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stored accumulator pressure for brake application.
2. Nose Landing Gear Wheels And Tires
The nose landing gear has dual wheels. Each wheel is 22 x 6.6 inches and made
of two forged aluminum halves. The two wheel halves are mated together by eight
bolts, with the inner joint fitted with an O-ring seal, forming an airtight structure for
mounting tubeless tires. The tires are 21 x 7.25 -10 rated at 182 knots for aircraft
S/N 1000-1213 (except S/N 1183) without ASC 190 installed. For aircraft 1214
and subsequent, and S/N 1000-1213 with ASC 190, the nose wheel tire speed
rating is 195 knots. For more information concerning nose wheel tire and wheel
selection, see GIV Illustrated Parts Catalog section 32.
3. Main Landing Gear Wheels and Tires
Each main landing gear has dual wheels. The wheels are forged aluminum with a
removable flange to facilitate tire servicing. The flange is mated to the wheel with
an O-ring that provides and airtight seal for the tubeless tires. Each wheel is
mounted to the landing gear axle with two tapered roller bearings. A brake
assembly is integrated into the wheel, fitting into the space between the bearing
housing and inside wheel rim.
S/Ns 1000 through 1213 (except 1183) have wheels and brakes manufactured by
ABS, and Goodyear 34 x 9.25-16, 18 ply rating, type VII tires, speed rated at 182
knots. Aircraft in this production sequence may be retrofitted with ASC 190 that
increases tire speed rating to 195 knots, and / or with ASC 266 that installs Dunlop
wheels, brakes and tires that provide increased braking capability. On aircraft S/N
1214 and subsequent, Dunlop wheels, brakes and tires are production installed,
supporting higher aircraft gross weights and consequent higher tire speeds. The
OPERATING MANUAL
PRODUCTION AIRCRAFT SYSTEMS 2A-32-00
Page 31
January 31/02
Revision 6
Dunlop wheels have a greater radius between the bearing housing and the inside
of the wheel hub to accommodate the larger braking package. This requires a
lower profile tire, measuring 34 x 9.25-18, in order for the tire and wheel
combination to fit into the wheel wells.
ABS wheels have three fusible plugs that melt at 430°F, releasing tire pressure if
the wheel overheats. Dunlop wheels have four fusible plugs that melt at 390°F
and a wheel safety plug that will deflate the tire if pressure reaches 375 - 650 psi.
4. Brake Assemblies
Brakes manufactured by ABS have four rotating discs (rotors) three stationary
discs (stators) an end plate and a pressure plate. See Figure 12 for an illustration
of an ABS brake. All of these elements are composed of carbon-metallic alloy, and
are referred to as a whole as the disc stack or heat pack. The stators are attached
to the torque tube that in turn is bolted to the aircraft gear assembly and holds the
wheel bearings. The rotors are attached to the wheel, with notches in the rotors
fitting keys on the interior of the wheel hub. The wheel with attached rotors turns
on the wheel bearing, with the rotors spinning between the brake stators. Brake
bolts attached at the brake housing and fastened to the outside of the end plate
maintain sufficient clearance between the rotors and the stators to permit the
wheels to turn freely. Five hydraulic actuating pistons are built in the brake
housing. When the brakes are applied, hydraulic pressure is applied to the pistons
that then move outward from the housing squeezing the pressure plate, and
reducing the clearance between the rotors and stators. The surfaces of the rotors
and stators are pressed against each other, producing the friction that slows the
spinning wheel.
Dunlop brakes have three rotors, two inner stators of double thickness, and a
stator of single thickness at the pressure plate and the end plate. The components
of a Dunlop brake are shown in Figure 13. Operation of the Dunlop brakes is
similar to that of the ABS brakes, but because of the greater energy absorbing
mass afforded by the increased diameter of the wheel and resulting larger surface
area of the rotors and stators, a higher breaking efficiency is attained.
Both brake types have provisions for brake temperature monitoring, anti-skid
protection, and application of hydraulic pressure at a reduced level (400 ± 50 psi)
to stop wheel spin as the landing gear are retracted into the wheel well.
2A-32-41: Hydro-Mechanical Analog Braking (HMAB) System
1. General Description
The Hydro-Mechanical Analog Braking (HMAB) system is installed on aircraft S/N
1214 and subsequent, and is available for retrofit on aircraft S/N 1000 through
1213 with the installation of ASC 307. The HMAB system applies up to 3000 psi
hydraulic pressure from the Combined system to the main landing gear brakes in
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湾流4操作手册 Gulfstream IV Operating Manual 2(83)
