Transponder mode A ... C????

[girard]

I just found and buy an old plane with a mode A transponder. It is still usefull or I should upgrade to C or can I just add an encoder to make it mode C..?? I think the coding in the transmission is different??. there is not much info in the PPL course.

Thank you!



Girard

[ahramin]

What kind of transponder is it?

[Hawkeye4077]

it is possible to add a mode c encoder to your present transpoder. they are pretty cheap to buy and easy to install in a avionic shop. aircraft spurce have them.

One problem you can run into is if your transponder is too old and don't have the ALT option on it then the tech might not be able to install it. Same problem if your transponder is too old and the avionic guy can't find the plan to install it. Basically if your transponder isn't too old there should be no problem.

Here is what I would do before buying the encoder.

1- find out what transponder model you have.

2- look at different encoder model online and find the one you like.

3- Call your avionic shop and ask them if they can install it giving them both your xponder model and encoder model

4- Ask for a quote. (shouldn't take mode than a couple hours to install)

5- buy enoder and have it installed.


Have fun flying in controlled airspace now

Hawk

[Grease Nipple]

it is possible to add a mode c encoder to your present transpoder. they are pretty cheap to buy and easy to install in a avionic shop. aircraft spurce have them.

One problem you can run into is if your transponder is too old and don't have the ALT option on it then the tech might not be able to install it. Same problem if your transponder is too old and the avionic guy can't find the plan to install it. Basically if your transponder isn't too old there should be no problem.

Here is what I would do before buying the encoder.

1- find out what transponder model you have.

2- look at different encoder model online and find the one you like.

3- Call your avionic shop and ask them if they can install it giving them both your xponder model and encoder model

4- Ask for a quote. (shouldn't take mode than a couple hours to install)

5- buy enoder and have it installed.


Have fun flying in controlled airspace now

Hawk

Takes more than a couple hours to install an encoder, unless you are just talking about mounting it. These days paperwork will take a couple hours. To do the job properly time will be needed to find a suitable location to mount the encoder, then it will have to be mounted, plumbed into the static system, wires marked and installed, cct breaker installed, system tested IAW CAR's 571 appendix F(I am guessing to 14,800ft), ELA and Weight and balance ammended, test sheets printed and finally log book entry made.

[Hedley]

Despite what you may read here, installing an encoder
can be a giant pain in the ass.

As part of the encoder installation, you will have to do
leakdown tests on your static and pitot systems. On
an older aircraft, they will leak. Don't be surprised if
you have to rebuild your altitmeter and airspeed
indicators - that's most of a thousand bucks right
there.

And, you will need all new tubing run for the pitot
and static lines. If the tubing to the pitot tube
leaks in the wing, you may or may not have to
completely disassemble and rebuild the wing
to gain access to it, depending upon your aircraft.

All of the above costs big bucks. I would be very
surprised if you could get an encoder installed
for only $1,000. Heck, doesn't Transport charge
$550 just for the major mod form submission?

After all the labour, and tax on the labour, you're
going to spend several thousand dollars getting
mode C.

[azimuthaviation]

If its a mode A transponder then it cant be mode C. If it has a selection for "ALT" then it is mode A/C. If thats the case just throw in an encoder, you may not need a breaker if the transponder has a power output to feed an encoder, also you wont need an ELA if thats the case. When you install it you probably need no more than a "T" fitting and six inches of tubing. Since youre going to get a correlation test done afterwards you can get the leak test done as well. Since these are done every two years regardless of how old the aircraft is then it shouldnt leak and adding one fitting and a length of tubing will not introduce any new leaks. Used encoders are 250 dollars and the W&B amendment is easy as its only one unit, one station number.

If you want to go extra cheap, dont tie the encoder into the static line, just leave it vented to the cabin. You wont have to do a leak test however when u go to get your bi-annuals done it will be more expensive (as your AME will have to tie into the enoder to do the correlation test then to the pitot static system to do the pitot/static leak test)

If the transponder is only mode A, then yeah, gonna cost u some money. May I suggest a Garmin 320A, and SSD 120, two best units out there for their price.

[Hawkeye4077]

Got my transponder "upraded" from A to C. took a morning at an approoved shop. 500$ + cost of the encoder. Most tubing and wire included in the encoder package. they are small an fit pretty much anywhere under the dash.

Your experience may and probably will vary but that's how it went with my c150.

good luck

[culver10]

doesn't Transport charge
$550 just for the major mod form submission?

They do not charge for this, at the moment, do not give them any ideas! I think the fee you are thinking about is the application fee for getting a LSTC.

[Grease Nipple]

If its a mode A transponder then it cant be mode C. If it has a selection for "ALT" then it is mode A/C. If thats the case just throw in an encoder, you may not need a breaker if the transponder has a power output to feed an encoder, also you wont need an ELA if thats the case. When you install it you probably need no more than a "T" fitting and six inches of tubing. Since youre going to get a correlation test done afterwards you can get the leak test done as well. Since these are done every two years regardless of how old the aircraft is then it shouldnt leak and adding one fitting and a length of tubing will not introduce any new leaks. Used encoders are 250 dollars and the W&B amendment is easy as its only one unit, one station number.

If you want to go extra cheap, dont tie the encoder into the static line, just leave it vented to the cabin. You wont have to do a leak test however when u go to get your bi-annuals done it will be more expensive (as your AME will have to tie into the enoder to do the correlation test then to the pitot static system to do the pitot/static leak test)

If the transponder is only mode A, then yeah, gonna cost u some money. May I suggest a Garmin 320A, and SSD 120, two best units out there for their price.

Even if the transponder has a power output the encoder will add to how much current the transponder draws, an ELA will be needed. Not plumbing it into the static system is not an option, pretty sure it is against regs. I would recommend having it done by a professional who will not cut corners, it's your ass up there.

[azimuthaviation]

Not quite.

Unless the install manual specifically calls for tying it into the static line then I dont think theres a regulation that specifies that, correct me if im wrong. The problem with leaving it just vented to the cabin is there will be a lag in changing pressure. However calibration occurs on the ground. Mind you no one would recommend such an arrangement but i can assure you theres a lot of aircraft flying like that in canada.

As for the ELA you will probably not have to amend it if the manual does not have separate values for with or without the power line out. Ive never seen one that did as its rather inconsequential compared to the power requirements for the transponder (its usually a 500mA internally fused power source) and is accounted for already in the maximum current drain.

[Hedley]

I cannot imagine that an encoder vented into the cabin
instead of the static system, even in an unpressurized
cockpit, could possibly be an approved installation.

If nothing else, the encoder will always read 100 feet -
the quantization altitude - higher than the indicating
altimeter (assuming both were perfectly calibrated).
This discrepancy is not good.

You can prove the above to yourself by opening the
static port in flight - note the 100 foot increase in
indicated altitude.

[azimuthaviation]

According to FAA the encoder must be calibrated to the aircrafts number one altimeter. If the quantization altitude can be accounted for on the ground then it should still be ok although how would you test it without a test flight?