B737-6/7/8/9 Proximity Switch Electronics Unit
(PSEU) Part Nm!er
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%4 ntro5ction This lesson covers the upgrade of the Proximity Switch Electronic Unit (PSEU) to a version which has an improved BITE menu structure and etter handling capaility of certain fault setting conditions! The main reason for upgrade from the "# PSEU to the "$ PSEU is the incorporation of the %ain &ec' argo &oor installation! This configuration uses special features in the "$ PSEU! Some airlines have chosen for this option! In the *% fleet all %&& functions are not used! +lso there were a numer of software and hardware improvement made in the "$ PSEU! Some of these improvements were made ecause of nuisance PSEU indications on the P, panel after ground power was put on the transfer usses! These nuisance PSEU indications were responsile for numerous dispatch delays!
"4 B6&&/7&&/8&&/9&& Proximity Switch Electronics Unit Prose The proximity switch electronics unit (PSEU) does these functions for the air-ground system. Κ %onitors
the landing gear compressed sensors!
Κ /perates
the air-ground relays!
Κ Sends
air-ground discrete signals!
1ocation The PSEU is in the forward e0uipment compartment! 1ou get access to the PSEU through the access door on the ottom on the airplane2 forward of the nose landing gear wheel well!
Physical .nctional *escrition The PSEU is an *3U with two internal circuit cards and a BITE panel on the front! Two red lights elow the BITE panel show if the air-ground systems are in the air mode! + placard on the front of the PSEU has instructions to operate the BITE!
The PSEU processes signals from the air-ground sensors and sends air-ground signals to airplane systems and air-ground relays! The PSEU also does these functions. Κ *anding
gear position indication!
Κ *anding
gear transfer valve control
Κ *anding
gear not down warning!
Κ Ta'eoff
(aural) warning!
Κ &oor
warning!
Κ SPEE&B3+ES
E4TE5&E& amer light control!
34 PSEU B'E ntro5ction 0eneral The PSEU can help you find and isolate a fault in the systems that the PSEU monitors and controls! 6ront panel BITE on the PSEU lets you interface with the BITE functions in the PSEU! The BITE does not operate when the forward access door is closed!
.alt n5ication The PSEU amer light on the P, aft overhead panel comes on when a no7dispatch type of fault is stored in the memory of the PSEU! The light comes on when these occur. Κ +irplane
on the ground!
Κ Both
thrust levers less than ,$ degrees!
Κ %ore
than $8 seconds after landing!
The /9E3:E+& light on the right master caution system annunciator and the master caution lights come on when the PSEU light comes on! The PSEU light also comes on when you push either master caution system annunciator if a dispatchale fault is stored in the memory of the PSEU! The PSEU then goes off when you push the master caution light!
4 PSEU B'E en See PSEU 7# %enu! See PSEU 7$ %enu! These are the items in the main menu of the PSEU BITE. Κ E4ISTI5; Κ 6+U*T
:IST/31!
Κ ;3/U5&
TESTS!
Κ +I3-;5& Κ /T:E3
6+U*TS!
/93&!
6U5TI/5S!
If the access door to the forward e0uipment compartment is closed when you push the /5-/66 switch2 the message TEST I5:IBIT shows instead of E4ISTI5; 6+U*TS!
ES'N0 .$U1'S The E4ISTI5; 6+U*TS selection does a chec' of the interfaces to the PSEU and the inside of the PSEU! It also lets you reset latches in the PSEU!
.$U1' S'+2 The 6+U*T :IST/31 selection shows fault information that is in the non7volatile memory (59%) in the PSEU!
0+UN* 'ES'S The ;3/U5& TESTS selection lets you do these tests. Κ *3U
replacement test!
Κ PSEU
self test!
Κ *anding
gear transfer valve test!
Κ SPEE&B3+ES Κ Ta'eoff Κ PSEU
E4TE5&E& light operation test!
warning test!
BITE display test!
$/0N* +:* The +I3-;5& /93& selection lets you change the air-ground outputs from the PSEU!
+'E .UN,'+NS The /T:E3 6U5TI/5S selection lets you do these functions. Κ Ta'eoff
warning report!
Κ *anding
gear transfer valve report!
Κ Sensor
3igging menu!
Κ %onitor Κ *3U
PSEU inputs and outputs!
onfiguration!
#4 "8#$%6&&-" to "8#$%6&&-3 *i;;erences Part Nm!er *i;;erences The partnumer changes from #<,+=>887# to #<,+=>887$! The #<,+=>887# and #<,+=>887$ are completely #<,+=>887$ may e replaced with a #<,+=>887#!
interchangeale!
+
The #<,+=>887$ will ecome standard for all new production! +irlines will e encouraged to update all #<,+=>887#s to #<,+=>887 $s to ta'e advantage of improved maintenance features! The *% fleet will e (retro)fitted with the "$ PSEU!
1U +887# Κ /ther
of the #<,+=>887# with the #<,+=>887$!
to #<,+=>887$ &ifferences!
functional revisions!
Κ 3evisions
to BITE ontrol Panel %enus!
Κ 3evisions
to PSEU I-/2 reported faults2 and fault setting conditions!
Κ BITE
ontrol Panel installation modifications!
64 +ther ;nctional re7$ is moved from the #<9& us Section = to the & ;round Service us y Boeing Service Bulletin! The argo *oading System is often used when the aircraft is on ;round Service! The PSEU is not powered in that situation2 ut the PSEU &oor @arning logic is needed y the argo *oading System to operate! To resolve the prolem the PSEU circuitrea'er is put on another & source2 which is always powered when the aircraft is on ;round Service! 5ow the PSEU is also operational when the aircraft is on ;round Service!
'a>eo;; warnin= ;nction +dded a test of the ta'eoff warning output initiated within $8s of an air7to7ground transition to verify valid output hardware!
Power- test o; o relays eliminate5 In service history showed nuisance faults could e generated which resulted in PSEU light indications that prevented immediate dispatch depending on airline7specific maintenance power up procedures! Test remains as part of *3U 3eplacement test!
Eliminate5 lan5in= =ear in5ication con;i=ration otion /riginal PSEU design included option for in7transit gear indication ased on altitude or flap positionA however the only configuration delivered for all $5; airplanes uses altitude software revised so that landing gear indication outputs depend directly on the <88C altitude inputs (+*T *T<88 * and +*T *T<88 3)!
74 e
display in menu shows numer of faults in list!
Κ The
&ISP+T: 6+U*T (message $#7>D88$) and 5/ &ISP+T: 6+U*T (message $#7>D88D) messages have een moved from the top of the message list to the ottom of the message list!
Κ The
details sumenu now ends with a 3ETU35 T/ *IST
Κ 1ES
returns to the fault message!
Κ 5/
returns to E5& /6 *IST 6ault :istory menu!
.alt istory chan=es Κ
6irst display in the flight leg sumenu shows numer of faults in list!
Κ The
details sumenu now ends with a 3ETU35 T/ *IST
Κ 1ES
returns to the fault message!
Κ 5/
returns to E5& /6 *IST!
Sensor i==in= men %enu has een installation!
expanded
to
show
more
information
aout
sensor
5ew sumenu as's operator three 1ES-5/ 0uestions. a 5/ response moves to the next 0uestion2 a 1ES response to ;+P ;3+P: will display. 7 the sensor numer! 7 the same graphical representation position as on the PSEU "#!
of
the
sensor
rigging
a 1ES response to ;+P 9+*UE will display. 7 the sensor numer2 7 the gap distance read y the PSEU in mils. 444 %I*S! a 1ES response to ;+P %/9E 9+*UE will display. 7 the sensor numer2 7 the difference etween the measured gap and the optimum gap in mils. F444mils shows how much the gap must e increased to e0ual the optimum gap2 7444mils shows how much the gap must e decreased to e0ual the optimum gap! If the sensor is target far2 all three displays will show T;T 6+3! There is a toggle etween the ;+P ;3+P: and ;+P %/9E 9+*UE!
The *3U placard has een revised to show the new menu details! The graphical displays have een recalirated to etter match the physical tolerances of the individual sensor installations77there should e no more mismatches etween measured gaps and displayed gaps!
84 +ther B'E .nction chan=es 6ault recording conditions have een modified slightly to reduce the numer of nuisance faults recorded during normal maintenance and manufacturing processes. Κ
internal faults #<,+=>887#!
are
always
recorded77unchanged
from
Κ
faults that occur when fault history recording conditions are not true will appear in the existing faults list while active ut may not e recorded in fault history77unchanged from #<,+=>887#!
Κ
external faults are recorded in fault history if. 7 all eight entry2 service2 and access doors are in their closed or loc'ed positions2 +5& 7 the airplane is not on ground and the air-ground override function is not active!
Κ
The two #<9 power %onitor menu!
inputs
are
now
displayed
on
the
I-/
Κ
The performance of the 1ES and 5/ uttons on the BITE ontrol Panel have een modified for more intuitive and more consistent operation!
94 e pin D to &=8?<# pin = (pins were shorted together in $7>88-88-<88 airplane wiring)! Κ
Κ
+*T *T<88 3 moved from &=8?<> pin =# to &=8?88-88-<88 airplane wiring)! Κ
&=8?
Κ
&=8?
Κ
The #<,+=>887$ has multiple7use inputs2 where the airplane connection to the PSEU depends on airplane model defined y program pin connections!
Κ
for $7<88-?882 &=8?<> pins =,-,#-,$ and &=8?<< pins $8-$,-,# are used for the six switch inputs from the *eft and 3ight 6orward /verwing :atch &oors!
eorte5 .alts 5ew general fault messages Κ
5/SE &5 &IS+;3EE (message $#7>=8=$)!
Κ
*&; 6*+P &IS+;3EE (message $#7>#8=D)!
I59+*I& /PT PI5S (message ,#7#=8,)! &eleted fault messages Κ Κ
3E& E5+B*E + 6+U*T (message $#7>#8=#)!
Κ
3E& E5+B*E B 6+U*T (message $#7>#8=$)!
%&4 e
the set time delays for +*T 5/SE ST32 T/@ I5:IBIT2 ;S9 */SE&2 ST+B T3I% ;3EE5-ST+B T3I% 5/T ;3EE52 *E 6*+PS E4T (stuc' false only) faults were modified to filter out nuisance faults recorded during normal airplane operation! Κ
Κ
the set condition for *@ I5:IBIT2 E5; 3U5 32 and E5; 3U5 * faults were modified to prevent nuisance faults recorded during normal airplane operation! the set and reset conditions for faults of the six inputs from the thrust lever were modified to prevent nuisance faults recorded during simulated engine out conditions! Κ
Κ
the stuc' false conditions for T+E/66 6*+PS + and T+E/66 6*+PS B faults were modified to prevent nuisance faults recorded under certain landing conditions (flaps extended eyond the ta'eoff flaps setting and advanced thrust settings)! Κ
the set condition for the *;T9 SET fault was modified to eliminate nuisance faults logged during simulated engine out conditions on B= flights! Κ
the set conditions for all landing gear up and loc'ed faults and landing gear down and loc'ed faults were modified to account for an alternate gear extension procedure that allows the gear to e extended one gear at a time during chec'out flights!
Nisance .alts 5rin= Power- 'est 6aults generated y the power7up test of the &ISP+T: 6+U*T2 5/ &ISP+T: 6+U*T2 overwing door warning2 and main dec' cargo door warning outputs are now cleared under certain conditions to prevent nuisance fault history records generated during maintenance actions when only dc us power is active!
+ther .alt Settin= ,on5itions 6aults associated with the hydraulic 0uantity reclassified from nondispatchale to dispatchale!
inputs
were
%%4 1istin= Sensors
o;
.$U1'
essa=es?
/+?
,onnectors
PSEU ;alt messa=es ;or !oth "8#$%6&&-" an5 "8#$%6&&-3 See PSEU 7# 6ault messages documentation! See PSEU 7$ 6ault messages documentation!
essa=e entry in;ormation Κ
message numer!
Κ
fault message on display!
Κ
connecting airplane e0uipment numer!
Κ
conditions and tests under which the fault can e set!
nt/ott n;ormation Κ
input-output name!
Κ
airplane connector numer and pin numer!
Κ
e0uipment numer of airplane connection!
Sensor n;ormation Κ
full sensor name!
Κ
displayed sensor name!
Κ
airplane e0uipment numer!
,onnector n;ormation correlates with $irlane E@iment 5umer &GGGGG with PSEU connector numers HG!
an5
%"4 .ront Panel lacar5 re
,omarison -"
%34 B'E ,ontrol Panel installation mo5i;ications ntro5ction The maority of the delivery and in7service prolems with the PSEU are related to its uni0ue installation of the BITE ontrol Panel! + series of minor optional modifications have een designed and incorporated into production units in se0uence! +ll optional modifications to the #<,+=>887# installation will e re0uired for the #<,+=>887$ Installation!
o5i;ications These modifications are. Κ
the #<,+=>8$7#< gas'et installed etween the top cover and the BITE ontrol Panel was removed to allow visual alignment chec'ing during installation and to reduce pin ending!
Κ
a custom header was designed to interface the oard7mounted soc'et with the BITE ontrol Panel to reduce module7to7 oard intermittent electrical pin connections!
Κ
the washers that control the standoff height etween the System # circuit oard and the BITE ontrol Panel were adusted to reduce the gap and improve electrical pin connections!
Κ
a shoulder washer will replace a regular washer to prevent interference with the components mounted on the System # circuit oard underneath the BITE ontrol Panel chassis recess77there is no interference during normal service and operation2 ut during maintenance the PSEU can e leaned against or stepped on and the cover can e pushed against the circuit oard!
