Thermal
and fire protection for aircraft engine reversers.
According to FAA
fireproofing regulations, commercial engine cowlings must be capable
of withstanding a fuel-fed flame of 2000oF for fifteen
minutes without flame penetration. To meet this requirement, there
are two approved spray-on coatings, MA-25 S and 64-C1-2. For some
time, many in the industry have been aware of reverser core failures
resulting in heat induced degradation going unnoticed under spray-on
coatings.
Hi-Temp
Insulation provides removable reverser insulation blankets for CF6-6,
CF6-50 and CF6-80 engine series. Each insulation blanket performs
as a fireproof barrier in accordance with FAR 25.1191. The blanket
tests were conducted in compliance with the criteria and requirements
set forth in Federal Aviation Administration Advisory Circular AC
20-135. The insulation blankets prevent a burn through and/or backside
ignition for a minimum of fifteen minutes.
Following is a list
of the advantages removable insulation blankets offer over spray-on
coatings. Many of these advantages where detailed in an article written
for Aerospace Engineering by Paul Romnes, Engine Technical
Services Maintenance Operations, United Airlines, San Francisco, CA.
Environmental:
Elimination
of toxic emissions during the surface preparation and spray-on
application of ablative insulation coatings.- Elimination of disposal problems
associated with the coatings when removed for inspection and with
the chemicals used during removal of the coatings.
- Elimination of special training
and handling.
- Elimination of special purpose
spray containment facilities.
Fit:
- Blankets are manufactured
to tool controlled tolerances.
- Blankets are configured to
pan down in specific areas to improve fit and avoid interference
problems.
- Blankets are designed around
areas where insulation is not required, rather than applying a
coating to the entire area, reducing overall weight.
- Mechanical fasteners are
used to precisely position and positively retain the blankets
in place.
Consistency:
- Blankets are not affected
by high vibration levels of an in-flight environment that can
cause fragile coatings to disintegrate.
- Blankets are fabricated to
tool-controlled dimensions.
- Blanket thickness is controlled
by both quilting the insulation core and heat curing the final
lay-up under vacuum.
- Blanket thermal efficiency
is superior to coatings, and remains consistent due to controlled
thickness and improved durability.
Durability:
- Blankets are not as easily
damaged as coatings during maintenance.
- Blankets are more resistant
to typical aircraft contaminants than coatings.
- Blankets do not require top
coats like those used as a binder for coatings.
Maintainability:
- Blankets are easily repaired.
- Blanket repair can be done
"on-wing".
- Blankets are easily removed
and reinstalled for fan reverser inspections.
Inspections:
- Reverser bond lines, between
the hot-side surface and the honeycomb core, can be inspected
more frequently due to improved accessibility.
- With improved accessibility,
a more reliable "tap test" and visual inspection can
be performed.
- Reversers require less repair
time since coatings are not being removed and re-applied.
Cost:
- Blankets last the life of
the reverser under normal conditions.
- Maintenance costs are reduced
compared to removing and re-applying coatings.
- Costly special handling,
needed to use the highly toxic components of the coatings, is
eliminated.
- Products related to the coatings,
that have a limited shelf life and must be stored, are eliminated.
- Maintenance downtime for
reverser removal and reinstallation, is reduced from ten days
for coatings, to less than twelve hours for blankets.
|
Drawing Number
|
Application
|
Engine Model
|
Service Bulletin
|
Repair Specification
|
|
46M1015-301
|
MDC Left Hand
|
CF6-6
|
S/B 78-2011
|
33DOC0009
|
|
46M1016-301
|
MDC Right Hand
|
CF6-6
|
S/B 78-2011
|
33DOC0009
|
|
46M1019-301
|
MDC Left Hand
|
CF6-50
|
S/B 78-3012
|
33DOC0009
|
|
46M1020-301
|
MDC Right Hand
|
CF6-50
|
S/B 78-3012
|
33DOC0009
|
|
46M1035-301
|
BAC Left Hand
|
CF6-80C2
|
S/B 78-1045
|
33DOC0051
|
|
46M1036-301
|
BAC Right Hand
|
CF6-80C2
|
S/B 78-1045
|
33DOC0051
|
|
46M1035-303
|
ABI Left Hand
|
CF6-80C2
|
S/B TBD
|
33DOC0051
|
|
46M1036-303
|
ABI Right Hand
|
CF6-80C2
|
S/B TBD
|
33DOC0051
|
|
46M1035-303
|
MDC Left Hand
|
CF6-80C2
|
S/B TBD
|
33DOC0051
|
|
46M1036-303
|
MDC Right Hand
|
CF6-80C2
|
S/B TBD
|
33DOC0051
|
|
46M1039-301
|
ABI Left Hand
|
CF6-80E
|
S/B TBD
|
33DOC0051
|
|
46M1040-301
|
ABI Right Hand
|
CF6-80E
|
S/B TBD
|
33DOC0051
|
|
46M1043-301
|
ABI Left Hand
|
CF6-80A
|
S/B TBD
|
33DOC0051
|
|
46M1044-301
|
ABI Right Hand
|
CF6-80A
|
S/B TBD
|
33DOC0051
|
Back
Prev
| Next
