Why do Lycomings start lean?
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Why do Lycomings start lean?
Hi Everyone.
Im just wondering if anyone knows why the Lycoming start process involves cranking while mixture is in the idle cut off position, and advancing the mixture when the engine kicks over, as opposed to Continental where it is started in the full rich position.
In my mind there really doesn't seem to be a lot of benefit in having the throttle in by some made up amount, resulting in the engine revving up way past 1000 on a cold winter morning in the time it takes to get your hand from the mixture to the throttle.
I'm just wondering what might be the reason for this starting process.
Im just wondering if anyone knows why the Lycoming start process involves cranking while mixture is in the idle cut off position, and advancing the mixture when the engine kicks over, as opposed to Continental where it is started in the full rich position.
In my mind there really doesn't seem to be a lot of benefit in having the throttle in by some made up amount, resulting in the engine revving up way past 1000 on a cold winter morning in the time it takes to get your hand from the mixture to the throttle.
I'm just wondering what might be the reason for this starting process.
What model Lycoming engine are you comparing with what model Continental engine?
Some Lycomings are fuel injected, and some are not.
Some Continentals are fuel injected, and some are not.
The 'standard' Lycoming fuel injection system is a 'mass airflow' system.
The 'standard' Continental fuel injection system is a 'continuous flow' system.
This is one of the reasons for the inherent dangers in the old wives' tales that circulate.
Some Lycomings are fuel injected, and some are not.
Some Continentals are fuel injected, and some are not.
The 'standard' Lycoming fuel injection system is a 'mass airflow' system.
The 'standard' Continental fuel injection system is a 'continuous flow' system.
This is one of the reasons for the inherent dangers in the old wives' tales that circulate.
Roger.
You will learn lots if you do some research on the 'standard' fuel injection system fitted to Lycoming injected engines and the 'standard' fuel injection system fitted to Continental engines.
They are different.
This might explain the different starting methods.
Let us know what you find out.
You will learn lots if you do some research on the 'standard' fuel injection system fitted to Lycoming injected engines and the 'standard' fuel injection system fitted to Continental engines.
They are different.
This might explain the different starting methods.
Let us know what you find out.
Ilikeflying:
If that is what happens to you, then you aren't doing it right. Try a little less throttle (1/4 inch starting point) and you should end up with the rpm around 1000 - 1200 just after it catches.
At least on the C172 I am occasionally privileged to fly, that is what it does after about Five blades.
In my mind there really doesn't seem to be a lot of benefit in having the throttle in by some made up amount, resulting in the engine revving up way past 1000 on a cold winter morning in the time it takes to get your hand from the mixture to the throttle
At least on the C172 I am occasionally privileged to fly, that is what it does after about Five blades.
Why do Lycomings start lean?
You could also do yourself a huge favour and track down a copy of the Lycoming Flyer Key Reprints. This document consists of a collection of operating tips by Lycoming staff.
You'll find lots of links on the web, here's one I found:
http://www.lancaironline.net/booksto...ming_flyer.htm
http://11hc.44rf.com/manuals/engine-...y_reprints.pdf
You'll find lots of links on the web, here's one I found:
http://www.lancaironline.net/booksto...ming_flyer.htm
http://11hc.44rf.com/manuals/engine-...y_reprints.pdf
Last edited by roundsounds; 24th Aug 2015 at 08:05.
roundsounds, the Airvan is Lycoming powered and most certainly does call for Mixture ICO to start. This is the only properly Lycoming powered Aircraft I've flown though, had a couple here and there changed over so obviously the POH didn't reflect the different engine but I still start the Lycomings with ICO and Continentals with Mixture Rich and haven't encountered too many issues (At least none that I'd attribute to the engine rather than my own mistakes!).
Leadie,
Do you know of any good publications on the subject? I'm interested myself and know the Conti way of doing things but not the other too well. I've had a google but haven't come up with much credible info. Cheers.
Do you know of any good publications on the subject? I'm interested myself and know the Conti way of doing things but not the other too well. I've had a google but haven't come up with much credible info. Cheers.
God, you see some crap on here!
Every fuel injected Lyc I can recall, and yes I have flown a few over the last 40 yrs, starts (cold and hot) with the mixture in idle cut-off - by the POH.
Why? Dunno - who cares - it works!
I fly lots of different aeroplanes, mostly post-maintenance test flights. Some types I have lots of time in, some very little or little recent time, and some I have never flown before (ie Expedition 350 - look it up - there is only one in Oz).
If in doubt - do it by the book - generally works fine for me!
Dr
PS - There is an exception to every rule, and in this case it is hot starting an IO520 Bonanza with a single speed (high) fuel pump!
Every fuel injected Lyc I can recall, and yes I have flown a few over the last 40 yrs, starts (cold and hot) with the mixture in idle cut-off - by the POH.
Why? Dunno - who cares - it works!
I fly lots of different aeroplanes, mostly post-maintenance test flights. Some types I have lots of time in, some very little or little recent time, and some I have never flown before (ie Expedition 350 - look it up - there is only one in Oz).
If in doubt - do it by the book - generally works fine for me!
Dr
PS - There is an exception to every rule, and in this case it is hot starting an IO520 Bonanza with a single speed (high) fuel pump!
Ilikeflying: In my mind there really doesn't seem to be a lot of benefit in having the throttle in by some made up amount, resulting in the engine revving up way past 1000 on a cold winter morning in the time it takes to get your hand from the mixture to the throttle.
As the engine fires set the RPM with the throttle then set the mixture to full rich. This way there is no excessive revs as you start.
The engine will run for several seconds before you need to advance the mixture.
The method I use for a Lycoming fuel injected engine that works every time is,
Cold start :
Set full throttle and mixture
Prime till fuel flow gauge rises and stabilises
Mixture to Idle Cut Off
Set Throttle to idle
Hand on throttle and crank engine.
As engine fires up set RPM
Mixture to Full Rich
From a cold start I've never known an engine not to start first time using this method.Prime till fuel flow gauge rises and stabilises
Mixture to Idle Cut Off
Set Throttle to idle
Hand on throttle and crank engine.
As engine fires up set RPM
Mixture to Full Rich
Hot Start
I find hot starts are not generally as easy as a cold start.
The need to prime depends on how long since shut down.
If it's only a couple of minutes I don't prime at least initially.
If in doubt don't prime for the first attempt
If priming is required prime till fuel flow gauge starts to rise.
Mixture to Idle Cut Off
Set Throttle
Start cranking while slowly advancing throttle (go to full throttle if necessary but be ready to close it back to idle as soon as the engine fires).
As engine fires set throttle
Mixture to Full Rich
Don't crank for more than 20 seconds.
If the engine doesn't start first time, and you haven't primed to start with, prime till fuel flow gauge starts to rise.
If it's only a couple of minutes I don't prime at least initially.
If in doubt don't prime for the first attempt
If priming is required prime till fuel flow gauge starts to rise.
Mixture to Idle Cut Off
Set Throttle
Start cranking while slowly advancing throttle (go to full throttle if necessary but be ready to close it back to idle as soon as the engine fires).
As engine fires set throttle
Mixture to Full Rich
Don't crank for more than 20 seconds.
If the engine doesn't start first time, and you haven't primed to start with, prime till fuel flow gauge starts to rise.
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I have a pretty good answer, which is not backed by any documentary evidence, but is just from observation of the systems and the actual goings on in the systems…….but, I suspect another "non expert" on prune might like to explain it as we have discussed this matter before.
I am surprised he has not piped up yet.
27/09
May I suggest your cold / hot starts should be;
Cold start :
Set full throttle and mixture YES
Prime till fuel flow gauge rises and stabilises YES Or count 1-2-3-
Mixture to Idle Cut Off YES
Set Throttle to idleYes, or crack it just a fraction, idle may be a bit low (fully closed) so just about where you think 1000 RPM would be
Hand on throttle and crank engine. No hand on throttle, just on the mixture
As engine fires up set RPM As engine fires roll the mixture up….just about half way, usually no more then let the rpm settle and lean to just past peak ROM…Job done!
Mixture to Full Rich Never required on the ground until you line up to go
From a cold start I've never known an engine not to start first time using this method.
Hot Start
I find hot starts are not generally as easy as a cold start. They are easier (refer above and delete the prime), if it is a genuine hot start, say after land/refuel, simply leave the throttle in the 1000RPM idle/taxi position and crank, at the first cough roll the mixture in as per above.
you may need the boost pump after that if there are any vapour locks.
The need to prime depends on how long since shut down. Yeah and that usually is a few hours. 30 minutes is a hot start except for kiwi's in winter
Hope that helps!
I am surprised he has not piped up yet.
27/09
May I suggest your cold / hot starts should be;
Cold start :
Set full throttle and mixture YES
Prime till fuel flow gauge rises and stabilises YES Or count 1-2-3-
Mixture to Idle Cut Off YES
Set Throttle to idleYes, or crack it just a fraction, idle may be a bit low (fully closed) so just about where you think 1000 RPM would be
Hand on throttle and crank engine. No hand on throttle, just on the mixture
As engine fires up set RPM As engine fires roll the mixture up….just about half way, usually no more then let the rpm settle and lean to just past peak ROM…Job done!
Mixture to Full Rich Never required on the ground until you line up to go
From a cold start I've never known an engine not to start first time using this method.
Hot Start
I find hot starts are not generally as easy as a cold start. They are easier (refer above and delete the prime), if it is a genuine hot start, say after land/refuel, simply leave the throttle in the 1000RPM idle/taxi position and crank, at the first cough roll the mixture in as per above.
you may need the boost pump after that if there are any vapour locks.
The need to prime depends on how long since shut down. Yeah and that usually is a few hours. 30 minutes is a hot start except for kiwi's in winter
Hope that helps!
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well at the point of making a point and I don't care what you all think this is how I do it for both lyc and tcm with injection
extreme cold
prime
get out of the cockpit
pull through the eng half a dozen times
crack throttle (small crack just over idle)
mixture ico
crank and on start slowly increase mixture to approx. half way.
as it clears increase to full mixture.
increase throttle as require to 1000
normal cold start
as above with out the pull threw
however you should always pull threw before any start.
if you have started and oil temp and engine is warm as above but just with a smaller prime. hand on boost pump if it requires more
most times my starts don't go over 800rpm and start 1st time every time unless there is a proplem
I never have to touch the throttle on start up
now I only start and run engines all but every day and more than once. so that's how I do I really don't care if you don't and ill guess ill get heaps of flack saying I don't know what im doing blah blah but when you start as many engines as is do well then tell me what to do.
extreme cold
prime
get out of the cockpit
pull through the eng half a dozen times
crack throttle (small crack just over idle)
mixture ico
crank and on start slowly increase mixture to approx. half way.
as it clears increase to full mixture.
increase throttle as require to 1000
normal cold start
as above with out the pull threw
however you should always pull threw before any start.
if you have started and oil temp and engine is warm as above but just with a smaller prime. hand on boost pump if it requires more
most times my starts don't go over 800rpm and start 1st time every time unless there is a proplem
I never have to touch the throttle on start up
now I only start and run engines all but every day and more than once. so that's how I do I really don't care if you don't and ill guess ill get heaps of flack saying I don't know what im doing blah blah but when you start as many engines as is do well then tell me what to do.
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just to add.
slowly increase the mixture, not fast not extremely slow to half way then then you will hear it clear.
start the right engine 1st
why
so you can hear it.
then the left
why
cause you can hear it cleaner because its closer to you.
you will notice engineers always start r/h then l/h
so today I started two c400 serries engines that 4engines in total.
the 1st aircraft 10 c oat normal cold start 750 rpm both engines
2nd aircraft approx. 24c 740 both engines on start
happy days
slowly increase the mixture, not fast not extremely slow to half way then then you will hear it clear.
start the right engine 1st
why
so you can hear it.
then the left
why
cause you can hear it cleaner because its closer to you.
you will notice engineers always start r/h then l/h
so today I started two c400 serries engines that 4engines in total.
the 1st aircraft 10 c oat normal cold start 750 rpm both engines
2nd aircraft approx. 24c 740 both engines on start
happy days
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I knew it!!!
....and here's silly me all these years thinking the RH Engine was always started first in case there was a fire in the engine on start up which would then mean exiting the aircraft past the unstarted (and not on fire) LH Engine which would be the safest way out.....
I'm glad that's all cleared up now....
Stiky
....and here's silly me all these years thinking the RH Engine was always started first in case there was a fire in the engine on start up which would then mean exiting the aircraft past the unstarted (and not on fire) LH Engine which would be the safest way out.....
I'm glad that's all cleared up now....
Stiky
Yep and in the PA31 you started the right first after pushing down the gear lever to check the hydraulic pump........it's been 25 years but I think that was a procedure????
Someone will correct me I'm sure
Someone will correct me I'm sure
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mixture ICO
The fuel lines are pressurised with the pump whilst the mixtures are at rich, pumps turned off and then mixtures to ICO before start, otherwise the engine (s) WILL flood!!
Jabba,
In my experience the injected Lycomings I'm most familiar with have been much much easier to start cold than warm. It's almost impossible to stuff up a cold start but I've seen plenty of botched hot starts. There's one flying school not far from here who's students seem to have no end of bother with hot starts on their injected C172's. However like anything YMMV.
Also I have a lot of experience with pilots new to an aircraft and or fuel injection and they tend to be ham fisted with starts usually having too much throttle set The OP also mentioned high RPM at start up. That is why I consider having your hand on the throttle instead of the mixture is a much better idea.
If you're flying that aircraft all the time then you'll know exactly where to set the throttle but there's a lot who don't.
There is no need to be in a hurry to advance the mixture.
I agree there isn't generally a need to go full rich until you're ready to roll.
In my experience the injected Lycomings I'm most familiar with have been much much easier to start cold than warm. It's almost impossible to stuff up a cold start but I've seen plenty of botched hot starts. There's one flying school not far from here who's students seem to have no end of bother with hot starts on their injected C172's. However like anything YMMV.
Also I have a lot of experience with pilots new to an aircraft and or fuel injection and they tend to be ham fisted with starts usually having too much throttle set The OP also mentioned high RPM at start up. That is why I consider having your hand on the throttle instead of the mixture is a much better idea.
If you're flying that aircraft all the time then you'll know exactly where to set the throttle but there's a lot who don't.
There is no need to be in a hurry to advance the mixture.
I agree there isn't generally a need to go full rich until you're ready to roll.
ACMS: Yep and in the PA31 you started the right first after pushing down the gear lever to check the hydraulic pump........it's been 25 years but I think that was a procedure????
Someone will correct me I'm sure
Someone will correct me I'm sure
Avoid imitations
Years ago I instructed / flew Lycomings, RAF fuel injected type.
I was led to understand that heat soak from the engine could cause expansion in the fuel system and fuel to enter the inlet manifold after shutdown, tending to over prime the engine. So deliberately restricting the fuel flow on start was a way of avoiding over enriching the mixture.
I was led to understand that heat soak from the engine could cause expansion in the fuel system and fuel to enter the inlet manifold after shutdown, tending to over prime the engine. So deliberately restricting the fuel flow on start was a way of avoiding over enriching the mixture.
