Tcas

[sangiovese.]

http://www.news.mod.uk/news_headline_story2.asp?newsItem_id=3916
Interesting article, didn't spot too many journalistic interpretations

[ShyTorque]

Typical spin, not sure that fitting what is now a routinely available piece of kit is worth a safety prize though.

They forgot to mention that the other half of the TCAS equation is the requirement for a functioning transponder in the other aircraft.

However, it's a great piece of equipment that should provide a very worthwhile contribution to safety. Once you have used it you don't want to go back to flying without it :ok:

[MrBernoulli]

I'm not sure I understand this.

"Aircraft crash avoidance system developed at RAF Linton-on-Ouse."
In what way have they developed anything?

"....adapted a North Carolina company's Traffic Alert and Collision Avoidance System (TCAS) for use on its fleet of Tucanos."
What? You mean fitted TCAS to the Tucano? How is that 'developing'?

Anyone from the Tucano world care to enlighten us? I'd be interested to hear.

[flipster]

Points raised so far (i'm sure they are not lost on the chaps at Linton):

TCAS is a great aid at Med and Hi Level
But it is nothing new
It only works if the other ac are transponding too - you even get mutual resolutions with Mode S
It will be of some benefit at LL but not a panacea for all ills
This was pretty awful spin-type reporting (but what else do you expect!?)

also,

Even with 2 transponding ac - cumulo-granite will interfere. A couple of years ago, 2 Hercs could have come head-to-head in the Brecon valley - despite TCAS. Luckily both ac saw the other BEFORE TCAS did on the J and did a quick 'step right'.

Therefore, there is no substitute for the Mk1 eyeball at low-level, its just that TCAS MIGHT SOMETIMES help an early viz acquisition. Again, I suspect that this is not lost on L-O-O, Valley or CFS.

[Pierre Argh]

Is this TCAS or a new system... to be of real use in a low level environment you would need a real motion, not relative motion, display to allow the pilot to manoeuvre laterally (A TCAS RA to descend when at low level wouldn't be much use?). As others have said...

a. it relies on the other aircraft transponding, and

b. the SSR data from the other aircraft having been verified... (incorrect Mode C might lull a pilot into a false sense of security)

This will can, virtually, be guaranteed above F100, so will reduce the number of "close misses with airliner reports in the papers... but be much less reliable in Class G airspace below 3000ft (7000 and other special use squawks, plus microlights, gliders etc)

Can anyone put a bit more detail onto this sparse report?

[Elmlea]

I'm not sure I understand this.

"Aircraft crash avoidance system developed at RAF Linton-on-Ouse."
In what way have they developed anything?

"....adapted a North Carolina company's Traffic Alert and Collision Avoidance System (TCAS) for use on its fleet of Tucanos."
What? You mean fitted TCAS to the Tucano? How is that 'developing'?

Anyone from the Tucano world care to enlighten us? I'd be interested to hear.

They've bought a pile of off-the-shelf TCAS modules which are being introduced across the fleet. They've had a fairly lengthy trial, and have decided to go for it. I can't remember the name of the system but I'll have a look.

For anyone who's flown Tucano recently, it's replacing the standby AI, which is being relegated about 12" lower to where the RMI used to be. This makes flying standby AI approaches the huge embuggerance it should be :sad:

It seems to work fairly well; or at least I think so, considering it was the first time I'd seen TCAS in operation. I'd be worried that brand-new BFJT studes may assume that lookout's now taken care electronically... Tucanos don't seem to have too many near-misses, so I'm not sure why they've decided to embody it. I'm sure come the release across the fleet someone'll say!

At the end of the day, they're slower than everyone else at 250ft so anything which helps spot 420kts traffic a bit quicker sounds fairly useful to me.

[Brain Potter]

If this is an ordinary TCAS I just hope the CFS do not expect more from it than it can deliver. I have already heard KingAir METS graduates stating "Clear Left on TCAS" before commencing a turn whilst IMC. The TCAS is not designed to provide this function and the display is not suitable as a reference for lateral manoeuvres. It will protect you if the turn then results in a confliction, which may be resolved with a vertical manoeuvre.

[Elmlea]

It certainly looked like ordinary, stand-alone TCAS. It beeps TAs in your ears, but doesn't issue RAs as far as I'm aware. With the position of the aerials I assumed blanking from the fuselage would be a bit of an issue in some directions. I'm not sure how it's going to be worked into the training, but I hope it's just used as an extra aid to safety and not a primary reference in any way.

[Uncle Ginsters]

As has already ready said, a great 'tool in the box' at low-level

Does anyone know if the trial included a look in to terrain-linked effects on the signal? (i.e 'wave bending' effects or a LL signal bounced off of water?)

TCAS works as long as both ac are transponding - anyone remember the 2 Hawk vs. airliner Airprox somewhere in the NW of England? I seem to remember that one major factor was that the Hawk(s) weren't squawking. Has any SOP been implemented to ensure that all LL ac ARE squawking in that environment - without it, TCAS is surely only a distraction at LL?

L:eek: :eek: kout still wins the day methinks.

Uncle G

[PPRuNeUser0211]

"I assume Tucano has or will have radalt."... guffaw;) ga99js, sorry old bean, not much chance of that happening anytime soon I dont think.... Afraid the low level altimeter is the mk1 eyeball... which may, or may not, interpret 250' as 250', depending on the instructor!

Elmlea, Tuc's have had their fair share of misses, but as you correctly point out, is often as not them turning into the path of something going speed of snot at low level...

[Farfrompuken]

As someone who has exensive experience of Tcas and understands the demands
placed under the Tucano crews in low-level conditions, all I can add is that is that is HAS to be better than nothing!

It will no doubt be employed in the TA mode throughout its use (circuits etc) but will only add, not replace, to the lookout the crew are employing. The Tucano installation is a very low-cost, not 100% ideal solution, but is a step in the right direction.

It will not counter against non-transponding targets, but will be an invaluable tool towards flight safety.

Those that criticise often have little or no experience of TCAS and assume it will either a) negate lookout or b) be useless.

The reality is that it will sit somewhere healthily in between. Fairly soon I imagine ALL traffic, gliders/microlights etc, will have to carry some form of basic transponding kit by law.

Better the rest of the military get kitted soon.

[Elmlea]

Those that criticise often have little or no experience of TCAS and assume it will either a) negate lookout or b) be useless.

I must admit I fall in to the former camp; I've got no experience of TCAS, and I'm worried about how hard-working, busy BFJT studes will take to its introduction. Once they've realised on a couple of GH trips that every tally they call has already been spotted by TCAS; and that it spots quite a few that neither they nor the QFI spot for real; I'm sure they'll start relying on it. Especially if they think that bad marks for lookout stem from the QFI spotting things they don't!

The risk there is that they use it not just to supplement their lookout or improve its effectiveness but to guide them when to look. It'll take a couple of spots which they get that TCAS doesn't for them to realise it's an aid rather than a replacement. I'm sure when I was there I would have been happy with a tool which told me where and when I needed to lookout if I wanted to be able to call a tally!

Of course, it all depends on how QFIs at Linton are told to teach its use; but I really hope studes don't come to lean on it too much.

[PPRuNeUser0211]

I just reckon it will make solo studes paranoid.... when I was there if you saw another gent in the neighbourhood you scooted off five miles to do your aeros, for risk of p@@"!~@ng off some qfi doing s&L 1! with TCAS i would have been somewhere over the north sea!

[Farfrompuken]

Elmlea:

"The risk there is that they use it not just to supplement their lookout or improve its effectiveness but to guide them when to look."

That's exactly why TCAS is so handy! :zzz: Wait till you use it before you comment!! It'll probably be most useful in the GH-style environment at Linton but has been tested with some success at Low-Level.

SOPs should prevent mis-use, provided those introducing them (the SOPs) have a decent working knowledge of TCAS.

The long and short of it is that TCAS is a handy tool, but you're not going to be flying around glued to the 'fish finder' for gawd's sake. The sooner people realise that the sooner they'll stop spouting hoop.:rolleyes:

[juliet]

re: RA at low level. TCAS will still give an RA at low level. It will not descend you into the ground as some like to believe, instead the low aircraft will be told to maintain its height while the other aircraft will be told to climb.

[Elmlea]

That's exactly why TCAS is so handy! :zzz: Wait till you use it before you comment!! It'll probably be most useful in the GH-style environment at Linton but has been tested with some success at Low-Level.

Sorry, I don't think I made myself clear. I'd be worried that studes only look out when there's something on the TCAS screen to look for; hence they may not even try to look for things TCAS hasn't picked up.

I appreciate it's useful in that it directs you where to look; but only if it's spotted them first!

I've tried it in the GH environment at Linton, and it was pretty successful. There were a couple of spots that hadn't appeared on the TCAS screen though, which are what led me to think this way. However, it did lead us to spot a few things further away than we normally would, so that's undoubtedly useful.

I didn't get the chance to try it at low level, but I'm looking forward to it when it comes in across the fleet. I'm not looking forward to the next IRT with where the standby AI's wound up though! :uhoh:

[ShyTorque]

re: RA at low level. TCAS will still give an RA at low level. It will not descend you into the ground as some like to believe, instead the low aircraft will be told to maintain its height while the other aircraft will be told to climb.

TCAS may or may not give RAs, depending on the mode settings! For Class G low level ops, TA is perfectly OK.

IF a student pilot were stupid enough to think he can get away with only looking out for TCAS targets, the sight of his microlight, glider or other non-squawker that passes close by will soon make him change his mind! :eek:

[Elmlea]

TCAS may or may not give RAs, depending on the mode settings! For Class G low level ops, TA is perfectly OK.
IF a student pilot were stupid enough to think he can get away with only looking out for TCAS targets, the sight of his microlight, glider or other non-squawker that passes close by will soon make him change his mind! :eek:

Do all TCAS setups give RAs, or only ones with links to the VSI like the Herc J?

I'm sure some student pilots will rely on TCAS, and it'll take the first tally which TCAS didn't identify to stop them doing that. But, it'll be a great safety tool at LL so I won't complain. I'm pretty sure the TCAS system's replicated front to back; so the back seat can switch it off if need be anyway ;)

[Pierre Argh]

It will not descend you into the ground as some like to believe I was interested to read this, but puzzled how, without Radalt (see other post) the system knows when the aircraft is near the ground... or are we just talking about below 3000ft?

[Farfrompuken]

Elmlea,

You're chasing your own tail here, sounding far beyond your years than your title suggests;)

Let me spell it out for you:

TA: Traffic advisory. Lets you know graphically where traffic is.

RA: Resolution advisory. Provides commands via VSI to achieve vertical separation.

Tucano system will not be linked to VSI as far as I know; it appears to be a standalone dispay. Therefore, It won't be capable of RA. Even if it were, you could select TA mode to avoid nuiscance alerts (e.g. in circuit etc....).

As I mentioned earlier, it is a tool to ASSIST lookout, not replace it. YOU WILL NOT BE FLYING ALONG STARING AT THE FISHFINDER UNLESS YOU ARE TOTALLY STUPID.

The flight regimes that the Tucano operates in at med level will be where it benefits the most (microlites et al no squawking lower down etc).

Wait till you've got a tad of time on the kit, then by all means let us know what you think, but to comment with no knowledge is a tad churlish:hmm:

And another thing....don't bother switching it off-you'd be a tool to do so.

[Brain Potter]

My point about the METS graduates is that it seems that CFS have invented yet another thing to talk about whilst flying. I think it is totally unnecessary for crews to comment on a blank TCAS display before manouvreing and it is incorrect to modify manoeuvres in the lateral plane purely based on TCAS information. So why mention it? - unless it has picked up a contact that you are trying to aquire visually. Apologies to the CFS guys if this is not of their doing, but some of their recent graduates have got this habit from somewhere. Maybe it's part of the "I must commentate on everything I do or think in order to impress you" strategy that the trg system seems to produce.

[A and C]

Wile I think that any device that can help to avoid a collision is a good thing and I understand that in military aviation RA commands are not a good idea I cant help thinking that the big picture has been missed.

In the USA traffic information can be data linked via the mode S transponder from ATC ground radar giving the pilot a "near TCAS" system that seems to do all that the system fitted to the Tucano will do but at a fraction of the cost of the device fitted to the Tucano. The only problem is getting NATS to enable the system.

It would seem to me that if the ground station part of this system could be put on line the low cost of the aircraft equipment would encourage the MOD to fit it to more of the military fleet, the cost is within the budget of even the lower end of the IFR equiped private aircraft fleet.

Having most of the aircraft flying in class G airspace equiped with a collision avoidence system should be a goal of the CAA and MOD it would make flying safer for both the civil and military pilots and in the long run must save all airspace users money.

The bonus with the system is that it can also be linked to ground weather radar giving weather avoidance information to aircraft that can't be fitted with weather radar.

It is time for the military and civil airspace users to get together for the common good and press NATS and Eurocontrol into enableing this system.

www3.bendixking.com/servlet/com.honeywell.aes.utility.PDFDownLoadServlet?FileName=/static/brochures/pdf/KMH%20880%20KTA%20870.pdf

[ShyTorque]

There seems to be a great deal of misunderstanding about TCAS and some scepticism from those who have never had the opportunity to fly with it.

Over the last 7 years I have been flying TCAS equipped aircraft for my bread and butter, mainly in class G airspace. The equipment we operate does NOT give RAs, only TAs. It is not linked to the radalt.

Simply put, the equipment transmits, just like an ATC secondary radar, and picks up transponder returns which are displayed on the circular screen. The airspace display can be "zoomed" in or out in stages, as the pilot sees fit. In the case of the present aircraft I fly, the displayed range can be set from 40 nautical miles to 3 miles. I normally fly with it set at 10 nm or 15 nm by preference, depending on the circumstances.

If a "Mode C" return is picked up, a diamond dot appears with relative altitude figures alongside. For example, "00" means same altitude and "+05" means 500 feet above or "-03" means 300 feet below. An up or down arrow alongside that figure means the traffic is climbing or descending respectively. As the "Mode C" altitude figures are based on information from a coding altimeter, they are generally very accurate.

If a "Mode A" only return is picked up, the relative altitude figures are absent and only a diamond dot appears on the screen. These are the worrying ones, such a target could be 2700 feet above or below the aircraft, the TCAS can't tell.

Relative azimuth information is computed and isn't as reliable as the altitude information. For example, an aircraft actually directly ahead could be shown as slightly left or right of the nose, or it may oscillate from left to right across the nose. If the TCAS decides there is a possibility of aircraft paths crossing based on "Mode A" azimuth information alone, it plays safe and gives a TA alert. These can be very worrying at the time, the supposedly conflicting aircraft could be out of sight above or below; natural survival instinct means that the pilot's eyes are generally out on stalks at this stage.

A TA comes in the from of a (loud) digital voice input to the pilot's intercom: "TRAFFIC, TRAFFIC!"

It is up to the pilot to hear the warning (not difficult!) interpret the displayed information and to carry out avoiding action if necessary. It might or might not be necessary and is preferably done after visually acquiring the opposing traffic, NOT by looking at the dial in isolation. In IMC height separation is safest, due to the limitations of azimuth accuracy.

The use of TCAS whilst flying at 250 feet shouldn't give any problems as far as I can see; it certainly didn't when I flew a police helicopter.

[ukatco_535]

One thing that the TCAS user must be aware of is that the azimuth information is not particularly accurate (as intimated by shy tourque) and certainly not up to the required standard for ATC radar separation purposes.

The amount of professional airliner pilots who try to second guess ATC by saying they have the traffic on TCAS, and requesting further climb/descend as a result is ridiculous.

I hope that the students are taught how to use it properly and are fully informed of its limitations - it is a very good tool when used properly for what it is designed for. It does not replace the mark 1 eyeball, it augments it.

[Pierre Argh]

Some respondants have been quick to criticise others who have posted... many will not have flown with TCAS, or ar ATCO's etc... so are asking questions to broaden their understanding, not necessarily being critical or dismissive?

Shytorgue says if a Mode A only response is detected the contact may be 2700 above or below... how does the system know, without Mode C to help, that it is not outside that band?

[BEagle]

As far as I'm aware, non-altitude reporting SSR-equipped traffic will be assumed to be co-altitude and will, if their closest point of approach is predicted to enter the traffic advisory sector, cause a TA to be issued.

ukatco_535 is absolutely correct with what he states - you must not rely upon TCAS bearing information as it is highly inaccurate. Neither must those using the very basic Tucano system belive that it is anything like as comprehensive as ACAS II used by commercial aircraft.

ShyTorque's figure of 2700ft above or below comes from the ability of some TCAS displays to be switched to display only traffic which is either within the altitude band of 2700 ft above or below the aircraft in 'normal' mode, 8700 ft above to 2700 ft below in 'above' mode or 2700 ft above to 8700 ft below in 'below' mode as determined by Mode C or Mode S altitude. As any non-altitude reporting aircraft are assumed to be co-altitude, they will be therefore be displayed as being within the 2700 ft above or below area in 'normal' mode even if actually well outside that as the system cannot determine their actual altitude.

Most, but by no means all, GA puddlejumpers not receiving an ATC service will routinely squawk 7000C if so equipped - but many still only have Mode A. TAs based on Mode A traffic could well prove a huge distraction in some parts of the UK to pilots using TCAS in Class G airspace. An environment for which TCAS was never intended! And don't forget that carriage of even Mode A is still not mandatory for most VFR GA traffic in Class G airspace.......

[Pierre Argh]

BEagle... thank you for expanding somewhat on this subject, and rasing some interesting and valid points... one addition on the subject of 7000 squawks is that the Mode C from such aircraft is unverified and, although unlikely, may be incorrect. This may give a false sense of safety and encourage the pilot to discount the contact (as discussed elsewhere on this forum). Keep your eyes open and in Class G use TCAS as a tool to prevent collisions not maintain separation, a subtle but important difference.

[Brain Potter]

The "verification" of Mode C readouts by ATC SSR is to allow them to reduce lateral seperation. An RA issued by TCAS will be followed regardless of the existence of any verification of the intruders Mode C by ATC. I wholeheartedly agree that lookout is still of overriding importance in Class G airspace. However, I think that it is just as pertinent not to assume that the traffic that you have spotted is actually the contact that TCAS is worried about - which opens up a another whole debate about switching to TA to avoid "nuisance" RAs, particularly in the circuit.

Our TCAS scans +/- 9000 feet and the Above/Below/Normal switch simply declutters the presentation as per the bands described by BEAgle. A squawk that is outside the current band will still trigger a TA or (less likely) an RA if TCAS regards it as a threat - Eg a FJ with a high rate of climb. Non mode C squawks are regarded as co-level and can trigger a TA even if they are 9000 feet below - the lack of Mode C prevents TCAS from screening them out. When military radar say "No Height" do they mean no verified mode C? I would rather be told "..indicating FLxx unverified" so that at least I know to which TCAS contact ATC are referring (probably). Furthermore, I can see no value whatsoever in responding to ATC traffic information with "Got it on TCAS" as there can be no resulting reduction in seperation.

[Pierre Argh]

The "verification" of Mode C readouts by ATC SSR is to allow them to reduce lateral seperation... not quite right, we verify SSR so that we and other colleagues know the information is reliable, but that's not my point. As you quite correctly say, Brain, TCAS will provide a RA based on the Mode C it receives... but it doesn't know whether this Mode C data is correct or not. Unless the squawk has been verified, which in all probability will not be the case with a 7000 squawk, the Mode C data being acted upon in unreliable!!!

[Elmlea]

Let me spell it out for you:

TA: Traffic advisory. Lets you know graphically where traffic is.

RA: Resolution advisory. Provides commands via VSI to achieve vertical separation.

Tucano system will not be linked to VSI as far as I know; it appears to be a standalone dispay. Therefore, It won't be capable of RA. Even if it were, you could select TA mode to avoid nuiscance alerts (e.g. in circuit etc....).

Whoa; not sure what I did to hit such a nerve with this. It reminds me why I normally just lurk! ;)

No expert on TCAS as you've pointed out; but I understand the difference between the two. What I was wondering was if it was possible to generate an RA without a link to the VSI. After all, the TCAS kit must make the decision as to whether climbing or descending is the best plan; so is there any reason why a bit of kit without access to the VSI couldn't suggest "climb" or "descend" in your ear as an RA?

As I mentioned earlier, it is a tool to ASSIST lookout, not replace it. YOU WILL NOT BE FLYING ALONG STARING AT THE FISHFINDER UNLESS YOU ARE TOTALLY STUPID.

The flight regimes that the Tucano operates in at med level will be where it benefits the most (microlites et al no squawking lower down etc).

Wait till you've got a tad of time on the kit, then by all means let us know what you think, but to comment with no knowledge is a tad churlish:hmm:


I've got a couple of token hours on the Tucano with the system installed, and a while it's my first experience of TCAS, I've got a little bit of experience of BFJT students. I know it's a tool to assist lookout, but think of the ab initio stude with 5 hours on the aircraft. He's still struggling to find the capacity to look out at all, inbetween everything else he's meant to be doing and the learning he's meant to be absorbing. My worry was that if you present him with a device which, as far as he knows, shows him the position of everyone around him, he won't necessarily believe his QFI sitting there reminding him that lookout is paramount.

He may think he just has to do a few token head moves, because TCAS will show him when he has to look, and where. The system's not perfect, after all.

[Brain Potter]

Pierre, Understood about verification.
However, I will always follow a TCAS RA regardless of the Mode C verification . The TCAS RA assumes priority over ATC instructions and clearances. The chance of the Mode C being wrong is much smaller than the risk of collision if the RA is not followed. I accept that 7000 Squawks in the UK are unverified, but so are squawks in procedurally controlled airspace. In the recent airprox involoving Hawks v Airliner, the airliner would have manoeuvred to follow any RA issued if the Hawk's IFF had not failed - unverified or not.
I hope this topic has highlighted importance of squawking mode C if you are at all able, even whilst not talking to ATC. As a TCAS user, often in Class G airspace, I wish that everyone would squawk mode C at all times and that a Mode C transpnder was mandatory for all aircraft. I know the GA communtiy would object, but I would feel safer.
I am amazed that any money has been found for TCAS on Tucano though. Every new bit of kit I have seen has been due to legislation changes or UORs. For years our pax carrying ac touted a military exemption from TCAS. We didn't even change our position after the USAF and Luftwaffe had a random mid air between 2 transport aircraft over West Africa (C141 v Tu154) which prompted them to fit TCAS to their large ac. It was always going to take a crash or a rule change for us to see TCAS. Fortunately the Germans said no TCAS, no-entry as of Jan 05 and we were duly equipped.
Ultimately it is a great bit of kit and I would hate to go back to flying without it. Now what about EGPWS!

[ukatco_535]

Brain

when the military say 'no height' they mean purely that. The aircraft has no height information (could be 7000 without Mode C or even just a primary contact)

If the height is unverified (i.e. 7000 squawk with Mode C)- they should say that it is unverified.

[Farfrompuken]

Relax, Elmlea,

As the above average creamie at Linton, as I'm sure you are;) , you'll soon see when his flying goes to pot that he's staring at the scope too much. You'll then be able to debrief him/her accordingly.

I'm sure when they introduced such innovations as TACAN/ADF etc., QFIs like you were concerned about the effect on trainees; 'they may spend all their time staring at the HSI in a desperate attempt to navigate', but funny old thing they actually seemed to cope with such levels of input.

The average BFJT stude is more concerned about performing well on his streaming board. To that end, he/she will be trying to impress their S+L skills ccts, stalling/areos/spinning etc. which all rely on VISUAL flying.

So relax, my friend, enjoy the benefits of TCAS. Don't be a TCAS monkey as I'm sure you won't, but don't be flying around with it switched off or you'll do yourself no favours.