noc19-ae02 LEc 27 – Checklist for Aircraft Reciprocating Engine Maintenance
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noc19-ae02 LEc 27 – Checklist for Aircraft Reciprocating Engine Maintenance

August 31, 2019

Hello, so far we have read about the, construction
of the engine, reciprocating engine. We have seen different parts, in the engine. We have
seen an engine in an open condition, in a dismantled condition. We have read about the
fuel system, the different types of fuel used, the different components in the fuel, what
are the inspections, we carry out in the fuel system. We read about the induction system,
about the exhaust system, the different components, in the induction system and the exhaust system.
And the maintenance inspections, which are required to be carried out in these systems,
apart from this, we also read about the exhaust system, the ignition system, in addition to
this we have done an engine ground run. We saw the different checks, which are to be
carried out, during the ground road and some of the maintenance, actions some of the maintenance
schedules, which are required, at different intervals, as recommended by the manufacturer.
We have seen, the daily inspection, we have seen the 50 hours of inspection, 100 hours
of inspection, 200 hours of inspection, one year of inspection, on the engine on a reciprocating
engine. Now there are a few points, general points, which we need to keep in mind while,
we are maintaining an engine, in order to get ultimate output from your engine, in order
to complete the engine life, it is very important that the some basic points, should be kept
in mind, if we follow these points and we follow the instructions, recommended by the
manufacturer, we are sure to get the complete life of an engine. And a trouble-free life
of an engine. So, let us see here, what are these general points, some very basic points,
some very points well, if we as a maintenance personnel keep it, in our mind and we follow,
that then the engine, is most likely give to give us a trouble-free operation. So, let
us see, what are these general points, in this small chair. We are showing you, some
of the slides, some of the basic, point’s different types of engines and what are the
tests and inspections and what are the some, what are some basic points. We need to keep
in our mind. So, let us see, what is it all about? Now coming to the reciprocating engine types,
various types of engines, during our course of the different lectures. We have come across,
these terms, we have also mentioned about, these engines and let us see the em one by
one, first is the normally aspirated engine, what is a normally as pirated engine? They
are the ones that are not supercharged or turbocharged .We have read about the supercharged
engines, we have read about the, turbocharged engines. So, normally aspirated engines are
the ones, which are not supercharged or turbocharged if an, aircraft has a manifold pressure gauge,
at full take off power, at sea level, on a standard day. So, on a standard day, at sea
level, at full takeoff power, it would indicate a manifold pressure, reading of approximately
29 inches of mercury. So, in case of normally aspirated engines, on a standard day, at sea
level at full takeoff power, manifold pressure gauge will read 29 inches of mercury. The
normally aspirated engines, use atmospheric pressure and thereby altitude limited. So,
these normally aspirated engines, they are altitude limited, because they are using atmospheric
pressure. Next is direct drive engines, these are engines, in which the propeller is bolted,
on the end of the crankshaft. So, on the direct drive engines, they are
the best in powered engines, where the propeller is bolted, on the end of the crankshaft and
the propeller turns at the same, speed as the crankshaft. Now what is a geared engine,
geared engines are usually the higher powered, more complex engines, using a reduction gear
on the nose of the aircraft. So, these geared engines they are higher power engines, more
complex engines and they are using a reduction gear, on the nose of the aircraft and with
the propeller attached to it. So, in between the propeller and the crankshaft, you have
a reduction gear, attached as a result the propeller will turn somewhat slower, than
the crankshaft, resulting in a lower propeller noise level. So, because of this reduction,
gearing the propeller will turn at a slower, rpm fast compared to crankshaft and will also
result in lower, propeller noise level, when the engine is geared, the engine designation
precedes, with a g’ now, now every engine, has been given a model number, it has it has
been designated a model number, for example, any number in case of geared engines, will
be preceded with a G, G stands for geared engine, thus a geared opposed normally, aspirated
engine, with a 480 cubic inch displacement of the cylinders, would be designated as GO
dashboard 8 0 model. So, G stands for, your geared engine, o is for a post or horizontally
opposed engine and 4 8 zero is the 480 cubic inch displacement of the cylinder. So, this
is how the engine model, is designated. Next is your turbocharged engine, it consists
of a turbocharger unit, with a small turbine wheel, attached by a common shaft to a compressor
wheel. We have read earlier about turbocharged engines, just to brush up it is it consists
of a turbocharger unit, with a small turbine wheel, attached by a common shaft, to a compressor
wheel and utilizes the engine exhaust gas, by directing it over the turbine wheel, to
drive the compressor. So, the exhaust gases are being driven, over the turbine wheel to
turn drive the compressor, the horsepower loss in operating the turbocharger, is negligible
turbocharging, can provide, greater utility to the piston engine by providing, sea-level
horsepower, in some models, as high as twenty thousand feet or it can be used to add horsepower
to the engine, particularly for takeoffs. So, turbocharged, ding will add power, to
the engine especially for takeoffs and it can also provide sea level horsepower, at
higher altitude, the faster the engine runs, the more air the turbocharger can pack into
the cylinder, to compensate for the thin air of altitude or to increase the horsepower.
So, the faster the engine runs, turbocharger will provide more power, into the cylinder
to compensate for thin air, of altitude ,because we know that as, we go up as altitude increases,
air thins down. So, in order to compensate, for the thinning of air at altitudes, turbocharger
will provide, compressed air and it will increase the horsepower. Next is your supercharged engine, now supercharged
engines ,they use a compressor wheel, to pack air into the cylinders, these superchargers
they are also, using a compressor wheel, to pack air into the cylinders, but the compressor
is driven by the crankshaft, through an intricate gearing system. So, in this case the compressor,
is being driven by the engine crankshaft, through a gearing system, which takes considerable
horsepower from the engine to operate, in comparison with a turbocharged engine, it
is a medium altitude powerplant. So, as compared to turbocharger, turbocharged engines, supercharged
engine, is a medium altitude powerplant, turbocharged engines are more widely used, as compared
to supercharged engines, because of the advantages that turbo charging offers. Now because turbo
charging, turbo charges they have more number of advantages, as compared to supercharged
engines. So, turbocharged engines are more widely used, in the industry, a supercharged
geared opposite, opposed fuel-injected engine with cylinders of 540 cubic inch displacement
is designated as IGSO 540 model. So, I is for injected, fuel-injected engine, G is for
geared engine. S is for supercharged engine. O is for horizontally or post and five four
zero is the cubic inch displacement, of the cylinder and this is how it is designated
as IGSO dash five four zero model. S represents supercharging. So, this was about the different
types of engines, different types like normally aspirated engines, direct drive engines, geared
engines turbocharged engines. So, much our engines different types of reciprocating engines.
So, this was just to brush up, what we had read in our earlier lectures. Now as the engine life, increases, as the
number of hours, number of operating hours of the engine increases, the deterioration
is bound to occur. And as the engine approaches, it’s life, we as maintenance personnel and
we as operators. We should keep a very close watch, on the engine and the help of the engine.
So, what are the different points that basic points that will give, us an idea of the engine
health, let us see what are these points? Now determining engine condition, as an engine
builds operating us and approaches, TBO, which may be either the manufacturer’s recommended
operating hours or a calendar year limit before overhaul, the question arises concerning the
condition of the engine. How the manufacturer has, fixed an engine life, on the basis of
the operating us, as well as the calendar period. So, the life of the engine, on the
basis of operating hours and calendar life should be closely monitored. And as it approaches
its life, suppose the life is two thousand hours or twelve years, whichever is earlier
and your engine is about, to complete two thousand hours, but the calendar period is
say only five years, in that case also we need, to close watch the condition of the
engine or the case maybe your, engine has just completed 500 hours, but your calendar
period is approaching 12 years, in that condition also you need to keep a continuous watch on
the health of the engine. A quick reference checklist to help determine
the engine health is a following. First is oil consumption, any unusual increase, we
need to see, whether the engine oil consumption has increased or there is an unusual increase,
engine history and calendar age, we need to consider the history of the engine, how the
engine has performed, in the previous operating hours and what is the calendar age of the
engine? How has the engine being operated? How the engine has been operated, pilots opinion
of the engine, the pilots who are flying the engine, flying the aircraft, what is their
opinion about the engine? Maintenance what kind has the engine received? Very important
over the period of time how the engine has been maintained, whether it has been maintained,
as per the manufacturer’s recommendations, approved procedures and approved materials,
have been used, what does the oil filter tell, very important we will see about this, what
has been the trend in compression checks. Compression check, we have seen in our previous,
lecture how the compression check is carried out, why is it carried out and what is the
trend, in the compression checks. We need to keep a watch and what do the spark plugs
show. And also the condition of the spark plugs. So, these general points, they can
tell us about the health of the engine, oil consumption engine history and calendar age,
how the engine has been operated, pilots opinion of the engine maintenance what kind of engine,
what kind has the engine received? What does the oil filter tell compression check trends?
And the spark plugs condition. So, these general points, they can tell us about the condition
of the engine. Let us see one by one, oil consumption. First
is oil consumption, as a maintenance person we should be aware of general, history of
oil consumption, during the life of the engine. Yes because since, we are maintaining the
aircraft, we are maintaining the N and an engine. We should be aware, of the general
history, how the oil has been consumed by this engine, in case it has been within the
limits, it has been normal throughout the, life or it has been erratic or it has off
late the oil consumption has increased. So, we should know, the trend of oil consumption,
a possible danger signal, concerning engine health, is a definite increase, in oil consumption
during the recent, 25, 250 hours of flight time. So, in case if the oil consumption,
has very recently increased in the last 25 to 50 hours ,if it has drastically increased,
then that is a possible danger sign and we need to keep a proper watch on it. And we
need to take corrective actions, as recommended by the manufacturer, the oil screens and filters,
should be carefully observed for signs of metal. So, the oil filters and the screens,
they should be very closely washed, they should be observed for any signs of metal, to see
whether there is anywhere in the internal, construction of the engine, a differential
compression, check should also be carried out. So, in case if you have seen that the
oil consumption has, drastically increased, in the last 25 to 50 hours, we need to check
the oil filters, we need to carry out a differential compression check, inspect the air filter
for cleanliness where and proper fit. So, apart from checking the oil filter and doing
the compression check, we also need to inspect the air filter, for cleanliness wear and proper
fit. This is all the more important, when operating in dusty areas and definitely could
be a cause of increased oil consumption. Now in case if your aircraft is operating, in
dusty and sandy conditions, in that case the engine is getting, more dirt inside and in
case if your filter, is clogged or your filter, is damaged that means more dirt is going inside
the cylinder, your engine is getting unfiltered air and that can be a cause of oil consumption.
So, we increase oil consumption, it has a very important thing, we need to keep a watch
on the consumption, of the engine, during the entire life of the engine and that oil
consumption trends, we need to see and in case if there is a drastic increase of oil
consumption, in the recent twenty five to fifty hours. That should be seen and certain
checks should be carried out, oil screen and filters should be checked compression, check
should be carried out. And air filter, should be cleaned or replaced as the case may be. Next point, to see the engine history and
calendar age. We should see what the engine history is and what is the calendar age? If
an engine has been basically, healthy throughout its life, this would be a favourable factor
in continuing to operate, it as the engine approached high time. Now in case if the engine
has operated, satisfactorily throughout its life. And there is no abnormal, indication
then we should be satisfied and it is most likely that the engine will complete its life
alternately, if it has required frequent repairs, the engine may not achieve its expected normal
life. Now in case, if the engine or its operation operating life, has required frequent repairs,
frequent maintenance than in that case it is not likely that engine will achieve, its
expected not normal life. Another important aspect of an engine’s history would be its
calendar age, engine flight time and calendar age are equally important to the operator.
So, the calendar period, the calendar life of the engine, is also very important and
engines infrequently, flown do tend to age or deteriorate more quickly, than low slowed
on regular basis. So, a very important point we will cover this point in detail, in our
further slides that any engine, which is not being operated frequent, frequently is likely
to deteriorate more quickly, than those flown on regular basis, thus manufacturers recommend
both an operating hour limit and a calendar error limit between overhauls. So, that is
why the manufacturers they will recommend the engine life, on the basis of the operating
hours as well as the calendar period, for example the life of the engine of Cessna 2:06
what aircraft, we have been watching in our videos, is $2,000 12 years whichever is earlier.
So, that means 2,000 of operating hours or twelve years of calendar period, whichever
is earlier operation. The basic question is how the engine has been
operated, the majority of its life. Now how the engine has been operated, how the pilots
have handled this engine this that is also a very important point, to be considered while
analysing the health of the engine, some engines operate continuously at high power or in dusty
conditions, could have a reduced life. Now it depends where your engine has operated,
in case if it has been operated in dusty conditions or in case it has been operated continuously,
at high power operations, then in that case also your engine could have a reduced life.
So, very important how the engine has operated, during its, service life likewise, if the
pilot hasn’t followed the manufacturer’s recommendation, on operation, it may cause engine problems
and reduce the expected life. So, very important point also, the pilots, the operators, they
need to follow, the instructions by the manufacturers and all these instructions are mentioned,
in the pilots operating handbook and all the instructions the manufacturers recommendation,
need to be followed and in case if the pilot has not followed, these recommendations, then
the engine will have faced problems and will and is expected to have, reduced life. Next
very important point is the pilot’s opinion of the engine, now the person who is operating,
who is flying the aircraft? Who is handling the engine? Who is handling the machine? What
is what his feeling about the engine? That in that opinion of that person is also very
important, whether during the course of operation, he is comfortable, about the engine whether
he is confident about that engine or not that opinion is also very, very important. The
pilot’s opinion of the power plant, based on experience, operating it is another important
point, the pilot’s opinion and confidence in the engine is based on, whether it has
been a dependable power plant. So, over the period of time and the power when the pilot
is operating an engine, he develops confidence, in that machine and whether during the entire
service life, the person has felt confident about that machine or not that opinion is
very important, while ascertaining the health of the engine. Next is the maintenance a very, very critical
point, very important point, good maintenance should aid in achieving maximum engine life,
alternately poor maintenance, tends to reduce the expected life. Now this is a very general
point, we all know that if we maintain, a machine a good maintenance is carried out,
it is going to achieve maximum life and in case of poor maintenance, it will reduce the
expected life, the engine logbook should properly reflect the kind of maintenance, provided
to the engine. Now whatever maintenance actions have been carried out, on the engine, they
have to be entered in the engine logbook and these engine logbooks, they are the legal
documents and they are the proof, but that whether the machine has been maintained properly
or not. So, these records should also be viewed, to ascertain the health of the engine. Now
coming to the other maintenance, aspects let us see, what does the oil filter tell? So,
as we know that oil is a very important thing, it is the lifeline of an engine. And the oil
filters they are very, very important components of an engine. So, let us see what does the
oil filter tell? Clean oil has consistently been an important factor, in aiding and extending
engine life. So, clean oil that is very important for an engine, to give it a full life a good
full flow oil filter, has been a most desirable application here. When the filter is exchanged
open it and carefully examine for any foreign elements. Now when this filter, is replaced
when we remove the old filter, put a new filter, the old filter, the old oil filter should
be opened and the element inside should be carefully examined, for any foreign elements.
The engine oil screen and external oil filter, tell us the story about the help of an engine.
So, the condition of the filter element, tells us the story, about the health of an engine,
in case if you observe any particles metal particles or that means that is an indication,
somewhere is happening inside your engine and you need to take corrective action. The
oil changes should have been, accomplished in accordance with the manufacturer’s recommendations
and should also have been recorded in the engine logbook, engine oil replacement, generally
the manufacturers they say 50 hours or four months whichever is earlier 50 hours, of operating
time or for calendar months, whichever is earlier. So, the engine oil change, is a very
important point, to be considered while, maintaining an engine, we should be very strict about
it and the engine oil should be replaced, strictly at 50 hours or four months, whichever
is earlier, in case if we follow this, we are we should be comfortable, about the engine. Next is the compression check. We have seen
in our previous lecture how, we carry out a compression check, now let us see why it
is important and this compression check, is also a very important test, to see the health
of the engine. What has been the trend in compression in at least the last two differential
compression checks? So, in the last two compression checks, what readings we have observed that
should be checked that should be observed, whether there is a drastic change in the compression
check readings or not, the differential compression check is the more reliable type and should
be taken on a warm engine. Yes we know that it has to be taken on a warm engine, if the
differential check reveals 25% loss or more than trouble may be developing. Now in case
if you are observing a loss of 25% or more that indicates that some is about to come,
a compression test should be made anytime, faulty compression is suspected, any time
pilot observes a loss of power in flight, when high oil consumption is experienced or
when soft spots are noticed while hand pulling the propeller. So, these are the occasions
when we are required to carry out a compression test, whenever you observe a faulty compression
or you suspect a faulty compression, any time your pilot is observing, a loss of power in
flight, whenever you observe high oil consumption or when you are turning the propeller, by
hand you experience, some soft spots. So, in these conditions, you are required to carry
out, a compression check apart from these points compression check, is also required
to be carried out, at every hundred hours of operation and every hundred hours of schedule,
we are required to carry out, a compression check of the engine, to ascertain the health
of the engine. The differential compression check is best used to chart a trend, over
a period of flight as a gradual deterioration, of charted compression, taken during maintenance
checks would be a sound basis for further investigation. So, whatever readings are being
observed, in the compression check, we need to record them and we need to, watch and analyze
these readings, very close very closely to ascertain, the health of the engine or a gradual
deterioration, of the engine and these readings should, be a sound basis for further investigation. Next is your spark plug. Now spark plugs also
tell us, lot of things about the engine. And these spark plugs up should also be, closely
observed and they should be analysed. The spark plugs when removed and carefully observed
tells us, what has been happening in the cylinders during flight and can be a helpful factor,
in ascertaining the engine health. So, these spark plugs, they also tell us what is happening
in the flight and they can also tell us about the engine health, in case if you observe,
copper run out and or lead fouling it means excessive heat. This is the first indication
if in case copper run out or lead fouling is observed that means excessive heat, in
case black carbon and lead bromide may indicate, low temperatures, in case if you see black
carbon or lead bromide on the, plugs then that indicates, low temperatures the type
of fuel being used and possibly excessive richness of the fuel metering at idle. So,
black carbon or lead bromide, that indicates that your mixture is on the richer side, the
type of fuel being used and also may indicate low temperatures. Now in case if the plugs
show us, oil fouling that indicates that your piston rings are failing, to seat or excessive
beer is taking place. Now if the plugs are showing you, we fouling that means your rings
are not sitting properly or there is excessive wear on the piston rings, the normal color
of a spark plug, deposit is generally brownish gray, in case if you observe a brownish gray
color of deposit that on the spark plug, that indicates, that it is of normal color and
which it is a normal operation. In high compression and supercharged engines, cracked spark plug
porcelain, will cause or has been caused by pre-ignition. So, in case of high compression
and supercharged engines, if your spark plug porcelain has cracked, then it is because
of preignition or it may lead to preignition. So, these were some of the points to, ascertain
the health, of the engine and we should continuously keep a watch on the engine health, while we
are maintaining, we should continuously analyse all these points, the oil consumption engine
history, how the engine is being operated, what is the pilots opinion, of the engine
what kind of maintenance is being done? What are the oil filters telling us? What has been
the trend in the compression checks? And how the what are the spark plugs telling us? So,
these are in general points to be observed, while maintaining an engine to ascertain the
health of the engine. Another very important tool, to observe to
be observed and to ascertain the health of the engine is oil analysis, whatever oil samples
we are taking, we need to analyze, these oil samples and we have to carry out an oil analysis,
to understand the health of the engine, oil analysis is used as a tool for helping to
determine engine condition, the object is to examine oil samples, from an engine and
break down, the sample in parts per million in order to determine the internal health
of the engine. So, the internal health of the engine can also be determined, by taking
the oil samples from the engine, by testing these samples and these samples they are broken
down, in parts per million, to determine the internal health of the engine. This is based
on the fact that all lubricated engine parts, where and deposit a certain amount of metallic
particles in the oil. So, the basis of this analysis is that all the lubricated engine
parts, will wear and they will deposit, a certain amount of metallic particles in the
oil, the number of particles per million, of each metal determines, the wear pattern
for the particular engine being analysed. It is of the utmost importance, to understand
that the result of the analysis is only pertinent to the engine, being analysed. So, very important
we need to understand that, the report is for that specific engine and whatever analysis
is being made, is for that specific engine. The fact that is important is a sharp rise,
above normal of the amount of a particular metal in the oil. So, in case if there is
a sharp rise, in the amount of a particular metal, that is to be observed, it is imperative
then to build a case history of each engine we’re in a sharp rise in one metal will indicate
abnormal, engine wear. So, we need to observe the samples, we need to have data of that
engine, of all the samples I need to observe that how that particular metal wear, has increased.
The analysis can also tell you, whether the oil contains other liquid contaminants such
as gasoline or water. So, this analysis can also tell you, whether the samples they have
gasoline or water also in it. Refer Slide Time 🙁 31: 57)
gasoline contamination of the oil canresult from blow-by, from the combustion chamber,
caused by poor combustion, backtime bring, in proper fuel make sure wornrings. So, this
gasoline contamination, this can occur, because of these reasons blow by from the combustion
chamber, workon combustion, back typing, improper fuel mixture, of worn rings. Water condom,
contamination is usually restricted to condensed vapour, but this, vapour combines with the
fuel, combustion products, toform harmful, metal attacking assets. So, this is very important,
in case if thereis water contamination, it is mainly dueto condensed vapour, but this,
vapour will combine with the fuel combustion products, to form harmful metal attackingacids.
Based on this contamination in theoil, the analysis will be able to pinpoint, improper
mixture, poor maintenance etc. So, this analysis will help us, intelling, whether your, you
are operating,on an improper mixture or poor maintenance is being done, differences in
manufacturing processes may cause avariation in analysis results for different engine models,
the amount oftin plating, copper plating, nitriding etcetera, performed during manufacture
has a definite relationship, to the oilanalysis reports. So, different manufacturing techniques,
processes areused and because, of these difference, different techniques, different processes,
the and there will be a variation in analysis results and it all depends among the upon,
the amount of plating: that is done, on these, components during manufacture.So, we have
to, take this also, into consideration, when, we prepare these oil analysis reports.
Refer Slide Time 🙁 33: 55) It is not uncommon for example, to see, what
seems, to be highcopper content early, in the life of an engine, only to have this content,
continually decrease, as the engine accumulates time and then, disappear together. So, in
some cases, you will find that, some metal, is there, in large quantity, in the early
stages and it gradually tapers off and gradually finishes, because in the initial condition
when the condition is new, you, you can observe somewhere and gradually,it will finish, it
will disappear. Poor air filter maintenance, running the aircraft on the ground with carburettor
or alternator, air on and holes, in the air intake system, are all factors, whichallow
an engine to ingest dirt and foreign matter. So, we have read about this earlier, in our
earlier slide also, in case if your air filter, is faulty, is clocked or is damaged, we or
your air intake system, there are holes in the heiress’s intake system, you run the aircraft
on ground, with carburettor or alternate air on, then you are ingesting dirt and foreign
metalin the engine. The result of this will show up, as high, iron that is cylinder barrels
and chrome: that is piston rings content at the next oil analysis. So, I don’t know next
oil analysis you will come to know: that because of this dudinjection, wear has taken place,
inside the engine. Several samples taken at the regular oil change intervals must be analysed,
to determine the normal characteristics of an engine and also,the first few samples,
on factory fresh engines, will read high, as new parts are wearing in and conforming
to each other. So, over the period of time several samples are taken, at regular oil
engine intervals and the readings, should be analysed,to determine the normal characteristics
and in case, if there is an abnormal where, if there is because, of some deterioration:
that also, we need to see,in these reports. During the initial stage of the engine, when
the engine is new, in the initial stage, we may see: that there are new parts, more bearing,
is taking place inside and gradually, this bearing will diminish.
Refer Slide Time 🙁 36: 20) Excessive heavy wear of internal engine parts,
will showup traces, as traces in parts-per-million during analysis, long before detrimental flaking
or scouring takes place and almost always, before any outward indication of trouble.
So, these excessive heavy wear of internal engine parts, thisis reflected, as traces,
in parts-per-million, during analysis and at a later stage, itwill occur, as flaking
or scouring. This initial departure from normal is not, not usually, any reason, to clear
the enginedown and investigation and timely and appropriate corrective action, replacing
the air filter perhaps, by the operator,will usually result in trace elements, returning
to normal, at the next oilchange.So, during the reports, during the oil analysis reports
if we see: that there is some wear, then we need to understand, the where, the cause of
the wear and if the corrective action is taken then, in the next analysis report,we will
see: that the problem has been solved. If long TBO, are to be achieved,it is most important
that clean air be provided to the engines. So very, important point for an engine, for
a reciprocating engine: that clean air should go, inside the engine and for that reason,the
air filters are play a very important role.Thus oil analysis is a good tool, if properly used,
like any other tool, it is one of the many things that must be used to determine engine
health. So, we have seen, the different points, to ascertain, the engine health, apart from
the previous points, oil analysis, this is also a very good tool,if it is used properly
and this will help us, in determining the engine health. And these, things should be
done regularly, to keep a close watch, on the ended engine condition.
Refer Slide Time 🙁 38: 21) Now, next is the tradition and pre-ignition,
these are, we have read about them, earlier also, just to brush up, what does detonation?
What does pre-ignition? We need to be careful, about these conditions and this is just to
brush up, these points. Detonation there is a limit to the amount of compression and the
degree of temperature rise: that can be tolerated, within an engine cylinder and still permit
normal combustion. So, the degree of temperature rise, the amount of compression, there is
a limit:that can be tolerated within an engine cylinder. When this limit has exceeded, detonation
can take place. So,when you have, temperature more than that,which is, what is prescribed?
Or you have,more compression then, in that case,detonation can take place, piston engines,all
over are vulnerable to detonation, at high power output, because combustion temperature
and pressure are higher, than they are at low or medium powers. So, at high powers,
you will have high compressions and high temperatures and so, piston engines are vulnerable, to
detonation, at high power outputs. Leaning the mixture at high power can also, cause
it. Now in case, if we are operating at high power and we lean the mixture, in that case
also, detonation can take place. Unless detonation is heavy,there is no cockpit evidence, of
its presence. Light to medium detonation may not cause noticeable roughness, observer,will
cylinder head or oil temperature,increase or loss of power. So, the person who is operating,
an engine,whose flying? The aircraft, he might not notice it even, in case if it is my detonation
or it has light detonation, because that roughness or cylinder-head temperature or oil temperature
increase: that probably he will not be able to notice or loss of power. However, when
an engine has experienced detonation, evidence of it can be seen, at teardown, as indicated
by dist piston heads. So although, during the course of operation, the operator might
not be able, to understand whether,detonation has occurred or not, but,whenever the engine
is, still open, for over all or for inspections, in that case we will come to know: that the
engine has faced detonation, this will be indicated by ditched piston heads, collapsed,
wall heads, broken ring lines or eroded portion of walls, Pistons and cylinder heads. Severe
detonation can cause a rough, running engine and high cylinder head temperatures. So, in
case if detonation is severe: that can be felt and the operator will come to know, when
your engine will be start running rough and you will have high cylinder head temperatures.
So,Severe detonation, will be noticed, will be noticeable, but, light and medium, detonation
operator will probably,not come to know. Refer Slide Time 🙁 41: 45)
Next is pre-ignition, as the name implies, means that combustion, takes place within
the cylinder, before the timed spark jumps,across the spark plug terminals. So, before the spark
plug fires, before that if the combustion takes place, within the cylinder, that is
preignition.This condition can often be traced, toexcessive combustion deposits or other deposits,
such as lead, which could, call which caused local hotspots. So this is, because you have
excessive combustion deposits or other deposits such as lead and these deposits become local
hotspots and cause pre-ignition, detonation often leads to pre-ignition. So, first detonation
happens and then pre-ignition happens, however pre-ignition may also, be caused by high-power
operation, at excessively, lean temperatures. So, pre-ignition can also occur, because of
high power operation, at excessive lean temperatures. Pre-ignition is usually, indicated in the
cockpit by engine roughness, backfiring and by a sudden increase in cylinder head temperature.
So, in the cockpit also, you can get an indication, when your engine starts running rough, when
backfiring has happened or there is a sudden increase in cylinder head temperature. It
may also,be caused by a cracked wall or a piston or a broken spark plug insulator, which
creates a hot point and serves, as a glow spot. So, in case if the piston has cracked,
wall has cracked or your spark plug insulator has broken, this will create a hot point and
it will act as a glow spot. Specifically pre-ignition is a condition similar to early, timing of
the spark, pre-ignition is a serious condition in the combustion chamber and will cause burned,
pistons and tuliped intake walls.So, this pre ignition is basically, ignition happening
before it is actually, planned and it is a serious condition, inside the combustion chamber
and it can result, in burned pistons and tuliped it take walls. The best temporary in-flight
method for correcting pre-ignition and decorate, detonation are, to reduce the cylinder temperature,
by retarding the throttle and reaching the mixture, opening the cowl flaps or a combination
of all these. So while, you are flying, in that case, if you notice that, your cylinder
head temperatures have, have sharply increased or you experience engine roughness, in that
case, during flying,the best thing is to reduce, the cylinder temperature, you can do that,
by retarding the throttle, by enriching the mixture, by opening the cowl flaps or you
can do, a combination of all these. So, this will take care of these problems, of detonation
and pre-ignition. Refer Slide Time 🙁 44: 48)
Now, next very important point, to be considered, is in case, if your engine is not being operated
very regularly, in general as a,a conception is like if the engine has completed less number
of hours, the condition is considered to be good. But,this may not be the case always,
let us see, what happens? If your engine has is not operated regularly, what? How it can
affect,the health of the engine, engine information is usually, provided as hours of operation,
since new or from engine overhaul for example, 800 hours TSN, would indicate, then the engine
has flown for 800 hours, since new or from the factoring. 800 hours TSO would indicate:that
the engine has flown for 800 hours,since last overhaul. That means in case,if the your engine
rock book, reflects 800 TSN or 800 TSO: that means, your engine has completed, 800 hours
since new or 800 hours since overhaul. But, in case,if the manufacturer has recommended
the life, as 2,000 hours or 12 years, in that case as compared to 2,000 hours,800 hours,
will appear, as if your engine has not flown much and your engine condition is in a pretty
good State. But, unfortunately this is not always true, there has been a case where,
an engine with less than 600 hours since new was reported to be using oil, at the rate
of 2/3 squat per hour and losing oil pressure during flight. Now, there havebeen cases where
the engine, which had completed just 600 hours since new and it was consuming, oil at the
rate of 2/3 quarts per hour and it was losing oil pressure during flight. Now, investigation
was carried out, because the engine had just completed 600 hours since new and 1400 hours,
were still left,to complete the life and still the engine was giving such severe problems,on
closer examination it was determined that, deterioration and we’re had caused,metal contamination
throughout the engine. Now, when the investigation was done, it was found that there is little
deterioration and we’re and because of that, metal contamination throughout the engine
has, taken place. An engineoverhaul was necessary, at and itincluded replacement of items, such
asthe camshaft, oil pump gears and pistons.Now, the investigation revealed that, theengine
now, needs an overhaul and during the overhaul, major components like camshaft, oil pump gears
and pistons they need to be replaced. Now, the point was,why should an engine with such
less hours, since new be in this sad state. Now, this is a very obvious,point to understand,why
engine which, which was new and had just completed six hundred hours, why it has come in such
a bad state, on closer examination, the engine logbook reflected:that during the first ten
hours of service, this engine had averaged, less than fourhour, four hours of flight time,each
month. Now, when the records were, investigated records were removed, it was found that, during
the first ten hours of service, this engine has, on an average flown for four hours per
month. Now, the chances were that, there was some months, when the engine was not flown
at all. Refer Slide Time 🙁 48: 33)
So, during the first ten hours of operation, the engine had flown on an average four hours,
per month and there were cases, there were periods, when the engine had not flown, at
all four months. The manufacturer in one of its and service instruction states: that the
recommended TBO, is based on the use of genuine parts, average experience in operation and
continuous service. So, the manufacturer in its maintenance publications and its manuals
clearly, you see: that the engine is expected to complete; its complete life,only when,
you use genuine parts, when you have average experience in operation and it is continuously,
in service. Continuous service assumes: that the aircraft will not be out of service, for
any extended period of time. Now, this continuous service means that, the aircraft will be in
service continuously and it will not be out of service, for an extended period of time,
if an engine, is to be out of service for longer than 30 days, it should be preserved,
as recommended by the manufacturer. A very important point, very important point we need
to understand:that in case, if the engine is not to be in service for more than 30 continuous
days, in that case, the engine is required to be preserved, as recommended by the manufacturer,
we need to follow, the steps,which are map which are mentioned by the manufacturer in
their manuals, we need to put, the material whatever, lubricants, there is a proper procedure,
for preservation, which is mentioned in the maintenance publications. And engine,which
is not flown frequently, is subject to deterioration, as a result of inactivity. So, as a result
of inactivity,the engine will deteriorate, when the engine does not achieve flight operating
temperatures, on a regular basis, the moisture and acids that form, as a result of combustion
and condensation, are not vaporized and eliminated through the exhaust and crankcase breather.
So very,important point to understand, when the engine is not operating, on flight temperatures,
on regular basis, then the moisture and acids: that form, because of combustion and condensation,
they are not vaporized and eliminated through the exhaust and crankcase breather. As moisture
and acids collect in the engine,they contribute to the formation of rust, on the cylinder
walls, camshafts and tappets. So,because moisture and acids, they are collected in the engine,
they will contribute to rust, in on the cylinder walls, camshafts and tappets.
Refer Slide Time 🙁 51: 11) Now, when the engines are run, after rust
has formed, the rust becomes a very fine abrasive, causing internal engine where, particularly
to the crank, camshafts and tappets. Now, because of this rust, it becomes a very fine
abrasive and it will cause internal engine wear, especially to the camshafts and tappets,
as these components where they make more metal, which attacks, the softer metals in the engines.
Now, as these components will wear, they will make more metal and will attack the softer
metals in the engine. Piston plugs,are examples of parts: that may be rapidly, when rust becomes
an abrasive, inside the engine.So, these piston plugs, they are made of soft materials, they
are rapidly, when rust becomes an abrasive inside the engine,this wear, could eventually,
lead to failure. So very important point, in the case, of a low time engine, with a
history of infrequent flight borescope examination, of the cylinders and aninspection of cam and
tempered surfaces shall be required. So, in cases where, the engine has not been operated
frequently, where it has been left idle, for long periods, in that case, the borescope
examination of the cylinders, the inspection of cam and tempered surfaces is very essential.
The slow numbers and the hours of operation records, do not guarantee, reaching TBO,with
many long hours of trouble-free operation. So now, we have seen that, in case, you find
an engine with less number of hours: that will not give you a guarantee: that your engine,will
give you trouble-free hours.So, there are certain rig inspections to be carried out,
in case, if your engine has not been flown, continuously and in case, if the engine is
supposed, to stay out of service for more than 30 days, it needs to be preserved.
Refer Slide Time 🙁 53: 05) Now, some more important basic points, to
be kept in mind for engine maintenance, some very, basic points, we have read them earlier
also, this is just to brush it, oil filters, clean engine oil is essential to long engine
life, we have just now seen yes, how clean engine oil is very essential, under normal
operating conditions the oil should be replaced every 50 hours of operation, or for calendar
months, whichever is earlier.This I had mentioned earlier also, the frequency of oil replacement,
it is very important that the filter element be cut,open in order to examine, the material
trapped, in the filter for evidence, of internal engine condition, however,operation in dusty,
areas or cold climates, may require more frequent oil change, despite the use of an oil filter.So,
in normal course of operation, the oil replacement is to be carried out at every 50 hours of
operation or for calendar months, whichever is earlier, in case our operation is in dusty
or sandy conditions, in that case, more frequent, replacement of engine oil and oil filter will
be required, as mentioned by the manufacturer. And engine which sits for long, periods between
flights, should have an oil change, at four-month interval,regardless of the limited flight
time accumulated, the filter cannot filter water and assets, which may accumulate, in
oil. So in case, if your engine is not operating very frequently, in that case also, the oil
should be replaced, after four calendar months, it is very important, to replace it after
four calendar months, because the filter will not be able, to filter out, water and assets,
which accumulate, inside the engine in oil. We have seen, in a previous slide, how acids
and water have accumulated, they get accumulated when your engine is not frequently used, in
that case, your oil should be replaced every four months, very important.
Refer Slide Time 🙁 55: 07) Next important thing is oil consumption, it
is a very important trend to monitor in an engine,we should closely monitor the general
history of oil consumption during the life of the engine, it is typical of an engine,
during seating of, new piston rings: that oil consumption may be erratic or high. So
in case, of a new engine you will experience high oil consumption, but, after the rings
are seated, generally within the first 25 to 50 hours,oil consumption should level off
below the maximum limits, established by the manufacturer. So, during the initial hours,
during say first 25 hours or 50 hours,when your piston rings have not seated,you will
experience more oil consumption and gradually, it will reduce, later during the life of the
engine, if there is a noticeable,increase of oil consumption, within a 25 hour period,
this could be a dangerous signal and calls for an,’Investigation’.So, once the oil consumption
level has settled and during the course of operation if you observe, drastic,increase
in oil consumption, then that is a cause of investigation and we need to investigate it
properly. The oil filters,should be carefully observed for signs of metal, compression check
of the cylinders, should be carried out and also,look inside the cylinders with a borescope,to
detect any unusual condition. So, through your filter element,should be inspected, you
should observe the compression, check of the cylinders and incase, if it is required then
borescope, inspection should also, be carried out, to look inside the cylinders.
Refer Slide Time 🙁 56: 43) Air filter very important thing, we have read,
about it earlier also, just to revise it, the induction air filter is a very important
element, in the life of an aircraft engine, with the modern high-performance power plant,
we must keep dirt and abrasives, out ofthe engine, if it is to attain theexpected life
and trouble-free hours. So,we have seen in a previous slide, a clean air is very much,
required for trouble-free life of the engine. We should be aware that excessive wear and
early, failures of reciprocating engine parts, is due in many instances to contaminates,
introduced through or around the air filter. So in case, if you are using a faulty, air
filter our damaged air filter or a clogged air filter,then you will be ingesting dirt,inside
and it will lead to, lot of fear and ultimate failure of the engine. The aircraft manufacturer’s
instructions for maintenance of the air filter must be closely followed, when operating in
very dusty or sandy conditions, it may be necessary, to service the filters frequently,
in accordance with the manufacturer’s recommendations. So, the replacement frequency of the air filter,is
mentioned by the manufacturers, in general, it is one year, every year you have to, replace
the filter element, air filter element and at regular intervals, during the inspections,
you need to clean them and in case, if you are operating in dusty or sandy conditions,
in that case,we may be required to replace the filters, very frequently, in accordance
with the manufacturer’s recommendations. Refer Slide Time 🙁 58: 22)
Next is the use of incorrect fuel. Now,fuel we have read, in our fuel system, chapter
the types of fuel and it is very important, to use the right type of fuel,for the engine,
there have been instances of the accidental use of the wrong fuel, particularly turbine
fuel. Turbine fuel or a mixture of turbine fuel and aviation gasoline, has proven to
be a particularly, ruinous fuel for piston engines. Now, in case, if you use a fuel other
than that is recommended, by the manufacturer, say turbine fuel or a mixture of turbine and
gasoline, then that, can doing your engine. As a result if the engine has been operated
with this unspecified fuel, qualified, maintenance personnel, must take, must make a detailed,inspection
of the engine, with particular attention to the combustion chambers.So in case, if the
fuel has been, used with and with the fuel, other than that specified by the manufacturer
in that case, the maintenance personnel are required, to inspect the engines thoroughly,
with a particular attention to the combustion chambers. If detonation has been severe enough,
further damage will occur, to crankpins and main bearings, counter weights and valve train
components. In view of possible damage,this assembly and inspection of the engine parts,
is the only safe recommendation that can be made, after the engine has been operated with
improper fuels. So in case, if the engine is used with improper fuel, then it is better
to dismantle the engine and inspect the engine parts, if it has been determined that the
engine has been run on unspecified fuel, do not continue to operate,it unless, it has
been inspected and certified, to be air worthy, by competent maintenance personal.So, in that
case, you have to get it inspected, get it dismantled, inspected and certified by qualified
people and then only the engine will be air worthy,for flights. So, these were some of
the basic points, what we had to see? During maintenance of engines, so that, we can have,
trouble-free life of the engine. Now,apart from these basic points, there are few more
points which we need to follow, whatever, publications, are available, whatever publications
are provided by the manufacturer, we should have, all the publications with us, we should
have, all the latest publications with us and we should, maintain the engines according
to the recommendations, by the manufacturers,because freak, there are frequent revisions in these
publications and we should keep our self-updated, about the latest developments and about the
latest recommendations by the manufacturers. During the course of maintenance, in case,if
we face any problem, if we encounter any snag or anything special or unusual,then that feedback
should always be given to the manufacturer and we should take, the manufacturers advice
also. This helps us also, while maintaining, our machine,at the same time, our experience,will
also help other operators, because these,unusual things, this is recorded with the manufacturer
and manufacturer can come up, with some solutions, so that, the others, will not face this kind
of problems. So, very important thing, to keepthe manufacturer always, informed andalways
we should consult, the manufacturers, we should follow, the latest publications, we should
always follow the approved procedures and approve materials, while we maintain the engines
or our aircrafts. So, this was all about the engine part and we have completed all the
systems and the different procedures, different maintenance schedules and what are the and
the basic points, to be considered while, maintaining the machine and an engine. Thank

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