Ams 271 Unit 6

How does a sonic venturi work?

-As turbocharger air passes through a sonic venturi, it is accelerated to a transonic speed to produce a shock wave. -shockwave slows the remaining airflow thereby limiting the amount of air entering the cabin.

How does an absolute pressure controller work

-Bellows that expands and contracts moving a variable restrictor valve(controls oil flowing through waste gate) -senses upper deck pressure

Purpose of carb heat

-Heats induction air before entering engine -prevents carb icing

Purpose of CAT

-Warn of possible icing condition -warn of possible detonation

What is bootstrapping and when does it occur?

-continual drift or increase in MAP pressure -occurs when a turbocharger system senses a small change in temp/rpm and continually changes the turbo output to establish equilibrium

Baffles installed between cowling and engine...

-divide engine compartment into upper and lower halves -force air to flow from the upper portion to the lower -intercyinder baffles direct air between the cylinders

Why is it easier to replace exhaust system components instead of repair?

-hard to determine exact allow -alloys can be difficult to weld -grain structure changes during use

Where are the reference pressures used to regulate turbocharger pressure located?

-shrouded fuel injector nozzles -Fuel Pumps -Fuel Flow gages

two stage supercharger

2 impeller ratios 8:1 and 12:1 internally gear driven

What percent of heat generated by recip a/c is used for useful work?

30%

What percent of heat generated by recip a/c must be removed from engine/ oil by cooling system?

30%

What percent of heat generated by recip a/c is expelled through exhaust?

40%

Exhaust systems are commonly made from

CRES monel inconel

Where is CAT located

Carb air inlet

How is bootstrapping reduced?

Differential pressure controller

What heats the incoming air?

Heat exchanger

Purpose of supercharging?

Increase the manifold absolute pressure (MAP) of an engine at high altitude

Sonic venturi

Limits the amount of air that can be delivered to the cabin for pressurization

purpose of a turbocharger?

Maintains rated power up to critical altitude

Must must all repairs on exhaust systems meet?

Manufacturers specifications

Rapid throttle advancement can cause?

Overboost overshoot

Airflow for cooling?

Ram air enters through cowling openings -routed rear and downward(baffles/ deflectors) -exits through the bottom of cooling

Air Box

Routes induction air from the filter to the fuel metering device

2 major parts of turbo?

Turbine(exhaust) compressor(driven by turbine)

blast tubes attached at?

aft air deflector

What is the purpose augmentor exhaust?

aids in engine cooling by causing a low pressure area aft of the engine

Expansion joints are used to?

allow for thermal expansion and absorb vibration and flexing

When is differential controller used?

below full throttle -exceeding 2'-4' hg pressure differential causes controlled to reposition waste gate

Where are the attachment points of induction pipes

bolted to the cylinder intake port and the the manifold/plenum

coolant pump

circulates coolant

Purpose of a shroud in exhaust system?

collect heat for cabin and indiction system

plenum

collects compressed air and routes it to cylinders

Purpose of Studs in muffler?

concentration point to radiate heat

waste gate

controls flow of exhaust gas to turbine

thermostat

controls the cooling system temperature

purpose of aftercooler?

cools compressed air to prevent detonation

Where do half of exhaust system failures come from?

cracks and corrosion on surface of heat exchanger

What happens if there is induction icing with a constant speed propellor?

decrease in MAP

what 2 controllers are used in lycoming turbo systems?

differential pressure controller density controller

purpose of blast tubes

direct cooling air to engine accessories -magnetos -alternators -generators

Cowl Flaps

doors on the bottom aft of cowling the control the amount of air exiting the cowling -controlled by the pilot by push/pull rods or electric motors

Induction pipes

ducting that runs from the air or fuel metering device to the cylinders

What happens if there is icing in the induction system with a fixed pitch propellor?

engine rpm decreases

What type of liquid is used on a liquid cooling system?

ethylene glycol mixed with distilled water

What happens to mixture if there is an induction leak after the carb?

excessively lean

Power recovery turbo

exhaust gas driven turbine that is connected to engine crankshaft -NO increase of map

cowling seals

flexible rubber seals attached to the baffles to prevent air flow from leaking between the cowling and baffles

When is density controller used?

full throttle -regulates bleed oil flow fro waste gate acuators

Exhaust systems are damaged by?

high heat corrosive gasses vibration poor maintenance

what drives a turbo?

hot exhaust air

Burned paint on the engine cylinders is an indication of

hot spot

Purpose of turbo-supercharger?

increase boost at sea level as well as higher altitudes

waste gate actuator

increasing the oil pressure closes the waste gate spring tension moves the waste gate to open position

two ways a supercharger can be driven?

internal Gear driven

What can cause severe burning due to high pressure in a turbocharger exhaust system?

leaks

advantages of air cooled engine

lighter less effected by cold weather

What is a side effect of turning carb heat on?

loss in engine power

manually controlling turbos is accomplished by?

manual linkage of throttle and waste gate

how are turbos controlled?

manually by pilot automatic through oil pressure

what is critical altitude?

max altitude at which an engine can maintain a specified power output

which filter can be serviced instead of replaced?

mesh type filters (some pleated paper can be)

where is collector exhaust system used?

modern 4 and 6 cylinder opposite engines

Characteristics of APC oil operation

oil flows out of waste gate actuator faster than it can flow in

advantages of liquid cooling

operating temp sis more uniform and easily controlled engine is quieter moving parts can be machined to closer tolerances

When does pressure relief valve open?

pressure exceeds 1' to 1.5'

pressure relief valve

protects the engine from overboost opens when map is within 1" of max rated pressure

cooling fins

provide large surface area exposed to the cooling airflow

What are baffles used for?

quiet exhaust noise

Purpose of baffles/deflectors?

redirect airflow to provide effective cooling for engine

Purpose of a tapered opening in exhaust pipes?

reduce noise

What does a radiator do in liquid cooled system?

removes heat from the coolant

cracked cylinder fins may be repaired by

removing the damage with a grinder filing area to smooth contour - ALWAYS refer to overhaul manual for cooling fin repair

deteriorated cowling seals should be

replaced

Difference between VAPC and APC

restrictor valve seat position controlled by a cam that is actuated by a throttle

Types of exhaust systems

short stack open stack collector system

single stage supercharger

single speed impeller with one stage of compression -8:1 nominal

How can symptoms of severe vibration be observed on exhaust system?

sooty streaks

What is overshoot?

turbocharger momentarily exceeds MAP

What happens if there is an induction leak before the turbo?

unfiltered air

what does the density controlled sense?

upper deck

what does the pressure differential controller sense?

upper deck and manifold pressure

Common inspection areas on exhaust system?

welds bends joints internal muffler baffles

Types of induction filters

wetted mesh wire mesh pleated paper polyurethane