INSPECTION SERVICE BULLETIN
BAe 146 SERIES/AVRO 146‑RJ
SERIES AIRCRAFT
MANDATORY
ISB.21-1156
CAA #003-10-2002
TITLE : AIR
CONDITIONING ‑ TO INSPECT AIR CONDITIONING
SOUND‑ATTENUATING DUCTS FOR SIGNS OF OIL
CONTAMINATION.
1. Planning information
A.Effectivity
Aircraft
Aircraft affected by this
inspection are defined below:
The inspection applies to aircraft
with the cabin air
filtration system fitted
(Modifications HCM01316A or
HCM013168)
and also to aircraft without the cabin air
filtration
system fitted.
B.Reason
Incidents have been reported involving impaired
performance of the
flight crew. Investigations have been conducted to
determine
whether the events could have been caused by
inhalation of an
agent(s) resulting from oil and/or oil breakdown
products leaking
from the engine(s) or APU and contaminating the
environmental
control system. At this time, there is no
substantiated evidence
indicating that oil breakdown products can impair
crew
performance.
In the past, oil leaks and cabin/flight deck odours
and fumes may
have come to be regarded as a nuisance rather than a
potential
flight safety issue
However whilst investigations are
being carried out to determine
the nature of any agents that may
be released into the cabin
environment and to define any
necessary corrective actions, oil
leaks and cabin/flight deck odours
must be regarded as a potential
threat to flight safety, they
should not be dismissed as a mere
nuisance and should be addressed
as soon as possible.
Mandatory Inspection Bulletin
ISB.21 –150 was issued in April 2001
to inspect the engine oil seals,
the APU and the ECS jet pumps and
air conditioning packs for signs
of oil contamination. Following
further investigations of cabin
air quality complaints by BAE
SYSTEMS, this ISB is intended to
supplement the ISB.21‑150 by
extending the areas inspected to
include the sound attenuating
ducting downstream of the packs
under the rear cabin floor, either
side of the mixing chamber
duct/filter housing. It has been shown
by recent inspection of in‑service
aircraft that sound attenuating
material within these ducts has
acted as an absorbent for oil
contamination on some aircraft.
This ISB does not replace ISB.21‑150, it must
be complied with in
addition to ISB.21‑150. Note that both this ISB
and ISB.21‑150
contain feedback forms for each operator to inform
BAE SYSTEMS of
the findings, and this feedback is required, even
when no
contamination has been found. These feedback results
are used by
BAE SYSTEMS in conjunction with the Airworthiness
Authority to
determine the periodicity of any inspections. Failure
to return
the feedback forms, including those forms which show
‘no
contamination', constitutes a non‑compliance
with the associated
Airworthiness Directives. Failure to return the
feedback forms
also results in BAE SYSTEMS having incomplete data of
the
cleanliness state of the fleet, which hampers
negotiations with
the airworthiness authorities to extend the
inspection period.
C.Description
(1) Inspection of the inside of
each of the four air conditioning
sound‑attenuating
ducts for the presence of oil contamination.
NOTE: Flight
crews should be reminded of the importance of
donning oxygen masks‑if
poor cabin air quality is
suspected, and reminded of
the importance of reporting
smoke or smells as a
technical defect (ref. AOM
00/030V).
D.Compliance
The actions generated by this
Inspection Service Bulletin are
classified as MANDATORY by the
U.K. C.A.A.
(1) Effective 30 November 2002, at the next
"A" check or within a
maximum of 500 flights and
repeated at every subsequent "C"
check, inspect and rectify in
accordance with para 2 of this
ISB.
(2) Notwithstanding the frequency of
inspection required by this
ISB, operators are reminded that
if a persistent air quality
problem is reported at any time,
which is suspected of being
caused by oil contamination of the
air conditioning system,
these ducts should be inspected
and rectified in accordance
with para 2 of this ISB.
E.Approval
The technical information
contained in this document has been
approved under the authority of
JAA Design Organization Approval
No.CAA.JA.02034.
F.Manpower
(1) To inspect as defined
in para 2.A ‑ 5 man‑hours.
G.Materials ‑ cost and availability
Cost and Availability is by
arrangement between the Operator and BAE SYSTEMS.
H.Tooling ‑ cost and availability
Cost and Availability is by
arrangement between the Operator and BAE SYSTEMS.
I.Weight and balance
No Effect.
J.References
Aircraft Maintenance Manual
AMM 06‑04‑00, 12‑10‑24, 21‑09‑11,
23‑71‑24, 31‑31‑27
ALL Operator Message AOM
00/030V
K.Publications affected
None.
L.Electrical load data
Not applicable.
2.Accomplishment instructions
A.GENERAL
The inspection procedures outlined in this ISB
address problems
caused by oil contamination of the air distribution
system from
the air conditioning system. It is imperative that
the source of
oil is identified.
Mandatory ISB.21‑150 addresses problems caused
by oil
contamination to the air conditioning system, in
particular oil
contamination in the air conditioning pack
regenerative air ducts
and air cycle machine, inspection of engine and APU
for oil leaks
and inspection of the APU bay for contamination.
If a report of poor cabin air quality which is
associated with oil
contamination of the air distribution supply from the
air
conditioning system is made at an airfield where the
inspections
described in this section cannot be accomplished, it
is
permissible at the discretion of the flight crew with
due
consideration to the nature of the event to continue
operation
for the rest of the day, in order to get the aircraft
to a suitable
airfield where these inspections and rectification
actions can be
conducted
NOTE: Flight crews should be reminded of the
importance of donning
oxygen masks if poor cabin
air quality is suspected, and
reminded of the importance
of reporting smoke or smells as a
technical defect (Ref. AOM
00/030V).
This ISB requires inspection and rectification if
necessary of the
sound attenuating ducts that supply air to the mixing
chamber duct
and route air from the mixing chamber duct. For
aircraft with the
air filtration system installed (Mods HCM01316A or
HCM01316B), the
filter housing is fitted in place of the mixing
chamber duct. The
mixing chamber duct/filter housing is Located in a
central position
beneath the rear vestibule/cabin floor between Frames
40 and 42.
The part numbers of the affected ducts are dependant
upon the
optional Modification configuration of the aircraft:
Port Side, upstream of
mixing chamber duct/filter housing:
XC5341 duct with ram air system installed
XC5349 duct with no ram air system
X6588 duct
with flight deck boost system installed
Starboard Side, upstream of
mixing chamber duct/filter housing:
XC5348 duct with no ground conditioning system
installed
XC5423 duct with ground conditioning system installed
Port and starboard side, downstream of mixing chamber duct /
filter housing:
XB5283 duct
These ducts are all silencer ducts with a silicone
flexible outer
skin and a porous inner flexible skin, the area
between the skins
is filled with a glass fibre sound attenuating
absorber. It is not
possible to effectively clean the duct owing to the
porous nature
of the glass fibre material.
WARNING HYDRAULICS: PRIOR TO ENERGISING OR DE‑ENERGIZING
AIRCRAFT
ELECTRICAL BUSBARS:
MAKE CERTAIN:
‑ GROUND SAFETIES ARE IN POSITION.
‑ ALL PERSONNEL ARE CLEAR OF HYDRAULICALLY
ACTUATED SURFACES.
‑ CONTROL LEVERS MATCH THEIR RELEVANT
COMPONENT POSITIONS.
‑ TRAVEL RANGE OF HYDRAULICALLY ACTUATED
SURFACES IS UNOBSTRUCTED.
‑ Observe all WARNINGS and CAUTIONS appearing
in the Aircraft
Maintenance Manual (AMM) referred to in
this Inspection Service
Bulletin.
B.Inspection
of sound attenuating ducts and mixing chamber duct in
air conditioning
distribution system
(1) Display
warning notices on flight deck prohibiting the use of air conditioning.
(2) Open rear cargo compartment
door (818)
(3) In rear cargo compartment,
refer to Aircraft Maintenance Manual
AMM 06‑04‑00 remove
and retain access panels 181HL and 182HR.
(4) If necessary, refer to
Aircraft Maintenance Manual AMM 31‑31‑27
remove and retain Flight Data Recorder and Cockpit Voice Recorder
AMM 23‑71‑24 .
(5) For each of the two sound
attenuating ducts connecting from the rear
pressure bulkhead to the mixing chamber duct
or filter housing:
(a)
release and retain clamps from rear pressure dome connector
and
sound attenuating duct OR release and
retain clamps from mixing
chamber duct/filter housing and sound
attenuating duct if this is
more accessible
(b)
pull sound attenuating duct away from dome connector or
chamber/
housing and inspect interior of sound
attenuating duct for contamination.
For page 7 through 14 see
hard copy of BRITISH AEROSPACE CAA MANDATORY
SERVICE BULLETIN ISB.21-156
dated Oct 31/02.