1) In the US, would it ever be legal to fly a loop in any US-registered airplane or glider that was operating in the "utility" category rather than the "acrobatic" category? (Assuming that no special waiver has been issued by the FAA: the question is not about Bob Hoover's famous Aero Commander routine etc.) Among other things, please consider the possibility that a loop may be listed as an approved maneuver in the "utility" category in the aircraft manual, which may or may not have originated in the US.
2) And here's a closely related, but more specific question, that I'd also like answered: Is it accurate to say that inside loops are generally permitted while flying in the "utility" category in the DG-1000S sailplane in Germany, but not while flying a US-registered DG-1000S in the US in the utility category?"
This FAR seems highly relevant:
§91.9 Civil aircraft flight manual, marking, and placard requirements.
(a) Except as provided in paragraph (d) of this section, no person may operate a civil aircraft without complying with the operating limitations specified in the approved Airplane or Rotorcraft Flight Manual, markings, and placards, or as otherwise prescribed by the certificating authority of the country of registry.
Some context-- note the extensive discussion of "semi-aerobatic" gliders here. I don't know whether said gliders are certified in the "acrobatic" category or not; certainly there are some aerobatic maneuvers that they are not cleared to do.
This link to a US glider club website suggests the answer to the first question is "yes" -- unless someone is just suggesting it's ok to be lax with the regulations-- the statement is made that it is "approved" to loop some gliders -- specifically including the DG-1000S-- when flown at a weight that puts them in the "utility" category, while at a lighter weight the same gliders would be in the "aerobatic" category and would be approved for more maneuvers.
Approved Maneuvers in Utility Category
DG-1000: ● G.W. below 1650 lbs ● No water ballast ● Tail ballast used to compensate for rear pilot OK
Approved Maneuvers: ● Spins ● Inside Loop ● Chandelle ● Lazy Eight (Wingover) ● Stall Turn (Hammerhead)
More advanced requires Aerobatic category
More information: the English version of the factory-produced flight manual for the German-made DG-1000S glider (may be downloaded here) states the following--
2.6 Approved manoeuvres Category „Utility“: The glider is certified for normal gliding in the "Utility" category. Simple aerobatics are approved but only without waterballast and with the weight of the rear pilot compensated by ballast in the ballast box in the fin see section 6.8.7.
The following aerobatic manoeuvres are approved with all spans:
Recommended entry speeds see section 18.104.22.168.
The manual then goes on to describe additional maneuvers allowed when flown at a lower weight limit, in the "aerobatic" category:
In addition to the manoeuvres in category „Utility“ the following manoeuvres are approved:
half flick roll from normal to inverted flight with half loop
half loop and half roll
half flick roll from inverted to normal flight
half roll and half loop
This link to an Australian aerobatics association website suggests that in that country, for any given aircraft, the pilot's handbook or cockpit placards will list all the maneuvers allowed in the Utility category, while in the Aerobatic category all standard aerobatic maneuvers are assumed to be permitted unless specifically listed as not allowed in the pilot's handbook or cockpit placards:
But this link to a related A.S.E. answer suggests the answer to the first question in the US is "no"--
So, please help me sort this out--
If your answer contains any answers to these additional closely related questions, it would be appreciated:
3) What, if any, FARs other than 91.9 are involved in the answer to question (1)?
4) In the US, is the situation in regard to question (1) fundamentally different for gliders than for airplanes for any reason?
5) What if a US-registered aircraft, and its flight manual, predates the establishment of the "utility" and "aerobatic" categories? Is it then up to the pilot's discretion whether to loop it or not in the US?