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Contents:
Foreword: ... 2
APU ... 8
Auto Slat System... 9
Engine Electronic Control (EEC) ... 10
When things go wrong and beyond basic systems knowledge ... 11
Engine fire detection ... 13
Feel Differential ... 14
Fuel Scavenge Jet Pump ... 15
Fuel valves ... 16
AC Generator ... 17
Isolation valve ... 19
Manual gear extension. ... 20
Mechanical pressure relief valves. ... 21
Nitrogen Generating System ... 22
Outflow valve. ... 23
Flight Control “Breakaway” Devices ... 24
Pack & pack control ... 25
Recirculation fans ... 26
Hydraulic Reservoirs ... 27
The APU Starter/Generator. ... 28
Landing Gear Transfer Valve ... 29
PTU ... 30
Wing Thermal Anti Ice (WTAI) ... 31
B737 Yaw damping ... 32
Zone temperature control ... 33
Lavatory “fire protection”. ... 34
Center tank boost pumps ... 35
Antiskid ... 36
Leading Edge Flaps ... 37
Thrust Reverser ... 39
Tail Skid ... 41
Vortex generators... 42
Window heating ... 43
Wing& Body Overheat ... 44
Horizontal Stabilizer Trim. ... 45
Display Electronic Units. ... 46
Proximity Switch Electronic Unit ... 47
Nose wheel steering lockout ... 48
Weather radar ... 49
Dissolved air ... 51
Frangible fittings ... 52
Rudder(vertical stabilizer) load reduction ... 53
Rejected Takeoff – speed brakes relation. ... 54
Electrical Bus (bar) ... 55
Crew oxygen system ... 56
Main system hydraulic pumps, (corrected) ... 57
Cockpit Voice Recorder System ... 58
Pressure control ... 59
Runway Awareness and Advisory System (RAAS) ... 61
Electro Motor Driven Pumps Overheat ... 63
Cockpit panel “+” symbols. ... 64
Overhead (P5) panel drains. ... 65
Closed crossfeed valve on takeoff and landings? ... 66
Amber AUTO BRAKE DISARM Light ... 67
B737 Fire protection ... 68
Start switch functions. ... 69
Fuel nozzle “coking”. ... 71
Dual bleed light ... 72
Air Cycle Machine operation ... 73
Airstair ... 74
Equipment Cooling ... 75
Overboard Exhaust Valve ... 76
Thermal electrical protections. ... 77
Fuel temperature indication. ... 78
Integrated Drive Generator (IDG)... 79
Electrical Load Shedding ... 81
Common Display System (CDS) malfunctions. ... 82
Cargo Compartments air. ... 83
NiCad Battery operation. ... 84
Climb Thrust Reduction ... 86
The “white bug”. ... 87
Standby Hydraulic System operation. ... 88
Transformer Rectifier Units. (TRU) ... 90
RAM AIR DUCT doors. ... 91
Standby Power. ... 92
Fueling panel ... 93
Brake accumulator ... 95
Control column shaker ... 96
Wheel thermal fuse plugs. ... 98
Battery busses ... 99
Electrical schematic ... 100
Fuel schematic ... 101
Hydraulic schematic ... 102
Bleed schematic ... 103
Air condition schematic ... 104
Engine oil & fuel schematic ... 105
Flight Mode Annunciations (FMA) ... 106
Power Sources (NG) ... 108
APU
The APU
pressuriz
transfer
starter o
until 32.
Electron
The APU
until 41.
takes th
mounted
perform
when th
on suctio
fuel pum
The ECU
illuminat
power, A
and a FA
malfunct
occurred
APU com
outside a
When th
minute b
OFF line
of the no
Delay sw
door to
collapse
is activat
U is a const
zed air. The
bus 1 (115V
operation rev
.000 ft. and
ic Control U
U can be use
.000 ft. That
he biggest p
d on a comm
ance of the
e demand is
on feed the
mp to pressu
U protects th
tes. The latt
APU fire, ove
AULT light ill
tions. A blue
d, the APU is
mpartment
air into the c
he APU is st
before the A
. By doing so
ozzles. (resid
witching the
close. The
. The 1 minu
ted or when
ant speed (
e starter/gen
VAC) where e
verses to a 9
66 KVA unt
nit (ECU) tha
ed for air and
t is also the
erformance
mon shaft wi
APU. That
s large (high
APU draws f
re feed whic
e APU and s
ter represen
ertemp (dur
uminates wh
e MAINT lig
s still allowed
and oil coo
compartmen
topped by p
APU actually
o it reliefs th
dual fuel form
Battery to O
door closes
ute is by‐pass
the Battery
± 49.000 RP
nerator is po
either source
90 KVA gene
til 41.000 ft
at needs the
d AC power
maximum st
from the A
ith the comb
is why there
EGT), air use
fuel from ta
ch extends th
shuts down w
nts more tha
ing start), hi
hen the star
ght illuminat
d to operate.
ling is accom
nt from an in
placing the s
stops. The c
e APU from
ms carbon on
OFF to 2 min
when the A
sed when th
Switch is sel
PM) gas tur
owered from
e is converte
erator, indica
t.) Starter se
battery swit
until 10.000
tarting altitu
APU as it ta
bustion comp
e is a restric
e is squeezed
nk #1 and w
he lifetime of
with a low o
an just the
igh oil temp
t is aborted
es when oil
.
mplished by
let just abov
switch to OF
cooling cycle
load and de
n the hot noz
nutes after se
APU deceler
e APU shuts
lected to OF
bine engine
m either direc
ed into 270V
ated by the
equence is a
tch to be in t
0 ft., just air
ude although
kes air from
pressor. The
ction in altit
d by IGV’s tow
when operati
f the APU.
il pressure, o
foregoing, i
and many m
through a p
quantity is
y exhaust ai
ve the exhau
FF, the ECU
e closes the A
creases the
zzles which c
electing the
rates to ± 3
down throu
F.
that can su
ctly the mai
VDC for start
blue APU OF
automatically
the ON positi
to 17.000 f
h recommen
m the load c
more air ta
tude use, es
ward the loa
ng for an ex
overspeed o
ncluding EC
more. The st
protection or
low or a ge
r used as a
st.
determines
APU BAV an
EGT prevent
can affect th
APU to OFF,
0% to preve
ugh a malfun
upply AC po
n battery (2
er operation
FF BUS light.
y determine
ion to energ
ft. and just A
nded at 25.0
compressor
ken in, the l
pecially with
ad compresso
xtended time
r when a FA
U failure, lo
art limit is 2
r when the g
enerator ma
an educator
a cooling c
d trips the g
ting so called
e flame patt
, this allows
ent the inlet
ction, the Fi
ower and
8VDC) or
n. At 95%
. (90 KVA
ed by the
ize.
AC power
00 ft. Air
which is
ower the
h air and
or. When
e select a
AULT light
oss of DC
2 minutes
generator
lfunction
to draw
ycle of 1
generator
d cooking
tern)
the inlet
t duct to
re Switch
Auto Slat System
The Auto Slat system operates the LE slats automatically in flight when you’re approaching a stall
under certain conditions just before the stick shaker becomes active.
These conditions are when the flaps are at position 1 – 5 and hydraulic pressure is available through:
• Hydraulic system B
• PTU (extend & retract)
• Standby hydraulic system (extend only)
* With alternate Flap use, the Auto Slat function is not available.
* With a short field performance configuration the Auto Slat operates with flap selections 1 – 25.
At the flap position 1 – 5 the LE slats are in the intermediate (extend) position and the LE flaps at
their only extended position . . . FULL. When the aircraft approaches the stall angle/speed region
determined by the Stall Management and Yaw Damper (SMYD) computer, the Flaps/Slats Electronic
Unit (FSEU) command the LE slats to the FULL extend position to prevent entering a stall condition.
Another action by the FSEU is to delay the “transit lights” to operate for 12 seconds thereby
preventing the LE devices transit lights to illuminate.
When thrust is increased/stick force relaxed and the aircraft flies out of this condition (higher speed,
lower AOA) the Auto Slat system drives the LE slats back to the intermediate extend position. Also
here the transit lights will not illuminate.
When the Auto Slat systems fails to operate or is not available by any cause, the AUTOSLAT FAIL
indication illuminates on the flight control panel. When 1 SMYD computer fails the other will
automatically take over and would go unnoticed unless you press RECAL during an Auto Slat
condition.
Engine Electronic Control (EEC)
The EEC is mounted on the right top side of the fan duct and exists of two computers (channel 1 & 2),
where one is active and the other standby although they’re both operating and cross linked during
normal operation. The EEC receives numerous environmental and engine input signals to calculate
fuel and control outputs to operate the engine and identifies the engines thrust rating by a pre‐
selected identification plug. Doing so it heats up and needs to be cooled which is achieved by tapping
off, and directing fan air to the EEC.
Normal power source of the EEC is an alternator mounted on front of the engine gearbox but is only
valid when the gearbox (N2) reaches 15%. Before 15% N2, the EEC is powered by Transfer Bus 1 or 2
(Eng. 1 or 2) if available, and becomes energized when the Start Switch is placed to GRD or CONT or,
when the Start Lever is moved to IDLE. A de‐energized EEC is indicated by blank engine indication
boxes on the upper and lower DU’s even when the EEC button illuminates a white ON, just indicating
that the EEC is selected to the normal mode. In this case the only indication visible directly from the
sensors are N1, N2, Oil quantity and the vibration indicator, all others are blank. So . . . during a
battery start (emergency power), indications of EGT, fuel flow, oil pressure and oil temperature
remain blank until the alternator reaches 15%.
On the aft overhead engine panel there are the two guarded EEC control buttons to select the EEC to
the NORMAL mode of operation (white ON light), or the manual HARD ALTERNATE mode of
operation (amber ALT light). An undispatchable failing EEC is indicated also on the engine panel by a
ENG CONTROL light and will only illuminate when on the ground and the engine N2 >50%.
A little teaser . . . . the last indication on the engine panel are two REVERSER lights . . . when and how
long do they illuminate amber during normal operation?
When things go wrong and beyond basic systems
knowledge
The next post is an actual situation that happened, losing a Transfer Bus in flight. I’ve tried to simplify
the explanation but in fact it’s just an indicator of what CAN happen. At this point Non Normal
Procedures, CRM and common sense is needed to fly out of these situations.
It started with a MASTER CAUTION and a right SOURCE OFF, indicating that XFR bus 2 was not
powered by its “last selected source” but by Transfer Bus 1. QRH tells us to select the GEN switch
(affected side) ON what this time caused a TRANSFER BUS 2 OFF to illuminate with additional related
indications. (DEU 2 and others, (check the power source booklet to find out) Next the APU was
started and when attempted to connect the generator, a BATTERY DISCHARGE illuminated indicating
an excessive discharge of a battery, with multiple additional indications. The crew decided to stop
further procedures and investigation and used the system “as is”. To give you an idea, the Indications
involved: battery discharge, master caution, right hand source off, right hand transfer bus off, Mach
trim fail, auto slat fail, fuel pump 2 fwd., fuel pump 1 aft, electrical hydraulic pump #2, probe heat B,
engine EEC alternate, zone temperature.
After this ordeal the crew managed to land safely with this reduced electrical power condition and
multiple caution indications.
What actually has happened was that the Generator Control Unit (GCU) 2 had received an erratic
signal through the Line Current Transformer (LCT) that IDG2 was connected to the transfer bus. This
signal is then transferred to the Bus Power Control Unit (BPCU) who arranges switching in the
electrical AC system to provide in the two major rules:
• No paralleling of AC sources
• An AC source connecting to a Transfer Bus disconnects the previous source (look at the first
rule)
This erroneous signal locked out the possibility to connect the APU or other AC sources like Transfer
Bus 1 to Transfer Bus 2. However, as IDG 2 in fact was not connected, transfer bus 2 lost power. The
erroneous indication must have originated at the GCB 2 (unit connecting IDG 2 to bus 2) itself,
indicating the switch had closed although it had not moved.
The BAT
the Batt
when a b
• C
• C
• C
Mind yo
Transfer
TTERY DISCHA
tery Bus as a
battery outp
Current draw
Current draw
Current draw
ou, normally
r Bus 1 which
ARGE is prob
also the DC 2
put condition
w is more tha
w is more tha
w is more tha
when Trans
h obviously d
bably caused
2 system (TR
ns exists of:
an 5 amps fo
an 15 amps f
an 100 amps
sfer Bus 2 is
didn’t happe
d by the a (ex
R 2 & TR 3)
or 95 second
for 25 secon
s for 1.2 seco
de‐energize
n.
xcessive) ma
were not po
s
ds
onds.
ed the Transf
in battery di
owered anym
fer 3 Relay w
ischarge by p
more and illu
would switch
powering
uminates
h TR 3 to
Engine fire detection
The engine fire detection system consist of a fire, and an overheat detection inside the nacelle which
are only active when the engine is operating. Temperatures are guarded by 2 (A & B) detector loops
which operate by expanding gas pressure inside the loop elements thereby activating an OVERHEAT,
a FIRE or a FAULT (leaking loop tube) contact. The engine areas covered by the loops are inside the
nacelles around the fan, and the “core” hot section so . . . a torch (see image) would go undetected
as it occurs inside the engine.
• OVERHEAT detection is indicated by an OVHT/DET, 2 MASTER CAUTION and respective ENG
OVERHEAT indication. (± 170°C around the fan section and 340°C around the hot section)
• FIRE detection would be indicated by 2 MASTER FIRE WARNING, the respective FIRE SWITCH,
an OVHT/DET, 2 MASTER CAUTION and an audio FIRE BELL warning. (± 300°C around the fan
and 450°C around the hot section)
When either of the foregoing occurs the fire switch unlocks to allow it to be pulled up.
A fire or overheat is detected when both loops exceed the mentioned limits and when one loop fails,
it’ll go unnoticed and the detection system automatically switches to a single loop operation. One
failing loop will only illuminate a FAULT during a test (also not on RECALL) and when both loops fail,
the FAULT light illuminates but NOT the MASTER CAUTION.
The detection tests on preflight are:
• The OVHT/FIRE test which checks the operation of the engine & APU fire detection control
module located in the E&E bay and not to forget the indications on the flight deck.
• A FAULT/INOP test checks the FAULT detection circuits (loops and elements) and the flight
deck indications by simulating a dual loop failure.
Note that the APU fire detection also operates during the FIRE test and is visible/audible in the right
main wheel well on the APU Ground Control Panel during pre‐flight.
Feel D
The FEEL
(The fee
supporte
1. The fi
When e
PRESS li
prevents
gear sele
2. The se
dynamic
the com
illuminat
3. The t
Feel Shi
approac
opening
DIFF PRE
Note on
operatio
Differen
L DIFF PRESS
el system s
ed elevator p
irst one is re
ither hydrau
ght illumina
s the light fr
ection.
econd is rela
c pressure fr
mputer recei
tes. (failed p
hird is relate
ift module (
hing the stal
prematurely
ESS also illum
n the last sy
onal.
ntial
S indication o
simulates “a
panels)
elated to a d
ulic system p
ates on the
om “flickerin
ated to the d
rom the two
ives an erra
probe heater
ed to the St
(EFS), which
ll region. Thi
y providing a
minates after
ystem, it’s i
on the flight
actual feel f
differential o
pressure dro
flight contro
ng” when pr
ynamic air p
pitot tubes
atic signal i
and icing co
all Managem
h creates a
s force uses
a higher than
r 30 seconds
inhibited <1
control pane
forces” at t
of A & B hyd
ops > 25% re
ol panel wit
ressure drop
pressure sup
mounted o
t’d be the
onditions)
ment and Ya
±4 times h
a reduced sy
n normal A s
.
100 ft. RA a
el can illumin
the control
draulic press
elated to the
th a 30 seco
ps in either s
ply to the Ele
n either side
same as th
aw Damper (
higher forwa
ystem A pres
ystem press
and AP sele
nate in the fo
column fro
sure to the e
e higher pre
ond delay. T
ystem by a h
evator Feel C
e of the vert
he pressure
(SMYD), and
ard control
ssure and wh
ure to the fe
cted, and w
ollowing case
om the hyd
elevator fee
essure, the F
The 30 seco
high demand
Computer. It
tical stabilize
drop and
d a so called
column for
hen this redu
eel actuator,
when the EF
es.
raulically
l system.
FEEL DIFF
nd delay
d such as
t receives
er. When
the light
Elevator
ce when
ucer fails,
the FEEL
FS is not
Fuel
De fuel s
Even at
cannot b
position
the syste
lower th
pump flo
which in
time (th
tanks. Th
off) but
operatin
tank #1 w
Note: th
decreasi
to run er
Note: w
There is
half full
emptyin
at requir
(>453, th
Scaveng
scavenge jet
0 Kgs indica
be sucked u
. To be able
em, next co
han half full.
ow to creat
n turn draws
e pump cap
he book say
when you’ll
ng. When the
which obvio
e “dissolved
ng pressure
rratic or eve
hen both ce
no bypass v
to even star
g the center
red safe leve
he main tank
ge Jet Pu
pump scave
ation there is
p by the sca
to use this la
onditions nee
(< 1990 Kgs
e a negative
s fuel from t
acity is 100–
s that the sy
remove the
e center tan
usly does no
air” story of
over the fu
n flame out w
enter tank fu
valve provisio
rt the scaven
r tank. Unde
els and a pos
ks have to be
ump
enges residua
s still some
avenge line o
ast bit of fue
ed to be me
s) When the
e pressure in
he center ta
–200 Kgs/hr.
ystem contin
e controlled c
k is depleted
o harm to eng
f fuel. When
el, air bubbl
when sucked
uel pumps a
on for suctio
nge jet pump
r these cond
sible overstr
e full and >72
al trapped fu
residual fue
of the cente
el, a center t
et; the LEFT
e float type s
n the (non‐r
ank relieving
. (AMM)) a r
nues to run f
condition (LE
d, the scave
gine #1 oper
on suction f
es (aeration
d up though
are inoperat
on feed, also
p. Even so, th
ditions you’ll
ress of the w
26, CONFIG)
uel from the
l in the cent
er tank boos
tank scaveng
FWD pump
shutoff valve
rotating part
it in tank #
relatively sm
for the rema
EFT FWD fue
nge pump d
ration.
feed with a h
) appear in t
the bypass v
ive, fuel wil
o the left ma
he scavenge
use main ta
wing roots ari
center tank
ter tank. Thi
st pumps be
ge system is
operating a
e opens, it a
ts) eductor t
1. Of course
mall imbalanc
ainder of the
el pump) als
draws air fro
high fuel tem
the fuel pos
valve.
l be trapped
in tank quan
rate is insuf
ank fuel befo
ses.
to tank #1.
s fuel is trap
cause of its
provided. To
and tank #1
allows LEFT F
type scaven
e this will cre
ce between
e flight (can’t
o the jet pum
m the cente
mperature an
sibly causing
d in the cen
ntity has to b
fficient to be
ore the cente
pped and
elevated
o activate
quantity
FWD fuel
ge pump
eate over
the main
t be shut
mp stops
er tank to
nd a rapid
g engines
nter tank.
be below
e used for
er tank is
Fuel valves
Let’s look at the most important valves in the fuel system, the Spar Fuel Valve and the Engine Fuel
Valve a bit further than needed but still at an acceptable level. It will clarify what actually happens
specifically with the Engine Valve. By all means just remember the easy way as the FCOM explains.
The #1 most important fuel valve is the Spar Fuel Valve. This 28 VDC valve is mounted in the front
wall “spar” of the main fuel tank supplying fuel to the fuel feed line of the engine. The DC power
comes from the Hot Battery Bus and the valve even has an own recharging Battery Power Pack to be
able to positively close the valve in case of an emergency such as a separated engine. The valve
opens when the Start Lever is placed in the IDLE position and closes by CUTOFF of that Start Lever, or
by pulling its Fire Switch. When the valve is closed it shows a dim blue light even with the Start Lever
in CUTOFF as I always explain that any blue light is a “not standard flight condition light”, knowing
that the book says it’s a status light.
The Engine Fuel Valve is actually the High Pressure Shut Off Valve (HPSOV) and is integral with the
Hydro Mechanical Unit (HMU) on the accessory gearbox. The valve opens and closes by the same
controls as the Spar Fuel Valve but its actual opening is a bit more complicated. It relies on the so
called Fuel Metering Valve (FMV) which is under control of the EEC. So, when conditions meet the
requirements to open the HPSOV, the EEC signals the FMV to open up the HPSOV by servo fuel
pressure.
On the other hand the closing of the HPSOV is achieved by the Start Lever or Fire Switch, the EEC
energizes the CLOSED SOLONOID of the HPSOV which uses 28VDC from the Battery Bus. During
engine start this FMV is controlled by the EEC and when conditions dictate the HPSOV (Engine Fuel
Valve) to close, the EEC commands the FMV and thereby the HPSOV to close in the following
conditions:
• A Hot Start occurs (>725°C) on the ground (exceedance protection)
• If the engine decays after idle speed during start below 50% N2 speed and EGT exceeds the
start limit
• The EEC senses a “wet start” meaning no EGT rise within 15 seconds after the Start Lever is
at Idle (YOU are the start limit for the EGT rise which is 10 seconds!!!)
All of these conditions will be indicated by a bright ENG VALVE CLOSED light.
Note that with an updated EEC software (7.B.Q and later) the EEC also provides a protection when
approaching a Hot Start meaning a rapid increase in EGT.
The 115/200 VAC, 400 Hz, 90 KVA Integrated Drive Generator.
AC Generator
I recently received a request from one of our followers to explain the operation of a brushless
generator. I’ve send the explanation and thought on sharing this generic AC power generation info of
an aircraft AC brushless generator. I’ve used the AC generator I’m familiar with and adjusted the
image toward that generic explanation and added the 737 protection circuits in the GCU.
The AC Generator is an assembly of three generators:
• Permanent Magnet Generator (PMG)
• Exciter Generator
• Main Generator
The most important Rotor components of the AC Generator are:
• Permanent Magnet Generator rotor
• Exciter Generator Rotor; which includes also the Rotating Rectifiers (3) and resistors (3)
• Main Generator Rotor
The most important Stator components of the AC Generator are:
• PMG Stationary Armature; output: 39 VAC, 1 ø, 600 Hz
• Exciter Generator Stationary Field; input: 28 VDC pulsating, 1,200 Hz
• Main Generator Stationary Field; output: 115/200 VAC, 3 ø, 400 Hz
Once the engine gearbox (N2) on which the generator has been installed has come on speed, voltage
is excited in the PMG. This will be a 39 VAC, 600 Hz, 1 ø, at 100% revolutions of the IDG (± 12,000
RPM of the generator). This voltage is fed to the voltage regulator in the Generator Control Unit
(GCU) through a DC Power Supply where it is converted into a pulsating direct voltage of 28 VDC,
1.200 Hz.
The output of the voltage regulator is linked through the closed Generator Control Relay (GCR) to the
Stator of the Exciter Generator which excites a 3 ø AC voltage in the Rotor. This AC voltage is than
rectified by three rotating rectifiers and subsequently supplied to the Rotor of the Main Generator.
The last step is that the Main Generator rotor field excites the required 115/200 VAC, 400 Hz, in the
Main Generator Stator. The 115 VAC is the voltage taken from one phase and ground and the 200
VAC is the voltage between two phases (115 x √3) which explains the ra ng of what the generator
can generate (115/200 VAC).
The above shows that there is no need an external voltage source to ensure the generator is in
operation, that’s why the system is also referred to as being "Self‐supported".
OK the easy way is that the Permanent Magnet Generator (PMG) rotates by the IDG on the same
shaft as the exciter‐, and Main rotors. The generated (39 VAC) is rectified to a pulsating DC in the
control unit and send to the exciter stator. This DC power creates an alternate current in the exciter
rotor and is rectified by the rotating rectifiers where after it finally creates an alternate current in the
three main generator stator. This is the 115 VAC/400 Hz output of the generator and is monitored by
the current transformers that relaxes or intensifies the DC power toward the exciter generator to the
requested load of the electrical system.
The in th
exciter f
generato
he image sh
field, which
or switch is s
own protect
h de‐energiz
selected OFF
tions in the
es the gene
F.
CDU will de‐
erator. This
‐energize th
de‐energiz
e GCR there
ing GCR als
eby de‐energ
so occurs w
gizing the
when the
Isola
The isola
AC Trans
conditio
When th
switch”
position
Isolation
When a
When a
to be use
Note the
Isolation
you need
ground a
there is
When th
AC powe
* A gene
This is a
lost pow
tion val
ation valve se
sfer Bus 1 bu
n bay. Becau
he Isolation s
positions. Th
the isolation
n valve opens
Pack switch
Bleed is sele
ed for the of
e isolation va
n Valve when
d to battery
air connectio
no personne
his would be
er with the is
eral rule for e
nice thing to
wer and a DC
lve
eparates the
ut also can be
use it’s AC po
switch is in th
hey are the P
n valve is clo
s in the AUTO
is OFF, the Is
ected OFF the
ff side WTAI.
alve logic is r
n in AUTO. Af
start engine
on is located
el allowed in
a battery sta
solation valv
electrical pow
o know also f
powered ins
e left, from th
e manually o
ower* it will
he AUTO pos
Pack and Blee
osed. On the
O selection.
solation valv
e Isolation va
.
related to sw
fter flight th
s when ther
on the right
the vicinity o
art you’ll nee
e switch OPE
wer is; “AC li
for analog in
strument wi
he right side
opened/close
fail in the se
sition the va
ed switches,
other hand i
ve opens to c
alve opens to
witch position
e Isolation v
e is no APU o
t side of the m
of the turnin
ed the isolat
EN, the valve
ies, DC dies”
nstruments, a
ll drop off to
e of the bleed
ed by a cont
elected posit
lve opening
when all the
if any corner
create equal
o allow air fr
n so a tripped
alve should b
or external e
manifold clo
ng engine so
ion valve to
e is still in the
.
an AC power
o zero.
d manifold. I
rol lever, acc
ion when po
relies on the
ese switches
r switch is se
performanc
rom either si
d pack or ble
be selected O
electrical pow
ose to engine
we have to s
be open, so
e open posit
red instrume
t is powered
cessible in th
ower is remo
e so‐called “c
s are NOT in t
elected to OF
ce of the eng
ide of the ma
eed will not o
OPEN just in
wer available
e #2. When N
start engine
when you re
tion.
ent stays whe
d from
he left air
oved.
corner
the OFF
FF the
ines.
anifold
open the
case
e. The
N2 >20%
#1 first.
emoved
ere it
Manu
Let’s hav
When th
from the
This is al
depressu
When th
attempt
handles,
cockpit f
The need
•
•
•
When op
LG select
selector
not hydr
This also
This proc
and gree
position
When yo
respectiv
When th
centered
of system
locked g
By the w
the doub
ual gear
ve a look at t
he gear is UP
e uplines to t
lso the prefe
urized hydra
he gear (all o
to lower the
, accessible t
floor.
d for this No
Disrupted el
No system A
LG lever stuc
pening the M
tor valve ele
bypass valve
raulically res
o prevents th
cedure is cov
en indicator
.
ou’d pull any
ve gear free‐
he gear is ful
d locked pos
m A pressure
reen lights.
way, there ar
ble green ligh
r extens
this Non Nor
P and the LG
the actuator
erred positio
ulic lines.
r any) does n
e gear. Manu
through the
on Normal pr
ectrical signa
A hydraulic p
ck in the UP
Manual Gear
ectrically dow
e which conn
tricts (locks)
he LG to retra
vered in the
lights illumin
y (or all) “T” h
‐falls down, s
ly down, the
ition. Norma
e, the springs
e 6 green lig
hts for each
sion.
rmal procedu
lever in the O
s which caus
n of the LG le
not extend a
ual extension
Manual Gea
rocedure cou
al to the LG s
ressure avai
or OFF posit
Extension A
wn regardles
nects the hyd
the actuato
act when the
QRH by the
nated, telling
handle it sim
supported b
e downlock “
ally this is acc
s enforce a m
ghts as a redu
strut will giv
ure and its co
OFF position
ses the three
ever during a
after a down
n of the gear
r Extension A
uld be caused
selector valv
lable
ion
Access Door,
s of the LG h
draulic lines
rs down cap
e door is not
LG disagree
g you the gea
mply releases
y gravity (we
bungee” spr
complished
mechanical d
undant indic
ve a backup f
omponents.
n, hydraulic s
e struts to “h
a manual ext
selection, fo
r is accomplis
Access Door
d by:
ve
a “door ope
handle positi
to return so
pability.
flush closed
procedure w
ar is down an
s the uplock
eight) and ai
rings will hold
by a downlo
downlock wh
ation. Neithe
for the down
system A pre
hang” in their
tension atte
ollow the QR
shed by pulli
just behind
n” micro swi
on. This acti
the manual
d after take‐o
with the LG h
nd locked bu
by cable acti
rflow to the
d the downlo
ck actuator b
hich is indicat
er gear is vis
n indication.
essure is rem
r respective
mpt because
RH procedure
ing the three
the FO seat
itch comman
on activates
down select
off and selec
handle UP an
ut not in the
ion where af
extend posit
ock struts in
but with the
ted by (6) do
ible on the N
oved
uplock.
e of the
e in an
e “T”
on the
nds the
the LG
tion does
cted UP.
nd all red
selected
fter the
tion.
an over
absence
own and
NG and
Mech
There ar
Positive
located o
and prev
system/o
The fuse
at a very
fuselage
pressuriz
when th
hanical p
re three mec
safety press
on each side
vent the insid
outflow valv
elage airfram
y low value. T
e just fwd. of
zation system
e inside/out
pressur
chanical adju
ure relief is a
e of the outfl
de/outside p
ve malfunctio
me structure c
The negative
the outflow
m and adjust
side pressur
re relief
sted pressur
accomplishe
ow valve. Th
pressure to e
on. (stuck clo
cannot withs
e pressure re
w valve. This s
ted at just a
re becomes n
f valves
re relief valv
ed by 2 mech
hey are total
exceed +9.1 P
osed outflow
stand large n
elief valve is l
spring‐loade
–1.0 PSID va
negative for
.
es on the 73
hanical adjust
ly independe
PSID in the e
w valve)
negative pres
located at th
d door is als
alue. This wil
example dur
7.
ted pressure
ent of the pr
event of a pre
ssures and is
he right lowe
o not depen
l prevent the
ring a (very)
e relief valve
ressurization
essurization
s protected f
er side of the
ding on the
e aircraft to c
fast descent
s,
system
for that
e
collapse
t.
Nitro
Followin
midair e
tank. The
the Pack
tank fue
pumps d
down aft
flight de
modifica
This prot
Nitrogen
oxygen l
The NGS
panel, so
Indicatio
• O
•
•
The nitro
after its
tank. The
•
•
•
ogen Gen
ng two Boein
xplosion), a
e 737 explos
ks under the
l pumps whi
did not had a
ter ±15 seco
ck when a ce
ations to eac
tective devic
n enriched ai
evel is decre
S has only an
o it has no vi
ons are:
OPERATIONA
DEGRADED (
INOPERATIV
ogen genera
cooled, drive
e NGS opera
Either engine
Fire or smok
Left Pack ove
neratin
g 737CL exp
protection w
sions were ca
tank which f
ch were still
an automatic
onds of LOW
enter tank p
h aircraft.
ce (NGS) divi
ir (NEA) in th
eased by the
indication a
sible clew fo
AL (green)
(blue)
VE (amber)
tion system
en through t
ates automat
e is shut dow
ke detection
erheat
ng System
losion invest
was develope
aused by tra
formed high
running wit
c shut off wit
PRESSURE. T
ump is runni
des Nitrogen
he center tan
NGS to ±12%
available in th
or crews of it
gets bleed a
the separatio
tically only in
wn in flight
in any comp
m
tigations in A
ed by Boeing
pped fuel hig
ly explosive
h an empty
th LOW PRES
This is also th
ing as by the
n from Oxyge
nk to a level w
% which is su
he right main
ts operation
air from the l
on module a
n flight and s
partment
Asia (and oth
g to minimize
gh temperat
vapors. The
center tank.
SSURE as the
he reason th
e FCOM, the
en by a sepa
which will no
ufficient to p
n wheel well
during flight
eft side of th
nd directed t
shuts down i
hers including
e explosive v
tures due to
fuel was ign
Early days c
e newer mod
at someone
book does n
ration modu
ot support co
prevent igniti
l next to the
t.
he pneumati
to a flow val
n the next co
g the B747 T
vapors in the
radiant heat
ited by the c
enter tank fu
dified ones th
has to be on
not cover exp
ule and leave
ombustion. T
ion.
APU fire con
c manifold w
ve into the c
onditions:
TWA 800
center
t from
center
uel
hat shut
n the
plicit
es
The
ntrol
where
center
Outfl
To stay i
The outf
pressuriz
has rake
The valv
valve ele
operated
Automat
control e
controlli
spring lo
The outf
provided
Electrica
• A
t
• A
t
•
V
A mode
or MAN(
The outf
mode of
Just for t
valve to
Aircraft c
low valv
n line with t
flow valve re
zed environm
ed edges for
e is moved b
ectro motors
d by a switch
tic control is
each flight or
ng the outflo
oaded to neu
flow valve in
d the Battery
al power to t
AUTO mode
through CPC
AUTO mode
through CPC
MANUAL mo
VDC Battery
selector is u
(ual).
flow valve re
f operation s
the “mind se
increase pre
control over
ve.
he previous
estricts/regul
ment in the a
noise reduct
by a common
s. Two motor
h when in Ma
accomplishe
r when a ma
ow valve is b
utral and has
dicator show
y Bus is powe
he three ele
1 electrical
C 1. (PRESS C
2 electrical
C 2. (PRESS C
ode electrica
Bus. (PRESS
sed to deter
eceives a clos
o it is not aff
et” when at a
essure in the
rride devices
post, let us l
lates the flow
aircraft. The
tion purpose
n actuator w
rs are operat
anual operat
ed by means
alfunction oc
by a manual t
three positi
ws the actual
ered through
ctro motors
power to the
ONT AUTO 1
power to the
ONT AUTO 2
al power to t
CONT MAN
rmine the op
sed signal wh
fected throu
a high altitud
aircraft whi
.
look at this p
w of conditio
valve is loca
es.
which can be
ted by the pr
tion.
s of 2 Cabin P
curs on the o
toggle switch
ons, CLOSE –
l position of
h the PRESS C
is provided b
e auto electr
1 C/B)
e auto electr
2 C/B)
he manual e
C/B)
peration of th
hen the cabi
ugh the MAN
de and a pres
ch results in
pressurizatio
oned air over
ated at the af
operated by
ressure syste
Pressure Con
operating co
h on the pre
– Neutral – O
the outflow
CONT IND C/
by:
ro motor 1 is
ro motor 2 is
electro moto
he outflow va
n altitude re
NUAL mode.
ssure loss, yo
lowering ca
n componen
rboard, there
ft lower side
y either of th
em controlle
ntrollers (CPC
ontroller. A th
ssurization p
OPEN.
valve in all m
/B.
s supplied by
s supplied by
r is supplied
alve, either A
aches 14.50
ou’d have to
bin altitude.
nt of the 73.
eby creating
e of the fusel
e three outf
ers and one is
C’s) which al
hird way of
panel. The sw
modes of ope
y the 28 VDC
y the 28 VDC
directly by t
AUTO, ALT(e
0 feet in the
o close the ou
g a
age and
low
s directly
ter
witch is
eration
Bus 1
Bus 2
the 28
ernate)
AUTO
utflow
Flight Control “Breakaway” Devices
There are two devices that allow you to control the aircraft in case of a malfunctioning or jammed
control system.
One concerns roll control. When one of the yoke cables (or aileron PCU/spoilers) becomes jammed
or moves freely, the opposite control is still available to roll the aircraft. The two yokes are
interconnected at the base of the co‐pilots control column by the Aileron Transfer Mechanism
through torsion spring friction and a “lost motion device”. If the FO control jams, the spring force can
be overcome by the Captain thereby controlling the aileron PCU through cables. If the Captain
control jams, the FO can control roll by use of the flight spoilers. Note that this only happens when
the yoke has been turned ± 12° which engages a so called “lost motion device” which in turn
operates the flight spoilers.
The second is related to pitch control. When one of the control columns becomes jammed, the crew
can override (breakout) the failing control. The control columns are interconnected below the
cockpit floor by a torque tube with a device that enables the controls to be separated from each
other. The Elevator Breakout Mechanism connects both control columns by two springs which will
separate the columns when ± 30Lbf/13Kgf is used to overcome them. When applied, the control
columns are mechanically separated from each other. Note that deflection of the elevators is
significantly reduced and a higher force is needed to move the elevators. (even higher than with
manual reversion)
Pack
There ar
direction
expansio
direction
the Pack
cooled t
selectors
position,
There ar
Pack. Th
takes ov
a Maste
Caution
When a
Master C
When th
the Blee
that Pac
A Pack a
aircraft i
automat
Note: th
flow thro
& pack
re two Packs
ns, one that g
on turbine) a
ns are mixed
ks through th
o a mixed m
s. (auto zone
, the left Pac
re two comb
ese two Pac
ver if an auto
r Caution lig
light, the pa
Pack becom
Caution light
he Pack cools
d panel. To p
k by demand
utomatically
is in the air w
tic high flow.
e image is ju
ough the pac
k contro
activated by
goes through
and one that
at the outp
he Pack Flow
inimum Pack
e temperatur
ck puts out a
ined Zone/P
k Controllers
o controller fa
ht. When bo
cks will still o
es overloade
t and the Pac
s down and t
prevent this
ding less cold
y provides a
with flaps up
.
ust a simplifie
ck and the co
ol
y an AUTO/H
h a three sta
bypasses th
ut of the exp
w Control and
k output of ±
re range is 1
fixed 24°C a
ack controlle
s have an au
ails. In this c
oth Pack Cont
operate unti
ed by the de
ck Flow Cont
the light exti
condition fro
d air from th
high airflow
. The other c
ed flow and
omponents i
HIGH selectio
age cooling c
e cooling ma
pansion turb
d Shutoff valv
± 18°C as set
8°C – 30°C)W
and the right
ers that cont
to “on side”,
case a PACK
trollers fail, a
l a temperat
mand of coo
trol and Shut
nguishes, th
om re‐occur
e cooling ma
when the ot
conditions re
pack compo
n both contr
on that indivi
ycle (2 air to
achine and it
ine of the co
ve is at ± 212
the lowest o
When these s
t Pack 18°C.
trol the requ
, and a stand
OFF light illu
a Pack OFF li
ture exceeda
ol air, a PACK
toff valve clo
e Pack can b
ring select a
achine bypas
ther Pack is s
equire engine
nent, and co
rollers.
idually has tw
o air heat exc
ts componen
ooling machi
2°C and is co
on the zone
selectors are
ired output
dby “off side
uminates on
ight illumina
ance occur.
K trip off light
oses shutting
be reset by th
higher temp
ssing it.
selected to O
e performan
ontroller ima
wo airflow
changers and
nts. The two
ne. Air that e
onditioned an
temperature
e all in the O
temperature
” control, th
recall togeth
tes with a M
t illuminates
g down that P
he reset butt
perature to “
OFF provided
nce and inhib
age to illustra
d an
flow
enters
nd
e control
FF
e of each
e latter
her with
Master
s with a
Pack.
ton on
“unload”
d the
bits the
ate the
Recir
The recir
bulkhead
compart
relieving
recircula
underne
compart
When a
shut dow
valve sel
On the g
Left REC
On the g
Left REC
In flight
Left REC
Both REC
In flight
Both REC
Reading
this area
rculatio
rculation fan
d. The purpo
tment back i
g the Packs fr
ation fan circ
eath the cabi
tment.
higher amou
wn under sev
lected to AU
ground using
IRC FAN shu
ground using
IRC FAN shu
using engine
IRC FAN shu
CIRC FANS sh
using APU b
CIRC FANS sh
the first par
a heats up by
on fans
ns are located
ose of these f
nto the mix
rom produci
culates air ba
n floor (mix
unt of fresh a
veral conditi
TO or OPEN
g engine blee
ts down whe
g APU bleed a
ts down rega
e bleed air:
ts down whe
hut down wh
leed air:
hut down reg
rt it makes se
y the several
d under the
fans is to re‐
manifold. Do
ng condition
ack into the m
manifold/fa
air is needed
ons with the
:
ed air:
en both Pack
air:
ardless of Pa
en either Pac
hen both Pac
gardless of P
ense that the
operating c
cabin floor o
‐use air draw
oing so there
ned (cool) air
mix manifold
n area), the
d from the pa
e recirculatio
ks are selecte
ack selection
ck is selected
cks are selec
Pack selectio
e left fan (dis
omponents.
on the forwa
wn from the c
e is no need f
r improving e
d from the di
right recircu
acks, the rec
on fans select
ed to high flo
d to high flow
ted to high f
n
stribution co
(my persona
rd cargo com
cabin and dis
for air from t
engine perfo
istribution co
lation fan fro
irculation fa
ted to AUTO
ow
w
flow
ompartment)
al point of vi
mpartment’s
stribution
the Packs, th
ormance. The
ompartment
om the passe
ns are autom
O, and the iso
) shuts down
iew)
s aft
hereby
e left
t
enger
matically
olation
n first as
Hydr
The 3 hy
from the
The stan
can only
A & B re
also send
low quan
panel wh
The A re
The EDP
higher ca
The B re
drain the
anymore
standpip
while us
Minimum
lower DU
Besides t
be a red
The pum
heat exc
ground o
raulic Re
ydraulic fluid
e bleed mani
ndby system
y be checked
servoirs is di
ds a signal to
ntity switch,
hen < 50%.
eservoir has a
is more like
apacity it pu
servoir has a
e entire B re
e but the rem
pe at 72% pre
ing the stand
m quantity fo
U when on th
that, when e
dial indicati
mps heated (c
changers mo
operation, th
eservoi
reservoirs a
ifold to supp
reservoir is p
on 2 gages m
isplayed dire
o the DEU’s f
which displa
a 20% standp
ly to malfun
ts out. (±4x)
a common st
servoir until
maining 1.3 U
eserves fluid
dby hydrauli
or the A & B
he ground an
equipped wit
on when A o
case drain) c
unted on the
here should b
rs
are located in
ply positive fl
pressurized t
mounted on
ectly through
for display o
ays the STAN
pipe to prese
ction becaus
tandpipe for
a 0% indicat
USG can be u
d to this leve
c system.
reservoirs is
nd TE flaps a
th an update
or B quantitie
cooling fluid
e bottom of
be at least 7
n the front o
uid to the pu
through the
the forward
h gages on th
n the lower
NDBY HYD LO
erve fluid to
se of the eng
both system
tion. In this c
used for the
l for both B s
s 76% which
are up, or no
e pin function
es decrease t
return to the
the main tan
60 Kg of fuel
f the main w
umps, preve
B reservoir.
d main whee
he reservoir b
DU. The stan
OW QUANTIT
the EMDP w
gine gearbox
m B pumps so
case the B sy
PTU to oper
system pump
triggers a w
engines are
n to the lowe
to 0%, or inc
e reservoirs,
nks. To achie
l in the tanks
wheel well. T
nting cavitat
These press
l well bulkhe
by a float typ
ndby system
TY light on th
when a leak o
x mounted he
o when a lea
ystem cannot
ate the LE lif
p operation,
hite RF (refil
operating.
er DU on sys
creases to 10
is routed th
eve enough c
s each.
hey are pres
tion and foam
ures (45 – 50
ead. Quantity
pe transmitt
reservoir on
he flight cont
occurs at the
eavy design
ak occurs, flu
t be pressuri
ft devices. A
in case a lea
l) indication
stems, there
06%.
rough oil‐to‐
cooling for o
ssurized
ming.
0 PSI)
y of the
er which
nly has a
trol
EDP.
and
id will
ized
second
ak occurs
on the
can also
‐fuel
n the
The A
The APU
The start
which re
must be
OFF, the
immedia
APU blee
Strangel
(115 VAC
(SPU), w
starter/g
energize
When th
as a sign
The AC g
post and
with low
APU Sta
U is started th
t sequence o
eceives powe
in the ON po
e Switched H
ately without
ed valve to u
y enough po
C). Both volt
where after a
generator in
ed and the AP
he APU RPM
nal that the A
generator co
d can supply
w air densitie
arter/Ge
hrough a sta
of the APU st
er from the S
osition (swit
ot Battery B
t the regular
unload/cool t
ower to the s
ages are firs
Start Conve
the start mo
PU becomes
reaches ±95
APU generato
onsists of the
90 KVA belo
s.
enerato
rter/generat
tarter/gener
Switched Hot
ched hot bat
us and ECU b
r 1 minute co
the APU prio
starter is pro
t changed/b
rter Unit (SC
ode. This sign
s self‐sustain
5% the ECU c
or can assum
e same parts
ow 32,000 fe
or.
tor and when
rator is deter
t Battery Bus
ttery bus ene
become de‐e
ooling cycle.
or shutdown
ovided by eith
oosted to a w
CU) creates t
nal lasts unti
ing and acce
commands th
me the electr
as the “regu
et and 66 KV
n on speed t
rmined by th
s. That is the
ergized) to o
energized wh
(trips the ge
)
her the Batte
whopping 27
he 270 VAC w
il 70% RPM w
elerates furth
he blue APU
rical load.
ular” AC gene
VA at 41,000
ransfers to a
he Generator
e reason why
operate the A
hich in turn s
enerator off l
ery (28 VDC)
70 VDC by th
which is nee
where the SP
her to its ope
GEN OFF BU
erator as des
because of A
an AC genera
r Control Uni
y the Battery
APU. When s
shuts down t
line and clos
), or Transfer
he Start Pow
eded to drive
PU becomes
erating RPM
US light to illu
scribed in an
APU load cap
ator.
it (GCU)
y Switch
switched
the APU
es the
r Bus 1
er Unit
e the
de‐
.
uminate
earlier
pabilities
Land
The Land
The simp
the alter
The seco
met befo
retractio
1.
2.
3. A
The PSEU
PSEU lig
737’s sys
pressuriz
volume t
gear retr
conditio
drag by a
normal f
The Pow
has low
higher sp
devices w
reservoi
ding Gea
ding Gear Tra
plest is to tra
rnate hydrau
ond way of o
ore the LG tr
on to the alte
Engine #1, N
Landing Gea
Any gear NO
U is triggered
ht is inhibite
stems. Losin
ze the A syst
than the EDP
raction whic
ns when you
any extende
fast retractio
wer Transfer
output. It su
peed as it wo
when system
r to be used
ar Trans
ansfer Valve
ansfer the no
ulic system B
operation (in
ransfer valve
ernate hydra
N2 below 50%
r Handle in U
OT in the UP a
d by those co
ed from T/O t
g engine #1
tem is by me
P. This would
h is an unwa
u need to cle
d gear. In th
on of the gea
Unit (PTU) is
upports the B
ould be 4 tim
m B fluid is lo
by the PTU.
sfer Valv
e has two wa
ose wheel ste
on the grou
flight) is a b
e moves from
aulic system
%
UP
and locked p
onditions an
thrust until 3
stops the ED
eans of the E
d result in 4 t
anted situatio
ean that conf
at case the r
ar is achieved
s a backup to
B system elec
mes slower w
ost to a 0% in
ve
ys of operat
eering opera
und (only), by
it more com
m its normal
B.
position
d moves the
30 seconds a
DP (hydraulic
lectric Hydra
times slower
on just after
figuration as
retraction is
d.
o the LE lift d
ctric hydraul
with just the
ndication, sti
ion.
ation from its
y a switch on
plex as it ha
hydraulic sys
e LG transfer
after landing
c system A) o
aulic Pump w
r movement
takeoff or o
fast as poss
transferred f
devices if the
ic pump to o
EMDP. The P
ll holding ± 1
s normal hyd
n the left fro
s 3 condition
stem A opera
valve to sys
but DOES gu
output so the
which puts ou
of its compo
on a go‐aroun
ible to decre
from the A, t
hydraulic sy
operate the l
PTU can also
1.3 USG resid
draulic syste
nt (Capt) pan
ns that needs
ation for gea
tem B. Note
uard and ope
e only way to
ut 4 times le
onents includ
nd with N‐1
ease the mas
to the B syst
ystem B EDP
lift devices in
operate the
dual fluid in t
m A, to
nel.
s to be
ar
that the
erate the
o
ss
ding a
ssive
tem so a
fails or
n a
e lift
the
PTU
The PTU
1. A
2. S
3. T
If this oc
motor. T
below th
there are
not visib
Note tha
AND retr
only)
Teaser .
A →B
1.
2.
3.
4.
5.
A →B
1.
2.
3.
4.
B →A
1.
2.
3.
4.
5.
6. S
operates w
Airborne and
System B ED
TE flaps less
ccurs the PTU
The motor dr
he standpipe
e return line
ble on comm
at the PTU do
racted by us
. . .how CAN
EMDP's OFF
Release park
EMDP A, ON
EMDP A, OF
EMDP B, ON
EMDP's ON.
EMDP B, OFF
EMDP A, ON
EMDP B, ON
EMDP's OFF
Either FLT CO
No1 thrust r
FLT CONTRO
EMDP A, ON
Stow No 1 th
hen the next
d,
P pressure lo
than 15° but
U control val
rives a hydra
e on the bott
es back to the
on simplified
oes NOT tran
e of the PTU
N you transfe
.
king brakes,
N and apply p
F and depres
and release
F and depres
N and apply p
and release
ONTROL to S
everser OUT
OL to ON.
N.
hrust reverse
t conditions
ow (< 2350 P
t not UP.
ve opens, al
aulic pump th
tom of the B
e B reservoir
d (FCOM) sch
nsfer fluid fro
U but will ope
er hydraulic f
deplete accu
parking brake
ssurize by co
e parking bra
ssurize by co
parking brake
e parking bra
STBY RUD.
T (uses stand
er (using sys
are met:
PSI) and,
lowing syste
hrough a com
reservoir to
r from the PT
hematics.
om A to B, a
erate accord
fluid from A→
umulator (<1
es.
ontrol colum
kes. (Sends t
ontrol colum
es. (Uses flui
kes. (Sends t
dby hyd sys)
A)
m A pressur
mmon shaft
operate the
TU hydro mo
nd that the s
ing the used
→B or B→A?
1800 PSI)
n movement
the fluid bac
n movement
d from syste
the fluid bac
e to operate
and uses the
e selected lift
otor and used
selected dev
pumps. (EM
??
t.
ck to system
t.
em A)
ck to system
e the PTU hyd
e 1.3 USG fro
t devices. Of
d devices wh
vices can be e
MDP + PTU or
B)
B)
draulic
om
course
hich are
extended
r PTU
Wing
Wing an
ice woul
“runback
negative
Note tha
note tha
The oute
as, a ble
that area
too muc
WTAI th
Where t
overhea
fan air to
overhea
predeter
During t
due to it
Although
regularly
The milit
expulsio
and vert
weather
deforms
g Therm
ti‐ice is prov
d constantly
k” over the w
e effect on en
at use above
at (ENG) anti‐
er slats are n
ed manifold,
a anyway an
h. Eventually
e stall warni
here is little
ting. First th
o extra cool t
t sensor (± 1
rmined value
he design/te
ts position in
h some ice c
y changes th
tary version
n de‐icing sy
tical stabilize
r mission ass
s the LE self b
mal Anti
vided for the
y heat up the
wing and pos
ngine perfor
FL 350 may
‐ice is not re
not de‐iced b
, telescopic t
d they realiz
y some drag
ng compute
cooling airfl
e engine ble
the engine b
125 °C) which
e.
est phase it t
n relation to t
an build up i
e AOA and e
of the Boein
ystems (EME
ers. The syste
ignments of
by using low
Ice (WT
inner three
e LE thereby
ssibly freezin
mance and f
cause a dua
equired when
because the n
tube and spr
zed that som
and increas
r remains se
ow over the
eed air is extr
bleed air for m
h closes both
urned out th
the engines
in that area,
eventually sh
ng 737, the P
EDS) installed
em is special
this aircraft
electrical cu
TAI)
LE slats only
melting the
ng up on fligh
fuel consump
l bleed trip o
n < ‐40°C SAT
narrow oute
ray tubes. Th
me ice accreti
e in stall spe
t with increa
LE on the gr
ra cooled thr
maximum LE
h WTAI valve
hat ice does
causing hot
it doesn’t ha
hedding ice u
8 Poseidon,
d on the lead
ly designed f
and does ba
urrent (28VD
y and is prefe
ice crystals i
ht controls. B
ption.
off by the req
T.
r slat cannot
he wing is act
on on that p
eed occurs, n
ased speed lo
round, they a
rough the pr
E cooling on
es when exce
not accumul
air from the
ave any adve
under the new
does have a
ding edges of
for the aggre
asically the sa
C and 25 Am
erably used a
mmediately
Besides that
quest of the
t hold the ha
tually not pro
part of the w
ot to forget
ogic.
are protecte
e‐cooler whi
the ground.
eeded and op
ate on the e
engines stri
erse consequ
w conditions
so‐called ele
f the raked w
essive slow a
ame as a de‐
mps).
as a DE‐icer.
, creating wa
it would hav
amount of a
ardware need
oducing muc
ing would no
that in case
d against
ich allows ta
Second ther
pening up ag
empennage,
king the emp
uences (the s
s).
ectro‐mecha
wingtips, hor
and low level
‐icing boot b
ANTI‐
ater
ve a
air also
ded such
ch lift in
ot hurt
you use
pped off
re is an
gain at a
mainly
pennage.
stabilizer
anical
izontal
l cold
but
B737 Yaw damping
Airplanes with continued Dutch Roll tendencies usually are equipped with gyro stabilized yaw
dampers. The Boeing 737 has two yaw dampers, a primary– and a standby yaw damper that keeps
the airplane stable around the vertical axis when selected ON and with the respective hydraulic
system pressurized through minimum SMYD generated rudder inputs.
When engaged in NORMAL OPERATION, the primary yaw damper provides input to the main Rudder
Power Control Unit (PCU) solenoid valve and is controlled by the Stall Management and Yaw Damper
Computer 1 (SMYD 1). The input solenoid valve uses hydraulic system B to move the yaw damper
actuator which ads in the mechanical rudder input. The yaw damper itself does not feedback motion
back to the rudder pedals. The yaw damper input to rudder movement is limited to 2° with flaps up,
and 3° with flaps down.
To engage the primary yaw damper select:
• Hydraulic system B ON,
• FLT CONTROL B switch ON and
• YAW DAMPER switch ON
o Engage light extinguishes
When engaged during MANUAL REVERSION, the standby yaw damper uses the standby Rudder PCU
and is controlled by SMYD 2 which operates with standby hydraulic system pressure.
During manual reversion the so‐called “Wheel To Rudder Interconnect System (WTRIS) supports
standby rudder operation through SMYD 2 which receives an input signal from the Captains control
wheel for coordinated turns during manual reversion.
To engage WTRIS and standby yaw damping select:
• Both FLT CONTROL switches OFF
• At least one FLT CONTROL switch to STBY RUD
• YAW DAMPER switch ON
o Engage light extinguishes
Both FLT CONTROL A and B switches must be OFF to enable SMYD 2, and one or both switches must
then be in the STBY RUD position to provide standby hydraulic pressure. WTRIS only operates at < M
0.4 and yaw damper input to the standby rudder PCU movements are limited to 2° with flaps up, and
2.5° with flaps down.
Both yaw damper systems are selected by a common “engage switch” on the Flight Control panel.
When selected ON and the YAW DAMPER light extinguished, it only tells you the respective yaw
damper is engaged regardless of operating by hydraulic pressure. During preflight the switch holds
and the light extinguishes even without hydraulic system B pressure. The other way, if you’d lose
system B pressure, the switch still holds with no light illuminated but primary yaw damping is lost.
The switch only kicks OFF when the FLT CONTROL B switch is deselected from the ON position. To
regain yaw damping you would have to transfer to manual reversion to operate the standby yaw
damper with the standby hydraulic system which you (of course) will not do.
Zone
Tempera
tempera
for each
manifold
the vario
controlle
from eit
Cont Cab
Passenge
and the
there is a
by the re
In the no
tempera
Unbalan
The left
lowest P
Unbalan
The left
Pack put
Single Pa
valves cl
Trim swi
Cabin te
tempera
Temp se
temper
ature contro
ature range s
individual co
d where the
ous control e
ers, a primar
her Zone/Pa
bin ZONE tem
er Cabin Con
two cabin re
an exceedan
eset button w
ormal mode
ature, the rem
ced mode (C
Pack produc
Passenger Ca
ced average
Pack produc
ts out an ave
ack operatio
ose and the
itch OFF, all t
mperature w
atures.
electors OFF
rature c
l is achieved
selection is fr
ompartment
right Pack pr
electronics fo
ry and a back
ck controller
mp light with
ntroller fails t
equirement w
nce of duct te
when cooled
the Packs pr
maining zone
Control Cabin
ces the select
bin selected
e mode (any
ces the select
erage of both
n and Trim O
Pack averag
trim modula
where the rig
will create a
control
d by mixing c
rom 18°C – 3
t. The left Pa
rovides 100%
or the Cont C
kup where th
r. (see previo
h a Master C
the ZONE te
will be avera
emperature,
d down. (sele
roduce a tem
es use trim (
n trim air ma
ted Control C
d temperatur
Passenger C
ted tempera
h Passenger C
ON results in
ges the three
ating valves a
ght pack pro
fixed 24°C o
ool Pack air w
30°C through
ack provides
% to the mix
Cabin and Pa
he Passenger
ous image) If
aution, if on
mperature li
ged. A ZONE
, the respect
ect colder on
mperature ac
hot) air requ
alfunction)
Cabin tempe
re, the Passe
abin trim air
ature but the
Cabin selecte
normal tem
e compartme
are close and
duces an ave
output from
with hot Pac
h mixing cold
20% to the C
manifold. Th
assenger zon
r Cabin has o
f both Cont C
e fails they i
ight and Mas
E temperatur
ive trim valv
n that area)
ccording the
uired for the
erature and t
enger zone tr
r malfunction
e trim air valv
ed temperat
mp control, w
ent requirem
d the left pac
erage of the
the left and
ck by‐pass ai
d air from the
Control Cabi
he Zone/Pac
es. The Cont
only one con
Cabin contro
lluminate on
ster Caution
re light also i
ve will close w
selection of
ir selected te
the right Pac
rim valves sti
n)
ve still opera
tures.
with Trim swit
ments.
ck produces t
Passenger C
18°C from th
r. The norma
e Packs with
n and 80% to
k controllers
t Cabin has tw
troller for ea
ollers fail you
n recall. If a
illuminates
illuminate w
which can be
the lowest
emperature.
ck puts out th
ill operate.
ates and the
tch OFF all tr
the selected
Cabin selecte
he right Pack
al
trim air
o the mix
s hold
wo
ach area
u’d get a
on recall
when
e reset
he
right
rim
Control
ed
k.
Lavat
I noted a
direction
Let’s sta
extinguis
The lava
The lava
you still
indicatio
In the ca
1. S
As the n
has a gre
smoke is
2.
Located
3.
At each
indicates
4. A
On these
and dete
that iden
panel. Th
test the
5.
The PA s
tory “fir
also B737 ca
n, of course a
rt with Boein
shing NOT p
tory smoke d
tory is equip
find a “SMO
on on the flig
abin we find
Smoke Dete
ame says, it’
een (power)
s evident for
Lavatory Cal
above the la
Master Lava
EXIT locator
s there is sm
Attendant Co
e panels ther
ect FAULTS. W
ntifies the ar
he switches
failing detec
Passenger A
sounds a rep
re prote
bin crew “Lik
also “need to
ng’s approac
rotection ;‐)
detection sy
pped with a s
OKE” annunci
ght deck.
smoke detec
ctor Unit
’s a smoke de
light and a r
> 8 seconds
l Light
avatory and i
tory Call Ligh
light there a
moke detecte
ontrol Panel
re are more
When smoke
rea where th
and lights on
ctor is indicat
ddress (PA) s
etitive high c
ection”.
kes” to our F
o knows” for
ch of “fire pro
ystem needs
smoke detec
ator light at
ction indicat
etection and
red (smoke d
s.
is a Call/Rese
ht
are three ind
d in the lava
s (fwd.& aft)
options than
e is detected
e smoke is d
n the panel a
ted through
system
chime when
FB page, so I’
r flight crews
otection”, of
28 VDC from
ction system
the P5 forw
ions through
d the unit is m
detected) ligh
et Light that
icator lights
atory in that
)
n just smoke
d a red light f
detected and
are self‐expla
the location
smoke is de
’ll try to aim
s.
f course we’
m DC Bus # 1
and a fire ex
ard overhea
h the next co
mounted aga
ht, also an al
flashes amb
where a flas
respective a
detection a
flashes toget
d an intermit
anatory, whe
n indicator.
etected.
a couple of s
re discussing
to operate.
xtinguishing
d panel but
omponents:
ainst the ceil
arm horn wi
ber when sm
shing amber
rea (fwd. or
s you can tes
ther with a fl
tent horn is
en a FAULT is
subjects in th
g fire detecti
system. In so
mostly there
ling of the la
ill sound whe
oke is detect
Master Call
aft).
st the system
lashing locat
sound throu
s detected d
hat
on &
ome 73’s
e is no
vatory. It
en
ted.
Light
m here
ter light
ugh the
uring a
