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This is a question about FAR 91.225 (requirement for ADS-B-out) and where aircraft with no electrical system will be able to fly.

FAR 91.225 exempts aircraft with no electrical system from many of the restrictions that would otherwise be imposed, as long as those operations are conducted

e(1) Outside any Class B or Class C airspace area; and

e(2) Below the altitude of the ceiling of a Class B or Class C airspace area designated for an airport, or 10,000 feet MSL, whichever is lower.

This question is about e(2). The question is in several parts:

1) Does e(2) prohibit an aircraft with no electrical system and no ADS-B-out from flying ABOVE THE CEILING of underlying Class B and Class C airspace, regardless of altitude, including altitudes above 10,000' MSL?

(Note that FAR 91.225(d)(3), to which aircraft w/o electrical systems do NOT appear to be exempt, already prohibits flight without ADS-B-out BELOW 10,000' MSL above the ceiling of underlying Class B and C airspace.)

2) Does e(2) also prohibit an aircraft with no electrical system and no ADS-B-out from flying in airspace that is above 10,000' MSL but below the FLOOR of an overlying shelf of Class B or Class C airspace? If so, this has very little effect in actual practice-- it appears that only floors of Class B or Class C that are that high are two of the outer Class B shelf areas at Salt Lake City International, with floors at 10,500' MSL and 11,000' MSL.

3) Is there any OTHER airspace-- if so please give a specific example-- where an aircraft with no electrical system and no ADS-B-out is NOT allowed to fly due to e(2), but WOULD be allowed to fly if e(2) were not there in the regulation? For example, all the Class E airspace over the contiguous 48 states that is simultaneously above 2500' AGL and 10,000' MSL? This interpretation appears to be implausible, as noted below.

4) Cutting to the chase, may we simply assume that the restrictions stated in FAR 91.255 (e)(2) ONLY apply within the lateral boundaries of (i.e. within, above, and below) Class B and Class C airspace?

One thing that has to be determined to answer the question, is just what Class B or C airspace is being referenced? There seems to be an unwritten assumption that e(2) only applies within the lateral boundaries of, i.e. in the column of air extending above and below, any portion of Class B or C airspace. As opposed to, say, also applying at some point that is 20 miles away from nearby Class B or C airspace. In most other similar regulations, including FAR 91.225(d)(3), this is clarified explicitly, but not in FAR 91.225(e)(2).

It seems that the "or below 10,000' MSL" phrase in FAR 91.225(e)(2) must be intended to apply ONLY to airspace that is somehow associated with Class B or C airspace, and presumably, more specifically, lies within the lateral boundaries of Class B or C airspace as described in the paragraph above. Otherwise the regulation just wouldn't function at all -- for example no relief would be provided from FAR 91.225(d)(4), the requirement for ADS-B-out in airspace that is simultaneously above 10,000' MSL and above 2500' AGL. Yet the phrase "Except as provided in paragraph (e)" in FAR 91.225(d)(4) clearly suggests that paragraph (e) IS supposed to provide relief from this requirement.

The "designated for an airport" phrase in FAR 91.225(e)(2) is also odd-- usually this phrase seems to be used to designate E2 airspace as distinct from E4 airspace, but that wouldn't apply here.

Might FAR 91.225(e)(2) be intended to apply to all the airspace referenced by FAR 91.225(d)(2)-- the airspace within 30 nm of the airports listed in Appendix D, Section 1? Perhaps requiring that any aircraft with no electrical section and no ADS-B-out stay below 10,000' MSL in all of those 30-nm circles, and also requiring that if any Class B or Class C ceiling exists in one of those circles, an aircraft with no electrical system and no ADS-B-out must stay below the level of that ceiling throughout the entire circle? This would be a much broader interpretation than what the literal language seems to be suggesting. This interpretation is problematic because the FAR 91.225(d)(2), which references the 30-nm circles, doesn't even apply above 10,000' MSL, so there really ought to be no problem with flying above 10,000' MSL in these circles. In which case the prohibition would only appear to apply to a layer of airspace extending from the Class B or C ceiling altitude, on up to 10,000' MSL, and the reference to "below 10,000' MSL" in 91.225(e)(2) would seem to be completely irrelevant. This interpretation seems unlikely.

In short, FAR 91.225(e)(2), seems to be quite poorly-worded, and seems to leave unclear as to whether it only restricts aircraft with no electrical system and no ADS-B-out from a very limited amount of airspace (essentially only above the ceiling of underlying Class B or C airspace, where the airspace below 10,000' is already off-limits to aircraft without ADS-B-out anyway), or whether it affects such a large amount of airspace (including everywhere over 10,000' MSL) that it invalidates all the relief that FAR 91.225(e) was apparently meant to offer to the requirement of FAR 91.225(d)(4).

Links to any existing FAA guidance on this would be appreciated.

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  • $\begingroup$ I don't think there is such a thing as class B or C that is not designated for an airport. $\endgroup$ – TomMcW Jun 19 at 16:00
  • $\begingroup$ Yes, that's why it seems irrelevant to me. $\endgroup$ – quiet flyer Jun 19 at 16:27
  • $\begingroup$ Even though the best answer seems clear on careful study of the regulation, the language is just unclear enough that I wouldn't be surprised if we see some conflicting interpretations from the FAA on this, perhaps ultimately requiring an final answer from the Office of the Chief Counsel. $\endgroup$ – quiet flyer Jun 19 at 17:30
  • $\begingroup$ @quet flyer, what aircraft do you fly? Just curious. I imagine it would take quite a while for a relativily low horsepower tube & fabric airplane to get to12,000 ft to get above the SLC Class B airspace. And then O2 use might be needed if one were to be up there quite a while. Chicago is another airspace with a top of 10,000 ft. $\endgroup$ – CrossRoads Jun 20 at 13:13
  • $\begingroup$ I have some concern that some interpretations of (e)(2) might be construed to prohibit an a/c w/o electrical system from flying above 10,000' MSL if above 2500' AGL, anywhere in the US. The language is very unclear. Hang glider pilots routinely use O2 and so do sailplane pilots, and I've been above 16K in the former and up to 18K in the latter. Also have time in a lightsport plane that may or may not be construed to have an electrical system; guess that's a whole other question someday. $\endgroup$ – quiet flyer Jun 20 at 13:43
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A careful reading of FAR 91.225 suggests that the answers to the questions are 1) yes, 2) yes, 3) no, and 4) yes. So in actual practice, the only airspace uniquely addressed by FAR 91.225(e)(2) (and not already addressed by other parts of 91.225) appears to be the airspace above the ceiling of underlying Class B or C airspace, including airspace above 10,000' MSL, and the airspace that is below the shelf of overlying Class B or C airspace and is also above 10,000' MSL.

In other words, the restrictions imposed by FAR 91.225(e)(2) should only be construed to apply within the lateral boundaries of (i.e. above, below, or within) Class B or Class C airspace.

More expansive interpretations of the meaning of FAR 91.255(e)(2) seem problematic, as suggested in the question.

More expansive interpretations of the meaning of FAR 91.255(e)(2) are also inconsistent with the FAA's past and present interpretation of FAR 91.215(b)(3)(ii), pertaining to where aircraft with no engine-driven electrical systems and no transponders may operate.

This quote from a 2017 AOPA article also further supports the idea that the restrictions imposed by FAR 91.225(e)(2) only apply within the lateral limits of (i.e. above, below, or within) Class B or Class C airspace--

The regulation 14 CFR 91.225(e) allows aircraft not certificated with an electrical system, including balloons and gliders, not equipped with ADS-B Out to operate within 30 nautical miles of a Class B primary airport—basically, within its Mode C veil—while remaining outside of any Class B or Class C airspace. These aircraft can operate as high as 17,999 feet msl except above Class B or Class C airspace; they also can operate beneath Class B and Class C airspace.

However, it would be nice to see some explicit reassurance from the FAA on this regard, since the language of the regulation is really quite unclear.

Here's a link to an outside forum giving my best understanding of the impact of the regulations pertaining to ADS-B-out on aircraft without engine-driven electrical systems, contrasted with the impact of the current regulations pertaining to transponders on aircraft without engine-driven electrical systems.

In essence the key difference appears to be that under the new regulations, aircraft without engine-driven electrical systems and without ADS-B-out will be barred from flying above ANY underlying Class B or Class C airspace, AT ANY ALTITUDE.

Currently, aircraft without electric-engine-driven electrical systems and without transponders are barred from flying above underlying Class B or Class C airspace only up to 10,000' MSL.

Also, under the new rules aircraft with no electrical system won't be able to fly above 10,000' MSL under a Class B or C shelf. The only such airspace appears to be some outlying Class B airspace near KSLC.

( The truth is that the "or below 10,000' MSL" clause in 91.215(b)(3)(ii) seems utterly useless. It seems to have no application whatsoever. Yet the fact that it was carried over into 91.255(e)(2) definitely complicates the interpretation of this regulation. )

Also note that none of these regulations apply to ultralights. Ultralights are considered "aircraft" by the FAA, but are specifically exempted from Part 91 in its entirety. For more, see the related answer In the United States, are ultralights legally considered aircraft?

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  • $\begingroup$ Even though the best answer seems clear on careful study of the regulation, the language is just unclear enough that I wouldn't be surprised if we see some conflicting interpretations from the FAA on this, perhaps ultimately requiring an final answer from the Office of the Chief Counsel. $\endgroup$ – quiet flyer Jun 19 at 17:32
  • $\begingroup$ Related, but not providing an answer to the specific question asked here-- faa.gov/nextgen/equipadsb/research/airspace , aviation.stackexchange.com/questions/55875/… $\endgroup$ – quiet flyer Jun 20 at 12:45
  • $\begingroup$ Future edit-- clarify speaking of the airspace over the 48 contiguous states in the US $\endgroup$ – quiet flyer Jun 21 at 18:18
  • $\begingroup$ Now see related question aviation.stackexchange.com/questions/65812/… $\endgroup$ – quiet flyer Jun 21 at 18:46
  • $\begingroup$ Possible future edit-- After paragraph "( The truth is...", add another paragraph stating "One could even go so far as to argue that because the "or below 10,000' MSL" clause" has no actual effect in 91.215(b)(3)(ii), it ought to be construed to have no effect in 91.225(e)(2) either, and ought not be construed to limit overflying Class B or C airspace above 10,000' MSL, or to limit underflying Class B or C airspace above 10,000' MSL. However this argument seems quite a stretch, in the absence of direct confirmation from the FAA. that the regulation should be read this way." $\endgroup$ – quiet flyer Jun 22 at 11:56

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