Flying over square [Archive]

knox

26th Sep 2011, 20:30

Thanks for all the great replies.

I was always taught that if all the gauges (MP & RPM) were in the green you couldn't really go wrong.
I remember once doing bumps and goes with a very experienced testing officer and having the RPM set at 2200 rpm (in a C206) and just using the throttle in the normal way but never exceeding the green arch of the MP. The aircraft preformed well and with no noticeable issues.

I have been told that if you run, for example 25/2300 you can get a few kts extra out of the cruise speed.

And one last thought, a lot of flight schools seem to promote going through to full fine on final approach often with no regard to the prop/engine and in the process creating a gut wrenching scream (for lack of a more descriptive word) from the prop/engine. Is this just poor engine management, as I can always seem to get the aircraft on the ground without doing this.

Knox.

AerobaticArcher

26th Sep 2011, 20:38

I've always found aircraft to fly a little faster running a higher RPM than MP (say 23/25).

As for valves, they will go sometimes regardless of how you operate the engine, it all depends on who and how they were seated during engine build/overhaul.

Correct me if I'm wrong, but Deakin and crew suggest that with a higher RPM, the engine will run cooler as there is more air being drawn through and the heat is taken away from the cylinder heads quicker... that will make the engine last longer.

an3_bolt

26th Sep 2011, 21:01

Refer here:
http://www.lycoming.textron.com/support/tips-advice/key-reprints/pdfs/Key%20Operations.pdf
Pages 43-44 and 65
Don't forget to refer to the POH for any power setting restrictions.

A brief bit on CHT page 51-52.

Off the thread a little - One other useful section is 54-56 regarding sticking valves. One such event was a slightly sticking valve at start up that was actually caused by one of the 2 springs broken. At some stage would have ended in tears if left unattended.

A link to the some other Lycoming stuff:
Key Reprints - Lycoming (http://www.lycoming.textron.com/support/tips-advice/key-reprints/index.html)

Desert185

26th Sep 2011, 23:27

Continental IO-520 with GAMIjectors. WOTLOPSOP for me. 1100+ hours, and going strong. Never had the TCM factory cylinders off since new.

Horatio Leafblower

27th Sep 2011, 00:38

Millenium pots, however, a different story :rolleyes:

Jabawocky

27th Sep 2011, 02:20

And one last thought, a lot of flight schools seem to promote going through to full fine on final approach often with no regard to the prop/engine and in the process creating a gut wrenching scream (for lack of a more descriptive word) from the prop/engine. Is this just poor engine management, as I can always seem to get the aircraft on the ground without doing this.

Knox,

Just some hints on what to do with all those complicated knobs. Generally speaking from TOD to parking it outside the hangar, use only the throttle to reduce power either on descent (keep speed under control) and in the circuit. No need to touch the mixture or RPM. Some days you may need a small and I mean small amount of richer fuel air ratio if it gets a bit rough on descent. But only just a small tweak ya hear! ;)

So on finals, boost pump should be on (unless otherwise noted), gear down as required and whatever else you have already checked on downwind.

In the unlikely but possible event of going round, remember you are already flying so there is no need for anything rash here, it is simply red knob, blue knob, and black knob.

As for other items, over square, what do you think happens on takeoff? That is over square. And some engines like those big round supercharged things have limits, but basically the bulk of Lyc's and TCM's are simple operations.

In simple form a flight should go something like this;

1. Start up, and lean until the RPM peaks and just starts to drop.
2. Taxi out and do your runups at say 1700RPM and only richen up enough to get 1700 smooth, do not over do it, watch RPM and EGT's (of course you have an all cylinder monitor) and on each mag, all EGT's should rise together. If any fall there is a plug mag or wire problem.
3. Line up, switch boost pump on, mixture rich....GO!!!!
4. passing through 500-700 feet take note of the EGT on any one cylinder (or the EGT on single probe) and remember it, this is now your TARGET EGT.
5. Depart the circuit and climb, do nothing unless for noise abatement.
6. Passing say 3000' lean back to get your target EGT on whatever cylinder you picked, probably cyl 1, and near enough is good enough. This will keep your fuel air ratio about the same as it was when you were full rich at sea level. Keep climbing.
7. Passing 5000' or there abouts chase that target EGT again, and again at 7000'.
8. Level off at your desired altitude, set the RPM where its smooth and comfy, (better with a dynamically balanced prop) say 2200-2500, and then lean to a setting appropriate to power setting, but lets say around 70-65% that is just LOP to 25LOP .......if you need injectors tuned, do it, in most carby engines you can get this if you try hard enough. If its carby and fixed pitch.....better come see me as its too hard to describe here! :bored:
9. enjoy the cruise and low fuel burn, cleaner pistons, plugs valves etc and MUCH LOWER CHTS!
10. TOD, nose over and reduce throttle setting to keep speed under control, if I am doing a 700'/min ROD I usually pull back to the MP I had in the cruise, and the speeds stay just in the green.
11. Join circuit and land with just throttle movement, shut down as per normal. Going full rich just carbons everything up, so don't do it.

I am sure most here know what this is all about but if there are a number of folk who would like to see this done, and like to learn about the science of it, and can get to SEQ, call me. It can be fun and educational.:ok:

J:ok:

PS Chimbu Chuckles will no doubt correct any errors or omissions above :)

NIK320

27th Sep 2011, 03:51

I was always taught to land full rich, full fine pitch, never really liked the sound of fine pitch stops on final.

I've just dug a 182 POH out of the bookcase to compare and it does have pitch full fine for takeoff, landing only says fine and balked landing specifies 2400rpm. From that I guess an interpretation could be made that Mr Cessna is telling us to do it your way with a overall fine setting and not shove the prop control as far forward as you can.

I think I'm inclined to change methods :)

mattyj

27th Sep 2011, 04:26

If you have a big enough hand..just push up all 3 at once on go around! At a sensible rate mind..don't want to shock an old donk

gassed budgie

27th Sep 2011, 04:38

I was always taught to land full rich, full fine pitch, never really liked the sound of fine pitch stops on final

If I'm in the 210, I don't touch anything from TOD (regardless of how high that might be) until I shut it down, other than the MP to keep the IAS in the green on descent.
The 172 however, might need a tweak of the mixture on the way down to stop any rough running and keep things smooth, if it's been operated at full throttle up high.
As far as running things oversquare are concerned, that won't be responsible for the junking of cylinders/engines. For a given power setting, you'll generally find the cylinder head and oil temperatures to be slightly less than what they would be running the engine at a higher RPM.
Anytime you fly a T210, Chieftan etc., it's almost always being operated oversquare as a matter of course and it doesn't hurt those engines.
Oversquare in a NA engine? Once you climb above around 4000/5000', it won't be the case anyway.

rioncentu

27th Sep 2011, 05:23

I'll concur with GB. Same in my 210.

WOT for climb and leave it there, just pulling it back on descent to avoid the yellow.

I too don't richen for descent.

Sure go full fine on very short final if you want as by then the prop is out of governing range and won't make any noise to scare the locals !!

T28D

27th Sep 2011, 10:29

Obviously no round engine pilots here, Wright 1820-86 take off 2700 rpm 52.5 inches climb 2400/36 inches economical cruise 2000/30 inches approach 1800/20 inches go round 2400/36 inches

Pratt Wasp Junior take off 36/2300 climb 31/2100 cruise 29/1850 approach 20/1850 go around 31/2100.

Oversquare ?????

Jabawocky

27th Sep 2011, 10:55

T28D

I know you will be pleased if not alarmed to hear me say 100% agree :ok:

The fuel does not know the difference. It just combusts all the same given the same circumstances, be it round or not!

J:)

MakeItHappenCaptain

27th Sep 2011, 13:37

Lasiorhinus

27th Sep 2011, 13:53

If you've got the power back far enough, which you should on short final, the propeller will already be up on the fine pitch stops, and therefore no movement of the RPM control towards high rpm, be it a slow gentle movement or a ham-fisted shove, will actually change the blade angle or RPM at all.

If you've got the power up so high that you're still in the governing range, then you're too fast on final.

Easy test to see if the propellor is on the fine pitch stops - is it still on the same RPM you set in cruise? If its any less at all, then you've got yourself a propeller on the fine pitch stops already. No change in noise, no change in descent rate, no change in drag from here.

multime

27th Sep 2011, 14:02

T28D
Thats indeed what i was trying to say.
I was cut short embarrasingly so without explanation.
Thanks

Chimbu chuckles

27th Sep 2011, 15:02

I remember once doing bumps and goes with a very experienced testing officer and having the RPM set at 2200 rpm (in a C206) and just using the throttle in the normal way but never exceeding the green arch of the MP. The aircraft preformed well and with no noticeable issues.

That is actually bad for the engine. Sure you won't notice anything immediately - and you may have only done slight damage to the engine's longevity on that occasion, but its still not smart. It doesn't surprise me at all that the 'very experienced' testing officer didn't know any better.

The single kindest thing you can do to a piston engine is use FULL rated power on every takeoff.

multime what is the essential difference between a Lyc and a Conti, radial or turbo?

I suggest to you there is no real difference in how they function or their metallurgy.

Sure, some have METO limits but MANY don't.

Treating those that don't like they do is actually bad for them.

A lot of people talk about MP and RPM as if they are the be all and end all - not true. Mixture is enormously important - and usually the least well understood.

I have spent LOTS of hours in my Bonanza tooling around with the IO550b at 27 or 28 inches MP, RPM at 2200 and mixture 30F LOP EGT. The engine loves it - it runs cool and clean with low CHTs and internal cylinder pressures. You could happily operate the engine that way for 1000s of hours.

IF I was so stupid as to move the mixture to 30F ROP EGT, and change nothing else, I would likely ruin the engine in no time flat. At the very least I would cook the cylinders in a few hundred hrs - worst case I could set off detonation and have the engine fail catastrophically in minutes.

And all I touched was the red knob.

FGD135

27th Sep 2011, 15:48

Pitch max will also provide a very useful source of drag ...

Ahem.

Is it producing that drag at the same time as it is producing thrust?

Was it the act of "increasing pitch" that caused it to start producing drag?

On takeoff, the blades will initially be on the fine pitch stops, but will move off the stops as the airspeed starts to build. Is the prop producing drag during these stages? Or is it producing thrust?

Horatio Leafblower

27th Sep 2011, 21:26

Is it producing that drag at the same time as it is producing thrust?

The wing produces lift + drag simultaneously, does it not?

Was it the act of "increasing pitch" that caused it to start producing drag?

Why do twins have feathering propellers? :confused:

Slightly off topic but I am led to believe that having the airflow drive-on the engines is very, very bad for GTSIO engines.

Jabawocky

27th Sep 2011, 22:39

It does seem that some people here are advocating landing with the prop at the descent setting (correct me if I'm wrong).

If you don't slam the pitch into full fine while carrying Vref + say 30kts, you won't get the prop bouncing off the redline while it attempts to govern your hamfisted commands.

Pitch max will also provide a very useful source of drag to provide that last bit of deceleration over the fence and give you the best climb ability in the event of a go-around.

During a go-around, why wouldn't you maximise your RoC by using T/O power? Height is your friend. Get it ASAP! Once a a safe height, then use the max cont. pwr settings (which most likely are your baulked landing figures....coincidence?)http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/thumbs.gif

MakitHappenCaptain

I am really not sure you understand what you are trying to say here. Why not land with the pitch control still set from the cruise. say 2300 RPM. Why not, in the event of a baulked landing, RED/BLUE/BLACK, in about the time you read that, or if you can do all at the same time, who cares. It will not make any difference. Now you are climbing away at full bore max rate.

In the likely event that you land, and I am sure you do mostly, taxi away leaned out, and not clogging up everything.

If you really do need all that extra drag from pitch, well use it, but next time plan your approach better ;). As pointed out already once the power is off the prop will be fine anyway so if you really want to move the lever up. There is no reason not to. But just the same there is no valid reason to.

Just as Chuckles is not surprised about testing officers, I am not surprised but still alarmed at how many CPL's are being churned out with all these OWT's well drilled into them. Hey Pyro ;)

AdamFrisch

27th Sep 2011, 23:14

I don't touch the props on landing. Sometimes on shorter strips I might just ease them forward a bit, but that's about it.

I run my geared engines (which is a different kettle of fish admittedly) at 20" and 2500rpm all day. I'll reduce the manifold as I descend to keep the 20" going as I get lower, and then go to even lower settings for the circuit as needed.

SpyderPig

28th Sep 2011, 02:33

I am not surprised but still alarmed at how many CPL's are being churned out with all these OWT's well drilled into them.

Then why are they (OWTs) so drilled into the instructors and then the student in the first place if its such a bad practice? If there is a better way or better technique why are they still teaching this? It makes no sense. Im sorry but I like to do things the most efficient way and just fail to see why if there is so much information saying its bad for the engine etc why they are still teaching fresh CPLs(myself) this?:confused:

Jabawocky

28th Sep 2011, 02:54

Spyderpig

I have no idea why....because when we are taught and I was a victim of this, we trust almost implicitly everything this font of all knowlege is teaching us.

My driving instructor when I was 17 was a good example, however the race training showed me much better skills.

So why do things get passed through generations, because it seems to be human nature. I believed a lot of this stuff until I saw the light, thought about it with an engineering type mindset, and then went and played in the air, and low and behold I saw with my own eyes :sad: I had been misled for so long.

Now I am like one of those born again evangalistic LOP'ers :}.

The truth shall set you free!

I think one of the other reasons is most instructors now and 30 years ago had no idea on the science, did not have a clue about how to work it out for themselves and back then communications was not like today where information is a blink away no matter where you are.

The old raial piston airliner guys knew and operated differently to what most kids are being taught today, and some of the Rules of Thumb from back then were applied to modern flat 4/6's without only part of the rule applied. The oversquare one is a classic example.

Now if young Pyro were brave enough to pop up here he would tell you the day he convincingly told me why you should fly a C172 RG a certain way. I challenged him on why he thought that. The answer was ...well politely put...Bull****, and I hope when a scientific explanation was put forward it sunk in and he did not revert to old habbits. He understood the common sense at the time, the theory I told him actually worked in the air, and the aircraft performed better ran cooler etc etc..........but I have to wonder have OWT's krept back into his SOP?

Maybe another session or two is required to cure the brainwashing. I call it brain flushing.

Why did the pwople back hundreds of years ago fear and believe the world was flat despite some sailors thinking and proving otherwise? GA training is no different.

J:ok:

Jabawocky

28th Sep 2011, 02:59

BUT - if I rocked up to my flying school and started using my own techniques, i'd probably be branded an idiot that is abusing the aircraft...

I even once had an instructor yell at me that I was "overboosting" a naturally aspirated engine because I was running at 24" MP and 2300rpm... Obviously this is a crock of bull****, but with me as a PPL and the bloke yelling at me was a grade 2 instructor, what the hell would I know!?!?!?!

If you knew better, the thing to do was find a time where you could challenge his thinking in a non confrontational way. Best is to ask a series of questions, lead them on a path to discovery for themselves. This is often the best way. I have done this with a few folk now, I am starting to think I should open up a school, trouble is most pilots owners and operators are too miserable to part with sufficient coin to make it worth my while.

Anyway the best question is .....Why would you say that? Followed up with really, now have you considered the science behind...........etc. Unfortunately some ego's will need a little massaging and you cant call them a turkey to their face, all you can do is educate them with more advanced technology....one day they will realise they were sold a pup once too! I know I was.

Aerozepplin

28th Sep 2011, 03:22

The training environment is in my experience fairly insulated from the outside world. Most people at the top have done little else, and most junior instructors (myself included) have learnt everything from those at the top.

I too was told off for "over boosting" at 24.5/2400rpm. I bet if I'd been at the 24.8/2100rpm the power chart for that aircraft recomended for 65% power at that altitude they would have had a heart attack. Of course, at that point in time I flew as per the flying schools SOPs: 25/2500 for climb, 24/2400 for cruise, 1" reduction per min (shock cooling BS), full rich at TOD. What a load of rubbish.

Interstingly, from my understanding the radial advice was to never run UNDER "squared" in the misguided attempt to avoid the prop driving the engine. John Deakin has a good article on this, and how it possibly lead to the loss of a CAF Heinkel 111.

Anyway, quite simply many/most pilots are ignorant of the fact they are ignorant. Flight instructors being amongst the worst, and the most dangerous. If a PPL doesn't know how to run their aircraft, they're the only ones being put in danger. If a instructor doesn't, they're passing that on to so many others.

I've shown the graph of EGT/CHT/ICP/HP to people and it blows their minds. The idea that it is high CHT/ICP that causes detonation not "over-boosting" or "over-leaning" takes a long time to be believed.

I think its criminal that it isn't more widely known. This ignorance has killed people, and will continue to kill people.

*prays at the alter of Deakin*

Atlas Shrugged

28th Sep 2011, 03:27

The ONLY thing that a Manifold Pressure Gauge tells you is the amount of AIR that is AVAILABLE to the engine............nothing more.

Aerozepplin

28th Sep 2011, 04:03

Indeed.

Blame engine damage on overboosting when the plane is in the hangar.
29.9"/0rpm!!! :eek:

Jabawocky

28th Sep 2011, 04:23

Amen. :ok:

...still single

28th Sep 2011, 07:58

Is there even a single POH that prohibits over square engine settings?

Honest question. I'd like to know.

knox

28th Sep 2011, 09:49

Some very interesting and informative posts on this subject, nice to see a healthy discussion taking place.
A lot of different opinions on leaning procedures and which is best, maybe time for a thread on LOP v ROP or would that just be opening up a can of worms??

Knox.

Jabawocky

28th Sep 2011, 11:32

knox

with all due respect, there are not lots of opinions at all.

There always seems to be facts and evidence based operations, and OWT's.

As for a thread on LOP v ROP :ugh: that will degenerate for sure, but let me say this, the lower case v in a title suggests one is opposed to the other, like Qld v NSW in a sport. One is opposed to the other scoring more points.

LOP is not opposed to ROP. ROP operations are perfectly valid and safe to do so provided they are conducted properly. Same for LOP ops. Heck ALL my takeoff and climbs are done ROP, and once climbing into the upper levels you are chasing best power and using a ROP setting that would not be wise at sea level. I often use ROP above 10'000. LOP is just more fuel efficient and kinder on your engine than running 100-200 ROP for not much speed loss.

Grasshopper you have much learning ahead of you!;)

FGD135

28th Sep 2011, 12:57

Yes, many OWTs and myths have featured in this thread.

One that has bobbed it head up, but not been addressed is the one about the act of "increasing pitch" on the prop on final approach which then "increases drag" and helps you to slow down.

There is a widespread myth about the effects of increasing prop RPM on final approach. I have heard some pilots express the view that the whole reason for increasing the prop RPM is to slow you down (!).

Some pilots seem to think that, because you are driving the blades to their fine pitch stops, this then causes drag - in the rearwards direction - which then causes the aircraft to decelerate.

To these pilots, the obvious question is: so what happens on takeoff, when the blades are again on the fine pitch stops (for the early stages of the takeoff, at least). Is the prop again causing drag, reducing the acceleration?

It must be clarified at this stage that the kind of "drag" we are talking about here is the drag that is acting in the direction opposite to that of the propeller thrust force. I shall refer to this drag as "thrust-opposing drag". It has the same effect on the aircraft as skin friction and induced drag.

The wing produces lift + drag simultaneously, does it not?

A prop cannot produce thrust and thrust-opposing drag at the same time!

Yes, there is the induced drag that the prop blades produce, but the direction of that drag is such that, rather than opposing the aircraft forward motion, it opposes the prop rotation and creates the torque force that must be balanced by the engine torque.

But we are not talking about that drag; we are talking about the thrust-opposing drag that is sometimes provided by the prop(s).

As it turns out, there is an element of truth to the OWT which says that "increasing prop RPM on final slows you down".

Sometimes, increasing prop RPM will indeed cause the prop to commence generating thrust-opposing drag.

And sometimes not. It depends on whether the torque has gone negative or not.

Increasing the prop RPM causes a reduction in torque. If the engine torque prior to the reduction was a small positive value, then the reduction can be enough to cause the resultant to be negative.

If the resultant torque is negative, then the prop will be generating no thrust but rather, thrust-opposing drag. This situation is also known as "back-driving", "discing", "windmilling" and plain old "negative torque".

The key ingredient to this outcome was the small positive torque that existed before the act of increasing the prop RPM.

So, what this all means is: increasing prop RPM on final may or may not cause an increase in drag.

If an undesired drag from the prop should be experienced at any time - not just while on final approach - the remedy is simple: just increase the torque until it returns to a positive value.

To do that, just push the throttle lever forward a touch! If a turboprop, just push the power lever forward a touch!

Those levers are part of a set of controls that set the engine torque. The other part of that set are the prop RPM levers. We knew that didn't we?

AirScrew

28th Sep 2011, 13:51

An instructor told me that this mythical rule comes from Radial Engine procedures (non-geared).

There is an abundance of info on the benefits of running Lyco/Conti engines oversquare and LOP.
Check your engine manual.
It will very clearly show (in a table MAP vs RPM vs Alt) the oversquare limits.

MakeItHappenCaptain

28th Sep 2011, 14:30

FGD135
Maybe I've oversimplified the effect, but was I actually wrong? You do understand that relative airflow changes depending on rpm AND airspeed?
ie. On final and ready to start your T/O roll are WAY different

This was only one part of the reason for setting pitch fine on short final. I see benefit in having the engine ready for a go around if required, especially in the post PPL training environment where the instinctive manipulation of controls in the correct order has not yet developed. More importantly, perusing my collection of flight manuals for finals checks;

Beech;
55 Props low pitch (high rpm)
58 Same
65 Advance to full low pitch at min appch speed
80 Props low pitch
76 Props high rpm
Britten Norman
BN2 props fully fine
Cessna;
172RG Prop high rpm
182 Same
206 Same
208 Prop max
210 Prop high rpm
303 Props high rpm
310 Props full forward
337 Props high rpm
340 Props full forward
401 Props forward
Decathlon Prop full increase rpm
DH8 Condition levers max rpm
Mooney M20 Prop full increase
Partenavia P68 Props full forward
A-viator Condition Levers Max 100% Np

Are we seeing a pattern here?

You are going to have to look hard to find an exception.

It's not an OWT.

multime

28th Sep 2011, 14:49

Continental.
But i,ll probably get blasted out of the park on this one too.
Engine manufacturers have guide lines, why F with that.
1000,s of hrs below 500 ft. I,m still here. What would i know.

MakeItHappenCaptain

28th Sep 2011, 15:06

Contis? Not as a rule, but Aztec C is the one exception I did find.

Props high cruise rpm

Amplified explanation is to prevent engine overspeed in the event of sudden throttle openings, but this is the only one I've found.

knox

28th Sep 2011, 17:26

knox

with all due respect, there are not lots of opinions at all.

Grasshopper you have much learning ahead of you!;)

Yeah maybe my england could have been better in that post as quite clearly there is 2 methods LOP or ROP.
Yes the learning never stops in this industry, I'll be a grasshopper for a longtime yet :D

I'm mainly flying lyc's at the mo and I came across this from the manufacturer
http://www.lycoming.textron.com/support/troubleshooting/resources/SSP700A.pdf

Knox

Aerozepplin

28th Sep 2011, 21:23

Knox, have a thread search for the terms ROP, LOP, lean, etc. There have been some great threads on the matter in the past. Mr Chimbu and Jaba in particular comes to mind as posting some great info on those.

Then of course reading through Pelican's Perch. Then reading it again. Then several more times.

The Lyc/TCM references have lots of good info, but also some bad stuff. I've seen pages where the classic CHT/EGT graph is displayed, sometimes even with 50LOP shown as "best economy", but then a warning about "there be dragons here".

They often state a risk of detonation, overheating, and engine damage. Yet, what is the best measure of engine temperature (and therefore internal pressure)? CHT. Which is shown as dropping of sharply when LOP, to a CHT that would require 200 degrees+ if ROP. But don't take my word for it though, I'm just a faceless internet name. The words of Chimbu and Jaba, etc however, I would trust.

rioncentu

28th Sep 2011, 22:18

If the APS (Advanced Pilots Seminars) come back to OZ at any stage, be sure to go along.

You can do them on line but it wouldn't be the same.

Or as suggested - Read pelicans perch.

They are a great bunch of presenters and will turn verything you are tought on its ear.

Even had the pleasure of dinner and beers with Braly and Atkinson at Darling Harbour. What a pair of characters.

Of interest is they provide the Operating Handbook for the Curtis Wright radial engine which was run LOP.

As Jaba says - It's not necessarily LOP v ROP. I follow what the APS semimars taught but still run ROP.

Stationair8

29th Sep 2011, 01:45

The 1979 Piper Aztec F that I flew for a while had charts for both square settings such as climb 25"/2500 RPM, cruise at 23"/2300RPPM(which we used), and also charts for over square settings such as cruise of 26"/2400 RPM.

Old timer who flew PA-24's and PA-30's in the 60's, said they always operated them over-square, and always got better than TBO on the engines.

Regarding the max RPM for landing, most of the turbo-props I have flown:

EMB110 props stayed at 91% for Landing,

Beech 90 props at 1700 or 1900 RPM for landing(variation due to various models and if Raisebeck modified etc). Also some of these versions had a requirement in the AFM for the props to be increased to 1900 RPM during an ILS approach.

Beech 200/300 props go up to 1900 RPM for landing for three bladed versions.

Shorts 330, props were placed into climb setting in the event of a go around.

Jabawocky

29th Sep 2011, 01:52

MIHC

I am not sure anyone said full fine on short final was an OWT of sorts, if I did say that well clearly I am losing the plot. What I did say..... Why not land with the pitch control still set from the cruise. say 2300 RPM. Why not, in the event of a baulked landing, RED/BLUE/BLACK, in about the time you read that, or if you can do all at the same time, who cares. It will not make any difference. Now you are climbing away at full bore max rate.

So if it makes you feel better going full fine on final, well do so, just dont go boring downwind at 120 knots and back to 2700RPM making an almight noise that only winds up the people who leave near to the aerodrome. They get enough on takeoff so halve the number of 2700RPM events:ok:

Despite what your instructor once taught you, you can learn a whole new more neighbour friendly and sensible "checklist" that is not dangerous and is "better" in some ways.

Stationair8

29th Sep 2011, 02:03

Jabba, that was what I was taught as well, perhaps those old experienced grey haired instructors and CP's know something afterall!!!

Bet not too many operaters of GTSIO-520 get the pilots to shove the prop levers to max on downwind or final?

FGD135

29th Sep 2011, 02:26

MIHC,

As Jaba has said, nobody is saying that "prop up" on final is an OWT.

My post was purely to address the myths that surround this practice.

Personally, I bring the prop levers up on final approach (in accordance with the SOP for the type), but I don't do it until the props are already on the fine pitch stops.

How does one know when the props are on the fine pitch stops? Go back and look at post #25 by Lasiorhinus.

SpyderPig

29th Sep 2011, 06:15

1 vote for best thread on DG&P right now :ok::D

AerobaticArcher

29th Sep 2011, 07:16

The angle of attack of the propeller is changing with the RPM change. At high RPM (full fine) the propeller may have a negative angle of attack, and is acting as a big braking disc. When you are in low RPM (full coarse) the opposite happens, there may still be an angle of attack on the blades which produces thrust (or lift).

Avgas172

29th Sep 2011, 07:53

blah .... my 172 is always on the fine pitch stops.

jas24zzk

29th Sep 2011, 09:27

sure its not on the feather locks?

T28D

29th Sep 2011, 09:54

One must be really careful with any geared engine not to allow the propellor to drive the engine, i.e. maintain positive manifold pressure and enough blade angle to always load the engine, on big radials this is really important as it gets serious expensive very quickly if you miss handle them !!

R1820 on final 1800 rpm 20 inches, forget the fine pitch bit close the throttle as you flare and the propellor comes back to fine as the power comes off during the roll out.

Even the non geared R985 Pratt is same , don't let the prop drive the engine, the counter weights get really unhappy.

Round engines require finesse, absolutely reliable if you treat them well.

Geared Continental is similar hold coarse until the round out power reduction.

jas24zzk

29th Sep 2011, 11:01

Having read all of this, given it some consideration, read a few more bits and pieces, I thought it was time I posted something a little more serious.

To me, not going fully fine on short final has ants on it. (I am going to restrict my reply to Flat non geared Piston engine types)

Many pilots are ham fisted and just ram the pitch lever forward. If you have a bit of power on still, the chance of beating the governor are huge. You don't whack full back stick to rotate, so why treat a condition lever different?

I thought about what was being suggested with leaving the prop in the cruise setting for landing and almost thought it wasn't a bad idea, and that it could do no harm. No harm to the engine, but a whole load of harm when needed. It isn't going to be the short period of over square that does the damage, its going to be the simple lack of performance, and i think that engine damage is going to be the least of the worries. I thought about it long enough that I thought I might go and fly some practice approaches with that set-up and see what eventuates(at a safe height)

Then reality hit me.....the CSU equipped type I fly the most, would kill you in this configuration...lord knows its killed enough when being flown by the book.

PA-32-300!

The reality phase was reflecting back on a few flights and recalling the power used on some approaches. One in particular in my memory was my first time into Great Lakes. Unfamiliar strip, unexpected sink, first approach to that kind of gradient, almost max weight............ 2600 rpm...yes thats right almost full power

Do I want to be in an aeroplane that suffers from reverse command, with cruise RPM set on short final, and power not available the moment i want it? NO not yesterday, today, tomorrow or EVER!. It is bad enough that you have to pre-empt your power needs and wind it up early, than to be dealing with having to go for a second lever to get the power you need...or worse forgetting its set for cruise.

Sorry but it just seems a bit d0pey to me to give yourself something extra to do in a pressure situation, when you can pre-empt that situation by setting the aeroplane up for what you may need BEFORE you need it.

Having limited time in a 210 (the only comparable type so far mentioned) I cannot really comment on the comparison, other to say, that the 210 would probably give you the time to react and get the prop lever forward, but a chog 6 won't!. You are already on the back of the drag curve, so the chog 6 happily decelerates. Really not a place you want to be in.

-------------------------------------------------------------------

Mixture management.

I concur with not touching the mixture for the begining of the descent.
In an injected/csu equipped, I like to have the mix at roughly 75% forward when i level off for the circuit(with a keen eye on the cht/egt), and go for 100% at the same time I go fully fine on the prop....another thing i don't have to deal with in the event of a go-around. Once on the ground I'll wind the mixture back again as part of my post landing clean-up to avoid fouling. I find in PXG, 6 turns works just fine.
----------------------------------------------------------------------

At the end of the day, it does come down to your POH, anything else is the realm of test pilots.....hence they get paid the big bucks and get to write the stories that tell you how to fly it.

Leaving pitch in the cruise setting for landing to me is a NWT.....and if you have flown the chog 6, then you would know the circuit setting is different to the cruise in both MAP and RPM.

Cheers Big Ears

Jabawocky

29th Sep 2011, 11:49

Is this a wind up?

Keen eye on egt/cht on descent......:rolleyes:

All yours Chuckles!

jas24zzk

29th Sep 2011, 12:07

c;mon jab,
you should know me well enough by now that I don't write something that lengthy to be a wind up.

I keep an eye on the EGT/CHT to avoid shock cooling. i.e watching the cooling rates. if i think its cooling too quick, i'll make some adjustments to compensate.....a couple of options there, more power, less fuel, slow down. Though i rarely have a problem with it as i tend to make powered descents. turbulence probably generates the biggest problem when i am forced to run a lower power setting and slow down.

BrokenConrod

29th Sep 2011, 12:24

I keep an eye on the EGT/CHT to avoid shock cooling. i.e watching the cooling rates. if i think its cooling too quick, i'll make some adjustments to compensate.....a couple of options there, more power, less fuel, slow down. .

Ah yes, shock cooling - you gotta watch out for that! :ok:

...and if you have flown the chog 6, then you would know the circuit setting is different to the cruise in both MAP and RPM.I would? :confused:

BC :cool:

FGD135

29th Sep 2011, 13:32

What’s happening?

Clinton, you are varying the prop between low drag (coarse pitch) and high drag (fine pitch). You describe the high drag situation as particularly noticeable.

The only way to get the drag down to (effectively) zero would be to feather it, but the single engine (piston) CSU does not have that ability.

When the mixture goes to ICO, the prop RPM will tend to decrease. The CSU, doing its job, will see the RPM drop and send the props more fine, in an effort to bring the RPM back up to "on-speed". The CSU doesn't know the engine has failed; all it knows is that the the prop is now in an "underspeed" condition.

But the props hit the fine pitch stops - and the RPM does not come back to on-speed (unless you are in a dive, with plenty of airspeed).

If the prop RPM is still within the governing range however, you can command a more coarse - and lower drag - setting by pulling back the RPM lever.

If however, your airspeed is too low, then the prop RPM will be below the governing range but on the fine pitch stops thus generating the high drag.

At high RPM (full fine) the propeller may have a negative angle of attack, and is acting as a big braking disc.
Only if the torque is low enough to result in the CSU commanding the fine blade angles.

This is exactly what T28D then said - but note the different terminology he uses:

One must be really careful with any (geared) engine not to allow the propellor to drive the engine, i.e. maintain positive manifold pressure and enough blade angle to always load the engine ...

Jamair

29th Sep 2011, 13:50

This discussion contains 3 of my 4 pet hates in piston engine management fairy tales
- power reduction on takeoff
- LoP fallacies
- Shock cooling, and
- running down the turbo after landing.

I was as ignorant as the next sprog product of a generic training program, until I hooked up with Chuckles & spent some time reading both Pelicans Perch and the POH / engine manual for the aircraft I was flying. I flew Chucks mighty Bonza and used the JPI and the LOP procedure under his tutelage. Then when I bought an aeroplane - before I even flew it the first time - I had a JPI installed so I knew for FACT what was going on under the cowls. Then I installed GAMI-jectors. I downloaded literally REAMS of data from the system and learned how to operate the engines properly, be it LOP or ROP. I would have thought with the profusion of engine data systems on piston-props these days, a lot of these would have been laid to rest. Apparently not.

Reducing power on initial climb:
All the normally aspirated flat aero engines, be they injected or carburetted, include in the design of the fuel system an enrichment device that adds extra fuel at full throttle, to reduce CHT and thus the risk of detonation in high power settings such as take-off. As soon as you pull the throttle back a little, like when you reduce to 2500rpm / 25" MAP, you shut off this feature and make the engine run hotter, just when you want it as cool as possible. LEAVE THE BLOODY THROTTLE ALONE! Once you level off set it per the power tables, and if that's above full throttle altitude pull it back just a bit to disable the enrichment. If you have decent engine instrumentation you can experiment and see the effects this stuff has.... like watching the EGT / CHT go UP when you pull the throttle back a little.:eek:

LOP / ROP:
Both are completely valid - if you take the time to learn how to do them correctly. The worst place to run an engine is 'a little rich' of peak EGT, or 'a little lean' of peak EGT. We use EGT for power setting because it responds almost instantly to changes and most aircraft have an EGT gauge. You need to be aware that the PURPOSE of EGT is to give an indication of CHT, which is what really matters. Of CRITICAL importance to understand is that peak CHT - where you absolutely DON'T want to be - is 50 or so degrees either side of peak EGT. Once you find the peak EGT with mixture adjustment you need to get well rich of it or well lean of it. You don't shag engines by 'running too lean' (bloody Whyalla) - you shag 'em by not running lean enough for LOP, or not running rich enough for ROP. Bear in mind also that the single point EGT gauge is only looking at one point in the 4/6/8 cylinder exhaust system, and not necessarily the hottest point at that. You REALLY need a multi-function all-cylinder digital engine monitor. I would not fly a piston-prop aircraft without one - well, not one I was paying the maintenance on anyway:}

Shock cooling:
Bloody BOLLOCKS. If the engine is running it's producing heat; nothing shocking about that. If it ain't running it's all cooling - no big shocks there (at least, not if the engine baffles are working). There are sound reasons to not yank the throttles closed at ToD, but shock cooling isn't one of them. Reverse-loading a drivetrain like a GTSIO gearbox is a bad idea, so slapping the throttle shut on a Titan in flight will not get you any brownie points with the boss. The greatest likelihood of a successful landing is in a stabilised approach, which precludes dirty great power alterations during the descent, which is best achieved by a planned steady power reduction throughout, not by pulling the levers to the back and sticking the nose down. All valid points, but shock cooling...:rolleyes:.... look to the JPI once again.

Running down the turbo:
starts when you reduce power during descent and by the time you're at low power on final the turbo is as cool as its gunna get. The longer the engine runs on the ground after landing, the hotter it gets (to a point) and sitting on the apron with the pax having a sauna while you 'run down the turbo' for 3 minutes is just silly. The JPI data proves it.

The test of an OWT or just plain ignorance is whether the other party can prove their position. All these points are eminently provable.

Rant over :zzz:

Aerozepplin

29th Sep 2011, 21:09

The JPI data proves it

:ok:

That's what I love to hear. There's so much data avaliable from the good ol' days and from modern digital instruments that the OWTs and bad operating practices shouldn't stand a chance.

I'd love to get some more equipment hooked up to an aircraft, particually a rubbish little 152 or Tommy to test some of the things we're told by the flying schools. Carb heat use being one (how quickly does the exhaust manifold cool down in a glide? does it cool down? how much heat is needed from the source to provide reliable carb heat) etc.

Jabawocky

30th Sep 2011, 00:48

c;mon jab,
you should know me well enough by now that I don't write something that lengthy to be a wind up.

Jas.......I am not sure how I am supposed to know you well enough, and if I do know you outside pprune land, suggest that we get together for some airborne education as per Jamiars post above.

SHOCK COOLING.....you mean like this?
m2BSfgnCU2Q

or this
NlBLwEfZCYI&feature=related

So shock cooling, well short of diving into a lake, I think you have far more important things to worry about on descent, unless there is a lake in close proximity. Shock Heating is probably more severe than cooling as far as Delta T is concerned but nobody seems to worry about starting their engines (except in freezing places but they use sump heaters etc).

Carb heat use being one (how quickly does the exhaust manifold cool down in a glide? does it cool down? how much heat is needed from the source to provide reliable carb heat) etc.

This is an excellent question. :ok: I can't quote you numbers off the top of my head, but I have had the good fortune to be testing a beautiful RV-7A of late, it has an awesome Dynon Skyview panel and the owner put a carby temp sensor on the O-360 and has this displayed on the EMS page. It is quite interesting to watch the temp change with throttle on and off, but I have not paid particular attention to how quick the carby heat works after a long power off descent. Maybe this weekend I will have another play and see what it does. Download of data would be interesting too! If I find anything worthy of reporting I will do so next week.

J:ok:

Aerozepplin

30th Sep 2011, 01:04

Most excellent.

It has direct safety implications, especially in the training environment where one often spends a lot of time at idle. We're taught the standard "engine warm" every 500-1000ft, which has been established to provide negligable CHT negligible, but maybe some useful benefit for the carb heat?

FGD135

30th Sep 2011, 03:10

Jamair,

Great post. It should be recognised that you, Chimbu and Jaba have put in many many hours of posting time over the years correcting myths and OWTs that have been planted by ignorant instructors.

I sincerely believe that eventually, thanks largely to Pprune and the efforts of you three, these myths will be completely eradicated across Australia!

mcgrath50

30th Sep 2011, 11:07

As AeroZ started to bring up, during long descents particularly practice forced landings, I was always taught to 'warm the engine'. Is this too an OWT as I was under the impression it was to keep everything heated and ready to go on go-around, but as mentioned above, if the engine is ticking over, it is warm.

Jabawocky

30th Sep 2011, 11:21

It takes a lot more than a forced landing practise to cool the engine to a point where a go around is conducted with a critically cool engine.

Go try it with an engine monitor. If your oil temp is below the minimum recommended ...... Check your oil temp instrument/ sender :}

Think touch n goes..... No different. Missed approach? Yep no different.

Another OWT BUSTED!!!! :ok:

PS : I once believed this rubbish I was taught too.:ugh:

Avgas172

30th Sep 2011, 11:46

Another OWT BUSTED!!!!

OK .... in this day and age I think it's time to transfer the OWT into the 'urban myth' (UM) lest we shall be smite by the great unwashed ....

jas24zzk

30th Sep 2011, 13:26

Jas.......I am not sure how I am supposed to know you well enough, and if I do know you outside PPRuNe land, suggest that we get together for some airborne education as per Jamiars post above.

Jaba, just kinda figured you'd seen enough posts from me over the years to figure out when i'm jesting :\

If you're ever in the YCEM area, i'll take you up on that :ok:

Your video's. The first. Isn't that simply extreme water washing of the blades? alternatively, on the Pilots incident report, didn't he write 'multiple water induced flameout' as his cause of accident?

The second.........thats simply the marine corp's method of helping the greens with man made reefs. :}

As for Jamair's post. A good read indeed.
Power Reduction on after take-off. Silly idea. It climbs better with more power anyway.:} Most CSU types have a 5 min limit on take-off power. That doesn't say pull the power immediately. 5 mins gives you enough time to get clear of the circuit and your heading and cruise climb sorted.
That got me thinking about driving twins, and the need/desire to get them props in sync. Looking at my BE95 docs, for ISA thats going to be 25.5/2450 to remain in the MCP envelope. I even perused the pic i have the panels of 2 of the travel airs I fly looking for a time limit placard...couldn't find it. Open to suggestions here, and will go chat to a baron owner i know who has done a couple of BPPP's and see what he has to say.

ROP/LOP. :ok: when in doubt consult the bible :8

Shock cooling. ok ok....blame my time hanging around glider ops where shock cooling presents a very real problem for the Tugs.

Turbo cooling. absolute drivel.....i just crack up at the ricer owners that fit turbo timers. They aren't pushing it hard enough to need it. If it needed it the factory would fit it...and damm likewise for aero engines. The only time a turbo timer really needs consideration is on a vehicle being used for towing, and even then you should consider what the vehicle was doing prior to your desired shutdown. if you have been moping around town, you're pretty safe to shut down, but if you have just worked it hard to climb a big hill and want to stop at the top for a cuppa tea and sticky bun, then sure let the turbo timer do its thing, coz the trans could probably use the help also. The only factory fitted 'turbo timer' i have seen is on my Fathers Mack. It has an electronic cummins turbo in it. Tho it doesn't time things, it actually checks turbo temperature, and prevents shut down until the temps come down to the right parameters.....sometimes as little as ten seconds at most 2 minutes.

Loving this thread.

Jas

AerobaticArcher

30th Sep 2011, 16:19

Early 58 Barons (3 blade props) have a T/O-MCP setting of Full Throttle/2700 RPM, no power reduction required. Max cruise power on the other hand is 24.5"/2500 RPM. The same practice is applicabe to the 402Cs. Only aircraft I flew witha 5 minute limit was C206/210, from what I was told, it was a heat related thing, but never been able to confirm that.

The company I worked for had a policy that ops at night or in IMC, aircraft was to be climbed at best rate and power left at T/O until through the MSA/LSALT, which was only a couple of minutes worst case.

PLovett

1st Oct 2011, 02:27

Most power limitations I have seen are on RPM, not MP. This was for aircraft such as the C206, 207 :yuk: and the 210. :ok:

T28D

1st Oct 2011, 02:34

Engine manufacturers spend a lot of money in the certification process determining how their product should be operated and when matched with an airframe where the green arcs on instruments should be placed and any do not operate ranges due to engine/airframe vibration issues.

So clearly it is OK to operate in the "green" all day without causing grief.

As a general rule running low compression slow revving engines at upper power settings is better for them than running them soft, less chance of cylinder glazing and better ring pressure on cylinder walls as most aircraft engines have Keystone Compression Rings.

Heat is not the enemy, if the engine is producing power it will be generating heat, there are more problems induced by rapid throttle moves particularly from low power to high power than will ever be induced by so called "shock cooling".

Rapid movements introduce lots of cool fuel/air mix without allowing the cylinders to heat up and at the same time the extra stress on the engine leads to cylinder head cracking particularly around the sparkplug area.

Rule of thumb with big radials is if you can see your hand moving the throttle you are moving it too fast !!!

The major scource of engine wear and low life is the number of times it is heated and cooled (thermal cycles) running the engine for long periods at proper power settings is good for the engine.

Another urban myth to expunge is the one that says a good engine does not use oil, Engines should use oil, lubricates the upper cylinder.

It is the useage pattern that is important, yet many owners/operators don't record oil use, if they did it is one of the best indicators of engine condition along with cylinder leak down tests.

Jabawocky

1st Oct 2011, 11:05

Ok folks, time for a small thread drift but a very educational one.

For the simple folk....remember this is just educational, just because you do not fly a Turbo Normalised SR22, does not mean there is nothing in this for you.

Why do many of us bang on here day after day about multi point EGT CHT engine monitors?

Why do we also harp on about actually having the education on how to understand what that EMS is telling you?

Well here is a SB from Tornado Alley Turbo....and for an SB about a problem they most likely did not create (plug choice), they really have to be commended for the quality of the SB.

I hope this is a good educational read for all.

http://www.taturbo.com/TATSR22-SB11-05%20fine%20wire%20spark%20plugs%20initial%20release%20sept% 2023%202011.pdf

And as pilots we should all be taking a closer look at our plugs, oil and general maintenance, even if your LAME does all the work.

Cheers

J:ok:

MakeItHappenCaptain

1st Oct 2011, 17:36

Jaba,
Your assumption that I need full fine to rectify my approaches is way off.
I have no problems with my students being shown this as a way to get their approach back to where it should be if required as long as they do it gently. Yeah, getting the approach right in the first place is preferable, but that doesn't always happen.

This is in addition to CAR 138;
The PIC of the aircraft must comply with a requirement, procedure, instruction or limitation concerning the operation of the aircraft that is set out in the manual.

S8,
Same, definitely didn't "shove" my IGSO-480s into full fine, and definitely no argument that some aircraft flight manuals spec less than max pitch for landing.

If so, they will be operated in this way, but in clarification, I was against the apparent generalisation that all aircraft should be operated in this way (again, feel free to correct me if this is wrong). If a commercial operator has to use the flight manual, why should a private pilot be taught not to?

I'm sure everyone is aware of the liability implications involved with this mentality. I respect and am an avid fan of people like Deakin, but this one's a bit different.

Katoom

1st Oct 2011, 21:57

Why "Over Square" Is Good (http://www.avweb.com/news/airman/184483-1.html)

Jabawocky

1st Oct 2011, 22:12

You said
It does seem that some people here are advocating landing with the prop at the descent setting (correct me if I'm wrong).

If you don't slam the pitch into full fine while carrying Vref + say 30kts, you won't get the prop bouncing off the redline while it attempts to govern your hamfisted commands.

Pitch max will also provide a very useful source of drag to provide that last bit of deceleration over the fence and give you the best climb ability in the event of a go-around.

During a go-around, why wouldn't you maximise your RoC by using T/O power? Height is your friend. Get it ASAP! Once a a safe height, then use the max cont. pwr settings (which most likely are your baulked landing figures....coincidence?):ok:

I said
MIHC

I am not sure anyone said full fine on short final was an OWT of sorts, if I did say that well clearly I am losing the plot. What I did say..... Quote:
Why not land with the pitch control still set from the cruise. say 2300 RPM. Why not, in the event of a baulked landing, RED/BLUE/BLACK, in about the time you read that, or if you can do all at the same time, who cares. It will not make any difference. Now you are climbing away at full bore max rate.
So if it makes you feel better going full fine on final, well do so, just dont go boring downwind at 120 knots and back to 2700RPM making an almight noise that only winds up the people who leave near to the aerodrome. They get enough on takeoff so halve the number of 2700RPM events:ok:

Despite what your instructor once taught you, you can learn a whole new more neighbour friendly and sensible "checklist" that is not dangerous and is "better" in some ways.

Now lets examine this a little closer...........:bored:

Where does it say NOT to do what most are suggesting? Also Where does it say that you must do the full fine thing, i.e does it say on down wind or just over the fence ready for your feared GA?

What I and most others are saying is do not go blasting down final or earlier with 2700RPM, rather if you want it already in the fine position at some mystical point ob very short final, knock your socks off.

Now as for my assuming you need fine pitch to rectify your approaches I am sure you are skilled enough to get your profile right from 30 miles out, its not that hard if I can do it. But this is a common misuse of a big noise generator.

And re-read what I said, especially the first few words.
So if it makes you feel better going full fine on final, well do so, just dont go boring downwind at 120 knots and back to 2700RPM making an almight noise that only winds up the people who leave near to the aerodrome. They get enough on takeoff so halve the number of 2700RPM events:ok:

I am off out the door for more flight testing.....and I am really concerned about the approaches in this thing, how do I get full fine on late final.......its a fixed pitch cruise prop :eek: will I crash and burn in a GA, will I have no climb performance:uhoh:. Ohhh dear once they put a CSU on a C172 they should have recalled all the others with fixed props for a change out.:ooh:

Now yes I am taking the pi$$ a little here, and poking a bit of fun, but the point is........there is no danger in leaving the cruise rpm set, unless there is a LIMITATION saying otherwise. Remember RED/BLUE/BLACK :ok:

PLovett

1st Oct 2011, 23:02

My introduction to the oversquare world was in reading the book, "Charles Lindbergh's Wartime Diaries".

Lindbergh had been sent to the South Pacific as a representative of Lockheed and Consolidated aircraft companies to advise on the operation of their aircraft. He actually flew combat missions (as a civilian) and was surprised to hear so many of the other pilots declaring fuel emergencies when he still had plenty of fuel.

On investigation he found that none of the pilots had been instructed in long range cruise techniques (some things don't ever change) so his first job was to set up a lecture on the subject. He taught that you should set the lowest RPM with the highest MP (remember, most of these aircraft had automatic mixture control). It was only after his tour that the USAAF was able to undertake the mission to shoot down Admiral Yamamoto's aircraft.

I have to admit that when I first read the book I thought it was all wrong. It wasn't until I started reading John Deakin's articles (over and over until I understood them) and talked to Douggie Spriggs at Arkaroola (who has one of the most amazing libraries on all things aviation mechanical I have ever seen) that the light went on. As an aside it was Doug who arranged for George Braly to come to Australia to give evidence to the Coroner's Inquiry into the Whyalla Airlines crash (and didn't that put some noses out of joint).

MakeItHappenCaptain

2nd Oct 2011, 13:59

Jaba,
No dramas, discussion is good.

CAR 138 as quoted is where it says the POH MUST be complied with.
Before landing is where almost every POH states full fine. I am as guilty of assumptions as anyone, but to me before landing means on final, not downwind.

As for annoying the neighbours.....
I reckon if they live near an airport, either they love the noise :ok:
Or they knew it was there when they moved in and so should put up or shut up.:E

Something we do agree on?:}

slackie

2nd Oct 2011, 19:10

Fantastic thread... I for one have learnt something (thanks Jaba!). I will "cherry pick" a few methods for future use!! The articles by John Deakin certainly filled a couple of gaps in my knowledge... these should be required reading as part of a CSU rating!!:D:D

SpyderPig

2nd Oct 2011, 20:52

I too have learnt a great deal (also thanks Jaba) and am now looking forward to some interesting conversations with some instructors on a trip I have coming up. Lets hope I dont get in to much trouble stirring the pot with my Deakin-ish, far left handed ways of preaching it is ok to fly over square!

NIK320

2nd Oct 2011, 21:51

Turned out to be a thread packed with useful information. I think I have learnt more about engines from this than the CPL text.
I stumbled over this publication 'EGT and Combustion Analysis In A Nutshell (http://www.mediafire.com/?32uqldh0i0fxv3x)' during my research that discuses the mixture control elements we have been discussing. Figured you can never have to much information :)

Again thanks to Jaba for his tutelage :ok:

LeadSled

3rd Oct 2011, 02:05

If a commercial operator has to use the flight manual, why should a private pilot be taught not to?

Folks,
Compliance with the Airplane Flight Manual, AFM (by whatever name) included as part of the aircraft certification documentation is required by law.

It doesn't make a blind bit of difference what license the pilot in command holds, or what kind of operation is being condusted, from private through HCRPT, the same rules apply. The AFM is NOT a list of guidelines, hard requirements must be adhered to.

Look at the strife Jetstar got into ( as well as getting within less than 100' of plowing in) over changing a missed approach procedure without the approval of the Type Certificate Holder and the certifying National Aviation Authority, NAA.

Non-compliance will invalidate any insurance policy, a far greater danger than CASA giving you a hard time.

For un-certified aircraft, if the engine manufacturer has solid recommendations, follow them.

If you are going to do a missed approach with other than full fine, be very very aware of the boost limits and aeroplane performance at the chosen power setting ---- and it is a procedure consistent with the AFM.

Tootle pip!!

Jabawocky

3rd Oct 2011, 02:49

Katoom

That is a good article generally, but there is one paragraph that ruins it.
Finally (but very importantly), lower RPMs produce lower EGTs at a given power output. At 65% cruise in my airplane, the EGT at 30"/2100 is more than 50F lower than the EGT at 26"/2350. This allows me to lean very aggressively (I cruise right at peak EGT) without the danger of over-temping my exhaust valves or cylinder heads. I wind up with a cleaner engine (fewer deposits on exhaust valve stems and spark plugs) plus better fuel economy.

Now surely Mike has learned since 1995 that his thinking here is not based on proven test data. But a good article all the same if you ignore that one OWT ;).

Now the ALCOR article is interesting, I have not read it yet, and only scanned it, and spotted some OWT's in there too. Anyone else spot them? Chocky frog for the first three (not sure how many there are yet). Again possibly a good article but ruined with some pearlers of proven myths. I'll have a read later today, and see how well i stack up to all you eagle eye folk.

Aerozepplin

3rd Oct 2011, 03:22

"Lean misfire" would be one (leave it at that so as no to be greedy).

Rather than the engine misfiring the fairly steep drop in HP once lean of peak can, when the injectors aren't balanced, create a large power difference between different cylinders.

One question I had regarding operating a lower RPM however. From my understanding the heat in an engine is related to the proximity of peak pressure and TDC. For a given EGT (so a given combustion speed right?) but a slower piston speed the peak pressure would occure closer to TDC, so causing a higher pressure and temperature. Is this somethign to be mindful of?

What change does CHT show with changes in RPM?

Jabawocky

3rd Oct 2011, 04:06

Ohhhhhh Dear!!! :sad:

Sorry folks I have to retract that Chocky Frog offer........can't afford that many frogs :{

For what could have been a good article, and some of it was, it has been trashed.

So NIK320......be careful of all the good info out there....including mine http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/badteeth.gif

Aerozep, yes the PPP does move closer to TDC but at the typical RPM range 2100-2500 used in cruise power settings this is not an issue unless a minimum RPM is specified for your engine.

Setting 1700 maybe and a very high MP and a 50ROP mixture might get you pounding the piston right at TDC (you could work it out based on combustion time and ignition advance, but I am not keen to do that right now). That would be something to be concerned about.

jas24zzk

3rd Oct 2011, 05:03

damm! and I was up to 3 peppermint, 2 strawberry and 5 caramel ones!

T28D

3rd Oct 2011, 05:23

And you might have to take into account compression ratio and induction pressure

Jabawocky

3rd Oct 2011, 05:40

T28D, :ok:we did mention MP, but compression ratio is a very good point indeed , although most Lyc/TCM's are all about the same, fairly low. Compression is done a few ways, and no doubt your namesake machine develops plenty of it via forced means :).

This is where some of the dynamic ignition systems come into their own, but most GA engines are fixed.

NIK320

3rd Oct 2011, 13:03

If you are going to do a missed approach with other than full fine, be very very aware of the boost limits and aeroplane performance at the chosen power setting ---- and it is a procedure consistent with the AFM.
I dont think anyone mentioned doing that. Full power leaned with a low rpm is a stupid idea. 100% power with a lean mixture = holes in cylinder.

Sorry folks I have to retract that Chocky Frog offer........can't afford that many frogs
I guess that's to be expected when the document is that old. There is a fair bit of contradicting information when you start to compare the dozen odd documents we have dragged up over the 5 pages.

Still more than the CPL text book has on it :8

Jabawocky

3rd Oct 2011, 20:54

I see Mike learned a heap in the last 13 years :ok: I certainly did.

Have a read of this article compared to the 1995 one.

The Savvy Aviator #59: EGT, CHT and Leaning (http://www.avweb.com/news/savvyaviator/savvy_aviator_59_egt_cht_and_leaning_198162-1.html)

FGD135

4th Oct 2011, 04:10

The AFM is NOT a list of guidelines, hard requirements must be adhered to.

LeadSled,

You say "the AFM must be adhered to". But what is the legal situation when the AFM is using words and phrases that are more akin to recommendations and advice, rather than concrete directives?

multime

5th Oct 2011, 11:06

Because i,m still alive and well.
Get to go home.
Thats whats its about.

Jabawocky

5th Oct 2011, 11:39

what??????? :confused:

jas24zzk

5th Oct 2011, 11:42

You say "the AFM must be adhered to". But what is the legal situation when the AFM is using words and phrases that are more akin to recommendations and advice, rather than concrete directives?

Are you serious?

You do something outside the AFM's 'Advice' and have a prang....thankfully you survive

It goes to court.

It turns out, that you were operating outside of the AFM's 'advice', but based on experience.

You are asked to show the documentation supporting your operating procedure.

Where do you stand now legally? :ugh:

jas24zzk

5th Oct 2011, 12:58

actually, this touches on something i am very passionate about!

our Casa/caa/dot produced performance charts were pretty much the best in the world! but some legal muppet decided, that as they were not not produced by the manufacturer that CASA might get sued!

F*CK OFF!!!!!

So now we are expected to use the manufacturers documentation for p-charts..........we all know they are for best case scenario flown by test pilots......and we are also expected that to factor in the seppo's rules of thumb for slope, wind factors etc........ has casa sent us those guidlines? (still searching)

Casa produced p-charts include an error factor, for crap pilotage, aeroplane condition etc, and i have always managed to out perform them. I KNOW i can trust them to keep me safe.....can i do that for a rule of thumb?? and how would that rule of thumb stand up at my funeral?

Sad fact, POH's that still carry the CASA p-charts are now against the law, but we all know you can trust em.

over to the mob....

AerobaticArcher

5th Oct 2011, 13:07

jas24zzk, if you use the charts in the P.O.H and multiply by the factors required by CAO 20.7.4 (or applicable to your aircraft) you will have plenty of margin.

jas24zzk

5th Oct 2011, 13:11

i'll come back to you on that....................................................

quagmire

5th Oct 2011, 14:08

I can't fault Archer on that one.
Good drift too btw Jas

Aussie Bob

5th Oct 2011, 19:05

our Casa/caa/dot produced performance charts were pretty much the best in the world! but some legal muppet decided, that as they were not not produced by the manufacturer that CASA might get sued!

In this instance thank god for the lawyers. Putting nonsence into flight manuals is stupidity. CASA charts assumed that idiots fly. Perhaps some do but why put us all in the same bag. CASA performance charts were rubbish.

Jabawocky

5th Oct 2011, 22:25

Heheh great drift

LOP ops causes Cherokee runway over run:}

osmosis

6th Oct 2011, 04:52

I am surprised not more have mentioned the high MAP/low RPM settings introduced by Lindberg as posted by PLovett (#86). I remember watching a video of his techniques years ago but quality supporting material is not always easy to find.

High MAP & Low RPM, Advantages, Reduced Fuel Consumption, Long Engine Life, Running Aircraft Engines Over Square, Airplanes - EAI (http://www.experimentalaircraft.info/flight-planning/aircraft-engine.php)

In my time, flying schools with CSU SE/ME aircraft would not allow oversquare settings despite what was in the POH. Ignorance or caution, it didn't matter; they didn't allow it. Is this still the case today? With a few exceptions, I believe flying schools typically saw their pilots as not being mechanically aware; a sign of the times back then and probably more so today.

I wonder what the majority of round engine drivers think; oversquare: par for course perchance?

T28D

6th Oct 2011, 06:29

Round engines ALWAYS oversquare.

knox

10th Oct 2011, 19:09

So if my flight manual doesn't have any allowance to fly over square then it shouldn't be done?

Knox.

PA38 Captain

10th Oct 2011, 22:16

I consider myself a pretty experienced GA pilot. I was always taught and always teach to NEVER fly over square. It is the same as driving your car up a hill at low speed in a high gear. It causes detonation and does serious damage to your engine :ugh:. I fell sorry for all your bosses who have to pay the maintenance bill!

Chimbu chuckles

10th Oct 2011, 22:40

Well PA38 it might surprise you to know that MOST of the pilots advocating over square operations, and Lean Of Peak EGT etc, on this thread are actually aircraft owners. Some have experience measured in 10s of 1000s of hrs spread across the entire spectrum of piston powered aircraft types.

WE pay for the maintenance on our OWN aircraft.

With all due respect, a thousand hours, or even 50000hrs, instructing in a PA38 does not add up to 'a pretty experienced GA pilot'...its 1 hour repeated 5000 times. Your comments demonstrate ignorance married to the unshakeable self assurance of youth.

Wotcha gonna do if one day you find yourself a PA31Captain?

Jabawocky

10th Oct 2011, 22:49

Surely this is a wind up:}

You say experienced, so 500 hours of doing the same misguided thing is still experienced, just like 4000 hours of doing the same misguided things, now you are really very experienced.

In all of your experience have you ever bothered to take the time and effort, maybe a hundred hours or more to research and learn. What's more have you ever flown with an EDM or EMS and truly tested your research?

This thread alone is not exactly the best education source alone, but had you read it through from the start, realized who exactly was behind the posts and what their experience is, you might start off by asking some good questions.

I see while editing to add these photos, the brains of the operation have arrived, so now would be a great time to look listen and learn, chances are I will learn some more too!

So...here are a few pics, please tell me what you think, Inlet or Exhaust valves? Good shape or not? How have they been run for hundreds of hours? Undersquare and ROP or Oversquare and LOP?

http://i849.photobucket.com/albums/ab58/jaba430/E3b.jpg

http://i849.photobucket.com/albums/ab58/jaba430/E5.jpg

http://i849.photobucket.com/albums/ab58/jaba430/I4.jpg

Triple Captain

10th Oct 2011, 22:54

Wotcha gonna do if one day you find yourself a PA31Captain?

about 95 knots :hmm:

Chimbu chuckles

10th Oct 2011, 23:31

PA38 Captain full fine is indeed 1st gear...which is why we take off in full fine...then we climb in 2nd gear, on many aircraft you can actually leave it in 1st for the climb too and that can make perfect sense.

But usually we climb in 2nd and cruise in 3rd or 4th gear...sometimes we might even use overdrive (5th gear).

Or do you roar along the highway flogging your old banger in 1st all the time...maybe you drive an automatic?

Let me ask you a couple of questions - as an instructor you should blitz them.

1/. What does MP indicate?

2/. What else changes when you change prop RPM?

3/. What is the ONLY control in the cockpit that is capable of regulating engine power between 0% and 100%?

PA38 Captain

10th Oct 2011, 23:51

1/. What does MP indicate? MP gauge is simply a pressure altitude meter. That is why when we are on the ground it indicates atmospheric pressure(QNH).

2/. What else changes when you change prop RPM? The experimental mean pitch will change. For basic forces on a prop. Lift, drag, weight, thrust, total reaction. A fixed pitched prop only has one best efficiency and therefore MP will always increase with an increase in altitude.

3/. What is the ONLY control in the cockpit that is capable of regulating engine power between 0% and 100%? Magnetos. With only one mag working, fuel burn rate will be less and power will be below 100%. With both mags off power will be relatively lower depending on altitude and airspeed. Some operators recommend only using 2 mags for takeoff and switching one off when in the cruise.

Ok smart guy, i have a few Q's for you.

1. If we have a hung start, what is the easiest way to remedy it?
2. When operating the PT6, what is the most fuel efficient stage of flight?

Brian Abraham

10th Oct 2011, 23:52

Round engines ALWAYS oversquareSo can your good old normally aspirated flat, especially on take off, 29 inches and 2700RPM. Due to European noise restrictions Chimbu's pimp ride has the governor restricted to 2500RPM, which knocks max horsepower back to 285.

The following is a chart for the IO-720, but you'll find the engine you fly not greatly different. You can see that at 29.5" MAP you are permitted to operate between 2650 and 2300 RPM. Of course horsepower suffers, dropping from 400 to 350. At 1800 RPM you can operate up to 25" MAP max continuous.

http://i101.photobucket.com/albums/m56/babraham227/IO034.jpg

PA38 Captain

11th Oct 2011, 00:18

1. The MP gauge is simply a pressure altitude metre. That is why when parked on the ground it will show the atmospheric pressure(QNH).

2. When prop rpm is change the experimental mean pitch will change. Remember the four forces on a prop - lift, drag, weight, thrust, total reaction. This is not the case for reverse pitch however. That is why when we gain altitude with a fixed pitch prop the MP will rise but in a variable pitch prop it will remain constant below 10,000ft.

3. Magnetos are the only control that regulates the power. With both mags on we get 100% power or more(up to 110% depending on the day). When only one mag is on the power will be 100% but detonation can occur in diesel engines. With both mags off power will be considerably less. Some operators recommend running on both mags for takeoff but only one mag in the cruise to reduce SFC. (not recommended for diesel engines).

T28D

11th Oct 2011, 00:46

Wow 38 I own 3 round engines, and I must admit in 50 years of operations I never knew all that !!

You are a legend, please stop instructing .

jas24zzk

11th Oct 2011, 00:58

surely pa38 just came along for sh*ts and giggles.... i read his reply elsewhere and it was actually good.

if not, pa38, you should 1st, put your bong back in the cupboard, 2nd read this thread in its entirety....ALL of it! and some of the articles linked in responses.

T28D.....3!!!!! do you have any hair left??? :rolleyes::rolleyes:

Cheers
Jas

Jabawocky

11th Oct 2011, 02:20

Ohhh dear........... T28D and I will bang heads on many topics, and I am sure we are at odds on many more, but it seems that we do have a common appreciation for the fact based science of engine operation.
Wow 38 I own 3 round engines, and I must admit in 50 years of operations I never knew all that !!

You are a legend, please stop instructing .I have to say I can't agree more :ok:

Now PA38.......Chimbu asked a bunch of serious questions, the most serious one and the one most understood is the one you took the piss out of.

Have a go at Q3 would you, or we might stop taking pity on you and call you a Troll....which will usually end up in you being banned. How sad that would be:sad:

PS: Can you please tell me all about those valve pictures?

T28D

11th Oct 2011, 05:28

Jas T28D.....3!!!!! do you have any hair left??? Sure do I love round engines.

One of the real misunderstandings about round engines is they are said to be unreliable.

Absolute poppycock, once a round engine is running in steady state they are remarkably reliable, fact is if you consider the firing order 1,3,5,7,9,2,4,6,8 it becomes obvious there is less stress on the whole engine than say a horizontally opposed engine.

They fire sequentially around the master rod so the forces are not across the engine rather tangential to the output in simple terms.

Most big radials have quite sophisticated magneto systems which control any pre ignition.

My Wright 1820 is 52.5 inches 2700 rpm at takeoff developing 1425 HP, climbs at 36 inches 2400 rpm, cruise 30 inches 2000 rpm and coming home 1700 rpm 20 Inches

Oversquare all the way.

Likewise the Pratt 985 are 36 inches at 2300 rpm for takeoff, climb 33inches at 2100 rpm, cruise 29 inches at 1850 rpm and come home 20 inches at 1700 rpm.

Never a hint of detonation, why one must wonder ?? well because it is well within the thermal limits of the engine and there is no internal overcompressed mixture or overload on the engine.

BTW the Auto Mixture on the Wright 1820 is set LOP as they all are and I get a really nice soft grey exhaust colour, CHT 150 degrees C engine happy and leakdown pressures all above 75/80 .

So 38 what am I doing wrong with my engine handling ??

Chimbu chuckles

11th Oct 2011, 05:29

Well THAT is a relief - relax T28...one thing our mate is NOT is a Flying Instructor.

PA38 'captain' I am sure you have heard the expression 'Google is your friend'...in your case its simply not true.:hmm:

1. The MP gauge is simply a pressure altitude metre. That is why when parked on the ground it will show the atmospheric pressure(QNH).

2. When prop rpm is change the experimental mean pitch will change. Remember the four forces on a prop - lift, drag, weight, thrust, total reaction. This is not the case for reverse pitch however. That is why when we gain altitude with a fixed pitch prop the MP will rise but in a variable pitch prop it will remain constant below 10,000ft.

3. Magnetos are the only control that regulates the power. With both mags on we get 100% power or more(up to 110% depending on the day). When only one mag is on the power will be 100% but detonation can occur in diesel engines. With both mags off power will be considerably less. Some operators recommend running on both mags for takeoff but only one mag in the cruise to reduce SFC. (not recommended for diesel engines).

On the outside chance you're (maybe - BIG maybe) a student pilot, not merely a troll, I will correct your homework.

1/. Reasonable attempt - at least you didn't suggest it indicated 'power'. A knowledgeable pilot would have answered 'The Manifold Pressure Gauge measures Air Pressure in the induction manifold downstream of the throttle butterfly. On the ground with the engine shut down it should indicate field barometric pressure.

2/. Fail. A knowledgeable pilot would have answered (within the context of this thread) 'when propeller rpm is varied the speed of the engine driven fuel pump is also varied'. For FULL marks he might also mention that, particularly in a direct drive/non geared engine, the speed of the pistons sucking air into the cylinders is also varied thus, together with the changed fuel pump speed, varying the fuel/air ratio. Lower RPM with everything else held constant LEANS the mixture and higher RPM en-richens the mixture.

3/. UTTER fail. A knowledgeable pilot would have answered 'The mixture control is the only control that can vary power through the range 0% (idle cutoff) to 100% (somewhat leaner than full rich).'

Tankengine

11th Oct 2011, 05:52

I like the bit about single mag cruise not recommended for diesels though!:}

NZScion

11th Oct 2011, 05:57

Aren't you supposed to have carb heat on prior to landing in a turboprop too? :}

jas24zzk

11th Oct 2011, 06:09

NZScion,
at that point you are also a bit late to have turned on the PATH (Pilot Activated Tarma Heating)

:E:E:E

@T28,
I wasn't referring to maintenance, more what all the oil has done to you :}

osmosis

11th Oct 2011, 06:32

From the journal "No Short Days: The Struggle to Develop the R-2800", Kimble D. McCutcheon concludes that the P&Ws R2800 has been run with 150 in Hg. Kinda makes a mockery of the only-just-oversquare figures this thread contains. On the second last page:

"Using ADI, Walker was able to coax 3800 HP from an experimental “C” engine
at manifold pressures up to 150 in Hg! This is nearly twice the power the engine was designed to produce."

Interestingly, the pilots notes for the Sea Fury indicate 9.5 lb./sq. in. Is that only 19.3" Hg, or am I missing something?...... no I remember, it's indexed at zero on the ground.

Chimbu chuckles

11th Oct 2011, 06:46

Interestingly, the pilots notes for the Sea Fury indicate 9.5 lb./sq. in. Is that only 19.3" Hg, or am I missing something?

Given that 0 lb/sq in 'boost' equates to 29" Hg (atmospheric) I think yes, you're :ok:

I have no idea what 9.5 lbs/sq in equates to but if its much less than 60" Hg I will surprised.

OverFienD

11th Oct 2011, 06:50

What does MP indicate?

Inches of Mercury

What else changes when you change prop RPM?

The noise

What is the ONLY control in the cockpit that is capable of regulating engine power between 0% and 100%?

The Pilot

:rolleyes: Sorry... I just couldn't help myself!! :E

T28D

11th Oct 2011, 08:24

Chimbu,
A lot of the pommie engines measured boost as PSI above atmospheric, so at ground level on a 30 inch day 1015 Hpa 9.5 inches would equate to approx 52 inches which I think is about the limit for the sleeve valve centaurus in normal ops.

Stationair8

11th Oct 2011, 08:49

Why do the poms, measure boost different to the yankee method?

ForkTailedDrKiller

11th Oct 2011, 08:50

Ya gotta love this forum!

Just when I am thinking, "Geez this thread has become boring as bat sh*t! Six pages of posts on operating a simple reciprocating petrol engine - time to bring out the lock"!

Then along comes a PA38 Captain who says to the Chimbu Chuckler,

"Ok smart guy, i have a few Q's for you.
1. If we have a hung start, what is the easiest way to remedy it?
2. When operating the PT6, what is the most fuel efficient stage of flight?"

OK, I've got my feet up, the top off a cold Crownie, and a bowl of beer nuts on the table beside the Jason Recliner!

Over to you Chuckles! :ok:

Dr :8

jas24zzk

11th Oct 2011, 08:58

Why do the poms, measure boost different to the yankee method?

Seriously, thats like asking why they make their engines spin the wrong way?? Even the RR jets spin the wrong way :ugh::ugh::ugh:

I think you will find, that they pretty much talk in In/Hg these days. Back in the old days the seppos used Inches, and the pommes used pounds of boost because they could.

Neither method is wrong. The way they go about it is drastically different, but if you understand what/how is being measured, then you won't have any problems.

Jas.

PS why do the pommes hide their money under the soap?

jas24zzk

11th Oct 2011, 09:09

From the journal "No Short Days: The Struggle to Develop the R-2800", Kimble D. McCutcheon concludes that the P&Ws R2800 has been run with 150 in Hg. Kinda makes a mockery of the only-just-oversquare figures this thread contains. On the second last page:

Osmossis,
no mockery of the 'just oversquare' figures presented at all. If you recall back the early pages of the thread, it seemed agreed to keep it to normally aspirated normal engines, which we both know will never make 30" at 7000 feet. :ok:

Nice post on the P&W development tho, some links would be lovely bedtime reading :ok:
----------------------------------------------------

Dr, how could you possibly consider closing this thread?

sure the 'normal' engine has run its course of discussion, but it has naturally evolved, into round ones, tho i thought turbo/supercharging would have been would have been the logical next step, however beggars can't be choosers.

:ok: Thumbs up to most informative thread of the year :ok:

Cheers
Jas......off to the fridge for a fresh green tube

jas24zzk

11th Oct 2011, 09:27

Chimu wroteGiven that 0 lb/sq in 'boost' equates to 29" Hg (atmospheric) I think yes, you're

I have no idea what 9.5 lbs/sq in equates to but if its much less than 60" Hg I will surprised.

T28D Replied
Chimbu,
A lot of the pommie engines measured boost as PSI above atmospheric, so at ground level on a 30 inch day 1015 Hpa 9.5 inches would equate to approx 52 inches which I think is about the limit for the sleeve valve centaurus in normal ops.

I calculated
9.5 lbs/in = 19.32 + 29.92 = 49.24 inches.
Given the 52 inch limit, I conclude that we got the conversion correct.

The next obvious question has to be why do we zero the instrument on the ground? well if you do that, then you have set the QFE into the instrument, and therefore you can use 'extra' boost (for want of a better description), to get the power you want. You do not need to do any calculations based on pressure/temp etc, you just did it on the ground.

How that is corrected on a distance flight, i await the answer to.

Cheers
Jas

BOTTOMS UP GLUGG GLUGG GLUGG

Chimbu chuckles

11th Oct 2011, 09:35

Hey Forkie...I didn't see that post:ooh:

Pa38 'captain' - I owe you an abject apology - I only saw the second post of drivel NOT your first attempt at high humour:rolleyes:

1/. Sit on your hands and do fcking nuffink!!!

Well that is the SOP for the RR Trent 800s I sit between at work. Highly clever aeroplane the 777. As long as it has oil pressure ya throw the fuel at it and sit back and watch it do its thing. If its really unhappy, and only after several automatic dry motoring runs and subsequent attempts at a start, it gives up and you get an EICAS prompt that says "FCK IT - I give up - do some of that clever pilot ****"...so you put the FCS back in cutoff and call the gingerbeers.

Now on all the earlier jets I have flown, F28, Bae146, Citation 580 ultra, Falcon 200 and B767 you were the brains of the operation - sorry I didn't mean YOU I meant me and the people I flew with - so you would manually select the fuel control switch to cutoff...if the engine starter was still engaged you let it keep cranking for 30 seconds or so to clear all that heat etc then interrupted the start. If the starter has already cut out you do a dry motoring run before trying again.

2/. Well...I haven't sat between PT6s for about 16 years - and before that only for about 4000hrs (DHC6/E110/DHC7)...so memory is rusty. I certainly remember ridge soaring a full Twin Otter for about 15nm one day in PNG...both engines in feather...that was pretty efficient...hell of a lot of fun too...only lost a total of about 300' in that distance - at one stage I was HIGHER than when I selected both to feather. No pax, just freight of course. Another time I did the same thing in an empty Twotter at TOPD into Moresby and glided all the way to long finals at about 1500' - prolly 30 odd nm.

You may be wondering why I wasn't dobbed in by the co-pilot for these disgraceful departures from proper and good airmanship?

Well we flew em single pilot - Banderantes too - MUCH more fun than having some killjoy, no sense of humour fkwit PA38 Captain in the RHS.

And another time I remember flying back from New Britain to Port Moresby empty at FL250 in a -300 Twotter with -34 PT6s...that was pretty damn efficient - if memory serves I was still getting 150kts TAS...I think the PT6s may have actually been MAKING fuel that day! No, seriously:ok:

You didn't ask about TPE331s so I won't bore you with flying C441s - managed to get one of those from Nadi to Cooly, upwind, one night. I thought that was pretty efficient:ok:

Over to you lad.

ForkTailedDrKiller

11th Oct 2011, 09:53

Now on all the earlier jets I have flown, F28, Bae146, Citation 580 ultra, Falcon 200 and B767 you were the brains of the operation - sorry I didn't mean YOU I meant me and the people I flew with
Well we flew em single pilot - Banderantes too - MUCH more fun than having some killjoy, no sense of humour fkwit PA38 Captain in the RHS.
Oh shoot! Now I spilled me beer - and nearly pissed meself laughing!!

Dr :8

jas24zzk

11th Oct 2011, 10:25

Dr...get a catheta! train the dog to bring ya one from the fridge, you'll never have to move, nor 'run the gauntlet' again!

Cheers
Jas

PS have you seen the other bit of muppetry that PA38 and Pukeit are involved in? at least PA38 has his head screwed on for that one!

Jabawocky

11th Oct 2011, 10:27

Still waiting for an analysis on my valves!

You know, under square ROP or over square LOP

And how about them maintenance bills?

Chuckles..... Back to his old form:ok:

jas24zzk

11th Oct 2011, 10:30

oh sorry Jaba....

I've seen better valves than them!

I was refraining from posting due to my knowledge of what they should look like.

Cheers
Jas

PS answer your PM!

Jabawocky

11th Oct 2011, 10:42

What PM?

Try sending it again:ok:

BTW I see the other thread you are talking about. I will be along there shortly to help sort some sheep from goats.....along with video proof.

Some of you folk need could do with some serious education and Chimbu Chuckles has imparted much of it to me, and I am forever learning more. In this other case we went out and tested theory. We learned a heap. Hopefully you and others will too.

What I have learned is that despite a really good injection of knowledge from really clever folk, I have learned there is much more to learn, and most of it is not coming from the typical 200-300 hr instructor folk like PA38 captain.

Now back to normal viewing on engines hey.....:ok:

jas24zzk

11th Oct 2011, 10:53

response changed..pm pending

osmosis

11th Oct 2011, 22:49

js24zzk, with regard to the journal I mentioned, I've had my copy for a while but a quick giggle search leads to:
Piston Engines (http://www.enginehistory.org/engines.shtml)

And a reference to Centaurus engine data:
http://s1.bild.me/bilder/030611/thumb_7955180fury_9_10.jpg (http://www.bild.me/bild.php?file=7955180fury_9_10.jpg)

PA38 Captain

13th Oct 2011, 02:49

At chimpmunk chuckles. Well done on your failure with using google :D. Well that is the SOP for the RR Trent 800s I sit between at work. Highly clever aeroplane the 777. If you had any idea of what crap you were talking about, you would have realised that the 777 has GE90 engines on them. The only time you will find yourself between two of them is when you are wearing your skirt and handing out inflight refreshments. Faker alert!

Well done on gliding the twin otter 30NM on flight sim. If you did this in real life you would get shock cooling within 2 minutes and your boss would be giving you the bill for all 12 cracked cylinders:ugh:.

Oh oh ah ah what will the chipmunk come up with next???

PLovett

13th Oct 2011, 02:56

If you had any idea of what crap you were talking about, you would have realised that the 777 has GE90 engines on them. The only time you will find yourself between two of them is when you are wearing your skirt and handing out inflight refreshments. Faker alert!

Well done on gliding the twin otter 30NM on flight sim. If you did this in real life you would get shock cooling within 2 minutes and your boss would be giving you the bill for all 12 cracked cylinders.

Oh oh ah ah what will the chipmunk come up with next???

Comfy chair.....................check
Cold beverage.................check
Munchies.........................check

This is gonna' get interesting. :rolleyes:

PA38, you don't know what your saying. :=

jas24zzk

13th Oct 2011, 03:02

Major failure PA-38.....even i KNOW without google, the 777 has 3 engine options...like most Boeings and Airbus's.

GE, P&W and RR.

Hmm,
i didn't know the twotter had 12 cylinders!!! i always thought it had 2 BIG ones. Learn something new everyday:ugh:

Aerozepplin

13th Oct 2011, 03:27

I think it's time Sir Tomahawk (is it the grand return of Compylot?) be ignored for the troll he is. I know he thinks he’s pretty damn funny, but this tread is full of extremely valuable information.

People die because they don’t know what is going on inside their engine, because they’re afraid to lean, because they follow OWTs. I wouldn’t have spent the many many hours I have researching this material if it wasn’t for the wise words of Chuckles, Jaba, etc that I saw a few years ago. Maybe it’ll save my life one day? It’s certainly made me a better pilot and instructor.

So if you’re a troll, kindly go away, and if you’re genuine (50% increase in stall speed with a 30kt tailwind? God help us all if you are genuine) stop talking and listen.

SpyderPig

13th Oct 2011, 03:29

You dont need a long neck to be a goose eh. Keep the knowledge coming cap, I wish you were my instructor Lol

Jabawocky

13th Oct 2011, 03:38

I think we just discovered this twerp is a Troll.

No we discovered that earlier, it is just now confirmed.

Knowing what I know I think PA38wanker is about to find it a little harder to view PPRUNE. :}

Atlas Shrugged

13th Oct 2011, 05:54

MP will always increase with an increase in altitude.

I have been sitting here for 40 minutes trying to think of something to say about this.........nope..................still nuthin'.

and then there's this...

nuts on the table

Chimbu chuckles

13th Oct 2011, 05:55

Wow PA38 Fkwit...I stand in awe of your erudite ignorance. It is after all only exceeded by your bullet proof arrogance which is, without doubt, shielded by wings of steel.

Hang on while I duck into this phone box:E

Atlas Shrugged

13th Oct 2011, 06:35

Oh oh ah ah what will the chipmunk come up with next???

I do believe his correct user name is Chimbu Chuckles. Please, "captain" show a little respect.

If you, you purile little man of abject misery, had even a modicum of intelligence, you would soon discover the answer to that question and quite possibly more than you will ever even know lies in a very quick and very simple SEARCH of this, and indeed other forum.

Perhaps you may have bitten of slightly more than you can chew here fella and I watch with the utmost interest, your ultimate demise here on pPrune.

Oh, and by the way, you would have realised that the 777 has GE90 engines on them

****, last time I looked......this "777"

http://t1.gstatic.com/images?q=tbn:ANd9GcTxz5T6v9boYfy36oibzoqSlJMgJGzPsQ_MPzOyVrh zBqFm2whXiQ

had "Briggs & Strattons" on it. Why was I not told that this happened!!!! Why, why, why..........!!!!!!!!!!!!!!!

I HAVE been told, though, and what with all of the hoo haa going on with Flynny and his band of flying fkucwits, that the new -8 is gonna have some nice Lycoming pistons on her. Can't wait to get me first look at that fancy MP gauge climbin' outta Anchorage. Recon' she'd be up to around 367.2 inches just passn' Big Lake.

Jesus wept!

adsyj

13th Oct 2011, 06:44

How embarrassing for PA38:O

Mods please do not lock the thread as it is full of valuable info.

Atlas Shrugged

13th Oct 2011, 06:50

A lot is but there is always, well.............you know........one.

Much Ado

13th Oct 2011, 06:51

Well looking at PA38 Captain's IP address it seems he is posting from Hawkes Bay, Napier, UNZED.

The working assumption is a Kindy in Lucy Rd where, having failed advanced play dough, the teacher has banished him from the craft room and he has stumbled upon a computer with internet.

You guys have fun with him for a little while longer.:E

Trent 972

13th Oct 2011, 07:25

How embarrassing for PA38, a Traumahawk Captain and a Sheep Shagger. Poor bastard. :sad: Bwahahahaha!

T28D

13th Oct 2011, 07:34

I want some of that manifold pressure that increases with altitude, then I could stop the wear on my Supercharger, WOW good stuff.

Maybe someone could teach me altimetry again so I can understand how this phenomena works ???????

Jabawocky

13th Oct 2011, 07:48

Come on PA38guru

You can't tell me you have not rebuilt dozens of engines especially that mighty awesome O-235, so tell me all about this question I asked you about.

http://www.pprune.org/dg-p-general-aviation-questions/464708-flying-over-square-6.html#post6744060

Or do you need to be asked back into the play dough class to get some help from your friends?

jas24zzk

13th Oct 2011, 09:26

nice to see we are trying to get back on track. I have learn't so much but oh so little in the last 2 days.

:ugh::ugh::ugh:

Cheers
Jas

PS..its almost been fun tho

43Inches

13th Oct 2011, 10:20

Bring back auto-mixture a BMEP guage and the other bloke that knew engine and systems stuff... and some real aircraft that make real noise.

MakeItHappenCaptain

13th Oct 2011, 11:18

Queen airs.....augmenters.....:E:E:E

jas24zzk

13th Oct 2011, 11:19

A LOT to be said in favour of electronic fuel injection and things like FADEC.

However, once you do that, the engine boys will lose their basic fault finding skills very quickly

43Inches

13th Oct 2011, 11:47

A LOT to be said in favour of electronic fuel injection and things like FADEC.

It would interesting to see the stats on how many unwarranted shutdowns have been caused by FADEC, compared to actual mechanical failure.

Chimbu chuckles

13th Oct 2011, 14:58

Back...so...wassup?:}

nomorecatering

14th Oct 2011, 06:28

Ive also read and saved John Deakins articles on engine operation and subscribe to his way of thinking, and thats how I will operate an angine when I own it.

Unfortunately, as I'm not the boss, I have to conform to the SOPs, lest i want an invite for tea n bikkies with the boss.

Interestingly, when I started flying the G1000 Cessna, I was horrified at the temperature ranges the cylinder heads go through when training. A session of practice forced landings sees the CHTs bounce between 190F and 350F. According to the shock cooling crowd, a prime candidate for cylinder head cracking one would think.

Have I missed something? are IO360 cylinders built differently to IO550, are they built with more meat in light of the "training environment" they live.

The 'warming the engine' throttle to full power briefly in the middle of a PFL, contrary to several instructors who stated(hand on heart) this does actually warm the engine, and prevent a failure. In reallity the CHT's didnt budge a degree F warmer, but did clear off any lead deposits on the spark plugs.

But 17,000hrs on the fleet so far and not a single crack. Most interesting was watching the CHT's cool on a normal approach, only to climb rapidly on taxi back to the parking area.

Jabawocky

14th Oct 2011, 07:29

nomorecatering

Are you sure you are getting CHT's that low? Just had a look at the data from a few flights and on descent and landing they don't get much below 280-290F.

190F is 87 degrees C

Are IO360 cylinders built differently to IO550..........Yep You betcha :ok:

Now if you were to be really honest here, the Lycoming IO360 to IO540 are basically built the same. I dare say some are identical. the TCM IO550 is a different animal and from what I read the TCM product is somewhat hit and miss in assembly quality, and has been for a number of years now.

Unfortunately, as I'm not the boss, I have to conform to the SOPs, lest i want an invite for tea n bikkies with the boss.
how about you invite him in for tea and bikkies and educate him...let us know how that goes.

but did clear off any lead deposits on the spark plugs.
Leaned properly this should not be a problem :=

nomorecatering

14th Oct 2011, 07:46

Jabba,

Ive got the CHT's recorded on the vid on my phone, I saw it the first time, so repeated it while videoing. Yep down to 195F, was a fairly long PFL.

It was raised in a staff meeting about ops on the Seminole and Arrow, a while back, I suggested a change to the ops manual to make it only RPM changed on the initial power reduction after TO.

I was politely, but firmly told to stick to teaching what was in "the book".

Horatio Leafblower

14th Oct 2011, 11:42

That’s why the need to ‘cool the turbo’ before shutting down is an OWT.

I wonder if it's less to do with heat and more to do with oil.

If your turbo is still spinning at 22,000 rpm (regardless of temp) and you shut off the engine (ie: shut off the oil circulation) I wonder if that would cause accelerated wear in the turbo's bearings?

Time for bed before we wonder too much.

Jamair

14th Oct 2011, 12:01

Horatio - hows the mighty 421 going?

The turbo is not spinning at 22000 rpm on shut-down; once the over-ambient pressure boost of turbocharging is removed, typically during the descent, the turbo speed winds down. On the ground, if you're not holding high power settings for some reason, then the turbo isn't doing much at all.

jas24zzk

14th Oct 2011, 12:36

Horatio!!! long time no see no post! WB!!! :ok:

Turbo at taxi RPM probably would be barely rotating. Once you shut down, it isn't going to rotate at all.

The argument could be presented that, even after shutdown it may spin for 5-10 seconds with no oil pressure, hence risking the bearings.

That probably comes under an OWT, as the turbo has not run dry. Even though the engine is no longer pumping oil, the turbo still has the resident oil for lubrication as the impellor winds down, that resident oil is not going to be pumped away. You are in a situation where the turbo is no longer having heat pumped into it from the exhaust. Although the oil will increase in temperature due heat soak, by the time it becomes possibly critical the turbo impellor RPM will be zero, hence no damage is possible to the bearings. Seals may be another matter.

I did write a lengty reply earlier on turbo timers and the like...if you can't find it, let me know and I will find it for you..........i didn't get any objections to my comments there.

Cheers
Jas

jas24zzk

14th Oct 2011, 12:49

Quote:
Have I missed something? are IO360 cylinders built differently to IO550, are they built with more meat in light of the "training environment" they live.

....

Unfortunately, data suggests that the US has forgotten how to build 520/550 TCM engine cylinders properly. Not a problem with design: more a problem with (recent) manufacturing.

Actually 50% correct.

Friend of mine recently (early this year........make it begining late last year) had his TCM rebuilt. The biggest delay was caused by TCM finally being brought out by a shareholder

His biggest problem was that the new owner basically stopped 'production' whilst they did a stock take of every element of the business.

TCM is now owned and controlled by chinese interests. Whether the quality drop is from managerial decisions, or simply the company trying to clear the back log. I'm going to take the optimust approach and blame the latter, So i'd be expecting an improvements from what has come out in not so distant past months.

Cheers
Jas

Jabawocky

14th Oct 2011, 13:09

jas24zzk

14th Oct 2011, 13:19

Have I missed something? are IO360 cylinders built differently to IO550, are they built with more meat in light of the "training environment" they live

Couple of ways to approach this.
My initial thoughts were similar to what you presented. I.e Bigger engine= beefier cylinder walls.

dunno about anyone else, but my observations over the years have been that the bigger the total displacement, the more worried the owners seem to become about shock cooling.

So thinking about what you had to say i thought about it. The whole issue with shock cooling as you present is based on the theory that the bigger the displacement, then the thicker the cylinder walls. This made good sense to me until in considered what i know about aluminium. For expansion/contraction aluminium is best kept as thin as possible to carry the loads.

So lets look at in some numbers

IO360 4 cylinders of 90 cubes each
IO540 6 cylinders of 90 cubes each
I0550 6 cylinders of 91.66 cubes each

So essentially, the IO540 really is just as 360 with 2 cylinders tacked on. Why would the designers increase the wall thickness of the cylinder? Really, it is going to have the same size bang inside.

The IO550 on the other hand might have slightly thicker walls, but not so much as to really create a metalurgy problem. We are probably talking about 10 thou max difference here.

So where is the real problem?

The way I see it, is not so much shock cooling, but uneven cooling. The more cylinders you add, the further away from fresh air the rear cylinders are. So they are hotter, always going to be, unless you alter the way we design our cowls and introduce some more air from somewhere.

Some one made the comment about temps actually rising during taxi. That is something i would expect given the airflow situation. Jaba love his digital engine monitoring, and this is one place i can see it being put into good use. being able watch, and if designers give us the tools (ie, inbound cowl flaps) then it is something we can deal with.....get those cyl temps roughly even before shut down.

After shut down you will always get a temp rise due heat soak. But it is an even thing, so nothing to worry about.

NOW!!!
before you all FLAME me.
These are only my thoughts, if you have proof to share with me to redirect me in the correct direction, then please share...I have a licence to learn!

I am happy to stand corrected.

Cheers big ears

Jas

PS...i see you are hiding from me jaba (tears)

jas24zzk

14th Oct 2011, 13:24

Lets get this closer to 100% correct hey, the less than ideal manufacturing issues have been going on for 10 years or more. It has nothing to do with "recent" events. Whether things change...thats a 50/50 guess.

I was trying to be polite to the new owners. They have a big job ahead of them.....As much as I hate chinese 'engineering' I do know that when they want to, they are capable of matching the 'best in the world'.

same old 'money talks'

Jabawocky

14th Oct 2011, 21:54

Clinton

I have the answer for your. Rather than turn this into an advertorial and every man and his dog pluggingbtheirnlocal engine shop, PM me and I will point you in a direction a long way from here but closer to you.

Closest thing to George's gami workshop you will find in Oz :ok:

T28D

14th Oct 2011, 23:01

A couple of simple facts at idle there is not enough exhaust pressure/flow to turn the turbo, therefore as one taxi's to parking the turbo is run down !!! The turbo rotor needs reasonable gas flow to energise and turn its mass even though it is on classy bearings.

There is more damage likely from shock cooling caused by introducing large lumps of cold fuel into the tops of the cylinders by going full rich in a swift and decisive push up of the mixtures in descent.

The amount of energy the engine is using at idle is unlikely to raise the CHT to anywhere near unacceptable limits.

Engine life depends on the way thermal shifts in the engine are managed, an engine properly libricated and operated at constant temps will outlast an engine that is constantly changing thermal state through power settings, mixture changes, airspeed/attitude changes, which is why private owners make TBO and better and flying schools and aerobatic players are more likely to have issues.

Trent 972

14th Oct 2011, 23:02

Further to Clintons OWT
That’s why the need to ‘cool the turbo’ before shutting down is an OWT
Not according to Kelly Aerospace, probably one of the preeminent knowledge sources on aircraft engine turbocharging, who have republished this article 'Boosting Your Knowledge of Turbocharging' (http://www.kellyaerospace.com/articles/Turbocharging.pdf) (185KB) on their website.
A preventative maintenance procedure that should be practiced universally is to allow the engine to sufficiently warm up before applying full power, and to avoid pulling power abruptly. It’s also advisable to allow the engine to idle an additional three to five minutes prior to shutting it down. This allows the turbo to cool down and equalize temperatures before going to idle cut-off. These simple measures will reduce the possibility of oil residue coking in the hot turbine housing and should prolong the life of the turbo.

MakeItHappenCaptain

15th Oct 2011, 00:29

Hope you're not advocating shutdown ASAP?
The turbo is spinning at very high rpm and is lubricated by????

Engine oil.

Take away that lubrication too soon (ie. while it's still carrying 10,000 rpm) and see how long it lasts.:E

T28D

15th Oct 2011, 00:36

Clinton, WHY

slows down and starts taxiing, the turbo heats up. If the aircraft stops taxiing and the engines are kept idling, the turbo gets even hotter.

Aerozepplin

15th Oct 2011, 01:42

Cars and trucks don't often spend several minutes at low power settings and high speed at the end of their trip like aircraft do however.

Has anyone ever measured turbo RPM and temperature vs phase of flight in an aircraft? I've never seen a conclusive answer to the turbo cool-down debate (one backed up by data that is), but I might not have looked hard enough.

T28D

15th Oct 2011, 03:06

Zep, I can tell you the turbo's on my TSIO 520 glow red at night in the cruise, quite disconcerting given their proximity to the main spar.

But as soon as the first power reduction to slow the Air Craft they stop the glow and cool very quickly.

Inlet temp to them is the EGT at around 1400 f depending on leaning, OAT, Altitude and cruise power setting, fuel flow generally 65 lph.

Enough info ????

Trent 972

15th Oct 2011, 05:01

Somehow I just don't think you 'get it' Clinton.
But it ain't getting any cooler
Engine oil is used for turbocharger bearing lubrication and COOLING.
It needs oil passing over the bearings to reduce the temperature, the oil is then cooled in the oil cooler.
It is the turbo bearings and shaft that need to be cooled to minimise coking!

Trent 972

15th Oct 2011, 06:29

The RPM of the turbo is zero at the start of the 'cooling' period, and zero at the end. The temperature of the turbo is determined primarily by the slowly increasing temperature of the engine to which it's bolted, exacerbated by zero air flow through the cowls.

You Sir, are the Old Wife spreading the Tale.
Enjoy your bliss courtesy of your ignorance.
I'll not bother with your pearls of wisdom from hereon. GoodBye.
Ignore button - click

nomorecatering

15th Oct 2011, 06:47

Are pre-oilers of any value in reducing the wear on start up?

Back Seat Driver

15th Oct 2011, 09:07

John Deakin - Pelican Perch. Very clever, intelligent and insightful commentator, mixed with a fair modicum of emotive and dubious anecdotes and nonsense .
Read his spray on the Whyalla report (http://www.avweb.com/news/pelican/182152-1.html).
CASA got it wrong, Lycoming don't know what they're talking about, Continental don't understand their own engines and the FAA is lost in space.
Reminds me of revivalist pastor selling enlightenment to the one true religion.
A lot of what he says is good, and a lot of it is rubbish. Problem is trying to work out which one is which.

Tankengine

15th Oct 2011, 09:08

STABLISATION of temperatures is as important as total temperature. Hot spots need to be reduced. Overcooling will stuff an engine quicker than quick heating!:ugh: Oil temp is part of the problem as well as turbo RPM.

T28D

15th Oct 2011, 09:23

Oil temp , now that is a real red herring, the oil temp in my T28 stays at 70 C long after shutdown, in fact I use the temp to pump the oil back out of the sump to the oil tank 30 minutes after shut down.

Anyone who thinks Deakin is some sort of aviation engine witch is not someone I would let fly any of my aircraft, he is really one of the true guru's and was quite correct in the case of the Whyalla Accident as the ATSB finally recognised in the amended report.

Jabawocky

15th Oct 2011, 10:15

ohhh dear.........hear I go again, agreeing 100% with T28D :ok:

I flew in a Lancair IV today Turbo IO-550 330HP, owner needs a dose of JD too, just old instructors from 20 years ago I guess. He will start seeing the light ;)

A lot of what he says is good, and a lot of it is rubbish. Problem is trying to work out which one is which. BSD........you are kidding me right:rolleyes:

So mr guru, start with a really good list of where JD gets it so wrong, I can't wait.

That statement sounds like the sort you get from people who have never built engines, run them on Dyno's nor run them with all cylinder monitors and played around experimenting. As an engineer, who has done a fair bit of all of the above, i may not be a George Brayly, as much as I wish I knew even what he has forgotten, but I can sure tell you everything these guys talk about I have proven.

So spill ya guts buddy, I am keen to be enlightened.

J:ok:

Al Fentanyl

15th Oct 2011, 10:43

Check back to Post #69, covers all these issues. Starting to suspect that PA38 Captain may be here under another username......:hmm:

Tankengine

15th Oct 2011, 10:47

T28,
your oil temp stays at 70C?

I reckon your oil temp sender is near the oil tank, IN the turbo while it is glowing red the oil will be much hotter. That is why a slow cooldown [not a really long idle period] is needed to allow some time for temps [turbo, cylinder, crankcase, oil] to stabilise.

Yep, 30 mins after stopping the oil will still be quite warm.

Engines like being heated and cooled - slowly. [but I am sure I am preaching to the converted]

MakeItHappenCaptain

15th Oct 2011, 11:12

So once again, Clinton, are you advocating immediate shutdowns, according to your understanding of the objective data?:confused:

Back Seat Driver

15th Oct 2011, 11:46

Dear Guru Jabawocky, I am really not fussed about your engine prowess, good luck to you.
Personally I have enjoyed reading most of JD's Pelican's Perch.
A couple of quickies for you though GJ, quoting JD
There is also the perception that running a tank dry scares passengers. Maybe, but I don't think so. I've done it many times with all types of passengers watching… DOH
A bit like when he forgot to dangle the 747 dunlops into LA. DOH x2
No JD there's not just 2 types of pilots, there's 3. There is also those that never have and never will.
WhyallaIn my opinion, the primary cause of this accident was CASA's failure to require, and the operator's failure to install and use, proper engine instruments that monitor the EGT and CHT of ALL cylinders, as the JPI EDM-700 and 800 do.
Getting a bit emotive with that one too. For better or worse the aircraft was fitted with the instruments that it was fitted with.
He's a clever cookie, but I doubt he's the mesiah.
I'm sure you could care for as little of what I think as I do for you, but you did ask. :ok:

Jabawocky

15th Oct 2011, 12:12

Well I am sure there will be a whole heap of comments on these but I'll bite first.

1. Running the tank dry.....no big deal.......I can get accrurate data to change tanks when about 2 litres is left, but if you want to know you squeezed every drop out of a tank, why not. heck if you do not want to no biggie either.

If thats your biggest beef....ohh dear!

2. Forgetting to dangle thy dunlops, well he is a big enough man to tell the story and write about it in public, but lets get the facts straight.....he did not guts it did he.....went through a scan of things and got back on top of his game. Are you casting the first stone?:E

3. Whyalla prang...... if you read all the reports and thought about it objectively, you can see his comments about the ATSB report and more importantly how the operator ran those engines, you might give Deakin and Brayly a bit more credit.

4. Actually I care a whole heap more than you think. I am still amazed, is this the best you can find?

PS: If you have read all JD's articles you will also note that some written over 10 years back have had updates inserted and noted as over the following years, mainly through GB's test stand and the APS development they all learned a few finer points in a few areas. I am sure you will have seen these. Its all in the test data, and it is amazing how they can convince my data logs to look like they say they would. Poured over 10 hours of data log tonight, just to be sure ;)

MIHC
Did you read Jamairs post #69. Happened to be flying behind a Turbo 550 today....what happens with that machine, even discussed this with the owner.....as per post #69 :ok:

PLovett

15th Oct 2011, 12:56

Actually, BSD, if you had read the article about dangling the Dunlops properly, if at all, you would have realised that the approach was at San Francisco.

There is also another factor that you need to realise about the Whyalla crash. Since the PA31-350 was released, with its POH that recommended leaning in climb, there has been an octane rating change in the fuel. If you follow the POH there is a very good chance you will have several cylinders in detonation. However, the POH was never changed despite this change. I wonder how many operators still lean?

There is something like $70k a piece on a PA31 wing that gobbles Avgas like its going out of style. It amazes me that the majority of owners don't fit all-cylinder monitors and GAMI injectors. Their maintenance costs and running expenses would be so much lower as to cover the installation costs time over time. The only downside is having to educate the pilots being turned out mouthing OWT about engine management. Perhaps its all too hard for some to understand, the generation that just wants to be told the figures where to run the engine day in and day out despite varying mission profiles and environment.

LeadSled

15th Oct 2011, 14:32

there has been an octane rating change in the fuel.

PLovett,
Would you care to elucidate on that one. The ASTM standard has not changed as far as octane is concerned for 100/130. 115/145 ceased to be available years ago.

100LL has less TEL in it now, but with higher octane base stock, the effective octane is the same, even though we have sadly lost some of the be benefits of higher TEL fraction.

CASA got it wrong, Lycoming don't know what they're talking aboutBack Seat

Actually, you left out ATSB, otherwise a fairly accurate summary. Have you actually read the Coroners report??

A number of claims in the original ATSB report were chemical and physical impossibilities.

What some of you dim sods don't seem to realise is that running "high RPM, low boost" as the norm is all a bit new, and the suggestion that you wouldn't run an engine "low RPM, high boost" would really raise an eyebrow from those who learned their trade when big pistons ruled the roost.

It is interesting to read a Lycoming engine manual from the '50's/60's, (or Continental) versus "newer" editions, to realise that even the manufacturers are short on "corporate memory", and the lawyers reign supreme.

Sadly, the most common method of leaning I hear around clubs and schools actually maximizes the threat of detonation.

Tootle pip!!

Back Seat Driver

15th Oct 2011, 21:28

PLovett, I apologise as you are correct SFO it was for the event mentioned. Perhaps I got it wrong because when I read things like
Passing about 1,300 feet, I glanced around the cockpit: All was well, right side showed the same thing as the left, guy in the right seat was awake, gear handle was off, speed brakes/spoilers were armed ... yup, all set. Watching my instruments, I got a funny little feeling. Gear handle off? Off? Why is it OFF? It's not supposed to be off, it's supposed to be Down. It felt like someone dumped a bucket of ice water down my back. I had forgotten the gear, and the landing checklist!
AH no JD, you've forgotten 'Landing Flaps' as well or the gear warning horn would be screaming its head off.
The only points I'll give myself that night are that I didn't flinch, or look. I just said very quietly, "Gear down, please, and landing check."
Take a few more points off JD because you still don't have Landing Flaps.
. Four men simultaneously sucked in their breath. And four men watched as the gear handle went down, the green lights came on, and red light went off as the doors closed. I called for the final flaps, the checklist was completed passing 1,000 feet, and the landing was uneventful.
OK now we have the Landing Flap, that's when you do the landing checklist.
What about all the safety devices? Landing gear warning horn? Well, cargo airplanes are often very heavy on landing -- 200,000 pounds or more heavier than passenger flights. Normally, the thrust levers can be reduced to idle when the wheels are still 50 feet off the runway, but with that much extra weight, the 747 tends to crunch the landing if you do that, so most of us kept some thrust until well into the flare. I would have done that, that night, and the warning horn would have been too late to do anything about it. OFTEN 200,000lbs heavier? It's possible. Anyone who's flown a 747 knows about inertia and how the 747 handles at extremes of weight. I personally have found the opposite of what JD says to be the case re inertia, but then I don't profess to have all the answers.
Did he say? I would have done that, that night, and the warning horn would have been too late to do anything about it.
Well JD the gear warning horn would have come on when the flaps extended beyond (memory is fading here) 23 degrees??? and there is nothing you could have done to silence it.
All this is a long winded way of getting around to say that (just like Geoffrey Thomas's reports on the Qantas PIA's of late) the good parts of the message get lost when you know parts of the story are bullsh!t.

Jabawocky

15th Oct 2011, 21:39

Leads led :ok:

Sadly, the most common method of leaning I hear around clubs and schools actually maximizes the threat of detonation.

You can say that again!

And as for leaning the chieftain engines, it's not that complex or hard once you have a small amount of knowledge. Unfortunately very few if any CPL students get any.

Triple Captain

15th Oct 2011, 22:09

Whyalla
Quote:
In my opinion, the primary cause of this accident was CASA's failure to require, and the operator's failure to install and use, proper engine instruments that monitor the EGT and CHT of ALL cylinders, as the JPI EDM-700 and 800 do.
Getting a bit emotive with that one too. For better or worse the aircraft was fitted with the instruments that it was fitted with.

You're joking right? Have you seen how inaccurate the old analog gauges are?

The Whyalla report noted that the company climb power setting and fuel flow. Consider what would be happening to the engine if the old FF gauges (which really arn't fuel flow) were slightly over reading as well. Id say 100/L /engine at climb is no where near enough FF.

T28D

15th Oct 2011, 22:50

The Wyhalla aircragft had Shadin Fuel flow system fitted as I recall, very accurate digital system.

jas24zzk

15th Oct 2011, 23:04

Turbo cool down periods?

Really?
no
SERIOUSLY!!...

So lets examine your 'cool down'
You taxi in. Come to a stop and set 1000 RPM and wait 3-5 minutes, then shut down. Are you bothering to monitor your engine instruments and watch what is happening? Nope, most do this without any thought, and are too busy gathering up all their maps, putting headsets in bags etc and preparing to depart the aeroplane.

Lets examine 'immediate shutdown'
You land, and taxi back to your parking bay. Normally what 800-1000 RPM. ?? any more than that and your going to ride the brakes. So your trip back to parking takes what 3-5 minutes?

So please tell me, how much cooler the turbo is going to be if i taxi in and wait another couple of minutes at 1000 RPM????

Cheers
Jas

Trent 972

16th Oct 2011, 01:49

Jas, why don't you call the agents for Honeywell and Garrett turbochargers and ask them?

Kelly Aerospace Power Systems
1404 E. South Blvd.
Montgomery, AL 36116
(334) 286-8551
(334) 286-1992 Fax
For my area of interest in turbochargers (Rajay), they say this
Allowing a cooling down period for the turbo is a maintenance procedure that should be universally practiced. When taxiing in, allow the engine an additional two minutes of idle time before going to ICO. This simple practice will prevent any oil residue from coking in the hot turbine housing and will prolong the life of the turbo. as
Reprinted with permission from (http://www.dotheton.com/downloads/RAJAY%20Article.pdf)Aircraft Maintenance Technology (http://www.dotheton.com/downloads/RAJAY%20Article.pdf), October 1997. (http://www.dotheton.com/downloads/RAJAY%20Article.pdf)
I think I'll stick with that rather than the advice of the savants of an anonymous internet bulletin board.

T28D

16th Oct 2011, 02:46

Thankfully the savants seem to have more experience on blown enjine handling than one named after a RR hair dryer.

The taxi is more than enough to stabilise temp and clear oil after a well planned minimum power approach by an experienced pilot who can do it without wild power gyrations, by the time one is at the bay the engine (s) will have been cooling gradually for some 8 minutes in the descent/approach/ taxi.

More than enough "turbo run down time" by any standard.

Perhaps one should read the Garrett treatise on turbo handling for ALL internal combustion engines.

??? should we let the TPE 331 idle for 2 minutes after on blocks as well, it has oil and bearings, personally I shut them down ASAP less noise for the ground people and saves fuel, BTW it doesn't hurt the engine.

jas24zzk

16th Oct 2011, 03:41

Darling trent :p

Allowing a cooling down period for the turbo is a maintenance procedure that should be universally practiced. When taxiing in, allow the engine an additional two minutes of idle time before going to ICO.

What a wonderfully written piece of advice this is... An additional 2 mintues to the taxi time. HOW long was the taxi time? is it 5 minutes? 2 minutes?

Lets see. YCEM rwy 17. 3 minutes to taxi to parking + 2 minutes 'cool down' yep that works.

YCEM rwy 35. 30 seconds to taxi to parking +2 minutes 'cool down' I can see how well that fits into rayjay's explanation :ugh::ugh::ugh::ugh::ugh:

YMMB rwy 13. about 8 minutes to taxi back....do you really need the extra 2 minutes?

This simple practice will prevent any oil residue from coking in the hot turbine housing and will prolong the life of the turbo.

What oil residue? ah you mean the oil that is getting past the oil rings and being blown into the turbo via the exhaust. hmm So we are worried about that sticking to the gizzards. Well in that case we are better off having the turbo hot as hell so it can burn off. The longer we run the thing at low power, the more 'residue' can enter the gizards, and being cool, it is going to stick.

Sitting between the hairdryers as you do, you'd be more aware than us mere plebs on how fast temperatures stabilise. Once stabilised, it ain't going to get any cooler running it for an extra 2 minutes or full hour.

You miss the whole fact, that I am not saying immediate shut down is acceptable. I am saying that after a reasonable taxi time, the turbo WILL be cool enough for shutdown upon parking. I.e ycem's rwy 35 would see me run the engine for probably 2 minutes before shutdown because I thought about it.

Jas

T28D

16th Oct 2011, 05:57

Jas, He doesn't get it, flight sim doesn't have taxi time.

Tankengine

16th Oct 2011, 06:07

It is the same with most Jets, 3mins cooldown at idle to stabilise - usually covered by taxi in, if not then slowdown taxi or short time stopped.:ok:
[clock started after coming out of full reverse - idle reverse shortens the time by adding all the roll-out time!]:rolleyes:

T28D

16th Oct 2011, 09:01

Tank Engine, Quite right the taxi time will always do it, temps stable.

Jabawocky

16th Oct 2011, 09:10

OK.......time for some thread drift :ugh:....... let a few of you cool your Turbo's down for a 2-3 minutes!

Who says you can't run a Carby Fixed Pitch plane LOP?

http://i849.photobucket.com/albums/ab58/jaba430/IMG_0630.jpg

Now this is one of several trials of different settings, and this was taken just after TOC, the CHT's started rolling back, and yes CHT3&4 are a bit high, some tweaking to baffles and things need to be done, and the TAS had not settled from a few bumps, but check out the details.

The TAS stabilised at around 150, the fuel flow was around 29 LPH, the cylinder spread was was pretty good.

PLEASE IGNORE the fact the EMS thought we were operating ROP, I had been playing around with different settings and it thought we were ROP, I had to drive it well rich again and lean back again to get that to change. 29lph is definately LOP.

No Turbo's today, that was yesterday and it seemed to attract hail storms :hmm:

Brian Abraham

16th Oct 2011, 11:14

Interestingly, the Cessna 404 manual says,

After extended periods of ground engine operation above 1600 RPM or when the cylinder head temperature indicator shows values within the upper half of the green arc, reduce power to between 600 and 800 RPM for a period of not less than 2 to 3 minutes prior to engine shutdown. This procedure is intended to reduce internal turbocharger temperatures and preclude the possibility of premature accumulation of carbon on the turbine shaft seals.As said the taxi in would cover it, thought the ground run part of interest though. If I recall correctly the turbo Bell 47 helo required 5 minutes after landing.

T28D

16th Oct 2011, 11:36

Jaba Who says you can't run a Carby Fixed Pitch plane LOP?

Nobody who knows what they are doing, and I note you have run out of MAP at 8500 ft interesting cylinder numbering , 2 number 3.

ForkTailedDrKiller

16th Oct 2011, 11:37

The owner/operator of the C402 that I used to fly told me during endorsement training, "Run them at idle or just what you need to taxi for 3 minutes after touchdown - so I did!

He let me fly his very nice executive config C402 - and I did as I was told. Simple!

Dr :8

jas24zzk

16th Oct 2011, 11:41

Jas, He doesn't get it, flight sim doesn't have taxi time.

Thanx for that T28. Nice to know that what I am saying makes plausible sense to someone. However I am not going to go so far as to suggest that he is an FS pilot. Probably one that flew turbo pistons a long time ago on OWT's, and has since forgotten to look at whats being offered objectionally.
I've made a couple of posts on turbo cooling through this thread, and I only hope he goes back and reads them with an open mind.

3 weeks ago I might have agreed on the cool down time. Since being pointed in different directions by a plethora of people here (no names because i will forget one) I have learnt a lot.

Even when i have disagreed, I have at least gone and looked at the data and used my head to think about it!!

Fanboy.............777 jockey........... you presented an article that is 14 years old. go ask the author to re-write it with stats and figures that they know today......you might be surprised.

Jas

jas24zzk

16th Oct 2011, 11:51

Jaba Who says you can't run a Carby Fixed Pitch plane LOP?

Flight instructors :D

TBH, i normally run ROP (best power) as the money making muppets who control the prices I pay (do NOT get me started on that hobby horse) want me to pay VDO wet. So i am gunna squeeze every extra knot i can out of it, and f*ck your fuel bill..........i am now only interested in my bill.

Give it to me on airswitch, i'll run it LOP and even peruse the AFM inflight to squeeze every MPG out of it i can.

MakeItHappenCaptain

16th Oct 2011, 12:58

Jaba and Clinton,

Just asking a question.

Yet to work for a single PA-31 or C400 series operator (there's that commercial vs private operator thing again) who would accept an immediate shutdown (taxi time notwithstanding) without telling the pilot to find a new job.

Any commercial operators out there seen otherwise?:confused:

Jas:
The only stipulation I would suggest for LOP operations would be make sure you are using a multiple-point egt/cht system. :ok:

mcgrath50

16th Oct 2011, 13:43

Further to MIHC's post, is LOP/Oversquare operations used often in the charter mobs around the place? Or is this the domain of those unprofessional PPLs who don't bother knowing the important details about their plane? :E

MakeItHappenCaptain

16th Oct 2011, 13:54

Don't get me wrong McGrath, LOP is a perfectly valid mode of operation and is actually factory spec procedure on several a/c such as the Piper Malibu (50F LOP). From memory, Deakin strongly promotes this kind of operation for Contis in conjunction with Gami injectors; much kinder to CHTs on the lean side of the egt peak.

Likewise with over square. If a manual specifies power settings, they aren't going to hurt the engine. If an operator specifies a power setting to be used in an ops manual, it is unlikely to be detrimental to the engine. If it happens not to be the most efficient way of running the engine, you aren't paying the fuel bill.:ok:

Aerozepplin

16th Oct 2011, 21:55

I spoke to a Queenstown NZ pilot a while ago who flew 206s and 207s. When he said they flew them LOP my eyes almost feel out.

T28D

16th Oct 2011, 22:49

All this thread drift whilst educational is really dodging the real bogey which in my view is a lack of understanding of the management of piston engines around detonation.

Lots of talk re leaning and oversquare without really bringing the relationship between the amount of fuel in the cylinder/ the pressure it is fed in at/ the RPM of the engine ( load ) /the tempreture of the top of the cylinder.

In talking to younger newbies I sense that the OWT re: detonation are well and truly entrenched in the Grade 3 instructor ranks and being passed on to all newbies as if a cobra were in their flight bag.

No real attempt to understand how the engine delivers efficient power, more a real "keep away from this" as a reference to the engine allegedly melting down before their eyes.

Jamair

17th Oct 2011, 00:58

'MakeItHappen' - Skytrans in Cairns was for several years the largest 404 operator in Oz, with 10 404s, 6 310s, 3 Bongos, a SKA and a Dash 8.

Almost without exception, their GTSIO 520s lasted through to TBO. The exceptions were a couple of cylinder failures said to be due to a batch of dodgy base bolts.

In those pre-JPI / EDM days, power was set well RoP via fuel flows with quite accurate FF gauges - full for max power or takeoff, 160pph/side for climb, 110pph/side for cruise. The handling notes and Ops Man state that once power is reduced in the descent, during the approach power can be adjusted freely between 17" to 25" without having any impact on engine temps.

The notes also add that once at these low power settings, this time is included in the 'cool-down' period required in the AFM. For practical purposes given that any approach was at least 10 minutes of low power flying, this meant that unless there was a go-around, a missed approach or OEI ops, then the approach, landing and taxi (which was at 800RPM unless the electric aircon was on, which required 1000RPM) constituted more than sufficient cooling time and once the aircraft finished taxying it was shut down immediately.

Having watched a new TIO540 undergoing test runs on a rig with the exhaust end of the turbo open, I can also state that low power ops do not come close to spinning up the turbine.

As has been said already, if you are paying for the maintenance, you might want to consider these concepts. If you're working for an operator, do it their way. Maybe you could have a conversation with them about it.

Trent 972

17th Oct 2011, 02:20

For the record, it wasn't me who deleted my last post. The Mods, I guess. :ouch:
(Perhaps I shouldn't have addressed T28D by his christian name)
and Clinton if you're talking to me, ????
This message is hidden because Clinton McKenzie is on your ignore list.

Avgas172

17th Oct 2011, 02:52

So i am gunna squeeze every extra knot i can out of it, and f*ck your fuel bill..........i am now only interested in my bill.

Lovely concept Jas, I'm hoping you never have the pleasure of using one of my aircraft .... may your wings fall off in the turbulence one day while you are charging across the sky in your ignorant bliss. :ugh:

jas24zzk

17th Oct 2011, 03:03

LOL avgas,

Squeezing every knot= ROP correct :)

Sure, i will slow down to turb penetration speed if it calls for it, coz i don't fancy flight without wings.....

But owners/operators who want to charge MAX dollars, bumping up the price simply because (reason removed), then want you to pay through your arse for an aeroplane that the comm's are dodgy, the half the knobs are missing off the transponder, the GPS database is 5 years out of date, the ADF still points 90 degrees away from the NDB (6 months after you wrote it up), half the trims are coming off, the thing stinks like a mouldy apple because it leaks like a bottomless bucket..........................need I go on?

Its apples for apples isn't it.
Show the client you respect your machine by investing some of that price gouging, and your client will show due dilligence in operating it.

Cheers
Jas

Avgas172

17th Oct 2011, 03:18

Hi Jas, Yeh I was probably a tad harsh in my approach, however (as a previous thread on costs shows) it's not all beer & skittles for the aircraft operator either,
so may your wings be structurally sound & your beer cold at the end of the day.
cheers :E
A172

jas24zzk

17th Oct 2011, 03:24

No probs,
i'm just a dumb :mad: panel beater, so i can be a bit dumb in how i present things :p

It just drives me mad when the owner of a POS thinks he can charge the same as joe up the road, who has impeccable aeroplanes. They really do wonder why people don't want to use them, and treat them like junk when they do.

I still recall the owners surprise after returning his aeroplane after a 2 week trip to the centre, I came back the next day and fully cleaned it. Back to the way it was the day I collected it....

anyway....BOT

Trent 972

17th Oct 2011, 03:36

Awww come on mods. Please put the 2nd last line of my deleted post back. Jas just confirmed it with his last few posts. Hahahaha.

ForkTailedDrKiller

17th Oct 2011, 08:26

Awww come on mods. Please put the 2nd last line of my deleted post back.

Better still - out with the lock!

Dr :8

Nivo

17th Oct 2011, 11:02

Continuing Jaba's thread drift.....

Who says you can't run a Carby Fixed Pitch plane LOP?

I ran a C172 sucessfully LOP. It had a JPI700 and I had been to hear Walter and George at the APS in Sydney.

The 2 tricks I discovered were:

1. to back the throttle just off WOT (it seems to induce a little turbulence in induction air flow for more even mixing of air and fuel) and

2. a smidgen (technical term) of carby heat for the same reason.

Now back to "Over Square"

Nivo :ok:

Al Fentanyl

17th Oct 2011, 11:02

Don't get me wrong McGrath, LOP is a perfectly valid mode of operation and is actually factory spec procedure on several a/c such as the Piper Malibu (50F LOP).
The Malibu had a truly awful engine reliability history early in the piece which turned out to be operators following the POH for LoP ops at 50 LoP, then saying 'I'll just add a little extra fuel, to keep it cool' and thus moving the mixture into the worst possible place - peak EGT!:ugh:

Nivo, the other thing you do with backing the throttle just a tad off full is disable the enrichening feature - which you want to do to cruise anyway.

jas24zzk

17th Oct 2011, 11:52

Why don't you retype it and pm it to me Trent?

I'm not scared

NOTHING anyone says here will hurt my feelings(the only person to come close to that was jaba, when he thought I wasn't reading/learning). I actually look forward to being wrong, and them pointing me in to documents where i can learn something and am certainly man enough to accept the better advice.

Now to get BOT,
we have been talking about cooling periods/turbo run down times etc.

As Jamair mentioned from personal observation, at low power/taxi rpm, the turbo impellor is making ZERO revolutions. So saying that you are waiting for it to wind down is based on nothing more than an OWT.

If you are waiting for the temperature to stabilise, then most of that seems to be guesses. I and others have mentioned time and time again about low power settings being enough for the cool down...i.e temperature stabilisation.

I was thinking about that on my way home and came up with a good demonstration for you all on how quickly things cool. Keep in mind this engine, isn't being pushed inside its envelope, it is being pushed until it goes BANG (which it doesn't do...........true blue ford :ok: )
Also keep in mind this engine, whilst being watercooled, is in a controlled environment, and is not being subject to airflow to assist with cooling.

Watch the video............(warning your wife might not appreciate the turbo whistle, so watch the volume)

1000hp Ford XR6 Turbo Engine - YouTube

Cheers
Jas

Jabawocky

17th Oct 2011, 12:18

Nice video Jas :ok:...I hate being anywhere near a Dyno, worse still when I am on one in the hotseat :uhoh:.

Remember this, Horsepower isn't everything!.............it's the ONLY thing! :ok:

Ford XR6 Turbo, the only thing that blows up more than modern day QF RB211's :ouch: :E

jas24zzk

17th Oct 2011, 12:52

what a load of poppy cock!!

its ford, it's tougher than toymotor!

Horsepower is the only thing???? crap waffle and total boulder cock!

torque is the only thing............. i want to hit the house doing 100kph, with 2 tonnes of boat on the back, but i want to relocate said house 7 post codes!!!

am actually dissapointed with that video, as it isn't the one that shows how quickly it all cools when they pull the power.

Some more websearching for me.

gotta be impressed tho, that power out of that engine.............

kingRB

17th Oct 2011, 13:33

with a good demonstration for you all on how quickly things coolAll it shows is how quickly a manifold (which looks to be stainless) stops glowing. With stainless steel, thats usually pretty quickly.

The whole setup still has a massive amount of heat in it once the manifold is no longer glowing red. Well and truly enough to damage bearings and seals if shut down at that point...

gotta be impressed tho, that power out of that engine............. Not really. Nissan RB26DETT with 1.4L less displacement, designed a good 14 years before the Ford engine, upgraded with forged internals and also capable of making well in excess of 1000 HP impresses me more :E

T28D

17th Oct 2011, 21:47

Most aircraft exhaust manifolds are Inconel and a light guage to boot which heats and cools quicker than stainless.

The hot side of the turbo is cast in exotic steel but is the only cast in the system and is also quite thin so it is light.

Cast Iron just doesn't get used for aircraft, simply it is far too heavy.

kingRB

17th Oct 2011, 22:23

my bad T28, just reread what I wrote and shaking my head. Was thinking of the turbine housing when I wrote that, not the manifolds.

Thanks for the correction.

Brian Abraham

18th Oct 2011, 03:24

Having watched a new TIO540 undergoing test runs on a rig with the exhaust end of the turbo open, I can also state that low power ops do not come close to spinning up the turbine.andAs Jamair mentioned from personal observation, at low power/taxi rpm, the turbo impellor is making ZERO revolutions. So saying that you are waiting for it to wind down is based on nothing more than an OWT.
Not what Lycoming infers, unless there is some other meaning given to "operating" other than revolving
In engines that call for more than field-level manifold pressure to produce rated power, such as the TIO-540 series, the turbocharger is operating at all times when the engine is running.

aldee

18th Oct 2011, 03:52

Been thinking this through myself, even at low power / wastegate fully open inlet air is drawn through the turbo, surely this would cause it to spin?

aldee

18th Oct 2011, 04:28

Getting a bit thread drifty and all but if the wastegate is fully open all exhaust bypasses the turbo= no driven rpm
The best the bearings get is low pressure oil which is a coolant = good:ok:
The problem is we're all generalizing here, turbo installs operate under vastly different regimes

Back to the over square debate:)

T28D

18th Oct 2011, 04:29

Aldee
Been thinking this through myself, even at low power / wastegate fully open inlet air is drawn through the turbo, surely this would cause it to spin?

The cold side of the Turbo is a compressor so it is not likely to be spun by the low volumes drawn through the Turbo at idle.

The hot side which is a turbine also will not be generally spun by low exhaust volumes at Idle bearing in mind the waste gate will be open at idle, it needs oil pressure to close, as a rule of thumb you will need + 50% power being developed to get enough gas flow to really activate the turbo.

aldee

18th Oct 2011, 05:02

I'm far from the air cooled turbo engine guru being a diesel mechanic whose built and dyno'd 300 - 2500 hp engines
These suckers almost turn the turbo cranking with the starter:}

Different animals these ground dwellers

Trent 972

18th Oct 2011, 05:30

One of the drawbacks of sourcing information from the internet -
Do a google or whatever search on operating garden variety mid to large GA aircraft engines, and one of the 1st pages to come up is
Operating Tips for Big-Bore Continentals (http://www.swaircraftappraisals.com/MeyersForum/Engine%20Info/Engine%20Operation/Operating%20Tips%20for%20Big-Bore%20Continentals.htm)
You'd probably think it's good stuff, afterall the author is
Mike Busch ([email protected]) is editor-in-chief of AVweb, and teaches powerplant management courses for the Cessna Pilots Association. He is a 5,000-hour pilot and CFIA-I-ME, has been an aircraft owner for 30 years, and presently owns a 1979 Cessna T310R.

Be careful to check the small print at the bottom of the page though
This page was last updated Sunday, September 28 1997.
An interesting part of the treatise says (my bolding)
I also am a big fan of cruising at low RPMs and high MPs rather than the other way around. If your engine will run smoothly at bottom-of-the-green RPM and top-of-the-green MP, that's an excellent place to operate them for cruise. (For the TSIO-520s in my Cessna T310R, that's 30" MP at 2100 RPM, and that's exactly the setting I use at altitudes up to 13,000' or so.) If your engines don't feel smooth at bottom-of-the-green RPM, experiment to find the lowest RPM at which they do feel smooth, and cruise at that.
You may then ask, what's changed since September 28 1997?
Well for one thing, this has

TELEDYNE CONTINENTAL ® AIRCRAFT ENGINE (http://www.tcmlink.com/pdf2/CSB09-11.pdf)
CRITICAL SERVICE BULLETIN (http://www.tcmlink.com/pdf2/CSB09-11.pdf) issued 09 25 2009
COMPLIANCE NECESSARY TO MAINTAIN SAFETY
SUBJECT: MINIMUM CRUISE RPM LIMITS
PURPOSE: To inform operators of the possible long term effects of low engine RPM in cruise conditions. To establish limitation of minimum engine RPM in cruise.
COMPLIANCE Upon issuance of this bulletin
MODELSAFFECTED: O-470-G; IO-470-N; IO-520-BB, CB, MB, P; IO-550-A, B, C, D, E, F, G, L, M, N, P, R; IOF-550-B, C, D, E, F, L, N, P, R;
TSIO-520-AE, BB, BE, CE, DB, EB, JB, KB, LB, NB, UB, VB, WB; LTSIO-520AE; TSIO-550-A, B, C, E, K; TSIOF-550- J;
TSIOL-550-A, B, C ISSUED REVISED PAGE NO REVISION................
.......

Engine cruise RPM settings should be no lower than 2300 RPM.

There are some very clever people here (I think Jaba is one, and he's often happy to put up photos to show his point) but buyer beware, if you put your faith in the musings of anonymous posters on internet bulletin boards, particularly when it contravenes the OEM recommendations. After all, some of these gurus like to extoll the virtues of their wealth of knowledge for the betterment of all (but they don't put their real name out there), but if it turns out later that they weren't quite so clever, they'll probably just change their user name and start all over again.
Me, I'm going to stick with OEM recommendations, even if it costs me a little bit more in fuel and maintenance. :suspect:

Jabawocky

18th Oct 2011, 05:39

Either way, no matter which kind of forced induction you have, be it supercharged or turbocharged, by the time you have pulled the power back on final approach, landed and taxied to your parking spot, set the park brake, cancelled sar, picked your nose :ooh:, turned avionics off, and generally fiddle farted around like most pilots do, you are well past the 2-3 minutes............so shut the fokker down :ok:.

If however you come screaming it with high levels of power, use the arrestor cable that you have conveniently installed at the front of your hangar / end of the runway, and have not crashed through the back wall........yeah sit outside for a couple of minutes, and after changing your jocks :eek:, then shut it down :}.

Trent 972

18th Oct 2011, 05:50

Aww give me a break Jaba, I got out of turbo's and into oversquare, because I don't want any more pm's from Jas.:ok:
Funnily enough though, it's the power-off plunges at the rwy threshold, that bunch my jocks. :{

Jabawocky

18th Oct 2011, 05:52

Trent972

Nice post :ok:

I can't say I always agree with what Mike Busch prints either. 2100 RPM and at MP's of 30" or more would certainly move the Peak Pressure Pulse much closer to TDC. And for those who do not follow that, this is not a good thing. But just how much trouble it creates depends on the engine design and the spark timing.

I would think TCM are suggesting a nice range of RPM to operate in there at high MP, but by that quote it does not say. If it were on descent with MP reduced, 2100 should be fine. I would like to see the whole document Trent if you have a link.

J:ok:

T28D

18th Oct 2011, 05:53

Aldee, a lot of difference between a compression ignition engine and a spark ignition engine in the way induction pressures are generated and managed.

Different fuels need different handling.

Neville Nobody

18th Oct 2011, 05:59

Different fuels need different handling.

This thread needs more drift, what about rocket fuels? You need to let a rocket cool off before shutdown?

c100driver

18th Oct 2011, 07:02

I once had a C172 that a previous owner had installed a MP gauge. That machine had a static RPM of about 2240.

Shock horror the MP was just over 29" on most days according to my instructors who first taught me the "rules" of operating an aircraft with constant speed propellers that engine should have been toast!! However that machine used to fly parachute and glider tow operations and was full throttle day in day out and did well over 3000 hours.

That was when I realised my instructors didn't have a clue:ugh:

The BE76 is a classic in that the AFM has the climb power of full throttle and 2600 or 2700 RPM. However the instructors were told by the CFI that climb is 25/25 and that is what they taught. Even after I managed to demo them that if you fly it iaw the AFM the CHT would comfortably sit at 380 degrees. At 25/25 the CHT was just over 460.

I have never heard of anyone not having the confidence to run a fixed pitch aircraft at full throttle (without knowing it being oversquare!!!!!)

jas24zzk

18th Oct 2011, 07:16

Aww give me a break Jaba, I got out of turbo's and into oversquare, because I don't want any more pm's from Jas.

but but but, my mail had nothing to do with turbo's :uhoh:

and you never replied :eek: I'm devastated, i really am a SNAG you know.

Jabawocky

18th Oct 2011, 08:08

Did someone edit my last post for me? :confused:

Horatio Leafblower

18th Oct 2011, 09:04

Even after I managed to demo them that if you fly it iaw the AFM the CHT would comfortably sit at 380 degrees. At 25/25 the CHT was just over 460.

I once had a bloke ring me in a panic that the U206 he was operating was running really high CHT in the climb. Company policy was full throttle, full mixture, 2500 rpm and at that power setting it would sit at 380.

If you climbed at 25/25 like the aero club told you (never mind the CP or the Ops manual or the POH) :ugh:

43Inches

18th Oct 2011, 11:03

I always thought the 25/25 was a compromise power setting taught by flying schools for passenger comfort reasons and a little preparation for more advanced types with METO/MCP limits. Once you attain a reasonably safe altitude increase speed and reduce power to reduce noise, vibration and body angle to make a more pleasurable experience for the paying customer, a sort of cruising climb. The higher speed offsets the reduced full rich cooling being close to 75% power (normally aspirated) its pretty close to a high cruise setting.

As an instructor it did annoy me that students did not understand that this 25/25 setting was not a limitation. Full power was available in any situation if required and should be used to achieve performance targets. The amount of times a student when asked to demonstrate a max angle/rate climb set 25/25 was very dissapointing.

The whole over square thing has no merit whatsoever and does nothing for engine life if it does not accidentally match with a recomended setting anyway.

Shock cooling will have little effect on perfectly formed materials as even heating and cooling will most likely occur (as designed). Unfortunately, most aircraft parts in general these days are far from perfect, any small defects/imperfections in a high stress area will be made weaker by large, sudden variations in temperature. Over time this may accelerate a failure such as cracking etc... Continued operation of an engine outside of its normal temperature range whether hot or cold will cause more lasting damage than sudden changes within that range.

Jabawocky

18th Oct 2011, 11:14

43inches.....what an appropriate name, lots of MP there :ok:

The higher speed offsets the reduced full rich cooling being close to 75% power (normally aspirated) its pretty close to a high cruise setting.

Please sir, wipe that OWT from you memory. Full rich or richer mixture means more fuel to air ratio, your statement suggests that fuel is doing cooling. Maybe I am reading more into your words, but please understand the injested fuel does not do any cooling at all. far from it, it is the source of all heat!

J:ok:

Trent 972

18th Oct 2011, 11:39

Full rich or richer mixture means more fuel to air ratio, your statement suggests that fuel is doing cooling. Maybe I am reading more into your words, but please understand the injested fuel does not do any cooling at all. far from it, it is the source of all heat!
Jaba are you saying that unburnt fuel from an over-rich mixture does not remove some of the heat from the cylinder, as it is exhausted?
SShhhh I can hear T28D coming, I've gotta run. :)

Jabawocky

18th Oct 2011, 11:58

trent

unburnt fuel out the exhaust.....I have never seen that happen. Not once. Have you? If so please explain.

I have seen unburnt fuel drip all over the nose gear from fitting the dreaded anti theft device lock and fuel drains back out through the throttle body and air intake.:ugh:

.........leaves a nice tell tale residue.

T28 is after you hey....I gotta watch :}

jas24zzk

18th Oct 2011, 12:29

Correct me where i err please.

Fuel dictates the size of the fire....................................

LOP. Your fuel is lower, so the fire is smaller, so less heat can be generated. You are also in a zone that the oxygen levels permit total burn of the fuel.

Peak. You are burning everything max, but you are opening the door to detonation and things like that.

ROP. You are rich, so if fuel is having a cooling effect, it certainly isn't doing it at the point of measurement. ROP is a hotter temp than PEAK. What is happening? the unburnt fuel is being burnt in the exhaust, causing a rise in what the probe is seeing.

Maybe a reword on the terminology being used need be considered, or at least clarified.

These days it seems to be taught as Best Power, Best Endurance. I know jaba, t28d and trent can relate em back, but can the others.

Cheers
Jas

Trent 972

18th Oct 2011, 12:30

Jaba
Simplest description I can offer is to think of what an exhaust system 'Backfire (http://en.wikipedia.org/wiki/Back-fire)' is.
an incomplete burn which causes the fumes to explode in the exhaust system
I'm sure you've seen engine tailpipes with that dark sooty telltale on the inside of the pipe. Unburnt fuel. Much more noticeable with large diesels engines with knackered injectors, thick black smoke, not completely burnt fuel in carbon form.
Peak engine power comes at a close to 12.5 :1 air/fuel ratio, and best economy at 15.5 :1 ratio. However petrol will burn anywhere from 20 : 1 to 8 : 1. If an overly rich mixture between 12.5 : 1 to 8 :1 (which will develop less power than peak mixture 12.5:1) then unburnt fuel will travel through the OTTO cycle.
BUT, I am not my wife and therefore by definition, don't know everything. :ok:

Jas, I agree with everything except
ROP is a hotter temp than PEAK
Think EGT guage and richening the mixture from peak EGT, the EGT will decrease. That is the unburnt fuel removing heat from the cylinder.

*Where I have used the term 'unburnt fuel' please substitute 'not completely burnt fuel', to be more precise.
-------
Found another interesting article - Mixed up about fuel mixtures (http://www.amtonline.com/publication/article.jsp?pubId=1&id=1171&pageNum=1)
Using a typical air-cooled aircraft engine running at normal power, with the throttle in a fixed position, if fuel is slowly added to the stoichiometric mixture (0.067) the added fuel will have a cooling effect and the combustion gas and cylinder head temperature will decrease.