Proper Cruise Settings

[Capt. Manuvar]

I'm interested in knowing what you think about the way most PPLs seem to be taught about cruise power settings. Most people seem to taught to fly airpspeed/rpm combination irrespctive of altitude and temperature e.g. 90kias/2250rpm in 152s or 110kias/2400rpm in 4-seaters. The problem is that fuel burn becomes an unknown. Also on a very hot day or at higher altitudes, the 'normal' cruise settings can easily exceed the highest recommended cruise settings, and this isn't good for the engine.
There was an accident not too long ago because someone flew a C152 at 2500rpm and ended up runing out of fuel, his explanation was that he usually flies PA28s and he confused the power settings (still 2500 is a little high for a pa28).
The method I use(so correct me if I'm wrong) is
1. select % power hence fuel flow
2. use POH graphs to find rpm and TAS
3. Calculate IAS
I would be grateful if you could explain how you can vary power and airspeed to take advantage of head/tailwinds.
Thanks
Capt. Manuvar

[Flyin'Dutch']

I'm interested in knowing what you think about the way most PPLs seem to be taught about cruise power settings.
The bare basics, if that. Most instructors have barely been outside the circuit or even know how to teach leaning.

Study the POH and ask questions if things are not clear seems to be the way to learn these things.
Also on a very hot day or at higher altitudes, the 'normal' cruise settings can easily exceed the highest recommended cruise settings, and this isn't good for the engine.
Hot and high means that the engine will produce less power so adjust as per POH.
There was an accident not too long ago because someone flew a C152 at 2500rpm and ended up runing out of fuel, his explanation was that he usually flies PA28s and he confused the power settings
Unfortunately no instant cure for this or instant injection of commons sense available (yet!)

I think most people will work out what power setting they want to use and work out airspeed and fuel burn out from that.
I would be grateful if you could explain how you can vary power and airspeed to take advantage of head/tailwinds.
Broadly speaking you want to fly as short as possible in a headwind and as long as possible in a tailwind so adjust your powersettings for that. Have to say that most folks I think just go for a few standard settings and stick to those.

HTH

FD

[TonyR]

This is very difficult if you are renting a club or school aircraft but the only way is to really know the aircraft you fly.

There are lots of "owner clubs" (Cessna, Mooney, Piper etc) and this is where you will get sound information from.

Tony

[IO540]

"I'm interested in knowing what you think about the way most PPLs seem to be taught about cruise power settings"

2300rpm :O

Regarding fuel flow, nobody had much idea. One was taught to look in the tech log ; there would be a figure written down by the previous pilot, e.g. "3.5hrs" and that was your remaining fuel.

And so one went flying....

Personally, I used to always fill up, except when flying with an instructor and then I would hand him control if we ran out. Only once or twice I refused to fly and insisted on going to the pumps.

Now I fly a plane with a Shadin flowmeter, accurate to 2% and checked at every fill-up, and it's a revelation.

I don't think there is any way to know the flow rate of a particular 30 year old aircraft because the prop fitted may not be the correct type, so setting an RPM will not give a known fuel flow.

I flew a PA29-161 which would do 103kt ias, and another one which would do 95kt ias, both at 2300. That is a difference in engine power of about 15%. It is a difference in fuel flow of 15% but that's true only at peak EGT or LOP. These planes were always flown full-rich. Nobody ever found out why. It could have been just the revcounters.

The only way to do it properly is to fit a temporary flowmeter and do measurements. Has anybody done that?

Presently, I set a chosen power setting, 2300/23"/10.5GPH. This gives me a point LOP, about 65% and I leave it there. With proper navigation, there is no need to fly a specific precise airspeed.

FD is absolutely right about headwinds and tailwinds, but the relationship is complex. One wouldn't fly at max cruise into any headwind, and one wouldn't fly at Vbg into any tailwind. One could produce a graph of optimal power settings, but only if a flowmeter was available.

[Flyin'Dutch']

HWD wrote that it was untrue and unfair that I wrote:
The bare basics, if that. Most instructors have barely been outside the circuit or even know how to teach leaning
Anyway that posting has been deleted I now see, however to qualify that statement I wrote:

Statement of fact.

If you got a tenner for every one that at the completion of their PPL syllabus can lean properly and I got a pound for everyone that didn't I would be the richer man.

There are some excellent instructors around from whom we can glean an awful lot and who are pleasant in conveying the message to everyone happy to learn and soak up knowledge.

Unfortunately there are also lots of instructors who do fall in the category of just crunching the numbers, knowing barely more than me and thy guarding their 'knowledge', putting students down if they ask questions and certainly not able/willing to make PPL newbies into competent aviators.

The divide does not always follow the common quoted 'hour builder on the ladder to the airlines/old hand been at it for ages' divide either.

If you are surprised or find the above hard to believe I suggest you just stay around in aviation for a bit longer and report back in a little while. Not everyone wants to become an instructor because they enjoy teaching people.

FD

[Say again s l o w l y]

Yep, insulting and inaccurate quite a feat for one sentence.

Power settings and fuel flows, look in the POH. I always teach and use the highest expected FF.
To be totally blunt, don't muck about with exact figures, put as much fuel in as you can possibly take to stay within W&B limits and go and enjoy yourself.
However, I would generally use a couple of figures- a high speed cruise figure (since that what I usually bomb about at) and a minimum expected FF. The second would be for my own mind in case of diversion and if neccessary holding.

If you are on a long route work out how much you need using a slightly higher than book figure and then stick on certain% more.
Older, near time expired engines will usually use more fuel than the book says anyway, so give yourself a decent reserve and you won't go far wrong. 45 mins+Diversion fuel and then a final reserve of say 10-20L.(Obviously this depends on what a/c you are in. 20L in a C310 isn't a huge amount of use! Whereas a C150 it's loads.)

Having a decent totaliser does make a big difference, but keep an eye on the fuel guages and check along route how much you have compared to what you need. If it looks a little tight, land and refuel, if not carry on. This is all common-sense like most things in aviation to be honest.

The only time you can have too much fuel is when you're on fire!

[Flyin'Dutch']

Say Again Slowly,

'Fraid we are not going to see eye to eye on this one either.

1. Not sure how you can find my reporting, on what is my experience and from reading these threads umpteen others, insulting or do you really believe that every PPL student can lean when they get their ticket?

2. I can see from your example that you further the cause of acurate fuel management by your approach of:If you are on a long route work out how much you need using a slightly higher than book figure and then stick on certain% more.If you are on a long route work out how much you need using a slightly higher than book figure and then stick on certain% more.
Older, near time expired engines will usually use more fuel than the book says anyway, so give yourself a decent reserve and you won't go far wrong. 45 mins+Diversion fuel and then a final reserve of say 10-20L.(Obviously this depends on what a/c you are in. 20L in a C310 isn't a huge amount of use! Whereas a C150 it's loads.)

Having a decent totaliser does make a big difference, but keep an eye on the fuel guages and check along route how much you have compared to what you need. If it looks a little tight, land and refuel, if not carry on. This is all common-sense like most things in aviation to be honest. Can I take it from this that all your aviation calculations are done with the same accuracy?

3. The only time you can have too much fuel is when you're on fire! Or when your performance is affected by it.

I will leave it to the audience at home to decide in which category of instructor you fall but I think you have done an excellent job in demonstrating why most PPLs do not have the first clue about fuel and enginemanagement when they get their coveted licence.

FD

[TonyR]

I find it's only owners with a bit of experience really know about power settings and fuel burn. This information comes with the same pilot flying the same aircraft on different trips in different conditions.

As most instructors don't, they tend to know very little about the settings and fuel burn in the actual aircraft they fly, usually a CFI will have told them something like "this one has four hours endurance".

It's just fill up and fly and if they have extra pax it's half tanks and fly, rarely for more than an hour anyway.

Tony

[Say again s l o w l y]

"Accurate fuel management in light a/c" You're having a laugh aren't you! As accurate as a Cessna fuel guage?

Performance issues? As long as you are within limits and you have done your calculations properly (with the properly applied fudge factor of course) then where are the performance limits? How many old machines will meet the POH limits? Not a lot I reckon.

I assume that you fly the same a/c all the time. I can assure you that when you have an aging fleet of machines they are all totally different and the POH can often be totally irrelevant.

So for the 'average' PPL I advocate using some stock and sensible figures. ALWAYS take more than you think you need. That works for airlines aswell as PPL flying. I regularily put hundreds of pounds extra into a/c I fly if I have the weight to spare. I know I have the performance to take it though.

If you know the a/c well, then you can start to refine the technique and fuel management, but if the type or particular machine is unfamiliar, then take a good reserve and use a general figure.

What's the big deal about having a totally accurate figure? So you can land and say "I used EXACTLY 55.687 ltrs aren't I clever!" what a waste of time. Flying is supposed to be fun and worrying about how much fuel you have is pretty crap.

I won't rise to the bait of questioning my instructional technique as it isn't worth bothering with, but I will say that I try to be one of the toughest instructors you'll ever meet and I don't put up with shoddy planning. If it can be demonstrated that the pilot understands fully why and what they are trying to achieve when it comes to pre-flight planning, then they are o.k in my book. Purely knowing how to look up tables and do calculations blindly with no reality check built in does not impress me in the slightest, even though my planning methods may seem at first glance to be rough and ready, they are built upon experience of what I see as really important and I've not run out of fuel yet, or failed to make it off or back onto the runway in one piece.

[Flyin'Dutch']

I wholeheartedly agree that doing some sensible approximations are just fine when doing your fuel calculations but that can only be done after you have acquainted yourself with the knowledge and experience required to do it properly.

Building in fudge factors may seem a good idea but as with doing adding a few knots here and there on the approach may well land you into more trouble (as in the far hedge)

The point I am making is that this essential and basic knowledge like fuel managament is not something most PPLs students get conveyed appropriately during their training, nor that of leaning.

I won't rise to the bait of questioning my instructional technique as it isn't worth bothering withThat is fine of course but it was you and HWD (who seems to have disappeared in the wide blue yonder) that wrote that my statement about lack of experience amongst instructors was inaccurate and insulting.

So far we have not had hords of folks coming out of the woodwork claiming that they were up to speed on these matters which are arguably essential and can not take more than 30mins of instructional time and should be integrated in the entire flying syllabus.
I will say that I try to be one of the toughest instructors you'll ever meet
Good luck to you and your pupils.

In my books 'toughest' does not equate to 'best'

FD

PS: You wrote:I assume that you fly the same a/c all the time Which amply demonstrates that assumptions can be dangerous, not just in fuel planning!

;)

[S-Works]

Steady on with the Cessna abuse! :p

My Cessna has bang on accurate fuel guages that are verified by a very funky FS450 fuel computer.

I know exactly what my plane uses at any flight condition and plan accordingly.

But the fact is that most instructors that I have come accross know squat all about fuel consumption and planning let alone leaning. It is true that they jump in fly the required lesson and jump out, nothing is ever taught about leaning and consumption other than some arbitary figure bandied around the school.

My aircraft uses 33lph at full tilt in the climb, 23lph at 105kts and leaned back which I do once staright and level above 1500ft it does 19lph. The change of prop from mcauley to sensenich was the most enlightening thing to happen to me in a ong time!

I was not taught this by an instructor despite flying one of the most common trainer aircraft on the planet, but by several hundred hours of watching the guages and dipping the tanks.

[Say again s l o w l y]

For toughest don't read ogre, it's more to with the standards I expect. I always expect them of myself so I would like a similar attitude in my students.

There are times and places for 'fudge' factors, approach speeds are not one of them. Too much speed is a bad thing, a bit too much fuel is a good thing.

Having a clear and full understanding of any subject is essential before you can start to take a few liberties. I'm all for having SOP's, but blind adherence to the rules with no thought as to why we do what we do is in my opinion lethal. SOP's cannot cover every eventuality.

For instance if you have worked out a wonderfully accurate fuel plan, but fail to check how it's going en-route, then the plan is useless if you don't notice an abnormal fuel flow and end up in a PFL.

There is NO excuse for ever running out of fuel.

Trying to plan fuel usage for a lesson is a total waste of time since fuel flows and power settings will often be changing constantly, will a navex use the same amount of fuel as a session of ccts or stalling? No way, this is why we'll usually use 1/4 a tank per lesson usage, filling up whenever it goes below 1/2. Leaving the final 1/4 as a reserve. Is this accurate? No, is it safe, Yes and there is no room for confusion. That to me is the most important thing.

[Flyin'Dutch']

That is all a lot more qualified than what you wrote before, and I can only agree with all of that, even the bit what you say about being tough!

The issue I raised was that you need the knowledge before you can master these matters and it is my firm belief that there is no or indeed too little attention for this during the PPL training.

Yup the licence is one to learn but who can stick up their hands and say that anything was done with the fuel calculations for the XC work they did during their training?

And even less will have been told anything about leaning.

That is not out of malice but just because the entire syllabus and training set up is not geared towards training people to do that for which they think they are going to use their PPL, touring.

Encapsulating these issues would not be difficult but does not happen. Why? I think because a lot of PPL instructors don't lean either or work out fuel calculations for XCs. What they don't know or don't think to be important they don't pass on. Contrary to popular belief most instructors are just humans.

;)

FD

[Say again s l o w l y]

Unfortunately due to the time pressures that get put onto instructors, far too many things get missed out during training. In reality we should do no more than 4 hrs a day flying, with plenty of space built in for proper briefing and de-briefing. This won't happen since FI's are paid by the flight hour so need to cram in as much airborne time as possible.

The only way to fix this is to charge more and have longer lessons or have unpaid non-pro FI's. Only the first suggestion is workable in my opinion.

I only do 3-4 students a day maximum, but I'm paid by an airline, so instructing is now a bit of fun for me rather than my only income. Takes the pressure off considerably and allows me to do the job properly and I will admit to not teaching as thoroughly as I would have liked on occasion because of the time pressure.

That is why things get missed in training, not down to the lack of knowledge of FI's.

The system does need an overhaul and only continued pressure from the PPL and instructor community will help it change.

Whilst touring is what many PPL's do, the vast majority turn up, fly around in circles for an hour, land and go home. Rarely do they go touring any great distance so a comprehensive fuel plan is pretty much a waste of time for them, but since the people who use their a/c as they were designed are invariably far more competant in my eyes, then it's not unreasonable to expect them to be able to complete a decent fuel plan.

[Flyin'Dutch']

I agree with you (this is getting boring now!) about the pressures there are on time etc and that some PPL studes do not further their own case by arriving unprepared so they are not ready to take in what is on offer.

However how much effort and time does it cost to pull out the mixture knob during the cruising along during the NavEx and teaching studes on how that bit is done?

Or how about filling up after you get back from your XCs and showing the discrepancy (if any ;) ) between calculations and real burn?

Whilst touring is what many PPL's would like to do The red bold bits are mine.

Ask what a lot of PPL wanabees want to do with their ticket. I think they broadly fall into 2 categories.

1. Those who want it to be their stepping stone to CPL/ATPL etc
2. Those that want to go for lunches to nice places/abroad.

The current system does not prepare people for the latter category. THat is why they your assessment of what happens is true:, the vast majority turn up, fly around in circles for an hour, land and go home. Rarely do they go touring any great distance.
Usually for a year or two, then get bored and hang their headsets and licence up to get dusty and stop flying.

Big shame, can be changed but would need a concerted effort from all in aviation, but that is another soapbox.

FD

[shortstripper]

Well there may be one one or two good excuses actually ... but then most of us are not faultless Sky Gods ;)

SS

[Flyin'Dutch']

For what?

Running out of fuel?

I doubt if there is any good reason for that. Running out of fuel that is in the understanding that there are no leaks etc.

FD

[Say again s l o w l y]

Personally I do both, but I know many others who don't.

I remember reading somewhere that the 'average' PPL will only do 50 hrs post licence issue before giving up. If that's true it's a travesty, but unfortunately understandable given the dire service most people can expect after they get their licences from most so-called flying 'clubs.'

Why don't we set up a Pprune club that offered training and help to people who have recently got their tickets aswell as organising fly-ins/outs etc. I know it is done on an informal basis already, but why not formalise into a non-profitmaking organisation. I for one would be very willing to put some time in and I'm sure their would be plenty of others (FI's and PPL's) who would also be willing to get involved. Just look at the number of people who offer help and advice free of charge here on Pprune already.
It could be a sort of one stop shop that provides everything that most clubs don't do very well.

[Flyin'Dutch']

Hear hear.

Something akin to this is running in a form of sorts here (http://forums.flyer.co.uk/viewforum.php?f=10&sid=2f890fe5c38e0fb1ea005c493ed9e19a)

Think that offering to fly with people/together would be part of the solution as you suggest.

FD

[IO540]

FD

Ask what a lot of PPL wanabees want to do with their ticket. I think they broadly fall into 2 categories.

There is a 3rd category: those that do it as a personal challenge, and perhaps a 4th one: those that are given £6k or so for xmas to do a PPL and they do it for a laugh.

Few out of the last two will end up flying in the long term.

From what I have seen, at my airfield where there is a number of schools, the 3rd category makes up about 75% of PPL students.

[Capt. Manuvar]

Good of you to bring up the idea of leaning. I don't think that instructors in the UK don't teach it becase of lack of time. Instructors in other countries aren't better paid but still teach leaning. There is a myth going around the UK ppl training world : PPL+leaning=cracked cylinders.
I totally disagree with those who don't bother using the POH due to inaccurate guages/old engines. It is totally irresponsible for any pilot to take off without knowing how much fuel there is. There is the lazy method of filling the tanks but not everyone has that option as any "four seat" aircarft pilot will tell you. Nowadays ther are £10 dip-thingies that you can use to check how much fuel you have, i wonder why all aircraft owners/clubs dont have one of those in the glove compartment, even 737s have them.
As for fuel burn, why not calculate the POH figure and then add 10% for pilot error and 10% for the cr@p engine. I agree that when it comes to local training sorties or jollies, calculating accurate fuel flow is pointless, but it would be a good idea to know what the max fuel consumpton is and to kno the you will be able to divert should the need arise. The problem i have is with people flying a particular airspeed or rpm regardless of OAT or altitude. 2400rpm or 110KIAS could be 60%/6gph in the winter or 90%/12gph on a hot day. Luckily a lot of crosscountries during training rarely exceed 2hrs, so we can get away with "fill the tanks". But when PPLs decide to 'spread their wings' or 'expand their horizons' then there is the potential for trouble, especially since most GA magazines are on a crusade to hae us flying as far as possible into the continent.

Capt. M (who doesn't know how to lean)

[High Wing Drifter]

In my honest opinion the notion that PPLs don't know how to lean and that instructors don't teach it, is one confined to internet forums.

[IO540]

CM

The problem, as someone finds out when they have a high perf plane with a flowmeter and they start leaning for LOP operation, is that the difference between

a) leaning until the engine goes rough and then going rich a bit, then applying carb heat and if the rpm drops you haven't leaned too much :O (this is the method normally taught in spamcans), and

b) leaning for peak-EGT or LOP operation, likely to work only on an engine which just happens to have a reasonably well balanced air/fuel flow, and perhaps more likely to work with a pilot who is used to cr@p planes and doesn't notice excessive vibration

is perhaps 20-30% on fuel flow.

With the sort of weight/range tradeoffs one is making on the average PA28 with three average adults in it (never mind four; most of those cases are overweight no matter what), a 20-30% error on the fuel flow is all it can take to run out.

I am not offering a solution; just pointing out that attempting to lean and assuming that the fuel flow will be X GPH, is no more accurate than flying full rich at a specific RPM and assuming the fuel flow will be Y GPH. In fact the latter is likely to be more accurate - assuming that somebody has actually gone up for a flight and measured it. A POH is the official reference but a POH for some 30 year old plane isn't likely to be accurate enough for this very safety critical department.

Somebody owning such a plane could establish the actual flow rates but I don't think it is ever done in the training environment.

HWD

I am sure PP posters are not a representative sample of the PPL population but I can assure you that leaning wasn't taught to me as a standard procedure. I was shown once.

[tyro]

I learned leaning last month. Before that, I was under the misapprehension, having never asked, that leaning was something that only happened during high altitude cruises.

I had planned a 340nm round trip in a Warrior to a private strip with no fuel. Having never flown so far before, I was getting a bit twitchy about the fuel planning. So I met my former instructor for a drink to discuss it. It was a surprise when he suggested that, even at 2000', leaning would be worthwhile and might save 1 or 2 GPH.

For good measure, he also commented that fuel gauges in a Warrior aren't quite as bad their reputation and I would know if and when it was time to land and refuel.

So I went with brimming tanks, leaned and arrived back 3.5 log hours later with apparently in excess of 7USG in each wing. I still have no real idea what actual difference fiddling with the red knob made.

[Flyin'Dutch']

HWD,

I notice from your location that you are heading up Norf. Are we talking about the same planet though.

When you write:In my honest opinion the notion that PPLs don't know how to lean and that instructors don't teach it, is one confined to internet forums.
You have to be kidding!

That this may seem to you to be only a subject raised here on the internet has probably more to do with the fact that people do talk about their uncertainties/questions in the comfort of a bit of anonimity rather than in full gaze at the 'Hangar Talk Inn'

If you were taught all about fuel management and leaning during your PPL syllabus and were made comfortable with that, great and credit to your instructor/training outfit.

A lot of people are under the misapprehension that what happens to them is what happens to everyone else (not just in aviation) and you only have to look at the threads which come up time and time again on these two essentials issues to realise that they are not well taught.

FD

[GroundBound]

During my training I was never shown a POH (I did however spend some time looking through one in a non-flying aircraft). I was given a photocopy with the target approach speeds and checks.

I have flown in the last couple of years in two clubs, and a POH was never available, even on request. One has been taken over, and they now have a photocopy of the POH which can be bought, "if you really want to".

During my training I was told lean above 3000ft ("pull the red knob back a bit").

My knowledge of leaning comes only from reading Thom (lean until loss of power then advance a bit), or the rants and raves on Pelican's Perch.

Some while ago I made a cross border trip and decided to go to FL60 in cruise (PA28/181) (lovely weather and some rising ground). I leaned until the EGT needle reached the red line. I left it on standard cruise power 2300RPM. The IAS fell back to 95kts.

I have no idea what 65%, 75% power means. I have no idea how to interpret the power graphs. I filled up before departure and before returning (2 hour flight, 4.5 hours of fuel approx.)

I don't know what I did wrong. I don't know what I did right.

Do I have any idea about engine management? Doesn't look like it!

Am I typical? Wouldn't surprise me, at all.

Do the people who rent me their planes care? I don't think so.

GB

[BigEndBob]

Leaning would also probably reduce the risk of carb. icing.
Less fuel evaporating in throat of carb. and hotter exhaust for carb heat.


And cleaner plugs.

At FL60 probably only see 2300rpm at full throttle 95kt ias but 105 tas typical.

Dont mix up throttle posn with actual power output.

[BEagle]

Flew with a chap once who suddenly yanked the mixture lever back at 1000ft. Predictably, the engine started running rather roughly. After about half a minute I aked him whather this was his normal way of operation...."Yes, always lean it off. Saves the club fuel" was his answer! "Well, please richen it again and save the club money on replacing burnt pistons and pots!" quoth I.

We've had a few cooked engines due to over-leaning over the years. I'd sooner waste money on burning a little too much gas at 85p per litre than have to fork out hundreds of pounds for engine repairs YET AGAIN!

Leaning off is really only safe if you've got the appropriate EGT and CHT gauges to assess how hot the engine is getting.

[Capt. Manuvar]

A quick question regarding the use of POH graphs:
The graphs I deal with have density altitude calculations based on Pressure Alt and Temp. Does pressure altitude mean Pressure altitude on 1013 or on QNH? (don't be too hard on me, I'm just another product of the system:ok: )
Beagle
I agree that there will be a tiny minority who will abuse the controls, but if instructors teach it properly in the first place it shouldn't be a problem. It's normal practice in other countries.

[tyro]

Beagle,

I can imagine that CHT and EGT meters would make leaning an exact science. However in club planes with neither, how good an approximation is the "lean until it starts to run rough and back off" method? If it's done right will it significantly alter fuel consumption or the life of the pistons and "pots"?

BTW: Is a pot the cylinder or its head or something else?

[Final 3 Greens]

BEagle

Is this the "lean it until you can't read the shaking dashboard and then enrich it a bit" method? ;)

Seriously, how do you think our Yank cousins manage out of 7000ft airfields in basic kit? Without leaning, the engine won't develop rated power and without that power it won't make the grade at 8-10,000ft density altitudes.

I agree that 1,000 ft is a bit aggressive for a PA28, but is there really a prob leaning by instantly enriching at the very first tremor of rough running?

[High Wing Drifter]

FD,
I notice from your location that you are heading up Norf. Are we talking about the same planet though.
Now, now. Be nice!

A lot of people are under the misapprehension that what happens to them is what happens to everyone else...
Oh really! Well I never.

[Dale Harris]

OK, just so I have this straight....... You guys pay 85p ($2.20 oz) per litre........ And you don't get taught to lean the mixture?? Are you fair dinkum? Even in the biggest POS I've ever flown in, the fuel burn I've got has always been within 2 or 3 % of the figures shown in the POH, more usually 1% in the aircraft i currently fly. What is with this "Can't trust the book thing"? Our aircraft are as old, if not older than yours, and as far as engine life goes, pretty much any warrior, 150/2, 172 et al, makes tbo. I just don't understand what is really going on here. Never trust fuel gauges, sure, that is what dipsticks are for, or visual checks. Gauges are a backup to fuel in/out. I really find it hard to believe that PPL's haven't been taught to lean an engine properly. Engine management is just as important as any other skill associated with aviation.

[IO540]

The explanation for the poor training is, I think, that here in the UK only a very small % of PPL students are doing it to go places.

Just hang around some airfield for a year, and look around. Most are doing it as a one-off challenge, or to impress the mates down the pub, or to pull birds (a complete waste of time for that), or because they got some money for Xmas to do a PPL. Some 90% don't bother to renew their PPL after 2 years.

Some are doing it to gain an ATPL but for most of those that seems to be a long haul too. A lot of people spend say 5 years as PPL instructors, on peanut pay, before they can get a job.

Also, most people that are attracted to PPL training don't have enough money to fly afterwards, or even at the time in many cases. There are plenty of people about with money; they just spend it elsewhere, presumably buying into some activity with a more exciting social scene.

If more people did it for some long term purpose, and more of them had more money, then there would be the demand for better training, better instructors, and untimately the aircraft available for self fly hire would improve in quality and condition.

In the end, we get what we deserve.

However I think there may be a particular problem with N European weather. The basic PPL really isn't very useful for going somewhere; instrument flight capability is more or less essential (even if, on the day, the weather is actually VMC). But nobody is willing to admit it, and if you turn up to do a PPL here, you won't be told that on any given year you will end up cancelling most of your planned flights. Also in flying clubs there are a lot of retired men, with plenty of time on their hands, who say "you can go everywhere VFR".

It is going to be very different in Australia.

This is all off-topic I know but unless one asks basic questions, the debate about what is unavoidably training standards can go on for ever.

[Gertrude the Wombat]

You guys pay 85p ($2.20 oz) per litre........ Er, no, not all of us. Very many of us rent wet, and pay by the hour. Unless all hirers aren't leaning to start with and then start leaning the operator won't see enough of a drop in fuel burn to lower the hourly rate.

[englishal]

I can hand on heart say that I do the fuel calculations for every single flight test :} (about 5 or so).

I learned to fly in California, where it is hot, and you get up high often, so you had to lean properly. The instructors were good, and taught leaning from the word go.

Often you have to lean in the climb, which is not a big deal, even though many people will no doubt scoff.

EA

[IO540]

It is fine to lean in the climb provided the airfield altitude is such that the engine never develops the power above which one isn't allowed to lean.

For example the IO-540-C4D5D is allowed to run at peak EGT (the hottest condition!) at any power of 75% of max HP (75% of 250HP). I don't know off hand how to work this out (the Lyco engine manual doesn't have a graph of HP versus density altitude; one would have to estimate the MP from the DA and look up the HP for a given MP) but 75% is probably reached at about 5000ft elevation (ISA). So, when departing from 5000ft or higher, one would lean for peak EGT on the runway.

But below that elevation, one would use full-rich because that's what the engine manual says.

It is unlikely that one would be authorised to lean at sea level, at full throttle. I suppose some engines may allow it. But it takes one into the detonation area.

OTOH there is no law against taking off at cruise power, 75% or less, from sea level, and leaning for peak EGT then. Just needs a lot more runway, and most would regard it as a stupid thing to do.

[dirkdj]

Sorry IO540 but I can't let this pass..

Quote: For example the IO-540-C4D5D is allowed to run at peak EGT (the hottest condition!) at any power of 75% of max HP (75% of 250HP).

There is truth in that statement but "(the hottest condition!)" should be left out completely.

The hottest place to run an engine (as seen on the EGT) is at 40-50 ROP, where the highest CHT will be found. The EGT reading is just a navigation landmark on the power curve and the EGT temperatures bear no relationship to the real temperatures of the exhaust valves.

Best power mixture is at the 80°F ROP EGT point, but at high power (take-off) more fuel is needed to make the mixture richer in order to give a wider detonation margin.

Given good instrumentation an engine can be run full thottle, at sea level , but very lean at about 80°F LOP EGT. This is in fact the FAA approved way to run the TATurbo.

Running it ROP at this power level would be asking for trouble.

Take-off should be done at maximum power, full rich with sufficient margin for detonation, leaning is necessary in high altitude or high temp situations in non-turbo engines only.

There is no better detonation protection than to be well lean of peak at high power, temperatures are well down, because the bulk of the combustion event occurs later in the downgoing power cycle: less compressed ergo lower temperatures.

Of course if a given engine will run smoothly lean of peak depends on several factors, mainly how well the horsepower of the 4 or 6 individual cylinders is matched. If some are still ROP while others are LOP then a power mismatch will give a rough running engine.

I have flown a Mooney 231 that was so well balanced it could be leaned until the engine died from lack of fuel without any roughness.

Dirk

[IO540]

Peak EGT is the highest EGT, by definition. That is also the stochiometric point, where all fuel is being burnt with just the right amount of air. This isn't the max power point, which as you say occurs slightly rich of peak. But it is a lot more economical point.

I think the #1 problem is that any specific statements should be limited to specific engines.

Lyco certainly don't allow leaning above 75% power for the one I referred to. Whether leaning to LOP at full throttle does any actualy damage is another matter. Most likely not, but of course if you are at full throttle at sea level and then lean it LOP, you won't be developing the rated HP anyway; that happens at the setting on the fuel metering unit where all 3 levers are fully forward which on the engine in question is about 125F ROP.

The rest of what you say I agree with; one needs balanced injectors (probably GAMI), decent multi-cylinder instrumentation, and knowledge. This makes it irrelevant to probably 99% of UK GA operations.

If PPL training included advanced engine management, the "45 hrs" would have to be 60-70hrs, a lot of people who manage to get through the exams would never understand it, and the planes don't have the instruments... so we have what we have. In the typical spamcan flown at 2000ft, it doesn't matter.

[High Wing Drifter]

Those interested in this thread maybe interested in this link from Lycoming: http://www.lycoming.textron.com/main.jsp?bodyPage=support/engineOperationTips/index.html

[dirkdj]

High wing drifter,

After reading the Lycoming text, be sure to follow on with: this (http://www.avweb.com/news/columns/182131-1.html)

IO540,

You are right that peak EGT is the hottest EGT.

But: EGT is a bogus number, it is not the temperature of the combustion gases inside the cylinder (they are well over 4000°F), it is also not the temperature of the exhaust valves. EGT is strictly a reference point to manage the leaning operation. There is no limit on EGT, in fact moving the probe a few millimeters in or out of the centre of the exhaust may have a dramatic effect on the reading.

The basic combustion cycle is really the same for all spark-ignition piston engines, some engines are more stressed than others and may need more care.

In my opinion the PPL is just a license to learn, engine management, GPS etc are barely or not covered.

Dirk