Walter Atkinson

Old Akro:

Thank you for posting that link. It's a very interesting and well done study.

In this study, Note:
1) at RPMs under 3000, no valve rotation was noted.
2) the components used to aid in this rotation are not part of the aviation engine.

We have tried to verify valve rotation via engine monitor data on a leaking valve. What we have found is that the leaking is not consistent with valve rotation as is assumed to be occurring. As I said, the jury is out, based on the data we have seen, that the valves rotate in an aviation engine at any consistent rate--if they are rotating at all. The assumption that aviation valves are rotating at higher than 15rpm as considered desirable in this study is simply not supported by the data.

There is more to study, for sure.

Old Akro

Walter

I've read a few papers on valve rotation and I thought this one was the most descriptive about the mechanism being the valve spring through the torsional rotation of the spring wire.

Since valve springs are tuned to have a natural frequency above redline to prevent valve bounce, I assumed that a valve spring designed for a low speed engine would - through either lower tension or lower natural frequency - involve valve rotation at lower speeds.

As an aside, my 1985 Alfa GTV6 gets valve bounce about 200 rpm part redine. Its an effective rev limiter and hilarious! It happens reliably if I try and eek another couple of km/h out of 3rd gear before the braking marker on the back straight at Winton.

The question is, do valve's burn because they don't rotate or do burnt valves stop rotating?

After you give me that answer, I have another question involving chickens & eggs.

Andy_RR

Humans aren't born with wings, but they still fly. There's plenty of electronic tools to help correct the foibles of humanity, but sadly no technological cure for Ludditism.

Creampuff

One of the chronic problems is that the regulator insists on recruiting ‘experts’ from the industry who then proceed to perpetuate the OWTs (folklore) they were taught, unhindered and untroubled by what the data actually show and the rules actually mean.
‘
Reforming’ the rules and administering them is merely an opportunity for these ‘experts’ to embed the folklore more deeply.

If some expert has decided that any and all cylinder damage is caused by ‘excessive leaning’, every example of cylinder damage ‘proves’ it. That ‘expert’ will of course passionately champion the cause of outlawing of ‘excessive leaning’.

Remember the good ol’ days of stomach ulcers? They were ‘caused’ by ‘spicy food’ and ‘stress’. It was ‘proved’ because every time a doctor asked someone with an ulcer: “Are you under a lot of stress or do you eat spicy foods?”, the answer was always: “Yes, as a matter fact I am. How did you know?”. And, if the person relaxed and stopped eating spicy foods the symptoms of stomach ulcer went away. That ‘proved’ the cause.

But then someone did some proper research and proper testing and found out that, in fact, stomach ulcers are usually caused by an infection with a bacterium called H. pylori. Treat the infection by killing the bacterium and – surprise, surprise – the patient could eat spicy food and endure ‘stress’, which actually meant ‘live normally’.

Almost all piston aero engines come off the production or overhaul line with an ‘ulcer’. The ulcer is an induction/fuel system that results in each cylinder reaching peak EGT at different points on the lean curve. The symptoms of this ulcer are ‘rough running’ and ‘lean misfire’ when the mixture is leaned.

One way to ‘treat’ the ulcer is to deal with the symptoms. Keep the mixture very rich – that is, avoid the lean mixture ‘spicy foods’ and ‘stress’ that ‘cause’ the ‘rough running’ and ‘lean misfire’.

However, the best way to ‘treat’ the ulcer is to deal with the cause: Fix the induction and fuel system so that each cylinder reaches peak EGT at around the same point on the lean curve. Then – surprise, surprise – the engine can then eat spicy food and endure ‘stress’ – which actually means “operate normally”.

Brian Abraham

Those who promote the LOP is bad argument need to explain why it is that certain aircraft do have it as an approved procedure in the POH. The Chieftain and Beech Baron (B58) are just two. If the procedure is bad, bad, as the luddites suggest, then they need to explain why the engine manufacturer, the aircraft manufacturer, and the FAA, and in our country, CASA, accept the procedure and attendant legal ramifications.

Answers on a postage stamp please.

Just saw your post re ulcers Creampuff and reminds one of a joke. Scotch and ice, rum and ice, gin and ice, all make you drunk. Ice is common to all, therefore ice makes you drunk.

Creampuff

Poor pet.

Amazingly, he seems quite capable of carefully constructing coherent sentences when he wants to be insulting: Or perhaps he's hired a ghost writer, Trent?

Sunfish

Apparently the new Rotax 912 iS electronic injected engine is programmed to run LOP at anything below 97% power. The ECU uses data from individual cylinder EGT's and a knock sensor as part of its decisionmaking.

No Hoper

If Trent is the Trent I know of he is on thin ice slinging off about others maintenance practices.

LeadSled

yr right,
Not only was I not that Captain, I simply do not believe the story.

Some of the smartest LAMEs I have come across were to be found on Qantas International's outstations. Not all Qantas stations have Qantas maintenance personnel, mores the pity.

That does not change the fact that I have knocked back aircraft that were not, as far as I was concerned at the time, fit for service. That experience has not been limited to airline aircraft, some of the worst defects I have picked up, doing a daily, have been in flying school aircraft. Defects that would have been life threatening. Something that you clearly do not understand (and it is a matter of law) is the matter of the rights and responsibilities of the pilot in command. CAR 233 is very clear, if the PIC decides the aircraft is not serviceable, that is it, the MR will be endorsed, and the aircraft will not go anywhere until the PIC is satisfied.

That is the last line of defense, not the LAME.

Creampuff has detailed the law, as far as maintenance elections are concerned, that results in the log book statement. That election can be changed at any time, by the registered operator, so the log book statement is hardly the be all and end all of maintenance.

As for "engineers", as far as the AQF (whatever it is called this week) an AME/LAME has trade qualifications, which do not meet the level to be called a profession. Likewise, holding a pilots license of CPL or above does not qualify as a "professional" qualification, notwithstanding that many pilot training courses result in a Bachelor of Aviation, or something similar.

Tootle pip!!

rnuts

Trent 972
You're right. That didn't come across as intended.
You, yr right and anyone who took offence. I do apologise.

Trent 972

Good on you for being the 'Bigger Man', rnuts. Not that I was offended. I just thought it a pity if yr right was dismissed for reasons other than his arguments.
If only Creampuff could be half the man. Sadly, I find him to be a FWOTHO.

Edit.
Not me No Hoper. I'm just a driver with 19,000+hours of the same hour over and over again!
I wasn't aware that I had slung off about any maintenance practices???
Maybe you are a little confused.

No Hoper

Apologies to you Tremt, I am just sick up and fed of people playing the man on a professional site. Although as Leadsled suggests we are lillying the gild by calling ourselves such

yr right

Yes i have a learning difficulty. Do and have I said I have yes. Do I care what you think. No. Dose it make me a better engineer. Yes cause I have to work a **** load harder.
But what I have lost in some areas I more than made up for in others
Cheers

Creampuff

And I’m a wheelchair-bound, acne-stippled geek from Hicksville USA. I’m scared of flying and I don’t like getting my hands dirty.

In what way, precisely, do anyone’s handicaps affect the temperature of valves at various points on the lean curve?

In what way, precisely, do 19,000+ hours in some pilot’s logbook affect the temperature of valves at various points on the lean curve?

It’s been said before: A person without data is just another person with an unsupported opinion. That goes for everyone: People in wheelchairs, people with dyslexia and skygods with fat logbooks.

No amount of burnt valves and stuffed cylinders count for data, unless….

Unless there is objective evidence to show what burnt the valves and stuffed the cylinders.

Data collected from millions of hours of piston aero engine operations show at what mixture setting valves and CHTs on a piston aero engine are hottest. Nobody’s hours in command or years on the bench makes a schmick of difference to the validity and implications of that data.

If that hurts: Boo hoo.

Progressive

Leadsled,
For probably he first time I agree with Yr Right, in terms of maintenance the required schedule is dictated by the log book statement. The owner may elect to change the schedule of maintenance whenever he likes: however this change in schedule is not formalized until the logbook statement is amended. The 100 hourly is required to be signed of "IAW the logbook statement".

As for this statement:
As for "engineers", as far as the AQF (whatever it is called this week) an AME/LAME has trade qualifications, which do not meet the level to be called a profession. Likewise, holding a pilots license of CPL or above does not qualify as a "professional" qualification, notwithstanding that many pilot training courses result in a Bachelor of Aviation, or something similar.

LAME technically qualifies as a para-professional qualification, trade qualifications are for an AME (CERT IV) (hence the required diploma level qualification for LAME). Interestingly the Diploma in Aeroskills (LAME qual) involves more teaching hours (and thus knowledge) than any other diploma level qualification in Australia, and more than many Bachelor degrees.

Creampuff

Hi progressive.

Do you have a CAR reference for that assertion?

CAR 42ZE says:The ‘CASA system of certification of completion of maintenance’ is in Schedule 6 of the CARs. The phrase ‘log book statement’ does not appear anywhere in Schedule 6.

Schedule 6 para 4.6 says: “A person must not make a final certification (under Schedule 6) unless the person is satisfied that … (a) all maintenance required to be carried out on the aircraft has been carried out…

Those requirements are driven by the schedule of maintenance and the approved maintenance data. I realise that the LAME will usually have only the ‘log book statement’ on which to rely to determine what the schedule of maintenance for the aircraft may be, but it’s still regulatory cart, not horse.

I have no doubt what the practice is. But, like many things in aviation in Australia, the practice may merely be a perpetuation of an OWT, including by CASA.

LeadSled

Progressive,
Creampuff has dealt with the issue of the standing of the log book statement.

The above may well be true, but, interestingly, the present setup is far lower teaching hours than a number of other countries, and you may be aware of the current criticism of the product of the present system.

Likewise, it is not unusual for unskilled person or tradesmen to earn far more then "professionals".

None of that has any bearing on the industrial classification, which come from the industrial relations system.

Tootle pip!!

yr right

Difference is when we **** up will kill people and as such every time a sign a piece of paper I take full responsibility for my actions and overs under. A dr takes one out at a time we can take multiple and we get paid **** for the privilege. So tootie up yr arse sorry.
Cheers

43Inches

A doctor can kill millions if they stuff up, that's what happened before doctors were professional and epidemics such as the plague abound. If they intentionally create a bug that is resistant they could cause the deaths of millions. I think they are worth all the credit and dollars they can get considering the ethics that control the worldwide medical profession.

Every time a planes flies, ship sails, train departs a bus pulls off the corner a number of people have direct control over whether the number of individuals inside survive the day. All these vehicles have the chance of being in a position that would ensure all inside do not make it to the next day. We all do our best to make sure this does not happen.

Creampuff

Diiing … Dongggg…

Ladies and gentlemen, as you can see the LAME has switched on the ‘SEATBELT’ sign.

There is some rough looking weather ahead and the LAME is reviewing the METARs and NOTAMS, and doing some fuel calculations, to see if we can fly around it and maybe to somewhere else. The LAME’s also checking in with the air traffic control LAME.

I got my pilot’s licence from a Wheetie’s box so, like you, I can’t do much but sit back and relax and watch the last line of defence do his thang.

Thank you for flying LAME!