FAA- Special airworthiness information bulletin on Rotax Engines

The following is a SAIB for Rotax Engines just published by the FAA and it was caused by a European AD note. I assume that the FAA decided that most of the Rotax engines are not on Certificated Aircraft so an AD note would do very little as all Experimental Aircraft are not covered by AD's as required action (yes it would be dumb to fail to comply with most of them).

It will be interesting to see how this effects the RV-12.

Best regards,
Vern


FAA
Aircraft Certification Service
SPECIAL AIRWORTHINESS
INFORMATION BULLETIN
SUBJ: Reciprocating Engine Liquid Cooling: Bombardier-Rotax 912 & SAIB: NE-05-84R1
914 Series Engines Date: September 10, 2009
This is information only. Recommendations aren?t mandatory.

Introduction

This Revised Special Airworthiness Information Bulletin (SAIB) alerts you, owners and operators of Bombardier-Rotax (Rotax) 912 A, 912 F, 912 S, and 914 F series reciprocating engines and facilities that maintain and repair these engines, to revised information related to monitoring of cooling system temperatures and the type of liquid coolant to use in these engines. All other
information remains the same. These engines are installed on, but not limited to, Aeromot-Industria Mecanicao Metalurgica AMT-200, AMT-200S, and AMT-300; Aquila Technische Entwicklungen GmbH AT01; Diamond Aircraft Industries (Austria and Canada) DA20-A1, HK36 R, HK36 TC, HK36 TS, HK36 TTC, HK36 TTC-ECO, and HK36 TTS; Iniziative Industriali Italiane 650 TC, 650
TCN, 650 TCS, and 650 TCNS; and Stemme GmbH S10-VT aircraft. These engines may also be installed on amateur-built and light-sport aircraft. At this time, this airworthiness concern is not an unsafe condition that would warrant airworthiness directive (AD) action under Title 14 of the Code
of Federal Regulations (14 CFR) part 39.

Background

The European Aviation Safety Agency (EASA) has advised us of possible loss of coolant and engine overheating on Rotax 912 and 914 series engines. Based on these findings, EASA published AD 2007-0155, dated May 29, 2007, that requires use of a waterless type coolant if the engine coolant exit temperature will exceed 120? centigrade (C). Use of waterless coolant may not apply to all Rotax 912 and 914 series engines because coolant exit temperatures are affected by the aircraft installation and operating conditions. The maximum cylinder head temperature limits approved for
these engines remain the same.

If you use a conventional ethylene-glycol/water coolant, and engine coolant exit temperatures exceed 120? C, loss of coolant, engine overheating, knocking, and engine damage can occur, which could result in an in-flight shutdown. You should monitor the coolant exit temperature to prevent engine
overheating when using conventional coolant. You can also prevent engine overheating by monitoring cylinder head temperature if an appropriate correlation is established between coolant exit temperature and cylinder head temperature.

Rotax service bulletins SB-912-043 Revision 2, dated November 10, 2006, and SB-914-029 Revision 2, dated November 10, 2006, provide additional information about coolant usage. The applicable Rotax 912 and 914 installation manuals and operator?s manuals also provide related information.
Recommendations

We recommend that you comply with the coolant usage information provided in Rotax service bulletins SB-912-043 Revision 2, dated November 10, 2006, and in SB-914-029 Revision 2, dated November 10, 2006, and the applicable Rotax 912 and 914 installation manuals and operator?s manuals.

2 We also recommend that you comply with the coolant usage information and cooling system temperature limits defined by the manufacturer of your aircraft because of installation effects on engine cylinder head and coolant exit temperatures.

For Further Information Contact Richard Woldan, Aerospace Engineer, FAA, Engine Certification Office, 12 New England Executive Park, Burlington, MA 01803; telephone: 781-238-7136; fax: 781-238-7199; e-mail: [email protected].

For Related Service Information Contact BRP-Rotax GmbH & Co. KG, Welser Strasse 32, A-4623 Gunskirchen, Austria; telephone: (43) 7246-601-0; fax: (43) 7246-601-760; Internet: www.rotax-aircraft-engines.com

This looks like a rehash of Rotax SB 912-043, which gives details. It's a complicated issue, but Rotax is concerned with the cooling capacity of the engine. One of the concerns is getting localized boiling of a water-containing coolant. Rotax wants you to look at the actual coolant temperature - which is different from the CHT reading - and if the coolant is above 250F, switch to waterless coolant. If your CHT and coolant temps don't exceed 250F, you don't need to do anything.

Now, I think very few of us are going to install coolant temp sensors (in fact, since most of you are building E-LSA, you can't!), so I would ask Van's if they have done any monitoring of the coolant temperature.

Personally, I never see CHTs above 230, so I am not interested in switching to waterless coolant. Yes, it allows for higher CHTs, but the coolant has a lower heat capacity and, well, isn't compatible with water. I suggest waterless coolant only if you have an issue with CHTs and/or coolant temps. I don't know how well the RV-12 cools, so I can't say whether any of you will need to do it. YMMV.

TODR

Why not just use waterless coolant?

So as I read this, the obvious question that comes to mind is why not just use waterless coolant and eliminate the risk rather than trying to determine whether there is a problem with water-containing coolant in a given installation? I presume there must be some downside to the waterless coolant that I am not aware of but I don't see that commented upon anywhere.

Typically, in the planes I have flown with a 912S, it was hard to get temps to 180F let alone 250F. Installing a coolant temp is not a big deal and can be done pretty cheap, and we can add the sensor info right to the Dynon, I think. I can't imagine why adding another sensor after this "AD" would be a bad thing even for the -12 and the LSA thing. Actually, I'm surprised it does not have it installed already.

jte65 said:

So as I read this, the obvious question that comes to mind is why not just use waterless coolant and eliminate the risk rather than trying to determine whether there is a problem with water-containing coolant in a given installation? I presume there must be some downside to the waterless coolant that I am not aware of but I don't see that commented upon anywhere.

Click to expand...

Good question. As I see them, here are the pros and cons of Evans NPG waterless coolant:

* Cost is higher than Dexcool (or other traditional coolants)
* Incompatible with water; thus, you need to carry some with the plane or risk being low on coolant when "on the road". You cannot not just top off with distilled water or traditional coolant.
* Lower heat capacity - it will not cool as well as traditional coolant or coolant/water mixes. This is somewhat ironic since you'd be switching to the waterless to prevent overheating!
* Won't boil, so there are no localized hot spots where the coolant forms micro-bubbles. No chance of boilover ever.

TODR

One downside, Evans "burns like Sterno".

Coolant Temperature Sensor Required?

I have just reread this stuff. The Rotax SB requires the 1.2 bar coolant pressure cap to be fitted by operators. My engine has the 1.2 bar cap.

It also requires manufacturers to comply with the provisions of the table listing coolant temperature, CHT, and coolant types.

The way I read it, even if coolant and cylinder head temperatures remain below threshold temperatures it is still a requirement to install instrumentation to monitor coolant temperature - if you are using water/glycol.

Am I wrong?

Cheers...Keith

there is one advantage to the waterless coolant. if your engine does get hot and boils the waterbase coolant then you can get bubbles or air in the system or water pump. this will cause the pump to cavitate. this is a bad thing for an airplane in flight. your choice. my 2 cents.

One guy I know tried the Evans when the original SB came out. He could not keep his 912 (80HP) within acceptable heat ranges (it was a hot summer). He went back to 50/50 Dexcool/Distilled and his temps all dropped. Rotax later amended the SB to allow Dexcool/water.

gpiney said:

One guy I know tried the Evans when the original SB came out. He could not keep his 912 (80HP) within acceptable heat ranges (it was a hot summer). He went back to 50/50 Dexcool/Distilled and his temps all dropped. Rotax later amended the SB to allow Dexcool/water.

Click to expand...

I ran Evans coolant in the 912 in my RANS S-7. My CHT and oil temps were typically in the 220 to 230 range. In my RV-12, I'm seeing both sets of temps under 200, even in the summer, using the 50/50 water/glycol mix. Both engines ran fine, with no overheating issues- I'm not going to worry about it. Steve