Hot starts and engine shut downs

[4RNB]

I'm building out or personalizing my checklists and want some help to internalize and understand engine shut downs and hot starts. I'm coming from C172 where idle power and pull mixture was the shut down and the plane never had a tough time starting back up. I'm now in a bigger better plane, IO-540.

For shut down, I've been told to do the following:
Pull power to 1700 RPM
Dial mixture back 100-200 RPM
Count to 5
Throttle to 1100
Mixture off.

For a hot start within 2 hours:
Don't touch anything!
Master on
Alternator on
Key start
Mixture to half on start, will run rough a few minutes.

Can someone please explain to me what the deal is with hot starts, what is happening in the above as it pertains to hot starts? And what the addition of an electronic magneto does to the mix (later this year I am upgrading one mag).
Thank you.

 

[asicer]

Can someone please explain to me what the deal is with hot starts, what is happening in the above as it pertains to hot starts?

The fuel injection lines are at the top of the engine so are really good at soaking up heat, which adds additional pressure. The "don't touch anything" means that you're relying on the throttle being at the ideal position for a start (1100RPM) and on the pressurized fuel to be sufficient to light off the engine. The mixture to half is probably at or near where you want to be during idle anyway.

And what the addition of an electronic magneto does to the mix

Makes the same process a little smoother and more reliable.

 

[Gilbert Buettner]

I had a Bonanza with the IO-550 engine. The fuel spider on top of the engine absorbed heat, so often there was vapor in the lines to the injectors, which inhibited the start. The book said to run the fuel pump until there was stable fuel flow and then make a normal start. I found that if I started cranking with the throttle open and slowly advanced the mixture it would start fine when the fuel/air mixture was correct.

 

[455 Bravo Uniform]

I’ve not mastered any other hot start technique than to run the fuel pump at idle cutoff for 30 seconds, then normal warm start. Purges the fuel lines of hot vapor and fuel. Hot fuel and vapor get returned to the tank.

 

[ateamer]

I'm building out or personalizing my checklists and want some help to internalize and understand engine shut downs and hot starts. I'm coming from C172 where idle power and pull mixture was the shut down and the plane never had a tough time starting back up. I'm now in a bigger better plane, IO-540.

For shut down, I've been told to do the following:
Pull power to 1700 RPM
Dial mixture back 100-200 RPM
Count to 5
Throttle to 1100
Mixture off.

For a hot start within 2 hours:
Don't touch anything!
Master on
Alternator on
Key start
Mixture to half on start, will run rough a few minutes.

Can someone please explain to me what the deal is with hot starts, what is happening in the above as it pertains to hot starts? And what the addition of an electronic magneto does to the mix (later this year I am upgrading one mag).
Thank you.

A friend was perennially having trouble with hot starts in his Lance (IO-540) until he learned same procedure. Every hot start went smoothly and it fired up right away.

 

[rwellner98]

I'm building out or personalizing my checklists and want some help to internalize and understand engine shut downs and hot starts. I'm coming from C172 where idle power and pull mixture was the shut down and the plane never had a tough time starting back up. I'm now in a bigger better plane, IO-540.

For shut down, I've been told to do the following:
Pull power to 1700 RPM
Dial mixture back 100-200 RPM
Count to 5
Throttle to 1100
Mixture off.

For a hot start within 2 hours:
Don't touch anything!
Master on
Alternator on
Key start
Mixture to half on start, will run rough a few minutes.

Not going to comment on this specific procedure much as it seems to vary based on plane. But I will say that it sounds like the shutdown is designed to set the plane up for the start-up. There really isn't any reason to do any of that stuff except to leave things how you want them for a hot start on that particular setup. If you are going to park the thing overnight, no need to do anything other than yank the mix.

Can someone please explain to me what the deal is with hot starts, what is happening in the above as it pertains to hot starts? And what the addition of an electronic magneto does to the mix (later this year I am upgrading one mag).

I got an emag last year. Game Changing. Engine hot starts almost as easily as cold starts now. If my experience is anything like normal, run, don't walk, to add one.

 

[William Pete Hodges]

I have an IO-360 Lycoming and there is a really good hot start M20J Mooney video where the mechanic Don Maxwell does several hot starts. There is also a really good section about this in the book Aircraft Engine Ooerating Guide by Kas Thomas. That and what I have been told will add up to a lot of information....

An engine can run at various air-fuel ratios but if the air-fuel mixture is either too rich or too lean it won't fire. One of the techniques is to begin cranking too lean and walk the mixture in the rich direction until it starts. This works well for cold start scenario but not for a hot start.

When a fuel infected engine is shutoff while hot, fuel delivery to the injectors stops, but the injector lines, injectors, and injection pump are still full of fuel. As long as the engine is running fuel flowing through these components keeps them cool. After shutdown the hot engine heats up all these components causing the fuel to boil and flood the intake ports as the expanding fuel has nowhere else to go. This means you now have 2 main problems: 1. The intake manifold will be saturated with fuel and the air-fuel mixture will be too rich to fire when you try to restart the engine, and 2. all the fuel lines will be devoid of fuel as the liquid fuel in the lines has boiled off, so the fuel delivery system will have lost its prime.

Problem 1: Assume the intake manifold is too rich to fire, so leave the mixture at idle cutoff. Control the mixture by adding air with the throttle. When you "crack open" the throttle, give it about 2-3 times as much movement as you would normally compared to a cold start. This give the engine more air and will cause the too rich air-fuel mixture to lean rapidly as you crank the engine, moving the air-fuel ratio into the preferred firing range.

Problem 2: The fuel lines and injection pump are devoid of fuel and need to be primed. During a cold start you would typically put the throttle and mixture on the firewall and turn on the electric pump, priming the system for 2-4 seconds. This primes the entire system all the way to the injectors. Then pull both the throttle and mixture back and crack open the throttle to start the engine. When the engine is hot, leave the throttle and mixture in idle and cutoff positions. Prime for 2-3 seconds to prime the fuel injection pump and supply side, but not the injection delivery lines. Then start the engine as described in problem one. Once the engine is running it may take a minute or so to finish priming the injection lines and cooling them off so the engine runs smooth again. This is normal and you will get used to it.

Remember at low throttle settings the air-fuel mixture can be equally affected by throttle or mixture controls. I run LOP and aggressively lean on the ground. I end up using both throttle and mixture controls to fine tune the air fuel mixture at low power.

Hope this helps.

 

[kujo806]

Running the fuel pump with mixture cutoff for 30 seconds only works with continental engines. Lycomings don’t return fuel to the tank like continentals.

 

[Skip Miller]

Running the fuel pump with mixture cutoff for 30 seconds only works with continental engines. Lycomings don’t return fuel to the tank like continentals.

This.

I wish every hot start procedure list started with: “for Continental engines” or “for Lycoming engines” because they are different! -Skip

 

[iamtheari]

This.

I wish every hot start procedure list started with: “for Continental engines” or “for Lycoming engines” because they are different! -Skip

Lycoming is really easy: Attempt the POH hot start checklist twice, then proceed to the POH flooded start checklist.

 

[Clip4]

I'm building out or personalizing my checklists and want some help to internalize and understand engine shut downs and hot starts. I'm coming from C172 where idle power and pull mixture was the shut down and the plane never had a tough time starting back up. I'm now in a bigger better plane, IO-540.

For shut down, I've been told to do the following:
Pull power to 1700 RPM
Dial mixture back 100-200 RPM
Count to 5
Throttle to 1100
Mixture off.

For a hot start within 2 hours:
Don't touch anything!
Master on
Alternator on
Key start
Mixture to half on start, will run rough a few minutes.

Can someone please explain to me what the deal is with hot starts, what is happening in the above as it pertains to hot starts? And what the addition of an electronic magneto does to the mix (later this year I am upgrading one mag).
Thank you.

All I do is reduce RPM to 1000 and pull the red lever, fuel pump on, push the red lever in and start. What 1700, lean, partially leaning and waiting 5 seconds functionally doesn’t do anything. I hear waiving a dead chicken over the cowling while doing a chant thing works.

 

[morleyz]

When I bought my Arrow (IO-360), the previous owner tried to convey some magical checklists for shutdown and hot start and it seemingly never worked. I always ended up at the flooded checklist. My A&P told me the simplest lists:

Shutdown:
Throttle to idle then
Mix (cut)
Music (turn off all electrical loads)
Mags (off)
Master (off)

Hot start:
Master (on)
Throttle slight (about 1200-1400 if I don't touch it after start)
Turn key
Slowly advance mixture until it starts then about 3/4 mix until runs smooth
Lean for ground ops

Haven't gotten stuck with a hard, hot start at all this summer.

 

[camorton]

My first day of T210 ownership I was struggling with a hot start (POH procedure was useless) and a kindly stranger passing by on the ramp showed me this technique (for Contis):

Full rich
Throttle cracked
Turn the key and wait a couple of blades for the engine to fire
Then toggle the boost pump (2-3 seconds) until it's running smooth.

On Cessnas, the boost pump is right next to the ignition switch so you can hit it with your thumb even while you're cranking. So easy and works like a charm every time. I've heard people say you HAVE to run the boost pump for up to two minutes to purge the vapor. Seems like a waste of time and would run down the battery.

C.

 

[Steamflyer]

My first day of T210 ownership I was struggling with a hot start (POH procedure was useless) and a kindly stranger passing by on the ramp showed me this technique (for Contis):

Full rich
Throttle cracked
Turn the key and wait a couple of blades for the engine to fire
Then toggle the boost pump (2-3 seconds) until it's running smooth.

On Cessnas, the boost pump is right next to the ignition switch so you can hit it with your thumb even while you're cranking. So easy and works like a charm every time. I've heard people say you HAVE to run the boost pump for up to two minutes to purge the vapor. Seems like a waste of time and would run down the battery.

C.

For Continentals, usually just run the boost pump until it stops cavitating and pressure stabilizes. Then start with mixture maybe 1/3 out, and while cranking, push in throttle until it fires (often near firewall, be ready to retard quickly), then stabilize around 1200 rpm with boost pump on low until the remaining vapor is gone (about 3-5 minutes). Has worked for 2500 Continental big bore hours at temps up to 117F. This is more or less what's in the manual for the 210. The two minute idea seems to be that one is bringing cool fuel round and around to cool the system, but none gets all the way through the injector lines at ICO, so doesn't seem to make a lot of sense.

Big bore Lycomings are their own beast; when I had one I had a plan for cold, < 20 mins since shutdown, and > 30 mins after shutdown. Had to make a cheat sheet. Those need the mixture to start at ICO and the trick of running the fuel pump does not work as it's a Bendix not a Cont system and they are plumbed and meter air differently.

 

[kyleb]

Running the fuel pump with mixture cutoff for 30 seconds only works with continental engines. Lycomings don’t return fuel to the tank like continentals.

Depends on how the FWF package is configured. You can do what you want on an experimental. My RV-10 and Todd's RV-10 both have fuel bypass valves which allow you to circulate hot fuel out of the engine compartment before start. I never use mine. I use a conventional hot start procedure, which is to pressurize the system with the mixture in ICO, start cranking with the throttle wide open, retard the throttle after a few (half dozen?) blades pass, then advance the mixture as the engine catches.

 

[Pinecone]

I’ve not mastered any other hot start technique than to run the fuel pump at idle cutoff for 30 seconds, then normal warm start. Purges the fuel lines of hot vapor and fuel. Hot fuel and vapor get returned to the tank.

That works on Continentals, but Lycomings don't circulate the fuel the same way.

 

[AA5Bman]

My plane goes into hot start mode super easily - even just restarting after taxiing over to fill tanks is going to be a hot start - so I’ve had to get my technique down. But the good ol’ fashioned two-handed monkey pull (full throttle, mixture full lean, walk the mixture in while cranking) starts it up every time. Usually I’ll get a good burst of power then the engine will ‘die’ while the blades spin, and when they slow down it’ll catch and settle into idle (provided I’ve pulled back the throttle, of course).

The thing that always gives me pause is how quickly that fuel will vaporize! And also, if I do ANYTHING else - god forbid I forget it’s going to be a hot start and run the fuel pump like a cold start… well, then it’s totally effed and nothing will work. Might as well take the cowling off and find a chair, because it’s going to be a while.

 

[flyingcheesehead]

Paging @Ted. @Ted to the white courtesy phone...

 

[flyingcheesehead]

I'm building out or personalizing my checklists and want some help to internalize and understand engine shut downs and hot starts. I'm coming from C172 where idle power and pull mixture was the shut down and the plane never had a tough time starting back up. I'm now in a bigger better plane, IO-540.

For a hot start within 2 hours:

Can someone please explain to me what the deal is with hot starts, what is happening in the above as it pertains to hot starts? And what the addition of an electronic magneto does to the mix (later this year I am upgrading one mag).

I have an IO-550 (Continental) and our fuel systems and hot starting procedures are thus going to be different. So, please ignore the specifics in what I'm posting here, it's been years since I ran an injected Lycosaur.

However, a hard and fast rule like "within 2 hours" seems like it's prone to failure. Things are changing in your engine compartment for quite a while after you shut down, and your technique will likely need to change somewhat depending on how long it's been. The plane doesn't have a timer that it looks at and says "Welp, I'm gonna be a pain unless he waits another 10 minutes".

With the Conti - If I'm starting up again almost right away, I don't have to do anything. There's still fuel almost everywhere there needs to be fuel. Put the mixture back in, crank and she'll probably fire right up.

If it's been a long time and the engine has cooled down to ambient temperature, then it's a cold start.

In between, there is a spectrum. After a few minutes from shutdown, the engine is evaporating all of your fuel inside the engine compartment, but you're not cold either.

Genereally, if there's any doubt, I use Ted's technique for Continentals: Throttle open, mixture cutoff, boost pump on until I hear the "spitting" noises in the fuel tank quit (I always do this on the right tank so my vapor return is just outside the door, which I leave open until I'm done with the boost pump), prime as for a normal start, then turn the pump off, firewall all three engine controls, and crank while slowly but deliberately pulling the throttle back to idle. When it hits the right mixture, it'll catch and you're on your way. (Again, this isn't quite how you should do it on the Lyc.)

I would say that in terms of how long it takes for the lines to get purged, it starts at 0 right when you shut down, grows to the amount of time spent to completely replace the fuel in the lines, and goes back down from there. That's simply due to the amount of fuel that has been vaporized. More time, more vapor, until the engine cools off.

 

[Pinecone]

A while ago I did a lot of formation flying in a friends T-34. We used a flooded start and it always lit off quickly. And we were flying 6 - 8 flights per day.

 

[Warlock]

I had an fuel injected IO 360 you basically had to sacrifice a virgin to get it started some times particularly on hot days if you did not relight within 20 min…only other option was a flooded start if it acted that way…

 

[Ted]

Hey @RyanB @GeorgeC it appears I don't have a sticky with my hot start procedures. If I make a new thread (probably in "Maintenance Bay" where my other stickies are) that covers my hot start procedures for injected Lycomings and Continentals (note: the two procedures are different because the fuel systems are different), will you guys make it a sticky thread?

 

[Ted]

Genereally, if there's any doubt, I use Ted's technique for Continentals: Throttle open, mixture cutoff, boost pump on until I hear the "spitting" noises in the fuel tank quit (I always do this on the right tank so my vapor return is just outside the door, which I leave open until I'm done with the boost pump), prime as for a normal start, then turn the pump off, firewall all three engine controls, and crank while slowly but deliberately pulling the throttle back to idle. When it hits the right mixture, it'll catch and you're on your way. (Again, this isn't quite how you should do it on the Lyc.)

Just to be clear, this is not my technique for hot starts on a Continental. In fact I have never done this technique.

 

[flyingcheesehead]

Just to be clear, this is not my technique for hot starts on a Continental. In fact I have never done this technique.

Interesting. I'm sure I modified it a bit over the years, but my impression is that I learned it from you...

Although, given how tired I was when I posted this I should go back and read the details because it's entirely possible I skipped half the words.

 

[MooneyDriver78]

With Mooneys, after starting if running rough, turn on the electric boost pump to smooth it out.
Also, if expecting to have to hot start, open cowl flaps on approach to cool down the engine, it will also prevent rough running/stalling after landing.

 

[GeorgeC]

Hey @RyanB @GeorgeC it appears I don't have a sticky with my hot start procedures. If I make a new thread (probably in "Maintenance Bay" where my other stickies are) that covers my hot start procedures for injected Lycomings and Continentals (note: the two procedures are different because the fuel systems are different), will you guys make it a sticky thread?

@Ted sure. There is this thread, but its title is too specific:
https://www.pilotsofamerica.com/community/threads/182-hot-start.87080/
, so feel free to make a new one.

 

[flyingcheesehead]

Just to be clear, this is not my technique for hot starts on a Continental. In fact I have never done this technique.

After further review... The purging part is mine, the starting part is yours:

1) Prime like normal (for me it's everything full rich, prime for a few seconds)
2) With the throttle fully open and mixture rich still, crank and pull the throttle back slowly (at a rate of about 5 seconds full throttle to idle)
3) By the time you get to about 1/4 throttle, it should catch

And I'm happy to give you credit, because it works really well. (On Continentals.)

 

[Ted]

To the OP, I have posted a thread with my hot start techniques. These don't require anything special for shutdown - just shut down your engine by pulling the mixture to idle cut-off from a standard idle.

Ted's Hot Start Procedures for Injected Lycomings and Continentals

As long as there have been fuel injected aircraft engines, there have been arguments on the best way to hot start the things, and the primary consensus is that hot starting them is annoying, and for many, relatively inconsistent. You've probably heard dozens of techniques for hot starts, you may...

www.pilotsofamerica.com

@GeorgeC @RyanB please make the above linked thread a sticky.

 

[RyanB]

Hey @RyanB @GeorgeC it appears I don't have a sticky with my hot start procedures. If I make a new thread (probably in "Maintenance Bay" where my other stickies are) that covers my hot start procedures for injected Lycomings and Continentals (note: the two procedures are different because the fuel systems are different), will you guys make it a sticky thread?

Absolutely!

 

[RyanB]

To the OP, I have posted a thread with my hot start techniques. These don't require anything special for shutdown - just shut down your engine by pulling the mixture to idle cut-off from a standard idle.

Ted's Hot Start Procedures for Injected Lycomings and Continentals

As long as there have been fuel injected aircraft engines, there have been arguments on the best way to hot start the things, and the primary consensus is that hot starting them is annoying, and for many, relatively inconsistent. You've probably heard dozens of techniques for hot starts, you may...

www.pilotsofamerica.com

@GeorgeC , please make the above linked thread a sticky.

Done!

 

[4RNB]

Why about Teds talk deserves any more attention? (I don't know his story, why get a sticky, why the Mod attention?)

 

[4RNB]

It's an interesting discussion because my engine manual has a hot start section that says "Because fuel percolates, the system must be cleared of vapor, it is recommended that the same procedure, as outlined in 3-2 (cold engine), be used for starting a hot engine". This is different than what I was told, and different than the checklist that came with the plane.

 

[tsts4]

Like I said over on VAF to this same question, you are going to have to take these various techniques as a starting point and experiment to find the exact procedure that your engine and setup likes. You might get lucky and find one or more of these techniques works as advertised with no modifications. You'll eventually figure it, but it might take some trial and error.

 

[midlifeflyer]

It's an interesting discussion because my engine manual has a hot start section that says "Because fuel percolates, the system must be cleared of vapor, it is recommended that the same procedure, as outlined in 3-2 (cold engine), be used for starting a hot engine". This is different than what I was told, and different than the checklist that came with the plane.

The problem is that starting a hot fuel injected airplane piston has vapor lock issues and people have found various techniques. Even officially, you can find variations. The procedure in some aircraft POH for hot start in a Continental is different than in the Continental engine manual.

For Lycoming IO-360s, the variations are endless, but the "don't touch anything until it catches and them move the mixture control" works quite well as does a variation (which I never understood) where you open the throttle completely doing nothing else before bringing it back to a starting position.

 

[Pinecone]

On Continentals, the throttle Full, Mixture ICO, run the fuel pump works by cooling the fuel system. Recommendations are for 30 or 60 seconds.

To be clear, when I mentioned using Flooded Start for the T-34 IO-550, you started by priming so you know it is flooded. The Throttle Full, Mixture ICO and crank. When it fires, you do the 3 hand dance (one on start switch, one on throttle, one on mixture ).

 

[iamtheari]

When it fires, you do the 3 hand dance (one on start switch, one on throttle, one on mixture ).

This is why I’m morally opposed to big Continentals in taildraggers. It becomes a 4-hand dance and I can only muster 3.

 

[flyingcheesehead]

Why about Teds talk deserves any more attention? (I don't know his story, why get a sticky, why the Mod attention?)

Ted has worked at one manufacturer of GA engines as an engineer, and he has owned and operated a lot of engines 'cuz he likes to have an extra one on every plane he's owned.

Ted knows his stuff, and many of us here have benefited from his techniques. He has earned the respect of the community.

<satire>Plus, nobody is sure they took the ban hammer away when he left the PoA management council.</satire>

 

[iamtheari]

<satire>Plus, nobody is sure they took the ban hammer away when he left the PoA management council.</satire>

We can’t find it anywhere. It’s really scary. Kind of like when Grant was sworn in and they couldn’t find the nuclear football, except that Ted doesn’t have Johnson’s restraint.

 

[xenadu]

Running the fuel pump with mixture cutoff for 30 seconds only works with continental engines. Lycomings don’t return fuel to the tank like continentals.

This is not actually true anymore, at least on the IO-360 used in Cessna 172s from serial number 9491. They added a loop back to the fuel reservoir specifically to help with hot starts.

 

[asicer]

This is not actually true anymore, at least on the IO-360 used in Cessna 172s from serial number 9491. They added a loop back to the fuel reservoir specifically to help with hot starts.

Well whatdya know, I learned something new today.

But not only serial numbers 9491 and up but there's also a mod kit for earlier 172S as well.

https://downloads.regulations.gov/FAA-2012-0846-0004/attachment_5.pdf

EDIT: Poking around a few planes that I know, it would seem that serial number 9491 is approximately around the same time that the G1000 became a thing on Skyhawks.