aural warning that's inhibited. That's still a PWS in my book and good enough reason to throw out the anchor.

PWS need not necessarily lead to reject take off because you are not yet in WS but reversal or wild fluctuations of trend arrow is sure sign you are in it.

Utter rubbish Vilas,

PWS on take off is a mandatory rejected take off action as instructed by Boeing. Why on earth would you want to take off into it if you have a choice.

Agg Karan.
PWS will activate above 100kts. Try it in the Sim. Its all about RTFQ. " No NEW PWS warning alerts " after 100 kts. So if it is just before 100 and remember you are accelerating then the warning will actually be running well after 100kts.

There is no black and white answer for rejecting for un-annunciated wind shear.
For example - you're accelerating through 130 kts. Two engines, running true, running hot.
Speed drops to 120 kts and stays there for 10 seconds. Reject? Continue? Hope it increases?

Its not un-annunciated ! There talking about PWS

Do you understand that PWS is part of the Weather Radar System and is looking at windshear 0.5 to 3nm ahead of the aircraft? Airspeed indications may be completely normal during the takeoff run. If you get a warning at 100kts with no airspeed fluctuations, do you really want to continue if windshear is 0.5nm ahead? You may be barely off the ground before you hit the windshear.

Ok so in short to confirm after 100 kts,

1) Only aural warnings are inhibited for PWS, but visual indication on PFD/ND will still show.

Any PWS alert should be responded to by the pilot with a reject (<V1), no doubt about that.

Hang on a minute. Boeing inhibited the aural warning at 100kts. Why? I'll bet they reckon that if a warning pops up after 100kts, there is a higher risk that you'll stuff up the reject than getting airborne and dealing with the possible windshear. Also remember that from line-up until 100kt, you have had ample time to actually look at the radar and spot the massive red blob that would/could produce a PWS warning and that if the sky is clear then, there's no way a windshear-potential Cb is going to create itself in the ensuing seconds it's going to take to get airborne.

Are you seriously going to reject at V1-20? -10? if the PM spots the PWS icon on the ND?

No agg karan that's not correct.

All NEW PWS warning alerts are inhibited at 100kts. So you wont get anything NEW from the PWS after 100 kts. No indications at all

However if a PWS warning is detected before 100kts then that warning will continue all the way down the take off roll if necessary with all the associated aural warning.

8che
I correct myself. You are right PWS aural warning calls for reject takeoff.