Can I downgrade a Mode S transponder?

Hi All,

I have a Dynon Mode S transponder, and understand that I can't use mode S unless I put in a HEX code and register it with the authority.

I would like to ask if there is a way to downgrade the transponder to transmit Mode C signal instead of Mode S.

The registration process here is a nightmare and a lengthy one. I am not allow to taxi unless I have a transponder, but I can't use my transponder without a HEX code, hence no transponder, no taxi.

Would greatly appreciate if any transponder guru can share your thoughts.
Thanks!
Hank

I don't think anything needs to be done:

Mode S[edit]
See also: Air traffic control radar beacon system § Mode S
See also: Secondary surveillance radar § Mode S
Another mode called Mode S (Select) is designed to help avoiding overinterrogation of the transponder (having many radars in busy areas) and to allow automatic collision avoidance. Mode S transponders are compatible with Modes A & C SSR system.[2] This is the type of transponder that makes the ACAS II (Airborne Collision Avoidance System) and the ADS-B systems function. The format of the messages is documented in ICAO Doc 9688, Manual on Mode S Specific Services.[3]

Why not call up the ground controller on a slow day and ask if they can see you with some arbitrary code... should be all they care about.

Mode C

Please pardon the silly question, but I don't need registration with a Mode A or C transponder?

Registration is not needed in the US but periodic certification is required for Mode C to ensure the altitude reported is correct. Mode A only reports the 4 digit code set in the transponder. Mode C adds altitude information.

It is only when you go to Mode S that aircraft specific information such as call sign or ICAO 24-bit address is sent which is why it needs to be registered.

Because no specific aircraft information is transmitted I would be very surprised if Hong Kong authorities would require Mode A or Mode C registration. What would be the point?

Just my thoughts -- TJ

The "registration" he is talking about is the ICAO 24 bit hex code that is uniquely assigned to each airplane in the world and put into a Mode-S transponder or ADS-B out device.

This is not the Mode-A "squawk" code that is assigned by the controller.

In the USA, this code is right on your aircraft registration.

Hank has the SkyView Mode-S transponder. The transponder will not operate until a IACO code is entered, because this is information a Mode-S transponder must have and encode in every reply. You cannot have the transponder be a Mode-C only transponder- different TSO's apply to Mode-S and Mode-C transponders, so the transponder would need to carry an additional TSO to operate in Mode-C mode, which it does not have.

To use our transponder, you do need to get a code from your regulation authority. There is the possibility that they have temporary or "fake" ones that they will let you use as long as you don't fly internationally, but admittedly we don't have much experience with doing this in areas like China and Hong Kong.

Is it possible for Hank to exchange his Dynon Mode S transponder for a Dynon Mode C transponder? If it exists?

Seeing as you have been allocated the tail number "B-KOO" the authority should be able to give you the corresponding 24bit code. I don't think there is any more information required to generate the code.

See more information here: http://www.kloth.net/radio/icao-id.php

scrollF4 said:

Is it possible for Hank to exchange his Dynon Mode S transponder for a Dynon Mode C transponder? If it exists?

Click to expand...

Trig/Dynon don't offer a mode C unit.

Doug said:

Seeing as you have been allocated the tail number "B-KOO" the authority should be able to give you the corresponding 24bit code. I don't think there is any more information required to generate the code.

Later: I did a bit of googly and based on information here: http://www.kloth.net/radio/icao-id.php I think your code MAY be something like:

Click to expand...

Different governments assign ICAO codes differently. In the USA you can figure out your ICAO from your tail number, but that's just the way we did it. Nothing that says the local authority can't give them out in order of people's registrations with no regard to the tail number, and they could require other paperwork to be completed to do so.

I looked on that page and didn't see an algorithm for China. While all China registrations will start with the bits 0 1 1 1 1 0, only they can tell you how to fill in the next 18 bits. That's not to say that there isn't a algorithm to go from tail to ICAO, but that doesn't inherently mean it's OK to type that in and use it if your local government requires registration to do so.

You are correct - I retracted.

Hank, do you know Martin Haraldsson at Tag? He could definitely help you with the registration hurdles, at least regulatory and documentation wise. Let me know if you need his contact info.

GOT IT

Thanks guys! In Hong Kong, all local light aircraft does not get assigned with a ICAO24/HEX code......EXCEPT aircraft in the international airport. The government automatically assumed we are light aircraft flying locally so they denied our application in the first attempt. We re-submitted our application and it seems we are able to get it, so no drama after all.

Thanks all for the input and suggestions!
Hank

Yay!