Mode S transponder near Class Bravo

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flyingvet

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flyingvet
Hello,

I have an experimental airplane equipped with a Dynon Mode S transponder and ADSB in/out. To be within 30 miles of a class B airspace, the regulations state that a Mode C transponder and ADSB is needed.

I can't find the answer to this anywhere, but am I allowed within the 30 mile radius of a class B airspace? Mode S gives more information out than the Mode C, so I think it should be fine. Does anyone have a definitive answer?
 
Mode S transponders (including this one) respond to Mode A and C interrogations.
 
flyingron said:
Mode S transponders (including this one) respond to Mode A and C interrogations.
Click to expand...
I'm not sure if I understand your answer. Can I or can I not use it within 30 nm of Class Bravo?
 
I believe you can get an override or exemption if you call ATC. I’ll let someone else chime in.
 
You need at minima an altitude encoding transponder, which the mode s would satisfy. But it also gives speed and registration.

Dad's plane has the Dynon mode s and we're based in the Ohare mode C veil.

Fly on.
 
§ 91.215 ATC transponder and altitude reporting equipment and use.
(a) All airspace: U.S.-registered civil aircraft. For operations not conducted under part 121 or 135 of this chapter, ATC transponder equipment installed must meet the performance and environmental requirements of any class of TSO-C74b (Mode A) or any class of TSO-C74c (Mode A with altitude reporting capability) as appropriate, or the appropriate class of TSO-C112 (Mode S).

b) All airspace. Unless otherwise authorized or directed by ATC, and except as provided in paragraph (e)(1) of this section, no person may operate an aircraft in the airspace described in paragraphs (b)(1) through (5) of this section, unless that aircraft is equipped with an operable coded radar beacon transponder having either Mode A 4096 code capability, replying to Mode A interrogations with the code specified by ATC, or a Mode S capability, replying to Mode A interrogations with the code specified by ATC and Mode S interrogations in accordance with the applicable provisions specified in TSO–C112, and that aircraft is equipped with automatic pressure altitude reporting equipment having a Mode C capability that automatically replies to Mode C interrogations by transmitting pressure altitude information in 100-foot increments. The requirements of this paragraph (b) apply to—

1) All aircraft. In Class A, Class B, and Class C airspace areas;

(2) All aircraft. In all airspace within 30 nautical miles of an airport listed in appendix D, section 1 of this part from the surface upward to 10,000 feet MSL;
 
Yes, you are fine with mode S. Mode C is the minimum. Mode S is more advanced.

Edit- just noticed George answered your question.
 
Think of a Mode S transponder as a superset of a Mode C transponder. If Mode C is required, mode S meets that requirement (and then some).

- Martin
 
Mode A just responds to ATC radar to give position
Mode C is Mode A plus adds altitude in the response
Mode S is Mode C plus adds ID and speed

If A is required, C and S also meet the requirement.
If C is required, C and S meet the requirement
If S is required, only a S transponder will meet the requirement.
 
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