Egpws?

[lazyeye]

Just wondering if EGPWS gives windshear warning at all altitudes or only below 2500agl? Please help.....

[Capt Fathom]

EGPWS has nothing to do with windshear warning systems. Windshear warning systems were available with GPWS systems 10 - 15 years ago.

The major benefit of EGPWS is the terrain database which is included to enhance the terrain warning capabilities.
The Windshear Warning System is still a part of the whole package.

[Reverseflowkeroburna]

For the benefit of the lesser informed amongst us....................

How exactly does EGPWS provide for timely windshear warnings anyway????

Airport-based systems in the US use doppler radar, and I'm guessing that would be rather cost-prohibitive for GA types.

Is it a reactive type of alert that utilises significant changes in velocity as determined by the GPS??????:hmm:

[404 Titan]

I think some are confused as to what EGPWS is. It stands for Enhanced Ground Proximity Warning System. Windshear detection and Predictive Windshear detection is not provided by this system.

EGPWS like GPWS provides alerts if the ground is getting to close or your rate of closure with the ground is unsafe given your current configuration or phase of flight. The only difference with EGPWS is it uses GPS and a terrain database to give a more advanced warning of terrain than is possible with GPWS and using RADALT.

Windshear detection uses airspeed trend to give windshear detection. Predictive windshear detection combines this with what the weather radar sees to give an advanced warning of possible windshear.

[404 Titan]

Ibex

That may be the case with the Honeywell system but the system used in the A330/340 has nothing to do with the EGPWS. The reactive windshear warning is displayed when the Flight Management Guidance Computer detects current windshear parameters. The Predictive windshear system is a function of the weather radar and looks out to five miles in front of the aircraft using Doppler radar to detect windshear ahead. The EGPWS on the A330/340 only has 5 basic modes plus the Terrain Awareness Display (TAD) and Terrain Clearance Floor (TCF) modes.

[Ace on Base]

I have been putting a fair bit of time studying these types of topics of late, and this is what I have been able to dig up. By no means am I saying this is gospel, but it may be along the correct track. Someone may have a better idea on this subject than the guy that wrote this info that I have been reading.

GPWS

This is essentially a central computer system that receives various data inputs, these are:
1) Excessive barometric rate of descent
2) Radio Altimeter (height/altitude)
3) Flap and Gear position (configuration)
4) ILS glide slope deviation.
5) Approach Minima
6) Throttle position

From these inputs it then calculates if any of the following dangerous or potentially dangerous circumstance exists:
1) Excessive barometric rate of descent
2) Excessive terrain closure
3) Height loss after takeoff
4) Flaps or gear not selected for landing
5) Too low on the ILS glide slope
6) Descent below approach minima.

These circumstances form the six main working modes for GPWS, these modes are:
1) Mode 1: Excessive barometric rate of descent
2) Mode 2: Terrain closure
3) Mode 3: Sinking flight path after takeoff or go-around
4) Mode 4: Flaps or gear not selected
5) Mode 5: ILS glide slope deviation
6) Mode 6: Approach Minimums

Now, regarding windshear, windshear is not a GPWS mode, but an entirely separate system. However sometimes it is “classified” as a GPWS mode because it uses the GPWS flight crew visual and aural warning system.

Windshear warnings are provided by using Air-data computer detected changes in airspeed to calculate the presents of a windshear phenomenon, which feeds into the GPWS, which generates a “windshear, windshear” aural and visual display on the main Attitude Directional Indicator. Windshear warnings are active from ground level to 1500 feet.

I hope that has answered the question!!

Now, a question from me:

Is EGPWS more favorable to have on an ILS or a VOR approach?

A) This has been bothering me for a while. Whilst it is true to say that the (E)GPWS has glide slope deviation and this works automatically on glide slope capture, an ILS is a precision approach, and the pilot flying should be scanning his ADI, the warning should really be a backup. Under the ICAO standards there is a fair bit of “Fat” built into this type of approach for protection.

B) However, The VOR approach is a NON PRECISION APPROACH, wouldn’t it be more useful to have the (E)GPWS back up an approach of this type?? Particularly with terrain mapping / terrain closure, as well as MDA Set on the Radio (GPWS) / Radar (EGPWS) altimeter?

I have a sneaky suspicion that it is answer A, but cannot rule out answer B. And as I have not had the pleasure of flying something that big that has either GPWS, or EGPWS, I cannot rely on any experience from myself – so I put the question out to those that have the benefit of experience!!

[Capt Fathom]

How many times do I have to say it?!!!!!!!
We've heard you Ibex, but you are the only one saying it ! :{

[Ace on Base]

IBEX

By no means am I saying this is gospel, but it may be along the correct track. Someone may have a better idea on this subject than the guy that wrote this info that I have been reading.

So, maybe I should have gone into the operation of EGWPS a little further, Maybe re-titled my post. As there seemed to be some confusion on the modes of operation and windshear being one of these, My intention was to simply try and clear some of the ambiguity about windshear......... So spank me and call me MARTHA!!!!!!:{

If you are as knowledgable as you proclaim, how about the challenge of answering the question that I had posted, rather than being a complete tw@t, and sticking it into someone that has no experience on the gear, that has simply studied the information, and isnt a self proclaimed know-it-all!:} :}

And just to satisfy IBEX, here it is...... EGPWS:ok:

EGPWS, like the rest of aviation is full of acronyms, stands for ENHANCED GROUND PROXIMITY WARNING SYSTEM

Initially this system was suitable only to aircraft with digital avionics, although there is current research to develope an analogue aircraft version. EGPWS provides greater levels of detection than a standard GPWS, some of the additional features that are an advantage over GPWS are Terrain Mapping - this can be overlaid on navigation display by using the weather system. Probable windshear visual and aural warnings can be generated to warn of the impending possibillity of encountering shear ahead. These warnings are derived from the EGPWS computer once it has recieved data from the stall warning computer after it processes angle of attack, and sensitive acceleration imputs from the INS.

There is a further bunch of stuff that I recall reading, I just cant place it at the moment. This included something along the lines of the terrain mapping is not a feature of the RADAR Altimeter (different in operation to the RADIO ALTIMETER used in GPWS I may add for IBEX's sake), however is derived from a data bank of the terrain world wide - some astronomical amount of data like 95% of the entire land mass's of the world are stored in it. But, as I said, I cant put my hands on it so it is not a credible source of information and most probably incorrect - just ramblings from a tired fool. If I find it, I will add to my post........... Unless IBEX is over his spat of simply shooting people down, and has some constructive input into this information / topic, maybe he / she could draw on the great depths of knowledge of his and inform the rest of us fools. :E

[Capt Fathom]

The aircraft I flew had the GPS embedded in the EGPWS. The GPS however, was not accessible and not available to the FMS for navigation.

captain marvellous,
(so many captains around here!) I would have thought the GPS was needed to compliment the accuracy of the terrain database, or do some systems just use the IRS.

[Ace on Base]

IBEX,

OK, Appology Accepted!:ok: :ok:

Now, Perhaps you could enlighten me on my question regarding (E)GPWS on an ILS, or a VOR (NPA), which one is more preferable?. Perhaps re-read the question in my last post.

Anyone else care to help me out? :confused:

[404 Titan]

Ibex

After doing a little research I have discovered that on B777 and B744 (B742 with EGPWS), windshear detection is part of the GPWS or EGPWS unit. On the Airbus A330 and A340 though, and I suspect other FBW Airbus aircraft, windshear and windshear ahead are not part of the EGPWS or GPWS unit. They only have an input into the EGPWS or GPWS computers via the FW computers and/or the PWS computers to inhibit modes 1-5 if windshear is detected. The reason for this is that windshear or windshear ahead warnings have priority over EGPWS or GPWS warnings. Maybe when discussing this type of thing we should all realize that different aircraft manufactures have different philosophies to the same problems and that what applies to one aircraft maker doesn’t necessary apply to the other. Do you get my drift Ibex? :ok: