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The Ultimate Homebrewed Cockpit - Part 2
by Gene Buckle

I made a serious omission in the first journal article. I neglected to explain what the end goal with this F-15 is going to be. Allow me to rectify that right now....

An actual F-15 cockpit

I'm after what all cockpit builders are after. An environment that's as realistic as possible, within the abilities of the builder's budget and resources. This could be something as simple as having a specially built desk that lends itself to flying PC simulator games or as complex as utilizing a full cockpit like myself and some of the folks working with real McBoeing 7XX flight decks.

For my project, I'm reaching for a 100% static environmental simulation. I say static because the cockpit will have no motion systems giving the pilot cues. I'm planning on reproducing the operation of every system and control that's available within an F-15C cockpit. It includes things as insignificant as the IFF antenna select on the left console, to a fully operative HUD. All of these systems will operate independant of the host flight simulator. For instance, none of the offensive systems will operate when using Fly!, with the exception of the attack radar. That will function. When using a combat package like Falcon 4, everything in the cockpit should be fully functional.

I can tell that you're sitting there thinking, "Man, this guy is off his rocker. There is no way in hell he can do this." Well, you're wrong. You'd be amazed at how simple something like this can be accomplished, and I'm going to tell you HOW.

EPIC (Extended/Programmable Input Controller)

There are two key components to building an accurate simulator cockpit. The first is the EPIC board by R&R Electronics. This one card is the end-all, be-all of cockpit interfacing. With the card and the first expansion board, you've got access to 304 inputs for things like switches and rotary encoders as well as 16 analog inputs for things like multiple throttles, toe brakes, mixture or propeller pitch controls. Each input is totally programmable using the EPL programming language that is downloaded to the card.

The EPIC board also has some pretty neat add-on cards. There is the 32 point output module that allows you to control anything from a single LED indicator, up to four 4 wire stepper motors. You can have 4 of these modules connected to a single EPIC board. There is a 7 segment LED controller (up to 4 as well) that can control 32 digits per board. This is priceless for doing radio frequency displays, digital DME indicators and MCP autopilot indicators, or anything else you need a numeric display for. Additionally, there is a gauge & meter module that supports up to 8 air core or milliamp meter gauge movements. This can be used for doing airspeed indicators, EGT gauges, TIT gauges, or anything that has a needle on it and doesn't require more than 305 degrees of travel (mechanical limit of the air core movement) Again, up to four of these modules can be used. The last expansion board allows you up to 20 rotary encoders like the kind used to select frequency on a radio or to change the target altitude on a commercial jets' MCP. It also provides for up to 4 16 bit digital joysticks. This is valuable since it allows a much higher precision value for things like throttle position where 0.255 isn't enough. All of this combines into an unbeatable interface system that's pure perfection for the home cockpit builder.

The second key component is known as a digital to synchro converter. This little magic box takes a 16 bit value from a digital source and translates it into a position the synchro will move to.

Most analog instrumentation that you'll find in any aircraft manufactured from the 1940's onward utilize a little gizmo that operates very similar to a stepper motor. It uses 400Hz A/C as it's power source - primarily because the transformers and generators to create a 400Hz waveform are lighter weight than those required to produce a 60Hz waveform. The voltage is typically 26v, 28v or 115v, depending on the type of synchro used and the system involved. The benefit of using a synchro over a stepper motor is its smoothness of motion. Because it runs on A/C it can be "infinitely" positioned. This gives very accurate motion and is critical for the movement and simplicity of such instruments and the artifical horizon and the gyro compass.

 

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