Fully Functional TACAN HSI - Finally complete!

[Boeing 747 Flyer]

NOTE: This thread may be of particular interest to those who posted in the "Burning HSI Question" thread!

This post is compromised of several sections. If you want to know everything, read from the start. However, if you just want to know certain bits, flick through the underlined and emboldened sections. Please note, there are VIDEOS and SCREENSHOTS at the end of the post, so make sure to read right down to the bottom if yo uwant to see these.

Hi everyone,

As well as working away at the Overhead and Pedestal projects these past few months, I have secretly been working on another project.



A HSI, or horizontal situation indicator, is one of the most important gauges in a cockpit. It allows heading, course, glideslope, VOR and even DME information at a glance; all within one instrument. Over the past few months, we have been working on getting a full-functional HSI for FSX working - with all the bits and bobs you'd expect from such a vital and complex instrument.

History

Almost 1 year ago, after visting "CockpitFest" in Newark, my father and I purchased an ex-BAE Hawk trainer instrument for £25.

It was a TACAN HSI instrument. Frr that price, we expected it to be a non-functioning part, or an unusable or outdated piece of technology. But boy, how wrong we were...

It turns out we had unlocked a treasure trove of possibilites. Our £25 investment had turned out to be a fully-functioning HSI instrument worth well over £4500. Amazed, we immediately looked at how we could get it working with Flight Simulator X.

Unfortunately, some of the original circuitry was non-compatible with anything we'd ever want to use, and as a result, we have removed it (but not discarded it!). Luckily, all the original gearing, motors and other circuitry is exactly how we'd want it to be.

A few months after obtaining the instrument, I was offered a hardware review by Spanish hardware manufacturer, Opencockpits. It was definitely a "Eureka" moment; what better to chance to obtain a product that would power our newly-purchased HSI.

So, I snapped up the opportunity to get an Opencockpits DC Motors Card (review by myself here: http://www.mutleyshangar.com/reviews/jack/dcm/dcm.htm). I would have also purchased a master card, to power some of the outputs, however I already have one, so I thought I'd save a bit and just use the one I already have.

In terms of getting the instrument working, it was an easy but very time-consuming process. All we had to do was wire all of motors and outputs to their respective cards. And then put protective components in. And then obtain a pulse counter-mechanism (see later). And then do the SIOC scripting. And the-...

You get the point. It took a very long time. Luckily for us though, we didn't have to do much "hands-on" work; the company that manufactured the part, SimTech, had done ALL of the gearing and connections for us (well, BAE actually).

Technological overview

It immediately became apparent how fragile an-instrument this was. There are so many gears and intricate clockwork-style mechanisms in the instrument that just the slightest knock could destroy it. Please enjoy sampling the internal circuitry of the instrument:





























As you can see, the instrument is a masterpiece of technology. Things to note in the above pictures are...

Motors. There are a whole range of DC motors in the instrument, however, luckily, they are all of the same type. This means that they're all compatible with the Opencockpits DC Motors Card. Through SIOC scripting, I can control all motors in the instrument, the functionality of which is explained later.

Potentiometers. These variables resistors provide "feedback" - a signal for the SIOC software to reference all its positions to. These adjust their resistance whenever their respective motors turn (they are on the same shaft as the motors).

Other wires. There are so many wires, it will take months for me to explain, in detail, every one. Just have a look at where they go and you might understand it. In the top left of the instrument, just behind the "RANGE" counter, there is a display pulse circuit which counts (numerically) up. See later for more information.

Functionality Overview



All functions are referenced to the above photograph...

Flags - OFF Flage, RANGE Flag, G/S Flag, "White Triangle" and NAV Flags are ALL fully-functional and modelled.

Course Pointer - The yellow pointer is driven by one of the aforementioned DC motors (see above and pictures). Also, the analogue-digit display visible in the top right of the instrument directly mimicks the position of the pointer (ie if the course pointer is pointing at 175, the digits show "175").

VOR Deviation Bar - The horizontal yellow bar visible in the middle. Likewise, this is driven by a DC motor, and moves left/right/centre depending on the location of the VOR tuned in the NAV1 frequency.

Glideslope Indicator - On the left side of the instrument, this yellow needle moves up and down depending on the position of the aircraft from the tuned ILS beacon frequency. If the needle is perfectly in the middle, you're bang on the glideslope. Driven by a DC motor.

Green and White Bugs - These bugs are driven by a motor(s), and can display any heading you want them to (perhaps for heading reference or for part of your navigational plan). They also have reciprocal "tails" 180 degrees from their heads.

Heading Bug - This yellow bug, which revolves around the outside of the heading scale, represents the autopilot selected heading. The move, the bug, you must use the "HDG" Knob.

HDG and CRS Knobs - The CRS knob adjusts the yellow course pointer. A rotary encoder is attatched to the CRS knob, which sends a signal to SIOC, then feeds the signal back to the DC motor driving the course pointer. The HDG knob, as previously mentioned, controls the heading bug. Both the CRS and HDG knob feature precision engineered grooves, as in real life. They also feature a true "Lock and Lift" mechanism; which means to work them, you must pull the Knob OUT then move it, then release it for it to go back in.

4-Digit RANGE Counter - This neat piece of kit uses a pulse counter to represent the distance from your VOR tuned in the NAV1 frequency. Its function is explained in detail below.

Pulse Counter Circuit

The RANGE display in the upper left corner is shielded by a flag. However, when a DME/VOR signal is available, this flag retracts and a 4 digit display is visible.

A pulse circuit, initiated through SIOC, powers this display. Each pulse (OFF-ON-OFF) adds "1" to the display. It goes all the way to 9999 before resetting to zero. However, what are the chances you'll be that far away from your desired VOR station. Very slim!!!

There is also a "reset" pin, which simply pops the counter back to 0000. Also, there is a "select" pin which chooses if I want to count UP or DOWN. EG:

To count from 0 to 43...

- I ensure that the 5V power supply is plugged in

- I make sure that the "select" pin is on UP

- I give the instrument precisely 43 pulses, controlled by SIOC

- Finally, I engage the reset pin if I want to reset the display back to 0000

NAV and "White Triangle" Flags

Whilst these flags do operate using a standard 5V output, they are special, and deserve their own section.

It is important to mention that these particular flags are GRAVITY OPERATED. This means that, even if the outputs are activated, the flags won't necessarily move unless the course pointer is in a specific position.

The White Triangle flag has three positions. "OFF" is when the flag is invisible (ie tucked behind the instrument); "ON LEFT" is when the flag pops up into the LEFT triangle slot; and "ON RIGHT" is when the triangle is visible in the right triangle window.

In terms of explanation, that's about it! If you want to know how to operate a HSI generally (ie you've never used/seen one before), then I suggest you Google "HSI instrument" or check out Wikipedia.

Oh, I almost forgot. What's a good post without beautiful screenshots! Enjoy! :icon_thumbup:











"Wait! Those screenshots just show pictures of the instrument in a stationary position. I want to see it WORKING!"

Absolutely no problem! I spent many, many hours shooting the following video clips which fully detail the HSI's operation and technical components. I would like to say a HUGE, MASSIVE thanks to Joe Lawford for taking the time and effort to upload these for me; due to my appauling upload speeds.

There are two videos, split up into parts...

HSI Operation (watch this first)

Part 1

http://www.youtube.com/watch?v=WQ3fVN3XRzk

Part 2

http://www.youtube.com/watch?v=eX73OxP8Z04

Part 3

http://www.youtube.com/watch?v=As6zAglcMoQ

Part 4

http://www.youtube.com/watch?v=qWZdviemQeg

Part 5:

http://www.youtube.com/watch?v=ichQtNk5OLs

HSI Gearing and technological information (watch this second)

Part 1

http://www.youtube.com/watch?v=7dgcQlwHKmo

Part 2

http://www.youtube.com/watch?v=K_YNZLbW0Ck

Part 3

http://www.youtube.com/watch?v=_K9GYsjLS4E

That's all! Thanks eberybody; I really you you've enjoyed this insight into the "secret project".

As always, comments/criticisms are welcome.

Kindest regards,

Jack

[Westozy]

FANTASTIC work, thanks for sharing!!!
Gwyn

[Matt Olieman]

Jack, this is absolutely wonderful. What a gift to our community. THANK YOU!!!!

Matt Olieman

[737NUT]

Very nice work!! I bet the SIOC code is getting big now!?

Rob

[Boeing 747 Flyer]

Thanks so much Gwyn, Matt and Rob (and to those who "thumbbed up" too; Nico, and Dnoize)!!! I wasn't expecting such a positive response!

Gwyn and Matt; thanks so much for the kind comments. I'm really happy to share this "gift" with our community; I put alot of time into it and it's finally paying back!

Very nice work!! I bet the SIOC code is getting big now!?

Rob

Hahaha Rob yes indeed!

Put it this way. The SIOC code for JUST ONE degree of the COURSE pointer ALONE is 25 lines long. There are 360 degrees in a circle, so lets times that by 360 (360*25) = 9000... Oh wait, then theres the glideslope, localiser, pulse display, flags... Haha!

I'm hoping to develop a more efficient script for the glideslope + localiser motors.

Jack

[fordgt40]

Jack

Congratulations - a job well done

David

[Boeing 747 Flyer]

Jack

Congratulations - a job well done

David

Thanks David! =D

[Joe Cygan]

Beyond awesome.

[Boeing 747 Flyer]

Beyond awesome.

Cheers Joe; your superlative sentence just made my day!

Jack =)

PS: If anyone has any questions re the HSI; feel free to ask, I'm always on hand.

[kiek]

Hi Jack,
I found your post really amazing.

Put it this way. The SIOC code for JUST ONE degree of the COURSE pointer ALONE is 25 lines long. There are 360 degrees in a circle, so lets times that by 360 (360*25) = 9000... Oh wait, then theres the glideslope, localiser, pulse display, flags... Haha!

I'm hoping to develop a more efficient script for the glideslope + localiser motors.

I have changed my mind, if I can be of help to make the SIOC script just let me know.

Nico