PDC1 - Propeller De-Ice Controller

For propeller driven aircraft we provide an advanced propeller de-icing (hot-prop) system. Our PDC1 controller will apply electrical de-icing to aircraft propeller blades, monitor the current flow in the process and indicate correct or otherwise de-icing operation through annunciation lights.

So far, our propeller de-icing system has been deployed on many Epic LT and Lancair IV aircraft, while also addressing various special applications. It easily interfaces with either EFIS annunciation, like the Garmin 900 series, or with traditional lights.

Functions

• Applies electrical power to blade heating elements in exact cycles
• Monitors electrical current and voltage applied to heating elements
• Indicates failure should current go out of the specified range
• Able to send measured information to displays, laptops, etc.
• Employs adaptive switching to limit heating boot duty-cycles
• Adaptable to suit various applications

Design Overview

The PDC1 employs a micro-processor to accurately switch power to prop de-icing boots and closely monitor the resultant load currents. It also indicates the operation to the pilot through two independent annunciation lights. The use of two lights adds redundancy since only one light is enough to indicate operation and failure.

For reliability and a long service life the PDC1 is built with only solid-state components. We utilized the latest solid-state technology to gain both high power switching and built-in current monitoring. In this way we avoided the use of relays to achieve a system with no moving parts.

Using a micro-processor enables the PDC1 to cater for a wide range of applications. The timing and the working current ranges are completely adjustable to be used on different boots, different aircraft, and different mission profiles.

Illustrated below is the basic wiring diagram of the PDC1. Not shown are the RS232 and CAN bus interfaces that may be used to communicate with other devices in the aircraft. The PDC1 can for example be linked a VR-3PD display unit or various other devices to indicate de-icing current.

Pilot's Panel

The pilot has one switch to control and two annunciation lights to monitor:

1. The PROP-HEAT switch will turn de-icing ON or turn it OFF. A three position switch may alternatively be wired-in to provide two levels of heating, either HIGH or LOW when not turned OFF.
2. The HEAT-ON light will light-up when de-icing is turned ON. In case of de-icing failure while turned ON, this light will blink continuously. Otherwise, when PROP-HEAT is turned OFF, the HEAT-ON light will go out.
3. The HEAT-FAIL light will light-up when a failure has been detected while de-icing is turned ON. Failure results when the electrical current flowing to the heating boots does not fall within the configured working current range.

Propeller Heating Boots

The PDC1 is normally installed within the engine compartment (in front of the firewall) and receives its power locally. This minimizes the wire-count through the firewall and increases efficiency by reducing the distance the de-icing current have to flow to get to the propeller blade heating boots. The PDC applies power to the boots directly (without the need for extra power relays) through the slip-ring assembly at the back of the propeller hub. We combine pins in parallel on the PDC connector to facilitate the switching of relatively high electrical currents through the unit.

Normal Operation

When the unit is powered (typically by switching master on) the PDC1 will light-up both annunciation lights while it performs a system self-check. After a second or two the lights should go dark to indicate that the system is ready for use.

When wanting to engage propeller de-icing, the pilot switches on the PROP-HEAT switch. The PDC1 will begin the de-ice cycle typically with phase A first. The HEAT-ON light should turn on while the HEAT-FAIL light stays dark.

As the heating cycle continues and the PDC1 moves from energizing phase A to energizing phase B you should notice that the HEAT-ON light will blink once or twice to mark this transition. These blinks continues every so often informing you of the phase transitions as well as which phase it is currently busy with. The manual explains this blinking operation in more detail.

When wanting to disengage propeller de-icing, the pilot switches OFF the PROP-HEAT switch. The PDC1 will stop powering the boots. Both lights will go dark.

De-Icing Failures

Should the monitored current to the boots fall outside the working current range, the PDC1 will indicate this failure by turning ON the HEAT-FAIL light while also continuously flashing the HEAT-ON light.

Should the problem disappear such that the current again falls within the working current range, the PDC1 will wait for at least one full de-icing cycle before turning OFF the HEAT-FAIL light and restoring normal operation of the HEAT-ON light.

Connecting to a Laptop / PC

A laptop PC and USB-to-serial adapter (such as the Bafo BF-810) may be connected to the PDC1 in order to make adjustments to settings as well as to troubleshoot the system. This is mostly concluded during the installation phase to properly configure the PDC1.

It provides the means to for example change the "Working Current Range: Minimum" and "Working Current Range: Maximum". For special troubleshooting support this software is also useful to record the working of the PDC1. These recorded operations are stored in files and may even be emailed to VR Avionics should you require special support. All are done through our System Link software which may be downloaded from this webpage (see right-hand column).

More Information

Additional information is contained in our PDC manual, wiring diagrams, etc. listed in the column on the right-hand side of the web page. You'll also find PDC firmware updates here that we provide free of charge to all customers. This firmware will be updated in the future to provide additional features and improvements. Also, please feel free to contact us with any query you may have regarding any of our products.