1 Title of the Invention
Process to achieve precision angular holes on Navigation Lamp assemblies
for aircraft.
2 Field of the invention
This invention relates to a sandwich jig that is designed and fabricated for
to provide high precision angular holes within tolerance limits on multi
contour Navigation Lamp assemblies to meet necessary navigation
requirement with interchangeability.
3 Background of the Invention
Navigation Lamp is installed on either side of aircraft on Wing tips.
Navigation Lamp is an assembly that consists of a Navigation Bulb (Red
and Green in Colour), a Navigation Lamp Cover and a Mounting Frame
Bracket. Assembly is in such a way that Navigation Bulb is protected by
Navigation Lamp Cover together installed with Mounting Frame Bracket
over the Navigation Bulb.

Achieving precision angular holes with required tolerance limits between the
Navigation Lamp Cover made up of Cast Acrylic Sheet and Mounting Frame
Bracket made up of Aluminium with multi contour shape is difficult due to its
soft nature and cumulative stack up tolerance errors. Hence, it necessitates
a special drill. jig set up to achieve precision angular holes within tolerance
limits on Navigation Lamp Cover made up .of Cast Acrylic Sheet and
Mounting Bracket to obtain required interchangeability among Aircraft and
avoid crack during assembly and Aircraft Flight loads.
4 Brief Summary of the Invention
In order to achieve precision angular holes with tolerance of H7 (0 to 0.015
mm), a dedicated sandwich jig is designed and fabricated for Navigation
Lamp assemblies with removable locators. This facilitates clamping/holding
by arresting the degrees of freedom while drilling and reaming of holes on
Navigation Lamp cover (1) and Mounting Frame Bracket (2) at 15 places

individually using same Sandwich Drill Template in different setup for
achieving the precision assembly.
5 Detail Description of the Drawings
Figure 1: shows Aircraft (11), Wing Assembly (12) with location of
5 Navigation Lamp (13), Navigation Lamp Cover (1) and Mounting Frame
Bracket (2).
Figure 2: shows Schematic Diagram of Sandwich Drill Jig consists of
Navigation Lamp Cover (1), Drill Template Top (3), Drill Template Bottom
(4), Centre Block (5), removable Locator Pin (6), Nut (7), guide bushes (8)
10 and Stoppers (9).
'
Figure 3: shows mounting frame bracket (2), Drill Template Top (3), Drill
Template (4), Centre Block (10) and removable Locator Pin (6), Nut (7) and
guide bushes (8).
'
Figure 4: shows the Navigation Lamp Cover (1), Drill Template Top (3), Drill
15 Template bottom (4), Centre Block (5) and removable Locator Pin (6) and
Nut (7).
Figure 5: shows Schematic Diagram of Navigation Lamp Assembly consist
of Navigation Lamp cover (1) and Mounting Frame Bracket (2).

6 Detail Description of the Invention
20 Navigation Lamp cover is made up of Cast Acrylic Sheet material and is soft
in nature, prone to get crack during Aircraft flight loads. Also fastening holes
on Navigation Lamp cover to be made with accurate dimension with
required positional tolerance to assemble on its mating part Mounting Frame
with close tolerance of H7 i.e., 0 to 0.015 mm. Any deviation of holes
25 position on Navigation Lamp Cover with its mating part will lead to crack on
Navigation Lamp Cover. Fastening holes on Navigation Lamp and
Mounting Frame to be drilled individually with suitable drill templates to
achieve necessary diameter within tolerance limits.

Figure 2 shows Schematic Diagram of Sandwich Drill Jig which indicates
Navigation Lamp Cover (1), Drill Template Top (3), Drill Template (4),
Centre Block (5), removable Locator Pins with Nut (6, 7) and Stopper (9) on
assembled condition with direction of drilling perpendicular to outer contour
surface. It indicates, all degrees of freedom of Navigation Lamp Cover (1)
are arrested using removal Locator Pins & nut (6, 7) and Stopper (9).
Each of these are assembled together to drill angular holes with in H7 (0 to
0.015 mm) tolerance, which is considered as critical tolerance in
engineering field. Once Navigation Lamp assemblies are installed on
aircraft. It should withstand Aircraft flight load to avoid any damage and also
it should have interchangeability to replace with any new assembly in case
of any damage.
A sandwich Drill Jig for drilling and reaming the mounting holes in
Navigation Lamp Cover (1) and Mounting Frame Bracket (2) is designed
and fabricated. This invention overcomes the present difficulties and the
details are explained as below:
Centre Block of quantity 2 Numbers to position and lock Navigation Lamp
Cover (1) and Mounting Frame Bracket (2) are made up of Aluminium Alloy
to match to its contour and locate individually, are designed and fabricated.

Drill Jig Top (3) and Drill Jig (4) each are made up of Aluminium alloy with
holes location accuracy of 0 to 0.015 mm are designed and fabricated to
drill holes on Navigation Lamp Cover (1) and Mounting Frame Bracket (2)
individually.
4 Numbers of removable locators pins and Nuts (6 & 7), 6 Numbers of
Stopper (9) at Drill Template Top (3) and Drill Template Bottom (4) are made
up of steel Alloy material are used to arrest Navigation Lamp assembly
movement in X, Y and 2 direction with an accuracy of 0.03 mm during driIling
and reaming of mounting holes in Navigation Lamp Cover (1) and Mounting
Frame Bracket (2) individually.

Drilling of 4 (H7) (0 to 0.015 mm) diameter holes on Navigation Lamp Cover
(1) and Mounting Frame Bracket (2) is carried out in stages using al drill
guns, drill bits, reamers with special guide bushes at 15 places individually.
By using above novel setup in a systematic process. precision angular holes
5 with tolerance limits of 0 to 0.015 mm on Navigation Lamp Cover (1) and
Mounting Frame Bracket (2) is obtained.

Title: Process to achieve precision angular holes on Navigation
Lamp assemblies for aircraft
We Claim,
. A process for achieving precision angular holes with tolerance limits on
multi contour Navigation Lamp assemblies using sandwich drill jig
comprising: ,
A Top Drill Template (3), Bottom Drill Template (4), Centré Block (5) &
(10), 4 Numbers of removable Locator Pins (6) and Nuts (7), 15
numbers of Guide Bushes (8) and 6 numbers of Stopper (9);
Position of Navigation Lamp Cover (1) and Mounting Frame Bracket (2)
are secured by arresting movement in X, Y and 2 direction before
drilling and reaming operation using said Drill Template (3), (4) and
said Centre Block (5), said Locking Pins and Nuts (6) & (7), said Guide
Bushes (8) with said Stopper (9) arrangements; and
Drilling of holes of 4 (H7) diameter on said Navigation Lamp Cover (1)
and said Mounting Frame Bracket (2) is carried out in stages using drill
guns, drill bits, reamers with said guide bushes (8) at 15 places
individually.