Hydraulics Flashcards
(88, 90) Functions of AUX hydraulic pump switch:
• Aux pump in the right system, provides addt’l source of hyd pressure.
• Operation controlled by auxiliary pump (AUX) switch located on FO’s instrument panel.
- ON – Turns on electrical hyd auxiliary pump.
- OFF – Turns off electrical hyd auxiliary pump.
- OVRD – (Momentary – must be held in OVRD) –
Bypasses thermal protective circuit & activates pump.
• Auxiliary pump is protected by thermal switch that automatically shuts pump off if normal operating temp range is exceeded.
(88, 90) Functions of the hydraulic transfer pump, positions of switch:
On / off switch
- HYD PUMP TRANS Switch open/closes shutoff valve on each side of transfer pump.
- Transfer pump mechanically connects left and right hydraulic systems and enables hydraulic pressure to be transferred from higher to lower side (higher pressure side operates as a motor and low pressure side acts as a pump).
(88, 90) Meaning of an illuminated HYD QTY LOW light before and after engine start:
Amber HYD QTY LOW lts on system display panel illuminate when:
MD-88:
• Left quantity < 8 qts or right quantity < 9 qts.
• After engine start, if either sys. quantity < 4 qts
MD-90:
• Left quantity < 9 qts or the right quantity < 10 qts.
• After engine start, if either sys. quantity < 6 qts
(88, 90) Will engine driven hydraulic pumps operate during electrical failure?
• Engine driven HYD pumps operate during electrical failure regardless of switch position.
(88, 90) 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
(ALL) How many independent hydraulic systems are on the MD-88/90? How are they designated?
• Airplane has 2 independent hyd systems (left and right) utilizing fire-resistant hyd 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 takeoff 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, 90) Maximum brake temperatures for takeoff and setting the parking brake: (MD-88)
MD-88:
• Max brake temp for setting parking brake: 300°C
• Prior to takeoff, verify brake temp < 205°C and OVHT light extinguished.
(88, 90) Maximum brake temperatures for takeoff and setting the parking brake: (MD-90)
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.
(88, 90) During what aircraft condition will GEAR HORN OFF button not silence gear warning?
Pushing GEAR HORN OFF button will silence landing gear warning horn and vocal warning under all conditions of descent and approach except:
- Gear not down and flaps > ~ 26°
- Gear must then be down & locked to silence warning sys.
(88, 90) Secondary indicator for nose gear extension:
• Indicator on forward pedestal appears when nose gear is fully extended and nose gear links are locked over-center.
(88, 90) Where are brake temperatures displayed?
- FO’s Instrument Panel.
* BRAKE TEMP gauge indicates hottest or selected brake temp depending on the position of the Brake Temp Selector.
(88, 90) When will Brake OVHT light illuminate?
Brake temp > 305°C / 540°C (88/90).
WARNING: If brake temp ≥ 305°C for ~5’ wheel fuse plugs may activate, deflating tires. Keep all personnel clear of main landing gear area.
