Rotax engines (1) scheduled service intervals

Rotax serviceOn what basis do you record your times for scheduled services on your Rotax engine? Engine running hours – start to stop? Starting to taxi to stopping – wheels turning to wheels stopping? Flight time via an air switch – wheels off to wheels on the runway?

At bigger and/or busier airfields there could easily be a big cumulative difference between engine start/stop and wheels off to wheels on the runway – as much a 25% or more by some LAME accounts. So what is the correct procedure for recording times to determine scheduled maintenance on your Rotax engine? The answer, it seems, has been about as clear as year-old engine oil!

The initial response from the Rotax service department to my query was that maintenance must be carried out based on engine running time as recorded by ‘an electronic engine hours timer’ – ie start-up to shut-down. This is different to some of the statements in their maintenance manuals and certainly not the way most flight schools and clubs record time for engine servicing; they usually use take-off to landing times for overhaul.

Please note:
What follows has now been superseded by the following: all Rotax engine scheduled maintenance times are currently based on engine running times – ie from start up to shut down. Therefore, for maintenance purposes, record engine running times accordingly. Also check to ensure that the airframe manufacturer aligns their mandatory maintenance schedules with the engine maintenance requirements. Most of them do – including Aeroprakt.

Please also see my updated blog post on scheduled maintenance times:

When questioned a little more, Rotax finally clarified that their engine scheduled maintenance times comply with standard FAA (and CASA) practice – that is, take-off to landing time, ideally measured with an air-switch hours meter. I now have this in writing (by email) from them, so if you or your engineer need written confirmation, let me know.

So, repeating, for the sake of avoiding all doubt – record your engine scheduled maintenance times from take-off to landing. Maybe even fit an air-switch-operated hours counter if you need to. In the long run, this can save you quite a lot when it comes to servicing, likely well more than the cost of fitting an air-switch.

PS – Don’t forget: if you are late with a service – eg 55 hours instead of 50, the next service is still due at 100 hours, not 105. Read the Rotax manuals!

3 thoughts on “Rotax engines (1) scheduled service intervals

  1. Pingback: Rotax Engines (4) scheduled maintenance update | Foxbat Pilot

  2. Hello FP,
    the service interval for a 912 has puzzled me for ages, and I have just asked the question of the UK Distributor who says completely the opposite of the above i.e engine-on time regardless of load. So please could you let me have a copy of this confirmation? cheers

    • Hi Ron
      Here are the references regarding engine & flight times:
      (A) Rotax 912ULS Line Maintenance Manual, 05-10-00, Page 3.1) Definition of Terms.
      Notes: A mechanical Hour Meter is directly coupled to the engine speed, the readings may deviate considerably from those given by electronic remitters (e.g. TCU, Flydat). Maintenance and Overhaul intervals are always dictated by the Readings of the electronic Hour Meter.

      There on the same page is,
      1.2) Time Limit, and 1.3) Life Cycle.
      The life cycle is always specified as an exact time span and is also quoted in Flight Hours
      Note: Parts with a limited life cycle must be taken out of operation and overhauled if the specified time span or number of Flight Hours is reached.
      (B) Rotax 912 ULS Heavy Maintenance Manual, 72-00-00, Page 8.
      Note: As the Mechanical hour meter is directly coupled to the engine speed, the readings may deviate considerably from those given by electronic hour meters (e.g.TCU, Flydat),
      Maintenance and Overhaul intervals are always dictated by the Flight Time.

      These items clearly refer to ‘Flight Times’ not engine running/operating times.

      Further, on 05 March 2015 I received the following reply from Rotax regarding my queries about engine vs flight times:

      “Hello Peter,
      You can safely ignore the implied references to “engine running time”. The documentation could stand some rewording – ROTAX actually conforms to the FAA definition.
      FAA definition: Time in service with respect to maintenance records is flight time (wheels off the ground until they contact again).
      Best regards, Michael”

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