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Touring Motor Gliders Association (TMGA)

Speed polar Grob109 with Rotax engine ?


gardener96

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Dear all,

I am an engineering student currently doing a project on the reengining of the Grob109B. I have already performed the gliding performance of the Grob109B with its original Grob 2500 E1 using the speed polar that was provided by my advisor.

However, i am now looking for data for the Grob109B, but with a Rotax engine. I was led to believe that such data could be found (notably the speed polar). It appears from what I could find that the Grob109A had a couple aircrafts approved for use with Rotax 912 engines, and that the Grob109B was developed from the Grob109A.

I have not found a speed polar, even for the Grob109A, with the rotax engine. Do you think such data could possibly be found?

I apologise in advance for the potential inaccuracies in my message. I admittingly do not have a lot of practical knowledge about aircrafts in general, and the project I am currently working on really highlights my shortcomings. Thank you in advance!

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Actually, the 'speed polar' which is usually the engine off sink rate vs forward velocity would not change much based upon the engine configuration.  So you don't need to find your specification configuration.  I'm attaching a flight test report on the engine-off performance of the Grob 109.

DickJohnsong109b.pdf

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