On Condition and Life Limits

[DonutHole]

I am looking for the CARs pertaining to private ownership and on condition programs.

I have heard that privately registered aircraft are not put on condition as the TBO's are not mandatory to be followed.

I am not looking for a spoonfeeding but perhaps a hint as to where I would look in the CARs. I had a customer ask about it today and I don't want to parrot out some b.s. I heard on the internet, I would like to find for myself (with a helpful hint from any of you) where I might find this information

Thank you

DH

[SeptRepair]

Standard 625 APPENDIX C - Item 7
"7. Engines

All piston and turbine engines installed in aeroplanes and helicopters operated pursuant to CAR 406, in large aircraft operated pursuant to CAR 604, and in aircraft operated pursuant to Part VII, shall be overhauled at the intervals recommended by the engine manufacturer, or in accordance with an alternative hard time interval or an engine on-condition maintenance program approved in accordance with Appendix D.

Information Note:

No hard time, including calendar time, between overhauls need be observed in the case of small aircraft reciprocating engines in non-commercial private operation."

[Colonel Sanders]

I really wish people would stop telling private aircraft
owners that their engines have to be overhauled at
TBO. I'm constantly educating people about that.

If nothing else, TBO is more than just air time - it is
also calendar time. Depending upon the manufacturer,
after 12 years or so, every engine is "beyond TBO"
regardless of air time. That must include the majority
of privately-owned aircraft in Canada, not all of whom
are contravening the CARs.

No one cares, but the condition of a privately-owned
aircraft engine is a function of how long it HASN'T flown,
rather than how long it HAS flown, which is what everyone
thinks is bad for it.

Plenty of private aircraft engines are trashed due to
internal corrosion from lack of use, at a fraction of
air time TBO. This is caused by the length of time that
they DIDN'T fly - they were NOT worn out by the time
that they DID fly.

Decades ago, I flew a twin with 5500 SMOH on one
of the Lyc engines. Ran just fine. They just kept changing
jugs and accessories. Flew all the time. Which was
NOT bad for it!!! During my visit to that operation,
I flew 105 hrs in 21 days. You do the arithmetic. That
kind of operation gives you engines that last thousands
of hours beyond TBO.

About 20 years ago, I flew with an outfit in Atlanta, GA
which did simulated air-to-air in T-34's. They flew them
really hard - ripped a wing off, after I left. Anyways, they
had TCM IO-550's installed. After 2600 hours, they got
nervous and pulled an engine - and EVERY PART was within
service (not new, but service) limits.

They did not "baby" their engines, the way people here will
tell you to do. They flew it hard, and flew it often. 'way
past TBO. They might have broken up the airframes, but
the engines loved it. No cold starts. Flew every day.

People don't understand that it doesn't hurt an engine to
produce torque at rated RPM. What hurts an engine is
running it hot. If you keep the CHT's and EGT's down,
the engine will last a long time. If you run high CHT's
and EGT's, well, the metal is going to wear out sooner -
regardless of the horsepower being produced.

Keeping engine temps down has far more to do with
condition of engine baffles and seals, rather than the
power setting, but no one cares.

[InclinePlane]

Airworthiness Notice - B041

http://www.tc.gc.ca/eng/civilaviation/s ... 41-549.htm

[Colonel Sanders]

Sigh. That's for commercial operators, not private owners.

It never ends.

[iflyforpie]

After 2600 hours, they got
nervous and pulled an engine - and EVERY PART was within
service (not new, but service) limits.

FWIW, that's all an overhaul is. Pull the engine apart, measure everything, if it's all within service limits it goes back together for overhaul period.

If you want new limits, you have to cough up for a factory remanufactured or new engine.

[newbiewings]

Colonel Sanders,

Thank you for that insight about Manufacturers TBO vs what's really important... I'm slowly learning the mysteries of aircraft and flying.

I'm working on my PPL, and hope to own in the reasonably near future. Now is the time to learn about ownership, before it gets expensive!

[Heliian]

TBO= time between overhaul

Life limit= calendar or airtime limit of a part as dictated by the manufacturer or an AD, once it has reached it's life limit then it is to be scrapped or quarantined, they can no longer guarantee that that part will not fail.

Some turbines are on-condition but contain parts that have life limits that must be replaced.

Piston engines can fail when they are 0 hrs or 5000000 hrs, but the manufacturers recommend an overhaul schedule to try and prevent any failures.

Every time the crank turns, parts are wearing.

[photofly]

TBO= time between overhaul

Life limit= calendar or airtime limit of a part as dictated by the manufacturer or an AD, once it has reached it's life limit then it is to be scrapped or quarantined, they can no longer guarantee that that part will not fail.

If only. Aside from some very limited factory warranties (which don't go anywhere near TBO) the manufacturer definitely doesn't guarantee that the part will not fail before its life limit.

[Heliian]

What i meant by guarantee is that the part has proven to be reliable to that life limit and then some and shouldn't fail under normal use. In some cases, life limits have been extended once field testing proves further reliability and in others, life limits have been reduced.

no warranty implied.

There is no substitute for proper maintenance and inspections, that is what engineers do and that is why it's regulated by the governments, otherwise most GA owners wouldn't do anything.

[Colonel Sanders]

Every aircraft owner needs to know that every single
part of his aircraft is always "on condition". At any
moment, it could fail and need repair or replacement.

This is especially true of anything with moving parts
but is also true of stuff that doesn't move.

Some people think that an airplane only needs maintenance
once a year, and that something magical happens at
the annual. What nonsense. The defer all their snags
which is unsafe and illegal and makes the annual a long,
expensive nightmare. Madness.

When an airplane breaks, fix it. An annual inspection
should be just that - an "inspection" of the condition
of the aircraft. Not a frikken rebuild.

Note that an airplane can break in one of three ways:

1) it fails on you. Obvious. e.g. a magneto is dead.

2) a failure is caught during inspection. e.g. cracking,
corrosion, wear, etc.

3) regulatory. An Airworthiness Directive arrives in
the mail, and your airplane is a collection of parts
until you comply with it. An AD may require that
you change part or all of your engine, prop or airframe.

[photofly]

What i meant by guarantee is that the part has proven to be reliable to that life limit and then some and shouldn't fail under normal use. ...
no warranty implied.

Ok, but let's use a different word than "guarantee", then, because its natural and dictionary meaning is other than what you intended.

[iflyforpie]

It's based on MTBF.... or Mean Time Between Failures.... usually with a healthy margin.

When they designed the thing and ran it through its certification tests, they came up with a number that would ensure a high percentage of the engines would make it though based on average operating conditions.

But many things, the calendar age of the engine, how it was operated (preheat, oil changes, operator techniques), where it was operated, how often it was operated and for how long, and even variations in materials and tolerances all have big effects on how long an engine will last.

In the typical entropic (?) order to chaos world we are used to dealing with, we would expect that the engine will deteriorate and become more likely to fail as time goes on... forming an exponential curve for likelyhood of failure as time goes on

But in recent years, we've been paying a lot more attention the 'infant mortality' aspect of engine failures. Better and more thorough investigation techniques (often headed by insurance companies and lawyers in the Litigious States of America) expose the use of substandard materials and construction techniques in new engines, resulting in numerous ADs and SBs on these engines while the ones overhauled in the 1960s and 70s are not applicable.

This changes our exponential curve into an inverse bell curve.... with the most risk of failure at the very beginning of TBO and towards or significantly beyond the end of TBO.

I am always more cautious with a new engine than one that has several hundred or even thousands of hours on it.

The next thing is that there are factors that are unrelated to TBO that might make it worthwhile to overhaul it early or shortly after TBO. A leaking or cracked case close to TBO might not be worth putting back together without an overhaul. Same with a prop strike or immersion.

[Heliian]

What i meant by guarantee is that the part has proven to be reliable to that life limit and then some and shouldn't fail under normal use. ...
no warranty implied.

Ok, but let's use a different word than "guarantee", then, because its natural and dictionary meaning is other than what you intended.

how about "confidently assure" and yes they pretty much guarantee it's service life and if it fails during normal ops before that then there is usually an SDR and much squaking to the company in question. No manufacturer wants premature failures of life limited parts.

[photofly]

.

[PilotDAR]

A "life limit", should there be one applicable to any part of your aircraft, will be expressed as an "airworthiness limitation". This means that when any of the limits (hours in service, cycles or calendar time) are reached, the part is no longer airworthy in the legal sense, regardless of condition. Therefore you must replace it.

You might have an expectation that it will not fail catastrophically during that time, but it might wear out and be unairworthy anyway.

It is uncommon for older GA aircraft to have airworthiness limitations, though I suppose that a life limited ELT battery would qualify....

[Defy Gravity]

I was always curious about:

Is an aircraft engine actually more reliable then an automobile engine?

Man I know guys that just abuse their auto engine and never have it quit. And I mean like zero oil changes, never warming it up before driving in the winter, just ripping the sh*t out of it....still it keeps on ticking.

Rarely do you hear of a family driving along the highway and the engine failing internally. And that could be a beater that's 15 years old or more.

Are the weights of auto and aircraft engines similar? (if both have the same HP)

Is the auto engine built tougher?

I can understand though if an aircraft engine is not used on a regular basis and internal corrosion being an issue.

[Colonel Sanders]

You are comparing apples and oranges.

Airplane engine runs at 100% during takeoff and climb,
and 65% power continuously thereafter.

Car engine never runs at 100% and continuous might
be 10%.

Porsche tried to adapt a car engine for an airplane - see
PFM - and it was a disaster.

[Colonel Sanders]

Dup

[iflyforpie]

I was always curious about:

Is an aircraft engine actually more reliable then an automobile engine?

Man I know guys that just abuse their auto engine and never have it quit. And I mean like zero oil changes, never warming it up before driving in the winter, just ripping the sh*t out of it....still it keeps on ticking.

The tolerances for keeping a car engine in service are much lower than an aircraft engine. We aren't doing a compression check every 10,000 km on a car engine like an aircraft engine. We aren't checking the oil filter for metal either at every change.

Rarely do you hear of a family driving along the highway and the engine failing internally. And that could be a beater that's 15 years old or more.

You don't hear about it because it doesn't involve a forced landing and a bunch or personal harm or property damage. A quick search of YouTube finds tons of cars blowing rods.... and those are just the catastrophic failures that happen to be captured or allowed to happen.

Just look at how often you see a car on the side of the road. If it is abandoned, chances are it was something more than a flat tire, bad belt, or lack or fuel.

Are the weights of auto and aircraft engines similar? (if both have the same HP)

Yes and no. The car engine itself usually has better power to weight, but requires a gearbox, cooling system, and electrical system to make it functional. The Porche PFM CS alluded to wound up producing less HP per pound of installation than the aero engine it was supposedly superior to.

Is the auto engine built tougher?

Again, yes and no. Auto engines have very few limitations on weight, are built to tighter tolerances because they are liquid cooled, and spend most of their time running at low RPM and a low percentage of their power

Aircraft engines must be light. They must also be simple which usually means direct drive and air cooled. Direct drive has the advantage of keeping engine RPM low, but that means it is more difficult to get power out of it--a 5.9L IO-360 only makes 200 HP (actually, not too far off a Dodge 360 back in the early 80s ).

Air cooled means tolerances are looser, so aircraft engines don't like running cold and constant power changes (a car engine only needs 15 seconds to have the combustion chambers up to temp, even though your coolant gauge is at zero).

[LV2FLY2]

Air cooled means tolerances are looser, so aircraft engines don't like running cold and constant power changes (a car engine only needs 15 seconds to have the combustion chambers up to temp, even though your coolant gauge is at zero).[/quote]

Well I have to disagree with "Air cooled means tolerances are looser". All engines (except marine) are air-cooled one way or another. Tolerances have nothing to do with cooling the engine. Most aircraft engines transfer the heat from the cylinders directly to the passing airflow via "cooling fins" located on the cylinders and cylinder heads. Liquid cooled engines have "jackets" that surround the cylinder and transfer the heat from the cylinder through the liquid to the radiator where the passing air flows through "cooling fins" in the radiator core (like cooling fins).

[iflyforpie]

Yeah, and you could use the same argument that all engines are liquid cooled, since we use oil as a coolant.

No, the cooling classification is what type of cooling is used to cool the cylinder sleeves. There is no air anywhere near the cylinder sleeves of a liquid cooled engine. If by the loss of coolant there is air there, it won't keep the engine cool enough and it will seize.

Tolerances themselves may have nothing to do with how the engine is cooled, but it has a great deal to do with the effect each method of cooling has on the engine.

For example, most aircraft engines have what is known as a 'choke bore' which means the cylinder gets narrower at the top. At proper operating temperature, the hotter top part of the cylinder expands so the bore is even while the aluminum piston expands (the coefficient of expansion of aluminum being greater than steel) to provide a good operating clearance.

When an aircraft engine is cold, the aluminum piston fits in very loosely and even more loosely at the bottom due to the wider clearances. If you operate it at high power settings when cold, you will get piston slap, which will result in scoring of the piston and in extreme cases shattering of the piston skirt.

In liquid cooled engines, with the large amount of cooling available to all parts of the cylinder in all phases of operation (idle, full power, different speeds), it is not necessary to make the tolerances loose. It is very rare to see a coolant gauge move on a car once it has got up to temperature, but an aircraft engine can vary as much as 100F in normal operation.

[Alberta_Canada]

I think comparing modern auto engines to aircraft engines is a bad comparison. Modern automotive engines run on much tighter monitored systems than what any piston powered aircraft down at the flight school will run with. I would say an aircraft engine from the 70s is much safer overall than any modern automotive engine. You can give me any car made today from any manufacturer and all I would have to do is install a jumper wire to create a short to ground in the HS-CAN network and you are left with a brick on wheels. Take out that network and none of the modules can talk to each other. The dash will look like Christmas with all the warning lights. Sometimes the car will start but you'll be very lucky to get anywhere. The PCM, TCM, airbag module, anti-lock brake module, 4x4 module, occupant classification module, even the fricken radio in most cases will be INOP and you'll be left will a pile of crap and any technician who loves electrical work is going to smile from ear to ear to hunt down where the haphazardly placed network wire has gotten damaged.

[Colonel Sanders]

I have been attacked endlessly for decades by legions
of non-flying proponents of car engine conversions
for airplanes. I call them penguins - you know, birds
that flap their wings but never fly.

I have a simple request for all those fanatics, who's
decades of effort have produced nothing:

Take a 172, cut it's alternator belt, and go for an
hour's flight.

Now cut the alternator belt of your car-engine
homebuilt, and try to go for an hour's flight.

Get back to me on how that works out for you.

Flying with a car engine is a really good way to
kill yourself. It is very, very high risk. I have done
it and I don't enjoy it. In comparison, surface acro
in the Pitts or L39 is far less hazardous.

The engineering on most homebuilts is really
substandard. The engineering on an auto engine
conversion for an airplane, needs to be really, really
good. Better than Porsche's.

Can you really do better engineering than Porsche?
I highly doubt it. This is why 99% of the flying
homebuilts out there have a Lyc or TCM.

[Alberta_Canada]

The homebuilts that really scare me are the ones that use GMs Vortec 4.3L engine. That thing was a turd on the best of days. It is very rare to see one make it to 200,000 kms before spinning a rod bearing.....most of the ones I've seen die in the 150-170,000 km range. Intake gaskets leak coolant into the oil and wash the bearings. I had a Blazer with that engine and it left me stranded in Strathmore with a spun rod bearing and I maintained it religiously. I can't believe people have actually put that thing in aircraft. Even if I won an aircraft equipped with that engine I don't even think I'd fly a single circuit with it. A stopped prop from a dead 4.3L kind of looks like a bowtie. That would be a painful last image for me to see. I wonder if "comb mullet" is added to the pre-takeoff checklist of a chev powered aircraft?