Walter Atkinson

FWIW, POHs and operations manuals have been recommending LOP mixtures since the 1930s. Some do not address it in the text but almost all do in the engineering data.

We show this during the APS class.

ALSO, the Wayalla issue would NOT have avoided disaster had it been run full rich. There was a crank issue as well. The engines were NOT run lean. THEY WERE NOT RUN LEAN. They were run "not rich enough" ROP. If one does not grasp the significance of that, one is lacking in the understanding necessary to evaluate the event properly.

The Coroners Inquest came to Ada, Oklahoma, to see this data first hand.

This report is one of the classic examples of an investigation run amuck. They got most of it wrong--according to the HARD DATA.

scavenger

Thanks Jabba. I guess I am looking for something in an AFM that says, look at the EGT, lean until peak, then continue leaning until 50 (or whatever) cooler. Are there any examples of this? The Lycoming Flyers I've read specifically deal with leaning using EGT but don't mention this technique.

Do any of the engine monitors come with AFM supplements that specifically say to operate LOP?

You've all convinced me that you each believe in your opinions, and I would be keen to come to the course advertised in this thread, but it would be pointless for the operation I'm involved in without compliance with CAR 138 (my mother's presence aside - thanks for that one) as CASA sees it. All the flight manuals in the operation I'm involved with say lean to peak EGT (best economy) or peak + 100 ROP for best power.

Creampuff et al, you have convinced me you believe in the danger of operating slightly ROP, no need to rehash that again, when I am asking about operations LOP.

43Inches

This was always the problem with flying Pa31s (or any other GA aircraft), every operator did things differently, how they arrived at their procedures probably came from different types and rumour rather than good condition monitoring and trend maintenance.

There is a procedure in the PA-31-350 manual para 4.37 "lean side of peak" procedure.

(a) set desired power setting and lean until peak;

Do not exceed 1650F EGT

(b) if peak is below 1650F or less continue to lean until maximum of 50F reduction in EGT. Readjust manifold pressure to desired setting.

(c) (long winded procedure for use if 1650F is achieved prior to peak)....

It does not state when to use this, or what fuel flow will be achieved.

In smaller pipers such as the Warrior and Arrow it states to lean (power settings below 75% only) until rough then enrich only enough to allow smooth operation, if the engine is able to run smooth LOP it will be LOP.

Old Akro

Its worth remembering that the aircraft manufacturers POH's were written around the standard instrumentation of the time. For a lot of aircraft this meant no EGT instrumentation at all.

As better instrumentation becomes available, so does better operating techniques.

When we get lambda meters the discussion of EGT will fade and we'll talk about Lambda (air / fuel ratio) readings.

Aircraft with a single point EGT measurement may have an EGT setting specified by the manufacturer designed to protect the cylinder with an outlying reading given that its known many engines have significant cylinder to cylinder variation.

If engines weren't so heavily regulated and changes were not so expensive / difficult, I suspect we'd see aftermarket intake systems that provide better cylinder balance rather than the band-aid of tuned injectors. Until then, GAMI injectors are the best option for engines that require cylinder to cylinder correction.

Agrajag

Yes Conti and Bendix do the same job of supplying fuel to the injectors, though in very differing ways. That understanding means that we as pilots operate them in a different manner, from starting technique down to usage of the boost pump. And I'll say it again: our fuel flow sender is pre-FCU; in fact it's pre-fuel pump.

I could indeed, and I could probably also do so for a RR Dart, but both would be equally irrelevant to this discussion. I don't believe I need to prove my credentials in order to demonstrate that you have no idea of what is in our particular aircraft, and therefore how it's best utilised. You're lecturing me, and others here, on the basis of some broad assumptions that were never true.

I hope you didn't offer strident, condescending advice on these varied aircraft without even setting eyes on them, or knowing what engines and equipment were installed. Because that's what you've been doing here!

Sorry yr right, but all the way along you've been pushing the hard line that there's only one way to operate all piston aero engines, and that's simply not true. I was taught the same stuff when I started, but I've since become aware that it was an over-simplification. We now know more about what's going on inside the engine, and we can use that information to optimise its operation in every phase of flight, instead of a one-size-fits-all rule. And since we didn't just buy our licences, as you sneeringly inferred a while back, we have the capacity to do so.

43Inches

All I need is Torque(BMEP) & RPM to set power, I think manifold pressure is a very poor gauge of power output, it is only good for letting you know when your manifold will eject in TC engines. The other monitoring equipment such as EGTs, CHTs, FFs etc to let me know its healthy. Knowing the fuel/air ratio going in doesn't really help to operate it.

And it works just fine without an EGT on these aircraft, the EGTs fitted to them tend to barely work at the best of times along with pilots able to correctly follow the leaning procedure.

Progressive

"Sorry Jaba you are in correct. The fuel pump has nothing to do with fuel flow in either tcm or bedix system. The fuel pumps supply fuel to the fcu. That is there only function. They do not in either system control any fuel flow to the engine"

Yr Right,
If you are going to call someone incorrect - make sure they are.
TCM fuel system is a pressure dependent fuel metering system, this system does not measure airflow through the engine it works by metering fuel in proportion to the relative position of the throttle valve (there are no blast tube or venturi suction measurements taken from the air side).

Fuel is supplied from the pump at a set pressure (un-metered pressure) to the fuel metering valve where the mixture and throttle metering valves (variable orifices) which reduce the pressure down to a metered value before sending it to the spider. With a known pressure across a known orifice (injector nozzles) we get a known fuel flow for the particular throttle setting.

Fuel pump output pressure is critical in this system as any change in pressure to the going into the metering device will change the metered pressure output.

All of this needs to be adjusted to get the engine running right, failure to do this will lead to low fuel flows at takeoff power and exactly the kind of cylinder damage you are talking about.

If you dont believe me believe continental:
http://www.tcmlink.com/pdf2/SID97-3F.pdf

Or for a more simple description of the system:
http://www.kellyaerospace.com/articl...inuousFlow.pdf

And before you bemoan pilots giving you advice I AM NOT A PILOT.
I am a LAME (and aircraft owner) who has:
Worked in a fuel overhaul shop
Overhauled radial, opposed and V engines
Spent 8 years maintaining a fleet of Chieftain engines
and instructed students in aircraft piston engines/theory/systems and maintenance for the last 3 years

PLEASE STOP FIGHTING A LOOSING BATTLE and making LAME's look bad. Take the free course!! If you don't believe it dismiss it AFTER you have tried it, otherwise take what you can from it to be a better LAME.
That is the sign of professionalism in ANY field.

Tinstaafl

To counter that no POH has LOP operation described & approved in it, a 1980 PA31-325 I operate has LOP ops in its POH, just like 43" described - and that's with the factory single point EGT & CHT gauges. Mind you, I had the owner install an EDM before I'd do LOP, other than a demo of the fuel savings to be made. According to my logbook I've flown this particular aeroplane 700+ hours, and I've run it LOP in the cruise by default for nearly all those flights.

Jabawocky

Scavenger
Well you could find it in some but not others, explicit good education that is. Problem is as described by others above, you will struggle.

As a comparison, the POH does not tell you how to comply with the Instrument Flight Rules, yet the aircraft is approved for IFR flight.

For some reason the thought process is unless it is spelled out explicitly in the POH you can't do it. No thinking allowed.

Also for LOP ops or for that matter ROP ops, the appropriate amount either ROP or LOP varies as the power increases. The book gives one set point and it is only one recipe in the cookbook, not all of the infinite possible variations.

Lumps

So hang on - fuel flow is displayed as a product of pressure in Continentals only?

The BE95 (Travelair) has Lycomings yet fuel flow gauge is pressure, or that's what it says on the gauge anyway (there's a little red line saying 10.5psi or something, can't remember the number)

Does this just mean the gauges are plumbed in to a different part of the fuel delivery system?

heated ice detector

I think YR (with his interesting methodology ) is posting that the fuel flow gauge on a Lycoming or Continental is actually a pressure gauge calibrated for fuel flow. I think!!!

yr right

Well I think will be my last posting. So ill clear so stuff up.
I was ask to comment on lop, so I did and all my experience meant nothing cause I had no data. Of course I don't have data no one dose cause we never recorded it as such. But ive seen plenty of upset faces in my time when given the cost of repairs.


Now I know exactly how the fuel pump works. But its still a pump that's it role a pump. You also forgot the regulators and what about the bellows as well. Now the pump dose not drive the fcu The fcu drives the pump in both cases lyc and TCM. Flows from both pumps will increase as the rpm rises. Now also fuel flow can be changed via the mixture lever as well as throttle position. The Fcu leads the pump follows.


Next ive ask everyone I know and no one ive talk to has any idea how you are getting fuel flow pre pump and pre fcu this includes some extremely smart EIR guys I know.


Now this one has puzzled me for a little while now. The reason why everyone has duck for cover made excuses . Why the e second engine stoped. Now to say it was rich enough and it was doomed to failed is sorry f&*king bullsh7t. Simple put it if that engine had full fuel it would have made it back. It didn't even Jabby said well yes it would have kept going. Simply put it it engine was under maximum load trying to keep the machine flying. You can not use oh the crank was crack so it was going to fail any way, when was it going to fail. The aircraft took off didn't it.
Now this leads me to this point.


The engine failed due not enough fuel to be supplied to the power setting that was asked for, simple. Now not really related to LOP but if you read between some line and think about it to your selfs. I really don't care what you think about me you don't even know who I am. But I wont put a pilot in a machine that I wont fly in my self, on that note there are a lot of pilots that I will not fly with.
Cheers

Jabawocky

yr right

I can't understand your last post.

Would you please give me the courtesy of answering my questions. I did for you?

I am trying to help you here.

Brian Abraham

But you've not answered the question as to why some of the flat engines, as in the Chieftain, are approved for LOP. What is so special about those engines, vice a properly fitted out aircraft as Jabawocky possesses?

Walter Atkinson

It is a very painful thing to experience when your long-held beliefs are upset with hard data. We have been watching that painful experience in this thread. The only way to assuage that pain is to learn the truth and expand one's knowledge.

gerry111

So true, Walter A.

cockney steve

Yr Right....I suggest you revisit first principles of Internal Combustion Engines....
The key to reliable running was an accurate fuel-air ratio....too rich, wets the plugs and puts the fire out....as you progressively lean the mixture, you reach a point at which it will burn, BUT THE CHARACTERISTICS OF THAT BURN ARE UNSTABLE (DETONATION)

continue leaning, you'll get better power, no detonation but excessive heat within the engine

Continue leaning LOP, you've got rid of theSURPLUS ENERGY IN THE FUEL-AIR CHARGE IN THE CYLINDER....So, you get a clean, cool burn with the exhaust being predominantly waste gases.

Your dragster analogy is an entirely different scenario.....very little of the consumed fuel is actually pushing down the pistons...that is self-evident by the huge columns of flame out of the exhaust stacks.
Of necessity, I've tried to give a much simplified account of why LOP is , of itself not doing the damage. hope this gives you something to chew on!
Back to another poster....my European contact changed the starter because he thought the cranking performance was well below par (he was correct) IF the new starter whizzes over the engine, sufficiently fast to lock-out the Impulse mech. THAT IS EXCELLENT!
The piston is travelling sufficiently fast, that the now-advanced spark can ignite the mixture and the piston goes OVER TOP DEAD CENTRE BEFORE the burning mixture can develop enough pressure to knock it back.
Q.....Do you tell all pilots to start on single-mag (impulse) only??

If not, why not?

It was after the starter change that he investigated further, as it still was extremely reluctant to start,despite battery, solenoid, cables, return-path all being OK plus a new, permanent-field starter which punishes the battery far less than the wound field-coil variety.
IIRC, plugs had done under 50 hours they were not a prime suspect until all else had been eliminated.

Another customer lost to Champion. Ask any motoring enthusiast what
the best plugs are...invariably it is NGK Bosch and Denso....Champion are now a poor "also-ran" trading on past reputation......Sad, because pre-war and into the 60's they set the standard and others followed.
I speak from personal experience and as "the man on the Clapham Omnibus" (average joe public!)

No Hoper

Cockney Steve, Detonation on startup?
Dragster flaming at idle is caused by cam timing overlap duration as previously explained.
Maybe this thread name should be " LOP- True Beliebers"
A starter that rotates the engine at an RPM that "locks out" the impulse coupling would not be approved for fitment on that particular installation.

No Hoper

I declare I have no dog in this "fight".
Without giving away propriety information, Consider stoicheometric mixture of 17: 1 or there abouts. What is peak, what is less than peak and what is more than peak? Note the terms more and less as I find lean of and rich of misleading in this case.

OZBUSDRIVER

Back on judicious use of carb heat to improve fuel distribution...are we after better mixing due to heat or higher induction velocity(better induction signal through carb throat)...granted, methinks I am after free info but pertinent question. Just cracking carb heat a little until roughness improves then attempt to lean again?