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.