BAE146QT
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Gpws

Tue Nov 21, 2006 8:16 am

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?
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meister808
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RE: Gpws

Tue Nov 21, 2006 8:42 am

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
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BAE146QT
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RE: Gpws

Tue Nov 21, 2006 8:51 am

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.
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charlienorth
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RE: Gpws

Tue Nov 21, 2006 8:52 am

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.
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Pihero
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RE: Gpws

Tue Nov 21, 2006 8:53 am

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
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avt007
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RE: Gpws

Tue Nov 21, 2006 11:00 am

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.
 
3DPlanes
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RE: Gpws

Tue Nov 21, 2006 2:27 pm

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."
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Pihero
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RE: Gpws

Tue Nov 21, 2006 6:03 pm

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
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BAE146QT
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RE: Gpws

Tue Nov 21, 2006 6:10 pm

Excellent stuff. Thank you for the responses and thank you, 3DPlanes for the clarification.
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CosmicCruiser
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RE: Gpws

Tue Nov 21, 2006 9:22 pm

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.
 
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RE: Gpws

Tue Nov 21, 2006 11:55 pm

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.
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DH106
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RE: Gpws

Wed Nov 22, 2006 12:32 am

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.
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bio15
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RE: Gpws

Wed Nov 22, 2006 1:09 am

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.


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PhilSquares
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RE: Gpws

Wed Nov 22, 2006 2:26 am

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).
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charlienorth
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RE: Gpws

Wed Nov 22, 2006 2:54 am

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.
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Jetlagged
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RE: Gpws

Wed Nov 22, 2006 3:27 am

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]
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troubleshooter
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RE: Gpws

Wed Nov 22, 2006 4:54 am

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
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Ralgha
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RE: Gpws

Wed Nov 22, 2006 5:19 am

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.
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charlienorth
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RE: Gpws

Wed Nov 22, 2006 5:21 am

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.
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PhilSquares
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RE: Gpws

Wed Nov 22, 2006 9:07 am

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.
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EssentialPowr
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RE: Gpws

Wed Nov 22, 2006 2:19 pm

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.
 
BAE146QT
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RE: Gpws

Wed Nov 22, 2006 10:20 pm

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?
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Jetlagged
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RE: Gpws

Thu Nov 23, 2006 2:40 am

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.
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Ralgha
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RE: Gpws

Thu Nov 23, 2006 3:11 am

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.
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BAE146QT
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RE: Gpws

Thu Nov 23, 2006 4:14 am

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.
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Ralgha
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RE: Gpws

Thu Nov 23, 2006 4:31 am

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 having screwed up, for a VFR aircraft to get close enough to cause TCAS to squawk about it. Contrary to popular belief, no one has to screw up to have a mid-air collision. Both airplanes can do everything right and still hit.

Another common situation is when doing parallel visual approaches to close runways, such as at San Francisco. TCAS gets very excited about that, but again, no one has screwed up.

[Edited 2006-11-22 20:33:24]
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EssentialPowr
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RE: Gpws

Thu Nov 23, 2006 4:44 am

How did we get from GPWS to TCAS?

Quoting Ralgha (Reply 23):
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.

Both of these are safety systems that operate in the "background", ie not a primary source of flight data (yes, terrain and the TCAS symbology can be put on the screen if the a/c is so equipped). The purpose of the system(s) is to provide info about avoiding either terra firma or other metal. Whether or not someone "screws up" is the exact issue, which is also why ALPA and most if not all airlines recommend compliance with TA and GPWS in almost all cases. For close parallels, which means visuals, most 10-7 pages recommend inhibiting the RAs.

[Edited 2006-11-22 20:45:48]
 
BAE146QT
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RE: Gpws

Thu Nov 23, 2006 5:07 am

Quoting EssentialPowr (Reply 26):
How did we get from GPWS to TCAS?

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 about secondary safety systems and not "why is the A380/787 overweight?" Count your blessings.

What I have taken away from this thread is;

1) GPWS is a warning system much like TCAS. You don't rely on it in normal situations but you PAY ATTENTION to it.

2) The altitude callouts on approach are either provided by the EGPWS*, CAWS or FWC which in turn gets this information from the radio altimeter, (where is the sensor for this anyway? Between the MLGs?). This may depend on the aircraft though.

3) These callouts are at least occasionally useful.

4) Approach control - as far as the pilot is concerned - relies on Localiser, Glideslope and Airspeed indcations.

Bearing in mind that you pilots out there will be operating all sorts of hardware, have I got this right?



* As I understand it, this is GPWS with a terrain database so it can look forward and predict where you're going.
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PhilSquares
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RE: Gpws

Thu Nov 23, 2006 8:09 am

Quoting Jetlagged (Reply 22):
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

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.
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3DPlanes
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RE: Gpws

Thu Nov 23, 2006 9:09 am

Quoting EssentialPowr (Reply 20):
What's a spam can?

Essentially, any (metal) aircraft where you can a have birdstrike from the *rear*... In my case a Piper Archer.

Quoting Ralgha (Reply 25):
Contrary to popular belief, no one has to screw up to have a mid-air collision. Both airplanes can do everything right and still hit.

Exactly so. How about an outsider flying through a flight school's training area and not monitoring the traffic frequency (not that they'd know to...) They can be doing *everything* 100% perfectly and still have a CFI student spin down into them... Or maybe a LifeFlight helo comes screaming through while you're doing turns around a point...
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EssentialPowr
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RE: Gpws

Thu Nov 23, 2006 3:30 pm

Quoting Ralgha (Reply 25):
for a VFR aircraft to get close enough to cause TCAS to squawk about it. Contrary to popular belief, no one has to screw up to have a mid-air collision. Both airplanes can do everything right and still hit.

WHAT?? NO one has to screw up to have a midair collision? Where or in what are you a captain?

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Jetlagged
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RE: Gpws

Thu Nov 23, 2006 9:01 pm

Quoting PhilSquares (Reply 28):
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.

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 many references to its use by other systems throughout the manual. The things you mention selectively are certainly referenced in Warnings, but radio altimeter is not mentioned as being part of the warnings system. There are many references to RA, but they mostly are with respect to TCAS resolution advisories.

What the AOM does do is specifically mention that GPWS provides the altitude annunciations (but doesn't mention the Rad Alt's part in this).

Finally, CAWS is not mentioned anywhere. That's a McDonnell Douglas acronym for the central aural warning system. The 747-400 aural alerts come from the MAWEA. EICAS acts as the central warning system and controls the Master Warning and Caution lights.

Now I understand that SQ will have it's own customised version of the AOM, but I doubt it would differ hugely in how the systems are classified and grouped together.
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PhilSquares
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RE: Gpws

Thu Nov 23, 2006 9:29 pm

Quoting Jetlagged (Reply 31):
Now I understand that SQ will have it's own customised version of the AOM, but I doubt it would differ hugely in how the systems are classified and grouped together.

What I quoted you was right out of Vol 2 Chapter 15, Warning Systems.
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Jetlagged
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RE: Gpws

Fri Apr 06, 2007 10:31 am

Sorry to resurrect this after so long, but I took a break from the forums for a while so missed this reply.

Quoting PhilSquares (Reply 32):
What I quoted you was right out of Vol 2 Chapter 15, Warning Systems.

Nothing in this chapter supports your posts that the RA provides the altitude callouts. Nor is there anything to say that the RA is a warning system. There are however references in the manual which support my position. For example:

Quote:
Altitude Voice Annunciations During Approach
GPWS provides the following altitude voice annunciations during approach:

• 2,500 feet – TWENTY–FIVE HUNDRED
• 500 feet – FIVE HUNDRED
• 100 feet – ONE HUNDRED
• 50 feet – FIFTY
• 40 feet – FORTY
• 30 feet – THIRTY
• 20 feet – TWENTY
• 10 feet – TEN

The altitude calls will vary according to the airline configuration of course. The manual is clear on where the callouts originate from.

As a technical aside, if you want to change the altitude callout schedule do you make a change to the RA system? No, you change the config strapping on the EGPWS. So the callouts on the 400 originate from the EGPWS.

Quoting PhilSquares (Reply 19):
On the 400 the RA is part of the EGWPS and the CAWS.

How can the RA be "part" of two different systems? What it does, amongst other things, is provide inputs to EGPWS and EICAS (no CAWS on a 400). But it also provides an indication of height above ground on the PFD, surely its primary function and nothing to do with EGPWS or warnings.

Quoting PhilSquares (Reply 28):
So, if you disagree, take it up with Boeing.

With all due respect, I disagree with you, not Boeing. You do not even consider the possiblity that you might be wrong for a change.
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zeke
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RE: Gpws

Fri Apr 06, 2007 11:59 am

Quoting BAe146QT (Thread starter):
Do you regularly use the GPWS to augment your picture of the world

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 they go off, it is a real wake up. Sometimes they are unavoidable like in an engine out situation when ever you have a special engine out escape procedure for terrain.

Quoting BAe146QT (Thread starter):
or is it something you only pay attention to in, say, heavy IMC conditions like fog?

I pay attention to GPWS warnings in any conditions.

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.

Correct, from the 320 series, 330/340 the FWC generates the callouts for 2500, 2000, 1000, 500, 50, 40 30, 20 ,10, 5, HUNDRED ABOVE, and MINIMUM, these are pin programmable, not all airlines have all the callouts (Ref FCOM 1.340.40)

Independent of the FWC the EGPWC also makes callouts for Mark V GWPS modes 1 to 5 and EGPWS functions (TERRAIN AHEAD PULL UP, and TERRAIN AHEAD), it uses RAD ALT 1 as an input.

Quoting Jetlagged (Reply 33):

As a technical aside, if you want to change the altitude callout schedule do you make a change to the RA system? No, you change the config strapping on the EGPWS. So the callouts on the 400 originate from the EGPWS.

On the 737, 744, 757, 767, 777 the Advisory Callouts come from the GPWS mode 6.

Mode 6 is used by GPWS manufacturers for for altitude callouts, selectable 500 foot callouts, bank angle warning, descent below selected minimum radio altitude, tail strike warnings, and on helicopters autorotation callouts, these are "pin programmable", a manufacturer like Boeing would not program the autorotation callouts into the 744, but Honeywell etc have it in their box so the avionics can be used in more than one type of aircraft.

The GPWS modes normally used on the Boeing include :

MODE 1 - Excessive descent rate.
MODE 2 - Excessive terrain closure rate.
MODE 3 - Altitude loss after takeoff or go-around.
MODE 4 - Unsafe terrain clearance when not in the landing configuration.
MODE 5 - Excessive deviation below an ILS glide slope.
MODE 6 - Descent below selected minimum radio altitude, Excessive bank angles and radio altitude
callouts below 100 feet RA.
MODE 7 - Windshear condition encountered (reactive windshear system).


The 777 FCOM says

Quote:
GPWS Callouts

GPWS provides a voice callout at selected radio altitudes to advise the flight crew of the approximate height above ground level. Voice callouts are provided at:
· 100 feet – “ONE HUNDRED”
· 50 feet – “FIFTY”
· 30 feet – “THIRTY”
· 20 feet – “TWENTY”
· 10 feet – “TEN”

The 744 FCOM says

Quote:
"Altitude Voice Annunciations During Approach
GPWS provides the following altitude voice annunciations during approach:
• 100 feet – ONE HUNDRED
• 50feet–FIFTY
• 30 feet – THIRTY
• 10 feet – TEN"

The 737 FCOM says

Quote:

GROUND PROXIMITY WARNING SYSTEM (GPWS)

GENERAL

Ground Proximity Warning System (GPWS) and Enhanced (EGPWS) provide aural and visual warnings, cautions and alerts for potentially hazardous flight conditions involving possible controlled flight into terrain (CFIT).
GPWS uses No. 1 radio altitude, ADC / ADIRU, glide slope and combinations of barometric altitude, airspeed, and aircraft configuration (landing gear lever and flap position).

No. 1 IRS and stall warning computer inputs, BCD - ADIRU /SMYD are required for reactive windshear mode.

EGPWS requires a terrain database correlated with the FMC position and enhance by GPS if installed.

GPWS MODES
MODE 1 - Excessive descent rate.
MODE 2 - Excessive terrain closure rate.
MODE 3 - Altitude loss after takeoff or go-around.
MODE 4 - Unsafe terrain clearance when not in the landing configuration.
MODE 5 - Excessive deviation below an ILS glide slope.
MODE 6 - Descent below selected minimum radio altitude.
MODE 6 - Excessive bank angles and radio altitude callouts below 100 feet RA.
MODE 7 - Windshear condition encountered (reactive windshear system).

Windshear warnings take priority over all other modes. GPWS / EGPWS is armed when all inputs are valid.
The loss of an input signal deactivates only the affected mode(s), however failure of the No. 1 Radio Altimeter causes failure of all GPWS modes.

Aircraft without Enhanced GPWS will not receive indications for flight toward sheer vertical terrain or slow descents toward unprepared terrain while in landing configuration.

ENHANCED GPWS

EGPWS includes all modes 1 through 7. In addition, EGPWS uses a world terrain database that contains detailed information for airport terminal areas and less detailed information between airports. The database is correlated
with FMC position. This enables aural and visual indications for flight toward potential terrain encounters or descent toward any type of terrain while in landing configuration.

EGPWS builds a terrain clearance floor around airports in the database and provides a 3-degree descent path from the final approach fix. Penetration of the terrain clearance floor causes a terrain warning regardless of aircraft configuration, rate of descent, or terrain closure rate.

Man made objects are not contained in the database and terrain clearance floors are not available for non-database airports.

Mode 1 – Excessive Descent Rate

Mode 1 has two boundaries and is independent of aircraft configuration. Penetration of the first boundary sounds the “SINK RATE” alert and illuminates the red PULL UP lights. If the more critical second boundary is entered, the “WHOOP, WHOOP, PULL UP” warning sounds.

Mode 2 – Excessive Terrain Closure Rate

Mode 2 has two sub-modes and is dependent on airspeed, radio and barometric altitude and radio altitude rate of change and configuration. Penetrating the first boundary illuminates the PULL UP lights and generates a twice-repeated
“TERRAIN” followed by repeated “WHOOP, WHOOP, PULL UP” warnings when the second boundary is penetrated.

Mode 2A

If landing gear and flaps are not in the landing position when climbing out of the “WHOOP, WHOOP, PULL UP” envelope, 300 feet of barometric altitude must be gained before the “TERRAIN” warning is silenced.

Mode 2B

If flaps are in the landing configuration when approaching terrain at an unacceptable baro rate, no altitude gain is required to silence the “TERRAIN, TERRAIN” warning. When landing gear or flaps are extended, the altitude gain function is inhibited. When both landing gear and flaps are extended, the “WHOOP, WHOOP, PULL
UP” warning is replaced by the “TERRAIN, TERRAIN” warning.

Mode 3 – Altitude Loss After Takeoff Or Go-Around

Mode 3 is active at low radio altitudes during takeoff or go-around. A “DON’T SINK” alert sounds when accumulated barometric altitude loss equals approximately ten percent of the original radio altitude gained. The alert continues until positive rate of climb is established. If the aircraft descends again before climbing to the initial descent altitude, another alert sounds based on the original descent altitude.

The takeoff mode arms automatically after flaps or landing gear are retracted. Go-around mode is armed when the aircraft descends below 200 feet RA in the landing configuration and either flaps or landing gear are retracted.

Mode 4

Mode 4 has two sub modes and is dependent on radio altitude, airspeed and flap / gear configuration.

Mode 4A – Unsafe Terrain Clearance With Landing Gear Not Down

At airspeeds below approximately 180 knots to 190 knots and below 500 feet RA, a “TOO LOW GEAR” warning is repeated when the gear is not down. As speed increases above approximately 180 knots to 190 knots at any altitude to
1000 RA the “TOO LOW TERRAIN” warning is repeated if the gear is not down.

Mode 4B – Unsafe Terrain Clearance With Flaps Not In A Landing Position

At airspeeds below approximately 150 to 160 knots and below 200 feet RA, the “TOO LOW FLAPS” warning is repeated. As speed increases above approximately 150 knots, the “TOO LOW TERRAIN” is repeated.
The “TOO LOW GEAR” warning takes priority over the “TOO LOW FLAPS” warning.

Mode 5 – Below Glide Slope Deviation Alert

Mode 5 descents below 1.3 dots on ILS glideslope cause a repeated “GLIDESLOPE” alert accompanied by two BELOW G/S lights. If deviation continues, the “GLIDESLOPE” aural gets louder and the repetition rate is
increased. The mode arms when a valid signal is being received by the No. 1 glideslope receiver and the radio altitude is 1000 feet or less.

The mode may be canceled or inhibited by pressing either BELOW G/S light when in the soft warning area.
Modes 1 through 4 aurals have priority over Mode 5 aurals; however, both PULL UP and BELOW G/S lights may illuminate simultaneously.

Mode 6 – Voice Alerts

Mode 6 is available from 1000 feet RA to 50 feet RA (301 – 332), 10 feet RA with the landing gear down. When the “bug” is set in the No. 1 radio altimeter, “MINIMUMS, MINIMUMS” sounds when the “bug” RA is reached.

All other GPWS aurals have priority over the radio altitude aural callouts. All decision height callouts are inhibited for positive decision height settings less than or equal to ten feet.

Mode 6 alerts sounds “BANK ANGLE, BANK ANGLE” at 35, 40, and 45degrees of bank; and “ONE HUNDRED,” “FIFTY,” THIRTY,” “TWENTY,” “TEN” AGL as the aircraft descends for landing. The accuracy of this warning is degraded by irregular approach terrain.

Mode 7 - Reactive Windshear Warning

The reactive windshear warning occurs after penetration of the windshear area if engaged in TOGA and provides flight director recovery guidance.

A red WINDSHEAR annunciation appears on the EADIs and is accompanied by a siren followed and once sounded “WINDSHEAR, WINDSHEAR, WINDSHEAR.” The annunciation remains until the aircraft is flown out of windshear condition.

Windshear warnings take priority over all other GPWS modes.

A windshear condition is detected using comparisons of angle-of-attack, IRS accelerations, and air data computer airspeed or ADIRU, SMYD as installed. The windshear intensity which activates a warning is dependent upon flap position, radio altitude, and phase of flight (takeoff or approach). Warnings occur below 1500 feet RA and during takeoff, at rotation. If using the autopilot, autothrottle, and/or flight director during a windshear encounter, normal TO/GA functions are available.
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avioniker
Posts: 1100
Joined: Tue Jan 01, 2002 5:38 am

RE: Gpws

Fri Apr 06, 2007 9:46 pm

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 the exact same thing with different words?

Example: CAWS: Central Aural Warning System (McDonnell Douglas), Caution And Warning System (Lockheed, and many airlines and military applications)

With the retirement of untold numbers of "graybeards" and the introduction to middle and senior engineering management of many testosterone infested young bucks pushing to make their mark on the industry, all control of standardization and uniformity has gone out the window.

It's time to reintroduce a document like the Collins Glossary (that used to be a mandatory refenence) so that when someone says ATC you know what they're talking about (According to the FAA it's Air Traffic Control, at the Rockwell Collins BRS division it's Automatic Trim Control). (On a more technical note TSE: Total System Error [an autopilot term in use for over 50 years] however Rockwell Collins now has redesignated it as Touch Screen Equipment.)

If you go from the MD-11 to the A320 to the B717 and the MD10 you have four completely different sets of acronyms and abbreviations even though the avionics suites are very close to identical in design and application. In the case of the B717 and the MD10 they are identical right down to the VIA's.

If we, as technical experts, start to insist on uniformity and standardization in naming conventions it will be a start in the right direction.

We've come right back to the 40's and 50's when the ATA standards were proposed to remedy exactly this situation.
I'll climb back down from my soap box now; Comments?
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One may educate the ignorance from the unknowing but stupid is forever. Boswell; ca: 1533
 
User avatar
Jetlagged
Posts: 2564
Joined: Sun Jan 23, 2005 3:00 pm

RE: Gpws

Mon Apr 09, 2007 2:16 am

Quoting Avioniker (Reply 35):
May I submit that many of you are saying the exact same thing with different words?

Example: CAWS: Central Aural Warning System (McDonnell Douglas), Caution And Warning System (Lockheed, and many airlines and military applications)

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 summary.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
pilotaydin
Posts: 2099
Joined: Tue Sep 07, 2004 12:30 am

RE: Gpws

Mon Apr 09, 2007 3:18 am

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 path landing 36R, and as i was coming in at 200 feet, the plane screamed...WINDSHEAR AHEAD go around.....all flight indications and instruments were normal, so i continued my landing......

later on it turned out that it picked up the vortex of the heavy that landed across our path....i was impressed!!
The only time there is too much fuel onboard, is when you're on fire!

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