The airplane engine and propeller, often referred to as the aircraft
powerplant, work in combination to produce thrust. The powerplant
propels the airplane and drives the various systems that support the
operation of an airplane.
A Mercedes E200 configuration 271EVO
engine and 722.9 transmission, mileage of 131670km. The car to replace
the oil filter base, 4 days after the engine fault light, and idle
engine jitter, the vehicle speed slow. xtool x100
- B – C – D – E – F – G – H – I – J – K – L – M – N – O – P – Q – R – S
- T – U – V – W Mmachine – машина, станок, обрабатывать
резаниемmachinery – машины, техника, механизмыmagnet – магнитmagnetic –
магнитный, магнито-magnetic field – магнитное полеmagnetic flux –
магнитный потокmagnetic switch – электромагнитный выключатель,
соленоидmagneto – магнетоmain – главный, коренной, основнойmain air
bleed – главки воздушный каналmain beam – дальний светmain bearing –
коренной подшипник, подшипник коленчатого валаmain bearing journal –
шейка коренного подшипника коленчатого валаmain jet – главный жиклёрmain
journal – шейка коренного подшипника коленчатого валаmain leaf –
коренной лист рессорыmainshaft – вторичный / ведомый валmainshaft spigot
- гнездо в торце ведущего вала для игольчатого п ведомого валаmaintain –
содержать в порядке, сохранятьmaintenance – техобслуживание,
уходmaintenance-free – не требующий обслуживанияmajor – больший,
основнойmajor accident – крупная авария, большое столкновениеmalady –
неисправностьmale – входящий в другую деталь, охватываемый, “папа”male
connector – штыревая часть соединителя, вилка, “папа”malfunction –
помеха, неисправная работа, работа с перебоямиmallet – киянка,
деревянный молотокmanagement – руководство, управлениеmandrel – оправка,
бородок, пробойникmanifold – трубопровод, патрубокmanifold ablolute
pressure (MAP) – давление во впускном коллектореmanifold gasket –
уплотнительная прокладка коллектораmanometer – манометрmanual –
руководство, ручной, вручнуюmanual gearbox – коробка передач с ручным
переключениемmanual transaxle, -transmission – коробка передач с ручным
переключениемmanufacturer – изготовитель, производительmap – картаMAP
(manifold ablolute pressure) – давление во впускном коллектореmap lamp,
-light – лампа для освещения картыmargin – край, обочина, дистанция
между автомобилямиmark – метка, знак, отмечать, следmarker lamp, -light
- габаритная лампаmarking – отмечать, маркироватьmask – шаблон,
накладка, трафаретmasking tape – клейкая лента для закрытия не
окрашиваемых частей кузоваmass – массаmass air flow sensor – измеритель
количества воздухаmaster – главный, основнойmaster cylinder – главный
цилиндрmastic – мастика, замазкаmat – мат, коврикmatch – подбирать
подходящее / пару, сочетатьmatchmark – установочная меткаmate – парная /
сопряжённая деталь, сопрягатьmaterial – материалmating serrations –
сопряжённые зубцыmating Surface – сопряжённые / соприкасающиеся
поверхностиmatrix – матрица, секция, элементmatting – подстилка,
коврикmauve – розовато-лиловыйmaximum – максимальный, предельныйmean –
середина, средний, средняя величинаmean pressure – среднее
давлениеmeasure – мера, размер, измерятьmeasurement – измерениеmeasuring
point – точка для измеренияmechanical – механическийmechanic(ian) –
механик, слесарьmechanism – механизмmedium – среда, средне-medium size –
средний размерmelt – плавка, расплавлятьmember – часть, опора,
балкаmembrane – мембрана, диафрагмаmemory – память, запоминающее
устройствоmercury – ртутьmerge – заглубить, заподлицо, впотайmesh –
зацепление, находиться в зацепленииmesh load – сила сцепленияmessage –
сообщение, информацияmetal – металлmeter – метр, измерительный прибор,
измерятьmetering chamber – измерительная / дозирующая камераmetering
head – измерительная головкаmetering rod – измерительная штанга,
регулирующая / регулируемая тягаmetering valve – дозирующий /
регулирующий клапан, игольчатый клапанmethod – метод, способ,
порядокmethylated spirit – денатурат, этиловый спиртmica insulator –
слюдяной изоляторmicrocomputer – микрокомпьютер, бортовой
компьютерmicrofiche – микрофишаmicrometer – микрометрmicroprocessor –
микропроцессорmicroswitch – микровыключательmid – средне-, полу-,
нейтральныйmid engine – двигатель центрального расположенияmid-range –
средняя зона, средний режимmile – миля (1609 м)mileage – пробег
автомобиля в миляхmiles per hour (mph) – миль в часmineral oil –
минеральное маслоminimum – минимум, наименьшийmirror – зеркалоmirror
defogger – обогреватель зеркалаmisalignment – несоосность,
непараллельность, отклонение от осиmisfire – прерывание,
перебойmisfiring – пропуск / перебой зажиганияmist – туман, мглаmix –
смесь, мешать, перемешиватьmixing valve – смесительный клапанmixture –
смесьmixture (adjustment) screw – регулировочный винт качества
смесиmixture (control) screw – регулировочный винт качества смесиmixture
ratio – состав смесиmobile phone – мобильный / радио телефонmode –
действие, режим работыmodel – модель, образецmodel year – период выпуска
модели автомобиляmodification – изменение, модификацияmodified –
модифицированmodify – изменять, преобразовывать, превращатьmodulator –
модулятор, преобразовательmodule – модуль, блок управленияmoist –
влажный, сыройmoistener – увлажнительmoisture – влажностьmold – форма,
отливать в формуmolecule – молекулаmolybdenum – молибден, Моmoment –
моментmomentary – мгновенный, кратковременныйMON – Motor Octane Number –
октановое число по моторному методуmonitor – монитор, проверочное
устройство, проверкаmono – цельный, одиночныйmonocoque – бескаркасный
несущий корпус, монококmonolithic – единый, монолитныйmonth –
месяцmoonroof – люк в крышеmotion – движение, перемещение, ходmotor –
электромотор, мотор, двигательmotorway – магистраль, автострадаmould –
литейная форма, лекало, шаблонmoulding – молдинг, декоративная
накладкаmount – монтировать, устанавливать, крепление, опораmounting –
монтаж, установка, сборкаmounting bracket – установочный / опорный
кронштейнmouth – вход, горловина, отверстиеmovable – движущийся,
подвижныйmove – двигать, смещать, передвигатьmovement – движение,
передвижение, ходmoving coil – перемещающаяся / вращающаяся катушкаMP –
multi-purpose grease – универсальная консистентная смазкаmph (miles per
hour) – миль в часMPI – multi-point injection – впрыск топлива во
впускной трактMT – manual transaxle, -transmission – коробка передач с
ручным переключениемmud flap – грязеотражатель, фартук крыла,
брызговикmudguard – крылоmuffler – глушительmulti – многоmulti-element
pump – многоплунжерный насос высокого давленияmulti-function switch –
многофункциональный переключательmulti-grade oil – универсальное /
всесезонное маслоmulti-hole injector – бесштифтовая форсункаmulti-hole
nozzle – бесштифтовая форсункаmulti-leaf spring – многолистовая
рессораmulti-meter – тестер, авометрmultiple – многократный, сложный,
составнойmultiplication – ускоренная передача, умножениеmultiplier –
множитель, коэффициентmulti-plug – многополюсная вилка, многоштырьковый
разъёмmulti-point (fuel) injection – MPI – впрыск топлива во впускной
трактmulti-port (fuel) injection – впрыск топлива во впускной
трактmulti-purpose grease – MP – универсальная консистентная
смазкаmulti-spherical – многосферическийmulti-valve –
многоклапанныйmushroom (type) tappet – грибовидный толкатель клапана
Reciprocating engines底特律活塞（Detroit Pistons）斯特林发动机
Most small airplanes are designed with reciprocating engines. The name
is derived from the back-and-forth, or reciprocating, movement of the
pistons. It is this motion that produces the mechanical energy needed to
accomplish work. Two common means of classifying reciprocating engines
Troubleshooting and troubleshooting
- by cylinder arrangement with respect to the crankshaft—radial,
in-line, v-type or opposed, or
- by the method of cooling—liquid or air-cooled.
The car replaced the oil filter base,
disassembled the intake manifold, according to the initial phenomenon of
the fault to determine the following reasons: the intake system in a
vacuum tube leak or not installed in place; intake manifold leak ;
Throttle does not match well, or is not installed in place; ignition
oil supply problem.
Radial engines were widely used during World War II, and many are still
in service today. With these engines, a row or rows of cylinders are
arranged in a circular pattern around the crankcase. The main advantage
of a radial engine is the favorable power-to-weight ratio.
Because the car did not change the
maintenance of the spark plug, VVDI MB
Tooland the last into the store to check the
spark plug attached to a lot of coke, and the phenomenon of burning the
electrode, first with a new spark plug installed, the car after the
engine or jitter. There is no problem with the spark plug connected to
the diagnosis of the spark plug. Read the fault code: P0172 mixture
(cylinder column 1) is too thick, the signal amplitude is greater than
the maximum amplitude. The meaning of the fault code is the mixture is
too thick, resulting in mixed gas is too thick because the main reason
is too much fuel injection, too little intake or burning is not good.
Follow the fault code to guide the actual value of the engine under
idling conditions. VVDI Key
In-line engines have a comparatively small frontal area, but their
power-to-weight ratios are relatively low. In addition, the rearmost
cylinders of an air-cooled, in-line engine receive very little cooling
air, so these engines are normally limited to four or six cylinders.
The actual value of the rail pressure
is 5440kPa (marked value is 4540 ~ 6540kPa), which will remove the
problem of high pressure pump. Throttle downstream pressure sensor
pressure value of 48.266kPa (standard value of 20 ~ 40kPa), the signal
voltage is 1.0V (standard value is 0.5 ~ 0.7V). There are two reasons
for its actual value: the sensor and its line problems; air intake
system in a part of the leak. According to the circuit diagram to
measure the sensor supply voltage of 5V, ground and signal lines are
normal. Throttle upstream pressure sensor and the downstream pressure
sensor, the two sensors are interchangeable, the actual value of the
sensor is still incorrect, indicating that the sensor and its line is no
problem. Next check the air intake system where there is no leakage,
V-type engines provide more horsepower than in-line engines and still
retain a small frontal area. Further improvements in engine design led
to the development of the horizontally-opposed engine.
In the first easy after the difficult
principle, first check the intake system of each vacuum tube with or
without leakage of the place, and then check the throttle, remove the
throttle to see the seal is not damaged and crushed place, flap is not
issued card , To save the throttle again after the replacement, with a
diagnostic instrument to re-learn, taking into account the E-class 212
models in the diagnostic test when the voltage requirements are more
stringent, when the battery voltage is lower than 11.6V when some of the
elements of learning And the match may not succeed. Connected to the
battery charger on the throttle to relearn, start the vehicle, the fault
remains the same, remove the throttle problem, VVDI MB
Then focus on checking the intake manifold, remove the intake manifold
to see its seal is intact, no abnormalities, but also in the seal on the
sealant, and then installed in accordance with the standard torque
intake manifold. Start the car, the engine or jitter, throttle
downstream pressure sensor actual value is not normal. Re-order ideas,
starting from the air intake step by step careful investigation, see
whether the missing part. When the rear of the air filter to check the
intake pipe, found that as long as the pull out of the intake pipe
connected to the secondary air jet pump hose (below),
C4the engine does not shake, and the
actual value of the throttle downstream pressure sensor Also fell to the
normal range. Put the handle near the hose, can obviously feel the warm
air blowing, smell like the exhaust gas from the
Opposed-type engines are the most popular reciprocating engines used on
small airplanes. These engines always have an even number of cylinders,
since a cylinder on one side of the crankcase “opposes” a cylinder on
the other side. The majority of these engines are air cooled and usually
are mounted in a horizontal position when installed on fixed-wing
airplanes. Opposed-type engines have high power-to-weight ratios because
they have a comparatively small, lightweight crankcase. In addition, the
compact cylinder arrangement reduces the engine´s frontal area and
allows a streamlined installation that minimizes aerodynamic drag.
This tube is the secondary air jet pump
inlet pipe, the secondary air jet pump is usually only in the coolant
temperature between 10 ~ 60 ℃, the engine speed is less than 3000r /
min, the engine is idle or part of the load. The secondary air jet pump
draws fresh air from here and then switches the vacuum control secondary
air injection valve from the intake manifold by the air pump changeover
valve (Y32). The fresh air enters the row of the cylinder head with the
secondary air injection valve Gas and exhaust gas to react, so that the
three-way catalytic converter as soon as possible to achieve the working
temperature, thus improving the warm-up process of emission performance.
According to the working principle of the secondary air injection
system, this tube should not be blown out of the air. There are two
reasons for this phenomenon:the air pump switching valve (Y32) is always
in the normally open state, the air pump switching valve (Y32) has been
through the vacuum to open the secondary air injection valve; secondary
air injection valve stuck, Open the state. Through the diagnostic device
to observe the actual value of the air pump switch valve, has been in a
closed state, and then through the diagnostic instrument to activate the
open, close are normal, the exclusion is the air pump switch valve (Y32)
problem. The following left the second air injection valve, and remove
the secondary air injection valve and open and found the diaphragm was
coke locked, can not be closed.Open the state. Through the diagnostic
device to observe the actual value of the air pump switch valve, has
been in a closed state, and then through the diagnostic instrument to
activate the open, close are normal, the exclusion is the air pump
switch valve (Y32) problem. The following left the second air injection
valve, and remove the secondary air injection valve and open and found
the diaphragm was coke locked, can not be closed.Open the state. Through
the diagnostic device to observe the actual value of the air pump switch
valve, has been in a closed state, and then through the diagnostic
instrument to activate the open, close are normal, the exclusion is the
air pump switch valve (Y32) problem. The following left the second air
injection valve, and remove the secondary air injection valve and open
and found the diaphragm was coke locked, can not be closed.can not be
closed.can not be closed.
The main parts of a reciprocating engine include the cylinders,
crankcase, and accessory housing. The intake/exhaust valves, spark
plugs, and pistons are located in the cylinders. The crankshaft and
connecting rods are located in the crankcase. The magnetos are normally
located on the engine accessory housing.
Since the secondary air injection valve
can not be completely closed, the exhaust gas is returned to the intake
pipe through the piping of the secondary air injection system so that
the pressure of the intake manifold is increased and the exhaust gas is
then introduced into the cylinder .
Because the entry of the exhaust gas,
relatively fresh air will be reduced, so that fuel can not be fully
burned, air-fuel ratio is not right, the engine jitter and reported
mixed gas too thick fault. The secondary air injection valve carbon
deposition clean, re-installed back, the engine running smoothly, the
Figure 1: Main components of a reciprocating engine.
The next morning to wash the car ready
to pick up the goods, start the vehicle and found the vehicle just off
the car immediately, and then start the second time, start time is too
long, but after the start of the engine running very smoothly . Then
start a few times, everything is normal. Stopped a dozen minutes to
start again, the failure appeared. And then use a multimeter to measure
the starting voltage of 10V, normal. The low pressure of the fuel system
is measured at about 500 kPa (standard value 400 to 670 kPa). Connect
the diagnostic device, analyze the actual value of the engine at
startup, found that the actual value of the downstream pressure sensor
is not normal, its value is 38.6kPa
(Standard value is 20 ~ 40kPa), close
to the critical value. Will be the second air pump inlet hose unplugged
and found a blown air, turn off after ten minutes and then start the
vehicle again, everything is normal. Again remove the secondary air
injection valve and find that the diaphragm is jammed again. Remove the
coke after careful observation, the diaphragm has been deformed, off
lax, it is easy to be coke locked.
The basic principle for reciprocating engines involves the conversion of
chemical energy, in the form of fuel, into mechanical energy. This
occurs within the cylinders of the engine through a process known as the
four-stroke operating cycle. These strokes are called intake,
compression, power, and exhaust.
Replace the new secondary air injection
valve after troubleshooting.
In the troubleshooting, we must
comprehensively, CGDI MB
comprehensively and systematically consider, master the working
principle of the engine system, according to the working principle of
the possible parts of the failure to exclude one by one, careful
analysis of the various failures and the actual value is very important
Can help us find ideas and found that difficult to find the point of
Figure 2: The arrows in this illustration indicate the direction of
motion of the crankshaft and piston during the four-stroke cycle.
The intake stroke begins as the piston starts its downward travel. When
this happens, the intake valve opens and the fuel/air mixture is drawn
into the cylinder.
The compression stroke begins when the intake valve closes and the
piston starts moving back to the top of the cylinder. This phase of the
cycle is used to obtain a much greater power output from the fuel/air
mixture once it is ignited.
The power stroke begins when the fuel/air mixture is ignited. This
causes a tremendous pressure increase in the cylinder, and forces the
piston downward away from the cylinder head, creating the power that
turns the crankshaft.
The exhaust stroke is used to purge the cylinder of burned gases. It
begins when the exhaust valve opens and the piston starts to move toward
the cylinder head once again.
Even when the engine is operated at a fairly low speed, the four-stroke
cycle takes place several hundred times each minute. In a four-cylinder
engine, each cylinder operates on a different stroke. Continuous
rotation of a crankshaft is maintained by the precise timing of the
power strokes in each cylinder. Continuous operation of the engine
depends on the simultaneous function of auxiliary systems, including the
induction, ignition, fuel, oil, cooling, and exhaust systems.
The propeller is a rotating airfoil, subject to induced drag, stalls,
and other aerodynamic principles that apply to any airfoil. It provides
the necessary thrust to pull, or in some cases push, the airplane
through the air.
The engine power is used to rotate the propeller, which in turn
generates thrust very similar to the manner in which a wing produces
lift. The amount of thrust produced depends on the shape of the airfoil,
the angle of attack of the propeller blade, and the r.p.m. of the
engine. The propeller itself is twisted so the blade angle changes from
hub to tip. The greatest angle of incidence, or the highest pitch, is at
the hub while the smallest pitch is at the tip.
Figure 3: Changes in propeller blade angle from hub to tip.
The reason for the twist is to produce uniform lift from the hub to the
tip. As the blade rotates, there is a difference in the actual speed of
the various portions of the blade. The tip of the blade travels faster
than that part near the hub, because the tip travels a greater distance
than the hub in the same length of time.
Changing the angle of incidence (pitch) from the hub to the tip to
correspond with the speed produces uniform lift throughout the length of
the blade. If the propeller blade was designed with the same angle of
incidence throughout its entire length, it would be inefficient, because
as airspeed increases in flight, the portion near the hub would have a
negative angle of attack while the blade tip would be stalled.
Figure 4: Relationship of travel distance and speed of various portions
of propeller blade.
Small airplanes are equipped with either one of two types of propellers.
One is the fixed-pitch, and the other is the controllable-pitch.
The pitch of this propeller is set by the manufacturer, and cannot be
changed. With this type of propeller, the best efficiency is achieved
only at a given combination of airspeed and r.p.m. There are two types
of fixed-pitch propellers—the climb propeller and the cruise propeller.
Whether the airplane has a climb or cruise propeller installed depends
upon its intended use:
The climb propeller has a lower pitch, therefore less drag. Less drag
results in higher r.p.m. and more horsepower capability, which increases
performance during takeoffs and climbs, but decreases performance during
The cruise propeller has a higher pitch, therefore more drag. More drag
results in lower r.p.m. and less horsepower capability, which decreases
performance during takeoffs and climbs, but increases efficiency during
The propeller is usually mounted on a shaft, which may be an extension
of the engine crankshaft. In this case, the r.p.m. of the propeller
would be the same as the crankshaft r.p.m. On some engines, the
propeller is mounted on a shaft geared to the engine crankshaft. In this
type, the r.p.m. of the propeller is different than that of the engine.
In a fixed-pitch propeller, the tachometer is the indicator of engine
Figure 5: Engine r.p.m. is indicated on the tachometer.
A tachometer is calibrated in hundreds of r.p.m., and gives a direct
indication of the engine and propeller r.p.m. The instrument is
color-coded, with a green arc denoting the maximum continuous operating
Some tachometers have additional markings to reflect engine and/or
propeller limitations. Therefore, the manufacturer´s recommendations
should be used as a reference to clarify any misunderstanding of
The revolutions per minute are regulated by the throttle, which controls
the fuel/air flow to the engine.
At a given altitude, the higher the tachometer reading, the higher the
power output of the engine.
When operating altitude increases, the tachometer may not show correct
power output of the engine. For example, 2,300 r.p.m. at 5,000 feet
produce less horsepower than 2,300 r.p.m. at sea level. The reason for
this is that power output depends on air density. Air density decreases
as altitude increases. Therefore, a decrease in air density (higher
density altitude) decreases the power output of the engine. As altitude
changes, the position of the throttle must be changed to maintain the
same r.p.m. As altitude is increased, the throttle must be opened
further to indicate the same r.p.m. as at a lower altitude.
Although some older adjustable-pitch propellers could only be adjusted
on the ground, most modern adjustable-pitch propellers are designed so
that you can change the propeller pitch in flight. The first
adjustable-pitch propeller systems provided only two pitch settings – a
low-pitch setting and a high-pitch setting. Today, however, nearly all
adjustable-pitch propeller systems are capable of a range of pitch
A constant-speed propeller is the most common type of adjustable-pitch
propeller. The main advantage of a constant-speed propeller is that it
converts a high percentage of brake horsepower (BHP) into thrust
horsepower (THP) over a wide range of r.p.m. and airspeed combinations.
A constant-speed propeller is more efficient than other propellers
because it allows selection of the most efficient engine r.p.m. for the
An airplane with a constant-speed propeller has two controls—the
throttle and the propeller control. The throttle controls power output,
and the propeller control regulates engine r.p.m. and, in turn,
propeller r.p.m., which is registered on the tachometer.
Once a specific r.p.m. is selected, a governor automatically adjusts the
propeller blade angle as necessary to maintain the selected r.p.m. For
example, after setting the desired r.p.m. during cruising flight, an
increase in airspeed or decrease in propeller load will cause the
propeller blade angle to increase as necessary to maintain the selected
r.p.m. A reduction in airspeed or increase in propeller load will cause
the propeller blade angle to decrease.
The range of possible blade angles for a constant-speed propeller is the
propeller´s constant-speed range and is defined by the high and low
pitch stops. As long as the propeller blade angle is within the
constant-speed range and not against either pitch stop, a constant
engine r.p.m. will be maintained. However, once the propeller blades
contact a pitch stop, the engine r.p.m. will increase or decrease as
appropriate, with changes in airspeed and propeller load. For example,
once a specific r.p.m. has been selected, if aircraft speed decreases
enough to rotate the propeller blades until they contact the low pitch
stop, any further decrease in airspeed will cause engine r.p.m. to
decrease the same way as if a fixed-pitch propeller were installed. The
same holds true when an airplane equipped with a constant-speed
propeller accelerates to a faster airspeed. As the aircraft accelerates,
the propeller blade angle increases to maintain the selected r.p.m.
until the high pitch stop is reached. Once this occurs, the blade angle
cannot increase any further and engine r.p.m. increases.
On airplanes that are equipped with a constant-speed propeller, power
output is controlled by the throttle and indicated by a manifold
pressure gauge. The gauge measures the absolute pressure of the fuel/air
mixture inside the intake manifold and is more correctly a measure of
manifold absolute pressure (MAP). At a constant r.p.m. and altitude, the
amount of power produced is directly related to the fuel/air flow being
delivered to the combustion chamber. As you increase the throttle
setting, more fuel and air is flowing to the engine; therefore, MAP
increases. When the engine is not running, the manifold pressure gauge
indicates ambient air pressure (i.e., 29.92 in. Hg). When the engine is
started, the manifold pressure indication will decrease to a value less
than ambient pressure (i.e., idle at 12 in. Hg). Correspondingly, engine
failure or power loss is indicated on the manifold gauge as an increase
in manifold pressure to a value corresponding to the ambient air
pressure at the altitude where the failure occurred.
Figure 6: Engine power output is indicated on the manifold pressure
The manifold pressure gauge is color-coded to indicate the engine´s
operating range. The face of the manifold pressure gauge contains a
green arc to show the normal operating range, and a red radial line to
indicate the upper limit of manifold pressure.
For any given r.p.m., there is a manifold pressure that should not be
exceeded. If manifold pressure is excessive for a given r.p.m., the
pressure within the cylinders could be exceeded, thus placing undue
stress on the cylinders. If repeated too frequently, this stress could
weaken the cylinder components, and eventually cause engine failure.
You can avoid conditions that could overstress the cylinders by being
constantly aware of the r.p.m., especially when increasing the manifold
Conform to the manufacturer´s recommendations for power settings of a
particular engine so as to maintain the proper relationship between
manifold pressure and r.p.m.
When both manifold pressure and r.p.m. need to be changed, avoid engine
overstress by making power adjustments in the proper order:
When power settings are being decreased, reduce manifold pressure before
reducing r.p.m. If r.p.m. is reduced before manifold pressure, manifold
pressure will automatically increase and possibly exceed the
When power settings are being increased, reverse the order—increase
r.p.m. first, then manifold pressure.
To prevent damage to radial engines, operating time at maximum r.p.m.
and manifold pressure must be held to a minimum, and operation at
maximum r.p.m. and low manifold pressure must be avoided.
Under normal operating conditions, the most severe wear, fatigue, and
damage to high performance reciprocating engines occurs at high r.p.m.
and low manifold pressure.
Excursion: Aerodynamics of the propeller
The induction system brings in air from the outside, mixes it with fuel,
and delivers the fuel/air mixture to the cylinder where combustion
occurs. Outside air enters the induction system through an intake port
on the front of the engine cowling. This port normally contains an air
filter that inhibits the entry of dust and other foreign objects. Since
the filter may occasionally become clogged, an alternate source of air
must be available. Usually, the alternate air comes from inside the
engine cowling, where it bypasses a clogged air filter. Some alternate
air sources function automatically, while others operate manually.
Two types of induction systems are commonly used in small airplane
the carburetor system, which mixes the fuel and air in the carburetor
before this mixture enters the intake manifold, and
the fuel injection system, which mixes the fuel and air just before
entry into each cylinder.
Carburetors are classified as either float-type or pressure-type.
Pressure carburetors are usually not found on small airplanes. The basic
difference between a pressure carburetor and a float-type is the
pressure carburetor delivers fuel under pressure by a fuel pump.
In the operation of the float-type carburetor system, the outside air
first flows through an air filter, usually located at an air intake in
the front part of the engine cowling. This filtered air flows into the
carburetor and through a venturi, a narrow throat in the carburetor.
When the air flows through the venturi, a low-pressure area is created,
which forces the fuel to flow through a main fuel jet located at the
throat. The fuel then flows into the airstream, where it is mixed with
the flowing air.
Figure 7: Float-type carburetor.
The fuel/air mixture is then drawn through the intake manifold and into
the combustion chambers, where it is ignited. The “float-type
carburetor” acquires its name from a float, which rests on fuel within
the float chamber. A needle attached to the float opens and closes an
opening at the bottom of the carburetor bowl.
This meters the correct amount of fuel into the carburetor, depending
upon the position of the float, which is controlled by the level of fuel
in the float chamber. When the level of the fuel forces the float to
rise, the needle valve closes the fuel opening and shuts off the fuel
flow to the carburetor. The needle valve opens again when the engine
requires additional fuel.
The flow of the fuel/air mixture to the combustion chambers is regulated
by the throttle valve, which is controlled by the throttle in the
Carburetors are normally calibrated at sea-level pressure, where the
correct fuel-to-air mixture ratio is established with the mixture
control set in the FULL RICH position. However, as altitude increases,
the density of air entering the carburetor decreases, while the density
of the fuel remains the same. This creates a progressively richer
mixture, which can result in engine roughness and an appreciable loss of
power. The roughness normally is due to spark plug fouling from
excessive carbon buildup on the plugs. Carbon buildup occurs because the
excessively rich mixture lowers the temperature inside the cylinder,
inhibiting complete combustion of the fuel. This condition may occur
during the pretakeoff runup at high-elevation airports and during climbs
or cruise flight at high altitudes. To maintain the correct fuel/air
mixture, you must lean the mixture using the mixture control. Leaning
the mixture decreases fuel flow, which compensates for the decreased air
density at high altitude.
During a descent from high altitude, the opposite is true. The mixture
must be enriched, or it may become too lean. An overly lean mixture
causes detonation, which may result in rough engine operation,
overheating, and a loss of power. The best way to maintain the proper
mixture is to monitor the engine temperature and enrichen the mixture as
Proper mixture control and better fuel economy for fuel-injected engines
can be achieved by use of an exhaust gas temperature gauge. Since the
process of adjusting the mixture can vary from one airplane to another,
it is important to refer to the Airplane Flight Manual (AFM) or the
Pilot´s Operating Handbook (POH) to determine the specific procedures
for a given airplane.
One disadvantage of the float-type carburetor is its icing tendency.
Carburetor ice occurs due to the effect of fuel vaporization and the
decrease in air pressure in the venturi, which causes a sharp
temperature drop in the carburetor. If water vapor in the air condenses
when the carburetor temperature is at or below freezing, ice may form on
internal surfaces of the carburetor, including the throttle valve.
Figure 8: The formation of carburetor ice may reduce or block fuel/air
flow to the engine.
The reduced air pressure, as well as the vaporization of fuel,
contributes to the temperature decrease in the carburetor. Ice generally
forms in the vicinity of the throttle valve and in the venturi throat.
This restricts the flow of the fuel/air mixture and reduces power. If
enough ice builds up, the engine may cease to operate.
Carburetor ice is most likely to occur when temperatures are below 70°F
(21°C) and the relative humidity is above 80 percent. However, due to
the sudden cooling that takes place in the carburetor, icing can occur
even with temperatures as high as 100°F (38°C) and humidity as low as 50
percent. This temperature drop can be as much as 60 to 70°F.
Therefore, at an outside air temperature of 100°F, a temperature drop of
70°F results in an air temperature in the carburetor of 30°F.
Figure 9: Although carburetor ice is most likely to form when the
temperature and humidity are in ranges indicated by this chart,
carburetor ice is possible under conditions not depicted.
The first indication of carburetor icing in an airplane with a
fixed-pitch propeller is a decrease in engine r.p.m., which may be
followed by engine roughness. In an airplane with a constant-speed
propeller, carburetor icing usually is indicated by a decrease in
manifold pressure, but no reduction in r.p.m. Propeller pitch is
automatically adjusted to compensate for loss of power. Thus, a constant
r.p.m. is maintained. Although carburetor ice can occur during any phase
of flight, it is particularly dangerous when using reduced power during
a descent. Under certain conditions, carburetor ice could build
unnoticed until you try to add power. To combat the effects of
carburetor ice, engines with float-type carburetors employ a carburetor
Carburetor heat is an anti-icing system that preheats the air before it
reaches the carburetor. Carburetor heat is intended to keep the fuel/air
mixture above the freezing temperature to prevent the formation of
carburetor ice. Carburetor heat can be used to melt ice that has already
formed in the carburetor provided that the accumulation is not too
great. The emphasis, however, is on using carburetor heat as a
The carburetor heat should be checked during the engine runup. When
using carburetor heat, follow the manufacturer´s recommendations.
When conditions are conducive to carburetor icing during flight,
periodic checks should be made to detect its presence. If detected, full
carburetor heat should be applied immediately, and it should be left in
the ON position until you are certain that all the ice has been removed.
If ice is present, applying partial heat or leaving heat on for an
insufficient time might aggravate the situation. In extreme cases of
carburetor icing, even after the ice has been removed, full carburetor
heat should be used to prevent further ice formation. A carburetor
temperature gauge, if installed, is very useful in determining when to
use carburetor heat.
Whenever the throttle is closed during flight, the engine cools rapidly
and vaporization of the fuel is less complete than if the engine is
warm. Also, in this condition, the engine is more susceptible to
carburetor icing. Therefore, if you suspect carburetor icing conditions
and anticipate closed-throttle operation, adjust the carburetor heat to
the full ON position before closing the throttle, and leave it on during
the closed-throttle operation. The heat will aid in vaporizing the fuel,
and help prevent the formation of carburetor ice. Periodically, open the
throttle smoothly for a few seconds to keep the engine warm, otherwise
the carburetor heater may not provide enough heat to prevent icing.
The use of carburetor heat causes a decrease in engine power, sometimes
up to 15 percent, because the heated air is less dense than the outside
air that had been entering the engine. This enriches the mixture. When
ice is present in an airplane with a fixed-pitch propeller and
carburetor heat is being used, there is a decrease in r.p.m., followed
by a gradual increase in r.p.m. as the ice melts. The engine also should
run more smoothly after the ice has been removed. If ice is not present,
the r.p.m. will decrease, then remain constant. When carburetor heat is
used on an airplane with a constant-speed propeller, and ice is present,
a decrease in the manifold pressure will be noticed, followed by a
gradual increase. If carburetor icing is not present, the gradual
increase in manifold pressure will not be apparent until the carburetor
heat is turned off.
It is imperative that a pilot recognizes carburetor ice when it forms
during flight. In addition, a loss of power, altitude, and/or airspeed
will occur. These symptoms may sometimes be accompanied by vibration or
engine roughness. Once a power loss is noticed, immediate action should
be taken to eliminate ice already formed in the carburetor, and to
prevent further ice formation. This is accomplished by applying full
carburetor heat, which will cause a further reduction in power, and
possibly engine roughness as melted ice goes through the engine. These
symptoms may last from 30 seconds to several minutes, depending on the
severity of the icing. During this period, the pilot must resist the
temptation to decrease the carburetor heat usage. Carburetor heat must
remain in the full-hot position until normal power returns.
Since the use of carburetor heat tends to reduce the output of the
engine and also to increase the operating temperature, carburetor heat
should not be used when full power is required (as during takeoff) or
during normal engine operation, except to check for the presence or to
remove carburetor ice.
Carburetor air temperature gauge
Some airplanes are equipped with a carburetor air temperature gauge,
which is useful in detecting potential icing conditions. Usually, the
face of the gauge is calibrated in degrees Celsius (°C), with a yellow
arc indicating the carburetor air temperatures where icing may occur.
This yellow arc typically ranges between -15°C and +5°C (5°F and 41°F).
If the air temperature and moisture content of the air are such that
carburetor icing is improbable, the engine can be operated with the
indicator in the yellow range with no adverse effects. However, if the
atmospheric conditions are conducive to carburetor icing, the indicator
must be kept outside the yellow arc by application of carburetor heat.
Certain carburetor air temperature gauges have a red radial, which
indicates the maximum permissible carburetor inlet air temperature
recommended by the engine manufacturer; also, a green arc may be
included to indicate the normal operating range.
Outside air temperature gauge
Most airplanes also are equipped with an outside air temperature (OAT)
gauge calibrated in both degrees Celsius and Fahrenheit. It provides the
outside or ambient air temperature for calculating true airspeed, and
also is useful in detecting potential icing conditions.
Fuel injection systems
In a fuel injection system, the fuel is injected either directly into
the cylinders, or just ahead of the intake valve. A fuel injection
system is considered to be less susceptible to icing than the carburetor
system. Impact icing on the air intake, however, is a possibility in
either system. Impact icing occurs when ice forms on the exterior of the
airplane, and blocks openings such as the air intake for the injection
The air intake for the fuel injection system is similar to that used in
the carburetor system, with an alternate air source located within the
engine cowling. This source is used if the external air source is
obstructed. The alternate air source is usually operated automatically,
with a backup manual system that can be used if the automatic feature
A fuel injection system usually incorporates these basic components—an
engine-driven fuel pump, a fuel/air control unit, fuel manifold (fuel
distributor), discharge nozzles, an auxiliary fuel pump, and fuel
Figure 10: Fuel injection system.
The auxiliary fuel pump provides fuel under pressure to the fuel/air
control unit for engine starting and/or emergency use. After starting,
the engine-driven fuel pump provides fuel under pressure from the fuel
tank to the fuel/air control unit. This control unit, which essentially
replaces the carburetor, meters fuel based on the mixture control
setting, and sends it to the fuel manifold valve at a rate controlled by
the throttle. After reaching the fuel manifold valve, the fuel is
distributed to the individual fuel discharge nozzles. The discharge
nozzles, which are located in each cylinder head, inject the fuel/air
mixture directly into each cylinder intake port.
Some of the advantages of fuel injection are:
- Reduction in evaporative icing.
- Better fuel flow.
- Faster throttle response.
- Precise control of mixture.
- Better fuel distribution.
- Easier cold weather starts.
Disadvantages usually include:
- Difficulty in starting a hot engine.
- Vapor locks during ground operations on hot days.
- Problems associated with restarting an engine that quits because of
Superchargers and turbosuperchargers机械增压器
To increase an engine´s horsepower, manufacturers have developed
supercharger and turbosupercharger systems that compress the intake air
to increase its density. Airplanes with these systems have a manifold
pressure gauge, which displays manifold absolute pressure (MAP) within
the engine´s intake manifold.
On a standard day at sea level with the engine shut down, the manifold
pressure gauge will indicate the ambient absolute air pressure of 29.92
in. Hg. Because atmospheric pressure decreases approximately 1 in. Hg
per 1,000 feet of altitude increase, the manifold pressure gauge will
indicate approximately 24.92 in. Hg at an airport that is 5,000 feet
above sea level with standard day conditions.
As a normally aspirated aircraft climbs, it eventually reaches an
altitude where the MAP is insufficient for a normal climb. That altitude
limit is the aircraft´s service ceiling, and it is directly affected by
the engine´s ability to produce power. If the induction air entering the
engine is pressurized, or boosted, by either a supercharger or a
turbosupercharger, the aircraft´s service ceiling can be increased. With
these systems, you can fly at higher altitudes with the advantage of
higher true airspeeds and the increased ability to circumnavigate