Blaze ALT-7 Operating Manual
Page 14
10 Installation
Connect the static port to a suitable static air pressure line. If you have a slow aircraft or an aircraft were the internal cabin
pressure does not change during flight and is equivalent to the outside air pressure you may find that it is not required to
connect a static port.
For installations in typical ultralight aircraft pods, be aware of possible pressure changes inside the pod during flight
caused by ram air or suction effects. This may lead to a false indication of altitude. Often these effects are dependent on
the current angle of attack of the airflow around your pod. You will need to install a suitable static port in these cases.
The ALT-7 static pressure port takes 4mm ID tubing. Use hose clamps to fasten the hose onto the ALT-7 static port.
10.1 Gillham Encoder transponder interface
The ALT-7 altimeter will measure altitudes typically to around 42 000 ft, however, this requires a transponder that uses
signal D4. Transponders that do not have D4 can only transmit altitudes up to 35000 ft. If your transponder only accepts
codes A1 to C4 then you leave signal D4 unconnected. The ALT-7 produces inverted Gillman codes as required by
virtually all transponders. The outputs are open collector types and will sink currents up to a few mA.
It is recommended to use shielded cable for the connection between the ALT-7 and the transponder if a long cable needs
to be used. The shield should be connected to ground at one point only (either on the encoding altimeter side or on the
transponder side).
The ALT-7 will switch all output drivers off if an error has occurred with the altitude sensor.
Important information
Depending on laws and regulations in your country you may not be allowed to install a transponder and associated
equipment yourself. This work may have to be done by a certified AMO or instrument technician.
Please check with your relevant authorities.
The ALT-7 encoding altimeter is uncertified equipment and may normally only be used in uncertified aircraft, homebuilt
aircraft and microlights (ultralights). Special operations permits for other aircraft may be required. Please be very aware
that any wiring mistake related to the application of Gillham codes to your transponder will result in incorrect altitudes
broadcast by your transponder. Any installation involving the ALT-7 must be checked by a suitably equipped aircraft
instrument maintenance outfit before operation. Failure to do this may be a criminal offence in your country.
Attention:
Your country may have regulations that do not allow you to install a transponder or an encoding altimeter
yourself. The installation may have to be performed by an authorized person or company. Please check
your applicable regulations with your aviation authorities.
