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Gpws  
User currently offlineBAe146QT From United Kingdom, joined Sep 2006, 996 posts, RR: 0
Posted (7 years 10 months 3 days ago) and read 3076 times:

After posting on the 747-8 thread, it occurred to me that it would be difficult to misjudge your height above the tarmac since the GPWS would be calling out at you.

Which leads me to my question.

In a recent thread, it was said that TCAS should not be relied upon as a primary flight tool since, if it is alerting you, someone somewhere has really screwed up and you had better act quickly. It's a last-ditch safety net, in other words.

Do you hold the same view of GPWS? When landing, I assume that you're mostly looking at the altimeter, the VSI, and out the window. Do you regularly use the GPWS to augment your picture of the world, or is it something you only pay attention to in, say, heavy IMC conditions like fog?


Todos mis dominós son totalmente pegajosos
37 replies: All unread, showing first 25:
 
User currently offlineMeister808 From United States of America, joined Jan 2000, 973 posts, RR: 1
Reply 1, posted (7 years 10 months 3 days ago) and read 3069 times:

I can't imagine why or how anyone would use either TCAS or GPWS to fly the plane. They are alert systems, and are designed to warn the pilot of something going wrong. While both may be handy ways to help the flight crew maintain situational awareness, there isn't really any way to use either system as a primary source of information when flying the aircraft, nor should there be.

-Meister



Twin Cessna 812 Victor, Minneapolis Center, we observe your operation in the immediate vicinity of extreme precipitation
User currently offlineBAe146QT From United Kingdom, joined Sep 2006, 996 posts, RR: 0
Reply 2, posted (7 years 10 months 3 days ago) and read 3061 times:

Quoting Meister808 (Reply 1):
there isn't really any way to use either system as a primary source of information when flying the aircraft, nor should there be.

I didn't think so, but I wondered whether anyone makes use of the information since it's there anyway. After all, the altitude callouts aren't delivered in an urgent tone, (not that I've ever heard, anyway), so it was reasonable to wonder whether they were there to augment the pilot's picture of the world.

On reflection it would seem that they're probably there to prevent the sort of thing that happened to that Eastern L1011 in the 'Glades.



Todos mis dominós son totalmente pegajosos
User currently offlineCharlienorth From United States of America, joined Jun 2006, 1122 posts, RR: 4
Reply 3, posted (7 years 10 months 2 days 23 hours ago) and read 3061 times:

On some aircraft the GPWS computer provides the automated callouts ..."300ft,200ft,100ft...retard..retard..retard..,some airlines used "TCAS Trail",don't know enough about it,assume it's a distance reference between aircraft,maybe one of our pilots can explain it better.

User currently onlinePihero From France, joined Jan 2005, 4445 posts, RR: 76
Reply 4, posted (7 years 10 months 2 days 23 hours ago) and read 3060 times:
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Quoting BAe146QT (Thread starter):
it occurred to me that it would be difficult to misjudge your height above the tarmac since the GPWS would be calling out at you.

NO, it wouldn't. Coming close to the ground with a landing configuration - flaps and gear - would be recognised by the GPWS as a normal situation, hence no warning will occur.
Your best height info would come from the altimeter, and the radio altimeter while coming close to the runway. On modern airliners, there's a voice call-out every 10 feet or so, allowing you to get a better rhythm on your flare.

Quoting BAe146QT (Thread starter):
it was said that TCAS should not be relied upon as a primary flight tool since, if it is alerting you, someone somewhere has really screwed up and you had better act quickly. It's a last-ditch safety net, in other words

Actually, TCas displays the traffic around you, giving you a better SA. What you should not do is to try and try your own avoidance manoeuvre on the horizontal plane with the TCas information. The close-by traffics are displayed on your nav screen as a diamond with its relative height to your own aircraft. When one comes closer, the diamond turns to white, then becomes a yellow circle with "traffic, Traffic !" voice call. If there is an impending conflict, the yellow becomes red and the resolution command will appear on your screen and the voice resolution command will sound (basically climb or descend, an increase option and a "monitor" possibility.

Quoting BAe146QT (Thread starter):
When landing, I assume that you're mostly looking at the altimeter, the VSI, and out the window. Do you regularly use the GPWS to augment your picture of the world, or is it something you only pay attention to in, say, heavy IMC conditions like fog?

Don't forget approach and final areas are altitude protected. In side these areas, just respect the vertical path. Of course in mountainous regions, I'd have one ND on terrain display while I'm descending toward an approach pattern. Same with a takeoff and climb out of relief. One is never completely sure !
Hope it answers your questions,

Regards



Contrail designer
User currently offlineAvt007 From Canada, joined Jul 2000, 2132 posts, RR: 5
Reply 5, posted (7 years 10 months 2 days 21 hours ago) and read 3018 times:

The sole purpose of the altitude call outs is to help the pilot during the final phase of his approach. It is in no way a warning from the system. It is optional and can be selected by strapping when the system is installed.

User currently offline3DPlanes From United States of America, joined Apr 2006, 167 posts, RR: 0
Reply 6, posted (7 years 10 months 2 days 18 hours ago) and read 2989 times:

Bearing in mind that I'm just a lowly spam can driver, I think the confusion lies in mixing up GPWS and Rad Alt...

To my knowledge, GPWS gives warnings like "Terrain!" and "Pull Up!" or "Sink Rate!" to keep you from flying into a hill. Or descending into a swamp, a la Eastern as mentioned above.

Getting a "50... 40... 30..." type callout as you approach that mountain peak would certainly get your attention, but would likely be too late to provide any room for avoiding the crash.

Those callouts are *meant* to be used during landing, unlike the original premise of utilizing a warning system like GPWS for "extra info."



"Simplicate and add lightness." - Ed Heinemann
User currently onlinePihero From France, joined Jan 2005, 4445 posts, RR: 76
Reply 7, posted (7 years 10 months 2 days 14 hours ago) and read 2963 times:
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Quoting 3DPlanes (Reply 6):
Bearing in mind that I'm just a lowly spam can driver, I think the confusion lies in mixing up GPWS and Rad Alt...

 thumbsup 
I agree with all your post, except the self-depreciating bit. I, as a professional (and probably blinkered by my trade) did not see that confusion.

Regards



Contrail designer
User currently offlineBAe146QT From United Kingdom, joined Sep 2006, 996 posts, RR: 0
Reply 8, posted (7 years 10 months 2 days 14 hours ago) and read 2961 times:

Excellent stuff. Thank you for the responses and thank you, 3DPlanes for the clarification.


Todos mis dominós son totalmente pegajosos
User currently offlineCosmicCruiser From United States of America, joined Feb 2005, 2255 posts, RR: 15
Reply 9, posted (7 years 10 months 2 days 11 hours ago) and read 2935 times:

Quoting 3DPlanes (Reply 6):
Getting a "50... 40... 30..." type callout as you approach that mountain peak would certainly get your attention, but would likely be too late to provide any room for avoiding the crash.

You won't get 50,40,30,etc from app. a mtn from GPWS. All you'll hear is "whoop, whoop pull up terrain.."

CAWS gives the rad alt callout on landing.


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17039 posts, RR: 66
Reply 10, posted (7 years 10 months 2 days 8 hours ago) and read 2909 times:

Quoting 3DPlanes (Reply 6):
To my knowledge, GPWS gives warnings like "Terrain!" and "Pull Up!" or "Sink Rate!" to keep you from flying into a hill. Or descending into a swamp, a la Eastern as mentioned above.

Getting a "50... 40... 30..." type callout as you approach that mountain peak would certainly get your attention, but would likely be too late to provide any room for avoiding the crash.

Isn't the latter what happened to the NZ DC-10 in Antarctica? They got the warning and crash. Not that it was a cause, just a symptom.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineDH106 From United Kingdom, joined Jun 2005, 626 posts, RR: 1
Reply 11, posted (7 years 10 months 2 days 8 hours ago) and read 2896 times:

Quoting Starlionblue (Reply 10):
Isn't the latter what happened to the NZ DC-10 in Antarctica? They got the warning and crash. Not that it was a cause, just a symptom

They got the "Terrain, Pull Up, Pull Up" GPWS warning, but unfortunately because of the specific shape of the lower slope of Mt. Erebus they received only about a 6 sec. warning - clearly too late for a large airliner.



...I watched c-beams glitter in the dark near the Tanhauser Gate....
User currently offlineBio15 From Colombia, joined Mar 2001, 1089 posts, RR: 7
Reply 12, posted (7 years 10 months 2 days 7 hours ago) and read 2886 times:

Quoting BAe146QT (Thread starter):
When landing, I assume that you're mostly looking at the altimeter, the VSI, and out the window

On an ILS approach without the runway in sight eyes are mostly set on the LOC/GS indication and the airspeed indicator. During the landing the GPWS gives height callouts, not the warnings.

Quoting DH106 (Reply 11):
They got the "Terrain, Pull Up, Pull Up" GPWS warning, but unfortunately because of the specific shape of the lower slope of Mt. Erebus they received only about a 6 sec. warning

That's the main disadvantage of the GPWS. The terrain proximity identification relies on the height of the aircraft which is measured vertically down; it uses information from the radio altimeter. This meaning that if you head towards a vertical wall you probably won't even get a warning. The EGPWS (Enhanced GPWS) has an additional information source which is a worldwide terrain database. With EGPWS you can get a warning if your path is in course of collision with terrain, even if the ground proximity computer has not yet identified the threat based on radio altimeter input.


Alfredo


User currently offlinePhilsquares From , joined Dec 1969, posts, RR:
Reply 13, posted (7 years 10 months 2 days 6 hours ago) and read 2865 times:

Quoting Bio15 (Reply 12):
During the landing the GPWS gives height callouts, not the warnings.

The GPWS does not give the callouts. Generally speaking, it's from the radio altimeter. As CosmicCruiser pointed out, the radio altimeter is part of the CAWS (caution and warning system).


User currently offlineCharlienorth From United States of America, joined Jun 2006, 1122 posts, RR: 4
Reply 14, posted (7 years 10 months 2 days 5 hours ago) and read 2856 times:

Quoting Philsquares (Reply 13):
The GPWS does not give the callouts. Generally speaking, it's from the radio altimeter. As CosmicCruiser pointed out, the radio altimeter is part of the CAWS (caution and warning system).

I know for sure it does on the A320,not positive on other types.


User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2556 posts, RR: 24
Reply 15, posted (7 years 10 months 2 days 5 hours ago) and read 2845 times:

Quoting Philsquares (Reply 13):
The GPWS does not give the callouts. Generally speaking, it's from the radio altimeter. As CosmicCruiser pointed out, the radio altimeter is part of the CAWS (caution and warning system).

Sorry, but it is the GPWS/EGPWS that provides the altitude callout audio. The radio altimeter provides it with the information to do so. Radio altimeters do not have audio outputs (although in the old days, before GPWS MkII, there was a rising tone available from the Rad Alt to indicate the last few feet).

Next time you are in the simulator, pull the GPWS C/B and you'll see that the altitude callouts are disabled (as well as GPWS itself, bank angle warnings, windshear alerts, etc).

I'm sure you didn't mean to imply that the Rad Alt is part of CAWS, but that is how your post reads.

[Edited 2006-11-21 19:30:57]

[Edited 2006-11-21 19:38:07]


The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlineTroubleshooter From Germany, joined Feb 2005, 423 posts, RR: 4
Reply 16, posted (7 years 10 months 2 days 3 hours ago) and read 2827 times:

Quoting Charlienorth (Reply 14):
Quoting Philsquares (Reply 13):
The GPWS does not give the callouts. Generally speaking, it's from the radio altimeter. As CosmicCruiser pointed out, the radio altimeter is part of the CAWS (caution and warning system).

I know for sure it does on the A320,not positive on other types.

On the A320 the altitude callouts are generated by the FWC´s (flight warning computer). They receive inputs from the radio altimeter system to do so. The same is valid for the "retard" announcement.

Some interesting infos about (E)GPWS can be found here (check out the videos): http://www.honeywell.com/sites/aero/...C5-3734-3A2F-1939-E2D290ED1616.htm



This job sucks!!! I love this job!!!
User currently offlineRalgha From United States of America, joined Nov 1999, 1614 posts, RR: 6
Reply 17, posted (7 years 10 months 2 days 3 hours ago) and read 2821 times:

Quoting BAe146QT (Thread starter):
In a recent thread, it was said that TCAS should not be relied upon as a primary flight tool since, if it is alerting you, someone somewhere has really screwed up and you had better act quickly. It's a last-ditch safety net, in other words.

It would be hard to utter a statement more false than that one.



09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0
User currently offlineCharlienorth From United States of America, joined Jun 2006, 1122 posts, RR: 4
Reply 18, posted (7 years 10 months 2 days 3 hours ago) and read 2821 times:

Quoting Troubleshooter (Reply 16):

On the A320 the altitude callouts are generated by the FWC´s (flight warning computer). They receive inputs from the radio altimeter system to do so. The same is valid for the "retard" announcement.

Some interesting infos about (E)GPWS can be found here (check out the videos): http://www.honeywell.com/sites/aero/...6.htm

Good Link!! The GPWC does in fact generate the final callouts on final app.,there have been instances of a british accented voice giving call-outs this being corrected by replacement of the GPWC.


User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 19, posted (7 years 10 months 1 day 23 hours ago) and read 2790 times:

Quoting Jetlagged (Reply 15):
'm sure you didn't mean to imply that the Rad Alt is part of CAWS, but that is how your post reads

You're somewhat correct. On the 400 the RA is part of the EGWPS and the CAWS. The RA is used to inhibit the Master Warning light and Fire warning message. It is armed from V1 to 400' RA or 25 seconds after V1.

The EGWPS does provide altitude voice annunciation through the RA and the minimums voice annunciation throught the Capt's RADIO/BARO switch on the EFIS control pane.


User currently offlineEssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 2
Reply 20, posted (7 years 10 months 1 day 18 hours ago) and read 2765 times:

Quoting 3DPlanes (Reply 6):
Bearing in mind that I'm just a lowly spam can driver

What's a spam can?

Quoting Ralgha (Reply 17):
Quoting BAe146QT (Thread starter):
In a recent thread, it was said that TCAS should not be relied upon as a primary flight tool since, if it is alerting you, someone somewhere has really screwed up and you had better act quickly. It's a last-ditch safety net, in other words.

It would be hard to utter a statement more false than that one.

What??? I completely agree with the fact that TCAS is not a primary flight system. It is a safety system... Sure, you can overlay terrain on a display like airports and other data, but it is not something that is used for primary navigation.


User currently offlineBAe146QT From United Kingdom, joined Sep 2006, 996 posts, RR: 0
Reply 21, posted (7 years 10 months 1 day 10 hours ago) and read 2719 times:

Quoting Ralgha:
It would be hard to utter a statement more false than that one.

It's difficult to know what you're objecting to since you didn't qualify your statement. But as I didn't provide an exact quote of that thread, I can see that it may be difficult to infer what the poster meant. My interpretation - which I probably didn't word correctly in my first post - was;

"Don't use TCAS as a replacement for your other senses - like your Mk1 Eyeball - when it comes to maintaining situational awareness. It's there to protect you from your own - and other's - shortcomings."

In other words, would you paint your car's windscreen black and then drive down the I-95 in heavy traffic, while talking on your cellphone, with only a Flensburg RADAR to guide you?



Todos mis dominós son totalmente pegajosos
User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2556 posts, RR: 24
Reply 22, posted (7 years 10 months 1 day 6 hours ago) and read 2698 times:

Quoting PhilSquares (Reply 19):
You're somewhat correct.

Your reply is somewhat correct as well.  Smile

Quoting PhilSquares (Reply 19):
On the 400 the RA is part of the EGWPS and the CAWS. The RA is used to inhibit the Master Warning light and Fire warning message. It is armed from V1 to 400' RA or 25 seconds after V1.

That doesn't make it part of CAWS or EGPWS, it just means it has inputs to CAWS, similarly for EGPWS. An aircraft like the 400 is highly integrated, so it's hard to say what is part of what. Maybe everything is part of the CMC  Smile

The RA is surely a separate unit, not provided as part of central warnings. It has many other functions, including inputs to the autopilot and display to the pilot via the PFD. Traditionally the RA is part of flight instruments, not warnings. However if Boeing now classify it as a warning system on the 400 then fair enough.

Quoting PhilSquares (Reply 19):
The EGWPS does provide altitude voice annunciation through the RA and the minimums voice annunciation throught the Capt's RADIO/BARO switch on the EFIS control pane.

EGPWS provides the annunciation by processing inputs from the RA and the selected DH/MDA. Not through the RA.



The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlineRalgha From United States of America, joined Nov 1999, 1614 posts, RR: 6
Reply 23, posted (7 years 10 months 1 day 5 hours ago) and read 2691 times:

Quoting BAe146QT (Reply 21):
It's there to protect you from your own - and other's - shortcomings.

That's what I'm objecting to. Only part of its purpose is to protect from shortcomings. I have gotten many, many TAs from my TCAS, and not a single one, that I can think of, was because someone screwed up.



09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0
User currently offlineBAe146QT From United Kingdom, joined Sep 2006, 996 posts, RR: 0
Reply 24, posted (7 years 10 months 1 day 4 hours ago) and read 2686 times:

Quoting Ralgha (Reply 23):
That's what I'm objecting to.

I understand. I think the problem is I cannot visualise a situation where two aircraft are in potential danger of colliding without someone having done something wrong.

I'm not making that as an absolute statement - you're a qualified pilot and I'm not, which is why I'm asking how it can happen. To an outsider, the fact of two aircraft being in the same place at the same time can only be attributed to an error by... someone or something.

I really do appreciate your input on this - and I'm not being sarcastic - since you are an instructor and I would (as a trainee) like to know how all this fits together.



Todos mis dominós son totalmente pegajosos
25 Ralgha : Most frequently they are caused by VFR aircraft who may or may not be talking to ATC. There are any number of legitimate reasons, without someone havi
26 EssentialPowr : How did we get from GPWS to TCAS? Both of these are safety systems that operate in the "background", ie not a primary source of flight data (yes, terr
27 BAe146QT : I do believe that was because of Ralgha's reply, no23. Still, show me a thread that doesn't go off-topic at some point. At least we are still talking
28 PhilSquares : Sorry to disagree, but what I quoted was right out of the Vol 2 of the AOM. So, if you disagree, take it up with Boeing.
29 3DPlanes : Essentially, any (metal) aircraft where you can a have birdstrike from the *rear*... In my case a Piper Archer. Exactly so. How about an outsider fly
30 EssentialPowr : WHAT?? NO one has to screw up to have a midair collision? Where or in what are you a captain? Airplanes dont do anything "right" or wrong; people do.
31 Jetlagged : The copy of the 747-400 AOM I have does not list the radio altimeter as part of warnings systems. It's main entry is under Navigation, but there are
32 PhilSquares : What I quoted you was right out of Vol 2 Chapter 15, Warning Systems.
33 Jetlagged : Sorry to resurrect this after so long, but I took a break from the forums for a while so missed this reply. Nothing in this chapter supports your post
34 Zeke : I try to go through life without GPWS calling a alert warning, professional pilots should never get in a situation where GPWS warnings go off, if the
35 Post contains images Avioniker : Gentlemen and ladies; There's really no reason to get heated. You all are speaking from your own experience. May I submit that many of you are saying
36 Jetlagged : I'll admit to being a bit picky on this, but this is Tech Ops, so being accurate is important. Zeke's post says it all, thanks for the excellent summ
37 Pilotaydin : the Boeing predictive windshear works like a charm.... 3 nights ago, a calmnight, we were approaching runway 06 5 miles out, and a heavy crossed our p
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