Question about transponder regulation

[Rimshot]

Howdy folks,

Today I was studying for my PPL exams and in a chapter about Radar I read it is obligated in Europe to have a Mode S transponder on board. Does anyone here know if the same regulation applies for the USA?
I'm asking because of all the FSX aircraft modelled with only mode A/C transponders, for instance the Carenado Cessna 152 and 172N.

Cheers,
Bert

[spotlope]

Howdy folks,

Today I was studying for my PPL exams and in a chapter about Radar I read it is obligated in Europe to have a Mode S transponder on board. Does anyone here know if the same regulation applies for the USA?
I'm asking because of all the FSX aircraft modelled with only mode A/C transponders, for instance the Carenado Cessna 152 and 172N.

Cheers,
Bert

Some of the more experienced members here will correct me if I'm wrong, but I believe you're only required to have a transponder in the US for operating within Class A,B, and C airspace.

EDIT: I was focusing on the transponder bit, not Mode S. I recall mode C being required in A,B, and C airspace, but I'm not sure about mode S.

[Brett_Henderson]

Obviously, a transponder is required for IFR, and VFR flight following.. and VFR entrance into 'B' & 'C' airspace (not 'D').

Mode-C, is altitude reporting.. and I haven't seen a non Mode-C transponder since I can remember.

In addition to entering 'B' 'C' airpspace.. you have to have an altitude reporting transponder active (even if squaking 1200), to get within 30nm of a class 'B' airport... There's a BIG line showing this on a VFR sectional.. see attachemnt for the SW corner od KDTW..

[fliger747]

Mode S transponders talk to each other. What they do is determine a rate of closure in both altitude and plan. If there is a potential conflict on will get an aural message "Traffic, traffic" and the display will turn the displayed aircraft yellow. If there is a definite colision risk, the displayed aircraft will turn red and a resolution advisory will be annunciated such as "Climb, climb now" etc. Once the risk is passed "Clear of conflict" is annunciated.

Often our closure rates are over 1000 mph and it is very difficult to judge the relative altitude of approaching aircraft due to cloud decks and the curveature of the earth. At night it is almost impossible.

Cheers: T

[Bone]

Mode-S transponders are not required in the U.S. , and Brett Henderson is right about mode-C transponders being required in certain airspace. Fliger is right, too, and the description he gave includes TCAS. Mode-C interfaces with TCAS in the same manner in which Fliger describes.

[ryanbatc]

Obviously, a transponder is required for VFR flight following..

Not neccesarily hehe ;) I've provided radar advisories to non xpndr-equipped acft before. All you do is identify them then ask them their altitude and altitude climbing to (or descending to) and tell them to advise of any altitude changes.

[Brett_Henderson]

Not neccesarily hehe ;) I've provided radar advisories to non xpndr-equipped acft before. All you do is identify them then ask them their altitude and altitude climbing to (or descending to) and tell them to advise of any altitude changes.

Wow.. I wish there were more ATC guys around like that.. Normally they seem bothered when you ask for VFR-flight-following.. let alone help an nont-transpondered aircraft..

But I have to ask.. what you're talking about is from a 'D' tower.. right ? Not genuine flight-following as to be passed from one controller to another ..?

[ryanbatc]

But I have to ask.. what you're talking about is from a 'D' tower.. right ? Not genuine flight-following as to be passed from one controller to another ..?

Essentially, yes, in busier C and B you need a mode c like you wrote above. But in D and E feel free to ask for advisories even if you don't have one.... Now, granted, the centers have limited radar coverage at lower altitudes and sometimes the quality of their radar isn't the best so they may not be able to radar identify you without a xpndr (it can actually be quite difficult to tell a primary target apart from a flock of geese hehe). The easiest way I ID planes is through secondary means - have the pilot "ident."

Actually I'm going to clarify the class D and E thing...

I work tower and tracon positions and our airspace is uncontrolled except a few E areas and of course the tower which is indeed D. So VFR's can come and go as they like as long as they are outside of the 5mi ring or above it (roughly 4000 ft msl). IFR's need to call us if they want service in the lateral and vertical limits our of airspace no matter what. Since our radar coverage is based on the ASR on the field we have fairly good radar capabilities in our tracon. So it's not too hard to distinguish an aircraft without transponder from a flock of geese. Somedays are better than others though hehe.... just today a guy called about 30 SE of the airport, wanting advisories to a destination about 50 NW. We could not see him on radar until he was on the other side of the main airport lol. It was a C152 I think... tiny and sometimes hard to see without xpndrs. Nonetheless we picked him up (and his xpndr started working lol)

You're right about VFR flight following with an ARTCC over a large area.... you really need a transponder for this operation. However, it is possible to preform a manual handoff between facilities with a "no-box" aircraft :wavey:

[Ken Stallings]

Howdy folks,

Today I was studying for my PPL exams and in a chapter about Radar I read it is obligated in Europe to have a Mode S transponder on board. Does anyone here know if the same regulation applies for the USA?
I'm asking because of all the FSX aircraft modelled with only mode A/C transponders, for instance the Carenado Cessna 152 and 172N.

Cheers,
Bert

Mode S is not required in the US.

You are required to have an operating transponder if you are inside Class B, C airspace or operating at or above 10,000 feet MSL unless you have permission from the controlling ATC agency to fly without it.

Inside the controlled airspaces, either Mode C or S will suffice.

Cheers,

Ken

[Ken Stallings]

Some of the more experienced members here will correct me if I'm wrong, but I believe you're only required to have a transponder in the US for operating within Class A,B, and C airspace.

EDIT: I was focusing on the transponder bit, not Mode S. I recall mode C being required in A,B, and C airspace, but I'm not sure about mode S.

Add in the requirement for flight at or above 10,000 feet and you are correct. Need working altitude encoding for A, B, and C. Class A because you must be on an IFR clearance to operate there.

Rules are still very permissive in the United States compared to most of the rest of the world.

Cheers,

Ken

[Ken Stallings]

Oh, something no one has yet mentioned is you are required to have the transponder with altitude encoding for ADIZ operations, inside, to, and out of.

Ken

[tigisfat]

The requirements for transponders inside certain airspaces in the US can be waived with a phone call. I used to ferry a friend's non-electrical equipped cub, and I'd call up the approach and tower folks and get my clearance and instructions from a telephone.

If you're gonna do so, it's only polite to have precisely planned the flight so they know where and when you'll pop up. If something changes, land or fly low and call again.

also of note: most class B airspace has a 30nm ring around it which requires mode C altitude encoding even when not directly in said airspace.

There was an old type of Mode C, the modern 4096 code type is now required.

[fliger747]

Mode S is not required for everyone in the uS, but we are required to have them! 747-400.....

T

[Tylerb59]

Not neccesarily hehe ;) I've provided radar advisories to non xpndr-equipped acft before. All you do is identify them then ask them their altitude and altitude climbing to (or descending to) and tell them to advise of any altitude changes.

How are squawk codes determined, btw?

[Rimshot]

Good to read I do not have to swap transponders with only A/C mode for an S mode type on all my virtual aircraft in the USA :)

[fliger747]

My Supercub has to have a Mode C because of the nearby International Airport who's airspace I must intrude on to takeoff. They do with some graciousness allow on ocassion not transponder, or non mode C aircraft to transit.

Cheers: T

[ryanbatc]

How are squawk codes determined, btw?

Random mostly... In some facilities they'll have "local codes," like a block of codes for certain purposes. Say if you only want advisories through my airspace you'll get a 0300 code (ie 0301-0377) since you would be VFR. Cirrus Design uses a 0200 code block while IFR aircraft staying within out airspace get 0400 codes... It varies by facility.

[Ken Stallings]

Random mostly... In some facilities they'll have "local codes," like a block of codes for certain purposes. Say if you only want advisories through my airspace you'll get a 0300 code (ie 0301-0377) since you would be VFR. Cirrus Design uses a 0200 code block while IFR aircraft staying within out airspace get 0400 codes... It varies by facility.

Some squawk codes are fixed to define a specific situation, most frequently used in 1200 for VFR flight. However, others are used for radio out or other emergency situations.

Ken

[Ken Stallings]

Mode S is not required for everyone in the uS, but we are required to have them! 747-400.....

T

I presume that is because of being a commercial operator?

Ken

[ryanbatc]

However, others are used for radio out or other emergency situations.

Ken

Yes I forgot to mention those... I'm thinking everyday codes... mainly they just go in chronological order for the acft which requires one next....

[SkippyBing]

In the UK the first two digits of the transponder code indicate who the controlling agency is with the last two for them to allocate as they see fit. For example RNAS Yeovilton uses 02XX this means the neighbouring ATC providers such as Bournemouth, Bristol and Cardiff know who's controlling the little dot getting ever closer to their CTZ!