sealantsis two hoursat75 ° Fahrenheitand50 percentrelativehumidity.Forevery10
temperaturerise,applicationlife is reducedin half;for every10° drop intemperature, applicationlife isdoubled. Increasedhumiditydecreasesapplicationlife,anddecreased humidityincreasesapplicationlife.
°
The applicationlifeof A-1/2classsealantis 1/2 hourunderthe same75 Fahrenheitand
50 percentrelativehumidity.
NOTE: Usecarewhenmixingsealantto avoidgettingair intothe sealant.
EFFECTIVITY:
51-20-00
Jan10/90
PIPER AIRCRAFT
PA-42-720(Advanced Trainer)
MAINTENANCEMANUAL
A. Processes (continued)
1. Sealing Procedures (continued)
(b) FuselageSealing (continued)
(3.) List of Equipment (Figures 201 and 202)
(a.) Mixers -Semco No. 285 Portable, orSemco No. 385 Automaticor equivalent. (b.) Cartridges -SemKit No. 650 2 1/2 ounces and 6 ounces proportioned with MIL-S-
7502 or MIL-S-8802 ClassB sealants only. (c.) Half pint kits of MIL-S-7502 or MIL-S-8802 Class A sealants only (5 fluid ounces). (d.) Air powered sealant gun (Semco No. 250-6 with extra retainers for 2 1/2 ounce
cartridgesor equivalents). (e.) Assorted nozzles for sealant gun. (f.) Extension for sealant gun. (g.) Solvent dispensers (polyethylenesquirt bottles). (h.) Clean, white, cotton cloths. (i.) Stiff bristle brush (not nylon). (j.) Solvent containerswith covers for cleaning nozzles,tools, etc. (k.) Fillet fairing tools. (Refer to 91-00-00.)
NOTE: Equipmentlisted is commercially available from vendors shown in the List of ConsumableMaterials,91-00-00.
(4.) List of Materials (Figures 201and 202)
Only the following materials are to be used:
(a.) Sealants -MIL-S-7502 or MIL-S-8802 -Classes A-1/2, A-2, B-2, B-4, B-6, and B-8.
(b.) Sealant material-3M -E.C. 1239.
(c.) Sealant material-G.E.-SS-4404 Primer.
(d.) Sealant material -G.E. RTV 88 with RTV 9811 catalysts.
(e.) Sealant material -PRC -PR 1422 (MIL-S-8802) and PR 1221 (MIL-S-7502).
(f.) Aluminum Wool -Fine.
(g.) Release Agent -Polyvinyl Alcohol.(PVA.)
(h.) Cleaning Solvents -Methylethylketone (MEK) or Aliphatic Naphtha.
NOTE: Materialslisted are commercially from vendors shownin the List of
available ConsumableMaterials,91-00-00.
(5.) Sealant Application(Figures 201 and 202)
Thefollowingsequenceof sealing must be observed:
(a.) Seal faying surfaces of assemblies prior to installation,
andsub-assemblies whichare
not accessible later.
(b.) Seal joggles, holes, cutout, and any other gaps.
(c.) Seal remaining seamsand joints.
(d.) Seal bolts, screws, nuts, and other fasteners.
(e.) Seal electrical harness.
(f.) Seal formed in place gaskets.
NOTE: All sealing is done on the pressure sideof the seal plane. This assures the pressurewill help hold seal in place.
EFFECTIVITY: 040-999
Jan 10/9051-20-00
PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCE MANUAL
A. Processes(continued)
1. SealingProcedures (continued)
(b) Fuselage Sealing (Figures 201 and 202) (continued)
(6.) Sealing Faying Surfaces (Figure 203)
Typical parts requiring sealing prior to assembly are bulkhead stations extending beyond the seal plane, between bulkhead stations 57.0 and 332.0 inclusive, angles and skin joints behind box bulkheads, stringers, windshields, and windows.
NOTE: The PA-42-720 floor panels are not sealed, but are within the pressure vessel.
Type B-2 class sealant must be used. Apply a liberal amount of sealant to each mating surface of the applicable parts. Assemble and secure components together before sealantdries. If specific components require riveting, the components must be riveted together while sealant is still wet. If permanent fastening is not possible at the time, temporary fasteners must be used in at least 50% of the holes to be riveted.
NOTE: Sufficient sealant must be applied to ensure a continuous extrusion on both sides of the joint after assembly of the faying surface. (Figure 203) Permanent fastening is required before work life of sealant has expired. A sand blasted bucking bar must be used to perform the riveting operation.
Allow class B-2 sealant to fully cure for 48 hours at 75°F and 50% relative humidity.
(7.) Sealing Joggles (Figure 204)
Seal joggles by completely filling them with class B-2 sealant. Apply sealant with a pressure applicator, forcing the sealant under the joggle from either side until it begins extruding on the opposite side of the joggle.
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