20 - Engines

Question 1

What engines are used on the EC175, and what are the basic principles?

Answer 1

• 2 x Pratt & Witney PT6C-67E engines (w. 1,800 shaft horsepower)

Compressor. | Combustion. | Turbine. | Exhaust.
-4-stage axial | -Reverse flow | -1-stage Compressor |
-1-stage centrifugal | annular | -2-stage Free Power |
-Bleed Off Valve (BOV) |

Question 2

What ‘P’ bleed air is used?

Answer 2

• P2.5: used for cooling and sealing of bearings
• P2.8: protects against surge (Nr/OAT); exits engine in the exhaust area
• P3: bleed air used for cabin/cockpit air heating.

Question 3

What engine cockpit controls are there?

Answer 3

• Eng Ctrl Sw.: Dbl-gated, 3-posn (OFF - IDLE - FLT)
• Eng ‘Repeater’ light: FIRE / FADEC / FLAMEOUT / LOW OIL PX
• SOV: closes fuel SOV in fuel line; powered directly from battery
• Crank: maximum 30 secs. No ignition, fuel or protection
• Trg Sw: simulates single engine performance - engine 2 only
• Chip burner: maximum 1 application/indication; maximum 2 applications/flight.

Question 4

Describe the FADEC system:

Answer 4

• 1 x EECU (electronic eng. ctrl unit) per engine (aft of engs); powered by NO SHED 1 &2
  - EECUs are dual channel and talk to each other, taking inputs from:
  - Eng Ctrl Panel, Maint. Ctrl Panel, Collective, Anticipatory Box (RVDT), Eng Sensor
• 1 x FCU (fuel control unit) per engine (RHS AGB)
  - contains Fuel Temp, Fuel Px, PMA N1 (N1 signal from here)
• N2, Tq, TOT, MOT, T1, MOP and FCU inputs to EECU (both channels) to Ctrl eng start.