46
2 Wind Tunnels and Other Aerodynamic Test Facilities
Fig. 2.12 High Speed Machining (HSM) of a fuselage model (© ONERA)
aluminium is used for fuselages or parts which are not subjected to high loading.
Moreover the interior of the model cannot be totally filled so as to accommodate
instrumentations (see Fig. 2.13). A good example is the aerodynamic balance (see
Chap. 8) to measure the forces and the moments acting on the model. The necessary
stiffness of the balance limits its miniaturisation and it its dimensions might constrain
the size of the model.
For static pressure measurement on an aircraft model it may require more than
1000 pressure ports (tapings or tubes with a diameter of less than 1 mm), particularly
on the wing. These tapping are connected individually to the pressure transducers by
metal and/or plastic tubes while passing inside the model together with additional
electric wires for various other sensors (balance, inclinometer, pressure transducers
steady and unsteady, etc.).
Hence a considerable volume of cables and pipes has to be taken into account
in the internal layout of the model (see Fig. 2.14). This resulted in instrumentation
complexity which led to the development of transducers with built-in pressure tap
and signal conditioning so that the output is digitised and acquired directly; this
greatly reduces the space occupied by the electric wiring. The disadvantage is the
high cost of design and manufacturing of the model, therefore this type of transducer
are reserved for large models which are highly instrumented.
2 Wind Tunnels and Other Aerodynamic Test Facilities
Fig. 2.12 High Speed Machining (HSM) of a fuselage model (© ONERA)
aluminium is used for fuselages or parts which are not subjected to high loading.
Moreover the interior of the model cannot be totally filled so as to accommodate
instrumentations (see Fig. 2.13). A good example is the aerodynamic balance (see
Chap. 8) to measure the forces and the moments acting on the model. The necessary
stiffness of the balance limits its miniaturisation and it its dimensions might constrain
the size of the model.
For static pressure measurement on an aircraft model it may require more than
1000 pressure ports (tapings or tubes with a diameter of less than 1 mm), particularly
on the wing. These tapping are connected individually to the pressure transducers by
metal and/or plastic tubes while passing inside the model together with additional
electric wires for various other sensors (balance, inclinometer, pressure transducers
steady and unsteady, etc.).
Hence a considerable volume of cables and pipes has to be taken into account
in the internal layout of the model (see Fig. 2.14). This resulted in instrumentation
complexity which led to the development of transducers with built-in pressure tap
and signal conditioning so that the output is digitised and acquired directly; this
greatly reduces the space occupied by the electric wiring. The disadvantage is the
high cost of design and manufacturing of the model, therefore this type of transducer
are reserved for large models which are highly instrumented.