Primarily for general aviation discussion, but other aviation topics are also welcome.
#1829784
TheFarmer wrote:If I’m going to have to get UL91 to fly in future, that’s a big hit on the appeal of my kind of flying.

I can feel the end of 34 years of great times coming.


I'm surprised you don't get it delivered. Once you've got somewhere to store it even at 1,000 litres at a time it works out affordable.
#1843045
MikeW wrote:
russp wrote:
MikeW wrote:
Unfortunately they don't do super, only normal 95, fine for a 912, not very good for a 912S.


I think you'll find that UK standard unleaded is manufactured to the same EN228 super standard that Rotax specify as the Min Mogas standard for the 912S. UK super unleaded is EN228 super plus .. and Yes it is stupidly confusing!


Well having spent a bit of time Googling EN228 in various incarnations my brain hurts! It seems you are right though. As far as I can make out Rotax are still using pre 2009 terms when basic 91 octane became "regular", super 95 became standard unleaded (or premium) and super plus became super - is that it?
For stupidity it's on a par with Annexe 2 becoming Annex 1.
Good to know - thank you.



Just when you thought it was safe etc..

Rotax service letter 912-016 R2 now recommends using 98RON for the 912ULS!
#1843206
MikeW wrote:
MikeW wrote:
russp wrote:
I think you'll find that UK standard unleaded is manufactured to the same EN228 super standard that Rotax specify as the Min Mogas standard for the 912S. UK super unleaded is EN228 super plus .. and Yes it is stupidly confusing!


Well having spent a bit of time Googling EN228 in various incarnations my brain hurts! It seems you are right though. As far as I can make out Rotax are still using pre 2009 terms when basic 91 octane became "regular", super 95 became standard unleaded (or premium) and super plus became super - is that it?
For stupidity it's on a par with Annexe 2 becoming Annex 1.
Good to know - thank you.



Just when you thought it was safe etc..

Rotax service letter 912-016 R2 now recommends using 98RON for the 912ULS!


Are you sure??

The latest version I can find is SI 912-016 R8 which still specifies Min RON 95 for the 912S/ULS, although it calls it EN228 Super.

So this posted on Rotax-Owner.com a month ago applies:

"In EN228 terms regular used to be 91 octane, super was 95 and super plus was 98. This changed a few years ago so 95 officially became just unleaded (but commonly called premium in UK) and 98 became super. There is no super plus now. This change seems to have escaped Rotax.

So unleaded (or premium) 95 should be OK for a ULS. However some brands of super have the advantage of 0% alcohol whereas 95 has to contain alcohol unless it is from a low volume supplier (this concession is UK only I think.) The pump still has to be labelled E5, this means up to 5%, including 0%.

I only became aware of this confusing situation recently from someone with more specialist knowledge than me, I previously thought you had to use super (i.e. 98)."

PS In Scotland in my experience, both types of unleaded have contained 5% alcohol for some years. However, if standard unleaded goes to 10% alcohol, but Super remains at 5% alcohol for a while, it might be necessary to use it again until the LAA approves E10 in your particular aircraft or longer if your tank etc is not suitable for 10% alcohol. Otherwise, the only alternative will be Avgas, preferably UL91.
#1843254
It's SL912-016R2, not SI912-016. You can get it from the flyrotax site documentation section.

It says
"In general, the minimum RON 98 fuels significantly reduce the proneness to detonation
damage and increases engine longevity. The selection of proper fuels is one of the
main levers to prevent detonation damage, especially in the case of other contributing
factors being present (see the table in section 3.1). ROTAX®, therefore, recommends
a minimum of RON 98 fuels in case of uncertainties or doubts."

In fairness, it doesn't prohibit using RON95 but says you must be careful about operating conditions and detonation.

The RPM/MAP graph from the previous version of the SL is redrawn with separate curves for RON95 and RON98. With RON98 you can use WOT down to 4000rpm, with RON95 use of WOT is only allowed above 5200rpm.
#1843318
MikeW wrote:It's SL912-016R2, not SI912-016. You can get it from the flyrotax site documentation section.

It says
"In general, the minimum RON 98 fuels significantly reduce the proneness to detonation
damage and increases engine longevity. The selection of proper fuels is one of the
main levers to prevent detonation damage, especially in the case of other contributing
factors being present (see the table in section 3.1). ROTAX®, therefore, recommends
a minimum of RON 98 fuels in case of uncertainties or doubts."

In fairness, it doesn't prohibit using RON95 but says you must be careful about operating conditions and detonation.

The RPM/MAP graph from the previous version of the SL is redrawn with separate curves for RON95 and RON98. With RON98 you can use WOT down to 4000rpm, with RON95 use of WOT is only allowed above 5200rpm.


OK, thanks. I wonder why Rotax have not updated SI 912 016?

PS I presume this is mainly an issue with constant speed or variable pitch props?