Probability of conflicting traffic?
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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.
"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.
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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.
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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!
Before this, I thought see and avoid was ok..."big sky, small airplane". Not any more!
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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.
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.
Last edited by IO540; 5th Dec 2005 at 10:49.
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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
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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.
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?
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.
But that assumes that the transponder is the only piece of equipment being powered.
Going back to ADS-B, interesting stuff particularly on VDL Mode 4 at EGOA. I thought VDL Mode 4 was virtually written off after the FAA rejected it, but it seems like there's still interest.
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I think everyone has missed the point (bar Ghengis)
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.
This forum is provided free for all kinds of reasonable debate, not to call someone a 'tw@t' as you put it.
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
Last edited by BRL; 6th Dec 2005 at 20:56.
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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.
Avoid imitations
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"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.
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.
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A cursory search reveals WarmWind's true colours. Please do not feed the trolls.
To anyone tempted to respond: The 'Ignore List' facility works a treat. Please use it and not spoil this wonderful thread.
Avoid imitations
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So, warm wind as in flatulence..... 
?
OK, he's ignored.
?OK, he's ignored.
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FORGET TCAS
There is NO SUBSTITUTE for good LOOKOUT. EVER."
There is NO SUBSTITUTE for good LOOKOUT. EVER."
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.