Flight Sim Hardware - DIY
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VHF NAV Panel
In this section, we will explore the Gables G7500 NAV panel, examining its components and functions. Additionally, we will design and build a VHF NAV flight simulator control panel for training and simulation. This hands-on project will provide a practical understanding of aircraft navigation systems.
Before we dive into the project, let's start with a high-level introduction.
Types of NAV Radio Panels
There are various NAV radio panels used in the aviation world. One of the common types of NAV radio panels found in older Boeing 737s is the Dual Navigation Radio Panel. Aside from this, another advanced one is the new Multi-mode NAV panel, which can tune VORs, ILS, MLS, and GLS.
1. Dual Navigation Radio Panel
Description:
The Dual NAV panel is often found in older Boeing 737 models and a more traditional analog or early digital display for frequency readout. There are two concentric knobs for MHz and KHz selection.
G7500-03 NAV Control Panel
Image courtesy of X-plane 11 Flight Simulator
2. Multi-mode NAV Panel
Description:
The Multi-mode NAV panel often has a more modern, integrated design. It usually features a digital display for frequency readout and knobs for tuning with various navigation modes such as VOR, ILS, and GLS.
G7501-01 Keypad NAV Control Panel
Image courtesy of X-plane 11 Flight Simulator
Gables G7500 NAV panel NAV Panel
The Gables G7500 NAV panel on the Boeing 737-NG is integral to the aircraft's navigation systems, allowing pilots to tune and manage VHF navigation frequencies used for various navigation aids such as VOR (VHF Omnidirectional Range), ILS (Instrument Landing System), and DME (Distance Measuring Equipment).
Key Components
1. Frequency Selector Knobs:
- MHz Selector (Outer Knob): Used to select the megahertz portion of the frequency. It typically allows adjustments in 1 MHz increments.
- KHz Selector (Inner Knob): Used to select the kilohertz portion of the frequency, usually in 0.05 MHz (50 kHz) increments, allowing precise tuning.
2. Active and Standby Frequency Displays:
- Active Frequency Display: Shows the frequency currently in use by the NAV radio. This is the frequency that the aircraft's navigation systems are actively receiving signals from.
- Standby Frequency Display: Shows the frequency that is set and ready to be swapped to active. Pilots can pre-select this frequency for upcoming navigation requirements.
3. Transfer Button (TFR):
- This button is used to swap the active and standby frequencies. Pressing this button makes the standby frequency the active frequency and vice versa. This function allows for quick changes between navigation aids.
4. NAV Radio Tuning:
- The panel typically has separate controls for NAV1 and NAV2 radios. These are the two independent navigation radios that can be tuned to different frequencies for redundancy and operational flexibility.
5. Indicators:
- Frequency Change Indicator: Some panels have an indicator light that shows when a frequency change is in progress or has been completed.
Operational Use
1. Tuning VOR Stations:
- Pilots can use the VHF NAV panel to tune into VOR stations by selecting the appropriate frequency. The VOR signal provides directional information, which is displayed on the aircraft's navigation displays.
2. ILS Approach:
- For ILS approaches, the panel is used to tune into the localizer and glide slope frequencies. The localizer provides horizontal guidance, while the glide slope provides vertical guidance for precision approaches.
3. Switching Frequencies:
- During flight, pilots often need to switch between different navigation aids. By setting the standby frequency ahead of time, they can quickly switch to a new navigation aid by pressing the transfer button.
4. DME Information:
- Distance Measuring Equipment (DME) often pairs with VOR or ILS frequencies to provide distance information from a navigation station. The tuned frequency on the VHF NAV panel will also determine the DME information received.
Example Scenario
Suppose a pilot is flying towards an airport and needs to switch from an enroute VOR station to the ILS frequency for landing. They would:
1. Use the MHz and KHz selector knobs to set the ILS frequency on the standby display.
2. Confirm the frequency is correct by checking the standby display.
3. Press the transfer button to make the ILS frequency active.
4. Monitor the navigation displays to ensure the aircraft is receiving the correct localizer and glide slope signals for the approach.
Our Design Approach:
To design our home-made VHF NAV panel, we will take the following approach:
1. Design the PCB:
Design a printed circuit board (PCB) in KiCAD or other free PCB design applications to integrate all necessary components for the VHF NAV panel as shown below.
2. Components to Include:
- MAX7219 8-Digit 7-Segment Digital Display: To display navigation frequencies.
- One Sliding SPST ON/OFF Switch: To power the panel on and off.
- One MomentaryTactile Push Button: To switch between active and standby frequencies.
- Two Rotary Encoders: To tune frequencies with precision and ease.
- Two Panel Back Lights: To illuminate the panel and enhance visibility, especially if the PCB is enclosed in a 3D-printed housing.
3. Assembly
Solder all the components onto the PCB, starting with the smaller components and working your way up. For easier troubleshooting, instead of soldering the 7-segment display directly onto the PCB, install two female headers onto the PCB and then stack the 7-segment module onto these headers. This way, it will be easy to remove and reinstall the 7-segment modules.
Assemble the male headers on the backside of the PCB so the Arduino will be mounted from behind the panel.
Optional backlight LEDs:
Two Panel Back Light LEDs and the voltage drop resistor (220 ohm) can be installed to illuminate the panel and enhance visibility, especially if the PCB is enclosed in a 3D-printed housing.
3. Arduino:
We will be using the Arduino UNO for this project, although any Arduino variant could be used. Our custom PCB design is specifically stackable onto the Arduino UNO.
4. Enclosure (optional):
- 3D-Printed Housing: We will design and print a custom housing to protect and enclose the PCB and its components, ensuring durability and a professional appearance.
This approach ensures that our VHF NAV panel is both functional and aesthetically pleasing, with a focus on user experience and ease of operation.
