Why is there a fuel selector switch?

[Dan Thomas]

Cars have had intertial fuel cutoffs since the 80's.

Now we need some sort of inertial cutoff for the electric cars, to keep them from catching fire so spectacularly in a collision.

 

[genna]

Definitely makes sense with low-wing and great analogy. I suppose once a tank runs dry an electronic valve could shut it off so the pump only sucks fuel from the tank with fuel remaining. Hey, I can dream.

There are many reasons to have switch. I'll give you a personal one. Once on a long flight(low wing), I had a fuel sender failure in one of the tank. Basically i did not know the remaining fuel in one tank. Only by calculation/guess. Since i didn't want to come to landing on the tank with possibly no fuel in it(or worse going for alternate airport on an IFR flight with unknown fuel), I switch to that tank in cruise and used as much as I thought was in in it. After that I knew what I had on board in the other tank.

The "autoselector" would not even work in this case as it would not know when to switch without that info.

There are times when you do not want to use a specific tank for various reasons. There are also planes with very complicated fueling systems(5 tanks)

 

[genna]

It seems like there's loads of warnings about a plane engine catching fire and what to do if it catches fire. I've never had a car engine catch fire. Airplanes and everything in aviation is supposed to be built to a much higher quality and safety standard than automotive parts, so why are airplane engines catching fire and car engines not? I realize plenty of car engines do catch fire, but I've personally never experienced it and I run the cars I drive harder than 99.99% of drivers.

cars catch fire pretty often actually, even new ones. Not even EVs. My buddy's 1 yo Scion BBQed itself on the parking lot 10 years ago

https://www.usfa.fema.gov/downloads/pdf/statistics/v19i2.pdf

Edit: But the reason there are more warnings in aviation is not because it happens often. It doesn't. It's because of the potential consequences. Car fire - you stop and get out. Even if middle of the road. Plane fire - you need to land first.

 

[smv]

cars catch fire pretty often actually, even new ones. Not even EVs. My buddy's 1 yo Scion BBQed itself on the parking lot 10 years ago

https://www.usfa.fema.gov/downloads/pdf/statistics/v19i2.pdf

Edit: But the reason there are more warnings in aviation is not because it happens often. It doesn't. It's because of the potential consequences. Car fire - you stop and get out. Even if middle of the road. Plane fire - you need to land first.

Besides, after some of the student landings I've seen, an inertial fuel cutoff is the last thing you want in an airplane.

 

[timwinters]

That's what I thought and good to know. I rarely drive a car that's more than a few years old. I also wouldn't be too comfortable owning an airplane that's more than 10 years old. You can't trust the longevity of old things. Plenty of planes flying great that are 30, 40, 50, 60 years old. But you never know when something is going to snap on a machine that age.

I'm a lot more comfortable flying a properly maintained and inspected plane that is 62 years old, like mine is/was, than one that is less than 10. Things were built a hell of a lot better back then.

 

[flyingron]

Well the intertial switch helps. The last few trucks I've owned had electric fuel pumps in the tank. Nice to have something cut off the fuel flow rather than continuing to pump it toward the engine in a wreck. Solve everything? No. But it does solve a problem.

 

[Doug Reid]

To answer the OP : not all airplanes are created equal. I fly an old Bonanza..it had 5 fuel tanks when I purchased it..I removed the 20 gallon aux in the baggage compartment...now I have 4 tanks. The engine has a pressure carb which returns about 3 gph to the left main all the time the engine is running. Each wing has a main tank and an aux. Aux tanks are only used in level flight....you have to burn fuel out of the left main first, to make room for the return fuel. Not as complicated as it sounds, but definitely requires a fuel selector for all the tanks. To make it interesting...one fuel gage and piano key switches to select the proper tank on the gage.

 

[flyingron]

Many planes with either injected engines or a pressure carb return to one of the mains. A few have a double fuel selector that routes the return to where the fuel is being drawn from It's kind of fun when we're getting ready to run the efficiency /proficiency events in the Navion to hit the boost pump with the aux selected and watch the level in the main come to the rim.

 

[William Pete Hodges]

What about the millions of flights that went without incident?

Okay I'll give you that one, but only if pilots of automatic planes have to log 3hrs xc and 3 landings in mechanical only mode every 3 months... Just like we do.

 

[William Pete Hodges]

That's what I thought and good to know. I rarely drive a car that's more than a few years old. I also wouldn't be too comfortable owning an airplane that's more than 10 years old. You can't trust the longevity of old things. Plenty of planes flying great that are 30, 40, 50, 60 years old. But you never know when something is going to snap on a machine that age.

Airplanes are not automobiles, are not built like automobiles, and are not maintained like automobiles, so you shouldn't apply automotive standards them. If ten years old is unflyable that would ground over 90% of the fleet. Also, you never know when something is going to snap at ANY age. Newer doesn't necessarily mean better, and you haven't got a long service history for comparison of a new type to see if it is likely to last, like you do in older more established types. NEVER buy the first year of a new vehicle until the model or type has a few years on it to verify it isn't a lemon.

My 68 Cherokee had 4400 TTAF in 2004 and I bought it with a zero time SMOH. I flew it for 14 years and it never let me down. When I bought my 64 Mooney it had 2800 TTAF and 800 SMOH. When you own an airplane YOU are responsible to MAINTAIN it PROPERLY. If you consider older airplanes to be unsafe, perhaps airplane ownership is not for you. That means you will be flying unknown airplanes, with unknown service history, maintained by people who may or may not maintain it as well as you would. Maybe you should reconsider flying at all.

Just an observation to get you thinking. This is not meant as an insult, but a learning experience for you.

 

[chemgeek]

That's what I thought and good to know. I rarely drive a car that's more than a few years old. I also wouldn't be too comfortable owning an airplane that's more than 10 years old. You can't trust the longevity of old things. Plenty of planes flying great that are 30, 40, 50, 60 years old. But you never know when something is going to snap on a machine that age.

The average age of the GA fleet is like, 40 years. My plane is around average. Airplane structures are quite robust, and unlike cars, thoroughly inspected and maintained. For some aircraft, critical structural items are life-limited, e.g. Grumman AA-5x spars.

 

[genna]

That's what I thought and good to know. I rarely drive a car that's more than a few years old. I also wouldn't be too comfortable owning an airplane that's more than 10 years old. You can't trust the longevity of old things. Plenty of planes flying great that are 30, 40, 50, 60 years old. But you never know when something is going to snap on a machine that age.

You should view GA airplane vs car age kind of like you view dog years. For every 1 year of typical car use, you can use an airplane about 5 years. 10 yo plane is like a 2 yo car. Yes, there is a discount vs new, but the prices are still up there. And given that many manufacturers/models seized to be made(or made in large numbers) in the late 70s-80s, you don't have as many choices after that

 

[Dan Thomas]

There's another reason for a selector. If you're on a flight where the landing options are limited, and your fuel is just enough for the trip plus the reserve, any major leak means a big problem. If a tank develops a leak, you switch to that tank and burn as much of it as you can before it's gone, saving the good tank until the bad tank is empty.

 

[Dan Thomas]

You should view GA airplane vs car age kind of like you view dog years. For every 1 year of typical car use, you can use an airplane about 5 years. 10 yo plane is like a 2 yo car. Yes, there is a discount vs new, but the prices are still up there. And, given that many manufacturers/models seized to be made(or made in large numbers) in the late 70s-80s, you don't have as many choices after that

Yup. If one limits his flying to <10-year-old airplanes, he won't do much flying unless he has lots of money. A lot of us have a lot of time in old airplanes.

Airplanes don't get driven over rough roads or road salt. They don't get banged up in parking lots or fender-benders. They aren't (usually) run until something breaks (though the number of alternator and vacuum pump failures I see reported on this forum makes me wonder about the average levels of preventive maintenance). A lot of old airplanes get total rebuilds in their lifetimes; not many cars do. It's also illegal to take off in an airplane that isn't running properly or that has any other airworthiness defect. I don't see any laws preventing me from driving my car with its engine misfiring.

 

[flyingron]

Just remember to turn off your GoPro in an accident before you shut off the mags or the fuel.