Rotax 916

[John Spartan]

If you have a constant speed prop a lycoming will develop full rated power for takeoff.

Still not reading you. Rotax has constant speed too. Both can produce full power at takeoff. What did I miss?

Rotax with turbo gets some great advantage at altitude because turbo. With the new props for Rotax coming there are going to be some awesome planes in the next 3 years. Look at Sling HW and Montaer MC04 for example.

 

[Shepherd]

Am I missing something? Can Rotax be run at full horsepower continuously, despite what the manufacturer says? I read that the 916 is capable of 160 hp during takeoff, but only has 137 continuous hp, which is hardly better than the 135 continuous hp of the 915. Can the 915 run at 141 hp full time, and will the 916 be able to run at 160 hp all the time?

I was told, and I'm under the impression, that the time limits for maximum power were an FAA rule, not a Rotax rule.
If you run the Rotax at continuous max power the plane will fly faster than the allowable 120 knots. The same applies to the Jabiru 3300 Arion LS-1.
I don't know what a Rotax 916 is capable of, but I've flown an Arion LS-1 at full power and over 140 knots (calibrated) for 25 minutes.

 

[John Spartan]

I was told, and I'm under the impression, that the time limits for maximum power were an FAA rule, not a Rotax rule.
If you run the Rotax at continuous max power the plane will fly faster than the allowable 120 knots. The same applies to the Jabiru 3300 Arion LS-1.
I don't know what a Rotax 916 is capable of, but I've flown an Arion LS-1 at full power and over 140 knots (calibrated) for 25 minutes.

I thought it was a matter of boost levels and a ton of manifold pressure. 160 hp at full power for 5 mins then 135 hp continuous up to like 15000 feet. That 160 at takeoff though would overcome a lot of density altitude issues and be very useful. The 135 in cruise would be plenty to rip along at 150+ knots in a Sling.

 

[Tusayan]

One would have to assume that there will be more choices emerging. If not the prop makers are stupid.

They’re not stupid now or in the past either. Wood bladed CS props as done by MT have infinite blade fatigue life and the damping that comes with low blade stiffness. This is not ideal for propeller design in general but makes them applicable to geared (four cylinder) engines with tough vibration and blade fatigue issues. Other prop blade technologies which I think are better in every other way do not have these attributes, so we find Rotax with limited certified CS prop options.

 

[John Spartan]

They’re not stupid now or in the past either. Wood bladed CS props as done by MT have infinite blade fatigue life and the damping that comes with low blade stiffness. This is not ideal for propeller design in general but makes them applicable to geared (four cylinder) engines with tough vibration and blade fatigue issues. Other prop blade technologies which I think are better in every other way do not have these attributes, so we find Rotax with limited certified CS prop options.

Interesting. Well, the reward is finally great enough for the prop makers to overcome these issues. I suspect plenty has been learned from the European market too. I’m going to stick to my positive outlook on CS prop improvements being likely for Rotax.