DESCRIPTION
4.1. BACKGROUND OF THE INVENTION
DO-228 aircraft fleet was installed with existing antennae system on both sides of
fuselage for one of the role modifications. Further a requirement was raised by system
operator to enhance the capability of the existing antennae system.
Feasibility study for installation of antennae of the upgraded system on DO-228 aircraft
was carried out. Location of antennae decided based on aerodynamic performance and
physical location of antennae on aircraft. Location of antennae was cautiously decided to
have minimum effect on Horizontal Stabilizer. .
Installations of antennae on both sides of the fuselage skin result in considerable amount
of protrusion outsides the aircraft due their sizes. These protrusions outsides the aircraft
fuselage skin were creating drag forces which affect the aircraft performance and
handling qualities. To minimize the drag forces an optimum mounting structure and a
composite fairing cover was designed & developed.
3D CAD model of DO-228 aircraft installed with antennae with faring cover was used for
carrying out aerodynamic analysis with the help of computational fluid dynamics software
to access the aircraft performance and handling qualities. The results of the aerodynamic
parameters obtained after analysis were found within the acceptable limits.
Accordingly, mounting Structure was designed and developed to integrate the antennae
on both sides of the fuselage of the aircraft. Stress analysis and optimization was carried
out to finalize the thickness of mounting structure & to validate the structural integrity.
The designed mounting structure is capable to withstand aerodynamic loads, inertia loads
due to antennae weight & bending loads generated by the antennae for continued
airworthiness of aircraft.
4.2 DESCRIPTION FOR INTEGRATION OF ANTENNAE FOR ROLE MODIFIFCATIONS:
Following main parts are required to integrate the antennae for one of the role modifications.
Item 1: Composite fairing
Item 2: Antennae
Item 3: Mounting structure
Item 4: Horizontal Channel
Item 5: Curved channel
tern 6: C channel cleats
tern 7: Doubler plate
Item 8: Existing Stringer
tern 9: Existing Frames
tern 10: Additional angles & stringers
tem11: fuselage skin
BRIEF DESCRIPTION OF THE DRAWINGS:
Fig. 1: Antennae with aircraft skin
Fig. 2: Cross section of Fig. 1
Fig. 3: Isometric view (Antennae hide for clarity)
Fig. 4: Wireframe view of Fig.1
Fig. 5: Isometric view of Mounting Structure.
Fig. 6: Sectional Isometric view of Mounting Structure.
Two quantities of Item 2 is installed on both sides of fuselage skin. Item 3 is a mounting
structure consisting of channel sections item 4, 5 and 6 as shown in Fig. - 5 & 6. Item 3 acts
as an adapter structure for installing item 2. Item 1 is used to avoid abrupt protrusion and
provide smooth aerodynamic shape.
Item 1 is used to provide aerodynamic shape to antennae mounting assembly and protect
antennae from ingression of rainwater, moisture etc. To reduce the weight, Item 1 is made
of glass fiber composite material which is light in weight and aerodynamically designed
fairing installed on both sides of fuselage skin results in reduction of drag/sides forces.
Item 1 is designed & developed with required number of layers, orientation & sufficient
thickness to sustain the drag/sides force.
The mounting structure is designed in such a way that antennae installation and removal is
being done from outsides of the aircraft, this facilitates quick and easy installation and
removal of antennae. The. fairing is designed in such a way that antennae can be installed
and removed without removing fairing.
Top face of item 2 is connected to item 1 with required numbers of fasteners and bottom
face of item 2 is connected to reinforced backup structure of aircraft with required number of
fasteners to sustain & distribute the inertia / aerodynamic loads. Two numbers of item 4 is
connected to two numbers of item 5 using four numbers of item 6 attached with required
number of fasteners to manufacture mounting structure as shown in Fig.-6.
Item 2 is attached with item 10 & aircraft skin. Item 2 is connected to aircraft structure with
item 8 & item 9 to distribute & sustain the aerodynamic loads. Item 3 to 11 are made of high
strength to weight ratio alloy materials.
4.3 OBJECT OF THE INVENTION
Object of the present invention is to design & develop an airworthy mounting
structure to integrate the antennae for one of the role modification on both sides of
fuselage skin on DO-228 aircraft without affecting the structural integrity,
performance & stability of the aircraft for the flight envelope loads and to have
continued airworthiness of aircraft.
4.4 SUMMARY OF THE INVENTION
To install the antennae on both sides of the fuselage skin on DO-228 aircraft, the
mounting structure is design & develop in such a way that it transfer the
aerodynamic and inertia loads of antennae to the aircraft structure.
The existing structure of aircraft where antennae being mounted is locally
reinforced. Since antennae is installed outsides the aircraft structure, a protrusion
was created which was causing large amount of drag force and affecting the
aircraft performance and handling qualities. A composite fairing is designed &
developed to cover the surrounding area of the antennae and to provide
aerodynamic shape outsides the antennae which streamlines the flow.

CLAIMS:
We Claim that,
1. Antennae for one of the role modifications are required to install on both sides of
fuselage on DO-228 aircraft consists of mounting structure, composite fairing,
doubler plate and auxiliary stringers. These structures are designed and developed
by TARDC, HAL Kanpur.
2. The Antennae as defined in claim 1, wherein location of antennae is decided based
on to have minimum effect on aircraft performance and handling qualities.
3. The mounting structure as defined in claim 1, wherein the protrusion of antennae
from the fuselage skin is kept minimum by optimum designing of the mounting
structure.
4. The composite fairing as defined in claim 1, wherein it is having aerodynamic shape
and designed with sufficient number of glass layers, thickness and orientation to
sustain the aerodynamic loads for structural integrity.
5. The mounting structure as defined in claim 1, wherein it is designed in such a way
that installation and removal of antennae is being done from outsides of the aircraft.
6. The composite fairing as defined in claim 1, wherein it is designed in such a way
that antennae can be installed and removed without removing fairing.