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I am due for a 50 hr Rotax Scheduled Maintenance Check (oil change when operating with 100LL) in 2 hrs, but my annual is just a month away —trying to avoid two maintenance visits in such a short time. After reading the Rotax manual, the way I understand it Rotax allows for a 10 hr tolerance on their inspections.

This is the same tolerance as ICON use for the airframe 100-hour inspection (not that common unless you fly a lot), although ICON say "while en route to reach a place where the inspection can be done." This mimics the language in FAA's 91.409(b), even though ICON's is under 91.327 (Aircraft having a special airworthiness certificate in the light-sport category: Operating limitations.)

Rotax Scheduled Maintenance Tolerance

- For the intervals between maintenance work, a tolerance of ±10 hr. is permissible, but these tolerances must not be exceeded. This means that if a 100 hr. check is actually carried out at 110 hr., the next check will be due at 200 hr. ±10 hr. and not at 210 hr. ±10 hr.

- If maintenance is performed before the prescribed interval, the next maintenance check is to be done at the same interval (e.g. if first 100 hr. check is done after 87 hours of operation, the next 100 hr. check must be carried out after 187 hours of operation).

ICON Scheduled Maintenance Tolerance

- The 100-hour limitation may be exceeded by not more than 10 hours while en route to reach a place where the inspection can be done. The excess time used to reach a place where the inspection can be done must be included in computing the next 100 hours of time in service.

- For the Condition Inspection "annual there is really no tolerance other than to the last day of the month of the previous annual - "performed once every 12 calendar months by a certificated repairman (light-sport aircraft)."