Operating Temps (It COLD!!!)

[tevbax]

Tried a search and looked through the POH. I could not find a min/ max operating temp for the CTSW. Besides freezing my backside off when cold, is there a minimum temp for operation? Looking to do a flight tomorrow and expected temps are -3F, which is a bit brisk. Radiator is taped up, new seals on the cabin. 

Other than the obvious freezing to death if there was an emergency, does the aircraft have any temp restrictions? 

 

[Anticept]

I have flown in -40c. It was cold enough that I had to turn on carb heat to stop the engine stumbling (that's so cold that gas has trouble atomizing).

You'll be fine.

[tevbax]

Thanks for the quick reply! If I remember correctly, the last club that I was in stopped flying when it was zero. I think that had more to do with creature comfort and emergency ops. 
 

[Mike Koerner]

Mike, Corey,

I think there are a couple limitations you should keep in mind.

First, the minimum oil temperature is 120F (CT2k & CTSW Pilot Operating Handbook, rev 2, revised 05.10.2005, Section 3.1 page 10). Obviously, when you start the plane, the oil is colder than this, but they tell us to keep the RPM below 2200 until the oil gets to this temperature. Apparently, they don't want the engine operated at higher power settings if the oil is cold. This is significant when flying around in really cold conditions. If you power back to descend, the oil temp is going to drop below the 120F threshold. That means you need to maintain power during descends, and perhaps even in the pattern, so you can go around if you need to without violating the oil temperature limitation.

Second, there's a -13F minimum temperature limitation for "engine starting and operation" (page 11 of the same section of the same document). Reading a discussion of cold temperature operation by Mike Busch leads to an appreciation of this limitation, even though he's discussing engine starting.

    

[Anticept]

The engine stayed warm enough, no issues there, even on the descent. But yes it's something to be conscious of, especially if you have one without a coolant thermostat and you have a LONG descent ahead of you.

[Roger Lee]

First move to a warmer climate. LOL

"but they tell us to keep the RPM below 2200 until the oil gets to this temperature. Apparently, they don't want the engine operated at higher power settings if the oil is cold."

I know we were all told originally that 2K plus warm up rpm was good, but Rotax doesn't care about higher rpms up to 2700 for a warm-up and they actually prefer 2500+ or so because there is less hammering on the gearbox and parts from an 11:1 compression ratio , a 30 degree dog gear set in the gearbox and other parts being subject to too much vibration that you can't feel. Point in case. You won't feel what the engine feels with the internal vibration unless it's really bad. I just had a Sting aircraft at my field that always warmed up at 2K -2.2K. They have 914 hours on the engine and just paid $2800 getting dog gears and other parts replaced due to vibration damage from low rpm warm up. I have now seen this about 4-5 times.

Leading Edge and the other service centers recommend higher rpm warm ups especially when it's cold. 

You WILL NOT hurt anything with a higher warm up rpm, but you may save yourself an expensive fix later.

 

If the oil temp drops to a low temp during the short approach for landing it is temporary and not a big deal. You just don't want to sit and operate in extra low temps for extended cruise times.

[procharger]

I believe with my new e-prop being so light should help with

gearbox issues?? maybe

[Roger Lee]

It's not just about prop weight. It's about internal vibration in part caused by compression ratio combined with the 30 degree dog gear hub. The 912iS doesn't have that issue.

[Jim Meade]

Field reports are often helpful.  It's nice to see supporting documentation.  Does anyone have a reference I can read that says Rotax permits or prefers higher warm-up RPM?

[Roger Lee]

It's published. Time to read and research.

[Jacques]

from the operators manual

[Jim Meade]

I talked with the lead tech at LEAF and he supports following the manual.  I do observe manual instructions, and I also watch oil pressure.  As oil pressure drops, I tend to slowly add throttle to warm up a little faster.  My FD CTSW oil pressure stays high for quite a while.  My Rans S-7S with same engine shows lower oil pressure right away and settle in the high 50's pretty quickly, so maybe there is something to do with the engine installation and sensors, as well.

Anyway, I generally follow the manual but combine oil temperature, water temperature and oil pressure in choosing warm-up throttle settings.

[Roger Lee]

Way to go Jacques.

Leaf a.k.a. Leading Edge Airfoils is not only the one that repaired that vibration damaged gearbox, but were the ones that told the client to idle at 2500+ during warm up so as not to damage it again. Cold engine's suffer worse than one from summer time temps.

[Jacques]

2500 rpm warm up is there since  a long time....in the Operator Manual

..although...in this Service Letter

https://legacy.rotaxowner.com/si_tb_info/serviceletter/sl-912-016-r1.pdf

in 3.2.4)  Keep engine at around 2200 rpm for warm up period

Rotax should revise this SL

[Roger Lee]

Rotax is not always joly on the spot for some revisions. The 2500 is better on cool and cold days and the 2200 would be better suited for summer months when the whole engine isn't as cold. That said I always use 2300 in the summer and 2500 in the winter and our days here are near as cold as the north and northeast states. If you live in cold country you really should be using a engine pre-heat. It's a whole lot easier on the engine for starts and the first several minutes of the warm up.

[Jacques]

4 minutes ago, Roger Lee said:

If you live in cold country you really should be using a engine pre-heat. It's a whole lot easier on the engine for starts and the first several minutes of the warm up.

you bet.... I start preheating at 40°F (5°C)....   kickbacks are no good and sprag clutch is PITA to change..and.$$$$

[Bill3558]

I recently posted about cold starts with my 912is lane lights staying on after engine start. I read on Rotax owners site what I was doing wrong. I now let the EMS boot completely, and turn the ignition on for a few seconds before engaging the starter. Problem solved. 
Don’t rush it. 

[EricB]

Anyone for a Tannis engine heater?