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SL-00078 and Updates to RV-12 POH and RV-12iS POH/FTS Published

greghughespdx

greghughespdx

Well Known Member
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Last night we published SL-00078, which covers the operation of the RV-12 and RV-12iS in high-temperature environments and with non-aviation fuels, specifically related to the prevention and recognition of fuel system vapor lock.

We also published updates to the RV-12 POH and the RV-12iS POH and FTS documents to add information about risks related to vapor lock and the need to carry an emergency egress hammer, among other changes.

After a number of vapor-lock-related incidents in a variety of airplanes, industry-wide ASTM requirements were changed to require fuel testing of Light Sport Aircraft. The results of that testing on the RV-12 and RV-12iS, as well as other aircraft and experience, resulted in the necessary changes/additions to the above documents.

Be sure to read the POH and FTS documents as applicable to your aircraft model. The information contained therein is critical safety information that you need to be familiar with. In addition, please read SL-00078, which contains a detailed discussion about vapor lock and the use of different fuels in the RV-12 and RV-12iS aircraft.

Emergency egress hammers are commonly carried in aircraft in case of the need to break the canopy to exit the aircraft in an emergency. Van's has always recommended the use of such devices, and these have been formally added to the POH for both aircraft models.

In the next few weeks, we will publish a video update that covers this topic as well. We will update this thread when that video is posted.

Thank you.

greg​
 
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Ron Singh posted a great presentation on YouTube about this; it includes a clip from a slightly earlier EAA 252 presentation he gave, with Rian Johnson talking about Vans' vapor-lock testing:

https://youtu.be/aKVyA7ROQ6A

Lotta good info about mogas in any plane, not just the -12.
 
I agree with all items and logic listed in this new Service Letter 00087. In my opinion this formal discussion as related to RV-12 is long overdue. This is a topic that is near and dear to my heart. Perhaps the folks who wrote this Service Letter have never experienced vapor lock in flight first hand…. I did. I started a thread to discuss vapor lock with RV-12 / 912ULS two years ago after having a bad day… https://vansairforce.net/community/showthread.php?t=194385&highlight=vapor+lock

In addition to the above thread, I have a few other comments…

  • Everyone who flies RV-12, without exception, needs to be completely aware of risks of vapor lock and mitigation techniques especially with RV-12 ULS Legacy that is very tightly cowled and has very small air inlets. If there is something you don’t understand…. ask for help.
  • Extended taxing downwind will nullify air flow through the cowling. Therefore, avoid as much as possible takeoff / landing to full stop with long taxi back. This will be tough for flight instruction, but a necessary caution.
  • If engine is heat-soaked, run electric pump for several (5) minutes to bring cooler fuel into fuel distribution above hot engine.
  • Leave oil access door open when not flying.
  • Use a cooling fan on oil access door opening when airplane is parked to draw hot air out of cowling.
  • Install higher pressure auxiliary (electric) fuel pump Notification N 18-07-12 and run it 100% of time.
  • Several RV-12 accidents, including one very recently, have earmark of vapor lock. I don’t think NTSB has ever stated vapor lock as probable cause. Hard to prove vapor lock after the fact. Best to avoid at all costs…
 
greghughespdx said:
Last night we published SL-00078, which covers the operation of the RV-12 and RV-12iS in high-temperature environments and with non-aviation fuels, specifically related to the prevention and recognition of fuel system vapor lock.

We also published updates to the RV-12 POH and the RV-12iS POH and FTS documents to add information about risks related to vapor lock and the need to carry an emergency egress hammer, among other changes.

After a number of vapor-lock-related incidents in a variety of airplanes, industry-wide ASTM requirements were changed to require fuel testing of Light Sport Aircraft. The results of that testing on the RV-12 and RV-12iS, as well as other aircraft and experience, resulted in the necessary changes/additions to the above documents.

Be sure to read the POH and FTS documents as applicable to your aircraft model. The information contained therein is critical safety information that you need to be familiar with. In addition, please read SL-00078, which contains a detailed discussion about vapor lock and the use of different fuels in the RV-12 and RV-12iS aircraft.

Emergency egress hammers are commonly carried in aircraft in case of the need to break the canopy to exit the aircraft in an emergency. Van's has always recommended the use of such devices, and these have been formally added to the POH for both aircraft models.

In the next few weeks, we will publish a video update that covers this topic as well. We will update this thread when that video is posted.

Thank you.

greg​
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The RV-12iS POH still has an incorrect spark gap callout (pg. 8.4). It should be .023-.027 for the NGK plug and .031-.035 for the Rotax 297656 plug. I contacted the support team last September regarding this.
 
Greg, inquiring minds are interested to know why Van’s decided to move away from the A6 paper size to 8.5”x11” for the POH, which is definitely NOT user friendly for storage in the aircraft?
 
Bob Y said:
Greg, inquiring minds are interested to know why Van’s decided to move away from the A6 paper size to 8.5”x11” for the POH, which is definitely NOT user friendly for storage in the aircraft?
Click to expand...

Going forward, the POH we provide is actually printed in spiral-bound, fold-flat book form. They are 8.5" tall, 5.5" wide, and (now) full-color booklets. No more binder. It's compact and quite usable. You can also print it from the PDF to that size or another percentage if you like, of course. The old/original binder style is no longer available.

I'll post a couple of photos of the new style book soon.
 
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I just bought 50 gallons of mogas two days ago(93UL, ethanol-free) but I have no idea if the blend is summer or winter. I am in East TN and obviously not quite May 1st yet. It would be great to measure the RVP per SL-00078. Does anyone know of a reasonably priced RVP tester? (if there even is such a thing!) Thanks!!
 
It’s the fuel distribution terminals that are required to start distributing summer-blend gas by May 1st. It takes time for the gas stations to sell off their winter blend and have 100% summer blend in their tanks. That’s why the June 1st requirement for gas stations to be 100% summer blend. But I’ll bet if you ask a clerk at your local gas station if they’re distributing summer vs. winter blend they’ll look at you with a blank stare. That being said, your gas is almost assured to be winter blend. I made my own crude RVP tester with some 3/4” copper pipe, fittings and a plumbing pressure tester, like this one:

CARBO Instruments Gas Test Pressure Gauge 15 Pound, 15 PSI / 100 kPa, 3/4” FNPT Connection, Brass Valve, Chrome Plated Steel Body Assembly. https://a.co/d/fpcB112

A pipe that holds 50 ml, filled with 10 ml of gasoline gives you the correct ratio. Go to YouTube and you’ll find several videos showing the test process. Since we’re just trying to determine winter vs. summer blend, exact values aren’t important - relatively high vs. low pressures will tell us which blend we’ve got. My tester gives me pretty reasonable results.
 
Bob Y said:
A pipe that holds 50 ml, filled with 10 ml of gasoline gives you the correct ratio. Go to YouTube and you’ll find several videos showing the test process. Since we’re just trying to determine winter vs. summer blend, exact values aren’t important - relatively high vs. low pressures will tell us which blend we’ve got. My tester gives me pretty reasonable results.
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Thanks very much Bob, appreciate the info! Paul
 
I unscrew the Schrader valve and use a syringe to add the fuel.
 

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Still a little bit confused

I watched and enjoyed the YouTube presentation, but I'm still a little bit confused as to why Ron experienced vapor lock.

I don't know exactly how the 12's are plumbed, but if the fuel pickup is in the bottom of the tank and sitting in liquid fuel, and the electric fuel pump(s) aren't having to pull fuel uphill, and the liquid fuel is basically free-flowing to the pump inlet, how can they vapor lock or cavitate? Vapor lock can only happen at the pump inlet (suction side) and if the pumps have liquid being fed to them, they're going to pump, regardless of the fuel temperature. Once the fuel exists the pumps, the fuel pressure regulator takes over an maintains a constant 45 psi in the fuel rail and across the injectors.

Those of us that run an SDS or EFII setup and also run car gas, are basically in the same boat. I run car gas in my -8 almost exclusively and I've never once experienced even a hint of vapor lock. It doesn't matter if it's winter or summer, hot starts or cold, high altitude or low, my airplane has never missed a beat.

So is there something about the way the 12 is plumed that's different than the typical SDS or EFII installation, or am I missing something here?
 
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RV-12iS

I have read the SL-00078 document. Wow.

The Rotax 912 ULS has only one fuel line and the Rotax 912iS
has two fuel lines & circulating (cooling).

Why did the RV-12iS Rotax 912 iS Fuel system get compared equally to the RV-12 Rotax 912 ULS model?

They are not the same. Where are the RV-12iS vapor lock stories?

Why no comment on Hight Octane Unleaded Ethanol free fuel?

Call Roger Lee at 520 349-7056
 
I see your profile lists RV-9… so perhaps you are not familiar with 912ULS. This engine has a single fuel delivery system with return flow to the tank (I believe you are calling this circulating / cooling). The comparison to 912iS is an acknowledgement that Vapor Lock is a real concern with elevated temperatures when using winter-blend Mogas where responsibility for safe operation is on the ownness of the pilot / operator. Vapor Lock can happen in any engine including Lyc and Cont when conditions are ripe. Knowledge is the key to safe operation…
 
Mark33 said:
Vapor lock can only happen at the pump inlet (suction side) and if the pumps have liquid being fed to them, they're going to pump, regardless of the fuel temperature.

So is there something about the way the 12 is plumbed that's different than the typical SDS or EFII installation, or am I missing something here?
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Yes, you're missing a lot... RV-12 with Rotax 912ULS has a low-pressure fuel delivery to normally-aspirated carburetors. Fuel lines are run topside on the engine and are easily heat-soaked. Fuel can "boil / vaporize" in the fuel lines and/or carb float bowls.
 
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pstraub said:
I just bought 50 gallons of mogas two days ago(93UL, ethanol-free) but I have no idea if the blend is summer or winter. I am in East TN and obviously not quite May 1st yet. It would be great to measure the RVP per SL-00078. Does anyone know of a reasonably priced RVP tester? (if there even is such a thing!) Thanks!!
Click to expand...

If you don’t mind, we’re do you purchase your fuel?

Thanks!
 
Piper J3 said:
Yes, you're missing a lot... RV-12 with Rotax 912ULS has a low-pressure fuel delivery to normally-aspirated carburetors. Fuel lines are run topside on the engine and are easily heat-soaked. Fuel can "boil / vaporize" in the fuel lines and/or carb float bowls.
Click to expand...

I know that low pressure fuel systems are ripe for vapor lock in a high temperature environment, but I was under the impression that Ron’s fuel system was a high pressure one, which also incorporated a return line. I’ll have to go and watch the video, but I know in his presentation he talked about and showed where his fuel pressure normally runs about 45 psi. but showed where that pressure dropped to around 12-15 when the vapor lock was occurring. I may also be mistaken in thinking that Ron has the iS model. If his has carburetors, I know the fuel can boil in the bowls and the floats can sink.
 
It seems to me that the 912 really would like Swift 94UL or 100R or GAMI 100UL. Fuel costs are a concern and I realize that drives many to mogas along with the increased maintenance cost of 100LL with Decalin. However, maybe we are being pennywise here because a hiccup at 300 ft on take off can get real expensive in a hurry and not just in dollars! - JJR
 
docjjrmd said:
It seems to me that the 912 really would like Swift 94UL or 100R or GAMI 100UL. Fuel costs are a concern and I realize that drives many to mogas along with the increased maintenance cost of 100LL with Decalin. However, maybe we are being pennywise here because a hiccup at 300 ft on take off can get real expensive in a hurry and not just in dollars! - JJR
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For me it's not a cost issue - I don't like putting lead in my airplane (because it's nasty stuff, bad for humans and bad for engines), but the nearest airport with 94UL is 600nm away, and neither 100R and G100UL have hit pumps anywhere yet as far as I'm aware. So mogas is the only remaining option.
 
100LL is a misnomer... it is not low lead. Aviation fuel contains enough Tetraethyl Lead (and then some) to prevent detonation. Detonation would be as Elon Musk says… rapid unscheduled disassembly. Aircraft engines are built very light-weight and barely remain in one piece as it is. In addition, the high lead content is bad for the 9-series gearbox slipper clutch.
 
greghughespdx said:
Going forward, the POH we provide is actually printed in spiral-bound, fold-flat book form. They are 8.5" tall, 5.5" wide, and (now) full-color booklets. No more binder. It's compact and quite usable. You can also print it from the PDF to that size or another percentage if you like, of course. The old/original binder style is no longer available.

I'll post a couple of photos of the new style book soon.
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Greg,


Were you able to get a picture of the new format POH? Is it now available?

Thanks,

Harry Burnette
 
HEB1022 said:
Greg,


Were you able to get a picture of the new format POH? Is it now available?

Thanks,

Harry Burnette
Click to expand...

I’ve seen it, and it’s not possible to replace individual pages when revisions are published. Definitely a step in the wrong direction from my perspective.
 
I ended up getting an A5 soft-sided binder, dividers and punch. Printed it two sided A5 reduced to 95% on 1/2 sheets (8.5 X 5.5) and it worked pretty well for me. Still larger than the previous version, but at least it can be updated now.
 
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