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Posted

when i turn off radar altimeter gcas fault light turns on and its means gcas doesnt work but i still get the pull up pull up vmu.

 

is it correct to hear that vmu pull up when gsas fault light is on ??

Posted

I think it is, i believe the A10C has a global map whit all elevation data in it.

It knows your current altitude and the altitude of the land there.

If closure rate becomes to big the warning is hearth.

 

At least, that's how i believe it works.

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Posted

yes i think here is a cadc elevation system but what if there is a big building or instalation built on a palce on a map.in that case gsas must relay on radar altimeter instead of cadc elevation.

Posted
yes i think here is a cadc elevation system but what if there is a big building or instalation built on a palce on a map.in that case gsas must relay on radar altimeter instead of cadc elevation.

Nope, Radar altimeter scans straight down from under the fuselage, it does not and can not look ahead and "see" buildings.

 

I think buildings can be put into the elevation data as well, not sure if and how its done though.

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Posted

I'm fairly certain the manual states GCAS will be non-functional if the radar altimeter is turned off.

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Advanced apologies if my post contains typos or missing letters. Many of my posts are typed on a laptop with an old keyboard that has a personality all its own.

Posted

GCAS has several warnings, many of which are at elevations that can be changed to suit the needs of the pilot. Though the terrain elevation is set in the DTC and read that way for terrain collision warnings.

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If you aim for the sky, you will never hit the ground.

Posted

Here's what the manual says:

 

Radar Altimeter. The two position switch labeled RDR ALTM allows you to enable or disable the radar altimeter. If the switch is in the NRM (normal) position, the radar altimeter is functioning and will provide data for GCAS functions. If however the switch is in the DIS (disable) position, the radar altimeter is disabled as well as GCAS functions.
So, when the GCAS is off, there should be no "pull up" warning. Currently, there's a "pull up" audio warning even when GCAS is off. That isn't right, going by the manual and by logic. This evidently is a bug, and I haven't seen anything from E.D. to indicate otherwise.
Posted

I'm sorry but it doesn't make sense to me that an disabled RAD Alt would also disable the Ground Collision and Avoidance System.

 

Sound more like a fault in the manual to me. Then again, i have no maintenance license on the A10C.........

[sIGPIC][/sIGPIC]

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Posted

GCAS functions such as the 90ft Hard Call are disabled when the radar altimeter is off/inoperative.

 

PGCAS, on the other hand, uses DTSAS and continues to function even without the radar altimeter. As such, it is normal to continue to receive the PGCAS Break-X and "PULL UP" VMU messages.

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Posted (edited)
GCAS functions such as the 90ft Hard Call are disabled when the radar altimeter is off/inoperative.

 

PGCAS, on the other hand, uses DTSAS and continues to function even without the radar altimeter. As such, it is normal to continue to receive the PGCAS Break-X and "PULL UP" VMU messages.

 

Btw, you may check what was the last GCAS call source on CDU DTSAS page. See attached pic. Once radar altimeter is off, 'IFFCC PGCAS' and 'IFFCC 90 FT' will never show in this line, and the only possible indication for new GCAS events will be 'DTSAS PGCAS'.

1792275872_DTSASpg.jpg.7aabae81c382d97bd92f336a92cd3405.jpg

Edited by Olgerd
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К чему стадам дары свободы?

Их должно резать или стричь.

Наследство их из рода в роды

Ярмо с гремушками да бич.

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