-
12.13 (ATA 32) LANDING GEAR
12.13.1 Introduction
The Dash 8-Q400 landing gear is electrically controlled and
hydraulically operated. Hydraulicallyoperated nosewheel steering
gives directional control during taxiing, take-off and landing.
Eachmain wheel has hydraulically powered anti-skid brakes. There is
also an emergency/park brakesystem.
12.13.2 General
The tricycle gear is a retractable dual wheel installation. The
main gears retract aft into thenacelles and the nose gear retracts
forward into the nose section. Doors completely enclose thelanding
gear when it is retracted and partially enclose the gear when it is
down.
A Power Transfer Unit (PTU) supplies back-up hydraulic power to
the No. 2 hydraulic system. Ifthe landing gear cannot be extended
normally, there is an alternate landing gear extensionmethod.
Advisory lights show position of gear doors and downlocks. There
is also an alternate downlockverification system. An aural warning
sounds if the gear is not extended during certain
landingconfigurations.
A Proximity Sensor Electronics Unit (PSEU) monitors and controls
the operation of the landinggear components. The nosewheels are
steerable by a flight deck hand control and by the
rudderpedals.
The wheels may be equipped (customer option) with tire fill
pressure gauges for quick visualmeans of verifying tire pressure
during aircraft walk-around.
The main wheels are equipped with anti skid multiple disc
brakes. The brakes can be controlledby the brake pedals or the
EMERG BRAKE lever.
Dash8 - Q400 - Landing Gear
Page 1
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Figure 12.13-1 Landing Gear
Dash8 - Q400 - Landing Gear
Page 2
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12.13.3 Controls and Indications - Landing Gear and Brakes
Dash8 - Q400 - Landing Gear
Page 3
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Figure 12.13-2 Nose Gear Ground Lock Control Handle
PRESS BUTTONTO RELEASEPULL AND TURNTO GROUND LOCKNOSE GEAR
PR
ES
S B
UT
TO
NT
O R
EL
EA
SE
PU
LL
AN
D T
UR
NT
O G
RO
UN
D L
OC
KN
OS
E G
EA
R
1 2
1 2
ENGAGED(FULLY EXTENDED)
DISENGAGED(FULLY RETRACTED)
Dash8 - Q400 - Landing Gear
Page 4
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NOSE GEAR GROUND LOCK CONTROL HANDLE CALLOUTS
1. NOSE GEAR GND LOCK CONTROL HANDLE PUSHBUTTON (momentary
action)PUSH - releases nose gear control handle from fuselage-
control handle only springs out partly- control handle must be
pulled out fully from sprung out position to rotate
2. NOSE GEAR GND LOCK CONTROL HANDLE (two position, rotary
action)IN - (flush with fuselage)- nose gear unlocked
OUT - (not rotated)- nose gear downlock disengaged- handle must
be rotated to engage downlock
OUT - (rotated clockwise)- nose gear downlock engaged- control
handle must be pulled out fully from sprung out position to
rotate
Dash8 - Q400 - Landing Gear
Page 5
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Figure 12.13-3 Landing Gear Control Panel
LANDING GEAR
LOCKRELEASE
DN UP
TEST
MUTEHORN
N. DOORL. DOOR R. DOOR
RIGHTNOSELEFT
RIGHTNOSELEFT
1
2
4
5
3
6
Dash8 - Q400 - Landing Gear
Page 6
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LANDING GEAR CONTROL PANEL CALLOUTS
1. GEAR DOOR ADVISORY LIGHTS
(L. DOOR, N. DOOR, R. DOOR) segment (amber) - related hydraulic
gear door open- hydraulic gear doors stay open with no hydraulic
pressure
(L. DOOR, N. DOOR, R. DOOR) segment (blank) - related hydraulic
gear door closed- hydraulic gear doors close after normal gear
extension and retraction
2. LANDING GEAR SAFE ADVISORY LIGHTS
LEFT, NOSE, RIGHT segment (green) - related gear down and
locked- lights can be tested using CAUT / ADVSY LIGHTS toggle
switch- gear can also be checked with downlock verification
lights
LEFT, NOSE, RIGHT segment (blank)- related gear not down and
locked or in uplock position
3. LANDING GEAR UNSAFE ADVISORY LIGHTS
LEFT, NOSE, RIGHT segment (red) - related gear not locked up or
down
LEFT, NOSE, RIGHT segment (blank ) - related gear locked up or
down or no power to lights
4. SELECTOR LEVER LOCK BUTTON (momentary action)PUSH DOWN AND
HOLD - enables operation of landing gear handle
5. LANDING GEAR SELECTOR LEVER/LIGHT (two position)
UP - starts landing gear retraction sequence
DN - starts normal landing gear extension sequence- also select
DN for alternate gear extension- No Smoking signs come on
automatically if not on
HANDLE (amber)- landing gear operation does not agree with
position of landing gear selector handle
6. LANDING GEAR WARNING HORN MUTE/TEST SWITCH (two position,
momentary action)
TEST - gear warning tone sounds over flight deck speakers
HORN MUTE - gear warning tone is silenced under certain
configurations
Dash8 - Q400 - Landing Gear
Page 7
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Figure 12.13-4 Landing Gear Alternate Release Door and Inhibit
Switch
ARE CLEAR OF OBSTRUCTIONSBEFORE CLOSING ACCESS PANEL
ENSURE ALL WHEEL WELLS
TO CLOSE DUMP VALVE
CAUTION
LANDING GEAR
ALTERNATE RELEASE
OPEN DOOR FULLY
INHIBIT
NORMAL
DOOR OPENDOOR CLOSED
1
A
A
INHIBIT
NORMAL
3
2
Dash8 - Q400 - Landing Gear
Page 8
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LANDING GEAR ALTERNATE RELEASE DOOR CALLOUT
1. LANDING GEAR ALTERNATE RELEASE DOOR (two position)
CLOSED - landing gear extends and retracts normally
OPEN - connects hydraulic extension and retraction lines to
return
- gear cannot be extended using normal hydraulic power
- door must stay open for alternate gear extension
2. MAIN L/G RELEASE HANDLE (spring loaded to stowed
position)
PULL - make sure the handle is pulled fully (all the way
out)
- releases main gear hydraulic doors and main gear uplocks
- hydraulic gear doors will stay open
3. LANDING GEAR INHIBIT SWITCH (guarded, two position toggle
switch)
INHIBIT - disables normal landing gear extension operation using
the LANDIN GEAR lever
- LDG GEAR INOP caution light comes on (if not already on)
NORMAL - landing gear extends and retracts normally
Dash8 - Q400 - Landing Gear
Page 9
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Figure 12.13-5 Landing Gear Alternate Extension Door
LANDING GEAR ALTERNATE EXTENSION
OPEN OVERHEAD
DOOR FIRST
PULL RING TOOPEN PANEL
TO EXTEND AND LOCK MAIN LANDING GEAR,OPERATE HAND PUMP UNTIL
HANDLE IS STIFF.
NOSE L/G RELEASE
PULL FULLY UP
VISUAL CHECK FOR GEAR DOWN & LOCKED
TURN ON LIGHT SWITCHCHECK FOR LIGHTS
ACCESS DOOROPEN
ACCESS DOORCLOSED
5
4
1 FWD
A
A
B
C
B C
3
2
5
4
Dash8 - Q400 - Landing Gear
Page 10
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LANDING GEAR ALTERNATE EXTENSION DOOR CALLOUTS
1. LANDING GEAR ALTERNATE EXTENSION DOOR (two position)
CLOSED - landing gear extends and retracts normally
OPEN - alternate extension hydraulic fluid available for
alternate gear extension- door must stay open for alternate gear
extension
2. NOSE GEAR RELEASE HANDLE (spring loaded to stowed
position)
PULL - make sure the handle is pulled fully (all the way out)-
releases nose gear doors and nose gear uplocks- hydraulic gear
doors will stay open
3. MAIN GEAR ALTERNATE EXTENSION HAND PUMP (two position)- pumps
fluid from the emergency hydraulic reservoir to the auxiliary main
landing gear
actuators- handle located behind copilot's seat is inserted into
socket
4. LANDING GEAR DOWNLOCK VERIFICATION SWITCH (two position,
toggle switch)
AFT - activates alternate downlock verification system on each
gear- enables operation of gear verification lights
CENTER - alternate downlock verification system deactivated
5. LANDING GEAR DOWNLOCK VERIFICATION LIGHTS(NG, LH, RH)
(green)- related (Nose, Left main, Right main) landing gear is down
and locked using the alter-
nate downlock verification system- downlock verification toggle
switch must be set aft
(NG, LH, RH) - (blank)- related (Nose, Left main, Right main)
landing gear is not down and locked using the
alternate downlock verification system- downlock verification
toggle switch not set aft
Dash8 - Q400 - Landing Gear
Page 11
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Figure 12.13-6 Anti Skid Switch
C-FJOE
1
Dash8 - Q400 - Landing Gear
Page 12
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ANTI SKID SWITCH CALLOUT
1. ANTI SKID SWITCH (three position, momentary at TEST)
TEST - held in position and released to ON position- if airborne
with gear down and locked, INBD ANTISKID and OUTBD ANTISKID
caution
lights come on for 3 seconds then go off to show serviceable
anti skid system- if on the ground, INBD ANTISKID and OUTBD
ANTISKID caution lights come on for 6
seconds and then go off to show serviceable anti skid system- if
antiskid test fails, INBD ANTISKID or OUTBD ANTISKID caution lights
will stay on
ON - anti skid system activated- anti skid self test is made
when switch is first moved to position and if wheel speed is
not
more than 17 knots- INBD ANTISKID and OUTBD ANTISKID caution
lights go out
OFF - anti skid system deactivated- INBD ANTISKID and OUTBD
ANTISKID caution lights come on
Dash8 - Q400 - Landing Gear
Page 13
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Figure 12.13-7 Emergency/Parking Brake Lever Call-outs
PROP F
L
A
P
S
900
900
MAX1020
MIN850
START &FEATHER
FUELOFF
0
5
10
15
351 2
0
0
0
0
0
CONTROL
LOCK
RATING
P
ER
EMERG
BRAKE
ELEVATOR
TRIM
TO
RATING
CONTROL
LOCK
FLIGHTIDLE
MAXREV
PARK
ND
NU
OFF
ON
1 2
OFF
ON
WO
21
Dash8 - Q400 - Landing Gear
Page 14
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EMERGENCY/PARKING BRAKE LEVER CALLOUTS
1. EMERGENCY/PARKING BRAKE LEVER PUSHBUTTON (momentary
action)
PUSH - lets parking brake lever be released from PARK detent
2. EMERGENCY/PARKING BRAKE LEVER (two position)
FORWARD - emergency brake not engaged- pull back to actuate
emergency brake- pull back to engage detent for park brake- uses
No. 2 hydraulic pressure or accumulator pressure- a fully charged
accumulator is sufficient for approximately six applications
PARK (detent)- parking brake set if parking brake hydraulic
pressure is correct- PARKING BRAKE caution light comes on- minimum
500 psi parking brake pressure is required to ensure adequate park
brake
pressure before engine start- hand pump located in right main
wheel well can be used to increase park brake system
pressure- alternatively, if an AC power supply is available,
park brake system pressure can be
increased by running the SPU and the PTU
Dash8 - Q400 - Landing Gear
Page 15
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Figure 12.13-8 MFD Parking Brake Hydraulic Pressure
27.728.5
27.728.526.126.1
ELECTRICAL AC EXTPOWER
DC EXTPOWER
LOAD
1 1 51 1 51 1 5
. 06
. 06
. 06
1 1 51 1 51 1 5
. 06
. 06
. 06
AB
C
AB
C
+22+22+22
+1. 00- . 34- . 34
+1. 00
+1. 00 . 06
+1. 00 +1. 00
APU GEN
DC GENLOAD1 2
TRULOAD1 2
LOADBATT
°C
VOLTDC BUS
RL
MAIN
AUXSTBY
ESS
MAINSEC
AC GEN 1
AC GEN 2
VOLT LOAD
VOLT LOAD
HYD PRESS HYD QTYPK
STBYPSI x 1000 % x 100
BRK 1 2 3 1 2 34
2
FLAPDEG
1050
35
0 0
1
Dash8 - Q400 - Landing Gear
Page 16
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MFD CALLOUT PERTAINING TO LANDING GEAR
1. PK BRK INDICATOR - hydraulic pressure in the
emergency/parking brake system- normally the same as No 2 hydraulic
system pressure- shows brake accumulator pressure if No 2 hydraulic
system pressure is not available- minimum 500 psi is required if
Engine no.2 is started first
minimum 1000 psi is required if Engine no. 1 is started first-
pressure shown in psi- indicates from 0 to 4000 in 1000 psi
increments- in composite mode, hydraulic brake pressure shown
digitally
Dash8 - Q400 - Landing Gear
Page 17
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Figure 12.13-9 Nosewheel Steering Toggle Switch
PILOT’S SIDE PANEL CALLOUTS PERTAINING TO STEERING
1. NOSEWHEEL STEERING SWITCH (two position, toggle)
STEERING - nosewheel steering activated if aeroplane is on
ground and nosewheel is within
70° of center
- NOSE STEERING caution light will illuminate if a fault is
detected in the Nosewheel
Steering system.
OFF - nosewheel steering deactivated and is in the castor
mode
- nosewheel assumes shimmy damped or castor mode
- use when tow bar is connected to nose gear
- NOSE STEERING caution light comes on if there is hydraulic
pressure in the steering
system
CIR BKR LIGHT
W/S WIPERICE DETECT
PILOTSFLT PNL
PROP O'SPEEDGOVERNOR
OFF
LIGHT
ADCTEST 1
TEST 2 TEST 2
OFF BRT
STALL WARN TEST 1
OFF
STEERING
OFF
TEST
T/O WARNTEST
1
Dash8 - Q400 - Landing Gear
Page 18
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Figure 12.13-10 Nosewheel Steering Hand Control
NOSEWHEEL STEERING HAND CONTROL CALLOUTS
1. STEERING HAND CONTROL (rotatable control, self centering)-
rotate left or right to steer nosewheel up to 70° either side of
center- nosewheel STEERING toggle switch must be set to STEERING-
spring loaded to center position
2. STEERING RANGE LABEL (decal)- shows forward steering range or
for steering hand control- can be used for reference with mark on
steering hand control
GRD CREW FWD AFT
GPWS FLAP OVERRIDE
F W ARD
OR
STEERING RANGE
1 2
Dash8 - Q400 - Landing Gear
Page 19
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Figure 12.13-11 Brake Pedals
BRAKE PEDAL CALLOUTS
1. BRAKE PEDALS (differential action)
PUSH - top of pedals for brakes- left pedal for left brake-
right pedal for right brake
2. RUDDER PEDALS ADJUSTMENT HANDLE (rotary action)
ROTATE - moves both pedals forward or aft
Right side shown. Left side similar.
Dash8 - Q400 - Landing Gear
Page 20
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12.13.4 Landing Gear - Description
The main gear retracts aft and has multiple disc brakes with an
anti skid system (Figure 12.13-12). The nose gear retracts forward
and has steerable nosewheels (Figure 12.13-13). The land-ing gear
is operated by the No. 2 hydraulic system and is controlled by the
landing gear selectorlever on the LANDING GEAR control panel. There
is an alternate (emergency) means of exten-sion for the main and
nose landing gear. Advisory lights give extension/retraction and
fail/safeinformation.
Each main gear has a pair of forward and aft doors hinged to the
nacelle side structure (Figure12.13-14). When the gear is up, all
doors enclose the main wheels. With the main gear down, theforward
door on each main gear stays open. The nose gear has a pair of
forward and aft doors,which completely enclose the nose gear when
the gear is up (Figure 12.13-15). With the geardown, the forward
nose doors are closed, while the aft doors stay open.
The Proximity Sensor Electronic Unit (PSEU) controls the landing
gear, hydraulically operatedgear doors and related advisory lights.
It also monitors Weight-on-Wheels (WOW) sensors.WOW signals prevent
gear retraction while on the ground. Failure of a WOW system turns
on aWT ON WHEELS caution light. Redundancy is built in to ensure
landing gear operation if there isa PSEU failure. An audible
warning tone sounds, when the gear is not down and locked
withlanding flap or power settings.
Ground lock pins are supplied for the main gear and an integral
ground lock mechanism is con-trolled from outside the aeroplane for
locking the nose gear. The main gear lock-pins may bekept in the
forward compartment of the forward passenger door. With the gear
extended, the pinsare inserted into the main gear stabilizer brace
assemblies (Figure 12.13-16).
There are also landing gear door lock pins for the nose (Figure
12.13-17) and main (Figure12.13-18) hydraulic doors. This prevent
the hydraulic gear doors from closing.
Dash8 - Q400 - Landing Gear
Page 21
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Figure 12.13-12 Main Landing Gear Assembly
RE
MO
VE
BE
FO
RE
FL
IGH
T
LEGEND
1. Shock Strut. 2. Drag Strut. 3. Stabilizer Brace. 4. Main Gear
Pin. 5. Auxiliary Actuator. 6. Main Actuator. 7. Fairings. 8.
Proximity Sensors.
FWD
1
2
3
4
5
6
7
8
Dash8 - Q400 - Landing Gear
Page 22
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Figure 12.13-13 Nose Gear Landing Gear Assembly
11
12
FWD
1
2
3
4
5
6
7
NOTE
Left nosewheel removedfor clarity.
LEGEND
1. Downlock Actuator. 2. Upper Drag Strut. 3. Lower Drag Strut.
4. Taxi Light. 5. WOW Cover. 6. Tow Assembly. 7. Trailing Arm.
8. Retraction Actuator. 9. Steering Gearbox.10. Outer
Cylinder.11. Centering Actuator.12. Piston Assembly.
10
8
9
Dash8 - Q400 - Landing Gear
Page 23
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Figure 12.13-14 Main Landing Gear Extended Doors Open
NOTE
Left gear shown.Right gear similar.
FWD
Dash8 - Q400 - Landing Gear
Page 24
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Figure 12.13-15 Nose Landing Gear Extended and Retracted
FWD
FWD
CLOSED
OPEN
1
5
2 3
4
LEGEND
1. Forward Door.2. Forward Door Operating Mechanism.3. Shock
Strut Assembly.4. Aft Door.5. Aft Door Actuating Linkage.
Dash8 - Q400 - Landing Gear
Page 25
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Figure 12.13-16 Main Gear Ground Lock Pin
A
A
MAIN LANDINGGEAR
B
B
2
1
LEGEND
1. Lock Pin.2. Lock Pin Hole.
FWD
FWD
Dash8 - Q400 - Landing Gear
Page 26
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Figure 12.13-17 Nose Gear Hydraulic Door Lock Pin
TRONAIRRE
MO
VE
NOTE
View shown with debris guard removed.
Dash8 - Q400 - Landing Gear
Page 27
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Figure 12.13-18 Main Gear Hydraulic Door Lock Pin
TRONAIRRO
VEC
ONTA
COX
EM
NOTE
Right side shown.Left side similar.
Dash8 - Q400 - Landing Gear
Page 28
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12.13.4.1 Gear Operation
Landing gear operation is controlled and monitored from the
LANDING GEAR control panel,adjacent the Engine Display (ED). The
landing gear is selected UP or DN (down) by moving thelanding gear
selector lever. A LOCK RELEASE selector lever must be held down to
let the gearselector lever move in either direction.
An alternate downlock verification system confirms downlock
engagement if the primary down-lock indication is in doubt. Three
green downlock verification lights are located under the LAND-ING
GEAR ALTERNATE EXTENSION panel in the flight deck floor.
Gear Warning Tone
A landing gear warning tone sounds over the flight compartment
speakers if the HORN switch isheld at TEST. It also sounds if the
gear is not down and locked and:
1. • flaps > 8.5°• either engine torque < 50%• both PLA
< RATING detent
2. • both PLA < FLIGHT IDLE +12°• KIAS < 156
• RA < 1053 ft (321 m) if it is valid
3. • one PLA < FLIGHT IDLE + 12°• both PLA < RATING
detent• HORN switch not latched at MUTE• KIAS < 156 • RA <
1053 ft (321 m) if it is valid
NOTE: This is the only case in which the landing gear warning
tone may be muted. Enginefailure at airspeed less than 156
KIAS.
Dash8 - Q400 - Landing Gear
Page 29
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Figure 12.13-19 Landing Gear Retraction Schematic
CO
NT
RO
LS
EQ
UE
NC
ING
MA
IN/N
OS
EG
EA
R A
ND
DO
OR
PO
SIT
ION
S
WE
IGH
T-O
N-W
HE
ELS
LO
GIC
PR
OC
ES
SIN
G
PR
OX
IMIT
Y S
EN
SO
RE
LE
CT
RO
NIC
UN
IT
MA
IN/N
OS
EG
EA
R A
ND
DO
OR
CO
NT
RO
L V
ALV
ES
NO
SE
GE
AR
AS
SE
MB
LY
MA
IN G
EA
R A
SS
EM
BLY
AIR
CR
AF
TS
YS
TE
MS
GE
AR
PO
SIT
ION
AN
DLO
CK
ED
IN
DIC
AT
ION
LA
ND
ING
GE
AR
LO
CK
RE
LE
AS
E
TE
ST
HO
RN
N.
DO
OR
L.
DO
OR
R.
DO
OR
RIG
HT
NO
SE
LE
FT
RIG
HT
NO
SE
LE
FT D
NU
P MU
TE
Dash8 - Q400 - Landing Gear
Page 30
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Retraction Sequence
When the landing gear selector lever is selected to the UP
position, hydraulic pressure from No.2 system is applied to the
retract side of the system (Figure 12.13-19). This opens the nose
gearforward doors and retracts the nose gear, it also opens the
main gear aft doors and retracts themain gear. The aft nose gear
doors are mechanically linked and close with the retracting
nosegear. After nose gear retraction, the forward nose gear doors
close hydraulically. The forwardmain gear doors are mechanically
linked and close with the retracting main gear. After main
gearretraction, the aft main gear doors close hydraulically.
The advisory light sequence during retraction starts with the
LEFT, NOSE and RIGHT red unsafelights and the amber selector handle
light coming on. At the same time, the green LEFT, NOSEand RIGHT
lights go off to show the gear is not locked down. The amber door
advisory lightscome on to show the hydraulically operated gear
doors are open. When the landing gear isretracted and locked in the
up position, the amber selector handle light and red advisory
lights goout. Finally, the amber gear door advisory lights go out
to show all the hydraulic gear doors haveclosed. No advisory lights
should be on if the gear is up correctly. The main and nose gear
areheld in the up position mechanically with uplocks, and hydraulic
pressure is removed from thesystem.
Extension Sequence
When the landing gear selector lever is moved to the DN
position, hydraulic pressure is appliedto the extend side of the
system through the solenoid selector valve (Figure 12.13-19). The
mainand nose hydraulic doors open, and the main and nose gear
extend. The hydraulic forward noseand aft main gear doors close
after the gear is down and locked.
The advisory light sequence during extension starts with the
LEFT, NOSE, and RIGHT redunsafe lights and the amber gear selector
handle light coming on. The amber door advisorylights then come on
to show the hydraulically operated gear doors are open. When the
landinggear is fully extended and locked in the down position, the
red unsafe lights, and the selectorhandle light goes out. Then the
green LEFT, NOSE, and RIGHT advisory lights come on. Finally,the
gear door advisory lights go out when the hydraulically operated
doors are closed. Continu-ous hydraulic pressure acts on the gear
when down and locked, however primary downlock is bythe overcenter
locks.
If a landing gear hydraulic sequencing valve fails, or the PSEU
is unable to control it, the LDGGEAR INOP caution light comes
on.
NOTE: With the LDG GEAR INOP caution light on, ALTERNATE GEAR
EXTENSION proce-dure is to be followed.
Dash8 - Q400 - Landing Gear
Page 31
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Figure 12.13-20 Alternate Landing Gear Extension Schematic
LA
ND
ING
GE
AR
AL
TE
RN
AT
E R
EL
EA
SE
DO
OR
(O
PE
N)
MA
IN D
OO
RU
PLO
CK
RE
LE
AS
E
LA
ND
ING
GE
AR
AL
TE
RN
AT
E E
XT
EN
SIO
ND
OO
R (
OP
EN
)
HA
ND
PU
MP
NO
SE
GE
AR
UP
LO
CK
RE
LE
AS
E
NO
SE
DO
OR
UP
LO
CK
RE
LE
AS
E
HY
DR
AU
LIC
PR
ES
SU
RE
CA
BLE
CIR
CU
IT/
LE
GE
ND
TO
MA
IN G
EA
RA
UX
ILIA
RY
AC
TU
AT
OR
S
MA
IN G
EA
RU
PLO
CK
RE
LE
AS
E
CO
NT
RO
L L
INK
AG
E
MA
IN L
/G R
EL
EA
SE
PU
LL F
ULLY
DO
WN
BA
A
B
EN
SU
RE
ALL W
HE
EL W
ELLS
AR
E C
LE
AR
OF
OB
ST
RU
CT
ION
SB
EF
OR
E C
LO
SIN
G A
CC
ES
S P
AN
EL
TO
CLO
SE
DU
MP
VA
LV
E.
CA
UT
ION
Dash8 - Q400 - Landing Gear
Page 32
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12.13.5 Alternate Gear Extension
The alternate extension system (Figure 12.13-20) gives a means
of extending the landing gearwhen:
• LDG GEAR INOP caution light is on• Landing gear indication
fails• Loss of No. 2 hydraulic system pressure
The landing gear extension INHIBIT switch is installed in the
flight deck ceiling, adjacent to themain LANDING GEAR ALTERNATE
RELEASE door. Setting the switch to INHIBIT isolates allhydraulic
pressure from the landing gear system.
When the main LANDING GEAR ALTERNATE RELEASE door on the flight
deck ceiling isopened it mechanically opens a bypass valve in the
normal hydraulic extension system, andgives access to the MAIN L/G
RELEASE handle. Pulling the handle releases the main landinggear
doors and uplocks. The main gear will free fall but may not fully
extend. The LANDINGGEAR ALTERNATE EXTENSION door, on the flight
deck floor, must then be fully opened givingaccess to the alternate
extension handpump and the NOSE L/G RELEASE handle. Opening thedoor
mechanically operates the MLG alternate selector valve. If the MLG
does not reach thedown and locked position, the extension pump
handle, located behind the copilot, is inserted intothe pump handle
socket and operated to complete main gear extension and subsequent
down-lock (Figure 12.13-21). Both the LANDING GEAR ALTERNATE
EXTENSION door and the MAINLANDING GEAR ALTERNATE RELEASE door must
be left fully open after alternate landinggear extension.
When the NOSE L/G RELEASE handle is pulled, the nose gear uplock
and doors are releasedand the nose gear free falls to a down and
locked position, assisted by the airflow to a down andlocked
position.
Dash8 - Q400 - Landing Gear
Page 33
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Figure 12.13-21 Main Landing Gear Alternate Extension System
SU
CT
ION
LIN
E
LE
GE
ND
A
MLG
ST
AB
ILIZ
ER
BR
AC
E A
SS
EM
BLY
LO
WE
R R
IGH
T N
OS
EC
OM
PA
RT
ME
NT
LA
ND
ING
GE
AR
AL
TE
RN
AT
E E
XT
EN
SIO
ND
OO
R (
OP
EN
)A
AU
XIL
IAR
YA
CT
UA
TO
RFW
D
ALT
ER
NA
TE
LA
ND
ING
GE
AR
SE
LE
CT
OR
VA
LV
E(C
LO
SE
D P
OS
ITIO
N)
PR
ES
SU
RE
LIN
E
ALT
ER
NA
TE
LA
ND
ING
GE
AR
HY
DR
AU
LIC
RE
SE
RV
OIR
1.2
5 U
.S. Q
UA
RT
S(1
.2 L
ITR
ES
)H
AN
D P
UM
P
NO
TE
Left G
ear
show
n.
Rig
ht G
ear
sim
ilar.
Dash8 - Q400 - Landing Gear
Page 34
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Figure 12.13-22 Nosewheel Steering Schematic
NOSESTEERING
fs number
LOW SPEED TAXI MODE70° LEFT AND RIGHT
(STEERING CONTROL HANDLE)
HIGH-SPEED TAXI MODE8° LEFT AND RIGHT(RUDDER PEDALS)
UNPOWERED(CASTER) MODE
120° LEFT AND RIGHT
8° 8°
70°70°
120° 120°
OFF
STEERING
PSEU
NOSEWHEELSTEERING
CONTROL UNIT(SCU)
STEERINGMOTOR
ON-GROUNDSIGNAL FROMNOSE GEARWEIGHT ON
WHEELS SWITCHESCAUTION LIGHT
STEERINGACTUATOR
NOSEWHEELSTEERING SWITCH
RUDDERPEDALS
STEERINGCONTROLHANDLE
LEGEND
No. 2 Hydraulic Pressure.Steering Pressure.ReturnElectrical
Dash8 - Q400 - Landing Gear
Page 35
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12.13.6 Nosewheel Steering System
Directional control on the ground is by the nosewheel steering
(NWS) system (Figure 12.13-22),powered by the No. 2 hydraulic
system. Steering control is by either the Steering Hand Control
orthe rudder pedals. The Steering Hand Control turns the nosewheel
up to 70° either side of centerfor low speed taxi. Steering with
the rudder pedals turns the nosewheel up to 8° either side ofcenter
for high-speed taxi, take-off and landing roll. After take-off, the
nosewheel automaticallycenters before retraction.
The hand control, located on the Pilot’s Side console, is
self-centering and operates when theSTEERING switch is set to the
STEERING position. The nosewheel must be within 70° of centerfor
the steering to work. An index mark on the hand control shows the
relative position of thenosewheel against a fixed STEERING RANGE
decal. With the STEERING switch set to STEER-ING, power is directed
to the nosewheel Steering Control Unit (SCU), if the nose gear is
downand locked with weight-on-wheels.
The nosewheel will revert to a passive shimmy dampened castoring
mode if:
• The nosewheel angle is greater than 70°• The SCU detects a
failure• STEERING switch is set to OFF
In the passive mode, the nosewheel will castor up to 120° either
side of center. Differential brak-ing and/or power may be used for
directional control in the passive mode.
The NOSE STEERING caution light comes on if:
• SCU detects a failure with STEERING switch set to STEERING•
hydraulic pressure detected in steering system with STEERING switch
set to OFF
The NOSE STEERING caution light does not come on if electrical
power is removed from theSCU.
When taxiing in reverse the STEERING switch must be selected on.
However, no steering is per-mitted with either the tiller or the
rudder pedals.
NOTE: Nosewheel steering using the hand control is limited to
forward taxiing only, with theSTEERING switch set to the STEERING
position.
CAUTION: Do not set the STEERING switch to STEERING if tow bar
is connected to nose gear.
Dash8 - Q400 - Landing Gear
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Figure 12.13-23 Normal Brake System
OU
TB
D
AN
TIS
KID
INB
D
AN
TIS
KID
LE
GE
ND
Ele
ctrica
lM
ech
anic
al
Norm
al B
raki
ng P
ress
ure
(N
o.1
Sys
tem
)E
merg
ency
Bra
king M
ete
red P
ress
ure
Hyd
raulic
Retu
rn P
ress
ure
QU
AN
TIT
Y L
IMIT
ING
VA
LV
ES
(4
)
CO
PIL
OT
RU
DD
ER
PE
DA
LS
Fro
m H
ydra
ulic
Sys
tem
NO
. 2
WH
EE
LS
PE
ED
SE
NS
OR
(4
)T
RA
NS
DU
CE
RS
SH
UT
TL
EV
AL
VE
S (
4)
RIG
HT
MA
IN
BR
AK
EC
ON
TR
OL
VA
LV
E
PS
EU
CA
UT
ION
&W
AR
NIN
G L
IGH
TS
AN
TI
SK
IDT
ES
T
ON
OF
F
To
Hyd
rau
lic R
etu
rn
Fro
m H
ydra
ulic
Sys
tem
NO
. 2
PIL
OT
RU
DD
ER
PE
DA
LS
DU
AL
AN
TIS
KID
VA
LV
ES
BR
AK
E U
NIT
(4
)
LE
FT
MA
IN
AN
TIS
KID
CO
NT
RO
LU
NIT
(A
SC
U)
OU
TB
D
AN
TIS
KID
INB
D
AN
TIS
KID
Dash8 - Q400 - Landing Gear
Page 37
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12.13.7 Brake System
12.13.7.1 Normal Braking
Each main wheel is equipped with a multiple disc brake unit
powered by the No. 1 hydraulic sys-tem (Figure 12.13-23). An Anti
Skid Control Unit (ASCU) modulates the application of brakepressure
to each brake unit.
Brake pressure is applied by pushing the pilot’s or copilot’s
brake pedals (Figure 12.13-25).
The anti skid control unit:
• Monitors wheel speed• Modulates the brake pressure applied to
each brake unit to prevent wheel lock-up• Gives maximum braking at
all levels of runway friction.
The ANTI SKID switch on the copilot's glareshield panel operates
the anti skid system when setto the ON position and the wheel speed
is more than 10 knots. A start up self test of the anti skidcontrol
circuits is made when the switch is moved to the ON, or momentary
TEST. The start upself test is prevented with wheel speed more than
17 knots. If the ANTI SKID switch is held atTEST, the aeroplane on
the ground, the INBD ANTISKID and the OUTBD ANTISKID cautionlights
come on for six seconds and then go out. If the ANTI SKID switch is
held at TEST in the air,with the landing gear extended and locked,
will turn on the related caution lights for three sec-onds. If the
ASCU senses a fault in the system, it turns on the related caution
light.
The PSEU supplies weight-on-wheels and gear up and locked
signals to the ASCU, to makesure that the brakes are off until the
aeroplane has touched down and the wheels are spinning.
Inconditions of low runway friction, the main gear wheels may not
spin up before the aeroplane'sweight is fully on the wheels. In
this case, the ASCU gives a 5 second delay before brake pres-sure
is applied. This delay is immediately cancelled when wheel speed is
more than 35 knots.
NOTE: Brake cooling times must be observed between a landing, or
a low energy rejectedtake-off and a subsequent take-off, to make
sure that sufficient brake energy is avail-able to bring the
aeroplane to a complete stop if the subsequent take-off is
rejected.
Dash8 - Q400 - Landing Gear
Page 38
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Figure 12.13-24 Brake Pedals
1
2
3
45
6
7
8
9
10
FWD
LEGEND
1. Copilot Brake Pedals. 2. Tie Rods. 3. Brake Control Levers.
4. Brake Interconnect Cables. 5. Lever Springs. 6. Cables to Brake
Control Valve. 7. Push Rods. 8. Spring Rods. 9. Tie Rods.10. Pilot
Brake Pedals.
Dash8 - Q400 - Landing Gear
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12.13.8 Emergency Brake System
The emergency/parking brake system (Figure 12.13-25) lets the
brakes be applied if the normalbrake system fails, or for setting
the parking brake. An EMERG BRAKE lever on the Engine Con-trol
quadrant operates the system. The emergency/parking brake system is
powered by No. 2hydraulic system, or by parking brake accumulator
pressure. Hydraulic pressure to the emer-gency/parking brake system
is shown on the PK BRK indicator on the PERMANENT SYSTEMSAREA (PSA)
of the MFD.
The EMERG BRAKE lever operates against a spring to produce a
resistance proportional to thebrake pressure applied as the lever
is pulled back. There is no differential braking and no antiskid
protection when using the EMERG BRAKE lever. If the
emergency/parking brake system isused with No. 2 hydraulic system
inoperative, the accumulator supplies brake pressure. A
fullycharged accumulator is sufficient for approximately six
applications.
The parking brake is engaged by pulling the EMERG BRAKE lever
all the way back to the detentPARK position. This turns on the
PARKING BRAKE caution light on the Caution and Warningpanel. The
button on the side of the handle must be pushed to release the
lever from the PARKdetent.
NOTE: Care should be taken when releasing the lever as
considerable spring tension willforce the lever forward.
NOTE: With the parking brake set, application of engine power
will cause the take-off warn-ing horn to sound.
A hand pump located in the right main wheel well can be used to
increase the park brake systempressure. Minimum pressure required
before engine start is 500 psi.
Alternatively, if an AC power supply is available, park brake
system pressure can be increasedby running the SPU and the PTU.
Dash8 - Q400 - Landing Gear
Page 40
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Figure 12.13-25 Emergency Brake System
FLAPDEG
35
1050 HYD PRESS HYD QTY
PKSTBY
PSI x 1000 % x 100
BRK 1 2 3 1 2 34
2
0
High PressureNitrogen
Parking Brake / Emergency Pressure
No. 2 HydraulicSystem Suction
PARKINGBRAKE
#2 MFD
From No. 2System Reservoir
From No. 2Hydraulic System
ACCUMULATORGAUGE
HAND PUMP
CAUTION LIGHT
MAIN WHEELBRAKE UNITS
From No. 1Hydraulic System
SHUTTLEVALVES
To the otherMain Gear
NOTEShown with ParkingBrake applied.
EMERGENCY/PARKINGBRAKE CONTROL VALVE
ACCUMULATOR
(Right Nacelle)
No. 2 Hydraulic Systemor
Accumulator Pressure
HandPump
Pressure
From No. 1Hydraulic System
Hydraulic Return
Dash8 - Q400 - Landing Gear
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12.13.9 Tires
12.13.9.1 Tire Fill Valve Gauges
Tire pressure gauges are offered as a customer option, to
operators who want a visual means ofchecking tire pressures during
a walk-around. The dial gauge is integral with the inflation
valveand mounted in the same location on the wheel without any
additional installation requirements.
A gauge is mounted on each MLG and NLG wheel and has a dial face
with a shaded portion ofits face denoting the proper inflation
pressure plus a 5% tolerance.
The gauge itself uses a Bourdon tube with the closed end
attached to a pointer and the other endvented to the tire interior
through the inflation valve bore.
12.13.9.2 Tire Inspection (Removal criteria)
General
Dunlop tires fitted to Q400 has two layers of nylon fabric
placed between the casing plies andthe base of the tread grooves.
This Inter Tread Fabric (also called reinforcement fabrics)
formspart of the wearable tread pattern and will be exposed during
the life of the tread. (Ref Figure12.35.26.)
• Examine the tires for signs of wear, damage and other
deterioration.
1) Wear
• Remove the tire when tread has worn to the base of any grove
or if any casing plies areexposed.
Note: Tires found to be exhibiting the above removal wear
standard, which at the time is atan out-station, the replacement
can be postponed to first night stop or to the basewhichever comes
first.
2) Cuts or cracking
a) Tread
• Remove tire if any cut or crack penetrate any casing
plies.
• Remove tire if cracking undercuts ribs.
• Remove tire if any cut extend more than 35 mm or 50% of any
tread rib and has a treaddepth of 50% or more than existing tread
depth.
b) Sidewall
• Remove tire if cracking is found in the sidewall.
Note: If only the first casing ply is damaged, the replacement
of the tire can be postponedto the first night stop or to base
whichever comes first.
3) Bulges or Air Bubbles
• Remove tires if bulges or air bubbles are found in the tread
or in the sidewall.
Note: Removal of tires exhibiting above removal standard may be
postponed to the firstnight stop or to base whichever comes
first.
Dash8 - Q400 - Landing Gear
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Figure 12.13-26 Tire
Dash8 - Q400 - Landing Gear
Page 43