Re: Light-Sport Aircraft Yahoo group Re: Can cruising the Rotax 912 a bit below 5000 RPM actually INCREA

My trike is set up so I can achieve about 5700 RPMs for takeoff and climb, but in cruising flight at trim speed I am only turning about 4100 RPMs.  If I want to go faster or climb, I can easily do either obviously, but I can't imagine I am damaging the engine by running at a pretty low power setting.  Has anyone talked to Lockwood about this.  I know they say the engine will run all day at 5500, and they also say don't exceed that except for short periods where it's necessary.  I've never heard them mention the low end being damaging, and I think if it was, they would have mentioned it.

Jim

 

From: pwrsport@ix.netcom.com

Sent: Thursday, December 22, 2011 12:15 PM

To: Sport_Aircraft@yahoogroups.com

Subject: Re: Light-Sport Aircraft Yahoo group Re: Can cruising the Rotax 912 a bit below 5000 RPM actually INCREA

 

 

Hi Alex; my short conversation on this was primarily directed toward the possible thinking that running a 912 at low rpm was saving the engine from ware or possibly increasing the engine longevity.  So I stated that the engine is designed and expected to run continually at substantially higher rpms day-in-day-out without harm. Running at low rpms may save fuel depending on the prop pitch and ground covered. You will use less fuel at low rpms, additionally you will be going slower.  Running at higher rpms should increase speed and ground covered.  The result is that the miles per gallon should be about the same for low or high rpms.  I should have spent more time on the lugging comment once said. It is possible to lug the engine at low rpm if the prop is set too course with a ground adjustable or fixed pitch where the desire was to get more speed or some other desire resulting in the engine not developing required rpms at high throttle settings. I would say that running at 4800 rpms is about as low as I would go for continuous operation if everything is set properly, as an example; not flying at a high angle of attack with high throttle setting.  Trying to cover these topics properly with brief writing is difficult as other factors also apply.

Ed Snyder 

 

 

 

-----Original Message-----
From: Alex
Sent: Dec 22, 2011 9:12 AM
To: Sport_Aircraft@yahoogroups.com
Subject: Light-Sport Aircraft Yahoo group Re: Can cruising the Rotax 912 a bit below 5000 RPM actually INCREA

 

Ed,

As Michael said :

                  Yes Ed, nobody is recommending "lugging the engine".

 

As the guy who posted the original question I had already mentioned that when speaking of running below 5000 RPM and wondering about the claim that this could cause more wear I was NOT lugging the engine.

 

In my Skyranger with me (weighing only 140 pounds) soloing at 4800 in level flight we are not in any sense lugging.

Low RPM does not necessarily mean the engine is lugging ---- no more so that when you cut RPM on approach.

 

So I still have the question --

Is it REALLY true -- counterintuitive though it may be -- that I am putting more wear on the 912 engine cruising my lightly loaded plane at 4800 RPM rather than 5500?

And if so, is the wear significant enough to worry about ....... As I do save a great deal of fuel and increase my range significantly by cruising slow.

 

Alex

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