Synthetic Vision using CRT possible?

[Liam1407]

I'm a student and new on here,

Quick question with regards to Synthetic Vision Displays, is it possible for these to run off CRT or would the resolution along with display quality be too poor to interpret the visual information and hence why LCD would be much better?

Any points on this matter would be greatly helpful,

Cheers!

[falconer1]

you answered the question yourself…

the resolution of CRTs ist not good enough…

LCDs are necessary…

's not rocket science...

[Intruder]

What resolution is required for synthetic vision? AFAIK, mainstream CRTs are capable of AT LEAST UXGA (1600x1200). I have seen reports of people using a CRT for 2048x1536 @60Hz.

I believe the REAL answer is that CRTs are much heavier and require significantly more power (and generate more heat) than LCD displays. There is little chance that someone would design a "new" avionics system based on CRTs, if LCD is an option.

[ZFT]

In addition CRTs age, have a far higher MTBF and are subject to catastrophic failures resulting in expensive burns to the CRT. ( A typical Honeywell DU repair with CRT replacement can we in the region of US$20K!!!)

[AirRabbit]

Quick question with regards to Synthetic Vision Displays, is it possible for these to run off CRT or would the resolution along with display quality be too poor to interpret the visual information and hence why LCD would be much better?

Any points on this matter would be greatly helpful

Notwithstanding the accuracies found in the comments above, the straight answer to your question, “…would it be possible…”, is yes, it is theoretically possible – as long as the system managed to meet the specific requirements that are currently found in the specific requirements for the kind of device on which it would be used. If you read through the requirements for any given level of simulation – depending on what regulatory system from which you plan to seek approval/qualification – you will note that the requirements for the lesser levels of devices are not as stringent and go all the way down, in at least some venues, to the point where visual systems are not required at all; and if used, they must simply not detract from the training being conducted. In fact, there are quite a few CRT-based simulation visual systems currently in use around the world – and, in fact, on the other hand, there are systems in use that very likely wouldn’t stand a chance of pilot acceptance except for the fact that some time ago there wasn’t anything better - and that/those system/s has/have been granted the authorization to remain in use, which is not saying that any such specific system would be found to meet current requirements.

Hope this helps.

[awblain]

Does anyone make large (or small) CRT displays any more?

Even oscilloscopes all digitize the signal and display it on a LCD/LED/OLED…

[Sir George Cayley]

My understanding is the HUDLS that fuse EVS, HUD thingys and SVS are the way forward.

There has to be a separate set of monitors for the RHS for a level of redundancy but 'no outside view' is possible.

[Another St Ivian]

As alluded to above - the answer depends on the level at which you're looking at the problem.

At a pure hardware level, could a CRT, like those currently used in aircraft, be used to display synthetic vision imagery? Yes. The CRTs are in essence no different from conventional ones used with computers, and would generally be fine.

Now, going back a level of abstraction from the pure hardware level and looking at this from a systems point of view...no, you couldn't. The standard architecture for aircraft utilizing CRTs is typically that you have some systems which generate guidance or navigational information (i.e. the FMS), which generate digital information and transmit it via an ARINC protocol (such as ARINC 429) to a display/symbol generator. The display/symbol generator takes this information, which you can imagine to basically be a long list of variable names and values, and turns that into something a pilot would recognize. That output is then what is rendered on the screen. It's pretty rigidly constrained, and the symbol generator can only really produce precisely what's been specified in the list (i.e. artificial horizon, HSI, etc).

With some installations you pipe all those ARINC labels (variable names and values) straight to the display and it does it all onboard, for some others you have a standalone box which then connects to a display via something roughly like a VGA connection.

Modern aircraft with fully integrated synthetic vision systems tend to use a non-federated architecture, which resembles something closer to that of a central set of computers running a series of applications, rather than discrete black boxes. You'll generally have something closely approximating a graphics card, which renders the whole mix of HUD imagery, synthetic vision pictures and the rest of it, and transmit that as broadband video data (see ARINC 818).

If I had to take a stab in the dark....are you looking at the feasibility of upgrading the black boxes 'behind' the CRT displays in something like the older Airbus models, bizjets, etc? If so...the CRTs in those aircraft cannot be used simply as dumb displays, and would have to go, along with the symbol generator and the rest of the gubbins.

[Intruder]

Depending on the level of graphics needed, and the "intelligence" of the CRT box, you may well be correct. However, there were several old systems that successfully used CRT displays for a combination of low-rez digital gfx and real-time IR images. The A-6 Intruder was one of them.

Also, the current 747-400 can interchangeably use CRT and LCD displays in its instrument panel. I admit that the 744 does not yet display live IR or extremely high-rez synthetic vision-type gfx, but I am not sure that the CRT display alone would be the limiting factor in a future upgrade. That said, the LCD displays certainly are more reliable...

I also agree that from a Systems Engineering point of view, there is little reason for someone to try it, even as a retrofit. I doubt the market would be big enough to support such an effort, even if technically feasible.