Terrain Avoidance Technology Question

[Badmachine]

Does terrain avoidance technology account for large man-made structures, such as a very tall building or other structure?

Any available reference information?

Thanx.

[Rainboe]

No. It uses radar altimeter signals which radiate almost vertically. Some of the latest visual cross section systems may have this protection, but only the latest. So cliffs and very steep terrain would be hazardous.

[karlk]

i believe in the a320 the EGPWS only takes into account natural terrain not man made structures. so its always important to watch out for those tall buildings in large cities. hope that helps

karl

[kijangnim]

Greetings

The radio altimeter is used as a "blind man stick" to consolidate the alitude (true altitude) as the last safety net in case of predictive (TAWS) and to give a height in order to compute is the aircraft is in the envelop in the case of reactive (GPWS)
Man made obstacles are incorporated in some database in the US, the biggest demand is coming from helicopters and Biz Jet.

[ahramin]

I have yet to come across a TAWS system which does not have all >=300 foot North American obstacles in it's database. Not sure about European obstacles.

[Denti]

Man made obstacles are normally included in the EGPWS database nowadays, however there allways can be some new ones which aren't yet in the dabase, so better look out. Especially in areasy where wind energy parks pop up faster than anybody can look.

[Bitburger]

The real question

Does GPWS terrain account for ISA - 15 C° or lower ?

[PEI_3721]

“Does terrain avoidance technology account for large man-made structures, such as a very tall building or other structure”?
Enhanced GPWS (EGPWS) does:
General Information – EGPWS Safety Examples/obstacle alerting – download.

Database – EGPWS Database Accessories/obstacle database – download.

… and it works … Celebrating TAWS ‘Saves’: But lessons still to be learnt. See incident #5.
Badmachine - Las Vegas, NV; also note incident #8.
Karlk, see incident #3 (India), and follow the advice re incident #5, fit the obstacle database – IIRC its free!

“Does GPWS terrain account for ISA - 15 C° or lower”?
Enhanced GPWS (EGPWS) provides non standard atmosphere correction when fitted with geometric altitude; this implies fitting the internal GPS receiver which is the better option for navigational aspects of the system’s terrain database (no map-slip).

General Information - EGPWS General Information/EGPWS Features – download.

[EMIT]

Terrain Terrain

Bitburger

E-GPWS accounts for terrain from a database: TAWS altitudes are based on "real" altitudes, feet from sea level. All corrections to altimeters, pressure and temperature related, have to be applied by the pilot(s).

As far as the people are concerned who write about the radar altimeter looking straight down - yes, that is valid for old fashioned GPWS. E-GPWS on the other hand works with a GPS receiver that supplies position, a database that supplies terrain around position and hence a warning system that can supply look-ahead warning of terrain.

Whether man made structures are included in the database - simply said, that depends on the database - consult your company's instructions for the latest truth in that matter (yes, the truth changes every day).

Edit: added third paragraph as an afterthought.

[FE Hoppy]

Honeywell Epic system includes obstacle data and used geometric altitude.

[safetypee]

See ‘Indispensable Upgrades’ - ASW Aug 08 for a well structured paper by Don Bateman reminding operators of the need to ensure that EGPWS software and database revisions are up to date. This also confirms that the ‘Peaks’ and 'Obstacle’ modes are a simple wire change – no cost upgrade.
Database info is available from EGPWS - database.

It might be worth asking maintenance about the mod state of your aircraft, both the software version and the database validity.
If anyone does not have the obstacle mode enabled then see the third link in #8.

[Spooky 2]

The Honeywell EGPWS offers both "peaks" and "obstacles" as seperate options. Hope that answers your question.

[kijangnim]

Greetings

Peaks mode is more an Enroute function, whereas Obstacle is more a TMA function

[safetypee]

kijangnim “Peaks mode is more an Enroute function, whereas Obstacle is more a TMA function”
Yes, or alternatively:
Peaks mode is threat avoidance (planning) and obstacle mode is error recovery (as for terrain modes)
EGPWS may likened to a threat and error detector, and an error avoidance/recovery instrument, thus from either view there are good arguments for displaying terrain (peaks) when planning (briefing) and flying all departures and arrivals.

PEI_3721 Re non standard atmosphere correction (#8). As I understand, EGPWS uses geometric altitude within the warning logic to provide ‘corrected’ warnings, maintaining the integrity of the ‘error detector/recovery’ system. However, EGPWS does not correct any of the normal altimeters etc; this is still a crew responsibility. This is particularly important with FMS/VNAV approaches, for which the majority are based on pressure altitude.
EGPWS may provide a display of geometric altitude (“true altitude”) depending on certification rules/installations. Also some systems may have an altimeter comparator alert when pressure and geometric differ by a certain value – another, much needed error detector function well before any terrain alert/warning.

[HAWK21M]

Unless the revised EGPWS data base has it included....Only natural terrain is present.

regds
MEL

[safetypee]

HAWK21M, if the above represents the mod state of your aircraft, then why not propose to management that the new modes “can be enabled on any EGPWS unit by changing a jumper wire on the unit to enable display of the highest terrain value ahead of the aircraft, display obstacles, and provide aural and visual warnings for a possible flight path into a tower or obstacle higher than 30 m (98 ft) above terrain” (quote from the link in #11).

This change also requires updating the database to include obstacles; usually done regularly?
See the note about incidents in India - link #8.