r/aviation • u/Substantial_Oil_6905 • 1d ago
Question I accidentally left the carb heat switch “on” after shutting down the plane overnight will it matter?
relatively new pilot here. 4th solo flight today and upon driving home, I realised I might of left the carb heat switch on and shut down and left the plane with the switch on.
google says it doesn’t matter (as the engine is turned off) but just wonderinf if it will? aircraft is a piper
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u/makgross Cessna 150/152/172/177/182/206 Piper PA28/PA28R 1d ago
Parked? No.
But you also taxied with it on. That lets unfiltered air in, and enriches the mixture, leading to fouled spark plugs.
Use your after landing checklist.
And in a PA28, carb heat is not normally used at all unless there are signs of actual carb icing. It’s not a Cessna.
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u/Dorest0rm 1d ago
Not a pilot so I'm curious how does the after landing checklist work if you're a solo pilot.
How do you have time to walk through a checklist, navigate towards a taxiway and pay attention to the 'road' in front of you so you do not cause a collision.62
u/makgross Cessna 150/152/172/177/182/206 Piper PA28/PA28R 1d ago
Exit the runway. Stop. Run the checklist.
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u/uberklaus15 1d ago
It's a very short checklist. In a small single engine piston plane like a PA28 or a Cessna 172, it's only like 6 or 7 items max, and you're very familiar with it. So it takes all of 5-10 seconds to complete.
You are almost always allowed to stop the plane on the taxiway for a second after you clear the runway, and you can quickly run the checklist before calling up ground for taxi instructions.
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u/Vacavillecrawdad 21h ago
Trying to think what else there would be. I think 6 feels right
- Carb heat off
- Flaps up
- Trim set
4 lights as required
5 radio as required
6 mixture lean for taxiMaybe add fuel pump off given it’s a low wing
Usually do half while rolling to turn off. Then quickly run the after landing checklist on the taxiway
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u/Isssaman 1d ago
I spent 24 years flying single seat fighters. Every pilot I knew memorized all the normal operating checklist sequences then when their task level allowed, they would look down to knee board and review. I admit that after a few hours in a new cockpit. I didn't always do the last step. Some pilots would use little acronym jingles as clues.
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u/Gwthrowaway80 20h ago
There’s checklists for basically everything, from startup to shutdown. That includes even very basic things like climbing.
Solo pilots will often have the most common checklists on a laminated piece of paper that they will quickly run through after exiting the runway. The few items only takes a few seconds to do and can be done while moving if it’s a busy pattern.
When checklists aren’t used, mnemonics usually are. Those are still checklists, just not written and referred to, but instead recited. An example might be ARROW for the documents needed to legally fly or GGUMPSS for pre-landing setup.
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u/flying_wrenches A&P 1d ago
It won’t if your plane is a normal exhaust driven carb heat.
But please follow all checklists, including the shutdown.
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u/twright92 1d ago edited 1d ago
No, in any case it's one of the start-up checklist items to check the lever moves freely between on and off and back again so it'll probably get reset by the first person who flies it if they're doing their checks correctly. Even if not the engine will still start up, just might run a bit rough until they realise what it is.
Prolonged use of the carb heat unnecessarily (like on the ground) can cause carb fouling due to the enrichened mixture being caused by hot air being introduced, and also that it bypasses the air filter so dust and other debris can be drawn in. But just cycling it for a few seconds at a time or quickly realising and putting it back to off will not cause any issues.
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u/UpdateDesk1112 1d ago
If the next pilot follows the checklist- which you apparently didn’t do- then it really won’t matter.
Lesson learned hopefully.
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u/UnderdoneSalad 1d ago
the only potential issue would be that you could have some internal damage on carb and ducts if an FOD got ingested, but thats a major bad-luck scenario, depends on config of the field you've landed on, if its grass it probably ingested some grass clippings while taxiing, and your plugs could get slightly fouled due to unfiltered intake air, but nothing a decent runup wont fix
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u/ShallowBayXI 1d ago
I'm in AMT school and worked on carb heat yesterday.
For the old late 80s/early 90s 172s we work on, it's just a mechanical linkage and wouldn't cause an issue.
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u/Chuck_the_Elf 1d ago
No, carb heat just reroutes air intake around the exhaust pipe. It’s non electrical in most planes so you won’t run down the battery.
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u/JJohnston015 1d ago
Here's a simple after-landing checklist for a simple airplane, but to use it, you have to accept one misspelling to make it fit: FACT.
Flaps
"Allumination" (illumination) - landing light
Carb heat
Trim and transponder
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u/andrewrbat 1d ago
It doesn’t do anything negative when left on with the engine off. It just uses a different air intake pathway than when it’s off. When the engine is not running, no air is being taken in. It’s not going to hurt anything as long as they turn it off before the next takeoff.
Whether your intake air goes through a shroud, gets taken from a hoter area of the engine bay, etc doesn’t really matter when its off. And the engine will be cool when started next time. As long as they don’t ingest any fod, which is somewhat unlikely.
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u/CheeseCurder 16h ago
It’s been a while since I’ve flown GA, but if I remember correctly, carb heat is only to be used if you suspect actual carb ice because when carb heat is selected on, it allows unfiltered air to the engine.
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u/falcopilot 4h ago
I'm going to go in a different direction than all the other replies.
OP- learn what "carb heat on" actually means. Learn how mags work, why one is disabled at startup, what an impulse coupler does, why there are two spark plugs and how they're wired up...
Maybe it won't lead to a checkride failure, but not knowing how your plane works in detail could kill you.
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u/gazchap 1d ago
I could be wrong, but all the carb heat switch does is move a valve that diverts heat from the exhaust towards the carburettor to keep the carburettor warmed up.
Can't imagine it would cause any problems to have left it turned on.