Agrajag

...no.

On the Lyc (Bendix) system, the pump is merrily pumping away, potentially supplying more fuel than the engine needs. The FCU simply limits that output via a diaphragm which responds to pressure drop across a venturi, to arrive at the desired flow. The pump can go as hard as it likes, but the FCU controls flow. That's why the flow doesn't change when you switch on the boost pump and raise the input pressure.

Sorry, but you lost me ages ago when you claimed that TCM and Bendix systems work the same.

You didn't ask me, and I'm not even that smart.

Boost pump -> inline sender -> EDP -> FCU. The sender measures the flow through the pipe, on its way to the engine.

Jabawocky

Cockney Steve,

Just a finer point, but the most detonation prone mixture is one that occurs around 35-50dF ROP. This happens after leaning past the best power point of 75dF ROP.

This is not to say that when conditions are right that you can't get mild detonation starting a bit earlier, because it depends on the severity of the conditions. These boundaries are very fuzzy ones but they do not extend past peak or if they do it is not easily perceivable as no LOP mixtures support detonation. One caveat here, perhaps some poor octane mogas in just the right conditions (read hard to achieve) will continue to detonate mildly at just LOP but not for long after that. Avgas at min spec or G100UL at min spec does not.

In the quest to provide the world with a certified unleaded Avgas with equal or better properties GAMI have been doing hundreds of hours of detonation testing on all manner of fuels, and I am privileged to be involved in a small way. The Data shows where common misbeliefs are simply that.

I am sure over the last 15 years Walter Atkinson has seen plenty more of this himself and would validate this.

Just to provide some balance here as many people get these two things mixed up, pre ignition events can occur while LOP, although most likely at higher powers so typically for that to happen it will need to be in a turbocharged engine.

Aussie Bob

I can only comment from my experience with one engine. The carby heat evens out the EGT's but it takes time for it to happen. I suspect that the inlet tubes need to be a bit warmer than OAT (hence the time). There is no judicious use here either, its full carby heat or nothing (again only my aeroplane where according to the carb temp gague, it is on or off). Looking at the route the carby hot air takes, I would suspect the inlet velocity is reduced.

Hopefully someone else can help with more info on this subject.

yr right

We'll some people are smarter than I. I used the nitro engine as an extreme as you can see what happens. I said they work the same because they do. The both have pumps an fcu and nozzles. They go about getting the fuel in a different way. As I said before. 34 years I've been doing this. Not one whine in flight shut down. Not one engine failure. God knows how many engine services I've done but you all seam to know and won't to tell me how I do my job. That's fine when you start signing your own M/R. And like I said fuel flow is measured from the FCU to the spider know one I've talk to has any idea where you get fuel flow pre fuel pump. Also every thing I've said has come out off my head. I've not gone to any books and not done any research with exemption of ask a few pilots and friends there thoughts on lop and fuel flow sensor. So sorry Jaba when you ask a very technical questions with out technical data I won't and can't answer them. The information I give is in it's basic form and there is a genuine reason for that.
I fully understand how a fuel system works. I also understand how a turbine fuel system works and make a piston engine system look like it should be on a lawn mower. I am also turbine lic.
I am always learning. It never stops. I also said if the manual says go lop do it. I don't care what you do. All the pa 31 I've look afyer over the years to my knowledge none of them flew lop. I said it before. Fuel is cheep.
Anyway I off to learn my silence.
Cheers

rnuts

If you are running LOP and using carby heat to do so. What happens if you get some situation whereby you start to get carb ice? Could you then be in a situation where engine failure is possible?
I doubt this was the intended use for carb heat.
Very interesting thread!!
I am now very keen to learn more about LOP operations for my 421C.
Previously I was too afraid to operate these engines differently to what I had been taught due to possibly screwing it up and causing damage.

Aussie Bob

Cruising with carby heat on keeps the carby well out of the icing range. An EMS includes a carb inlet air temp gague. My experience with carby ice is always with a low inlet temperature, but again, more opinions please. I am a beginner with this stuff.

Old Akro

Do you want to think about that again? To get carby ice you need....

Unfortunately, often what we are taught is not consistent with the engine operators manual. Go to Essco or wherever and buy a copy of the engine operators manual for the 421 engines. Most of the time that is consistent with what the Advanced Pilot Seminars teach. If you want to learn more, enrol in one of Jaba's courses.

The geared turbocharged Continental 520's require a lot more caution and you may find that you have trouble maintaining pressurisation at the power levels used for LOP operation. John Deakins has a couple of articles specifically on turbocharged engines. Go to Avweb and find them. Print them and read them more than once.

Note: By some freak of luck, TCM have a pdf copy of the engine operators manual for the GTSIO 520 D fitted to the 421.

see here:

http://www.tcmlink.com/pdf2/maintena...044/x30044.pdf

There are a few things to note:
1. TCM recommend climb at 75% power full rich. Your climb will be a different thing than the average BO because instead of climbing to 4-6,000 ft you're probably climbing to 20,000 ft or more (hopefully at Carson speed). Cooling deteriorates and becomes more critical as the air becomes thinner / dryer so inlet charge cooling from rich operation becomes more important. Especially since Australia is typically 15 - 20 degC above ISA temperatures.
2. There is a strong chance that a LAME somewhere has screwed up your fuel pump settings. Its tedious to set properly and many don't bother or think they know better and can do it by "feel". The engine operators manual shows a maximum fuel flow for 75% power. Check your fuel flows against that. Our aircraft is too rich, so I lean in the climb to achieve the Continental figure.
3. The Continental instructions are based on TIT, not EGT. On a turbocharged engine they can be quite different. Do not apply the APS / Deakin teaching to TIT. You need to fit an engine monitor to follow their teaching.
4. There is a lot of data, but not presented in a user friendly manner. You'll need to do some unit conversions to make sense of it all. Get out a pencil and change the charts.
5. The Continental manual defers to the Cessna POH for cruise leaning instructions. The Cessna POH seems to be saying to lean to a fuel flow derived from a fuel computer. However it also suggests leaning to peak EGT below 65% power. Deakins et. al. will cry that this is inside one of their red boxes. However, you need to know where the temperature is measured first and the Cessna POH doesn't say. If it is in fact a turbo charger inlet temperature (TIT) rather than an EGT (near the exhaust valve) then Cessna may be correct.
6. In my (limited) experience with pressurised aircraft, you might find that it doesn't maintain the cabin altitude at the flight levels that give best efficiency at 65% power. There are more gains from optimal altitudes than optimal leaning. Someone will correct me if I'm wrong, but I don't believe APS advocate LOP above 65% power.

rnuts

Old Akro.
Ok mate no need to be a smart a$$.
Was just asking the question.
I know you need moisture, which is always present to a varying degree.
Also you need the temperature drop at the Venturi to be below the freezing level.
I gather you are saying that it would be impossible for the formation of ice with carb heat on all the time.
The guys here for the most part have been keeping these discussions civil which I think is fantastic.

Old Akro

Didn't mean to be a smart arse, just cheeky. Sorry.

Besides, you have injected engines, so no venturi.

Continental engine operators manuals & Cessna POH's are about the worst combination you can get. They really don't make it easy to run the engines optimally. And a turbocharged engine providing cabin pressurisation as well as engine boost works pretty hard in the flight levels where the engines can be cooling limited as well.

rnuts

No worries.
Intent can be difficult to judge at times.
I fly many different aircraft from little Cessnas to Jets.
The carb ice question was just something I thought was worth addressing.
It worries me that people try some of these practices without proper equipment, training and understanding of what they are actually doing.

Brian Abraham

rnuts, you may want to get in contact with the guy here. See the bottom of page for contact details.

Operating a Cessna 421 C LOP ? Insurance Approved Training

Creampuff

From the text at the link in BA's post:How could that be so, yr right??

yr right

We'll cream puff I said I not posting any more. But I will say this and you can correct me if I'm in correct. Tcm knew they had a problem with the cly on gsio engines. They change some stuff and wow really no one has a problem any more. As a matter of fact I'm working on them today oh also biggest problem do gstio engines is the driver.
Cheers

Creampuff

I’m still interested to know some of the mistakes you’ve made and the misconceptions under which you’ve discovered you were labouring, over your 34 years’ experience as a LAME.

What were the circumstances in which you took a step back and thought: “Hang on sec’, I have this all wrong.”

If your answer is: "Never", that would explain a lot.

yr right

Cream puff.
I'm more than happy to stand behind my record in aviation. I take your comments like the toilet paper they written on. I have a failing that I don't suffer fools lightly you fall into this category.
We have a saying here in aust.
I would not piss on you if you where on fire and in the gutter. In this case you also fall into.
You will not get any further response for my self.
Cheers

gerry111

Creampuff, Please don't say it! Just go and have one of those 'Pabst Blue Ribbon' beers...

Aussie Bob

It has been explained.

yr right

What. No engine shut down no engine failures no wheels up no accidents cause by my self. What do you people won't it is
Your life's in our hands.
You all amaze me no end.
Cheers.

Oracle1

yr right you are now playing the man and not the ball


you are showing that you are not even willing to analyse new ideas much less judge them on their merit. Jabawocky et al know their sh@t and have evidence based on the scientific method of analysis. LOP has a well proven history and when conducted in the correct manner can be beneficial.

A true professional accepts when they are wrong admits it and moves on with a higher standard of knowledge. A true professional always accepts there is more to learn. Theories get disproved all the time.

You should do some more study before you deride others based solely based on the fact that you are a LAME and they are not.

Just because you are a LAME does not mean you are the suppository of all knowledge on engine management

cockney steve

THAT has to be the best Freudian slip, ever , on here.

For those in doubt, Googoo "Suppository" and "Repository"