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

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 with

That 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!

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

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.