Primarily for general aviation discussion, but other aviation topics are also welcome.
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By Full Metal Jackass
FLYER Club Member  FLYER Club Member
#1846579
IMCR wrote:Most modern transponders now automatically apply ground mode.


That's what I thought hence I would put the transponder to ALT mode after starting the engine; the transponder is a GTX330 ES; even though the ground speed was set properly to ensure it logged flight time, it was still sufficient to cause a TCAS RA.

I didn't understand it either, still don't, but only put the transponder onto Alt mode after lining up.....
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By Iceman
FLYER Club Member  FLYER Club Member
#1846581
Having been brought up in the pre Mode-S days (read modern transponders), it has always been my lineup action on crossing the hold :- RAPT

Recognition / landing lights on
Anti-collision lights on.
Pitot heater on.
Transponder to Alt.

Iceman 8)
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By T67M
FLYER Club Member  FLYER Club Member
#1846584
Full Metal Jackass wrote:
IMCR wrote:Most modern transponders now automatically apply ground mode.


That's what I thought hence I would put the transponder to ALT mode after starting the engine; the transponder is a GTX330 ES; even though the ground speed was set properly to ensure it logged flight time, it was still sufficient to cause a TCAS RA.


If the pilot pushes the ALT button, the GTX330 immediately goes into flight mode with altitude reporting. Automatic Gnd/Alt switching only works if (and only if) the pilot has NOT manually selected another mode (Off, Sby, On or Alt).
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By Cub
FLYER Club Member  FLYER Club Member
#1846586
TCAS 7.1 progressively inhibits Resolution Advisories (RAs) depending on the height Above Ground Level (AGL) provided by the radio altimeter as follows:

“Increase Descent” RAs are inhibited below 1,550 ft AGL (± 100 ft)

“Descend” RAs are inhibited below 1,100 ft AGL (± 100 ft)

All RAs are inhibited below 1,000 ft AGL (± 100 ft).

If a “Descend” RA is in progress while the aircraft is descending through 1,100 feet AGL, the RA will change to an “Adjust vertical speed” RA.
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By IMCR
#1846589
Full Metal Jackass wrote:
IMCR wrote:Most modern transponders now automatically apply ground mode.


That's what I thought hence I would put the transponder to ALT mode after starting the engine; the transponder is a GTX330 ES; even though the ground speed was set properly to ensure it logged flight time, it was still sufficient to cause a TCAS RA.

I didn't understand it either, still don't, but only put the transponder onto Alt mode after lining up.....


Yes, funnily enough although it might seem counter intuitive, you were defeating the system which rather relies on your doing nothing. A sort of whatever else you do keep the pilot off the controls. :-).
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By IMCR
#1846590
Cub I think this is all very fine, but there is no retrofit update requirement unless I am mistaken (non CAT) so its only if you fit a new txp or its a new aircraft. I doubt either the Cirrus or Metroliner (FAA land) would have been so fitted, and nor will the vast majority of the GA fleet especially at 50 to 80 K a pop. Is there any purely software update available? I am guessing not.
Last edited by IMCR on Wed May 12, 2021 11:10 pm, edited 1 time in total.
By IMCR
#1846593
Yes it does, as I speculated earlier (and it isnt crystal clear) looks like the U/C is gone. They were very lucky maybe pulled up a bit at the last moment so the prop and wings didn't pile in. Doesn't bare thinking about just how lucky they got.
By Ibra
#1846599
Josh wrote:The SR22 was in the visual circuit, not on a visual approach. Lining up on the incorrect parallel runway is pretty bad juju and if your SA is low enough for you to be doing so and miss the traffic called to you by ATC I’m not sure any electronic aid will help.

I doubt there were any advisories either in this case (making assumptions about height agl given the positions of the collision) - TCAS has all sorts of sensible inhibitions that kick in as you approach the ground. On some specific parallel approach procedures (not this one) US operators are authorised to disable TCAS manoeuvre commands. Also not uncommon for light GA and heavy metal to be separated legally by US standards but close enough to set off a TCAS RA.


I just got mislead on 180mph comment from one witness somewhere (most likely in IFR visual joins), not sure it it's true, but 160kts is not a good speed for visual circuit?
By A4 Pacific
#1846603
All RAs are inhibited below 1,000 ft AGL (± 100 ft).


Alleluia!

Somebody here actually seems to know what they are talking about!

The cause of this near multiple fatal appears crystal clear. Nothing is likely to save anyone who’s a total d1@khe@d!

Runways 17L and 17R are VERY closely spaced parallel runways! Just another (frequent!) hazard of operating in the Wild West to add to all the others!! :roll:
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By Cub
FLYER Club Member  FLYER Club Member
#1846607
IMCR wrote:Cub I think this is all very fine, but there is no retrofit update requirement unless I am mistaken (non CAT) so its only if you fit a new txp or its a new aircraft. I doubt either the Cirrus or Metroliner (FAA land) would have been so fitted, and nor will the vast majority of the GA fleet especially at 50 to 80 K a pop. Is there any purely software update available? I am guessing not.


Do you know if either aircraft was equipped with TCAS? If either had TCAS fitted, it is extremely likely they would be operating to 7.1. It has been around a long time now.
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By Full Metal Jackass
FLYER Club Member  FLYER Club Member
#1846609
Cub wrote:Do you know if either aircraft was equipped with TCAS? If either had TCAS fitted, it is extremely likely they would be operating to 7.1. It has been around a long time now.


The Cirrus would not have had TCAS but some sort of TAS based on ADS-B. The Metroliner would have had TCAS fitted of some sorts but bearing in mind the age of the aircraft - it was 43 years old - and the fact it wasn't flying in RVSM airspace, it could have still been using version 6.04a, if it was installed pre Jan 1 2005, or version 7.0 if installed later.
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By Cub
FLYER Club Member  FLYER Club Member
#1846610
Full Metal Jackass wrote:
Cub wrote:Do you know if either aircraft was equipped with TCAS? If either had TCAS fitted, it is extremely likely they would be operating to 7.1. It has been around a long time now.


The Cirrus would not have had TCAS but some sort of TAS based on ADS-B. The Metroliner would have had TCAS fitted of some sorts but bearing in mind the age of the aircraft - it was 43 years old - and the fact it wasn't flying in RVSM airspace, it could have still been using version 6.04a, if it was installed pre Jan 1 2005, or version 7.0 if installed later.


I am sure we will discover when the investigation report is published.

Remind me. Did 6.04a or 7.0 suppress RAs below 1,000ft AGL?
By johnm
FLYER Club Member  FLYER Club Member
#1846612
EC completely irrelevant to this my guess is that the Cirrus pilot was transferring from a slower aircraft and simply got behind.
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