EMB120 Power Plant Systems

Question 1

What Engines does the 120 have?

Answer 1

P&W 118
P&W 118(a)
P&W 118(b)

Question 2

What is the difference in the engines?

Answer 2

The (a) and (b) engines have better internals that allow the engine to stay cooler longer

Question 3

What kind of Prop does it have?

Answer 3

Hamilton Sunstrane 14RF-9

4 Blades

Question 4

How many compressors does each engine have?

Answer 4

2 compressors

Question 5

What is the TMM?

Answer 5

Turbo Machinery Module

Question 6

What is all run/powered on the TMM?

Answer 6

Starter/Generator
HMU
Fuel Pump
Oil Pump

Question 7

What is the HMU?

Answer 7

Hydro Mechanical Metering Unit
The Mechanical Fuel controller, it take engine inputs, pressures and settings and creates a “fuel schedule”
gives a range of fuel to the engine

the carburetor or fuel injection system

Question 8

What is the RGB?

Answer 8

Reduction Gear Box

Question 9

What is run/powered by the RGB?

Answer 9

Auxiliary Feather Pump
Hydraulic Pump
Auxiliary Generator 
PCU Oil Pump
Over Speed Governor 
PCU

Question 10

What is the PCU?

Answer 10

Propeller Control Unit
Primary governor
Controls prop speed and pitch

Question 11

Are the Compressors and the power turbine connected

Answer 11

No, the compressor section creates enough airflow to the combustion section to sustain continuous combustion. The turbine section converts energy from the expanding gasses exiting the combustion chamber into rotational force used to drive the compressors, propeller, and accessories.

Question 12

Do the turbines spin different directions?

Answer 12

yes to help prevent torque effect

Question 13

How much horse power is the engine rated for?

Answer 13

1800 SHP

Question 14

Roughly how much air used for cooling and for the fire in the engine?

Answer 14

25% to burn

75% to cool

Question 15

What kind of oil system does the engine have?

Answer 15

Pressure system

Question 16

How much oil can the system hold?

Answer 16

2.4 Gallons

Question 17

Is the oil pressure gage and the oil light connected?

Answer 17

No

Question 18

How many fuel nozzles does each engine have?

Answer 18

14 that produce a continuous flow of fuel

Question 19

How many igniters does the aircraft have?

Answer 19

2 and they are only on during start

Question 20

What is a Hot Start?

Answer 20

When there is either too much fuel or not enough air the T6 temp rises very rapidly

Question 21

What is a Hung Start?

Answer 21

A hung start is a start that begins but doesn’t finish properly and gets stuck

Question 22

What is the EEC?

Answer 22

Electronic Engine Control
takes info from the HMU and other engine inputs and fine tunes the HMU fuel schedule

protected against Compressor stalls

Fixed torque Climb - Sets the power and it attempts to hold the same torque during climb

Question 23

What happens at 14,000ft?

Answer 23

when climbing through 14,000ft The fuel gets too rich for the EEC so the HMU de-enriched the fuel schedule so the EEC can properly utilize the fuel schedule. when descending back through 14,000 the HMU will re-enrich the fuel schedule. If the re-enrichment doesn’t happen by 10,000ft you will get a triple chime and “ENGINE CONTROL”

Question 24

what is the max RPM of the Propeller?

Answer 24

1300RPM

Question 25

How much oil is the AUX oil tank?

Answer 25

0.3 gallons enough oil to go from full forward to full feather once. If the Engine is still spinning it will refill itself

Question 26

Explain how the prop system works.

Answer 26

The PCU is commanded by the power levers and the condition levers. When a pitch change is commanded, the PCU changes the rotational speed of the transfer tube (normally rotates at the same speed as the prop) either faster or slower then the prop speed. This speed change is obtained by 2 distinct oil pressures; supply and control. The supply pressure actuates to increase pitch and control pressure actuates to decrease pitch. When the transfer tube speed is increased or decreases it opens 1 of 2 chambers. When oil enters either chamber it moves actuator piston which then changes the pitch of the blade

Question 27

What conditions must be met for auto feather to work properly?

Answer 27

Switch to on PLA greater then 62 degrees Tq of both engines must be above 62%

Question 28

Why does prop sync have to be off during takeoff?

Answer 28

Because the left engine is the Master and the right engine is slaved to the left. so if the left engine were to auto feather on takeoff then the right engine would also auto feather because it slaved to the left engine

Question 29

How close do the props have to be for prop sync to work?

Answer 29

2.5%

Question 30

How many turbine does the engines have? How many are power turbines?

Answer 30

4 turbines, 2 power turbines

Question 31

What should be Ground idle Nh with EEC on? Flight idle?

Answer 31

Ground 62% | Flight 72%

Question 32

What all does the EEC do?

Answer 32

Np fuel gov (reverse) Smooth fuel Governing to prevent compressor stalls Fixed torque climb

Question 33

What happens if EEC fail below 14000k ft?

Answer 33

They fail fixed at whatever schedule they are in

Question 34

What is the flight idle stop? How does it work?

Answer 34

Prevent the power levers from going into reverse while in flight. A weight on wheel switch removes the block when on the ground

Question 35

When is prop heat available?

Answer 35

Oil pressure 40psi

Question 36

What ways can the prop be feather?

Answer 36

Mechanically- condition lever Electronically- electric feather switch Auto feather Low pitch secondary stop

Question 37

What is the low pitch secondary back stop?

Answer 37

While in flight if props are in the reverse range, it sends the props back towards feather using the electronic feather solenoid. It won’t completely send the prop into feather

Question 38

What could be a reason for a beta light in flight?

Answer 38

Surging prop

Question 39

What keeps the prop and the selected speed?

Answer 39

Normal speed gov, uses a fly weight

Question 40

Explain the how the overspeed gov takes over?

Answer 40

The least selector valve chooses the lowest oil pressure between the normal speed gov and the overspeed gov. The normal speed gov has lower oil pressure then the overspeed gov in normal ops. If the normal speed gov fails, the pressure will increase making the overspeed gov oil pressure the lower of the 2. The least selector valve will then choose the overspeed gov.

Question 41

What Nh will the overspeed gov try to always maintain with oil pressure?

Answer 41

103%

Question 42

What Nh will the overspeed gov try and maintain if it can’t maintain 103%?

Answer 42

107%, it will pull fuel from the engine to try and maintain 107%

Question 43

What happens if the prop system looses oil pressure?

Answer 43

Fixed pitch prop