CTLSi Shut Down

[airhound]

Other than it’s not by the POH……..Is there anything harmful to shutting down the engine with the fuel control lever on the panel? Maybe the fuel pump(s) are still trying to work ?

[Anticept]

Air and vapor are not good for injectors. Shutdown by turning off the gas supply will drop pressure until no gas is injected, with the possibility of forming vapor.

[Tom Baker]

The fuel injected Rotax is set up with automotive fuel injection technology. You don't turn the fuel off in your car, and you shouldn't with this either. The other thing to consider is that the lever on the CTLSi controls not one but two valves. By pulling the lever you not only shut off the fuel supply, but you shut off the fuel return path. That might cause some potential unexpected problems.

[airhound]

Tom, I understand, thank you for your expertise.

[airhound]

7 hours ago, Anticept said:

Air and vapor are not good for injectors. Shutdown by turning off the gas supply will drop pressure until no gas is injected, with the possibility of forming vapor.

Thanks for the education Corey.

[airhound]

Good question T. Don’t know, Guessing to reduce standing fuel pressure on firewall forward fuel system components. 

[Warmi]

I got a different model plane but when I bought it one of tips dealer told me was something like…. Don’t even bother with fuel shut off valve , just keep it open all the time - his reasoning was that these things won’t last if I keep turning them on and off every day.

These days I close it only when I do some maintenance and also during annual my mechanic always delivers the plane back with the valve closed so all in all the valve gets exercised maybe 2-3 times per year.

[Roger Lee]

When parking for the day you should turn off the fuel especially in a high wing. The shut off valve was put there for a reason and not just for a fire. I have seen numerous leaks from people who didn't and starting issues too.

Anyone who said don't use it because you'll wear it out.  Well I guess we shouldn't turn the key, check the mags, push on the peddles, pull the heat on, adjust the trim, use the flaps or brakes. I guess if used they'll all wear out. If it rolls on the wheels we'll wear out the bearings too.

That guy's tip was bad for numerous reasons.

[Madhatter]

It is common knowledge that not exercising a shaft with a rubber seal will eventually cause a leak. I see this all the time with aircraft that are not regularly flown. The seals dry out when not exposed to fuel or oil by working them.

[Warmi]

4 hours ago, Madhatter said:

It is common knowledge that not exercising a shaft with a rubber seal will eventually cause a leak. I see this all the time with aircraft that are not regularly flown. The seals dry out when not exposed to fuel or oil by working them.

Ok I do exercise it but is there any benefit of shutting off fuel before it gets to gascolator  beyond just exercising the valve so it stays lubricated ?

[Anticept]

If there's a leak firewall forward, you're far more likely to have a fire for one especially if you don't notice.

I'd take a leak at the fuel valve over a leak in the engine compartment!

[Warmi]

22 minutes ago, Anticept said:

If there's a leak firewall forward, you're far more likely to have a fire for one especially if you don't notice.

I'd take a leak at the fuel valve over a leak in the engine compartment!

Yes but that’s just emergency shutoff which makes perfect sense - the question I have is why would be benefit of shutting it off daily, say at the end of the day ?

[airhound]

WE still haven’t answered the basic question other than, ‘because it’s there’. But why is it there? Why didn’t they just design the system without a valve there?  How about it ROTAX Academia, how about some humbling logic other than, it’s all about exercising a seal, because it’s there?? So, if it’s for keeping the system from leaking at some specific point, guessing, like at that expensive, must change, fuel pressure regulator on a 912iS which probably usually doesn’t leak, but maybe standing fuel gets by it and pools down stream…….do tell, it’s there for some reason. Thank you!!  Doug

[Anticept]

Warmi: sorry, not what I was getting at. Your engine doesn't suddenly become cold when you shut down. Carbs have been known to get sticky needle bowl valves and overflow, for example. It's also possible to get leaky fuel injectors and you might not ever really notice until your oil reservoir is full of gasoline.

It's also possible to have a slow enough leak that it wets some parts under the cowl, but not enough to drip out and be noticed.

These are all astronomically slim things, but the conditions still exist, why not use one more extra measure so you aren't the guy posting on ctflier.com about a fire from a gas leak or a giant gas puddle because all your fuel leaked out through the engine?

[Anticept]

7 minutes ago, airhound said:

WE still haven’t answered the basic question other than, ‘because it’s there’. But why is it there? Why didn’t they just design the system without a valve there?  How about it ROTAX Academia, how about some humbling logic other than, it’s all about exercising a seal, because it’s there?? So, if it’s for keeping the system from leaking at some specific point, guessing, like at that expensive, must change, fuel pressure regulator on a 912iS which probably usually doesn’t leak, but maybe standing fuel gets by it and pools down stream…….do tell, it’s there for some reason. Thank you!!  Doug

It's there because it also acts as an emergency fuel shutoff in case of a fire in the engine bay.

Closing fuel valves after flight has actually been a standard recommendation for decades on small and big aircraft alike as well. As was said, because it exists, it really should be exercised for seal health. You can also tell early on if there is a problem with the valve so that you can get it fixed before you ACTUALLY need it.

This is one of those things where really, just taking the time to do it is the most minor of inconveniences, for the most minor of payoffs. I really can't say much more than listing a bunch of possibilities, but the valve MUST exist for emergencies. Many things have a pilot control in case the automation malfunctions.

[Roger Lee]

I've seen and heard of several CT's that leaked a lot of fuel over night and over a few days when no shut off. The fuel has head pressure and somethings like carb needle valves don't always hold back fuel.

We do things under "best practices" scenarios. Leaving that open is worst practice and leaving it closed is best practice.  

The dealer didn't give good advise.

[Tom Baker]

On 12/22/2022 at 6:53 PM, TheEngineer said:

Is there any reason at all to close the fuel valve on a CTLSi? With the return line being there, what's the benefit of the fuel shutoff, aside from emergency situations?

I ask this because when I picked up my used CTLSi, I made it about 5 hours before the fuel shutoff valve started leaking fuel into the cockpit. I had it rebuilt, but I've since been hesitant to use it in accordance to the regular checklist.

Was it the selector valve, shut off valve, or the return line valve that started leaking? On the CTLSi when you move the lever on the instrument panel it opens or closes two valves in unison. It basically traps the fuel supply in the engine.