Sample Chapter
from:
"Building Metal Airplanes"
17. Systems Integration
When
you are building a metal airplane, you are not only concerned with the basic
structure, but also with the installation of systems. These are for example the
electrical system, fuel and hydraulic lines, flight controls, pitot-static
system and so on. Start thinking at an early stage about what needs to go into
the airframe. One example would be antenna installation. In a metal airplane,
antennas have to be external for proper function, because the metal structure
shields the electromagnetic waves, which the antennas receive or transmit.
Determine the locations for the antennas you need. Most antennas are
lightweight and do not produce a lot of drag, but in areas where the wing or
fuselage skin is thin, you should add doublers or stiffeners to prevent the
antenna from overstressing of flexing the skin. Install the reinforcement,
usually a doubler will do the job, at a stage in the building process where you
have good access to that area.
17.1
Fluid Carrying Lines and Tubing
Your
airplane will most likely require the installation of some tubing. Although
tubing can often be replaced with hoses, tubing has several advantages over
hoses. Tubing is used to route fluids and gases through the structure. These
can be fuel, hydraulic fluid, oxygen, oil etc. Tubing can be used anywhere
where the parts to be connected do not move relative to each other. Do not use
tubing to connect anything between airframe and engine, vibration will break it
sooner rather than later. Aluminum tubing is suitable for most applications
except for very high pressure (as in some hydraulic lines) and areas where
tubing needs to be fireproof (firewall forward). In those cases stainless steel
should be used. Aluminum tubing is the lightest, least expensive and most
durable way to route fluids when compared to hoses, but requires a little more
skill in fabrication and installation. The tubing needs to be bent precisely
and the ends need to be prepared. The following table lists the most common
tubing sizes:
|
Dash Number |
Tubing O.D. inches |
|
-2 |
1/8 - 0.125 |
|
-3 |
3/16 -
0.188 |
|
-4 |
¼ - 0.250 |
|
-5 |
5/16 -
0.313 |
|
-6 |
3/8 - 0.375 |
|
-8 |
½ - 0.500 |
|
-10 |
5/8 - 0.625 |
|
-12 |
¾ - 0.750 |
|
-16 |
1 |
Table 21 Tube Sizes