BV107-II Systems

Question 1

SYSTEM MALFUNCTIONS

You notice your Aft Transmission Pressure has dropped and your NR indication has dropped to zero. What has happened? What procedure would you apply?

Answer 1

Your Aft Transmission may be failing.

Carry out procedure for imminent transmission failure. (Nr tach generator reads from the Aft Transmission)

Question 2

ENGINE CONTROL

What do the positions of the ECL’s do?

Answer 2

Stop - fuel shut off and ignition disabled

Crank - fuel shut off, ignition system energized and the starter remains engaged until starter cutout at 46%ng or ECL is brought back to stop

Start - fuel is provided and fuel control is allowed to automatically start the engine. At ground idle the fuel control will govern to hold NG stable

Fly - fuel control is governing NF

Question 3

ELECTRICAL SYSTEM

What does the MASTER BATTERY switch do?

Answer 3

1) Completes the circuit between the BATT switch and main battery relay.
2) Ground to the AUX BATT switch.
3) Ground for the AC frequency control relays.
4) Closes the DC external power relay

Question 4

ELECTRICAL SYSTEM

What does the BATTERY switch do?

Answer 4

ON position closes the battery relay and the battery is connected to the DC bus.

OFF position power is interrupted to the relay and the battery is disconnected from the DC bus.

Question 5

ELECTRICAL SYSTEM

What does the INVERTER switch do?

Answer 5

DC voltage is supplied to the inverter from the DC bus. The inverter then delivers single-phase 115 VAC, 400 Hz power to the SAS and the two phase-B instrument buses. (Used to power instruments during DC start up or when no AC power is available)

Question 6

SYSTEM MALFUCNTIONS

When loss of NG indication occurs what other system should you monitor for indications of a greater problem?

Answer 6

Engine oil pressure, the NG tach generator is powered by the accessory drive at the engine oil pump.

Question 7

ELECTRICAL SYSTEM

What does the AC bus feed switch do?

Answer 7

Used to switch to auxiliary AC feeders if there is a malfunction in the normal feeder lines.

Used to select either GEN as the primary AC power source.

NORM position with both GEN’s on, number 1 is primary and 2 is in stand by. Opposite for AUX position.

Question 8

ELECTRICAL SYSTEM

What do the Transformer Rectifiers do?

Answer 8

Rectify 115/208 VAC into 28 VDC power for the DC system. When switched to the ON position they are connected to the DC bus, disconnected when moved to the OFF position.

Question 9

ELECTRICAL SYSTEM

What do the GENERATOR switches do?

Answer 9

Applies voltage to the field energizing the GEN and the output is then connected to the bus.

Question 10

ELECTRICAL SYSTEM

What does an illuminated AC Feeder Fail warning light mean?

Answer 10

Fault is detected in the selected feeder. Manually switch to the feeder not in use.

Question 11

ELECTRICAL SYSTEM

Describe the GENERATOR’s

Answer 11

20 KVA Generators
115/208 VAC
Three-Phase
380-420 Hz

Question 12

ELECTRICAL SYSTEM

Are both GENERATOR’s connected to the electrical system?

Answer 12

No, one unit is in

stand-by mode.

Question 13

ELECTRICAL SYSTEM

What is the purpose of the GCU’s?

Answer 13

1) Detect over voltage
2) Detect under voltage
3) Detect under frequency
4) Remove the faulty GEN from the bus when one of these conditions is detected.

Question 14

ELECTRICAL SYSTEM

What do the Differential Protection Units do?

Answer 14

Associated with each GEN

1) Detects current differential between the three phases.
2) Opens the field circuit to disable the generator when imbalance is detected.
3) Activate change over circuitry causing the appropriate GEN to accept the electrical load.

Question 15

SYSTEM MALFUNCTIONS

If you have a full electrical failure can you still shut down the engines?

Answer 15

Yes, you can attempt to use the 24volt AUX battery to move the ECA to STOP or START then trim the engine down to shutdown, or manually close the fuel shut off valves located in the stub wings.

Question 16

ELECTRICAL SYSTEM

What are the frequency control relays?

Answer 16

Located under the ECL’s on the center console.

1) Prevent generator operation before the ECL’s are placed in FLY.
2) If the NR falls below 83% when in FLY the under frequency cutout is delayed 10 seconds.
3) The relays also open the rotor brake circuits so the brake cannot be engaged with the ECL’s in FLY.

Question 17

FUEL SYSTEM

When will the FUEL BOOST FAIL lights illuminate?

Answer 17

When pressure output drops to 10 +/- 3 PSI on either of the two boost pumps located in the stub wings a pressure switch will illuminate the associated light.

Question 18

FUEL SYSTEM

When does the LOW FUEL PRESS warning light illuminate?

Answer 18

When inlet fuel pressure drops to 7.5 +/- 0.5 PSI a pressure switch located in the engine compartment will illuminate the associated light.

(This light will illuminate above 10,000’ if the boost pump is not operating)

Question 19

FUEL SYSTEM

Are the fuel boost pumps powered by DC or AC power?

Answer 19

175 gallon tanks use 28 VDC to power the boost pumps.

190 gallon tanks use 115 VAC three phase to power the pumps.

Both variations utilize 28 VDC control

Question 20

HYDRAULIC SYSTEM

Describe the components of the hydraulic system.

Answer 20

Two independent systems No. 1 and No. 2

Pressure compensated variable delivery pumps driven by the FWD XMSN

Hydraulic reservoir (side by side tanks, shared vent and overboard drain line)

Low fluid level switches

Two pressure switches (1 per system)

Four pressure filters (2 per system)

Two return filters (1 per system)

Two case drain filters (1 per system)

Two pressure transmitters and indicators

Stick boost manifolds

Lower stick boost actuators

Upper stick boost actuators

SAS extensible links

SAS control valves

Accumulators

Question 21

HYDRAULIC SYSTEM

SAS components and operation

Answer 21

The Stability Augmentation System (SAS) is an electro-hydraulic system that assists the pilot in maintaining helicopter stability about the pitch, roll, and yaw axes.

The SAS responds to changes in attitude as sensed by rate gyros.

Rate-of-motion signals created by rate gyros are processed then sent to the extensible links in the appropriate axis where they are converted into flight control movements.

These inputs are not felt in the controls as the extensible links are located after the lower stick boost actuators.

The systems primary reference is the rate of motion in the given axis and not the actual aircraft attitude.

The SAS has limited control authority (15% in pitch and roll, and 33% in yaw).

Components include:
Extensible links
LVDT’s
Amplifiers
Rate Gyros
Control Valves
SAS on/off selector 
Pedal Potentiometer
Side Slip Ports
Pitot static lines

Question 22

HYDRAULIC SYSTEM

Describe the flow of HYD fluid through the system

Answer 22

Reservoir
Quick disconnect
Pump Suction to Pump
(Case Drain HYD fluid routed to Case Drain filters then to return lines prior to return filters)
Pump Pressure to reservoir 
Pressure Relief Valve internal in Reservoir
Quick disconnect 
Pressure Switch (half gain relay)
Upper Pressure Filters
Upper Boost System
(T-off routes down to lower boost system)
Accumulators
Direct pressure gauges
Lower pressure filters
SAS control valves and SAS if activated
Snubbers
HYD Pressure transmitters 
Lower boost system manifolds to LDBA’s

Return lines routed to return filters then to reservoir.

Question 23

ENGINE

Describe the fuel control

Answer 23

Hydromechanical computer

Driven by the accessory drive

Uses the following signal inputs AM, P3, T2, NG, and NF.

Schedules the correct fuel/air flow during start

Governs Ng speed at idle

Maintains a constant Nf speed in FLY

Prevents compressor and power turbine overspeed, compressor stalls, over temperature, and rich/lean blowouts by sensing the onset of these conditions and computing a reaction by adjusting fuel pressure.

Uses raw fuel pressure as a hydraulic force to operate the stator vane actuator.