Probability of conflicting traffic?

[Mariner9]

Somebody on a recent thread stated that in his/her view, see and avoid was a load of hogwash, and that collisions were primarily avoided by the statistical unlikelyhood of flight paths converging.

That got me thinking about the number of times that I've seen conflicting traffic, and had to manoever to avoid it (apart from joining/in the circuit). As far as I can recall, that has only happened to me on three occasions in my 170-odd hours (each of which was a conflicting glider as it happens) :mad:

There was also one occasion where I didn't see conflicting traffic approaching until the last second when it flashed past on a reciprical course about 100' to port same level (if you flew a Rockwell Commander near Goodwood last July it could have been you) ;)

There's also a chance that I have also been in near-conflicts that i haven't seen at all :oh:

Assuming I have seen everything, on the basis of my observations we might expect to be in a conflict situation every 40 hours or so. However, the majority of my flying hours are in the S. West, with only 30-odd in SE bandit country, where given the increased traffic density, conflict chances are likely higher.

Anyone care to add their experiences to see if we can come up with an average?

[englishal]

I've had a number.....1 in 40 hours sounds about right, I had one during my PPL which was opposite direction, about 100m right, same level......

I was flying a G1000 aircraft with Traffic display in the US a few weeks ago, I realised that the traffic I saw compared to what was on the screen was about 30%....The nice lady informing me of "traffic traffic" went off a number of times......:oh: Sods law says that the traffic is ALWAYS converging......

Damn useful device, shame its not available here...

[Genghis the Engineer]

I can say with certainty that there are at-least two occasions in the last 1000hrs when see-and-avoid in VFR saved my neck.

1 in 500 hours is pretty significant by my count.

G

[High Wing Drifter]

Somebody on a recent thread stated that in his/her view, see and avoid was a load of hogwash, and that collisions were primarily avoided by the statistical unlikelyhood of flight paths converging.
In 200 odd hours I can recall the need to avoid five times; three were very close and to be honest one was so close and quick that we flashed past each other before either got a chance to react and that was over WCO, an early lesson in not flying over landmarks or beacons!

After seeing Farnborough's radar screen, I'm much resigned to the fact that I simply have not seen at least half the traffic that was probably visible to me, and I reckon I'm pretty diligent when it comes to lookout.

[hugh flung_dung]

Quite a few near'ish (usually gliders) and 1 VERY near - maybe 2 spans away, passing at 90 degrees L-R, 28/Aug last year, N of Bournemouth, T tail (PA38?) :mad: - in a few thousand hours.

I'm a believer in the "big sky small aeroplane" theory, lookout is important and helps but it cannot fully protect you.

One common failing with students when they see a close "bogey" - they don't turn towards so they can keep it in sight.

HFD

[IO540]

Those you spot are not on a true collission course.

An aircraft on a true CC will appear completely stationary. In 600hrs I've never had one of those (evidently, as I am writing this) but have seen plenty which I felt a need to avoid. They might have missed by 50-100m, which looks very close.

The only foolproof solution, for those who think it's worth paying for, would be mandatory Mode C and TCAS.

[Saab Dastard]

I've had one VERY VERY close one in a little over 100 hours. Were it not for the mark 1 eyeball and quick reactions on the part of the FI sitting in the RHS I would not be here today.

That was SE England, not far from Pulborough, at about 2500 feet, >10K vis. about 3 years ago.

As IO540 says, the ones you don't see are the ones that will hit you!

The FI (not me) estimated that we missed by less than 30 feet - and that was AFTER taking last-second avoiding action (we dived, just as well the other aircraft didn't).

SD

[IO540]

Flying around MID at 2400ft is not a lot better than flying in a circuit :O

Otherwise, if one flies around at reasonable levels, say 3500ft+ rather than 2000ft where a lot of people like to sit, there is very little traffic.

Abroad I fly at 8500/9500 or higher. Best MPG is at 8500 or so.

One can get very hung up about this. Statistically there is no support for it though, and I would never pay the £15k-20k for a TCAS. Especially not until transponders are mandatory. A radar altimeter, less than half the price, for those DIY approaches into [name your favourite English/Welsh airfield with a perpetual cloud cover and a dodgy NDB] would be a lot better :O

[booke23]

I'm surprised you got back to the airfield with your pants still clean saab after the 30ft incident!

In my 100 hrs I have not had any close calls like the above. Although I was flying north of Bournemouth one Sunday a few weeks ago and had to turn to avoid 3 aircraft in 40 mins. All at the same level, closest was about 200m horozontally....although we both had seen each other.

It's very true that it's difficult to see aircraft on an collision track......I also know that alot of collisions happen because one or both aircraft were in each others blind spots.

I always try to keep a good lookout, but theres alot to be said for climbing higher.......I find that even at 4000ft theres much less traffic.

Also I usually talk to the nearest radar unit if I can.......they can be a good help at times. If I'm flying from A to B in a straight line I'll ask for a RIS......Although often it's easier said than done getting a RIS!!

[Johnm]

I've had two fairly close encounters both with gliders in my 300 odd hours.

I also fly as high as I can and choose odd levels eg 2200 ft or 1900 ft in the crowded SE where TMA is down to 2500 and many seem to pick 2000 or 2400.

One interesting observation from an IMC holder, flying North about 500ft above a thin layer of Stratus with a RIS I got a lot of opposite direction traffic info and never saw any despite a careful look out for it (and pop up traffic). I can only assume it was below the layer and I was above. It's safer on top:mad:

[chevvron]

Climbing out of Halton in an AX3 passing about 2000ft, just turned to go down the valley towards Amersham when a Citation appeared from over my right wing (classic blnd spot) and turned left to cross in front of me, cunningly keeping his reg from my view. it seemed close, but was probably 300m or more. Obviously he'd seen me, was he 'carving me up' I wonder?

[stiknruda]

This year's end of season display pilots' seminar had a very interesting presentation about this entire subject.

In short, I'll tell you what my chum and I were so amazed by that we even talked about it on the way home....

Statistically, by a huge factor, most air to airs happen in the circuit. Of those 60% are run down from behind - Mrs Breakneck you may have a point, so I suggest that you acquire a faster aeroplane!

Stik

[Laundryman]

I'm running at about 1 in 25 to 30 hrs three this year each time the same flying school (big well known organisation too) they teach a lot of commercial pilots so maybe these guys have got their heads down practicing IFR. It does make me apprehensive in case I miss seeing one until too late. Always ask my passengers to keep a sharp eye out, its good to have to pairs of eyes on the job even if they are in the same aircraft.

[IO540]

The problem is that lookout has a limited effectiveness.

I've often flown under an RIS, with 3 passengers, and we were all looking out for traffic reported to us. Most of it we never saw.

Also, at best, the angle of view from a cockpit is limited. You could be going at 100kt and another plane descending at 180kt could fly into you from say your 4 o'clock.

People don't like to be told that the "old Mk1 eyeball" (to quote the traditionalists) is actually pretty useless....

In reality, mid-airs are extremely rare. If they were common, something would have to be done about it. Just as well, since most people really do believe that keeping a lookout avoids hitting something. Those that you spot (and perhaps try to avoid) would nearly always not have been on a true collision course anyway.

The only potentially effective way is mandatory Mode C transponders, and TCAD/TCAS which starts at about £15k. Even then, you won't spot most of the reported traffic but at least you can take your own avoiding action.

I agree the circuit is the most dangerous place. Which is why I don't like overhead joins. One is asking several pilots at once to all head for the same area, all at 2000ft AGL. Usually, one cannot spot all of those who are known (from the radio) to be arriving at the same time. In those conditions, I've aborted the join and came back later. But there isn't a solution to this, if several planes really do arrive at the same time. Not under VFR. Under IFR you just put them into holding patterns so in effect they are doing overhead joins but at different levels :O

[High Wing Drifter]

IO540,
The only potentially effective way is mandatory Mode C transponders, and TCAD/TCAS which starts at about £15k. Even then, you won't spot most of the reported traffic but at least you can take your own avoiding action.
I think this would create more problems. I agree that technology solves IFR problems, but remain suspicious that for plain old vannilla VFR, technology seems to add complexity and procedures for dubious returns. As has been said, most mid airs are in the circuit and any half decent TCAS system would be going absolutely banannas as it approaches the ATZ! Yes you can switch it off, but that is another line to the checklist, something else to miss and something to distract. TCAS is a good idea for an airliner where seperation is ATC maintained 99.73% of the time and any Resolution Advisory is a rare eye-widening event. For the VFR bimbler in the open FIR you can fly pretty close once viz is established without feeling in danger and Resolution Advisories would be common place and needless in most cases. I'll wager that it would become next to friggin useless once you have tired of the number of alerts vs the number to real potential VFR conflicts.

[DubTrub]

I find that even at 4000ft theres much less traffic At 800 feet there's even less. And before someone mentions the military...:hmm:

Also, never fly at "exact" height/altitude, and never over a VOR or NDB honeypot.

[funfly]

I've often found myself looking at an aircraft approaching from my left (say at 10 or 11 oclock) and maybe heading towards me or across in front of me although not necessarily on a collision course - maybe at a different height.
The rules of the air say I should turn to my right but that assumes he will also move to his right. In my experience these aircraft zoom past and don't seem to have spotted you at all so what would others do in this situation?

[MichaelJP59]

Which is why I don't like overhead joins. One is asking several pilots at once to all head for the same area, all at 2000ft AGL. Usually, one cannot spot all of those who are known (from the radio) to be arriving at the same time. In those conditions, I've aborted the join and came back later. But there isn't a solution to this, if several planes really do arrive at the same time. Not under VFR.

I often worry about this. Someone reports overhead join, descending on deadside, but you have no real way of knowing where they are if you're also approaching.

So far I've tended to wait until I think it's clear, but once I reported joining overhead and someone else did a few seconds later. Just carried on, but I did feel as though I was trusting to luck even though I was keeping a look-out. There are plenty of blind-spots even on a good visibility aircraft.

[Penguina]

Statistically, by a huge factor, most air to airs happen in the circuit. Of those 60% are run down from behind

Where you just don't stand a chance of saving yourself. :(

I've had a couple in my 150 hours. One was indeed in the circuit, in bad viz and it persuaded me not to be such a silly billy and continue flying in such weather!

The other was very lucky indeed. Finding the cloudbase seemed to be lowering a bit, I descended 100ft or so to be on the safe side. 30 seconds later someone emerged from the cloud roughly at the height I had been maintaining previously. :eek: :uhoh:

On neither occasion would my eyes have helped me, I'm afraid to say.

[ShyTorque]

Highwingdrifter,

"I think this would create more problems. I agree that technology solves IFR problems, but remain suspicious that for plain old vannilla VFR, technology seems to add complexity and procedures for dubious returns. As has been said, most mid airs are in the circuit and any half decent TCAS system would be going absolutely banannas as it approaches the ATZ! Yes you can switch it off, but that is another line to the checklist, something else to miss and something to distract. TCAS is a good idea for an airliner where seperation is ATC maintained 99.73% of the time and any Resolution Advisory is a rare eye-widening event. For the VFR bimbler in the open FIR you can fly pretty close once viz is established without feeling in danger and Resolution Advisories would be common place and needless in most cases. I'll wager that it would become next to friggin useless once you have tired of the number of alerts vs the number to real potential VFR conflicts."
------------------------

Sorry - but have you ever flown an aircraft equipped with TCAS or received instruction in its use? Because you are 100% WRONG! I fly a commercial helicopter thus equipped. We are required to fly in Class G most of the time, often IFR or changing between IFR/VFR or vice versa. We do NOT, repeat NOT use RA mode but TA mode only. To be honest, I don't EVER want to go back to flying without it because I know how good it really is.

I don't understand your point about TCAS distraction - if you are possibly about to have a mid-air collision - what else is more important than knowing about it and acting to avoid it? NOTHING!

Judging by the number of times that we encounter other aircraft and hold right of way i.a.w. the Rules of the Air, but have to take serious avoiding action because nothing is done by the other pilot, TCAS very certainly helps us spot conflicting aircraft MANY times more often than other pilots spot US. We carry extra white strobes and HISLs and switch on the forward facing searchlight when appropriate, but it IS most often US taking the avoiding action.

Once you have used TCAS for some time you begin to realise just how many aircraft there REALLY are out in class G and how often you potentially get very close to other aircraft. There must be a lot of pilots flying around UK in blissful ignorance - because they don't SEE all the other aircraft they asssume they just aren't there! :ok:

[wbryce]

In 85 hours I have had none!

I dont tend to fly at the most common heights...and I fly in Scotland where GA is probably some what less busier and less compact than the United States of England...

[Say again s l o w l y]

I have to agree with ShyT about TCAS, it is a fantastic tool and once you have used it, you don't really want to fly without it.

It was critical at my last company as we would often be returning to base after 9 in the morning and would usually try and get descent OCA to try and speed things up for our return, rather than being left very high until the last minute causing us to have to scream down.

When you are doing over 200kts at around 3000' OCA, then you really don't see an awful lot of traffic, TCAS was utterly invaluable for helping us pick our way back in safely. If we didn't have it fitted (tight wad company!) then we would never risk taking an early descent even if it was gin clear with two crew keeping their eyes open. (We were supposedly IFR as well.........)

[High Wing Drifter]

Now you see, if I hadn't posted such a comment I would never have got such a detailed response :ok: Only ATPL level thoery here. I'm keen to know what I am wrong about though. An RA in controlled airspace must be reported, so they are taken pretty seriously. If you turn RA off, then you have a potentially more complex situation perhaps? Its fine if you are the only bod for miles using TCAS at 2500' in and around Farnborough (possibly a bad example because of the number gliders), but if everybody else (the original point) was flying about in Class G with TCAS in TA mode only, how exactly would the multitude of warnings be resolved? Just more possibility for somebody to misinterpret the screen and climb when they should be descending. Also, you said it, "commercial", you are properly trained and well practiced in its use. If we all had TCAS then would that really be the case?

I really understand if you are fast traffic, the sitaution is different, but the point IO540 was making is that we should all have TCAS, that is my point of contention.

Although the visual lookout is inefficient, I'm not sure it is neither ultimately ineffective nor inappropriate for VFR. Also, the lookout is proactive activity. I personally think that technology could lead to a more reative approach to flying. I can't see how that can be a good thing.

[IO540]

HWD

I never said everybody should have TCAS. It's 15 grand or so, min, for the cheapest systems that give azimuth (essential).

I didn't even say everybody should have a Mode C transponder (I do actually think that).

What I have been saying is that the benefit of a lookout is illusory [hears the sound of windows at CAA Gatwick and Kingsway opening and the entire GA Dept jumping out] and that if one is after a solution it has to be TCAS, and obviously that will never work properly until Mode C is mandatory.

Luckily for most, midairs are very rare so, for the typical GA "low value payload" (you or your granny) there is very little reason for spending the money.

And even if you do spend the money, it won't pick up maybe 50% of traffic because they don't have transponders or have them switched off, intentionally or not.

Those commercial pilots here swearing blindly how wonderful TCAS is must be aware that they are missing a lot of stuff :O

I would bet that below say 2000ft > 50% don't transpond, especially self fly hire pilots. Higher up it will be a lot better. Most owner-pilots that go distances switch on Mode C religilously.

I wonder what will happen in 2009. What will they do about e.g. gliders and vintage planes with no electrics?

It doesn't bother me; everything in life is a risk and the sky is big and is 3D. I just don't like to bet against known odds, like joining overhead with 5 others, of which I can see just 2 :O

[ShyTorque]

HWD,

The TCAS fit we use doesn't have the facility for the pilot to select RA, it's in permanent TA only.

Multiple TCAS conflicts are dealt with in exactly the same way as multiple visual conflicts in VFR - usually you LOOK out of the window and make a decision which avoiding action is most appropriate.

TCAS prioritises an alert on one aircraft, which may or may not be the most appropriate one, from personal experience. It may give a "false" alert if there is no mode C return. These are the frightening ones as the pilot doesn't know where to look to resolve the conflict - it could be same level, below or above him - and the azimuth may or may not be accurate - so it could be left OR right of the nose! (It might easily be up to 2700 feet above or below on our type, depending on the "airspace" setting).

I wish we could dispel the common trap of thinking that we "lucky TCAS folk" rely on it solely and fly around "heads in" because of it. We certainly don't - if anything TCAS gets a pilot's eyes OUTSIDE the window; those little white dots on the screen are a constant reminder that there are other aircraft in the vicinity!

I personally fit the TCAS instrument display into my normal lookout scan because LOOKOUT remains the primary method of collision avoidance - the ANO says so, as well as an experienced pilot's own common sense. Obviously, not all aircraft have a transponder in any event, so it would be a very unwise pilot who doesn't look out.....

As I said, TCAS isn't reliable enough in azimuth to depend on it in isolation. It IS very good in reporting altitude of other traffic, provided of course that the other traffic has a serviceable Mode C in use, so it's always best to resolve a potential conflict by altitude separation if possible.

That's why I tend to have a bee in my bonnet about permanent use of Mode C if it's fitted and paid for .... it's a potential lifesaver for both parties. If you have Mode C, please use it in the circuit too, unless ATC request otherwise because then we can "eliminate your aircraft from our enquiries". Ta. :ok:

One more point: TCAS helps a pilot to be MORE pro-active, not reactive. If you are aware of an aircraft 20 miles or more away you can obviously do something about resolving a potential conflict FAR more easily than if you are obliged to rely on lookout alone, which will result in an aircraft being "spotted" much later / closer in average conditions.

I began flying for my living in 1977 and have been doing so continuously ever since (RAF jets / Support helicopters / QHI / Heli Display pilot / Military QFI SEP / Heli SAR S.E. Asia / UK Police / VIP corporate). I've had some pretty close shaves during all that and I KNOW the limits of the human eyesight (even though I still have 6/5 vision outside the cockpit). Anything that helps me out is a bonus, as far as I'm concerned. Anyone who thinks that sole reliance on the vagaries of the human eyesight is the only good way, is sadly misguided.

[englishal]

Traffic info is excellent. You can see if you're going to be ramed up the a*se and from those places that you can't see. For example a biz jet was descending from my RH side above the wing of a 182, and I could see them coming on the traffic display but not visually . No doubt they had TCAS anyway, but assuming they hadn't and hadn't seen us.........

It is ok in the circuit, makes it easier to see where numbers 1,2 and 3 are, and it doesn't distract....

Cheers

[High Wing Drifter]

Fair doos chaps. I know when I'm beat :ouch: :O

[ShyTorque]

Not the intention to beat you HWD, just hope you understand :ok:

[chrisN]

" . . . TCAS isn't reliable enough in azimuth to depend on it in isolation. "

Just for info - what sort of things go wrong? Does anyone know why? Will it improve with 100% Mode C/S carriage, if/when that happens including gliders etc.?

If not, what would be needed to improve TCAS to be 100% reliable, if anything could?

Chris N.

[Say again s l o w l y]

For a start, everything in the air to have a Mode C transponder and actually turn it on!

[ShyTorque]

There's a lot of good reading stuff on the internet about the limitations of the "see and avoid" principle. Here's a good link for a start:

http://www.atsb.gov.au/publications/2005/See_and_Avoid.aspx

The .pdf download document at the bottom of that page is very good.

[Mariner9]

Instead of a TCAS for GA, with all the inherent inaccuracy of azimuth, how about a GPSCAS? It surely wouldn't be very hard to develop a GPS that transmitted it's position, and received data from other GPS's for conflict calculations.

The Marine world has something similar already with the Ship Identification system, although that (at the moment) is not used directly for collision avoidance, though it does assist identification of "blips" on the radar and can help avoid the oft-heard RT transmission "ship on my port side, what is your intention?"

[Say again s l o w l y]

Or if we really want to be safe, make everyone fly under a radar control service and get vectored around all the time!

[IO540]

Mariner9

I think it's called ADS-B.

Yes it would be great.

[High Wing Drifter]

Mariner9,

That sounds like ADS-B. This requires a Mode S tranny.

[Mariner9]

Currently requires a mode S tranny maybe, but surely a simple lightweight lowcost (OK that maybe unlikely) GPS transmitter/receiver/conflict detector could be developed. Given the tiny signals that GPS's receive, they presumably would not be required to belt out high power output signals unlike txp's, and accordingly, could work on batteries for non-elec aircraft.

[IO540]

The generation of the position data also requires the prohibited three-letter word, banned by the CAA :O

[robin]

SAS

>>>Or if we really want to be safe, make everyone fly under a radar control service and get vectored around all the time!<<

I really hope that was an ironic comment.

[Say again s l o w l y]

I'll let you be the judge of that...... Do you think I want to suck all the fun out of flying?

It'd be difficult to do a an aero's sequence if I needed clearance everytime I wanted to change altitude or heading!

[bookworm]

Currently requires a mode S tranny maybe, but surely a simple lightweight lowcost (OK that maybe unlikely) GPS transmitter/receiver/conflict detector could be developed. Given the tiny signals that GPS's receive, they presumably would not be required to belt out high power output signals unlike txp's, and accordingly, could work on batteries for non-elec aircraft.

There were three datalink technologies proposed for ADS-B.

1) Use the extended squitter of Mode S (i.e. its capability of sending data along with the response to interrogation)

2) VDL Mode 4 (http://www.eurocontrol.int/vdl4/public/subsite_homepage/homepage.html), a fairly complex system working on a couple of VHF frequencies, but allowing relatively low power systems to work. It was developed in Sweden and has been championed by Eurocontrol.

3) UAT (http://www.garmin.com/products/uat/), a system developed by MITRE specifically for ADS-B and aimed at the GA user. It uses UHF, like the transponder. It's under trial in Alaska (http://www.alaska.faa.gov/capstone/Index.htm) for ADS-B.

The FAA decided (http://www.faa.gov/asd/ads-b/) (also see here (http://www.icao.int/icao/en/ro/apac/2004/cnsmet_sg8/ip15.pdf)) to use a combination of UAT and Mode S (called 1090ES) for ADS-B.

In Europe, since we'll almost all be required to carry Mode S transponders anyway, there's less of a pressing need for development of a low-cost low-power alternative link technology -- though of course there is a pressing need for development of a low-cost low-power Mode S transponder!

[chrisN]

And, for those fairly new to threads such as this, the UK CAA has been promoting a "LAST" - "Light Aviation SSR Transponder" - a lightweight, low cost, transponder which the CAA has been trying to get commercially developed. It has been trialled with varying results over the last few years. I am advised that:

"The present prototypes use Mode A/C analogue technology using an effective power of only 20 watts. While this has produced acceptable results against modern ground installations, many of the existing ground stations have 1970's waveguides and the low power signal gets lost! The present ICAO requirement specifies a minimum airborne transponder power of 70 watts and if the CAA continue to pursue the 20 watt power requirement, then the UK will eventually have to file for 'differences' from the ICAO specification. As cost effective approved 70 watt Mode S aircraft transponders with an acceptable power requirements already exist on the commercial market, the LAST trial might be overtaken by technical advancement. That said, 20 watts or so works well with airborne Traffic Collision Avoidance warning Systems (TCAS) and Mode S ground installations as the receivers/waveguides use modern technology. "

I believe that the CAA is trying to avoid the "file for 'differences' from the ICAO " route by persuading enough other countries to support LAST.

Regards - Chris N.

[cosworth211]

I've had one that near miss that was so close I was concerned in 190 hours. Unsurprisingly it was in Florida. I have been doing most of my hour building at night, when the sky's are emptier at lower levels and conflicting traffic can be spotted much easier.

[PA-28-180]

I had one - actually would have to class as a NMAC. I was heading up to the Nut Tree airport from Buchanan (N. Calif) and weather was CAVU. Used flight following from Travis who released me approx 5 miles SE of the field. Called into Unicom - 2 in the pattern, north runway in use. My intention was to cross over the field at 1,800 then enter the 45. This SHOULD have been enough clearance as the TPA was 800. BUT...there was a warrior on downwind who was at 1,500 - was an instructor/student btw. I NEVER saw the guy until we were 'on' each other! Scared the cr@p out of me. At the time I was doing my IR and for a LONG time after that only flew IFR.
Before this, I thought see and avoid was ok..."big sky, small airplane". Not any more!:sad:

[chevvron]

And where is a glider or microlight going to get the power source for a 20 watt Tx? Surely a lower powered device would be sufficient?

[IO540]

The transponder doesn't draw 20 watts all the time. 20 watts is the RF power which goes to the aerial. Allowing for losses this is probably more like 50 watts power to the RF output stage, but the duty cycle is very low, of the order of 0.01% to 1% depending on how often the transponder is getting pinged.

So the DC power consumption of the transponder will be mostly the power required by the instrument, and this could be as low as (order of) 1 watt, which is peanuts and a small battery would do it.

The problem is lack of imagination and lack of electronics design expertise in the avionics business. Historically, avionics has been designed on the basis that power is not limited (believe it or not). So, we have VHF transceivers that draw 20 watts all the time, panel mount GPSs that draw 30 watts all the time, 4-6" multifunction displays that draw 50 watts all the time. These figures are 10x too high, given the actual function requirements. Then, obviously, we need a dirty great fan behind the avionics stack to get all the hot air out.

A really useful side effect of this ventilation is that all avionics has to have big holes in it so the air can flow through. So, when the plane is parked outdoors in the winter, the moisture gets in really nicely and eats away the circuit board, and anything else. This results in intermittent faults and eventually the equipment is beyond economical repair, because the damage is so widespread, and "repairs" are often effective for a limited period only. Whereas anybody who knows that planes do spend some time outdoors (seems to be a closely guarded secret, known only to pilots) would design the stuff to draw minimal power (basically, only the LCD backlight needs to draw a fair bit, and LCD heaters need to draw power only when the display is errrmmm ... cold) and the equipment would be sealed to IP65 or better.

It's however unlikely that any new company will bother to develop and market a low power transponder. The market will be close to zero until it becomes mandatory, and currently nobody can be sure what will happen in 2009. And if/when they become mandatory for all powered flight then the market will be huge, and any of the existing companies (Garmin being the obvious one) will easily knock up a "low power" unit and will sell it successfully through their existing dealer channel to which avionics shops have a lot of loyalty because of generous trade margins.

The end user doesn't really feature in the picture very much.

Except in the Permit/microlight market where users can buy the stuff mail order and install it themselves. Somebody could do something for that.

[High Wing Drifter]

It's however unlikely that any new company will bother to develop and market a low power transponder. The market will be close to zero until it becomes mandatory, and currently nobody can be sure what will happen in 2009. And if/when they become mandatory for all powered flight then the market will be huge
There is a 2 year transition period is for the phased introduction, although not stated, this must be to help deal with the problems of installing Mode S into aircraft with little or no supply.

[IO540]

The problem with a transition period is that (like at present) everybody will be hoping that it will be eventually dropped, for some classes at least. This in turn will prevent technological solutions emerging.

[bookworm]

And where is a glider or microlight going to get the power source for a 20 watt Tx? Surely a lower powered device would be sufficient?

This has come up before (http://www.pprune.org/forums/showthread.php?threadid=190161&pagenumber=6)

The Filser TRT600 Mode S transponder draws between 0.1 and 0.4 A at 12 V. That is a low power (LAST) device -- 70 W RF power rather than 125 W. A typical glider battery seems to be about $150 and offers ~7 Ah, i.e. power to the transponder for more than 20 hours.

[robin]

But that assumes that the transponder is the only piece of equipment being powered.

[bookworm]

But that assumes that the transponder is the only piece of equipment being powered.

Well if the aircraft already has an electrical system delivering several amperes, it's not much of an imposition to ask it to add a couple of hundred milliamps to that drain, is it? ;)

[High Wing Drifter]

not much of an imposition to ask it to add a couple of hundred milliamps to that drain, is it?
Possibly a case of vertibrae, humped ruminants, straws and structural failure in some cases?

[bookworm]

Going back to ADS-B, interesting stuff particularly on VDL Mode 4 at EGOA (http://www.egoa.se/). I thought VDL Mode 4 was virtually written off after the FAA rejected it, but it seems like there's still interest.

[WarmWind]

Back to the original point...

FORGET TCAS

There is NO SUBSTITUTE for good LOOKOUT. EVER.

Anybody who thinks it's statistically acceptable to not look out because you only have to take avoiding action once every 40 hrs is a liability and should immediately give up flying before they kill somebody.

It only takes one mid air to kill you but more importantly, you will kill someone else.


IO540: The problem is that lookout has a limited effectiveness

This forum is provided free for all kinds of reasonable debate, not to call someone a 'tw@t' as you put it.

[Mariner9]

WW, think that's a bit harsh, many have questioned the lookouts effectiveness but I dont think anyone on here maintains that its acceptable not to keep a good lookout.

[ShyTorque]

"Back to the original point...

FORGET TCAS

There is NO SUBSTITUTE for good LOOKOUT. EVER."

Except in marginal weather conditions or IMC. I would think that no-one fails to look out just because they have TCAS, if that is what you meant.

IO540 is certainly NOT a TW@T. He probably understands the limitations of the human eye a little more than you do.

[bookworm]

ShyTorque

A cursory search reveals WarmWind's true colours. Please do not feed the trolls. ;)

[CPilotUK]

A cursory search reveals WarmWind's true colours. Please do not feed the trolls.

I noticed the same thing Bookworm.

To anyone tempted to respond: The 'Ignore List' facility works a treat. Please use it and not spoil this wonderful thread.

[ShyTorque]

So, warm wind as in flatulence..... :suspect: ?

OK, he's ignored.

[BRL]

The user WarmWind has been thread banned for personal abuse.

[englishal]

FORGET TCAS

There is NO SUBSTITUTE for good LOOKOUT. EVER."
This is not true. It is far safe to engineer in controls rather than rely on procedures.....human nature being what it is.

I read last night in the US AOPA mag about a mid air at a CTAF field in the US. Seminole and SEP, two instructors, three commercial pilots, 4 instrument rated pilots all killed. However if one of the aircraft had had a nice ladies voice shouting "Traffic Traffic" at them, and they had the traffic displayed on the screen I would say that all 4 would still be alive today.

[IO540]

Never in the history of human endeavour have so many gigabytes of text been generated, by so few, and ignored by so many, as in trying to drag GA into the 20th century.