After Fire: A follow-up (we were lucky).

[Bob E]

Eagle1671's after-fire turned out to be a cracked engine mount.  Problem diagnosed and fixed.  Great outcome!   But let's return to the subject of after-fire. 

Experienced Mooney owners already know about this, but since there are a fair number of new folks on the forum, let me describe a dangerous situation that is easily avoided.

With my carbureted M20C there have only been a couple of times I've had issues with fuel burning somewhere other than inside the cylinders.  One time was years ago when probably I didn't pull the mixture control completely during shutdown, and got a backfire on startup that blew out a muffler baffle.  Expensive lesson but otherwise harmless.

The other time was recently.  After a long flight my son (who is also a pilot with about 100 hours in this aircraft) and I landed to refuel.  After refueling we decided to park the aircraft.  My son was at the controls and I stayed outside and went over to the tie-down spot to help guide him in.  He cranked the engine but it didn't start at first.  He cranked a couple more times and I walked over toward the aircraft and yelled "lean it out more."  He opened the little pilot's window to hear me better and cranked some more -- at which time I saw flames coming out of the bottom of the engine!  I yelled "lean it out, start it NOW!"  He did and the engine then started; that extinguished the flames. It all happened so fast that I hadn't even had time to look for the fire extinguisher (which was close by).  We shut down and inspected for damage - and fortunately nothing. Paint not singed, fabric and nylon fasteners unaffected, etc. The flames had lasted for maybe five or six seconds.

We figured out what happened:  He didn't realize you don't prime a hot engine.  He just went through his checklist, and priming -- that is boost pump on, give the throttle a couple of squirts -- was part of the checklist.  When the engine didn't start the first time, he kept boosting and squirting.  We were fortunate that he finally leaned the engine, which then started immediately. 

Lesson learned:  My fault for not giving him sufficient information.  We revised our checklist.

 

[Boilermonkey]

I usually need one shot to get our M20C started. How many times did he prime it?

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[Bob E]

3 hours ago, Boilermonkey said:

usually need one shot to get our M20C started. How many times did he prime it?

Probably 5 or 6 times.    I usually need one shot for a cold engine, none and half throttle for a hot one.

[Skates97]

Thank you for posting. I have had problems in the past starting my O-360 right after a fuel stop or if I had just shut down. I wasn't pumping the throttle to prime in those situations but would have mixture rich and it would just crank and never start. What I figured out works for starting it hot when just doing a quick re-start either after fueling or when shutting down and then needing to taxi further than I want to push/pull it is:

1. Leave boost pump off
2. Don't pump throttle (as you mentioned)
3. Leave mixture pulled out in cut-off position
4. Barely crack throttle open where I have it for idle
5. Start cranking and at same time slide mixture in, it usually starts on about the second or third blade

[Bob E]

Skates - Yep, that works for me.

[Boilermonkey]

Interesting technique, I'll give it a try. I've been doing several Young Eagle events lately with 6-8 hot starts in a day. Usually a single pump works, but anything that reduces wear and tear....and fire risk, is a good idea.

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[Eagle1671]

That is all very good information!

thanks

[DXB]

2 hours ago, Skates97 said:

Thank you for posting. I have had problems in the past starting my O-360 right after a fuel stop or if I had just shut down. I wasn't pumping the throttle to prime in those situations but would have mixture rich and it would just crank and never start. What I figured out works for starting it hot when just doing a quick re-start either after fueling or when shutting down and then needing to taxi further than I want to push/pull it is:

1. Leave boost pump off
2. Don't pump throttle (as you mentioned)
3. Leave mixture pulled out in cut-off position
4. Barely crack throttle open where I have it for idle
5. Start cranking and at same time slide mixture in, it usually starts on about the second or third blade

This seems likely to work.  My version of a hot start on a C is  to have the mixture only half way in at most, and then to pump once when starting to crank. It starts instantly every time without flooding and may be a tad simpler procedure.

[Hank]

3 hours ago, Skates97 said:

What I figured out works for starting it hot when just doing a quick re-start either after fueling or when shutting down and then needing to taxi further than I want to push/pull it is:

1. Leave boost pump off
2. Don't pump throttle (as you mentioned)
3. Leave mixture pulled out in cut-off position
4. Barely crack throttle open where I have it for idle
5. Start cranking and at same time slide mixture in, it usually starts on about the second or third blade

I just generally push mixture Full Rich, pump throttle once to get fuel into the carb and turn the key. If it's not running in a couple of seconds, then I pump the throttle. It's worked well for 12 years, except when my SOS was on the fritz. Shouldn't take more than 4-5 seconds.