T6 Hydraulic System

The T6's hydraulic system uses fluids pressurized to what?

3000 +- 120 psi

T/F: the hydraulic system can be referred to as electro-hydromechanical

True

The primary hydraulic system operates which devices in normal flight ops?

Landing gear and main landing gear inboard doors

Flaps

Speed Brake

Nosewheel steering

What is the source for the hydraulic system's pressure?

The engine-driven pump

The hydraulic system can be used to power nosewheel steering, landing gear, main gear doors, flaps, and speed brake operations at what point?

When pressure exceeds 1800 psi

What drives the engine-driven pump?

The engine accessory gearbox

What does the power package reservoir do?

Provides pressurized fluid to the pump to keep the pump "charged" with fluid

How much pressure does the engine-driven pump produce?

3000 +- 120 pounds

What is the pressure within the power package reservoir?

50 psi

What pressure value does the power package pressure release valve operate at?

3250 to 3500 psi

What is the purpose of the power package slide valve?

To isolate the hydraulic pressure coming from the engine-driven pump to the rest of the hydraulic system when the emergency system is activated

Which handle activates the emergency system?

The landing gear emergency extension handle

What does the selector manifold do?

Allows hydraulic system, cockpit controls and aircraft devices operated by hydraulic system to work together. Contains 5 selector valves.

Describe how opening the landing gear normally works

Cockpit control to open landing gear sends electrical signal to selector manifold, which activates corresponding selector valve that sends pressure to the landing gear actuator

What are the normal operating limits of the hydraulic pressure?

2880 to 3120 psi (Green)

What are white values of hydraulic pressure?

Within safe operating limits

1800-2880 psi, 3120 - 3500 psi

What are amber values of hydraulic pressure?

Deserve special attention

1700 - 1800 psi, 3500 - 3600 psi

At what level does the amber HYDR FL LO light come on?

If the hydraulic fluid level in the reservoir drops below 1 quart

When is the emergency hydraulic system pressurized?

At the time of engine start up

What three circumstances call for emergency extension of landing gear

- Primary hydraulic system failure

- Engine failure

- Battery bus failure

During loss of engine power, the primary hydraulic system, or the battery bus, the emergency package will allow a one-time extension of

Flaps, landing gear, and main gear inboard doors

How does the emergency package get its pressure?

The emergency accumulator, which contains helium gas that was compressed by a metal bellows at start up

How many emergency extension selector valves does the emergency package have?

Two

The pressure release valve in the emergency package activates at what point

If pressure in the system reaches 3500 psi

The hydraulic fuse in the emergency system shuts off further flow to the emergency system at what point?

If a leak >0.25 gal/min occurs and a maximum of 20-30 cubic inches has passed

At what point does the amber EHYD PX LO annunciator come on

If emergency accumulator pressure drops below 2400 +- 150 psi

How are the landing gear doors operated?

Four are mechanically operated and two are hydraulically raised and lowered

How are the main gear inboard doors operated?

Hydraulically, share a single actuator that turns a torque tube and bellcrank

How are main gear outboard doors operated?

Mechanically, pulled along as strut is lowered and raised by individual actuators

What are the major components of the nose gear?

Spring strut, nose leg actuator, and nose gear door

Which way does nose gear retract?

Rearward

How long does a normal gear extension/retraction sequence take

6 seconds

What does it mean if the landing gear handle is illuminated red?

Main gear inboard doors are not closed or the PCL is approaching IDLE with gear handle UP

When are the gear position indicator lights red?

The gear or inboard gear doors (main gear only) are in transit

PCL is approaching IDLE and gear handle is UP, regardless of airspeed

When are gear position lights green?

When the gear is down and locked

Your airspeed should be ____ anytime the gear is extended

Below 150 KIAS

In what conditions does the gear aural warning take place?

Gear handle not DOWN, PCL below mid-range pos, airspeed below 120 KIAS, and flaps UP or TAKEOFF (common on spin entry)

All gear not indicating down and locked with flaps LDG (can't be silenced)

There is weight on the wheels with the gear handle not DOWN

Under what conditions can you not silence the gear warning?

Gear UP and flaps LDG

Gear handle UP with aircraft on the ground

What does the down lock solenoid do?

Prevents movement of landing gear selected handle when the aircraft is on the ground

Does the down lock override allow the landing gear to retract on the ground?

No, only the handle will be raised

Emergency hydraulic system specifically operates what?

Landing gear, main gear inboard doors, and flaps

When the power package slide valve closes, the hydraulic pump pressure is prevented form energizing any hydraulic components except for

The nosewheel steering actuator

What flap setting produces greatest lift with least drag?

Takeoff

How are the flaps controlled and operated?

Electrically controlled and hydraulically operated

What does the flaps system include?

Two selector valves

Emergency extension selector solenoid

Flap actuator

Flap torque tube

Associated microswitches

Make sure your airspeed is ____ before operating the flaps

Below 150 KIAS

Emergency flap operation is powered by what?

The hot battery bus

T/F: neither normal nor emergency flap operation and position indication is available when auxiliary battery is the only source of electrical power

True

What flap functions do you lose if the battery bus fails?

Normal flap operation and position indications

What does the speed brake do?

Increases drag in order to decelerate as well as increase descent rate without increasing airspeed

Where is the speed brake switch?

On the PCL

Once extended, the speed brake remains extended until any of what three tings take place?

- speed brake switch is moved forward

- Flaps are extended to landing or takeoff position

- Power control lever is moved to maximum

True or false: The speed brake can extend if the flaps are already extended

False

True or false: The speed brake can be controlled by the emergency hydraulic system

False, if you lose your primary hydraulics you'll lose the speed brake too

Describe the effects of the speed brake on pitch

Extended speed brake causes the aircraft to pitch up, becoming more pronounced as airspeed increases.

To counteract this pitch change the speed brake is connected to the elevator trim tab actuator and trim is input to help counteract the pitch change. This isn't perfect and the pilot will probably also have to input elevator trim

What are the 3 methods of steering the aircraft?

Differential braking

Nosewheel steering

Rudder inputs

When using Nosewheel steering how much do you control the amount of movement of the nosewheel

Up to 12 degrees in either direction

True or false: Nosewheel steering has greater turn radius when using the brakes

True

It is also more sensitive so don't lose control

Between rudder/differential braking and nosewheel steering, which allows you to make tighter turns?

Rudder/differential braking allows 80 degrees of turn, whereas NWS only allows 12

What are the components of the nosewheel steering and their functions?

Selector control valve - opening provides hydraulic pressure to actuator

Servo valve - lever mechanically connected to rudder pedals by push-pull cable. Moves back and forth using hydraulic pressure to turn the rotary actuator

Centering Valve- Returns wheel to centered position before it is extended or retracted

Describe the sequence of nosewheel steering function

Electrical solenoid from cockpit-> selector control valve -> actuator (servo valve, mechanical)

How many types of power does nosewheel steering use?

Electrical, hydraulic, and mechanical (3)

How is the wheel brake system operated?

Non-boosted, mechanically actuated system operating independent of the primary hydraulic system

Describe each brake unit

Disc brake with six pistons and two discs. There is only a brake unit for the left and right main wheels

Which pilot determines the amount of braking?

The one that applies the most force

How do you activate the parking brake?

Pull and turn the parking brake 90 degrees counter clockwise while holding toe brakes

What component sends pressure to the main wheel brakes

The master cylinder

True or False: The NWS system is separate from the selector manifold

True

True or False You will not have emergency flap capacity if the auxiliary battery is the only active power source

True

What systems are part of the selector manifold?

Landing gear system, landing gear main doors system, speed brake system, flaps (landing and takeoff) system

Which bus do normal gear and flap operation rely on?

The battery bus

What are components of the power package?

Reservoir, pressure release valve, slide valve

The primary and emergency hydraulic systems use ______ lines to the actuators

Separate

How many quarts of fluid are in the hydraulic system

5 quarts (1.25 gal)

What do you want to see on the green indicating rod in the reservoir level window?

FULL AC (accumulator charged) post flight or FULL AD (accumulator discharged) pre flight

On the gear handle what do red lights on the left and right side indicate?

The main inboard gear doors are open/in transit

How do you know if the nose gear doors or the outboard gear doors are closed?

You don't know, there are no indicators

What's normal sequence for emergency landing gear extension

Lower landing gear selector handle

Pull emergency landing gear extension handle

What are all of the flaps connected to?

The torque tube. The torque tube rotation is what puts down the flaps, which is how we can use only one actuator for the flaps

What's the benefit of flaps?

Shortens takeoff and landing roll by changing lift and drag of the aircraft

Describe the flap system sequence

As you select the flap switch on the PCL quadrant, the electrical system sends a signal to the electrical selector valve in the manifold to open or close.

Pressure released by the selector valve moves through the hydraulic line to the flap actuator.

The flap actuator drives the flap actuator strut which rotates the torque tube and flap segments to the selected setting (Figure 111-4).

As the torque tube rotates, a cam on the torque tube activates position sensing microswitches to drive the flap indicator in each cockpit.

What are some types of abnormal trim operations?

Runaway trim, inoperative trim, trim position indicator