Agrajag

Again, no dispute.

I think, informative as this branch of the discussion is, it may have strayed from the context in which it began. Specifically, it related to whether LOP operation is a breach of a manufacturer's limitations as published in a POH. There are those who say, if it isn't specifically approved, it's therefore prohibited. The gentlemen at APS disagree and, given that this is their area of expertise, I'm inclined to believe them.

yr right

Negative ghost rider. If it's not stated and you don't have or have an stc you can't use it. It is that simple.
You cannot make your own rules.

Cheers

Ultralights

actually most engines do, and i have seen the data, and seen all types of engines run LOP.. plenty of data around on LOP ops, so much so, that i doubt anyone would be a test pilot when it comes to LOP in any aircraft..

a test pilot implying that the pilot is flying without any knowledge of what will happen when operating the aircraft in its current setup/conditions..

yr right

Um I think you are reading to much into test pilot some what.

LeadSled

yr right,
Maybe that is what you think is the case, been taught, whatever, but it is not legally true, as far as aircraft certification is concerned. However, if one has been "trained" in Australia, either as a licensed pilot or maintenance person, I can easily understand how that legal misapprehension comes about.

As mentioned previously, a POH, by whatever name, is a combination of certified data, approved/acceptable data, and selected useful information for the operation of the aircraft by suitably trained, experienced and licensed crews.

In matters of LOP, if it is not specifically prohibited, it is permitted, as LOP is a quite normal operating mode for a four cycle (Otto Cycle) piston engine, aircraft or otherwise.

Tootle pip!!

yr right

No you cannot change data from something else to some thing else. Data is specific to the aircraft and not transferable between any aircraft that the data is required for.
If I have an stc or an eo its rego and s# limited, I cant use any document to any other aircraft period unless it is on that document. If you don't have data you cant use it. so if there is no charts for LOP as an example you cant legally use it. The regs are very specific on this.
I will add here this is for aust and I will not make comment on any other country regs, I also have held o/t lic coverage and approvals.
cheers

drunk_pilot

Leadsled:

Oh really... So what happens when your aircraft POH only has performance tables for, say long range cruise leaning to peak EGT, which has a TAS and fuel flow attached to it, and some turkey decides he/she can make his/her destination in one go if he/she runs LOP based on their self derived data. How can he/she PROVE what performance they will achieve? Let's say they have an unforeseen headwind and suffer fuel exhaustion prior to their destination and have to land in tiger country. How successful do you think they'll be fronting the coroner over the death of a passenger because they extrapolated the OEM POH with their own, or anyone else's non-approved data? That's what I thought.

You quoted me out of context, Ultralights. I said IF YOU DON'T have charts for it. Read my first post a couple of pages back, if you have the charts and know what you're doing, go for it. Run LOP.

What really bothers me here, is that people are suggesting that just because the manufacturer doesn't specifically say don't do it, that you can! A little bit of knowledge is dangerous in the wrong hands, and this forum has a lot of new pilots reading, and getting ideas of stretching their dollar or range by running LOP, potentially without having any approved data or procedure in the POH to do it. You're asking for trouble saying that on here.

I'll say it ONCE more for clarity: If the POH says you can, and you know what you're doing, then go for it. But for your OWN sake, if you don't have the approved data to hang your hat on, DON'T DO IT!

Creampuff

When you set the timing to e.g. 22 degrees before top dead centre, the engine is not running. (That's why some people call it 'static' timing.)

When the engine is running the crank is moving. During the short period between the points opening and the spark occurring the crank has moved about half a dozen to a dozen degrees. It depends on RPM of course.

That's 'actual' timing.

The dyno data shows it.

And no, yr right, there are not multiple sparks out of a bog standard aero engine magneto after each points opening event. Just one spark, then some secondary 'ringing'.

yr right

Seriously leadsled before you make comment on law I suggest you know the regs first. You have made a rather large hole for your self and entered extremely dangerous territory that's not for the faint hearted.
You cannot add or subtract from the manual with out approved data. Its like saying you can do aeros in a metro cause you can do them in a pitts.
Really stop and think about what you have said.
Cheers

yr right

um points moved via a cam which is driven via shaft which has a gear attached which is driven via a gear off a gear which is attached to a crankshaft.no lost motion there !!!!!!!!!!!!

yr right

best let casa here know then cause they been teaching us all the wrong things, but hey you already knew that.

Creampuff

But when you set the magneto timing the crank isn't moving at thousands of revolutions per minute.

Why don't you just leave engine operation to the experts in engine operation?

yr right

yes I should so are you going to stop posting cause that be great
cheers

LeadSled

ye right,
OK, would you like to be very specific about the regulations, to which you refer. No generalization, very specific regulations, please.
You will quote the Australian certification standards post 1998 ie: the CASRs, of course.
Not anything that you believe may have been extant (but probably legally was not) at the time you did your apprenticeship.
I note that, in mid-1960s, I was operating VH- registered light aircraft LOP, even demonstrating the fuel savings to DCA Examiners of Airmen.

No, Its not anything like that, because the TCDS will tell me exactly what the certification base is for each aircraft, thus defining the flight envelope. Further, in the case of the Pitts, if it is certified in the Aerobatic category, the exact maneuvers permitted will be stated, if there are any maneuvers limitations. Once again, if there are no stated limitation, and maneuver physically possible is permitted, withing the limits of the design G.

Using another example, the Limitation for a B707/720 (all models) prohibited sideslips, therefor no sideslips. In contrast, sideslips ( which are NOT an aerobatic maneuver) were not mentioned in Limitations for B757/767/747/744, therefor sideslips were permitted. There was not, nor was there any legal requirement for, a specification that permitted sideslips.


Yes, we do know that, what else is new??

Tootle pip!!

Jabawocky

WOW....has this thread wound up notch

I doubt he is one of our students. We can't control what they do after a course, but we teach understanding....we avoid like the plague "cookbook recipes" because they do not work very well. By the way POH's tend to do this.

If you wish to PM me his details I can offer to help. Assuming he is a past student. Chances are I know him anyway. Even if not a past student!

Akro is correct.
yr right
Wrong again.

OK so what happens with a CS prop? The rpm does not change, but fuel flow especially with a Bendix system, is almost linear with mass air flow?

You really are getting confused here.

Yr right,
It is funny to watch you bury yourself even more. You do not know t but despite my thoughts on airspace ADSB and things being at odds with leadsled at times, he and I both know fact from fiction pretty well. It seems you unknowingly are slagging off at or refusing to be educated by several of the best heavy weights in aviation not only here but in the USA. All in this thread.

I am cocksure and ignorant at times, Leadie will attest to that, but I have nothing on you. You are blatantly disregarding thousands, maybe millions of hours of hard data produced by NACA (NASA), P&W, CW, Lycoming even validated it in the 60's, and more recently by GAMI and APS. All lock step in consistent data. The guys at GAMI I bet have seen as many if not more cylinders than you ever will. I cant be 100% sure, but I would bet serious coin on it.

Then you have been taking on several people who include experts (really...seriously top of the pile) in Aviation Law from not only senior airline positions but also regulators, and those also have engineering quals as well.

You have taken a poor attitude to one guy with well over 39,000hrs of flying (plus who knows how much not logged) in a list of aircraft from J3 cubs to B747, and some fiery beasts in-between, and that list is so long it is quicker to write the list not flown.

I just do not get it. You refuse to answer any question I ask of you, yet you get narky for missing one of yours, which I promptly addressed.

You do not have to believe me.....just the data.

In respect of your not wanting to paste the CASA fight on here, would you PM a link of the public record to me. I would like to learn some stuff from it. Seriously I do.

Creampuff

yr right, you appear to be labouring under yet another misconception. You appear to believe that the spark occurs at exactly the same instant as the points open when the engine is running. It doesn't.

It takes time for the collapsing primary current to cause the voltage in the secondary to build sufficiently to arc across the plug gap. During that time the crank is rotating. It's not long, but it's long enough for the crank to rotate half a dozen to a dozen degrees (depending on RPM).

The mathematics is quite simple and the reality in operation is measurable (and has been measured).

Leave operation to the experts.

PS: You are correct on one suggestion - the manufactures do take this into account in determining the static timing spec.

Jabawocky

AxA

Creamie has answered that already, but in addition to what he has described, there are subtle differences from some mag setups to others. On the Turbo 540 there are two kinds of magneto drives. Static timing can be set the same, the actual spark plug firing is a couple of degrees different.

In addition the spark firing moves quite a bit from one combustion event to the next. There is a bunch of dynamic stuff going on all the time including an amazing amount of crankshaft torsionals that are mind boggling when you see the data. This all adds up, and some of the effect is from the cycle to cycle variability of which there are about 20 per second.

Most of the variation is in the mechanicals before the points even get opened, but there is some variation there after as well.

All of this is challenging to the mind. And of course it does not really exist if you do not have the ability to measure it. But when you do....a whole new world of understanding erupts. All this good data is clearly stuff yr right knew but has forgotten. But it can be learned again!

Andy_RR

I'd beg to differ on the ignition timing thing a little Jaba. Whilst there may be variation between dynamic ignition timing and static depending on engine speed (i.e. torsional vibration effects), at a constant speed the ignition timing is pretty consistent. Certainly less than a degree variation - you can see this clearly with a timing strobe as I have done on many test engines.

What does change from cycle to cycle is the ignition delay, which is conventionally defined as the time between the initiation of the spark and when the mass-fraction burned reaches 10% - that is 10% of the total heat energy has been released. This usually takes a very long and variable time compared to say the 10-90% burn time which is usually relatively more consistent. All of this is calculated from indicator diagrams - these days in real time with all the fancy DSP available to us.

The ignition delay is a function of how fast the flame kernel grows from the spark and depends on mixture ratio, preparation, micro turbulence, combustion chamber and gas temperature and probably also the phase of the moon.

Jabawocky

Andy,

I beg to differ that we differ Just watched a dyno run to double check this. The beloved Chieftan engine no less, and at cruise power variation was anywhere from 0-1 degree on any cylinder. At Idle / warm up it was typically double that.

So we are in extreme agreement. And this is normal. The average is also several degrees different to the static timing mark. This is the concept that yr right was struggling with I think.

And as Creamie has pointed out this is consistent with what the manufacturer designed it for.

We are all on the same page

Ultralights