Lycoming O-360 Shut-down techniques

[Mach1Muppet]

G'day all,

Been reading about O-360 shut down tips especially:

1. Lean, operate at 1200 rpm for 1-minute. (While taxiing?)
2. Operate at 1800 rpm for 20-seconds
3. Reduce to 1200 rpm and kill with mixture.

How true is the above? Has anyone seen the major issues surrounding improper shutdown?

Cheers,
Mach1

[Lead Balloon]

Folklore.

Aggressively lean for all ground ops (such that any attempt to apply more than a little power will result in stumbling rather than increased power). Shut it down by pulling the mixture at idle, as soon as you no longer need the fan running.

(For entertainment purposes, can you post the explanation, by the brainstrust that came up with that 'technique', as to the technical underpinnings for it?)

[Mach1Muppet]

Folklore.

Aggressively lean for all ground ops (such that any attempt to apply more than a little power will result in stumbling rather than increased power). Shut it down by pulling the mixture at idle, as soon as you no longer need the fan running.

(For entertainment purposes, can you post the explanation, by the brainstrust that came up with that 'technique', as to the technical underpinnings for it?)

Thanks a lot for that!

That's just the thing about it, it didn't come with any explanation which is why I wanted to ask!

[Lead Balloon]

That's unsurprising.

I'm not aware of even a folklore-strewn POH that has that 'technique' in it.

Millions of hours of operation of a simple machine designed in the 1940s and still the fertile soil of folklore sprouts new stuff.

Best thing you can do M1M: Fly aircraft with an all-cylinder engine monitor and do some research to understand the implications of the information it's presenting to you.

[Mach1Muppet]

That's unsurprising.

I'm not aware of even a folklore-strewn POH that has that 'technique' in it.

Millions of hours of operation of a simple machine designed in the 1940s and still the fertile soil of folklore sprouts new stuff.

Best thing you can do M1M: Fly aircraft with an all-cylinder engine monitor and do some research to understand the implications of the information it's presenting to you.
Cheers Lead Balloon! Might give that a go in the near future!

[FullWings]

Idle at 1,135RPM for 12 seconds plus 1.5s for every 1,000’ of density altitude over standard. If the engine is aligned within 20 degrees of magnetic north, you can reduce that by three seconds, but only on Tuesdays and Fridays.

Run at 1,750RPM for four seconds while going rich/lean/rich as fast as you can, followed by another five seconds on the left magneto only at 900RPM. Sing the last two lines of “The Star-Spangled Banner” while slowly moving to cutoff, which completes the procedure. If in the Southern Hemisphere, it goes without saying that you should use the right magneto instead.

[Out Of Here]

FullWings ,absolutely brilliant spat my coffee out. LMAO

[Lead Balloon]

That's the juice, FullWings.

Of course, that's just for the injected 360. In the case of the carby version, you add 3.72% to all those numbers and the singing is instead of the last three lines of "Does Your Chewing Gum Lose Its Flavour On The Bedpost Overnight?"

(Mach1Muppet: If someone advises you to carry a metric shifter and a left handed screw driver in your flight bag, be dubious.)

[43Inches]

If in the Southern Hemisphere, it goes without saying that you should use the right magneto instead.

No need, magnetos sold in the southern hemisphere have had their labeling swapped around so L = R anyway. CASA mandated that all Ls are Rs so that trans hemispherical alignment of cross pollinated rules infusion could occur. This is to avoid confusion when preforming shut downs and mid flight toilet breaks. The only issue is when you cross the Andes backwards flying the pacific route to Australia in a Canadian modified rig then you have to consider what you said carefully.

Of course, that's just for the injected 360. In the case of the carby version, you add 3.72% to all those numbers and the singing is instead of the last three lines of "Does Your Chewing Gum Lose Its Flavour On The Bedpost Overnight?"

Don't forget to modify the inverse landing distance by 3 as per CASA holiday choir rules chapter 12.3. I had heard the designer of the O-360 was Sino-Austrian-Cherokee of decent, so singing "Botswanan Lullabies" might be more appropriate.

[ahramin]

I was similarly skeptical when I heard of this procedure.

Actually, it's good advice. The lead scavenging agents in 100ll do not work at the combustion temperatures at idle. Leaning on the ground will reduce the quantity of lead built up, but will not remove the lead build up. The 20 second run at 1800 RPM gives a high enough temperature to activate the scavenging agents and remove lead build up. Basically you're doing a lead cleaning procedure at the end of your flight.

[Lead Balloon]

Solid gold, ahramin. Solid gold!

[43Inches]

So does that mean we do this procedure for all AVGAS piston engines, that is, because its a fuel problem evidently?

[Vag277]

O-360 ÈÍ Series Operator’s Manual Lycoming Part Number: 60297-25 ©2007 by Lycoming. All rights reserved.

10. ENGINE SHUT-DOWN. a. Set propeller at minimum blade angle (where applicable). b. Idle until there is a decided decrease in cylinder head temperatures. c. Move mixture control to the idle cut-off position. d. When engine stops, turn ignition switch to off position.

[Vag277]

O, HO, IO, AIO, HIO, TIO-360 Series Operator’s Manual Lycoming Part Number: 60297-12 ©2005 by Lycoming
9. SHUT DOWN PROCEDURE. a. Fixed Wing. (1) Set propeller governor control for minimum blade angle when applicable. (2) Idle until there is a decided drop in cylinder head temperature. (3) Move mixture control to Idle Cut-Off. (4) When engine stops, turn off switches. b. Helicopters. (1) Idle as directed in the airframe manufacturer’s handbook, until there is a decided drop in cylinder head temperature. (2) Move mixture control to Idle Cut-Off. (3) When engine stops, turn off switches.

[Lead Balloon]

I've always found that the circa 700 degrees C EGTs and 200 degrees C CHTs on the next take off and climb are good indications of temperatures that are preventing 'lead build up'. That and proper leaning. Boroscope and spark plug inspections confirm it.

[Lead Balloon]

O, HO, IO, AIO, HIO, TIO-360 Series Operator’s Manual Lycoming Part Number: 60297-12 ©2005 by Lycoming
9. SHUT DOWN PROCEDURE. a. Fixed Wing. (1) Set propeller governor control for minimum blade angle when applicable. (2) Idle until there is a decided drop in cylinder head temperature. (3) Move mixture control to Idle Cut-Off. (4) When engine stops, turn off switches. b. Helicopters. (1) Idle as directed in the airframe manufacturer’s handbook, until there is a decided drop in cylinder head temperature. (2) Move mixture control to Idle Cut-Off. (3) When engine stops, turn off switches.
Problem is, Vag, that for most fixed wing aircraft the coolest the CHTs will be is on the flare for landing. All taxiing and idling after that will often result in steadily increasing CHTs.

Engine monitors don't lie.

[AbsoluteFokker]

LB's advice about "Aggresively lean on taxi is good" .When others (usually a cross-hire or flying school) used the aircraft, I had mag drop issues which were usually cleared by high RPM runups, leaned for max RPM and left for 45-60 second until reducing revs for second mag check. I attributed this to poor leaning in taxi.

I had a fouled plug on an O-360 at about 400 ft after takeoff - still climbed ok, but really rough running. Underpants were in danger territority. Quick PAN call and early turn to downwind with a very tight base leg for an uneventful landing. $150 coffee at Rottnest canned and I replaced the plug.

[Mach1Muppet]

Idle at 1,135RPM for 12 seconds plus 1.5s for every 1,000’ of density altitude over standard. If the engine is aligned within 20 degrees of magnetic north, you can reduce that by three seconds, but only on Tuesdays and Fridays.

Run at 1,750RPM for four seconds while going rich/lean/rich as fast as you can, followed by another five seconds on the left magneto only at 900RPM. Sing the last two lines of “The Star-Spangled Banner” while slowly moving to cutoff, which completes the procedure. If in the Southern Hemisphere, it goes without saying that you should use the right magneto instead.

Wait just so I get this completely, should I replace star-stangled banner with Waltzing Matilda when operating in Australia?, also does anything to the procedure change when it is a leap year?

What a ripper of a comment this is! Jokes aside thanks all for clearing this up!

[roundsounds]

For the sceptics, the following is an extract from the Lycoming Flyer Key Reprints, page 66 under the heading of Spark Plug Fouling;

“Prior to engine shut-down the engine speed should be maintained between 1000 and 1200 RPM until the operating temperatures have stabilized. At this time the engine speed should be increased to approximately 1800 RPM for 15 to 20 seconds, then reduced to 1000 to 1200 RPM and shutdown immediately using the mixture control."

This is an engine manufacturers recommendation, which hasn’t been adopted by aircraft manufacturers.

Interstingly, the above procedure is identical to the published shutdown procedure for a number of radial powered Yak aeroplanes.

[roundsounds]

Folklore.

Aggressively lean for all ground ops (such that any attempt to apply more than a little power will result in stumbling rather than increased power). Shut it down by pulling the mixture at idle, as soon as you no longer need the fan running.

(For entertainment purposes, can you post the explanation, by the brainstrust that came up with that 'technique', as to the technical underpinnings for it?)

The brainstrust being Lycoming. This procedure is recommended by Lycoming, it can be found on page 66 of the Lycoming Flyer Key Reprints. This is a document containing maintenance and operating tips produced by Lycoming.

the procedure is also mentioned in the following Lycoming Service Letter:

https://www.lycoming.com/sites/default/files/Spark%20Plug%20Fouling.pdf

[roundsounds]

G'day all,

Been reading about O-360 shut down tips especially:

1. Lean, operate at 1200 rpm for 1-minute. (While taxiing?)
2. Operate at 1800 rpm for 20-seconds
3. Reduce to 1200 rpm and kill with mixture.

How true is the above? Has anyone seen the major issues surrounding improper shutdown?

Cheers,
Mach1
Here’s a current service letter recommending this procedure. However, you need to read the entire document and may find it doesn’t apply to the engine / spark plug combination you’re operating.
https://www.lycoming.com/sites/default/files/Spark%20Plug%20Fouling.pdf

[Ex FSO GRIFFO]

And, For ALL of 'That'.....NOBODY YET has mentioned the 'Thronomister' Pressure Equaliser Requirement.....


COME ON..!!!

[lelebebbel]

This is all very interesting to me. With the ever increasing price of AVGAS, I, too, have been considering to shut down my engine at night

[ahramin]

I'm afraid some here may have thought that my comments were sarcastic. The guidance is also found in Shell documentation:

Lead Fouling | Preventing Lead Fouling in Aircraft | Shell Global (https://www.shell.com/business-customers/aviation/aeroshell/knowledge-centre/technical-talk/techart-18-30071600.html?fbclid=IwAR2BPW-ROZ4j2Hx4RFbZtZ_plsRJW_QEyqBMH1tG4MSkzrdkKwNkWVISlGU)

[NutLoose]

Yup run up to clear the plugs before shut down, remember you could have done a longish taxy back at low RPM before shut down, so clearing the plugs is always a good thing.

[Lead Balloon]

It’s all folklore.

Plenty of folklore has been produced by piston aero engine manufacturers and others.

There are ways to find out if there’s ‘lead build up’ and fouled plugs due to the method of operation.

Fouling due to long taxi at idle is due to an overly-rich mixture. If it’s overly-rich at 1,000 RPM, it’s still overly-rich at 1,800 RPM. That is, unless you lean the mixture…

Aggressive leaning during ground ops and stop the fan as soon as you no longer need it. I remember one fouled plug in 35 years of flying pistons.

[43Inches]

1800 rpm is not a mild power setting so depending on where you park, thrashing the engine just before shutting it down may get an less than amused response from the other owners who just got their planes sand blasted or rock pelted. Let alone you try that on a busy apron. Makes total sense until reality kicks in.

As with LB above never had issues with fouled plugs with healthy engines even without significant leaning on the ground. When a particular aircraft started to foul then we tried plug changes and leaning, have to also consider oil fouling as the engine condition deteriorates. If its fouling seriously in short periods theres other things at play.

[B2N2]

It’s all folklore.

Plenty of folklore has been produced by piston aero engine manufacturers and others.

There are ways to find out if there’s ‘lead build up’ and fouled plugs due to the method of operation.

Fouling due to long taxi at idle is due to an overly-rich mixture. If it’s overly-rich at 1,000 RPM, it’s still overly-rich at 1,800 RPM. That is, unless you lean the mixture…

Aggressive leaning during ground ops and stop the fan as soon as you no longer need it. I remember one fouled plug in 35 years of flying pistons.

THIS ^^^
The quoted publication starts by saying that plug fouling is caused by low temperatures and rich mixtures.
Lean the mixture till anything over 1200-1300 rpm causes a stumble.
Thats properly leaning for taxiing.

[jonkster]

It’s all folklore.
Plenty of folklore has been produced by piston aero engine manufacturers and others.


The manufacturers design and build and warranty the engines and have liability issues for what they make and say.

If they recommend you sing the star spangled banner on shutdown, I personally would think it is at least worth learning the first line or two or maybe knowing how to hum the tune.


There are ways to find out if there’s ‘lead build up’ and fouled plugs due to the method of operation.

Fouling due to long taxi at idle is due to an overly-rich mixture. If it’s overly-rich at 1,000 RPM, it’s still overly-rich at 1,800 RPM. That is, unless you lean the mixture…


I am not sure that is quite accurate. I am not an engineer and may be wrong however I understood that the idle mixture setting is set on the carb (for FI on the throttle body or fuel control unit) independently (to a large extent) from the manual (cockpit) mixture control. I think mixture can vary with RPM (at least between idle and non idle). Over rich at idle does not imply over rich at 1800RPM. Similarly I think the rev recommendation and mixture adjustment more about controlling temperatures in the combustion chamber and how temperature impacts lead deposition. Again I am not an engineer though.


Aggressive leaning during ground ops and stop the fan as soon as you no longer need it. I remember one fouled plug in 35 years of flying pistons.

I was going to say how my memory is heading the same way too as I age but didn't want to take too cheap a shot - FWIW I can't remember exactly how many plug fouling incidents I have had over a similar time period so my memory is probably way worse than yours :)

I have no doubt that you have only had one plug fouling incident in 35 years and that your technique works. In fact leaning on taxi is actually what Lycoming recommend so no argument from me.

I guess where we differ is when the manufacturer recommends a shutdown technique on a particular engine, I don't readily dismiss it. Lycoming have bulletins and service instructions for their engines (as @roundsounds posted). I would not be quick to think they should be ignored.

my 2c

[Lead Balloon]

The effectiveness of all these procedures can and has been proven or disproven. Comparisons can and have been made between the condition of engines run in accordance with them and engines not run in accordance with them. Plugs can and have been removed and inspected. CHTs can and have been monitored. Boroscope inspections can and have been carried out. Comparisons, inspections and monitoring now done over millions of hours and many, many engine monitors.

What you have to realise is that the engine manufacturers base their recommendations on test stand operations. That’s where the recommendation came from about running at idle until the CHTs start dropping. That’s because on the test stand running at ‘high power’ makes the CHTs ‘hot’ then running the engine at idle reduces CHT. But in the real world the coolest CHTs usually are is on the flare and roll after landing. All operations after that – even at idle – usually result in an increase in CHT. The numbers on the engine monitor don’t lie.

You don’t have to be an engineer to work out whether mixture set to full rich is or is not ‘over rich’ at 1,800 RPM compared with 1,000. You can measure fuel flow at each, you can read the engine monitor and you can pull the plugs and inspect them after the differing procedures. A properly set up engine is still ‘quite rich’ at FULL throttle and full rich. You can prove it by leaning the mixture with the throttle set to full: Lo and behold, the engine produces more power! (But don’t do that for long…)

A while ago I was asked to do a 50 hourly oil change and plug inspection a bog standard C172. It spent most of its life taxiing before take off for a few circuits then taxiing after circuits. The red knob was usually touched only twice during each of these flights: full rich before start and idle cut off to shut down.

The plugs were pitch black. I wouldn’t have put them in my lawn mower. Full power during take off and ‘medium’ power – in excess of 1,800 rpm – during downwind before pulling it back for base and final was never enough to ‘overcome’ the consequences of the almost-continuously over rich mixture. 1,800 RPM might make the engine hotter, but it’s still running too rich if the mixture is set to full rich – even more so if you are above MSL ISA.

You can take whatever cheap shots you like. I should have said I also remember numerous failed plugs over 35 years. That’s not the same as fouled plugs. The percentage of plugs that are bad, new out of the box is quite surprising.

Ah, warranty claims. You’re absolutely right. An engine manufacturer would refuse a warranty claim if an operator had failed to comply with the manufacturer’s recommendation to sing the star spangled banner on each shut down. It’s what engine manufacturers do. But that shouldn’t stop us calling out bull**** when it’s bull****.

[AbsoluteFokker]

Another factor: fine wire vs massive electrode spark plugs. O-360 is permitted to have either.

Experience showed that fine wire had less prevalence of fouling issues (but 4 times as expensive) - longer lasting too which is clearly good, but plugs should have been inspected/cleaned/rotated at 100hrly anyway.

[BigEndBob]

So at taxi speed is the carb. only feeding fuel through the slow run idle jets. Seems if carbs. aren't set right there seems a stutter at 1200-1300 rpm. Is this the change over point.
So what's the point leaning carb. engines when taxying.
Never had any problems properly set up carb. ign. and plugs.
But do believe plugs should be pulled at 25, not pushed to 50 hour check as we do.

[Lead Balloon]

What is the basis of your belief that plugs should be pulled at 25 hours rather than 50? Have you observed any difference between a plug pulled at 25 versus 50? If yes, what was the difference? If they’re getting dirty or full of lead gubers in 25 hours, the engine’s being run too rich for too long.

The point of leaning an engine during ground operations is to reduce the risk of plug fouling due to an overly-rich mixture. It can be tricky getting it right on some carb’d engines because the setting is sometimes close to ICO, but with practise it’s easy. The point of “aggressively” leaning is to avoid the possibility of the engine being able to produce much more than idle / taxi RPM. Full throttle/RPM with the engine ‘slightly’ leaned can be ‘bad’.

[43Inches]

Leaning on taxi out would only be advised as far as the run-up bay, once you have completed your pre take-off checks the settings should remain that way until after take-off to avoid things like out of trim or take-off with the mixture leaned. If the aircraft is significantly fouling in the taxi between the run-up bay/area and take-off then you really should get it worked on to alleviate whats causing it.

As for 25 hour checks, god are you trying to nail the final nails in GAs coffin for no reason. Our fleet of Warriors ran 100 hours between checks in ham fisted training with no engine monitoring, simple egt and very mild leaning and the engines exceded TBO except for a few rare cases where a warranty item had to be called on (non operational caused issue). Until AD-ENG-4 this all worked fine and never had any issues related to operating. The carby O-320-D3G was relatively bullet proof, as with the O-235s on 152s. If told we had to pull the plugs every 25 hours you'd get a stern look from the owner. The O-360 series much the same unless its put in a Seminole and then that's more a cam issue and not leaning related, although thrashing it at 1800 rpm just prior to shut down would not help it. I reckon half modern engine issues are to do with them being pulled apart way more often than they need, rather than only when required. Non invasive condition monitoring is the way to go, let it run until it shows signs its not happy, then play with it. Alter operating patterns and process to make it operate longer and happier between techs pulling things apart and changing things.

[ahramin]

It's not just plugs that get lead fouled. Valve problems from lead fouling are much more expensive and time consuming to deal with. Plus plugs get cleaned regularly anyway.

As for not leaning after the run-up is done, what if you don't do a run-up that flight? Personally, I put the mixture rich entering the runway.

[43Inches]

Again pre take-off checks are just that, to set the aircraft up for take-off. You change any of the critical settings after you have run those checks/checklist you set yourself up for a distraction based ATSB appearance. Unless you are doing multiple pre-take off checks before you depart, which just over complicates things. Doing critical actions while entering a runway for departure is not great airmanship as you set yourself up for either missing that action or missing your lookout in a busy environment. Much better pilots than me have succumbed to this so I avoid doing anything but concentrate on lookout and the take-off anywhere near a runway, not worrying if something I should have done stationary well away from there has been done. And not confusing this with a quick scan that everything is where it should be prior to rolling, but that is just conformation, not actions that could be missed in a rush.

Reminds me of Navajos and taking off on Auxillaries, because the operator had some weird method of taxiiing on auxes and if you missed the pre take-off checklist item to change tanks to mains you ended up star centerfold in the crash mags. This happened more than once, I wonder if operators still do this sort of nonsense.

A lot of this is airmanship as well, blasting the parking area at 1800 rpm just prior to shut down makes no sense, and if you are doing this arbitrarily without thinking even worse.

[Lead Balloon]

Now it's valves as well? Once more: boroscope inspections...

I see that Shell's into it as well, here (https://www.shell.com/business-customers/aviation/aeroshell/knowledge-centre/technical-talk/techart-18-30071600.html), e.g.:Engines that have been involved with long, low power descents, or have taxied for some distance, can have quite low cylinder temperatures and this - as we now know - can lead to lead fouling. Again the advice from Textron Lycoming and Teledyne Continental Motors to remedy this is: once on the aircraft is on the stand, the engine speed should be kept between 1000 and 1200 rpm until the engine temperatures have stabilised.I thought it was 1800 rpm. Anyway...

The 'remedy' quoted is based on intuition rather than real world data.

When I start my 360, if I sit at idle the engine gets warmer. Then it gets warmer. Then it gets hotter. Then it gets really hot. And, if I'm stupid enough to sit there idling or taxiing around without taking off, it will get even hotter and finally reach 'red line'. And, after I land and pull off the runway, the engine gets slowly hotter and hotter and hotter and...

[Pinky the pilot]

'Thronomister' Pressure Equaliser Requirement.....

Well Griffo, I'm mentioning it but only because I've heard so many different versions of it that I wouldn't have a bloody clue!!:confused::E

And I find it hard to believe that this thread has progressed so far on what is really a simple procedure.

Which consists of following the instructions that which every single Instructor, Check and Training or Chief Pilot I have ever flown under/for has given me. This has mainly consisted of "Read the Flight Manual" and do what it tells you to do!:=

[roundsounds]

The 'remedy' quoted is based on intuition rather than real world data.

When I start my 360, if I sit at idle the engine gets warmer. Then it gets warmer. Then it gets hotter. Then it gets really hot. And, if I'm stupid enough to sit there idling or taxiing around without taking off, it will get even hotter and finally reach 'red line'. And, after I land and pull off the runway, the engine gets slowly hotter and hotter and hotter and...

Maybe your 360 gets hot due to your aggressive leaning practices..

[BigEndBob]

Leaning on taxi out would only be advised as far as the run-up bay, once you have completed your pre take-off checks the settings should remain that way until after take-off to avoid things like out of trim or take-off with the mixture leaned. If the aircraft is significantly fouling in the taxi between the run-up bay/area and take-off then you really should get it worked on to alleviate whats causing it.

As for 25 hour checks, god are you trying to nail the final nails in GAs coffin for no reason. Our fleet of Warriors ran 100 hours between checks in ham fisted training with no engine monitoring, simple egt and very mild leaning and the engines exceded TBO except for a few rare cases where a warranty item had to be called on (non operational caused issue). Until AD-ENG-4 this all worked fine and never had any issues related to operating. The carby O-320-D3G was relatively bullet proof, as with the O-235s on 152s. If told we had to pull the plugs every 25 hours you'd get a stern look from the owner. The O-360 series much the same unless its put in a Seminole and then that's more a cam issue and not leaning related, although thrashing it at 1800 rpm just prior to shut down would not help it. I reckon half modern engine issues are to do with them being pulled apart way more often than they need, rather than only when required. Non invasive condition monitoring is the way to go, let it run until it shows signs its not happy, then play with it. Alter operating patterns and process to make it operate longer and happier between techs pulling things apart and changing things.
Must be different fuel in Oz. Certainly my experience of engines in the 152 size needed plugs pulling before 50hrs. We have been operating a PA38 it lasts 50 hrs, even with leaning, quite a bit of lead in plugs.

[Lead Balloon]

Maybe your 360 gets hot due to your aggressive leaning practices..It gets hotter after start, quicker, due to my aggressive leaning practices. It gets hotter after landing than it would if I set the mixture to full rich.

I do have to laugh. What is the very purpose of the procedure quoted by the OP? The very purpose?

To make the engine (actually particular bits of it and EGT).... hotter.

I can achieve that (and keep the plugs and valves clean) without having to blast away at 1,800 rpm in some pre-shutdown ritual.

(Where are you located, BigEndBob?)

[43Inches]

Must be different fuel in Oz. Certainly my experience of engines in the 152 size needed plugs pulling before 50hrs. We have been operating a PA38 it lasts 50 hrs, even with leaning, quite a bit of lead in plugs.

This might hold merit as we had a problem with fuel from a particular refinery to do with dyes and tel causing a grime/slime in tanks and eating away at brass carby parts. Resulted in a lot of tanks and fuel systems having to be flushed with water voiding any warranty they might have had. There was also talk of WA AVGAS having some cause in fuel pump wear as opposed to eastern states, leading to a possible cause of engine failure and crash many years back.

Cessna 152 O-235-L2C and N2C are pretty solid engines, never really had any issues with ours if the engine was healthy and they almost always made TBO without much issue. A lot of the flying was circuit work and training area with students, lots of taxiiing and idling with only the odd case of fouling and we are talking thousands of hours a year between several 152s. To put in perspective for each hour of running time .3 was on average ground time, so every 100 hours airframe the engine was running 130 hours, that 30 being low power ground handling. Compared to the Arrow fleet where .1-.2 ground time per hour was average due to the navigation focus on its use. Maintenance was conducted on air-switch. I know early on C152 had a reputation for fouling issues, but I assume engine modifications and carby changes over the years, new plug technologies, may have remedied this. There were definitely more than one carby options for the 152 at least.

[McDuff]

Thanks a lot for that!

That's just the thing about it, it didn't come with any explanation which is why I wanted to ask!

Sorry if I've missed the point, but for the Grob Tutor we started having to run the engine up just before shutdown to reduce fouled plugs. I think . . .

[43Inches]

Actually I had forgotten about the Grob-115C2, which uses the O-360 engine, again a bit of leaning on taxi would remedy any fouling if the engine was healthy. For the engines on the way out a bit more of a run pre take-off might be needed to clear plugs. Never heard of the idea of running at 1800rpm prior to shut down, really not sure it would prevent that much fouling as it would just start building again the next taxi out, as the engine would be at it's coldest then. I do remember sometimes quite a long idle warming the engine as well after start if it was first flight, as LB said some leaning would help it warm as well as preventing fouling.

[griffster94]

Well I’ve got a question guys. And I hope that it’s okay to put here. How much damage do you do to one of these engines, if you shut it down with the key, rather than with the mixture. I recently have found that when me and my friend go flying, that for short stops, such as fuelling, we turn the engine off with the key. And the longer it stops, so if the plane is gonna be parked all day or if we are going to be moving away from it for a long period of time, we shut it down with a mixture. How much damage is it doing by turning off by the ignition rather than the mixture.

[Ex FSO GRIFFO]

Hey Mr Pinky,
Is there a 'computerised' Flight Manual...??

I mean, today's Aces' wouldn't read a lowly 'manual' would they?
I mean, If its NOT 'computerised' then it simply cannot be 'right'?

P M Sent.....Melly Chlistmas,,,,,

[Lead Balloon]

Well I’ve got a question guys. And I hope that it’s okay to put here. How much damage do you do to one of these engines, if you shut it down with the key, rather than with the mixture. I recently have found that when me and my friend go flying, that for short stops, such as fuelling, we turn the engine off with the key. And the longer it stops, so if the plane is gonna be parked all day or if we are going to be moving away from it for a long period of time, we shut it down with a mixture. How much damage is it doing by turning off by the ignition rather than the mixture.
The short answer to your question is: No 'damage'. But I do hope the mixture is then pulled to ICO?

It's actually good practice to occasionally make sure that that the 'OFF' position on an ageing ignition switch in an aircraft with ageing wiring actually grounds both magnetos.

I have to ask, what is the underlying logic of using the key for 'short' stops and the mixture for 'longer' stops? I'm guessing that the engine involved is an injected one that's hard to start when hot?

[43Inches]

Not a good idea to shut down using keys with the traditional updraft carby, that will leave residual fuel in the carby venturi and induction area creating a back-fire risk on restart and fire hazard, as well as a kick risk if the prop is manipulated by hand while moving around. So no direct damage risk, but a few other risks that you need to be aware of. Obviously shutting down with mixture ICO will mean every last drop of fuel/air mix in the induction system will be sucked through the engine and most likely burnt as it dies as the spark is still happening.

The same risk of unintentional kick from manipulating the prop is there with fuel injected as well, as turning off the keys just stops ignition, so the fuel system is still charging. Have to remember vapor locks are caused by hot gaseous fuel in the system, not hot air, so residual fuel in the lines is the enemy, not air.

https://www.boldmethod.com/learn-to-fly/systems/what-is-vapor-lock-and-how-does-it-happen/


Not a bad rundown on what causes vapor locks and simple remedies, this comment was good;

Fred Sweet
Vapor lock also occurs in the fuel control unit and engines mechanical fuel pump. The mechanical fuel pump is easily heat soaked as it is mounted to the case. The electric fuel pump is typically remotely mounted and can still push fuel through the system. You can tell when fuel reaches the injector lines as the fuel flow indicator on many aircraft is located just prior to the fuel distribution block. If you prime the system with fuel mixture and throttle full open, the fuel flow will rise as liquid fuel flow past the fuel flow transducer. Shutting off electric fuel pump immediately after the rise in fuel flow will minimize flooding. At this point starting may still be difficult as the mechanical fuel pump is still heat soaked and can be vapor locked despite getting fuel into distribution lines. Beechcraft have a fuel return line so with the mixture in idle cut off, running the electric fuel pump for 60 seconds, fuel runs through mechanical fuel pump to control unit and back to tank cooling them off. Then a normal start procedure can be used. Many aircraft have a hot start procedure that is effective to the specific model of fuel injected aircraft. In the absence of a specific hot start procedure, if u have flooded engine, try cranking with mixture at idle cut off, throttle full open and gradually bring throttle back till engine fires, then gradually advance mixture. There are many hot start procedures, best is the one in POH if provided

The only addition I'd make to that is knowing which tank the return line flows to, if you have the other tank selected and the return tank is full you might end up pumping fuel overboard.

[Lead Balloon]

Not disagreeing with the substance of what you said, 43, but I do think it’s worthwhile to make the overarching point that this is another circumstance demonstrating why knowledge of the specific systems fitted to the specific aircraft you’re flying is essential. You touch on the reason in what you say about the destination of the return fuel line. Further, this statement from Fred is a bit misleading: “Beechcraft have a fuel return line so with the mixture in idle cut off, running the electric fuel pump for 60 seconds, fuel runs through mechanical fuel pump to control unit and back to tank cooling them off.”

The FCUs on injected TCM engines have a return fuel line. That’s because the mechanical fuel pump is designed to always provide more output than is required for the power setting chosen by the pilot. That applies to FCUs on injected TCM engines whether they are fitted to Beechcraft or any other aircraft brand or model.

Then we have different systems on different serial numbers of the same aircraft type. For example, the return line from the TCM FCUs on some of the early serial number Bonanzas went to only one tank, irrespective of which tank was selected on the fuel selector. That gave rise to the risk you identified. The return line on later serials goes to whichever tank is selected on the fuel selector. That risk is removed on those serial numbers.

Some Bonanzas have a two speed electric aux fuel pump. Some have only one speed. The pressure out of the single speed pump or the two speed pump on ‘HI’ can be sufficient to force fuel through the FCU even with the mixture set to ICO. That results in dangerous puddles of AVGAS when ‘the electric fuel pump’ is run for 60 seconds. I have seen it first hand.

(Research into the specifications for and maintenance instructions for the ‘standard’ FCU on an injected TCM engine showed that the only ICO requirement was that when the FCU is set to ICO on the test bench it lets through less than ’20 drops per minute’ with an input fuel pressure of 10 PSI. The pressure out of the single speed pump or the two speed pump set to ‘HI’ is waay higher than that. Another discovery – which should have been durr obvious but I’m a bit slow – is that the electric aux fuel pump is an airframe component and not an engine component. Why’s that important? Because the engine manufacturers don’t do anything different to e.g. an IO520BA fitted to aircraft X versus aircraft Y, but those aircraft can have different fuel plumbing and electric aux fuel pumps.)

And then there are different kinds of mechanical fuel pumps fitted to the same engine. Some IO520s have an EDP that is connected to the mixture control along with the FCU. Some IO520s have an EDP that has no connection to the mixture control.

In relation to residual fuel after shutting down using the ignition switch, my experience and observation is that on a hot engine any residual fuel will quickly boil off or otherwise evaporate. On an IO520, for example, the valve in the manifold (‘spider’) shuts off fuel to the injector lines when the input from the FCU reduces in pressure due to ICO at idle. But then you can physically hear the remaining fuel in the injector lines boiling and hissing in the lines and venting through the vents on the fuel injectors. The carby mounted in the updraft configuration (e.g. on my 0360) quickly ‘heat soaks’ after shut down. (It's the heat soaking of the EDP on the injected TCM engines that is the primary cause of their hot starting problems. The fuel evaporates in them.)

Cold/er engine? I’d be very wary. But we should always treat props as live and deadly, anyway.

(Don’t get me started on ignition system knowledge…)

[43Inches]

Very aware of the modern EFI/FCU and all that jazz, was just trying to keep it simple from old tech to new, as there was no mention of type. It does get complicated around newer stuff depending on what 'off' does specifically in your system. An old system was just isolating magnetos and that was that, a new system 'off' disengages a variety of things more like a car. The mixture ICO was more for when the systems were completely separate and new systems you have to dig deep to find out what does what when, best just to follow the POH in that regard unless you are prepared to really understand it (which any aircraft owner should to save money and down time).

And yeah any prop should be treated as live. I remember first flying turbo props and have little hairs stand on the back of my neck every time I was rotating the props for damage inspection with the respect ingrained in me from piston flying.

I remember one instructor many years ago was pulling an aircraft forward via the prop from a parked position to avoid blasting into a hangar on start. Started pulling then realised he didn't have the keys, so asked the student via hand signal with a key twisting motion to ask where they were, student took it as 'give it a whirl' and engaged start with his hand still resting on the prop. Instructor had a fat purple fist for a couple of weeks post event, best possible outcome considering he could have easily lost the hand completely.

PS I would like to know if there are any modern types that do have POH shut down methods of simply turning off the key.

[ahramin]

I'm trying to get a FlyEFII electronic fuel ignition and injection system working right now, the only way to shut it down correctly is to remove power to the system. In this case with a key. Interestingly you can shut down just the ignition system which should get the same results and turning the mags off on a legacy engine but this leads to a very rough shutdown since the injectors are still metering fuel into the engine very precisely as the prop slows down. The residual heat in the cylinder ignites the fuel / air mixture at random and everything shakes like the dickens. It sure feels like it could damage something.

Which leads me to Griffster94's question. If you are talking about legacy Lycoming and Continental engines with a mixture cutoff control, the way specified by the manufacturers is to shut down with mixture first, then the key once the engine stops. This minimizes the leftover fuel in the intake and cylinders which is ideal for the reasons listed above. It's not that you're going to damage the engine, it's that you're leaving the engine in a more dangerous state than otherwise possible. Some of the older Continental engines don't have a mixture cutoff control and so the only normal way to shut them down is with the ignition key. I've never heard of those engines being damaged from their normal shutdown procedure.

[Lead Balloon]

What engine are you talking about, here, ahramin, as shaking like dickens?I'm trying to get a FlyEFII electronic fuel ignition and injection system working right now, the only way to shut it down correctly is to remove power to the system. In this case with a key. Interestingly you can shut down just the ignition system which should get the same results and turning the mags off on a legacy engine but this leads to a very rough shutdown since the injectors are still metering fuel into the engine very precisely as the prop slows down. The residual heat in the cylinder ignites the fuel / air mixture at random and everything shakes like the dickens. It sure feels like it could damage something.Is it a 'legacy engine' - which I take to be a 'standard' injected Lycoming or TCM engine - to which you have fitted a FlyEFII system? Or are you talking about a 'standard' injected Lycoming or TCM engine with 'standard' ignition?

[ahramin]

What engine are you talking about, here, ahramin, as shaking like dickens?Is it a 'legacy engine' - which I take to be a 'standard' injected Lycoming or TCM engine - to which you have fitted a FlyEFII system? Or are you talking about a 'standard' injected Lycoming or TCM engine with 'standard' ignition?
The FlyEFII system replaces the standard fuel pumps, throttle body, injectors, flywheel, magnetos, and spark plugs. The bottom end and cylinders are standard IO-375.

[Lead Balloon]

Interesting...

I'm guessing you didn't try shutting it down with the mag switch when the engine it was 'standard'?

Does the system retain the standard injector manifold (the 'spider' with the injector tube 'legs')? You say 'pumps' plural. What pumps are they?

On a standard injected engine at idle, switching the mags off will usually result in a reduction of RPM that reduces the fuel pressure out of the FCU and a consequent shutting off of the valve in the injector manifold and, therefore, no more go juice to the cylinders. Maybe the pressure out of the new pump/s(?) remains quite high in the FlyEFII system.

[ahramin]

This particular engine was never standard but I've flown other IO-375s with standard fuel injection. As you say, shutting one down with ignition rather than fuel is normally a non-event as the fuel mixture becomes initially way too rich and then way too lean followed by cutoff as the RPM decreases. It's possible to get a combustion event or two during the shutdown but normally everything just winds down peacefully. On this fuel system everything is completely replaced from the tank pickups all the way to the injector ports on the cylinders. Fuel pressure is provided by a primary fuel pump with a backup fuel pump in parallel that kicks in if the power to the primary fails or if the fuel pressure drops below 20 psi. It doesn't matter what the fuel pressure is though, the injectors will only deliver fuel on the intake stroke.

During an ignition only shutdown the fuel system is still working at 100% all the way through the shutdown. As the MAP increases and RPM decreases the system is adjusting for this and metering the fuel accordingly so it's much more likely on any given power stroke for a combustion event to happen. This is why the system is normally shut down with the key to kill everything at once, injectors and ignition.

[Lead Balloon]

Well there's the cause of the engine shaking like dickens:Fuel pressure is provided by a primary fuel pump with a backup fuel pump in parallel that kicks in if the power to the primary fails or if the fuel pressure drops below 20 psi. It doesn't matter what the fuel pressure is though, the injectors will only deliver fuel on the intake stroke.


During an ignition only shutdown the fuel system is still working at 100% all the way through the shutdown.It actually does matter what the fuel pressure is. There's a reason it's called "idle" cut off. If one of your pumps is pushing fuel at 'high' pressure into that standard TCM FCU at idle, some of it will be getting through the FCU into the manifold and the valve in it will never close to provide that 'clean' shutdown. That, presumably, is why you have to switch the 'whole' FlyEFII system to get a 'clean' shut down.

[ahramin]

Yes Lead Balloon, as stated, that's the cause.

I think we're getting confused about what we're talking about. I thought you were asking about the electronic ignition and fuel injection system that I was referring to, but you keep commenting on my statements in relation to a standard Lycoming or Continental fuel injection system. This is not a standard system. There is no idle cut off. In the system I'm talking about, each cylinder has its own electronic injector that meters fuel into that cylinder based on crank timing, manifold pressure, rpm, throttle position, engine temperature, fuel pressure, fuel trim setting, and exhaust O2 ratio. As long as the fuel pressure is between 20 and 40 psi, the system meters correctly. Fuel pressure is regulated at 35 psi from before start until shutdown, and the injectors will do their thing as long as there is power to them. Once power is removed, no fuel goes into the engine regardless of fuel pressure.

The point was to provide one example of a Lycoming or Continental engine that shuts down with the key rather than the mixture in response to a question in this thread. Another example is a C85 which does not have an idle cutoff in the carburetor.

[43Inches]

Just out of interest, what power loss are we talking here? So if you lose the electrical system in the aircraft does the engine fail, or is it more like larger turbines that have an integrated alternator for engine only systems. The turbine not really requiring the alternator to sustain though if the alternator fails, although you do lose some automated control functions. With a spark and fuel injection related piston that would mean total power loss if your electrics were fried, would make lightning strikes possibly interesting. I've never had great trust in aircraft electrical systems, compared to power plants, like boats everything a plane is exposed to is anti wiring and electronics. And talking of IO-360s, the Arrow engine set-up used to blow/drip oil directly into the alternators reducing their life by about 70%.

[Lead Balloon]

Yes Lead Balloon, as stated, that's the cause.

I think we're getting confused about what we're talking about. I thought you were asking about the electronic ignition and fuel injection system that I was referring to, but you keep commenting on my statements in relation to a standard Lycoming or Continental fuel injection system. This is not a standard system. There is no idle cut off. In the system I'm talking about, each cylinder has its own electronic injector that meters fuel into that cylinder based on crank timing, manifold pressure, rpm, throttle position, engine temperature, fuel pressure, fuel trim setting, and exhaust O2 ratio. As long as the fuel pressure is between 20 and 40 psi, the system meters correctly. Fuel pressure is regulated at 35 psi from before start until shutdown, and the injectors will do their thing as long as there is power to them. Once power is removed, no fuel goes into the engine regardless of fuel pressure.

The point was to provide one example of a Lycoming or Continental engine that shuts down with the key rather than the mixture in response to a question in this thread. Another example is a C85 which does not have an idle cutoff in the carburetor.Ah yes, I was confused. I was labouring under the misconception that you retained the original manifold (spider).

[ahramin]

Just out of interest, what power loss are we talking here? So if you lose the electrical system in the aircraft does the engine fail, or is it more like larger turbines that have an integrated alternator for engine only systems. The turbine not really requiring the alternator to sustain though if the alternator fails, although you do lose some automated control functions. With a spark and fuel injection related piston that would mean total power loss if your electrics were fried, would make lightning strikes possibly interesting. I've never had great trust in aircraft electrical systems, compared to power plants, like boats everything a plane is exposed to is anti wiring and electronics. And talking of IO-360s, the Arrow engine set-up used to blow/drip oil directly into the alternators reducing their life by about 70%.
I have great trust in the electrical systems of most of the the GA aircraft that I fly. Well thought out architectures are simple and reliable and provide for comfortable continuation or termination of the flight after a failure. In fact I've never run across anyone who has had any problem with a GA electrical system that didn't boil down to "The alternator died and I didn't notice until way too late"

On the other hand, this aircraft has a very complex engine and electrical system. The electrical system is powered by two batteries and an alternator. There's a fancy bus manager that should isolate a battery or bus fault and also has an emergency switch to directly connect one battery to the engine bus. The engine system has two independent ECUs, each of which is capable of running the engine. Unfortunately, between electrical system and the engine control system is a single 15A breaker so if that breaker fails, the engine quits with no way to recover it. There are a few additional less probable but still worrying single points of failure. Lightning strikes are not really a concern but nevertheless, trust is low.

[43Inches]

I only mentioned lightning strikes as i'm very familiar with the issues they can cause airliners, from nothing to whole electrical resets, that take a few minutes to sort out. Which is fine if your engine is independent, but it makes me worry if you on top of the electrical problems also had the donk stop until everything sorted itself out. That single 15amp breaker also seems a bit of a failure waiting for Murphy to have the once over. In any case as long as pilot is well versed in picking paddocks (or resolving said problem) then no issue. In theory cars run on for years without electrical issues as well, so I should be more trusting, but something about boats and aircraft makes me think twice.

[cooperplace]

That's the juice, FullWings.

If someone advises you to carry a metric shifter and a left handed screw driver in your flight bag, be dubious.)

Excuse me! I never go anywhere without a left-handed screwdriver!

[Pinky the pilot]

a metric shifter

Never have that problem as I have an AFS shifter.:=

[Ex FSO GRIFFO]

AHA! A 'shifty' character then.....??