Reciprocating engines

100問 • 1年前

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When is the fuel/air mixture ignited in a conventional reciprocating engine? a. When the piston has reached top dead center of the intake stroke. b. Shortly before the piston reaches the top of the compression stroke. c. When the piston reaches top dead center on the compression stroke.

Shortly before the piston reaches the top of the compression stroke.

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.

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.

Excessive valve clearance in a piston engine

decreases valve overlap.

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 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.

Some aircraft engine manufactures equip their product with choked or taper-ground cylinders in order to

Provide a straight cylinder bore at operating temperatures.

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 reduce density of the air drawn into the cylinders.

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 positioned past top dead center.

The valve clearance of an engine using hydraulic lifters, when the lifters are completely flatl, or empty, should not exceed

a specified amount above zero.

What does valve overlap promote?

Better scavenging and cooling characteristics.

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 cylinde

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

may be a result of abnormal plain type bearing wear and is cause for further investigation.

Master rod bearings are generally what type?

Plain

A hissing sound from the exhaust stacks when the propeller is being pulled through manually indicates

exhaust valve blow-by

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

When will small induction system air leaks have the most noticeable effect on engine operation?

At low RPM.

What special procedure must be followed when adjusting the values of an engine equipped with a floating cam ring?

Eliminate cam bearing clearance when making valve adjustment.

Valve overlap is defined as the number of degrees of crankshaft travel

during which both valves are off their seats. b. between th

Which of the following engine servicing operations generally requires engine pre-oiling prior to starting the engine?

Engine installation.

What is the best indication of worn valve guides?

High oil consumption.

How may it be determined that a reciprocating engine with a dry sump is pre-oiled sufficiently? a. The engine oil pressure gauge will indicate normal oil pressure. b. Oil will flow from engine return line or indicator port. c. When the quantity of oil specified by the manufacturer has been pumped into the engine.

Oil will flow from engine return line or indicator port.

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.

Excessive valve clearances will cause the duration of valve opening to

decrease for both intake and exhaust valves.

Which statement is correct regarding a four- stroke cycle aircraft engine?

The intake valve closes on the compassion stroke.

A characteristic of dyna- focal engine mounts as applied to aircraft reciprocating engines is that the

shock mount point toward the engine’s center of gravity.

Which statement pertaining to fuel/air ratios is true?

The mixture ratio which gives the best power is richer than the mixture ratio which gives maximum economy.

One cause of after firing in an aircraft engine is

an excessively rich mixture.

The horsepower developed in the cylinders of a reciprocating engine is known as the

indicated horsepower

An increase in manifold pressure with a constant RPM will cause the bearing load in an engine to

increase

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

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 primary purpose in setting proper valve timing and overlap is to

obtain the best volumetric efficiency and lower cylinder operating temperatures.

Engine crankshaft run out 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

A condition that can occur in radial engines but is unlikely to occur in horizontally opposed engines is

hydraulic lock.

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.

Excessive valve clearance results in the valves opening

late and closing early.

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 or defective ring(s) indication.

Engine operating flexibility is the ability of the engine to

run smoothly and give the desired performance at all speeds

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 cylinders.

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.

Grinding the valves of a reciprocating engine to a feather edge is likely to result in

Pre-ignition and burned valves.

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

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 nitrided.

The purpose of two or more valve springs in aircraft engines is to

eliminate valve spring surge.

What could cause excessive pressure buildup in the crankcase of a reciprocating engine?

Plugged crankcase breather.

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 2600 from top dead center compression stroke No. 1 cylinder. How can this indication usually be interpreted?

A normal indication.

One of the best indicators of reciprocating engine combustion chamber problems is

spark plug condition.

If the ignition switch is moved from BOTH to either LEFT or RIGHT during a magneto check, a normal operation is usually indicated by

slight drop in RPM.

The primary concern in establishing the firing order for an opposed engine is to

provide for balance and eliminate vibration to the greatest extent possible.

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.

If the hot clearance is used to set the valves when the engine is cold, what will occur during operation of the engine?

The valves will open late and close early.

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.

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 bearing is least likely to be a roller or ball bearing?

Master rod bearing (radial engine).

On which strokes are both valves on a four-stroke cycle reciprocating aircraft engine open?

Exhaust and intake.

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.

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.

Some cylinder barrels are hardened by

nitriding

Why does the smoothness of operation of an engine increase with a greater number of cylinders?

The power impulses are spaced closer together.

Which of the following is a characteristic of a thrust bearing used in most radial engines?

Deep-groove ball.

Which condition would be the least likely to be caused by failed or failing engine bearings?

Low oil temperatures.

Valve clearance changes on opposed-type engines using hydraulic lifters are accomplished by

push rod replacement.

The floating control thermostat, used on some reciprocating engine installations, helps regulate oil temperature by

controlling air flow through the oil cooler.

Which of the following would most likely cause a reciprocating engine to backfire through the induction system at low RPM operation?

Lean mixture.

What is the purpose of a power check on a reciprocating engine?

To determine satisfactory performance.

To what altitude will a turbo charged engine maintain sea level pressure?

Critical altitude.

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.

If the crankshaft run out readings on the dial indicator are plus .002 inch and minus .003 inch, the run out is

.005 inch.

Full-floating piston pins are those which allow motion between the pin and

both the piston and the small end of the connecting rod.

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.

When does valve overlap occur in the operation of an aircraft reciprocating engine?

At the end of the exhaust stroke and the beginning of the intake stroke.

Which statement is correct regarding engine crankshafts?

Moveable counterweights serve to reduce the torsional vibrations in an aircraft reciprocating engine.

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

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 warm up.

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.

The five events of a four-stroke cycle engine in the order of their occurrence are

intake, compression, ignition, power, exhaust.

Ignition occurs at 28° BTDC on a certain four-stroke cycle engine, and theintake valve opens at 15° BTDC. How many degrees of crankshaft travel after ignition does the intake valve open? (Consider one cylinder only.)

373°.

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.

Backfiring through the carburetor generally results from the use of

an excessively lean mixture.

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.

Which of the following conditions would most likely lead to detonation?

Use of fuel with too low an octane rating.

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

Cam-ground pistons are installed in some aircraft engines to

provide a better fit at operating temperatures.

What is an advantage of using metallic-sodium filled exhaust valves in aircraft reciprocating engines?

Reduced valve operating temperatures.

The operating temperature valve clearance of a radial engine as compared to cold valve clearance is

greater

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.

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 700: BBDC. Intake closes 45°: ABDC. Exhaust closes 10°: ATDC.

245°.

What tool is generally used to measure the crankshaft rotation in degrees?

Timing disk.

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.

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.

Compression ratio is the ratio between the

cylinder volume with piston at bottom dead center and at top dead center.

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.

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.

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.

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.

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 the RPM.

Which of the following will be caused by excessive valve clearance of a cylinder on a reciprocating aircraft engine?

Reduced valve overlap period.

If the intake valve is opened too early in the cycle of operation of a four stroke cycle engine, it may result in

backfiring into the induction system.

100

If an engine cylinder is to be removed, at what position in the cylinder should the piston be?

Top dead center.

airlaw

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