[RNB]

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.

 

[Carl Froehlich]

Some thoughts:
- After landing your should already have your mixture pulled back to just before the engine dies on lack of fuel. You can tell you are lean enough if you advance the throttle while taxing and the engine bogs down a little. This helps keep the plugs clean and somewhat mitigates stuck exhaust valve problems.
- From this lean position, shutdown is just ~1000 RPM and pulling the mixture to cutout.
- For hot start, crack open the throttle, igntions on (for pMag) and crank. For mag you typically start on just the left mag (e.g. standard key ignition). If the engine does not start to fire, then (and only then) do you slowly advance the mixture until it does fire. This assumes you did not already flood the engine somehow. Starting off advancing the mixture will result in a flooded engine.
- If you do flood the engine, then mixture at cut out, throttle wide open, crank until it fires then throttle back to fast idle and mixture advanced to your lean taxi position.

I run dual pMags and I’ve had people ask me how do I get the engine to fire after a couple of blades during a hot start. The pMags help, but the procedure is the foundation.

Carl

 

[Auburntsts]

The deal with hot starts is fuel boiling off in the injector lines and trying to get back to an acceptable fuel air ratio for starting that’s not too rich or too lean.

I agree with Carl on a general procedure. Also your FI setup can also have an impact.. IMO there is no universal method that’s works 100% of the time for everyone. For hot starts the sweep method that Carl describes is a good place to start. But you’re going to have to experiment and find the sweet spot your engine and setup likes.

I gave the AFP FI system with a purge valve so hot starts are usually a non-issue for me but occasionally I mess up my timing and have to fight it.

 

[bjdecker]

My thoughts -- YMMV and others have their own religion about this as well.

First, some humor -- "Continental Engines have a very well defined hot start sequence...problem is, no one knows what it is..."

**Follows is for lycoming engines with Bendix/RSA style continuous flow injection system**

You need three elements for combustion in the correct ratios at the right time: Fuel, Air, Spark.

When you shut down the engine using the mixture, you essentially cut off all fuel flow from the servo to the injectors. Any residual fuel that remains in that circuit will "boil off" from the excess heat at the top of the engine, resulting in dry injectors, distribution spider, fuel outlet at the servo ( read: no fuel). The engine is sitting there with 0 fuel at the intake ports, so you need to introduce some fuel, but not too much because you don't want an overly rich mixture or it won't start.

Tips --

1. Don't use the boost pump to "prime" or "flood" the engine -- 99% of the time you're just making noise and not accomplishing anything. However, if the fuel is at 0 psi, then use the boost pump to introduce fuel into the engine pump/servo.
2. Use the residual fuel pressure to "prime" the servo, spider, injectors -- do this by setting the throttle @ high idle (1/4 open) and advance the mixture until you observe the pressure start to drop, then hit the starter.

...

Of course, the above process is guaranteed to fail when people are watching, or you're in a hurry, or the battery is about dead, or there is a storming coming in, or....