Ch 8 Powerplants Flashcards
Define flat rate
Means that a given horsepower may be reached at a given temperature, such as 80 degrees
(An engine having a HP rating at higher than standard day temperatures)
Define torque limited
Used in regards to power engine may deliver to transmission- which is torque limited or capable of withstanding only so much of the engines potential power output
(A limitation placed on the drive train in regards to power output of the engine)
Purpose of engine alignment
Ensures driveshaft alignment between engine output and transmission input
To measure rpm on a shaft turbine, what is used?
Tachometer
There’s
- Dual Tach
- Tripple Tach (2 engines & 1 M/R)
- married needles (if needles in line= all good)
N1 or Ng
Compressor or gas producer
N2 or Nf
Power turbine
What does the N2 tachometer indicate and what type is it?
- dual tachometer
- indicates engine and main rotor output
Define droop
If the N2 rpm can’t maintain or lags behind as collective is increased
What are causes of droop?
Overloaded Helicopter
Worn engine
Incorrect adjustment
What do these acronyms stand for?
EGT, ITT, TIT, TOT
EGT- Exhaust Gas Temp.
ITT- Inner Turbine Temp.
TIT- Turbine Inlet Temp.
TOT- Turbine Outlet Temp.
Particle Separators purpose
Device used to remove foreign material from the air entering the engine
(By means of centrifugal force)
What was modified on fixed wing engines to be put on helicopters?
- Lubrication System (oil sump relocated and modification to/ Intro of oil scavenge system)
- increased Power Requirements (added fan/oil pump= work harder and its constant speed, blade pitch change= more drag= more power to over come)
- Cooling System (not cooled from prop/ram airflow so fan added to produce required cooling airflow)
Other than the modifications to the lubrication/cooling systems as well as increase in power requirements, what other modifications were made to the engines?
- Method of controlling power (need constant rpm)
- increased idle rpm
- shortened life (result of modifications and higher power settings needed)
- carburetor heat, superchargers, fuel injection, transient rpm ranges, shortened life TBO 1200-2000 (R22)
How do cracks form on cooling fan? And what do you do with a cracked fan?
- have to replace
- caused by out of balance/vibrations and centrifugal force
Maintenance problems?
- location of accessories (L/H side of engine on R/H side of helicopter)
- unable to easily rotate crankshaft (special tooling to allow to turn engine)
- removal and install of engine a lot harder on helicopter than fixed wing
Correlation System on what type of engine?
Reciprocating only
Before Rigging Correlation System, what must be rigged first?
Collective
Throttle rigging should never be attempted unless collective has been properly rigged
Turbine engines for weight and power, what 2 things are helicopters referred to?
- Flat rated (given HP may be reached at a given temp.)
- Torque limited (amount of power that engine may deliver to transmission-always watch torque gauge)
What is droop compensation? Purpose and prevents?
- a linkage between the collective pitch control and turbine speed governor
- adjusts for increased load. The rotor places on engine as collective pitch is increased
- prevents rotor speed decreasing as load applied
Main difference between droop compensation and correlation System?
Correlation is directly linked to Fuel Control whereas the Droop Compensator isn’t connected to Fuel System at all (connected to governor which tells FCU more fuel-it’s predictive)
If adjust beep switch too low? Too high?
Too low- lose alt.
Too high- overspeed= blade stall
(Rig governor position with beep switch and collective position- ICC beep switch /secondary&primary control, twist grip is primary)
Functions of twist grip are:
-mechanical control of internal shut-off valve of FCU (N1)
Purpose of droop comp. linkage?
To change governor position mechanically to anticipate required action as the collective is moved
Beep switch purpose?
Trims N2 rpm which trims rotor speed
