Reciprocating Engines Flashcards
Which statement is true regarding bearings used in high-powered reciprocating aircraft engines?
there is less rolling friction when ball bearings are used than when roller bearings are employed
A condition that can occur in radial engines but is unlikely to occur in horizontally opposed engines is
hydraulic lock
Which condition would be the least likely to be caused by failed or failing engine bearings?
low oil temperature
What is the principal advantage of using propeller reduction gears?
to enable the engine rpm to be increased with an accompanying increase in power and allow the propeller to remain at a lower, more efficient rpm
Which of the following will decrease volumetric efficiency in a reciprocating engine?
1. Full throttle operation.
2. Low cylinder head temperatures.
3. Improper valve timing.
4. Sharp bends in the induction system.
5. High carburetor air temperatures.
3,4 and 5
Which of the following is a characteristic of a thrust bearing used in most radial engines?
deep groove ball
Which bearing is least likely to be a roller or ball bearing?
master rod bearing (radial engine)
The operating temperature valve clearance of a radial engine as compared to cold valve clearance is
greater
A nine-cylinder engine with a bore of 5.5 inches and a stroke of 6 inches will have a total piston
displacement of
1,283 cubic inches
The five events of a four-stroke cycle engine in the order of their occurrence are
intake, compression, ignition, power, exhaust
The primary concern in establishing the firing order for an opposed engine is to
provide for balance and eliminating vibration to the great extent possible
If fuel/air ratio is proper and ignition timing is correct, the combustion process should be completed
just after top center at the beginning of the power stroke
Grinding the valves of a reciprocating engine to a feather edge is likely to result in
pre ignition and burned valves
Which statement is correct regarding engine crankshafts?
moveable counterweights serve to reduce the torsional vibrations in an aircraft reciprocating
engine
On which strokes are both valves on a four-stroke cycle reciprocating aircraft engine open?
exhaust and intake
Master rod bearings are generally what type?
plain
The actual power delivered to the propeller of an aircraft engine is called
brake horsepower
Cam-ground pistons are installed in some aircraft engines to
provide a better fit at operating temperatures
Using the following information, determine how many degrees the crankshaft will rotate with both the
intake and exhaust valves seated.
Intake opens 15°: BTDC.
Exhaust opens 70°: BBDC.
Intake closes 45°: ABDC.
Exhaust closes 10°: ATDC
245 degrees
Some aircraft engine manufacturers equip their product with choked or taper-ground cylinders in order
to
provide a straight cylinder bore at operating temperatures
An aircraft reciprocating engine using hydraulic valve lifters is observed to have no clearance in its valve- operating mechanism after the minimum inlet oil and cylinder head temperatures for takeoff have been
reached. When can this condition be expected?
during normal operation
What tool is generally used to measure the crankshaft rotation in degrees?
timing disk
movement within the cylinder will be
at maximum velocity 90 degrees after TDC
If the intake valve is opened too early in the cycle of operation of a four-stroke cycle engine, it may
result in
back firing into the induction system
Some cylinder barrels are hardened by
nitriding
Which statement is correct regarding a four-stroke cycle aircraft engine?
the intake valve closes on the compression stroke
On which part of the cylinder walls of a normally operating engine will the greatest amount of wear
occur?
near the top of the cylinder
During overhaul, reciprocating engine exhaust valves are checked for stretch
with a contour or radius gauge
When is the fuel/air mixture ignited in a conventional reciprocating engine?
shortly before the piston reaches the top of the compression stroke
Ignition occurs at 28° BTDC on a certain four-stroke cycle engine, and the intake valve opens at 15°
BTDC. How many degrees of crankshaft travel after ignition does the intake valve open? (Consider one
cylinder only.)
373 degrees
What is the purpose of the safety circlet installed on some valve stems?
to prevent the valves form falling into the combustion chamber
Valve overlap is defined as the number of degrees of crankshaft travel
during which both valves are off their seats
The valve clearance of an engine using hydraulic lifters, when the lifters are completely flat, or empty,
should not exceed
specified amount above zero
If the exhaust valve of a four-stroke cycle engine is closed and the intake valve is just closed, the piston
is on the
compression stroke
How many of the following are factors in establishing the maximum compression ratio limitations of an
aircraft engine?
1. Detonation characteristics of the fuel used.
2. Design limitations of the engine.
3. Degree of supercharging.
4. Spark plug reach.
three
Full-floating piston pins are those which allow motion between the pin and
both the piston and the small end of the connecting rod
The primary purpose in setting proper valve timing and overlap is to
obtain the best volumetric efficiency and lower cylinder operating temperature
If the hot clearance is used to set the valves when the engine is cold, what will occur during operation of
the engine?
the valve will open late and close early
The purpose of two or more valve springs in aircraft engines is to
eliminate valve spring surge
During overhaul, the disassembled parts of an engine are usually degreased with some form of mineral
spirits solvent rather than water-mixed degreasers primarily because
water mixed degreaser residues may cause engine oil contamination in the overhauled engine
Why does the smoothness of operation of an engine increase with a greater number of cylinders?
the power impulses are placed closes together
Compression ratio is the ratio between the
cylinder volume with piston at bottom dead center and at top dead center
If the crankshaft runout readings on the dial indicator are plus .002 inch and minus .003 inch, the runout
.005 inch
(1) Cast iron piston rings may be used in chrome-plated cylinders.
(2) Chrome-plated rings may be used in plain steel cylinders.
Regarding the above statements,
both no. 1 and 2 are true
How is proper end-gap clearance on new piston rings assured during the overhaul of an engine?
by placing the rings in the cylinder and measuring the end gap with a feeler gauge
The volume of a cylinder equals 70 cubic inches when the piston is at bottom center. When the piston is
at the top of the cylinder, the volume equals 10 cubic inches. What is the compression ratio?
7:1
When cleaning aluminum and magnesium engine parts, it is inadvisable to soak them in solutions
containing soap because
some of the soap will become impregnated in the surface of the material and subsequently cause
engine oil contamination and foaming
What is the purpose of a power check on a reciprocating engine?
to determine satisfactory performance
What will be the likely result if the piston ring gaps happen to be aligned when performing a differential- pressure compression check on a cylinder?
a worn defective rings indication
Which of the following will be caused by excessive valve clearance of a cylinder on a reciprocating
aircraft engine?
reduced valve overlap period
The floating control thermostat, used on some reciprocating engine installations, helps regulate oil
temperature by
controlling airflow through the oil cooler
Which of the following would indicate a general weak-engine condition when operated with a fixed- pitch propeller or test club?
. lower than normal static rpm, full throttle operation
What is required by 14 CFR Part 43 Appendix D when performing an annual/100-hour inspection on a
reciprocating engine aircraft?
cylinder compression check
After spark plugs from an opposed engine have been serviced, in what position should they be
reinstalled?
next in firing order to the one from which they were removed and swapped bottom to top
Excessive valve clearance results in the valves opening
late and closing early
During routine inspection of a reciprocating engine, a deposit of small, bright, metallic particles which do
not cling to the magnetic drain plug is discovered in the oil sump and on the surface of the oil filter. This
condition
Maybe a result of abnormal plain type bearing wear and is cause for further investigation
A characteristic of dyna-focal engine mounts as applied to aircraft reciprocating engines is that the
shock mounts points toward the engines center of gravity
If metallic particles are found in the oil filter during an inspection,
the cause should be identified and corrected before the aircraft is released for flight
If the oil pressure gauge fluctuates over a wide range from zero to normal operating pressure, the most
likely cause is
low oil supply
What special procedure must be followed when adjusting the valves of an engine equipped with a
floating cam ring?
eliminating cam bearing clearance when making valve adjustment
Which of the following is most likely to occur if an overhead valve engine is operated with inadequate
valve clearances?
the valves will not seat positively during start and engine warmup
Excessive valve clearances will cause the duration of valve opening to
decease for both intake and exhaust valves
What does valve overlap promote?
better scavenging and cooling characteristics
At what speed must a crankshaft turn if each cylinder of a four-stroke cycle engine is to be fired 200
times a minute?
400 rpm
Engine crankshaft runout is usually checked
1. during engine overhaul.
2. during annual inspection.
3. after a ‘prop strike’ or sudden engine stoppage.
4. during 100-hour inspection.
1 and 3
Before attempting to start a radial engine that has been shut down for more than 30 minutes,
turn the propeller by hand three to four revolutions in the normal direction of rotation to check for
liquid lock
An engine misses in both the right and left positions of the magneto switch. The quickest method for
locating the trouble is to
check for one or more cold cylinder
A hissing sound from the exhaust stacks when the propeller is being pulled through manually indicates
exhaust valve blow-by
If the oil pressure of a cold engine is higher than at normal operating temperatures, the
engines lubrication system is probably operating normally
If an engine operates with a low oil pressure and a high oil temperature, the problem may be caused by
a
leaking oil dilution valve
Which fuel/air mixture will result in the highest engine temperature (all other factors remaining
constant)?
a mixture leaner than a manual lean mixture of .060
If an engine cylinder is to be removed, at what position in the cylinder should the piston be?
top dead center
The horsepower developed in the cylinders of a reciprocating engine is known as the
indicated horsepower
Engine operating flexibility is the ability of the engine to
run smoothly and give the desired performance at all speeds
Standard aircraft cylinder oversizes usually range from 0.010 inch to 0.030 inch. Oversize on automobile
engine cylinders may range up to 0.100 inch. This is because aircraft engine cylinders
have relatively thin walls and may be nitride
If the ignition switch is moved from BOTH to either LEFT or RIGHT during an engine ground check,
normal operation is usually indicated by a
slight drop in rpm
During ground check an engine is found to be rough-running, the magneto drop is normal, and the
manifold pressure is higher than normal for any given RPM. The trouble may be caused by
a dead cylinder
What is the best indication of worn valve guides?
high oil consumption
By use of a differential pressure compression tester, it is determined that the No. 3 cylinder of a nine- cylinder radial engine will not hold pressure after the crankshaft has been rotated 260° from top dead
center compression stroke No. 1 cylinder. How can this indication usually be interpreted?
a normal indication
When does valve overlap occur in the operation of an aircraft reciprocating engine?
at the end of exhaust stroke and the beginning of the intake stroke
What is an advantage of using metallic-sodium filled exhaust valves in aircraft reciprocating engines?
reduced valve operating temperatures
Valve clearance changes on opposed-type engines using hydraulic lifters are accomplished by
pushrod replacement
What is likely to occur if a reciprocating engine is operated at high power settings before it is properly
warmed up?
oil starvation of bearings and other parts
An increase in manifold pressure with a constant RPM will cause the bearing load in an engine to
increase
Direct mechanical push-pull carburetor heat control linkages should normally be adjusted so that the stop located on the diverter valve will be contacted
before the stop at the control lever is reached in both Hot and Cold positions
Reduced air density at high altitude has a decided effect on carburetion, resulting in a reduction of
engine power by
excessively enriching the fuel/air mixture
Increased water vapor (higher relative humidity) in the incoming air to a reciprocating engine will
normally result in which of the following?
decreased engine power at a constant rpm and manifold pressure
(1) Preignition is caused by improper ignition timing.
(2) Detonation occurs when an area of the combustion chamber becomes incandescent and ignites the
fuel/air mixture in advance of normal timed ignition.
Regarding the above statements,
neither no. 1 and 2 is true
Which of the following engine servicing operations generally requires engine pre-oiling prior to starting
the engine?
engine installation
During the inspection of an engine control system in which push-pull control rods are used, the threaded
rod ends should
be checked for the amount of thread engagement by means of the inspection holes
Which of the following conditions would most likely lead to detonation?
use of fuel with too low an octane rating
An unsupercharged aircraft reciprocating engine, operated at full throttle from sea level, to 10,000 feet,
provided the RPM is unchanged, will
lose power due to the reduced density of air drawn into the cylinders
Which of the following would most likely cause a reciprocating engine to backfire through the induction
system at low RPM operation?
lean mixture
How may it be determined that a reciprocating engine with a dry sump is pre-oiled sufficiently?
oil will flow from the engine return line or indicator port
What is the basic operational sequence for reducing the power output of an engine equipped with a
constant-speed propeller?
reduce the manifold pressure , then rpm
Which statement pertaining to fuel/air ratios is true?
the mixture ratio which gives the best power is richer than mixture ratio which gives maximum
economy
Backfiring through the carburetor generally results from the use of
An excessively lean, mixture
Which of these conditions will cause an engine to have an increased tendency to detonate?
1. High manifold pressure.
2. High intake air temperature.
3. Engine overheated.
4. Late ignition timing.
1,2,3
When will small induction system air leaks have the most noticeable effect on engine operation?
low rpm
To reduce the power output of an engine equipped with a constant-speed propeller and operating near
maximum BMEP, the
manifold pressure is reduced with the throttle control before the rpm is reduced with the propeller
control
One of the best indicators of reciprocating engine combustion chamber problems is
sparkplug condition
What could cause excessive pressure buildup in the crankcase of a reciprocating engine?
plugged crankcase breather
Excessive valve clearance in a piston engine
decreases valve overlap
To what altitude will a turbo charged engine maintain sea level pressure?
critical altitude
If air is heard coming from the crankcase breather or oil filler during a differential compression check,
what is this an indication of?
piston ring leakage
One cause of after-firing in an aircraft engine is
an excessively rich mixture
As the pressure is applied during a reciprocating engine compression check using a differential pressure
tester, what would a movement of the propeller in the direction of engine rotation indicate?
the piston was position past top
As the pressure is applied during a reciprocating engine compression check using a differential pressure
tester, what would a movement of the propeller in the direction of engine rotation indicate?
ans. the piston was position past top
the piston was position past top
