View Full Version : Help understanding EE Lightning Attitude Indicator etc

Conventional Gear
8th Dec 2012, 04:03
Hello to all,

Whilst grounded due to a total lack of funds :hmm:, I've been turning my attentions increasingly to flight sims. I hope I'm not in the wrong forum, but I'm not asking for help on the sim part, rather in understanding the display of the real instrument.

So, I'm trying to replicate the Attitude Indicator from an EE Lightning F6. This unit is described in AP101B-1003 as 'Attitude Indicator F4C'

I've grasped the principle of the roller-blind display, so have a good representation of the horizon moving up and down and rotating. That was very straightforward to do as it is easily facilitated in XML.

Where I am stuck is with what I'll describe as the moving 'dot'.

As I understand it looking at pictures of the instrument it was a dot held over the blind by wires. I've read the abstract from the Kelvin & Hughes patent but can't quite grasp what the pilot would have actually seen on the display in flight.

I understand the dot was to indicate roll/pitch whilst the aircraft was at very high positive or negative angles of pitch and therefore presumably the horizon display would have appeared all white or all black.

I also understand it was constrained to horizontal and vertical motions (i.e. there was no rotational element to the movement).

I guess what I'm asking is what did the pilot actually see as the aircraft pitched from say horizontal through to 90 degrees vertical?

I think I understand how roll angle was indicated by the 'dot', for example, if the aircraft's right wing was down 20 degrees the dot moved to the left to the 20 degree ring on the display. I don't know though if this was a constant display at all flight attitudes or if it only came into action after the horizon disappeared from the display? Or even if I have understood it fully or at all!

I hope someone can explain it to me :ok:

Once I have this sorted I'm hoping to move on to doing the TACAN/ILS/NAV display, so no doubt I'll have more questions on those to come. :)

8th Dec 2012, 06:52
If it's the same as the OR946 display in the Gnat, the wire-mounted bead was part of the flight director system and the aircraft was manoeuvred to keep the bead centred.

Extremes of pitch attitude were indicated by a zenith / nadir star. If I recall correctly, to recover from an extreme attitude, you rolled to put the 'star to the six o'clock', pitched in the direction indicated by the longest arm of the star to the nearer horizon, before spot rolling out if inverted.

Mate JF when he almost lost a Lightning recalled seeing the nadir star in the centre of an all-black attitude indicator, gently rotating......shortly before his 11+G North Sea avoidance manoeuvre!

Conventional Gear
8th Dec 2012, 07:32
Ah, the mist clears I can see now why I was in a muddle, there was talk in the patent of moving dots to indicate roll/pitch and I've confused this with the Lightnings flight director indicator. I would guess the roll/pitch dot idea wasn't followed through to operational instruments.

Hence why I was trying to figure out the 'dots' relative movement to the horizon display during attitude changes, which was a complete misconception. I can grasp the nadir/zenith star concept so I should now be able to finish that part of the project. :ok:

I really can't imagine what it would be like flying something like the Lightning, I get worried enough in a PA-28 at 2+G ;)

8th Dec 2012, 15:51
The Flight Director dot was originally designed to facilitate a Mach 0.89 climb, as the most fuel-efficient way of getting the aircraft up to an operating height.

The Attitude Indicator FD took its computed feed from the Flight Control Computer, with inputs from the height and speed units (whose names I can't remember).

AI's were not all that reliable. Contrast them with the superbly engineered navigation system (analogue/barely digital!)

Conventional Gear
8th Dec 2012, 21:48
Thanks LFittNI for the additional information :ok:

I've found the modeled roller blind AI very intuitive to fly with so far in the simulator. I read an article in the Flight archive which described how it revolutionized the instrument panel in high performance aircraft and certainly that is experienced when using the display in the simulator too.

So as I would understand it, the FD dot would have moved up or down to facilitate the maintenance of the Mach 0.89 climb, too slow and I assume it would have indicated to the pilot to pitch down (dot moves from central index downwards) too fast would have given a similar pitch up indication? (I'm assuming that the power setting would have been already established so the pilot controlled the speed in the climb with pitch only).

I would guess flying at the correct pitch through the climb would have otherwise been quite a challenge due to substantial weight change of the aircraft due to fuel burn in the climb?

Do you know if the FD dot also moved left/right, presumably to help maintain bearing during the climb?

Sorry for all these questions, but in addition to modelling the unit in the simulator, I may also have the opportunity to attempt to bring an example of an actual instrument back to life in the near future, through interfacing with the simulator. So I'm trying to build as complete an understanding as possible, not easy when I have never seen the unit in actual use.

Conventional Gear
9th Dec 2012, 01:13
Here's a mercifully short sim video clip of the modeled Roller Blind AI.

It's not yet a graphical masterpiece or optimised for the sim, but hopefully it can be confirmed that the basic functionality is there:


I replicated the North Sea avoidance maneuver too in the video, something that with most stock instruments in FSX would have been extremely difficult to achieve.