Cessna 172S Fuel Burn Question

[SkunkStripe]

Where in the POH can I find the fuel burn table or equation for flying full rich on an engine break in? All I can find is the power setting for 75% power.


Sorry if the answer is obvious.

[SkunkStripe]

If its not there; where can I find this info?

[ahramin]

Do you have any guidance from lycoming telling you to fly full rich and above 75% power for the break in?

http://11hc.44rf.com/manuals/engine-pro ... prints.pdf

Page 35.

[SkunkStripe]

Interesting. The owner wants it run full rich. Will have to contact Lycoming for documented procedures then have a nice detailed chat with him.

[SkunkStripe]

Good thing I asked. I did find it weird to run something full Rich.

[SkunkStripe]

Yeah. So even the Lycoming break in procedures state to follow the POH. Cant find full rich anywhere on anything.

http://www.lycoming.com/Portals/0/techp ... mption.pdf

[SuperchargedRS]

I've always just used my mixture to keep target CHTs primarily and target EGTs secondary.

You have a engine monitor?

[PilotDAR]

So even the Lycoming break in procedures state to follow the POH. Cant find full rich anywhere on anything.

Huh?

Cessna 172 POH:

"BEFORE TAKEOFF
....
7. Mixture -- RICH

.....
ENROUTE CLIMB
....
3. Mixture -- RICH (above 3000 feet, Lean to obtain maximum RPM)"

The owner wants it run full rich.

Were I the owner, I would too!

[ahramin]

He's talking about cruise PilotDAR.

[pdw]

Re: "obvious answer"

for flying full rich on an engine break in

The engine break in specifics are temporary and occur only once at the beginning; why print in POH if a "rich" order is submitted directly to any new owner (for that short period) upon delivery ?

[cncpc]

I've broken a few engines in and as I remember it, there is no special procedure.

I know there was or still is a theory that the engine should be babied in the first few hours, but I remember that is the wrong thing to do. I'm not sure of the mechanism, but it had something to do with the rings not seating properly within the cylinder walls if the engine wasn't put through its normal power settings. After a while, that became a permanent condition and it burned oil and needed a top overhaul.

There was a procedure with a different oil during the breakin period, either use detergent or non detergent oil only, if forget which. Whatever you normally use, it is the other kind.

I've had an engine fail on the test flight after the second application of full throttle, but that turned out to be a valve guide clearance issue, and nothing to do with procedure. There were no special instructions from the overhaul shop before the test.

[ahramin]

there is no special procedure.

Lycoming SI 1427C Lycoming Reciprocating Engine Break-In and Oil Consumption

http://www.lycoming.com/Portals/0/techp ... mption.pdf

Continental SB M89-7 Engine Operation After Cylinder Replacement and/or Major Overhaul

http://www.continentalmotors.aero/xpubl ... s/m89-7r1/

[Big Pistons Forever]

The C 172S POH, The Lycoming IO 360 Operators manual and the more general "Lycoming Flyer Key Reprints" are silent on leaning during cruise when breaking in the engine.

The only direction is to use high power settings, 65% to 75% being most often mentioned for the first 50 hours. This ensure high cylinder pressures and encourages ring seating. Running low power power setting can result in the cylinder walls getting glazed with oil varnish which means the rings will never properly seat, resulting on excessive oil consumption for the life of the engine

The last time I broke in a new engine I picked a quiet time at the airport to minimize time on the ground and then did 3 hours of laps above the airport with the power set to 75 % and the mixture to full rich. The CHT's and oil temp was initially very high but were back to the normal range by the time I landed. This is common as most of the break in occurs during the first few hours. I stayed near the airport because statistically a mechanical failure of an engine component is most likely after engine maintenance, with an overhaul obviously being the most extreme example of that.

After the first flight the aircraft was de-cowled, the engine compartment thoroughly checked and the airplane released for service. For the next 50 hours the engine was operated at 75 % power with the mixture leaned to a conservative best power setting of 150 deg rich of peak. The oil was changed at 25 hours and again at 50 hours to get rid of any break in wear remnants and then normal operation was commenced. From everything I have read this seems to be a pretty standard way to operate

Continuous full rich mixture cruising does more than waste fuel, Lycoming is clear that that it is harmful to the engine. The full rich mixture setting is designed to provide excess fuel when the engine is developing full power, 180 hp in this case. It will be excessively rich at a lower power setting so I see no reason why you would want to run this way for any time except for the very first few hours. Full rich is only used here because it is onli in those first few hours where engine temps will be abnormally high.

Edit: I see Ahramin has posted the applicable guidance from Lycoming, which explicitly permits leaning in cruise. As I have said in other posts, aircraft owners should not just rely on their POH, they should also avail themselves of all the information provided from the engine manufacture, and as a minimum have the engine manufactures operator manual for the engine in their aircraft

[SuperchargedRS]

So even the Lycoming break in procedures state to follow the POH. Cant find full rich anywhere on anything.

Huh?

Cessna 172 POH:

"BEFORE TAKEOFF
....
7. Mixture -- RICH

.....
ENROUTE CLIMB
....
3. Mixture -- RICH (above 3000 feet, Lean to obtain maximum RPM)"

The owner wants it run full rich.

Were I the owner, I would too!

Hope to god that POH never is read outside of where flat landers and cool weather folks live.

Get a DA of 6,000+ and play that full rich game at your own peril.

[PilotDAR]

Hope to god that POH never is read outside of where flat landers and cool weather folks live.

Cessna are pretty experienced at writing POHs for their aircraft, and thought of this too! A good read of the POH will reveal instruction for this situation too!

[cncpc]

Some of the material Ahramin put up is mostly to do with the period while the engine is still at the overhaulers, or on the test flight or the next hour or so. The OP was seeking advice on how to run the engine in the break-in period which is somewhat longer. 50 hours isn't it, or 25 as far as the mineral oil goes? I have seen them do the test cell bit on a Navajo engine we had overhauled in Halifax, with the club installed for the prop. For the most part, that bit is done by the overhauler or the "test" pilot.

I think that from the break in pilot's point of view, the major thing is to do what is required to properly seat the rings and avoid glazing of the cylinder walls. BPF has the clearest bit on that. I do know of a guy who ran at no more than 55% other than takeoff and climb, and he had to do a top overhaul after 100 hours or so. Probably just rings and hone the cylinders, but...

I would think the engine shop and your AME who installs your engine will have some guidance.

Good thread. I remember that is always some discussion on this, when you put a new engine in, or particularly when you are a renter and the school has just overhauled the engine you're flying.

[SuperchargedRS]

Hope to god that POH never is read outside of where flat landers and cool weather folks live.

Cessna are pretty experienced at writing POHs for their aircraft, and thought of this too! A good read of the POH will reveal instruction for this situation too!

On the single page checklist in my plane, I have it mixture to DA

[Big Pistons Forever]

Not exactly on topic, but related. In the absence of a POH , fuel flows can be estimated by dividing the horsepower by ten to get the full power, full rich fuel flow.

In the case of the C 172S, 180 hp = 18 gal/her. Climb will be 2/3rds of that or 12 gal/her and 65 % cruise leaned, will be half, or 9 gal/hr

[SuperchargedRS]

Or just to target CHT and EGT and good RPM

[ahramin]

Some of the material Ahramin put up is mostly to do with the period while the engine is still at the overhaulers, or on the test flight or the next hour or so. The OP was seeking advice on how to run the engine in the break-in period which is somewhat longer. 50 hours isn't it, or 25 as far as the mineral oil goes?

How did you arrive at your 50 hour figure? The Continental SB says 25 hours or much less, Lycoming just says when oil consumption stabilizes.

NOTE
The  purpose  for this engine  break­in  procedure  is for correct  piston ring  seating  and  stable  oil consumption on a top overhauled engine or a newly overhauled engine that is installed in the aircraft.

NOTE
For correct piston ring seating, in a top overhauled engine or a newly overhauled engine, operate the aircraft at 65% to 75% cruise power until oil consumption is stable.

I would submit that when reading information for the purposes of flying an aircraft careful study would be more appropriate than browsing, even if at first blush it doesn't seem immediately applicable to the problem at hand.

[PilotDAR]

On the single page checklist in my plane

Checklists are great tools. The checklist for one of my planes is a brief placard. However, a checklist (factory, or otherwise) does not replace the "operating procedures" information as presented in the POH. There is much more information, and quantitative values, presented in the POH.

[photofly]

Not exactly on topic, but related. In the absence of a POH , fuel flows can be estimated by dividing the horsepower by ten to get the full power, full rich fuel flow.

In the case of the C 172S, 180 hp = 18 gal/her. Climb will be 2/3rds of that or 12 gal/her and 65 % cruise leaned, will be half, or 9 gal/hr

By your figures why is climb not full power full rich and 18gph? Where does 12 gph come from?

[Big Pistons Forever]

Photo

You are correct. The formula was meant as a general one so for an aircraft equipped with a constant speed prop, the climb fuel flow figure will be close for a typical climb power setting like 25 in MP and 2500 RPM.

In the case of the 172 full throttle climb from a sea level airport will start at 18 gal/ hr but obviously decreases as the airplane climbs and thus develops less power even though throttle remains full in.

[cncpc]

I would submit that when reading information for the purposes of flying an aircraft careful study would be more appropriate than browsing, even if at first blush it doesn't seem immediately applicable to the problem at hand.

The post was from a pilot who was going to be flying someone else's airplane during the engine break-in period, whatever that is. In this case, it was still being broken in.

This is not a situation where the pilot has to go to the engine manufacturers guidance on how to operate the engine. Those documents are not documents required to be on board the aircraft. In over 7000 hours, and a number of hours in breaking in engines, I've never looked at such documents. In fact, until now, I've never known they existed.

It is really the owner's choice as to how he wants the engine operated in the period. If a pilot has been around for any length of time, he's flown break-ins, and knows the prevailing logic, which I accept, at some far back point in history, may well have come from the documents you have quoted.

I don't think we have to carefully study that which is general knowledge. If we did, we'd soon tire of reading Bernoulli's theorem before every flight, or looking up the tire pressure in the flight manual.

It is nice to know the precise steps coming from the manufacturers, i.e. 75% for the first hour, then 65 to 75 after that. Sure, the idea is to get the best out of an overhaul, and that is probably a marginal improvement over 75% all the way through, which I expect was what I was told and did.

Every pilot who comes upon an engine for breakin for the first time wants to know the procedure. This guy, or gal, asked on this forum. Now he or she knows, from several different perspectives, none of which is disputed.