Leaning Engines

[mad_jock]

Following on from another thread about poorly taught subjects at PPL.

Leaning was brought up. I agree it is badly taught due to lack of experence of instructors in their hour building etc.

How many private pilots do actually lean the engine?

MJ

[Fly Stimulator]

I do.

[Barney_Gumble]

I only started to lean when I bought a share in my current steed last November. Didn't before that because I was sh1t scared of the engine even getting remotely near the point of quitting; even the slightest change in engine tone was not an enjoyable experience.

I know this is incorrect but wasn't taught during PPL, so didn't learn about it until later.

In fact the for the first 15 hours of my PPL training I thought the mixture control was just a way of shutting the engine down :O

Andy

[Chilli Monster]

Always lean - and always fly as high as possible.

Came as a big surprise when on a trip in France a couple of years back I got my Warrior down from 34 litres an hour to 26 (Cruising at FL75). That's a saving worth having.

Just wait until you move onto something like a Seneca. In that you have a fuel flow meter - almost straight after take-off you pull the fuel levers back to 15 gph in the climb - then back further to 10gph in the cruise. Really unsettling the first time you do it as it's totally against everything you were taught in a small single.

[Fly Stimulator]

As you say, it can make a big difference, especially to the wallet.

I flew to Ireland and back at the weekend in an aircraft that made it easy, with all sorts of whizzy computerised displays of fuel flow, egt for each cylinder, and a 'lean assist' function that walks you through the whole process as you do it.

The fuel flow dropped from 12 gph at full rich to just under 9 at best economy flying at around 7,000', which was more than enough to finance a few pints of Guinness.

[Tall_guy_in_a_152]

I lean the Archer above 3500'. It has an exhaust temperature gauge which makes the process easy.

I tend not to lean the 152. I guess that is because:
1. I fly shorter trips.
2. I fly more locally, which means lower altitude (South East airspace).
3. There is no ET gauge, so rely on engine note to lean correctly. No biggy, but that gauge in the Archer is fun to watch. :O

Both aircraft are hired wet.

TG

[drauk]

During my PPL, no. Now, yes - for taxi and cruise. Personally I don't think it is not taught because of a lack of experience of the instructors. I think it isn't taught because ignoring it means one less thing to worry about, it's not tested on, it isn't essential in typical training types, the instructor is not paying for fuel or engines and most training (certainly in the south east) is done at low altitudes.

[MLS-12D]

See this previous thread (http://www.pprune.org/forums/showthread.php?s=&threadid=87203)

[dmjw01]

Leaning has become fairly automatic for me. When I've finished climbing, I level off, accelerate, trim, then reach for the mixture control. Even if it's 1500 feet. The only time I don't lean is when I'm doing circuits or practising manoeuvres that involve high power settings. In an O-300 C172 I get about 25 or 26 litres per hour at 2300rpm.

[FlyingForFun]

Not on my current aircraft. But that's only because it doesn't have a mixture control - it's all done automatically.

I have on every other aircraft. Never really got the hang of using the EGT when leaning - it always seems to lag more than I expect - that's because as a student none of the aircraft I flew had a serviceable EGT guage, so I was only taught the method of leaning till it runs rough then pushing it forward a bit. But the only aircraft I've ever flown with EGT guages that worked all had fuel-flow meters, so I just set the fuel flow recommended by instructors for each phase of flight.

FFF
--------------

[IO540-C4D5D]

Leaning can save you more than 20% in fuel for the same speed. There is NO negative impact on the engine especially if you can lean LOP (lean of peak) where the temps start to fall again.

Full-forward on everything normally means about 125F-150F ROP (rich of peak); that's how engines tend to be set up, for max power and extra cooling (plenty of unburnt fuel) during a full-power climb. But it's silly to cruise like that.

The trouble is that to lean correctly you need adequate engine instrumentation. With that, e.g. an EDM700, you can lean until you see peak EGT and then continue LOP; once LOP there is little additional "mpg" gain because LOP engine power output is nearly proportional to fuel flow.

I am suprised someone here leaning a Seneca during climb - Lycoming specifically prohibit leaning above 75% power so the man must have meant a cruise climb at 75% power or less, and with the airspeed being sufficient for cooling.

Carburreted engines are harder to lean because of uneven fuel distribution, so the onset of vibration tends to be seen earlier. The trouble is that if one leans only part-way to peak-EGT, one could end up in the detonation region (~50F ROP) - although detonation isn't actually likely to happen below 75% power.

A good reference for this type of engine management is Deakin's articles at avweb.com.

[M14P]

I am not aware that Lycoming specifically prohibit leaning - In fact at high elevations and/or high temperatures you will NEED to lean to achieve maximum available power for take-off.

The EDM that IO540 mentions is a fab piece of kit - specifically because the probes are positioned in every cylinder - not just in one. That means that as you lean you can see which cylinder reaches peak first thereby reducing any tendency to run too hot.

I used to fly aircraft with Continental IO 550 engines. That engine was specifically set up to run with very wide throttle settings (full in many cases) and various power settings both lean and rich of peak (by 40 deg F). Interestingly, peak EGT was not approved for any length of time due to this being too hot.

By not leaning you are actually increasing wear on the engine by causing excessive lead build up on the valves which in turn fail to seat properly.

It is also worth noting that most of our piston engines are fuel cooled to some extent (as well as air cooled). The limitaion on leaning your engine may occur way before 40 deg rich of peak if the cylinders fail to cool adequately thru lack of fuel.

I am therefore a great exponent of multi-probe EGT and CHT instruments as well as accurate fuel flow instrumentation. Sadly the CAA make it rather expensive to pursue installation of these devices as far as full certification and approval (and then bang the drum about being a safety regulation group!)

[Ludwig]

I was never given any advice about leaning during my training, and when I asked the owner of the school about it, he said that it's cheaper to burn avgas than to have engines burn due to excess lean running. Don't know if it's true but it sounded plausible to me!

I always lean as necessary on injected engines but don't on non injected engines - don't know why force of habit I 'spose.

How many of youy brave leaners will actually lean back whilst say mid channel in a single- me , I don't touch the damn thing over water, no sir whatever it is coasting out it stays that way:D

[Fly Stimulator]

How many of you brave leaners will actually lean back whilst say mid channel in a single

My Irish Sea crossing was 80nm over water each way and I had the engine leaned to best economy all the way. As I see it, leaning the engine correctly, especially at altitude, brings the mixture closer to the optimum and therefore reduces, rather than increases, the chances of engine problems.

The particular aircraft I was flying makes it especially easy, with a fuel flow meter and egt and cht monitoring for every cylinder, but I'd still make the effort in any machine.

[Dale Harris]

Lycoming are no different to continental in most cases. They don't usually recommend leaning above 75% power, although it does depend on the airframe it is fitted to, the major exception I know of is the lycoming L/TIO 540, where leaning in climb (85%) is acceptable. It might be more useful if the particular model of a/c is mentioned here. For example, the seneca comes with both lycoming (naturally aspirated) engines, (seneca 1) and continentals (turbocharged) 2,3,4, and 5. You can lean the 1 for takeoff if necessary, but NEVER the turbocharged ones for takeoff. It depends on whether it is naturally aspirated or turbocharged.

While we're at it, yes it can be efficient to cruise higher with regard to fuel, but depending upon how you are paying for the aircraft it can be more expensive to do so. Fuel cost is but one facet of the overall picture, and with normally aspirated engines, higher is not always cheaper.

[IO540-C4D5D]

M14P

Yes one needs to lean at high elevations etc but then the engine is nowhere near developing full rated hp. If the airfield is at say 7000ft then the full throttle hp may be only 60% of max rated. So one isn't actually leaning above 75% power.

There are various articles on the lycoming website - sorry I don't have the URLs handy but could dig them up.

Not a problem in the UK :O

What happens with a turbo engine (which would develop max rated hp at 7000ft) I don't know. Do they need leaning at takeoff?

[Tinstaafl]

No leaning for take off in a forced induction a/c. Max horsepower is maintained up to whatever the rated altitude is.

Apart from that caveat, I lean anytime the manual says I can, should or must, at all altitudes including below 1000'.

[willbav8r]

Avweb.com has a great article on leaning (J Deakin I think).

On a similar subject, there is also a pretty good 45 min video sold via Sporty's which gives a lot of info on engine (recip) management, fuel mixtures etc.

[Davidt]

When learning i was tought the old wives tale dont lean til over 3000 and by the way just forget it anyway you've got more important things to worry about!

I didnt know what the red knob did for years i suspect like most.

Then bought into an old cherokee 180 which fouled its bottom plugs if you didn't lean.So started to learn a bit.

biggest learning curve was when i sat behind an IO540 which has a fuel flow. Properly leaned out the difference is 24gph full rich in a nominal 65% cruise as opposed to 12.5gph makes a hell of a difference.

Read Deakin he explains it all. following his advice i just had a EDM 700 fitted what a wonderful toy!

Someone was worrying about detonation in the context of running near peak egt at 75% power at altitude, if you look at most poh's you cannot get 75% power at any setting at that sort of altitude with a normally aspirated or injected engine. i cannot get near 75% at 8K.

certainly my poh expressly forbids lean of peak opperation and so do most folks advise agains trying to unless you also have gamijectors. I have for short periods set lop and it seems to work much cooler engine with little power loss.

Anyone got an opinion on lop running and gami's????

[sennadog]

I hadn't really come across it in the UK other than as a cursory lesson before but freshly arrived back from a trip to SA where many of the airfields are above 3000ft it has now been drummed into me.

My instructor there even made the point about leaning once again whilst cleared for take off and not to allow ATC to become impatient with you whilst this takes place.

[IO540-C4D5D]

Davidt

AFAIK there is no general mechanical reason why a particular engine should not be run LOP. Any such advice is likely based on the standard plane having inadequate engine instrumentation to make it feasible or safe.

LOP, or even peak EGT, may not be achievable in practice if the fuel flow to the cylinders (or, to be more precise, the power developed by the individual cylinders) is badly matched. The result is excessive engine vibration.

I gather that most carb engines can't do LOP for the above reason, while most injected engines can, to varying degrees depending how well the injectors are matched up. Some people are lucky, most not.

GAMI will take your EDM700 data (you have to run a special flight test, details on their website) and sell you a set of injectors which are designed to make *your* engine balanced.

I don't have GAMIs but do fly LOP routinely at 45% to 65% power; what GAMIs would give me is the ability to run LOP at say 75% power. Reports from other GAMI owners suggest you get a smoother engine anyway. Cost about US$800 plus fitting.

There are reports of additional small fuel savings resulting probably from operation with a wide open throttle (e.g. at 8000ft, 65% power) which means the engine can suck the air in more easily.

[GRP]

Davidt (or anyone else who has had an EDM-700 fitted)

I've long thought about getting one of these installed (in an Arrow IV).

JPI quote about 10 hours to install the basic kit on their web site - did yours take that or was it longer?

Can you just replace the existing EGT guage?

Is this a minor mod or a major mod? Currently waiting (and waiting) for CAA signoff of a major mod so not keen to get into this again in a hurry!

I notice you can download data from the unit to a PC. Does that involve getting to the back of it somehow or is there some sort of access from the front? And how long will the unit store data for? It'd be handy of you could download it at every 50 hour check which could be a month or 6 months. I'm quite interested in the data recording capability because my aircraft is rented out and it would be quite useful to try to get a view of what sort of abuse the engine gets!

[IO540-C4D5D]

GRP

The EDM700 has an RS232 port (output only I believe; this "market leading product" is a really crude piece of 1970s technology!) which the installer should bring out onto a jack socket, DB9 or whatever.

You then get their windoze software from their website, and use that to receive the data. The data is compressed binary of some sort and the prog has to decompress it, and it expands each flight into a .csv file, plus you get a .txt file listing all the flights. There is also a program (basically an Excel macro) which displays the temps in a nice graph (although you can do that in Excel as with any other data).

On the EDM you get the option to download all data or just 'new' data (i.e. since the last download). The logging rate is configurable but basically you get of the order of 10-50 hours' of recording.

The UK installed price bears no relation to the US list price. Avionics shops get a nice mark-up for supply and installation. I suppose on a Private CofA plane you could do the really time consuming work (routing the 12-14 thermocouple cables halfway around the world :O ) yourself.

[MEI]

Wasn't taught much about it in the private days, but was teaching it heavily as an instructor. Got tired of getting into an airplane , doing a run up and having the plugs foul. I lean on taxi, sometimes climb (depends on a/c and what altitude I'm going to), and always when I'm pulling 75% power or less, even down low.
When I was flying out of mountain strips in Idaho, Montana and the like you have to lead on take off to get full power. I have never trusted the lead of peak thing. I know some guys in Bonanza's that swear buy it, but it's not for me. The airplanes I usually flew it was a luxury to having a working EGT gage. My usual trick was lean until the engines changes tone, that would be about peak EGT then 3 half turns in. (each half turn is about 25 degrees, so you would be running about 50 -75 rich) Worked about right for most trainers I've flown in. The engine analyers mentioned are sweet but owners get paranoid about 10 degree's of difference in a cylinder. They flew the pants of the thing before with an old standard EGT now they have this toy and try to lean it for the sake of 2$ in fuel. Well the engine is about 30,000$ for the Beech so I'll just stick to a little on the rich side is O.K. for me. I'm not saying the gages aren't useful, just takes some skill to do it right. (which I don't think average joe pilot has, that's not flying the thing all the time) just my .02 cents

[Davidt]

GRP

I only just had my EDM 700 installed and have only "flown" it for a few hours. So far dead impressed so much data. Down side you must have a safety pilot with you, you'll spend too much time staring at the pretty lights :O

I opted for the 700/6/lx which is a package with some optional extras( fuel flow,oat,oil temp) got mine from Harry Mendleshonn for just over £2k. If you look at the web site www.jpinstruments.com they quote 20 hours labour for a standard installation plus 6 hour for each option extra .

I combined mine with an annual and haven't had the bill yet.

Unit comes with a data port at the front + a lead to enable downloads of data to a Palm or Laptop. AQlso get a program to decompress the data and import it into progams like Excell so you can do spread sheets and graphs with it.

My installation is a minor mod, I think you will find that you cannot get rid of any of your original primary instruments as they are part of your Type certification or if you can that will take you into major mod territory.

They do a 701 which is not certified for my plane (Commander 114) which appears to be certified in the states as a primary instrument at least for some types. Contact JP if there is an FAA STC for what you want to do as I understand it the CAA will recognise that as a minor mod.

I ended up with three copies of JP's cd rom training video pm me if you want one.

Good luck

[Chimbu chuckles]

Guys go here for all the info you'll ever need on Leaning. The engine specific articles are in a seperate box a little down on the RHS. Vast amounts of general good airmanship stuff too besides the mixture stuff.

Pelperch Engine Articles (http://www.avweb.com/news/columns/182146-1.html)

I have Gamijectors and an EDM 700 in my Bonanza and run LOP all the time if not too high...climb LOP too if not going high. When cruising high and into a headwind I usually operate ROP to get the TAS up...but above about 7-8000 you can do whatever you like with the mixture nd not hurt your engine.

You CANNOT run LOP (lean of peak EGT) without an all cylinder monitor and, unless you're incredibly lucky and have balanced injectors, without Gamjectors.

Anyway I fly my Bonanza as per Deakin's articles and can categorically state that what he says is spot on.

LOP is easier than ROP and better for your engine.

The link below shows my EDM in cruise at 7500' LOP.The numbers shown are the hotest cylinder...compare the number to the standard CHT next to it. With only the standard gauges you have no idea whatis really going on inside the engine...that's why so few engines make TBO

My EDM (http://www.fototime.com/{C0EF217E-34EA-4888-95C9-FEC87D861808}/picture.JPG)

Not a great piccy as I was in light/ moderate turbulence at the time ducking around CBs over northern NSW heading home to Queensland.

The Data port is at 1 o'clock and the switch at 4 o'clock is for selecting between various scan modes.

Chuck.

[M14P]

Chimbu -
You can run LOP without the EDM - that's why the IO-550 flight manual tells you to do it. In fact you probably have a greater chance of damaging the engine (burning valves etc) if you are not aggressive enough with LOP running since your EGT will be higher.

I agree, however, that the EDM removes all of the guesswork from the equation.

Running at 'moderate' power settings almost eliminates the possibilty of 'overleaning' most engines (i.e. they are happier really lean than over rich) - particulary with regard to worrying about LOP operations. However, I would always urge adherance to the manufacturers handbook for your motor if only to preserve the warranty.

[Chimbu chuckles]

Of course it is possible to run LOP without an all cylinder monitor...in the vast majority of cases it won't be possile without tuned injectors...but why would you want to?

How would you know that all the cylinders have actually passed over to the lean side of peak?

How do you know that the CHT is reading the hottest cylinder?..look closely at the picture I have posted and see that the triplex CHT is reading 330 odd while cylnder 2 & 4 are around 370F.

Without an all cylinder monitor you could easily have several cylinders safely LOP, a couple at peak and a few just ROP...how would you know?

A good mate of mine who owns an Aztec bought himself an EDM760 after flying in my Bonanza but held off on the Gamjectors due costs...he was absolutely astounded at how inaccurate the triplex style CHTs were and how high the actual CHTs got when leaning as per the manual...upwards of 450F on a few cylinders!!

He recently fitted the Gamis to fix that before it cost him an engine.

My IO550b cost AUD40K to overhaul with new Millenium cylinders...+ the cost of buying/installing the Gamis/EDM...probably all up another AUD10K...you just can't afford not to have this technology in the biger bore, injected flat4s and 6s...it's a completely false economy.

In my Beechcraft Flight Manual it specifically states NOT to lean beyond peak...it specifically recommends 50F ROP for 'best economy...it is wrong...even CASA says it is wrong now that they have been to ADA and seen the IO540 running on the test stand at GAMI.

From a VERY senior CASA engineerin dude (hint THE most senior) "We have learned more about what is going on inside these engines in the last little while than inthe last 40 years!"

Warranty?

My EDM records the last 25 odd hours of engine data at 6 second intervals...every EGT & every CHT & Fuel Flow...if it fails and a warranty claim is made I have all the data I need to prove not one limitation has been exceeded.

I have had very experienced engineers tell me that I will damge my engine operating LOP...they can't tell me how, it just 'will'!

Chuck.

Appologies for the missing letters and gaps...think i's time fora new key board:(