PP 02

What is meant by a cam-ground piston?. Machined according to crankcase curvature. Machined perfectly circular. Manufactured slightly oval in cross-section. Machined to match cylinder taper.

Why are small holes drilled in piston bosses leading to the piston pins?. o balance piston weight. To vent compression gases. To increase fuel atomization. To lubricate the piston pins.

What is used on most aircraft engines to prevent the piston pins from scoring the cylinder walls?. Stainless rings. Cylinder lube grooves. Brass or aluminum plugs in ends of piston pin. Floating steel end caps.

Is the greater diameter of a piston parallel or perpendicular to the piston pin?. Parallel to the piston pin. Perpendicular to the piston pin. Equal in both directions. Depends on bore finish.

What material are piston rings normally made of?. Aluminum. Gray cast iron. Chrome moly steel. Beryllium bronze.

What is meant by an interference fit between a valve seat and a valve face?. Valve clamped by springs. Valve face is conical, seat is spherical. Valve and seat angle differ about 1° for a better seal. Seat is machined undersize and hammered into place.

Why do aircraft engines use more than one valve spring per valve?. Reduce spark plug fouling. Maintain constant compression. Prevent valve surge or bouncing. Reduce valve temperature.

What are the two types of connecting rods used in a radial engine?. Primary and secondary rods. Master and articulating rods. Crank and eccentric rods. Articulated and thrust rods.

What is the function of the sludge plug used in an aircraft engine’s crankshaft?. o balance crankshaft rotation. To hold lubrication during shutdown. Collect carbon and sludge deposits. Seal the crankshaft oil passage.

What is the purpose of dynamic dampers used on an aircraft engine crankshaft?. Prevent detonation. Control lubrication pressure. Reduce whip and vibration. Seal counterweights.

What is the gear ratio on a propeller reduction system with a sun gear of 75 teeth, ring gear of 125 teeth, and three planet gears with 40 teeth?. 1.3:1. 1.5:1. 1.6:1. 2.0:1.

In what kind of bearings does the camshaft of a horizontally opposed aircraft engine ride?. Roller bearings. Ball bearings. Plain bearings. Tapered bearings.

When is valve clearance greatest on a radial engine — hot or cold?. Always the same. When engine is cold. When engine is hot. Depends on spring tension.

What happens if valve clearances are set with too little gap?. Valve opens late and closes early. Valve temperature increases and loses compression. Valve opens early and closes late. Ignition timing changes.

Why are propeller reduction gears used on some aircraft engines?. Increase propeller RPM. Reduce propeller drag. Allow max engine power at lower propeller RPM. Prevent carburetor ice.

The planetary gear reduction system has a Bell gear with 84 teeth, planet gears 36 teeth, and a sun gear 42 teeth. What is the gear ratio?. 1.3:1. 1.5:1. 1.75:1. 2.0:1.

What percentage of heat does an aircraft reciprocating engine waste?. 30%. 50%. 70%. 90%.

What percentage of the wasted heat leaves through the exhaust?. 25%. 30%. 45%. 60%.

During ground operation, what position should the cowl flaps be placed in?. Closed. Half open. Fully open. Vented only during taxi.

How does the exhaust augmentor system help cool the engine?. Increases oil flow at high RPM. Circulates coolant through cylinders. Creates low pressure in the augmentor tube to draw cooling air. Vents carburetor heat over cylinders.

What can be done if cylinder cooling fins are cracked or broken?. Replace cylinder immediately. Dress or contour fins. Sandblast cooling area. Install secondary fin rings.

Many aircraft without cowl flaps have a lip on the lower cowl. How does this aid engine cooling?. Redirects exhaust gases. Cools the oil sump. Creates low pressure to draw air through engine. Increases ram air velocity at propeller.

What six things does engine oil do?. Lubricates, cools, seals, cushions, protects against corrosion, cleans. Lubricates, heats, filters, expands, balances, senses pressure. Cools, insulates, pressurizes, seals, stores, atomizes. Cleans, burns, compresses, cools, vents, ignites.

What is meant by viscosity of engine oil?. Oil’s resistance to temperature. Oil’s internal resistance to flow. Oil’s ability to absorb water. Oil’s ability to resist corrosion.

What is S.S.U. the abbreviation of?. Steam Seconds Units. Standard Service Units. Saybolt Seconds Universal. Specific Shear Units.

Aviation oil W100 has approximately the same viscosity as which SAE oil?. 20 weight. 30 weight. 50 weight. 75 weight.

What is meant by the cloud point of engine oil?. Temperature at which oil begins to evaporate. Temperature at which wax in oil begins to solidify. Temperature at which oil loses lubrication. Temperature at which oil becomes milky from fuel.

What is meant by the flash point of engine oil and how does it differ from the fire point?. Flash point = constant flame; fire point = momentary ignition. Flash point = temperature oil freezes; fire point = wax melts. Flash point = momentary ignition; fire point = sustained combustion. Flash point = temp oil emits vapors; fire point = no vapors.

What is one of the chief limitations of straight mineral oil for use in aircraft engines?. It causes detonation. It oxidizes at high temperature or when aerated. It attracts water. It damages valve seats.

What is the main limitation of detergent oil for aircraft engine lubrication?. Low lubricity. It loosens deposits and may plug galleries. It foams when cold. It has no thermal stability.

What has better lubricating properties, straight mineral oil or ashless dispersant oil?. Straight mineral oil. Ashless dispersant oil. Both the same. Depends on altitude.

Is it permissible to use mineral oil with ashless dispersant oil?. No, never compatible. Yes, always compatible. Yes, sometimes compatible. Only during hot weather.

In what units is oil viscosity measured for aircraft reciprocating engines?. PSI. Poise. Centistokes. Saybolt Seconds Universal (SSU).

Is oil temperature usually measured as it enters the engine, or as it leaves the engine?. As it leaves the engine. As it enters the engine. In the sump. At the oil filter.

What is the function of the oil bypass valve in an oil strainer in a reciprocating engine?. Prevents oil foaming. Opens if screen plugs to maintain oil flow. Shuts off oil during cold start. Recirculates oil through cylinders.

Which oil pump has the greatest capacity, the engine oil pump or the scavenger pump? Why?. Engine pump; oil is cool. Engine pump; oil may contain vapor. Scavenger pump; oil has more volume and air bubbles. Scavenger pump; pressure is higher.

What is a surge protection valve in an aircraft reciprocating engine oil cooler?. Valve to maintain oil viscosity. Valve that bypasses cooler to prevent clogged oil lines. Valve that allows oil to flow around cooler if congealed. alve that controls oil temperature electronically.

What is meant by oil dilution?. Mixing oil with water. Adding fuel to oil to reduce viscosity for cold start. Removing old oil from the sump. Heating oil before shutdown.