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Tcas Coupled To The Autopilot?  
User currently offlinetitanmiller From United States of America, joined May 2006, 89 posts, RR: 0
Posted (3 years 9 months 1 week 6 days 1 hour ago) and read 4359 times:

Are there any aircraft that have the TCAS coupled to the autopilot so that an RA can be automatically followed? If the pilot determines that following the RA is more dangerous than not following it then he/she could simply disconnect the autopilot and take control.

If not, any ideas as to why this hasn't been implemented?

21 replies: All unread, jump to last
 
User currently offlineFly2HMO From , joined Dec 1969, posts, RR:
Reply 1, posted (3 years 9 months 1 week 6 days ago) and read 4335 times:

Quoting titanmiller (Thread starter):
Are there any aircraft that have the TCAS coupled to the autopilot so that an RA can be automatically followed?

Not that I am aware of. And I'm not too sure I'd want the autopilot to do such things.

Quoting titanmiller (Thread starter):
If not, any ideas as to why this hasn't been implemented?

For one, the autopilot can't actually see the offending aircraft in an RA. In a clear day if an RA is given and the pilots of both aircraft have each other in sight and they determine they are safe, then the RA may be ignored. That's something an autopilot can't decide on it's own.

[Edited 2010-10-18 20:46:46]

[Edited 2010-10-18 20:47:32]

User currently offlineGoBoeing From United States of America, joined Jun 2000, 2682 posts, RR: 14
Reply 2, posted (3 years 9 months 1 week 6 days ago) and read 4319 times:

Quoting titanmiller (Thread starter):
If not, any ideas as to why this hasn't been implemented?

A TCAS resolution advisory is not the type of thing that you would want the autopilot to respond to.

Remember, ATC is not expecting whatever it is the pilot is about to do. If the TCAS says climb, that's it -- you have to climb. It may not be any fault of the air traffic controller since the traffic could be VFR and not in communications with them. Because of this issue, hand flying is the best option as it ensures the aircraft is headed back towards the assigned altitude as soon as the conflict is over.

Another consideration is how abruptly an autopilot would do this maneuver. A "monitor vertical speed" while you're coming down at 1000 feet per minute at 200 knots might just necessitate pulling the nose up a degree or two and shallowing out the descent. However, picture an RA at FL220 and 310 knots. "CLIMB, CLIMB NOW." Of course, following this guidance in a timely manner is important, but there are flight attendants walking in the cabin, and there could be passengers up and moving around as well. Do you really want to float someone into the ceiling and risk breaking their neck just because some airplane a couple miles away didn't have a shallow level-off at an altitude near yours? Of course not. So again in this case, hand flying the maneuver smoothly prevents excessive G-force -- I can't see all autopilots doing a good job with that in all situations.

Quoting Fly2HMO (Reply 1):
In a clear day if an RA is given and the pilots of both aircraft have each other in sight and they determine they are safe, then the RA may be ignored.
False.

And the reason is the reason for TCAS itself -- the traffic the crew is looking at may not be the one that is the threat.

The only thing that knows for sure what airplane is what is the TCAS. It is in communication with the other transponders and they are working together to prevent a collision. If it's a nice clear day and the crew sees a plane off their right wing and they get an RA to "CLIMB, CLIMB NOW", they have to climb. The aircraft that is a threat might be 1000 feet below them and climbing at 3000FPM, while the traffic the crew has in sight putters along watching the whole thing from the side.

Funny for me to read your post, titanmiller, because I had my first RA in months just this morning. We were departing MDW at dawn. Right to 090 off 4R, level off at 3000 which comes up in the first minute off the ground. We're cleaning up and then we're assigned 4000 and departure calls traffic at 11 o'clock and 2 miles 500 feet above us. They said when able turn left to 060. We elected to wait because we saw the traffic watch Cessna still getting closer and we were at the same altitude. As we approached 4000, we got "TRAFFIC . . . TRAFFIC . . . MONITOR VERTICAL SPEED." To keep our attitude in the green box we needed to overshoot 4000' by a bit. Nice little opener for our 4 leg, 13 hour workday.


User currently offlineDashTrash From United States of America, joined Aug 2006, 1519 posts, RR: 2
Reply 3, posted (3 years 9 months 1 week 6 days ago) and read 4305 times:

Quoting GoBoeing (Reply 2):
False.

And the reason is the reason for TCAS itself -- the traffic the crew is looking at may not be the one that is the threat.

We had relief in the FOM that allowed us to disregard an RA if we deemed necessary (think on an arrival with somebody 1000 above going the same direction and someone climbing out leveling off 1000 below going the opposite direction.)

Quoting GoBoeing (Reply 2):
Funny for me to read your post, titanmiller, because I had my first RA in months just this morning. We were departing MDW at dawn. Right to 090 off 4R, level off at 3000 which comes up in the first minute off the ground. We're cleaning up and then we're assigned 4000 and departure calls traffic at 11 o'clock and 2 miles 500 feet above us. They said when able turn left to 060. We elected to wait because we saw the traffic watch Cessna still getting closer and we were at the same altitude. As we approached 4000, we got "TRAFFIC . . . TRAFFIC . . . MONITOR VERTICAL SPEED." To keep our attitude in the green box we needed to overshoot 4000' by a bit. Nice little opener for our 4 leg, 13 hour workday.

I had one coming out of PHL where the TCAS decided our aircraft was a threat to itself. That was interesting.


User currently offlineBMI727 From United States of America, joined Feb 2009, 15718 posts, RR: 26
Reply 4, posted (3 years 9 months 1 week 5 days 23 hours ago) and read 4292 times:

Quoting GoBoeing (Reply 2):
hand flying is the best option as it ensures the aircraft is headed back towards the assigned altitude as soon as the conflict is over.

An autopilot couldn't do that?

Quoting GoBoeing (Reply 2):
However, picture an RA at FL220 and 310 knots. "CLIMB, CLIMB NOW." Of course, following this guidance in a timely manner is important, but there are flight attendants walking in the cabin, and there could be passengers up and moving around as well. Do you really want to float someone into the ceiling and risk breaking their neck just because some airplane a couple miles away didn't have a shallow level-off at an altitude near yours? Of course not. So again in this case, hand flying the maneuver smoothly prevents excessive G-force -- I can't see all autopilots doing a good job with that in all situations.

Why couldn't the system and the autopilot make that distinction?



Why do Aerospace Engineering students have to turn things in on time?
User currently offlineGoBoeing From United States of America, joined Jun 2000, 2682 posts, RR: 14
Reply 5, posted (3 years 9 months 1 week 5 days 23 hours ago) and read 4286 times:

Quoting BMI727 (Reply 4):
An autopilot couldn't do that?

I would not trust it to pitch down gradually enough. Not in the plane I fly anyway. Additionally, you have the issue of whether or not ATC now wants you to just stay put at your new altitude, or go back down. It could be a few hundred feet, and they may prefer you to stay put and wait for higher or lower to continue in the direction you originally wanted to go instead of expediting back to the last assigned.

Quoting BMI727 (Reply 4):
Why couldn't the system and the autopilot make that distinction?

If programmed correctly it could but why not take the doubt out of it when you're talking about someone being injured in a moving vehicle that is anywhere from 10 minutes to several hours from being on the ground, and then a drive to the nearest hospital from there.

As DashTrash mentions, these things all malfunction. Would you want an autopilot to aggressively respond to a TCAS RA that is very obviously a bogus, erroneous resolution advisory? Definitely not.


User currently offlineGoBoeing From United States of America, joined Jun 2000, 2682 posts, RR: 14
Reply 6, posted (3 years 9 months 1 week 5 days 23 hours ago) and read 4285 times:

Quoting DashTrash (Reply 3):

We had relief in the FOM that allowed us to disregard an RA if we deemed necessary (think on an arrival with somebody 1000 above going the same direction and someone climbing out leveling off 1000 below going the opposite direction.)

We don't even have that.

The only instance in which we are allowed to disregard a TCAS RA is when it is deemed unsafe. I take that to mean, "TRAFFIC, DESCEND" when you are approaching a ridge that the TCAS doesn't know about but the GPWS will soon scream about! And similar situations...on final in IMC getting a descent RA but you'd have to dive below the glideslope to follow it. Not sure I'd be keen on doing that either.


User currently offlineBMI727 From United States of America, joined Feb 2009, 15718 posts, RR: 26
Reply 7, posted (3 years 9 months 1 week 5 days 20 hours ago) and read 4236 times:

Quoting GoBoeing (Reply 5):
Not in the plane I fly anyway.
Quoting GoBoeing (Reply 5):
If programmed correctly it could
Quoting GoBoeing (Reply 5):
ould you want an autopilot to aggressively respond to a TCAS RA that is very obviously a bogus, erroneous resolution advisory? Definitely not.

Well, if you limit it to purely current technology. But there are really no technical hurdles that could not be overcome to make autopilots able to react to TCAS warnings, and by extension, make single pilot ops feasible for larger planes.



Why do Aerospace Engineering students have to turn things in on time?
User currently offlineCCA From Hong Kong, joined Oct 2002, 830 posts, RR: 14
Reply 8, posted (3 years 9 months 1 week 5 days 18 hours ago) and read 4202 times:

Airbus.

Quote:
The Airbus solution is to integrate the TCAS resolution advisory with the flight director and the autopilot, so if the autopilot is engaged it will fly the resolution advisory, and if it is not the pilots have only to follow the flight director - with which they are totally familiar - to carry out a successful manoeuvre.
http://www.flightglobal.com/articles...lotflight-director-tcas-works.html



C152 G115 TB10 CAP10 SR-22 Be76 PA-34 NDN-1T C500 A330-300 A340-300 -600 B747-200F -200SF -400 -400F -400BCF -400ERF -8F
User currently offlineMax777geek From Italy, joined Mar 2007, 538 posts, RR: 0
Reply 9, posted (3 years 9 months 1 week 5 days 17 hours ago) and read 4201 times:

Quoting CCA (Reply 8):
The Airbus solution is to integrate the TCAS resolution advisory with the flight director and the autopilot, so if the autopilot is engaged it will fly the resolution advisory, and if it is not the pilots have only to follow the flight director - with which they are totally familiar - to carry out a successful manoeuvre.

Airbus solution doesn't sound a wise thing to do in a messy airspace...


User currently offlineBMI727 From United States of America, joined Feb 2009, 15718 posts, RR: 26
Reply 10, posted (3 years 9 months 1 week 5 days 16 hours ago) and read 4162 times:

Quoting Max777geek (Reply 9):
Airbus solution doesn't sound a wise thing to do in a messy airspace...

Why? It's getting its data from TCAS, and presumably GPWS is in the loop as well. The combination tells the pilot or autopilot where to fly.



Why do Aerospace Engineering students have to turn things in on time?
User currently offlineMax777geek From Italy, joined Mar 2007, 538 posts, RR: 0
Reply 11, posted (3 years 9 months 1 week 5 days 13 hours ago) and read 4087 times:

Quoting BMI727 (Reply 10):

Why? It's getting its data from TCAS, and presumably GPWS is in the loop as well. The combination tells the pilot or autopilot where to fly.

With the exception that the pilot rules on his visual, ie if there's on path an ariplane without tcas installed, most likely the pilot will not try to hit it.


User currently offlineGoBoeing From United States of America, joined Jun 2000, 2682 posts, RR: 14
Reply 12, posted (3 years 9 months 1 week 5 days 11 hours ago) and read 4028 times:

Quoting BMI727 (Reply 7):
Well, if you limit it to purely current technology. But there are really no technical hurdles that could not be overcome to make autopilots able to react to TCAS warnings, and by extension, make single pilot ops feasible for larger planes.

Okay, I just got done explaining several reasons why judgement that a computer lacks is something that a TCAS RA response should include. If you don't believe any of it, fine. I'm sure you've read lots of TCAS RA reports, practiced them in a simulator, and responded to them out flying the line yourself.


User currently offlineBMI727 From United States of America, joined Feb 2009, 15718 posts, RR: 26
Reply 13, posted (3 years 9 months 1 week 5 days 10 hours ago) and read 4010 times:

Quoting Max777geek (Reply 11):
With the exception that the pilot rules on his visual, ie if there's on path an ariplane without tcas installed, most likely the pilot will not try to hit it.

Then TCAS needs to be on every plane, which should have been done years ago.

Quoting GoBoeing (Reply 12):
Okay, I just got done explaining several reasons why judgement that a computer lacks is something that a TCAS RA response should include. If you don't believe any of it, fine. I'm sure you've read lots of TCAS RA reports, practiced them in a simulator, and responded to them out flying the line yourself.

The judgement a computer lacks isn't the biggest hurdle to increased automation and/or single pilot ops.



Why do Aerospace Engineering students have to turn things in on time?
User currently offlineDiamondFlyer From United States of America, joined Oct 2008, 1508 posts, RR: 3
Reply 14, posted (3 years 9 months 1 week 5 days 10 hours ago) and read 4008 times:

Quoting BMI727 (Reply 13):
Then TCAS needs to be on every plane, which should have been done years ago.

You have to be kidding me. The cost of TCAS alone is absurd for a vast majority of planes in the country today, when they will get little to no benefit from it.

-DiamondFlyer


User currently offlineGoBoeing From United States of America, joined Jun 2000, 2682 posts, RR: 14
Reply 15, posted (3 years 9 months 1 week 5 days 10 hours ago) and read 3995 times:

Quoting DiamondFlyer (Reply 14):
You have to be kidding me. The cost of TCAS alone is absurd for a vast majority of planes in the country today, when they will get little to no benefit from it.

It is apparent that BMI has little to no real experience at all, so this is the type of suggestion that you get.

I agree -- it is not going to happen in all airspace.

And, we regularly exit class B airspace in 121 operations so there is still going to be plenty of VFR traffic out there without a TCAS.


User currently offlineBMI727 From United States of America, joined Feb 2009, 15718 posts, RR: 26
Reply 16, posted (3 years 9 months 1 week 5 days 9 hours ago) and read 3961 times:

Quoting DiamondFlyer (Reply 14):

Well that's the alternative if you think the risk is unacceptable. But it's probably cheaper to just have an accident every so often.



Why do Aerospace Engineering students have to turn things in on time?
User currently offlineDashTrash From United States of America, joined Aug 2006, 1519 posts, RR: 2
Reply 17, posted (3 years 9 months 1 week 5 days 9 hours ago) and read 3961 times:

Quoting BMI727 (Reply 10):
Why? It's getting its data from TCAS, and presumably GPWS is in the loop as well. The combination tells the pilot or autopilot where to fly.
Quoting DashTrash (Reply 3):
(think on an arrival with somebody 1000 above going the same direction and someone climbing out leveling off 1000 below going the opposite direction.)
Quoting DashTrash (Reply 3):
I had one coming out of PHL where the TCAS decided our aircraft was a threat to itself. That was interesting.
Quoting GoBoeing (Reply 6):
We don't even have that.

The only instance in which we are allowed to disregard a TCAS RA is when it is deemed unsafe. I take that to mean, "TRAFFIC, DESCEND" when you are approaching a ridge that the TCAS doesn't know about but the GPWS will soon scream about! And similar situations...on final in IMC getting a descent RA but you'd have to dive below the glideslope to follow it. Not sure I'd be keen on doing that either.

That's probably closer to the intent on our relief, but when flying turboprops into large airports ATC fills the holes with you. We get out descents earlier than the jets, the slowed while 2 or 3 pass us 1000 ft above on the arrival. They're at 10, we're at 9, and the departures are climbing to 8.

I got out of the turboprops and into something MUCH faster. Then it was the opposite problem.....


User currently offlineDiamondFlyer From United States of America, joined Oct 2008, 1508 posts, RR: 3
Reply 18, posted (3 years 9 months 1 week 5 days 7 hours ago) and read 3904 times:

Quoting BMI727 (Reply 16):
Well that's the alternative if you think the risk is unacceptable. But it's probably cheaper to just have an accident every so often.

Let me get this straight. You think putting TCAS would do anything to prevent a mid-air between a Part 121 carrier and an aircraft not equipped with TCAS. You do know that a vast majority of aircraft out there which aren't equipped with TCAS rarely or never venture into the airspace in which 50% or more of 121 operations take place in.

The amount of flag waving for the scheduled air carriers is unbelievable. Without general aviation, there is no aviation. But hey, lets continue to drive the prices up. Damn the little guy, all we care about is some marginally profitable airlines.


User currently offlineFly2HMO From , joined Dec 1969, posts, RR:
Reply 19, posted (3 years 9 months 1 week 4 days 21 hours ago) and read 3799 times:

Quoting GoBoeing (Reply 2):
False.

And the reason is the reason for TCAS itself -- the traffic the crew is looking at may not be the one that is the threat.

The only thing that knows for sure what airplane is what is the TCAS. It is in communication with the other transponders and they are working together to prevent a collision. If it's a nice clear day and the crew sees a plane off their right wing and they get an RA to "CLIMB, CLIMB NOW", they have to climb. The aircraft that is a threat might be 1000 feet below them and climbing at 3000FPM, while the traffic the crew has in sight putters along watching the whole thing from the side.

A valid point. However, I am basing myself on more than a dozen Captain Incident Reports I filed at my former airline where they state they ignored the TCAS when they had the offending traffic in sight.


User currently offlineN243NW From United States of America, joined Jul 2003, 1626 posts, RR: 20
Reply 20, posted (3 years 9 months 1 week 4 days 10 hours ago) and read 3716 times:

Quoting DashTrash (Reply 3):
I had one coming out of PHL where the TCAS decided our aircraft was a threat to itself. That was interesting.

The TIS system in our Diamonds and Pipers does that all the time...it only polls the airspace around the airplane once every few seconds, so if you turn suddenly it doesn't have enough time to catch up with your own Mode C signal and identifies the airplane itself an intruder. This happens almost all the time during an upwind to crosswind turn, when the aircraft is climbing steeply, at a slow airspeed and turning much more quickly than standard rate.

It can scare the bejeebus out of you if you're not expecting to suddenly see a blip on the moving map right on top of you with "+0" as the altitude variation, but I've learned to ignore it, especially if I'm at a towered airport where I know there are no other planes turning crosswind.



B-52s don't take off. They scare the ground away.
User currently offlineFly2HMO From , joined Dec 1969, posts, RR:
Reply 21, posted (3 years 9 months 1 week 4 days 6 hours ago) and read 3669 times:

Quoting N243NW (Reply 20):

The TIS system in our Diamonds and Pipers does that all the time...it only polls the airspace around the airplane once every few seconds, so if you turn suddenly it doesn't have enough time to catch up with your own Mode C signal and identifies the airplane itself an intruder. This happens almost all the time during an upwind to crosswind turn, when the aircraft is climbing steeply, at a slow airspeed and turning much more quickly than standard rate.

Yeah I saw that a lot too with ADS-B targets as well. A ghost would appear right on top of my plane. Later software revisions seemed to mitigate the issue.


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