Most preselect systems obtain reference from an encoding altimeter
. If the logic in these systems goes haywire, you could find yourself wondering what those Billie goats are doing in the clouds.
Thirty minutes later while you're cooling your heels in the pilot lounge, the technician tracks you down with news you don't want to hear: Your encoding altimeter flunked the test because it has too much friction.
if you have an encoding altimeter (this is an altimeter that also has an altitude encoder built in), you might consider installing a separate altitude encoder and a standard altimeter.
Its easy-to-use control head references an encoding altimeter
to command the 55X autopilot.
If your Encoding Altimeter
flunks the FAR 91.411 certification, consider replacing it with a standard altimeter and a blind encoder.
The digital KAP140 is rate based and comes in three types: single-axis roll only, dual-axis roll and pitch and dual-axis with altitude preselect using the KEA130A encoding altimeter. Automatic electric elevator pitch trim is an option, too.
Recently, S-TEC introduced a new altitude preselect/alerter system with encoding altimeter. Unlike its quirky predecessor--the $3670 ST-360 alerter still in the line--the new SA-200 preselect with encoding altimeter is a joy to program and has comforting voice callouts, telling you where the airplane is and where it's going in the vertical.
Not so long ago, at least for people who engage in age denial, encoding altimeters
were the most common way of doing this.