JohnJ
Topic Author
Posts: 1362
Joined: Tue Jun 27, 2000 5:01 am

How Common Is A TCAS Warning?

Sun Jul 21, 2013 3:33 pm

I was on a CRJ flight from DCA to BUF Thursday - bad weather in DCA had delayed the flight, then we had to get a re-route out of DCA due to thunderstorms blocking our original path to Buffalo. About midway through the flight, the plane did a fairly aggressive descent - nothing too abrupt, but enough to put my heart in my mouth and make me take notice. A few minutes later we ascended. I figured we were avoiding a thunderstorm as there were some ominous clouds outside and didn't think too much further of the incident.

The captain came on the intercom later in the flight and explained that "you may have noticed that we quickly descended a few minutes ago then went back up. We got a warning in the cockpit of being too close to another plane. We received instructions to descend, while the other plane would have received instructions to go up. Sorry for any problems this may have caused." I got the impression he meant a TCAS warning vs. instructions from ATC to descend.

Here's the FlightAware track log - looks like what I describe happened around 8:58. How common is this?

http://flightaware.com/live/flight/A.../20130718/2300Z/KDCA/KBUF/tracklog
 
26point2
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How Common Is A TCAS Warning?

Sun Jul 21, 2013 3:55 pm

Not common.

Usually a TCAS RA (Resolution Advisory) such as this would be caused by nearby VFR traffic the controller may or may not be talking to but I see you were at FL240 so this one is quite unusual and I imagine the controller had some explaining to do to his supervisor.

TCAS calculates rate of closure to determine potential conflict. Looks like your aircraft was level but if the conflict traffic was climbing or descending at a rapid rate toward you the TCAS doesn't anticipate a level-off and might trigger an RA. Pilots are trained to maintain maximum 1000fpm ascent/descent rate the last 1000' to avoid this but clearly some don't follow this guidance.

TCAS RA avoidance is made by flight director pitch changes only (at the moment) and it is an aggressive pitch maneuver by design. The maneuver is hand-flown. If the pilot can see the conflict out the window he can dampen the pitch change but pilots are trained to follow the command bars passenger comfort be damned.

To qualify...I am a corporate pilot who flies about 350 per year and have had 1 RA in the past 10 years. That was departing the Denver area.

[Edited 2013-07-21 08:59:41]

[Edited 2013-07-21 09:05:27]
 
Boeing77W
Posts: 171
Joined: Tue May 15, 2007 6:27 am

How Common Is A TCAS Warning?

Sun Jul 21, 2013 6:13 pm

I've got around 1800 hours flying commercially and never had an RA. I've had one or two TA (Traffic Advisory) and also a couple of instances where the controller has issued immediate changes of heading to prevent a conflict.

Quoting 26point2 (Reply 1):
TCAS RA avoidance is made by flight director pitch changes only

It depends on aircraft type. The 737NG doesn't provide any Flight Director guidance. On receipt of an RA the pilot has to ignore the FD and pitch to an area outside of the red trapeze that appears on the PFD.

[Edited 2013-07-21 11:14:40]
 
freeze3192
Posts: 142
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How Common Is A TCAS Warning?

Sun Jul 21, 2013 10:03 pm

I've been flying 121 for about a year and a half, and I have about 1200 hours in 121 thus far. I've had at least 10 RA's in that time. Many were just the "monitor vertical speed" type RAs, but I'd say just under half were actual RA's where we were required to climb or descend.

The differentiating factor between me and the other pilots above is that I fly a turboprop, down low, in to and out of some of the busiest airports in the world. Couple that with 6 legs a day, up to 8 hours of flying and the RA's are bound to add up.
"A passenger bets his life that his pilot is a worthy heir to an ancient tradition of excellence and professionalism."
 
Viscount724
Posts: 18850
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How Common Is A TCAS Warning?

Sun Jul 21, 2013 10:31 pm

Quoting 26point2 (Reply 1):
Not common.
Quoting freeze3192 (Reply 3):
I've been flying 121 for about a year and a half, and I have about 1200 hours in 121 thus far. I've had at least 10 RA's in that time. Many were just the "monitor vertical speed" type RAs, but I'd say just under half were actual RA's where we were required to climb or descend.

There are usually a few TCAS items every day in the Transport Canada daily occurrence reports, about 50 since June 1. A few random recent examples. Dozens of others similar to these.

A Jazz Aviation DHC-8-102 (C-GONN/JZA8757),from Montréal (CYUL) to Rouyn-Noranda (CYUY), responded to a TCAS warning by climbing from 9 800 ft to 10 400 ft. The warning had been set off by the rapid climb of a Boeing 737 which was flying VFR. JZA8757 descended again when it visually confirmed the position of the Xstrata Canada Corporation Boeing 737-2S2C (C-GXNR/RAG200) which was flying from Rouyn-Noranda to Montréal. The traffic was communicated. No impact on operations.

A Jazz Aviation DHC-8-102 (JZA8746), from Ottawa (CYOW) to Québec (CYQB), reported a TCAS RA and descended from 9 000 ft to 8 000 ft. The only traffic near the aircraft was a Pascan Aviation British Aerospace Jetstream 3201 (PSC401) which was descending from 2 500 ft on approach for CYND. JZA8764 later continued its climb. No impact on operations.

A Jazz Aviation DHC 8-402 (C-GGMQ/ JZA8556) from Victoria, BC (CYYJ) to Vancouver, BC (CYVR) departed CYYJ, climbing to 3000 feet, and responded to a TCAS RA. Traffic was a Harbour Air de Havilland DHC 3 Otter (C-GOPP/ HR305) from Victoria/ Inner Harbour, BC (CYWH) to Vancouver Harbour, BC (CYHC) VFR at 3500 feet. Traffic had been passed to both aircraft. HR305 reported having JZA8556 in sight. There was no impact to operations.

Approximately 10 southwest of Toronto, ON (CYYZ), an Air Canada Airbus A319 (ACA452) from Toronto, ON (CYYZ) to Ottawa, ON (CYOW) was climbing to 7000 feet, reported a TCAS RA and turned right before continuing on course. Traffic was a Skywest Airlines Bombardier CRJ-700 (SKW5159) form Houston, TX (KIAH) to Toronto, ON (CYYZ) level at 8000 feet in the downwind for runway 24R.

The Canadian North Boeing 737-300 (C-GICN) was operating as flight MPE1527 from Ottawa, ON (CYOW) to Fort MacKay/Albian, AB (CAL4). While in VMC on descent into CAL4 MPE1527 was in radio contact with a C208 Caravan transiting the area in an attempt to avoid a conflict. Passing through 5500 feet ASL MPE1527 received a TCAS RA advising them to stop their descent. The crew complied and avoided a further conflict with the C208.

A Jazz Aviation DHC-8-402 (JZA8404) from Fort McMurray, AB (CYMM) to Calgary, AB (CYYC) at FL220 reported they were responding to a TCAS RA and climbed to FL227. An Air Canada Airbus A320 (ACA154) from Edmonton, AB (CYEG) to Toronto, ON (CYYZ) was passing below at FL210. No other impact to operation.

A Westjet Boeing 737-7CT (WJA405 ) from Hamilton, ON (CYHM) to Moncton, NB (CYQM) performed a Traffic Collision and Avoidance System (TCAS) climb approximately 4 nautical miles final approach for Moncton Runway 11. The aircraft conducted a right hand circuit and landed Runway 11 without further incident.
 
Mir
Posts: 19092
Joined: Mon Jan 05, 2004 3:55 am

How Common Is A TCAS Warning?

Mon Jul 22, 2013 3:31 am

TCAS TAs are fairly common in my experience, but RAs are rare.

-Mir
7 billion, one nation, imagination...it's a beautiful day
 
wilco737
Posts: 7279
Joined: Sun Jun 20, 2004 12:21 am

How Common Is A TCAS Warning?

Mon Jul 22, 2013 4:48 am

I have almost 6000 hours and only had one RA during climb out back in 2005.

TA happen fairly often. Usually when you climb or descent with a high ate of climb/ descent towards your cleared level. And the TCAS doesn't know you will level off and then it calculates a conflict and issues a TA or RA.
Our policy is to reduce rate of climb/ descent to 1000 ft/min when within 1000 feet of the cleared level.

wilco737
  
 
nipoel123
Posts: 236
Joined: Thu Jan 13, 2011 6:23 am

RE: How Common Is A Tcas Warning?

Mon Jul 22, 2013 1:17 pm

Just heard one on the radio a couple of days ago from a Wizzair A320 climbing out from EIN.

I only have 40 hours or so, so if this continues statistically, I'd say they're very common  
one mile of road leads to nowhere, one mile of runway leads to anywhere
 
BoeingGuy
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Joined: Fri Dec 10, 2010 6:01 pm

RE: How Common Is A Tcas Warning?

Mon Jul 22, 2013 4:36 pm

Quoting Boeing77w (Reply 2):
Quoting 26point2 (Reply 1):
TCAS RA avoidance is made by flight director pitch changes only

It depends on aircraft type. The 737NG doesn't provide any Flight Director guidance. On receipt of an RA the pilot has to ignore the FD and pitch to an area outside of the red trapeze that appears on the PFD.

No Boeing airplanes have TCAS feed into the Flight Director. With a few exceptions, all Boeing airplanes have the red Trapazoid guidance ont he PFD that the previous poster referred to. It's a customer option on several modes to also put a red band "keep out zone" on the Vertical Speed Tape on the PFD. The latter is baseline on the 787 though.

Quoting JohnJ (Thread starter):
The captain came on the intercom later in the flight and explained that "you may have noticed that we quickly descended a few minutes ago then went back up. We got a warning in the cockpit of being too close to another plane. We received instructions to descend, while the other plane would have received instructions to go up. Sorry for any problems this may have caused." I got the impression he meant a TCAS warning vs. instructions from ATC to descend.

Yes, that's a TCAS "coordinated maneuver" since the other airplane was also equipped with TCAS.

It's worth noting that current industry guidance is to follow TCAS under any circumstances. You shoot first and ask questions later. Even if you think you have a visual on the traffic, you follow TCAS (it may be a different airplane that you don't see). If ATC gives you conflicting instructions, you follow TCAS (which would have prevented the DHL 757 mid-air).
 
BoeingGuy
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Joined: Fri Dec 10, 2010 6:01 pm

RE: How Common Is A Tcas Warning?

Mon Jul 22, 2013 9:15 pm

Quoting 26point2 (Reply 1):
TCAS RA avoidance is made by flight director pitch changes only (at the moment) and it is an aggressive pitch maneuver by design. The maneuver is hand-flown. If the pilot can see the conflict out the window he can dampen the pitch change but pilots are trained to follow the command bars passenger comfort be damned.

That's not entirely correct. TCAS RA's are not designed to be an aggressive maneuver, or "passenger comfort be damned". They are something in the order of 300 to 1500 feet per minute climbs or descents. The Flight Crew Training Manual directs crews to fly them smoothly and smoothly pitch up or down. They are not supposed to slam people to the ceiling or make people puke.

Also, you follow the pitch guidance on the PFD. You don't dampen it because you think you see the traffic. There might be another airplane causing the RA that you don't see.
 
cornutt
Posts: 333
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RE: How Common Is A Tcas Warning?

Wed Jul 24, 2013 2:53 am

As others have noted, the current TCAS system can only calculate and recommend pitch maneuvers. I work with some MIT-Lincoln Labs guys who are working on the next-generation ACAS system that will be able to calculate both horizontal and vertical maneuvers.
 
SAAFNAV
Posts: 337
Joined: Wed Mar 17, 2010 5:41 pm

RE: How Common Is A Tcas Warning?

Wed Jul 24, 2013 12:31 pm

Had a TA today. We were descending, and a level-flight C172 crossed our path.

1 000' which is quite a bit, but I don't the controller knew about that guy.

Wakes you up a bit though!

Erich
On-board Direction Consultant
 
DashTrash
Posts: 1266
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RE: How Common Is A Tcas Warning?

Wed Jul 24, 2013 3:39 pm

Quoting freeze3192 (Reply 3):
I've been flying 121 for about a year and a half, and I have about 1200 hours in 121 thus far. I've had at least 10 RA's in that time. Many were just the "monitor vertical speed" type RAs, but I'd say just under half were actual RA's where we were required to climb or descend.

The differentiating factor between me and the other pilots above is that I fly a turboprop, down low, in to and out of some of the busiest airports in the world. Couple that with 6 legs a day, up to 8 hours of flying and the RA's are bound to add up.

I would agree with your statement from my turboprop flying as well. Much of my flying was in the Northeast and RAs were common. Most were the monitor vertical speed type, but maybe (just guessing) 30-40% required control input.

After the turboprop flying I flew for a fractional in a jet. I don't think I had any RAs flying into the main airports around the country, including the ones I flew the prop into. Going into the outlying GA airports they were more common. Again, around the Northeast and Southern California. Both the turboprops and arrivals into those GA airports get descending earlier than the jet traffic going into the main airports and put in higher traffic areas with more VFR targets.

I've also gotten RAs from aircraft that didn't exist. One prompted a missed approach in crap weather at LGA, another was on a severe clear day climbing out of PHL. The PHL one I believe was our TCAS picking up our own transponder, as the target was right with us and climbed at the same rate. Both times ATC saw nothing. The LGA target may have been a low flying / scud running helicopter or light aircraft since it flew across our path a few hundred feet below. We were in the clouds so no luck seeing it visually.
 
JohnJ
Topic Author
Posts: 1362
Joined: Tue Jun 27, 2000 5:01 am

RE: How Common Is A Tcas Warning?

Wed Jul 24, 2013 5:44 pm

Interesting information, thanks for all the replies.

John
 
Boeing77W
Posts: 171
Joined: Tue May 15, 2007 6:27 am

RE: How Common Is A Tcas Warning?

Thu Jul 25, 2013 5:23 pm

Quoting BoeingGuy (Reply 8):
No Boeing airplanes have TCAS feed into the Flight Director. With a few exceptions, all Boeing airplanes have the red Trapazoid guidance ont he PFD that the previous poster referred to.

That's what I wrote...is it not? Apologies if I've missed something here.
 
BoeingGuy
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RE: How Common Is A Tcas Warning?

Thu Jul 25, 2013 9:24 pm

Quoting Boeing77w (Reply 14):
Quoting BoeingGuy (Reply 8):
No Boeing airplanes have TCAS feed into the Flight Director. With a few exceptions, all Boeing airplanes have the red Trapazoid guidance ont he PFD that the previous poster referred to.

That's what I wrote...is it not? Apologies if I've missed something here.

Yep. You correctly stated the 737 doesn't have Flight Director RA guidance. I followed up by stating that none of the Boeing models do, not just the 737.

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