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Fuel Restrictor RV-12 Notice

jeterjim

Member
I just received this form Rotax. Does this refer to the requirement to remove the Banjo bolt pilot jet? RV-12 Pg. 46-09.


The purpose of this Information Safety Notice is to inform ROTAX operators and owners about the mandatory fuel return line that is required to be incorporated into the aircraft's fuel system design.

As per the ROTAX installation manual, a Mandatory ?restricted? fuel return line is to be incorporated within the aircraft's fuel system. The purpose of the fuel return line is to bleed off any vapors that may form within the fuel system that could cause vapor lock, resulting in a possible loss of engine power.

Please reference the latest ROTAX installation manual and check with the manufacturer of the aircraft to verify that a fuel return line has been incorporated within the design of the aircraft's fuel system.


The latest Rotax Installation Manual can be found at www.FlyRotax.com OR www.RotaxOwner.com

What is this Information Safety Notice about and how does it affect me?

Field reports have indicated a potential for fuel system vapor lock leading to loss of engine power or stoppage due to one or more of the following variables:

-Fuel system design
-Engine cowling design
-Fuel quality
-Seasonal adjustment on fuel
-High ambient temperatures

Owners and operators need to consider all of the above and understand how they may contribute to fuel system vapour formation.

Fuel System Design

Fuel system design is one factor in managing the formation of vapour in the fuel system due to heat soak. Fuel system components in close proximity to engine heat sources should be adequately protected from heat soak. Fuel line routing, heat shielding, fire sleeve etc. all influence fuel system temperatures.

Engine Cowling Design

Engine cowling design is another factor which can greatly influence heat soak on engine fuel system components. Tightly cowled engines can run much hotter under-cowl temps than more open cowl designs during certain conditions such as taxiing and climb.

Owners and operators need to understand their aircraft's temperature limitations and respect them. Rotax defines maximum engine component operational temperatures in the respective engine installation manual.

Fuel Quality

Fuel quality can have a large influence on the formation of vapour. Inadequate storage, handling and contamination can all affect fuel quality. Always respect the minimum fuel requirements as outlined by Rotax, maintain good storage practices and source the best quality fuel possible.

Seasonal Adjustments

Seasonal adjustment of fuel by manufacturers for high summer temperatures and low winter temperatures may affect the fuel vaporization rates. This can have consequences when using winter grade fuel in hot summer months. Always use seasonally correct fuel.

High Ambient Temperatures

High outside ambient temperatures may increase under-cowl operating temperatures and therefore increase the fuel system heat soak. Owners and operators may need to adjust performance expectations when operating in such conditions.

How Does This Affect Me?

In consideration of the above variables, Rotax has updated the engine installation manual to mandate the use of a fuel return line. Such a design helps to vent off the formation of fuel vapours, increasing the safety margin. Owners and operators are urged to consider all the aforementioned and review their fuel system design with their respective aircraft manufacturers.

NOTE: Although this video series is for the fuel injected engine, it is still relevant to the carbureted 912 series in regards to fuel vapor formation and cooling systems.
 
I just received this form Rotax. Does this refer to the requirement to remove the Banjo bolt pilot jet? RV-12 Pg. 46-09.

No

The just issued safety notice is to bring awareness to the requirement that a fuel return must be part of the fuel system for a 912ULS (when Van's first started on the RV-12 development program, there was no such requirement).

The RV-12 does have the fuel return incorporated into the fuel system design so as along as an RV-12 has been built per the KAI, this notification is complied with and can be ignored.
 
Jim--

yes the design of the RV12 fuel system does comply with the Rotax guidelines.
Our retrofit hose package does also, AND complies with Rotax SI-912-022, which (paraphrase) states that if teflon hoses are used, they do not fall under the 5 year replacement guidelines, other than obvious inspection.

In looking for this SB, I found an interesting one--SI-912-008r1, which (paraphrase) refers to fuel pressure indication problems. Check for the proper tolerances of the crush washers around the banjo bolts. It only affects the pressure INDICATION on the gauge, NOT the actual supply pressure.
(The TS Flightlines/Aircraft Specialty retrofit kit uses AN hardware and not banjo bolts and is not affected by this.)

For those of you that have experienced a low fuel pressure indication on your RV12's I wounder if it was AFTER some maintenance of the banjo connections and the crush washers were NOT replaced. The bulletin seems to indicate that the reduced thickness of a reused crush washer 'could' affect the fuel pressure indication.

The SI-912-008r1 is on the Rotax site.

Tom
 
yes the design of the RV12 fuel system does comply with the Rotax guidelines.
Our retrofit hose package does also, AND complies with Rotax SI-912-022, which (paraphrase) states that if teflon hoses are used, they do not fall under the 5 year replacement guidelines, other than obvious inspection.
................
Tom

Tom
I just went to your web site to look for the Rotax hose retrofit/replacement package and could not find it.
I will be replacing Rotax hoses in a couple of years and will hopefully remember your kit, but it would help if there was some easy and prominent link to it on your web site (and indicating that your kit does not have a calendar life if that is the case).
John
 
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Tom
I just went to your web site to look for the Rotax hose retrofit/replacement package and could not find it.
I will be replacing Rotax hoses in a couple of years and will hopefully remember your kit, but it would help if there was some easy and prominent link to it on your web site (and indicating that your kit does not have a calendar life if that is the case).
John

John,

Tom and I developed this kit together a few years back as a retrofit kit to improve on the standard package.

Here is a link to the kit

http://aircraftspecialty.com/rv-12.html

And here is a link to the install manual

http://aircraftspecialty.com/PDF Documents/Fuel Hose Install 111013.pdf

If you have any questions at all please feel free to contact us. We will also be monitoring this thread.

Have a great weekend and happy building
Steve
 
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I installed the Aircraft Specialty fuel hoses at last annual. I have 6 months with them now (65 Hours) and I am very pleased with them.
 
I installed the Aircraft Specialty fuel hoses at last annual. I have 6 months with them now (65 Hours) and I am very pleased with them.

I agree, the Aircraft Specialty fuel hoses for the RV-12 are a top notch product ... I too am very pleased with them.
 
John in Australia,
the picture is in the gallery. Sorry! I'm not real computer/website functional, as alot of you know. Steve is MUCH better at this than I am. LOL----thats why we work so well together, and share stuff!
We've been trying to update our website, but frankly a bunch of other things have taken priority. But we'll get it done.

Tom
 
yes the design of the RV12 fuel system does comply with the Rotax guidelines.
Our retrofit hose package does also, AND complies with Rotax SI-912-022, which (paraphrase) states that if teflon hoses are used, they do not fall under the 5 year replacement guidelines, other than obvious inspection.

In looking for this SB, I found an interesting one--SI-912-008r1, which (paraphrase) refers to fuel pressure indication problems. Check for the proper tolerances of the crush washers around the banjo bolts. It only affects the pressure INDICATION on the gauge, NOT the actual supply pressure.
(The TS Flightlines/Aircraft Specialty retrofit kit uses AN hardware and not banjo bolts and is not affected by this.)

For those of you that have experienced a low fuel pressure indication on your RV12's I wounder if it was AFTER some maintenance of the banjo connections and the crush washers were NOT replaced. The bulletin seems to indicate that the reduced thickness of a reused crush washer 'could' affect the fuel pressure indication.

The SI-912-008r1 is on the Rotax site.

Tom


Tom - so the return line (I assume supplied by your group for the kit) does have some "restriction" included in the design? If so, how does it compare to the flow rate of the restrictor that is removed from the factory?

Thanks,
Jim
 
Tom - so the return line (I assume supplied by your group for the kit) does have some "restriction" included in the design? If so, how does it compare to the flow rate of the restrictor that is removed from the factory?

Thanks,
Jim

Jim,

Yes. Our retrofit fuel system does have a restricted return line. There is a difference in the placement, but the orifice restriction size is matched very closely to the restrictor size utilized in the standard kit.

If you would like to see the installation manual it shows both the restrictor as well as how the system is installed in the RV-12.

Here is a link to the kit

http://aircraftspecialty.com/rv-12.html

And here is a link to the install manual

http://aircraftspecialty.com/PDF&#37...l 111013.pdf


Have a great weekend and let me know if you have any other questions.
Steve
 
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In looking for this SB, I found an interesting one--SI-912-008r1, which (paraphrase) refers to fuel pressure indication problems. Check for the proper tolerances of the crush washers around the banjo bolts. It only affects the pressure INDICATION on the gauge, NOT the actual supply pressure.
(The TS Flightlines/Aircraft Specialty retrofit kit uses AN hardware and not banjo bolts and is not affected by this.)

The standard Van's supplied installation is not effected by this either (the attachment of the fuel pressure sensor is done in a totally different way) so whether you have the standard installation or the Flightlines kit they will perform the same.
 
Coming full circle back to this....

There has been discussion in the past regarding differences in the orifice restrictor diameter for the return hos on the VA-216 kit supplied hose assembly, and the specification listed in the Rotax install manual.

The orifice used by Van's in the VA-216 hose assembly is a standard off the shelf part supplied by Rotax.
It has a restrictor orifice that measures .020-.021" diam.
The install manual specifies that it be .014" diam.

It took a while, but I have finally been able to confirm (all the way back to engineering in Austria) that the specification in the install manual is an error and will be revised.
The Rotax factory supplied part with the .020 orifice diam. is the desired size, and will produce the desired amount of return flow.

Knowing this I need to amend my previous post.....
The standard Van's supplied installation is not effected by this either (the attachment of the fuel pressure sensor is done in a totally different way) so whether you have the standard installation or the Flightlines kit they will perform the same.
I believe the Flightlines kit uses a .014 restrictor as specified in the install manual. That being the case the return flow will be lower so the performance in that aspect will not be the same.
 
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Coming full circle back to this....

There has been discussion in the past regarding differences in the orifice restrictor diameter for the return hos on the VA-216 kit supplied hose assembly, and the specification listed in the Rotax install manual.

The orifice used by Van's in the VA-216 hose assembly is a standard off the shelf part supplied by Rotax.
It has a restrictor orifice that measures .020-.021" diam.
The install manual specifies that it be .014" diam.

It took a while, but I have finally been able to confirm (all the way back to engineering in Austria) that the specification in the install manual is an error and will be revised.
The Rotax factory supplied part with the .020 orifice diam. is the desired size, and will produce the desired amount of return flow.

Knowing this I need to amend my previous post.....

I believe the Flightlines kit uses a .014 restrictor as specified in the install manual. That being the case the return flow will be lower so the performance in that aspect will not be the same.

First off... Thank you Scott for checking into this further. I am glad that Rotax is fixing the published documentation so that it is accurate.

The ASFlightlines kit currently has a .015 orifice restrictor, which is .001" larger than the one that has been listed in the official Rotax documentation (and continues to be listed) since we first started doing Rotax hose packages. We will modify our package to utilize a .020 orifice restrictor to match the revised documentation that Rotax is planning on releasing.

We have done real world testing on an aircraft that had the .020-.021 restrictor installed and then changed over to the .015 restrictor. There was a slight difference in fuel flow and a minimal/almost negligible difference in fuel pressure.

We have also tested in real world application the difference in restrictor locations between our kit and the stock Vans kit. Location does not appear to have any appreciable difference on fuel pressures.

In short, the reasons that our kit appears to fix the low fuel pressures that SOME RV-12s are having does NOT appear to be due to the slightly smaller orifice restrictor or its location.

We are currently working on assembling a "modification package" which we will provide (***free of charge-see below***) to any customers utilizing our kit. It will consist of a #76 drill bit to enlarge the orifice from .015" to .020". We will offer this to anyone who has EVER purchased a kit from us and chooses to modify their restrictor.

We have modified our website with an order page already. If you go to the front page, it can be found under the "Manuals/Service Tab". We anticipate we will have the drill bits in stock no later than 5-1-2018 (hopefully sooner) and will enable online ordering as soon as we have them.

As always, thank you all so much for allowing us to earn your business.

Steve and Tom

*****FREE***** - Our payment provider doesn't allow $0.00 transactions for security reasons. So, the kit will be sold for $0.01.
 
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