Rotax 912iS versus the 914 Turbo - Which One?

[912iS Fanatic]

Tom, you’re right about mixture control; need to take my own advice on off topic hearsay and my caveat about being beyond my experience base.  This is the best written section of the FAA’s LSA rules that I should’ve re-read.

https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/airplane_handbook/media/18_afh_ch16.pdf

[SlingPilot]

The iS still suffers from needing premature gearbox servicing. ROTAX has been on the case for a fix, but hasn’t quite solved the problem. I so wanted the iS for my Sling, but was talked out of it. I could have had the 914, but couldn’t justify the cost or need. I fly mainly on the east coast and east of the Mississippi. My flight back to NY from CA was easy with the ULS at FL095 and 11k. 

I’m sure ROTAX will address the teething pains, they are a fantastic company with a great product and respond to any and all issues. 

[Roger Lee]

The 912iS gearbox fix is just now hitting the market.

[912iS Fanatic]

The gearbox upgrade  was installed in mine over 18 months ago, it was paid for by Rotax  and we saw no evidence of wear but did the upgrade anyway.

[912iS Fanatic]

Roger you commented on this pretty extensively on the rotaxowner forum.  You also seem to be up on the prop and spinner balancing criticality for all versions, perhaps this is best for you to address.  My ownership of the iS has been a positive experience.

[Roger Lee]

The 912iS fix before now was just to install the same parts and hope they didn't wear again. Some had to replace gearbox parts 4-5 times. Rotax identified the issue as poor oil distribution in the gearbox, but especially on top and forward. The fix is now a new gearbox with a new oil spray nozzle mounted in the front to spray oil on top. You can see this in the new Parts manual. The gearboxes are just now coming out. Part of what took so long was the extensive testing that took thousands of hours to make sure it would work.

Props were not the cause of the 912iS gearbox dog hub wear. It is usually a good idea to get your prop balanced for the longevity and health of the engine over its lifetime. 

[Ed Cesnalis]

On 9/16/2018 at 11:46 AM, 912iS Fanatic said:

In terms of power, our 912iSc sport engined P2008 climbs out of Mammoth Lakes on a 90 degree day, with full tanks, two on board, one bag, at 1000fpm at 80KIAS.

I'm available anytime if you want to take me for a ride and demonstrate this.

I fly my CTSW out of Mammoth 3 days / week and find your claim to be dubious.  

[Warmi]

I thought 912is , according to Rotax numbers, had a bit more torque but I would be hard pressed flying my 912 ULS Sting at gross weight on a 90 degree day at 1000 fpm at 2800 feet density altitude , let alone at 7000 feet DA. 

Sounds a bit doubius indeed.

[Ed Cesnalis]

5 minutes ago, Warmi said:

let alone at 7000 feet DA

On a 90* day Mammoth DA is prolly 9,500'

[Eddie]

On 1/1/2018 at 8:08 PM, markmn said:

Hi, Mark Gregor from Advanced Aircraft/Tecnam US here.

I hope you don't mind me responding but the post is referencing a Tecnam after all!

We end up discussing pros and cons of the Rotax engines regularly. All three Rotax engines are offered by Tecnam because we believe they are all good viable choices. It just depends on what you want. The 912ULS is a well proven engine at a low price. The 912is is the latest in technology, full fadec w automatic lean of peak operation below 97% power. Impressive but no more horsepower than the ULS and likely less in many conditions. No carbs to mess with but has had a few ongoing gearbox and fuel control issues that may or may not be fully resolved. Definitely much better than when it was first released though. 

The 914 is a mature design but the turbo can be additional maintenance if a few basic care rules are not followed. The last 914s we delivered had carb leaks at high manifold pressure settings. Was easily resolved by a good Tech but goes to show nothing is ever perfect. With that said and nearly 1500 hours divided between all three Rotax engines the 914 is nearly always my first choice to pull out of the hangar. I like the 914 because it is smoother, quieter and substantially more powerful! The first time I flew the P2008 with the 914 i was very surprised how much stronger it was. Really sets you back in the seat compared to the 912. Takeoff roll is substantially reduced. The 914 cruises at 35 inches manifold continuous. At this setting the 914 is making a lot more horsepower that a 912. 40 inches manifold or 115% power as Rotax calls it is limited to 5 minutes. When I hear negativity about the 914 it is nearly always from someone who has never flown behind one.

Disadvantages?  A $20,000 more than the ULS and $8,000 more than the 912is!

Mark Gregor

Gregorma@bevcomm.net

507-3279465

Mark - can you offer an update regarding service issues with the 912is that have been discussed?   Were previous issues due to the install package?   Thinking about buying a P2008 sometime in the not too distant future, and I'm hung up on the engine choice issue, hearing a lot of pros and cons on the carb vs. injected versions.  Thanks!