Lean of Peak, Flight Manuals and CAR 138

[Wing Root]

I've been having a look at a POH for a Cessna 206 and on page 4-18 is has the following note.
Operation on the lean side of peak EGT is not approved.
So, now I get a JPI engine analyser and a set of GAMI injectors fitted and choose to run lean of peak. Is this an offence against CAR 138 (http://scaleplus.law.gov.au/html/pastereg/0/51/0/PR004870.htm)?
Do things change with the STC for the injectors? I would like to know what the deal is here. :confused:

Thanks for any help. :ok:

[Jamair]

I'm sure Creampuff et al would wax long and lyrical on 'offences of strict liability'; however the key phases here are from the manual, from the CAR, and from yourself.

The manual says 'Operation on the lean side of peak EGT is not approved', ie don't come running to me if you do it and destroy the engine, or kill / injure someone in the process'.

CAR says that failure to follow a 'requirement, instruction, procedure or limitation' from the manual is an offense' - if you get caught, which will only happen in the above circumstance.

You say that you 'choose to run lean of peak'. Your choice, your problem as per the above.

You can however produce a defence based on inconsistancies between the POH and the engine manufacturers recommendations; wherein (some) Contis and Lycos are specifically approved for LOP operation despite the aeroplane manufacturer disapproving it. The STC for the GAMIs specifically states that LOP operation is a matter of POH recommendation and operator choice and not part of their type certification.

For my money, and my engine dollars, if the JPI is demonstrating CHTs within or better than the recommended parameters, it matters not whether the engine is LOP or ROP as long as it is outside the danger zone (see previous thread on running 'oversquare'):ok:

[Creampuff]

The question whether you’re allowed to do it or not has got nothing to do with strict liability. I’d get an expert to advise you as to whether the effect of the GAMIjector STC is that you may now run LOP without breaching 138.

On a more important note, I would be interested in the results you get/are getting from the GAMIjectors. Could you post your pre- and post-GAMIjector lean test results here?

One ‘left field’ point on the oversquare issue – propeller manufacturers do vibration analyses that sometimes result in limitations that effectively preclude oversquare operations. For example, there is a commonly used GA propeller that the manufacturer says should not be operated continuously above 2500 at an MP above 25inches on a specified “undampered” engine. In other words, the limitation is not to protect the engine, but to protect the propeller from vibration caused by the engine at tested RPM/MP combinations. Whether the GAMIjectors reduce that vibration is another interesting issue…

[Jamair]

Hi Creamy; you could fill a warehouse with what I don't know / understand about strict liability - I threw that out as a bait 'cause I was aware of your 'interest'.....:E

The STC documentation that comes with GAMIs specifically states that the engine is to be operated in accordance with the manufacturers recommendations (so they don't cop a load of suits from people mis-using the set-up and frying engines).

Same goes for the users instructions in the JPI - 'This is how to set up LOP, but you need to operate the engine in accordance with the manufacturers recommendations'. There are several aeroplanes that recommend LOP operation and will only work properly using that technique.

My lean test was VERY interesting. The object of the exercise is not aimed at having all cylinders running the same temps - that is practically impossible, especially on some of the older installations. What is examined, is whether all the cylinders 'peak' within an acceptable margin of each other. On one of my engines, the pre-GAMI lean test had a 'spread' of 15 lpm flow rate between when the first cylinder peaked and the last one peaked. The standard EGT & CHT were fitted to one of the mid-range cylinders, which meant using the readings from them to adjust mixtures resulted in some cylinders being LOP in the danger zone, some ROP in the danger zone, and some in a safe ROP area. Post GAMI, not only was the engine very noticeably smoother and easier to start (quite a feat for hot-starting Lycomings), but the spread was down to 3 lpm between first and last cylinders peaking.:ok:

I have recommended to plenty of people to seriously look at installing GAMIs and a JPI; some of the best money you can spend on your aeroplane. It generally only takes a ride in mine to convince any sceptics of the value of these bits of kit.

As far as engine / prop harmonics go; having a smoother engine could only be a good thing, but as the suppliers direct operators to follow the manufacturers directions for operating the aeroplane (and GAMI etc are unlikely to want to undertake the extensive testing required to win an STC that changes things like engine/prop vibration zones) then I don't THINK there would be any changes allowed there. However, I have seen changes of prop that have removed or reduced original limitations in these areas. Archers, Arrows, Grumman Tigers and Commander 112/4 are some that spring to mind for RPM restriction zones that can be altered / removed with alternative prop installations.

CU

[Icarus2001]

An interesting discussion. Unfortunately I do not have a C206 POH to hand but surely the definitive reference is publications from the engine manufacturer not Cessna, the aircraft manufacturer. Where the two disagree I would be happy to argue in court that lycoming know more about their engines than Cessna.;)

The old leaning chestnut is a great argument starter, have a look at this...

http://www.lycoming.textron.com/support/engineOperationTips/SSP700A.pdf

I definately agree that engine monitoring and/or analysis instruments should become mandatory for Transport category operations. Especially in thirty year old Navajos & Chieftains etc.

[Wing Root]

Thanks to all for the replies.

Just to clarify, I don't own a Cessna 206. I was just thinking about the ramifications for others in this situation.

Although I have read most of John Deakin’s articles I actually hadn't read this one (http://www.avweb.com/news/columns/186015-1.html) when I posted first off but after having a read it may well answer the question. Especially this point....
What gives me heartburn are the people who say, "Takeoff with flaps is illegal, unless it's in the manual." Absolutely not true, unless it's in "Limitations," with language like "Takeoff with flaps is prohibited." Now that's something you can hang your hat on. If that sort of language is in "Limitations," and an FAA type sees you use them for takeoff, he's got a legitimate bust.
My quote from the flight manual was not from the limitations section, it was in amplified normal procedures. All the powerplant limitations listed in the POH limitations section can be complied with while running LOP.

Another piece of rather curious information was that Cessna call the EGT gauge a "Cessna Economy Mixture Indicator" and it's OPTIONAL. The normal leaning procedure is to use the rather dubious fuel pressure gauge disguised as a fuel flow gauge.

[Creampuff]

Jamair – thanks.

The lean-of-peak debate is a perpetually interesting one. Mr Deakin has me convinced. I also recall a flight test article on a recently-released FADEC-equipped GA aircraft that said the FADEC automatically leans the mixture to – surprise surprise – 50 degrees lean-of-peak.

What I laugh about is that even if Deakin’s wrong in theory and the FADEC manufacturers and I’ve been sucked in, the ‘lean test’ results such as those done by you and many others on an average GA engine show the blissful ignorance of running rich-of-peak – or at least thinking you are – on the basis of a single EGT gage.

The cylinder to which the EGT gage is attached may well be running rich of peak, but what about all the others? Perhaps these engines are designed so that it’s dangerous to run the EGT gaged cylinder lean-of-peak, but some or all of the others can take it!

[swh]

Wing root,

The actual "flight manual/POH" people buy off the shelf will have information contained in it which exceeds what was the “certified” flight manual, additional information as you have indicated "amplified normal procedures" etc. which may or may not form part of the certified manual.

To see what actually forms part of the approved flight manual you need to first have a look at the Australian Type Acceptance Data Sheet to see what manufacturers Type Certificate Data Sheet was based on.

I do not have your manual in front or me, nor the Australian TADS, nor the TCDS so I cannot tell you exactly what constitutes your "flight manual".

Icarus2001, the engine and prop will also have their own TCDS, however it’s the aircraft TCDS holder that certified the aircraft, and they alone have access to the "big picture" of the airframe/engine/prop combination. The engine TCDS holder may know more about their equipment, however they would not have access to the flight test data that the aircraft TCDS has.

Many examples have been cited over the years, esp. with turbofan engines where an engine manufacturer has learnt more about their engines from the airframe manufacturer.

[Chimbu chuckles]

Great!!!

Let's all follow slavishly POHs that were written 40 years ago that hold precisely ZERO information that is of any real value in how to operate aircraft properly or safely let alone economically!!

The brand spanking new AFM that CASA dictated I buy last year for my 1970 A36 is the exact same part number and contains, word for word, the same lack of information that the original POH contained in 1970!!!!

The sum total of POH/AFM info on leaning is gauranteed to have you damaging your engine but let's do that because some CASA legal moron says we must!!!

Heaven forbid we be allowed to fit modern technology, and pitch the original fit crap, and then operate the engine as it should be operated based on imperical data!!!

Let alone that technology be mandated for aircraft in commercial pax carrying ops.

My Boeing 767 manuals are as bad...and almost obscene lack of info...written by people watched by lawyers who think that too much info will get them sued!!

A ray of hope is that the current boss of CASA airworthiness in Canberra is a convert to the technology embodied within all cylinder monitors and Gamijectors and has told me that I can write a amendment for my A36 AFM allowing LOP ops....when I'm not so busy with the above mentioned Boeing I'll finish it off and submit it. In the meantime my IO550b spends it's life either LOP/Peak or ROP as appropriate to the conditions inflight....and you can shove CAR 138. The TONS of data available would make any spurious court battle a doddle to win!!

Creamy...blissfull ignorance is exactly right!!! But for aircraft manufacturers to not provide the requisite info in the POH and the technology on the dashboard is bordering on criminal. I fitted JPI/Gamijectors to my Bonanza 15+ months ago and could no sooner fly without my 'engineer in a box' than I could without petrol in the tanks....I'm proud to say that a short while later I sat Jamair in my RHS and said "watch this" :D

Chuck

[Jamair]

:p Aww Chuck, now you're just skiteing......

Seriously; anyone who has an interest (and that should be EVERYONE who owns or operates a piston engine aeroplane of ANY vintage) should read Deakin and follow his links to the SCIENTIFIC DATA (as opposed to the myriad of OWTs - Old Wives Tales) that we are all fed in initial training; then if not convinced, go find someone who has been and let them take you for a fly - hell, call ME and I'll take you in the Aztruck or even in Chucks Bonza (now hes OS and can't stop me.....:} )

FACT - Whyalla Airlines would still be flying if their aircraft had been voluntarily or obligatorily fitted with these devices.

I’ve just overhauled an engine at 2000hours which had no failures through that time, using GAMIs and a JPI; and the new $45K engine is doing just fine with them as well. Hows that for putting the money where the mouth is? The AF based V35 who recently flew around the world solo – did so with GAMIs and a JPI – LOP the whole way, and is still flying the same engine.

As for original POHs - PuhLEEESE! The 1969 POH for my Aztec doesn't even include a power setting table - Piper clearly thought pilots were too stupid to understand how to use them!

[Creampuff]

Latest Aust Aviation, Cirrus Airtest, page 61:By further leaning to best economy (35-40degrees lean of peak) that speed drops by 5 to 10kt, but with a 15 per cent fuel burn improvement.[bolding added]

One wonders why it's not raining Cirrus, rather than Cirrus reigning!

[Capt W E Johns]

A little while ago, I ran some tests trying to improve efficiency while flying a Lycoming - figures at this page:

http://wal.t.tripod.com/aeio540l1b5.htm

[djpil]

Capt, it must be too late for me, I'm having trouble with the arithmetic so I don't understand the figures in the "Best TAS vs SFC Compromise", subtitled "best kts per litre of fuel of fuel burned ratio".
60 l/hr and 154 kts shows a TAS/SFC ratio of 395. I don't understand that term TAS/SFC?
nm/litre of fuel is 2.57 from my calcs. I just took a few lines and plotted this Specific Air Range vs TAS, that sample looks good.

[Capt W E Johns]

I tried to get too clever for myself! You're right... I'll adjust the page shortly.