Hydraulics Flashcards
HYD_001
Understand the functions of the AUX hydraulic pump switch:
- The auxiliary pump, in the right system, provides an additional source of hydraulic pressure.
- Pump operation is controlled by the auxiliary pump (AUX) switch located on the FO’s instrument panel.
- ON – Turns on electrical hydraulic auxiliary pump.
- OFF – Turns off electrical hydraulic auxiliary pump.
- OVRD – (Momentary – must be held in OVRD) – Bypasses thermal protective circuit. Activates pump.
- The auxiliary pump is protected by a thermal switch that automatically shuts the pump off if the normal operating temperature range is exceeded.
HYD_002
Understand the functions of the hydraulic transfer pump switch:
- The HYD PUMP TRANS Switch open/closes shutoff valve on each side of transfer pump.
- The transfer pump mechanically connects left and right hydraulic systems and enables hydraulic pressure to be transferred from the highest to the lowest side (the high pressure side operates as a motor and the low pressure side acts as a pump).
HYD_003
Meaning of an illuminated HYD QTY LOW light before and after engine start:
MD-88:
- The amber HYD QTY low lights on the system display panel illuminate when the left quantity is less than 8 quarts or the right quantity is less than 9 quarts.
- After engine start, if either system’s quantity is below 4 quarts, the applicable low light illuminates.
MD-90:
- The amber HYD QTY low lights on the system display panel illuminate when the left quantity is less than 9 quarts or the right quantity is less than 10 quarts.
- After engine start, if either system’s quantity is below 6 quarts, the applicable low light illuminates.
HYD_004
Recall that the engine driven hydraulic pumps operate during electrical failure:
Engine driven HYD pumps operate during electrical failure regardless of switch position.
HYD_005
Recall the minimum hydraulic quantity for dispatch:
- MD-88: Left minimum – 8 qts, Right minimum – 9 qts
- MD-90: Left minimum – 9 qts, Right minimum – 10 qts
HYD_006
Recall the number of independent hydraulic systems and how they are designated:
The airplane has two independent hyd systems (left and right) utilizing fire-resistant hydraulic fluid.
(88, 90) Minimum hyd pressure necessary to set the parking brake:
• Minimum of 1400 psi (88) / 1700 psi (90) on BRAKE PRESS gauges is required prior to setting the parking brake to ensure adequate brake holding power.
(88, 90) Meaning of amber ABS light:
- Landing gear handle is down
- AUTO BRAKE selector is moved out of the OFF position
- AUTO BRAKE ARM/DISARM switch is in DISARM.
(88, 90) Conditions for availability of antiskid braking:
Antiskid system is elec. controlled and is operational when:
- Switch in ARM position
- Gear handle down or alt gear handle pulled
- Parking brakes released
- Wheel speed greater than 10 knots
Note: Anti-skid braking is not available if the left / right DC busses are unpowered.
(All) Recall auto brakes are available in normal brake system only: When should autobrakes not be used? When is ABS unavailable?
- The anti-skid system must be armed and operational for ABS operation.
- With left and/or right hydraulic system failure, do not use Autobrakes.
- ABS is unavailable with flaps < 26° for landing or if the accumulators are the only source of hydraulics.
(ALL) Conditions required for autobrake RTO system operation:
- ABS takeoff mode is activated during rejected take off upon spoiler handle extension.
Note: If spoiler handle fails to deploy automatically, manual spoiler handle deployment will activate ABS.
- If a rejected takeoff is initiated < 70 kts (88) / 90 kts (90), ABS reverts to landing mode operation and MIN braking is provided.
- At speeds > 70 kts (88) / 90 kts (90), max dual-system auto braking is applied immediately without any time delay.
Note: Full right and left brake system pressure is applied to the brakes and maximum deceleration is limited only by anti-skid operation.
(ALL) Conditions required for ABS operation during landing:
- ABS landing mode is activated when
- (1) spoiler handle is deployed either automatically or manually,
- (2) throttles retarded and
- (3) brake pedals released.
- Auto braking is delayed after spoiler deployment for ~ 1” in MAX position and ~ 3” (88) / 1” (90) in MIN or MED positions. ABS landing mode is inhibited if throttles are not retarded towards idle.
Note: - With MED selected, brake system pressure is modulated to brakes by land manifold to maintain a fixed level of deceleration. - With MAX selected, full right brake system pressure is applied to brakes; maximum deceleration is limited only by anti-skid operation
(88, 90) Brake pedal deflection that will disengage automatic braking (autobrakes):
MD-88
- Autobrakes are disarmed at any speed by depressing brake pedals beyond 25% travel.
MD-90
- Below 90 knots, 25% pedal deflection is required to disengage autobrakes.
- ,Above 90 knots, 90% pedal deflection is required to disengage autobrakes.
(88) Maximum brake temperatures for takeoff and setting the parking brake:
MD-88:
- Max brake temp for setting parking brake: 300°C
- Prior to takeoff, verify brake temp < 205°C and OVHT light extinguished.
(90) Maximum brake temperatures for takeoff and setting the parking brake:
MD-90:
- Max brake temp for setting parking brakes is 500°C.
- Prior to takeoff, verify OVHT light extinguished and BRAKE TEMP gauge < 250°C for airport elevations up to 2,200’ MSL.
- Corrections to takeoff brake temperature limits: - When OAT exceeds 32°C, subtract 5°C for each 1°C above 32°C. - For each 1 knot of tailwind, subtract 15°C. •
- For takeoff from higher airport elevations or higher brake temperatures refer to guidance in VOL.1 NP and ODM.
