Altitude Hold Features
The EZ series altitude hold systems uses the same MEMS gyro that has proven so successful in the Trio EZ Pilot autopilot. The gyro is used to accurately measure pitch changes in the aircraft. It is very responsive and proves extremely capable in handling turbulence.
The pressure sensor is the internal altimeter for the altitude hold system. It is a high resolution device that allows measurement of altitude changes as small as six inches. It is temperature compensated for repeatability over a wide range of temperatures.
Safety is priority one at Trio. When you turn your elevator control over to an autopilot you have every right to expect that it has multiple safeguards to prevent overstressing your aircraft. The servo has twin processors to monitor its functions (and each other), the motor drivers are triple protected, and an accelerometer in the altitude hold module monitors “G” forces. If anything occurs that the system recognizes as inconsistent with safety, it will sound an alarm and disconnect the servo from the elevator control system.
In the event the aircraft experiences abnormal G forces, the EZ-3 system is designed to automatically disconnect from the control system before structural damage can occur. It will sound an alarm and disconnect if it senses a sustained vertical acceleration (+ or -) of 1 G for more than a few seconds. In turbulence, it will tolerate stronger, short-interval G excursions without disconnecting. However, if severe turbulence is encountered it will disconnect when the intensity approaches that which dictates that the pilot should be in control of the aircraft.
The rotary encoder (the black knob) is useful in setting brightness and contrast on the LCD switch screen, as well as system gain and other functions. However, in flight it offers the unique capability of allowing the pilot to change altitude in small increments. Each “click” of the control changes altitude by several feet. This is quite convenient when you must update your altimeter barometer setting while flying cross country – just reset the altimeter and then rotate the knob slowly until you have climbed or descended to the proper altitude. This eliminates the necessity of disconnecting the A/H, flying to the new altitude and then re-engaging the A/H.
When making large changes in altitude, it is convenient to use the remote disconnect button (mounted on the aircraft control stick) to disconnect the A/H system. Pressing the button momentarily disengages the servo and the pilot can then fly to a new altitude and re-engage the servo. If the pilot pushes the remote disconnect switch and holds it down for over 3 seconds, the servo will re-engage when the button is released. Thus, to change altitude, the pilot may push the button down and hold it while flying to the target altitude and then simply release the button – the servo will automatically engage and hold the new altitude.
The LCD screen that is incorporated into the lighted push button switch provides an innovative way to conserve panel space, while allowing graphics presentation of the altitude control messages, alerts and warnings. The backlight is tri-colored (green, amber, or red) depending upon the message being shown. Because of the nature of the LCD screen polarizer, the pilot is advised to wear non-polarized sunglasses when viewing the screen.
The altitude hold system microprocessor uses algorithms that detect when the system is demanding excessive servo pressure to maintain altitude – which would be the case when the elevator control system is out of trim. This might happen on a long flight as fuel is burned off and the aircraft exhibits a tendency to climb. The A/H system will prevent if from climbing, but as fuel is burned the pressure that it must exert on the elevator control will grow. At some point, the system will ask the pilot to re-trim the aircraft by using the manual elevator trim system. Once trim is reestablished the message will be removed. (Note: If the aircraft has the Trio automatic elevator trim option, the trim motor will automatically keep the aircraft in trim as the flight progresses)
Because the LCD switch and the rotary encoder are two separate units, they may be mounted in several possible configurations. To accommodate a number of different arrangements, Trio can provide switch bezels and mounts to help make an attractive installation. The bezels that we currently offer are shown below. To download a PDF document that gives dimensions, click here.
The “Gold Standard” link above will take you to a page with full information on the servo