Honeywell BA-141 altitude indicators and SI 225/285 airspeed indicators are avionics units common to a variety of jet aircraft. When these units are sent in to Duncan Aviation for repair, one of the most common squawks reported is pointer jitter. Pointer jitter occurs when the indicator's pointer oscillates or vibrates and does not give a clear reading. This squawk can be caused by a dirty sycho, defective potentiometers or power supply capacitors that get weak over time. If the pointer jitters badly enough, it can and does cause a flagging issue during flight.
It is a very simple process to troubleshoot altitude and airspeed indicators if you have a spare indicator available. If you do not have a spare indicator, Duncan Aviation has a loaner available.
Replace the suspect unit with a spare unit. If the problem goes away, the indicator is faulty. If the problem remains, the fault is elsewhere, most likely with the air data computer (ADC).
Both the altitude and airspeed indicators provide valuable information to the pilot, but cannot function on their own. They are fed the information from the ADC and in turn report the appropriate information to the pilot. It is not uncommon for these indicators to be blamed for a squawk that resides in the ADC.
When sending the units to Duncan Aviation for repair or overhaul, it is always a good practice to send both the indicator and ADC together. This allows our avionics technicians to identify the cause much quicker and act accordingly. Every unit sent in will be inspected for cleanliness, damaged or broken parts and loose screws. It is put through a full function test that includes inspection of the lights, wiring and electronic components.
If you send Duncan Aviation your Honeywell BA-141 altitude indicator and your air data computer at the same time, we will certify and return them with an altitude correction card. We must have both the ADC and the BA-141 altitude indicator in order to certify and return with an altitude correction card.
Duncan Aviation is the only Honeywell Authorized Service provider for these units. If you should have any questions regarding these units, don’t hesitate to contact me. To schedule a repair or overhaul event, contact any one of our Duncan Aviation avionics customer account reps.
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