DESCRIPTION:
4.1 Background of invention:
HS-748 AVRO aircraft is fitted with two main brake assemblies. Each brake assembly has
two discs consisting of 10 rotor segments per disc. The rotor assemblies are each
constructed of jig-saw type segments interlocked with each other to form an annular nonrigid
structure. There are two single and one double stator assemblies on which set of brake
pads are mounted. Due to no-quote of rotor segments from OEM M/S DUNLOP Aerospace
Ltd, UK, the overhaul of brake assembly became difficult. To achieve the availability of brake
assemblies Design, development of rotor segments had been taken up. The details of the
brake assembly is illustrated in Fig.1
Fig 1: Brake Assembly
4.2 Object of the invention:
There was requirement of establishing alternate rotor segments for overhauling the Brake
assembly of HS-748 AVRO aircraft. The rotor segments part no. HF-AHM5780 designed and
developed through DMRL-Hyderabad and HAL, Foundry& Forge Division-Bangalore were
integrated on the brake assembly for fitment trial. Brake assembly was installed on aircraft
and subjected to actual aircraft taxi and landing trials. Segments were qualified and approved
to meet performance requirements on HS-748 AVRO aircraft by HAL, Kanpur.
4.3 Description:
The rotor segment as shown in Fig.2 is manufactured using high strength low alloy steel
specification MDN 127A (0.31C-1.25Cr-0.5Mo-0.25V). The segment profile was
manufactured by fine blanking/ wire cutting process as per blanking drawing no. FBP 1012.
The rotor assemblies as shown in Fig.3 are each constructed of jig-saw type segments
interlocked with each other to form an annular non-rigid structure.
4.4 Qualification tests:
The .prototype samples were fabricated and undergone simulation/ Dynamometer test at
RDSO, Lucknow. After completion of brake dynamometer test, rotor segments were installed
on brake assembly and subjected to actual aircraft taxi and landing trials at HAL, TAD,
Kanpur. Based on satisfactory test results and customer feedback report, item got approved
for use.
4.5 Operation : (Refer Fig 4 for Operation of Automatic Brake Adjuster)
When hydraulic fluid is applied under pressure the pistons move outwards
and apply a direct thrust to the pressure plate which in turn imparts a
clamping force to the stator and rotor assemblies. Thus a retarding force is
obtained by resultant frictional resistance to the rotation of the rotors.
The automatic adjusters return the brake to the "OFF "position when the
hydraulic pressure is released and maintain a preset working clearance
between the stationary and rotary brake components, throughout the full
service life of the pads. When the brake is applied the movement of the
pressure plate is transmitted via the retraction pins and abutment sleeves to
compress the return springs. Spring travel is limited by the abutment of the
sleeve flange against a shoulder in the housing bore. The movement
represents the total working clearance when the brake is "OFF".
The application of hydraulic pressure compresses the return springs to the
limit of their travel, and any further movement necessary to apply the brake
results in the retraction pins being drawn through the friction bushes. As the
pad wear, this withdrawal correspondingly increases so that when hydraulic
pressure is released the return springs withdraw the pressure plate and
pistons only by an amount equivalent to the spring travel. Thus after each
brake application involving brake pad wear, the pistons protrude a little
further from cylinders, thereby leaving only the preset working clearance to
be taken up on the next application.
A. BRAKE OFF
B. BRAKE ON
SPRING COMPRESSED.
SPRING FRICTION P*0 ROTOR
tUSHES .
C BRAKE ON
PIN ORAWN THROUGH
BOSHES AS PAD WEARS.
D. BRAKE OFF
RUSHES MTAIN NEW
LOCATION ON PIN.'.
SPRING WnHORAWS
PAD PROM ROTOR.
Fid 4 Operation of Automatic Brake Adjuster

5.CLAIMS
We Claim that,
1. TARDC, HAL Kanpur has developed the integration of indigenous rotor segments
part No. HF-AHM5780 which meet the form, fit and functional requirement for use on
brake assembly of HS-748 AVRO aircraft.
2. The rotor segments in clause-1 were integrated on the brake assembly, followed by
actual aircraft taxi and landing trials by HAL, TAD, Kanpur. Based on satisfactory test
results and customer feedback report, item was approved for use on HS-748 AVRO
aircraft.