19 Jun 2017 08:58 - 19 Jun 2017 14:04#34566by ScottBouch
Well, this weekend I managed to pick up:
- 2X Percent RPM indicators as used in most cold war RAF jets (the ones with the small dial and the main dial).
- A rate of climb indicator, no idea yet on the aircraft it's from.
- A flap position indicator, again from a mystery aircraft so far.
- A compass unit with direction indicator for VOR / ADF etc.. from Viscount and a few other bigger aircraft of that era.
All these bits will help me start to put together a "Generic Cold War Era" panel that is useful for a few aircraft types.
I couldn't find speed / altitude indicators that were electrically operated, only pneumatic, so left them for now. Also, all the artificial horizons I found had internal gyro's, which is not really useful for a project like this... Ideally I'd want to find an artificial horizon that uses a remote gyro, and is purely an indicator.
Can't wait to start trying to pull data from FGFS and figure out how to drive these indicators. The compass will be the most complex.. ROC should be the easiest, so may start with that. Once I have the compass working, It'll be fun to do another MP flight with others advising on bearings to follow!
I also picked up two temperature indicators (up to 300 degrees C) which will be used on my two log burners flue pipes at home!
19 Jun 2017 10:45 - 19 Jun 2017 11:59#34568by ScottBouch
There is one system that uses a centralised information system, and purely electronic indicators, the IFIS,as seen in the later Lightnings, Hunter T7A, Gnat T2, Buccaneer S2, and a couple of Harrier variants.
The IFIS (Integrated Flight Instrument System) was created by Smiths Instruments as previously all systems had their own gyros and pressure transducers (this would be one set of Autpilot, one set for Radar, one set for Navigation equipment, etc.. and then the cockpit indicators on top... this meant a lot of repeated kit in the aircraft.
Smiths' IFIS system reduced aircraft weight as it uses one Master Reference Gyro (MRG), and it's own pressure transducers to supply common information to all the systems mentioned above.
However, these indicators cost an arm and a leg to buy! I saw one of the strip speed indicators with a broken glass for sale for £90..
But It made me think that there may be other systems (more modern) that also work in the same fashion and could be electrically simulated from FGFS data.
Aircraft that were fitted with the IFIS also carried standby indicators in case it failed or there was an AC power failure, and these generally were pneumatic, or had their own gyro.
The main driver for this project for me is that I'm an aircraft preservationist - So I want to see the indicators working as they would in a real aircraft. I've seen real indicators get hacked apart and servo motors inserted, but this actually leads to quite jerky / non-fluid movement of the pointers, and also sounds plain wrong. All these original indicators made their own noises, a cold-war era cockpit is not a quiet place! Also the preservationist in me weeps a little when you see pieces of history get cut up.
I met a professional sim builder at the show, he had a replica Lancaster panel with him; his company had made all the indicators from scratch using perspex layers and servo motors. It looked nice, and worked with their own interfacing software controlling the servos. He took quite an interest in my projects, and we are going to stay in touch as we could be helpful to each other.
Ok, so here's the Flap position indicator, with info I (luckily) have on it.
This one will be tricky to operate, as it's Desynn type system (a variable resistor with 3 connections to a single track, and 24V across two opposing wipers).. See circuit diagram.
I can think of two ways to simulate the 3x voltages required:
- Picking three positions, spaced 120 degrees apart of a sine wave set in the software.
- Have three sine waves set in the software 120 degrees apart and pick the same points along all three depending on the input.
19 Jun 2017 15:57 - 19 Jun 2017 16:10#34572by ScottBouch
Rate Of Climb indicator.. not sure on the units, but -10 to plus 10 somethings.
Dead simple to operate at first glance, just a variable voltage need applying... But... that's only in one direction, as the indicator rests at zero, it needs a variable current in both directions to go up and down.
Easiest way is to use two PWM outputs, one for positive movement, the other for negative, and have them operating an H-bridge circuit, like bi-directional motor control.
19 Jun 2017 17:05 - 19 Jun 2017 17:32#34576by ScottBouch
Hi Timi, thanks for that... The IFIS rate of climb dial in the pictures at the beginning show it from -6 to +6, which is x 1000, making 6000 ft / minute.
The IFIS indicators were used in some of the fastest jets of the time, so I cant see many aircraft would have a need for 10,000 feet / minute! .. space shuttle perhaps?
So yes, you could be right with M/S! But how many aircraft used metric units of measurement throughout the cold war? I'd be surprised if any British did, perhaps it's intended for a European aircraft? It is British made by Weston's, I don't know if they exported to other countries or not...??
Could it be feet per minute x 100? - up to 1000 ft/minute ie, for a slower moving aircraft? Or is that ridiculous? - ie; i'm not sure what the rate of climb / decent would be for something like a Hercules..
19 Jun 2017 20:03 - 19 Jun 2017 20:05#34579by ScottBouch
That AP covers a multitude of indicators - I have 600 pages of it, and there is still lots more I don't have! ... so most aircraft of a certain vintage are likely to have some indicators covered by this AP.
Really, the aircraft illustrated parts catalogues (IPC) should list all indicators used in the cockpit by their stores reference number (starting 6D for indicators), but I don't have any IPC's at all.
Next best way to roughly identify (to be treated as Secondary information as it can include results from museums and restored cockpits) it is by trawling google image results of cockpit images.. By doing so, I just found (by having a very quick look) the Canberra's, Gnat, and Vulcan, Victor, Shackleton, Hunter, Wessex, Whirlwind, Vampire, seem to use -4 to +4..
The pilot's notes for the Canberra and Gnat (not checked the other yet) don't seem to explain the units, I think the aircrew manuals are needed, as the aircrew manual for the Lightning does explain it - which is where I got the 6000 ft/min figure from earlier.
Sea Venom, Tucano, Phantom, TSR2, and Jaguar seems to be -6 to +6 like the Lightning (from google hits).
Basically I can't find this - 10 to +10 indicator in any aircraft so far!
It seems to go by several names like vertical speed indicator which I have personally
seen most of the time but also vertical velocity indicator, rate of climb and descent indicator, rate-of-climb indicator and variometer.
So it must be off something slow, I will keep having a look..
Just to throw another one out there; since it's not marrying up with many VSI's we've seen - it says Up and Down, (not Climb / Fall etc..), is there any other parameter that it could be for that would use Up and Down? Ie: Angle of attack? ILS glidepath in the vertical axis? Or am I talking utter garbage now? I've never seen such an indicator used for glidepath indication, so am probably talking rubbish, but just thought it might be worth a mention as it may trigger off another thought process.
As a glider pilot I can't claim to be an expert on any of this. Anyway, the AOA
indicators I've found look like this.
So I don't think the scale fits for AOA. And ILS glide slope indicators have
a vertical and a horizontal component which need to be aligned in order
to be on the glide slope, so I don't think it's for that either. It looks like a VSI
in my opinion. But what is the scale, ft/min x 100, ft/min x 1000 or m/s, not
And one more indicator with positive and negative values come to mind,
the G-meter. The scale would be usable for that one. Although G-meters
often have two extra needles and they stick on the max positive and
negative values achieved on the flight.
But I haven't seen a G-meter with the words up and down though.