Jump to content

[HGS] All pitch-related symbology is displayed too low on the combiner


Recommended Posts

Please compare the two pictures (intersection A2 in EDDM).


Noticable is the different vertical postion of the marked horizontal line, called "Zero-Degree Pitch Line". One important characteristic of this line is that on ground it is aligned (conformal) with the physical horizon. When you compare the pictures both Zero-Degree Pitch Lines have the same position in relation to the outside world (absolute position correct). Still, their relative position on the screen is different (RL is significantly higher).





So, what is the reason and how could it be solved?

The pitch-related symbology is based on the default seat position (instrument view: CTRL + 0), which is incorrect. This seat postion is too low, which can be checked with a tool in the cockpit - the "Eye Reference Point".





The seatposition is correct when the ball in the rear is exactly covered by the ball in the front. As the "Eye Reference Point" below shows the default seat position is too low:





The right postion is "one notch" up (UP ARROW key):




So, now that we have found the correct seat position, the AS devs need to realign all pitch-related symbology to it 😉


  • Like 2
  • Thanks 1
Link to comment
Share on other sites

  • 3 weeks later...

This problem is inherent to the way the HGS is presented in FS2020 on the CRJ.  The screen, or image combiner for the HGS projector, is designed by Rockwell Collins to project the image on the screen at a focal distance of infinity.  It is supposed to focus images at a point behind the screen in the far distance; from the pilot's perspective, you would be looking through the combiner like a window to see the information presented, which would appear to be behind the screen.  If you were to move your head the information displayed on the HGS would remain in place relative to outside references.  Essentially, if you move your head up and down or side to side, the horizon and other references should remain fixed in place, and looking at the combiner from an oblique angle you would not be able to see any of the information.  There should be no "tweaking" required of the combiner representation, as the references would display correctly regardless of viewing angle.  This is not an issue with the Boeing 787, whose HGS displays correctly.  Jump into that aircraft, power up the batteries and drop the screen down, then move the camera around to see an example of what I'm talking about.


You can also see this video for an example of how an HGS is supposed to display (in this case, I believe, on the Rockwell-Collins Challenger 604 test aircraft).  You can see that, as the camera is jostled by bumps and turbulence in the flight, the images stay fixed to the horizon reference and parts of the display disappear off the edges of the combiner (relative to the camera).  It acts in a very similar manner to a holographic gunsight or the displays on fighter aircraft glareshields, and is the same technological principle.




To make a long story short, this is a problem with the way Aerosoft has elected to display the heads up guidance computer (which also has several other issues related to the HCP presentation and functionality).  I have no idea if they're currently working on a fix for this problem.  Let me know if this makes sense.


All the best.

Link to comment
Share on other sites


Thank you for your reply.


You are referring to the missing screen collimation of the combiner, which indeed would be nice to have. However, that is not what my complaint is about. I am referring to a single group of symbols being displayed at a too low part of the screen compared to the rest of the symbols.


Here is another comparison of a RL photo and a screenshot, both made with the same preconditions (altitude, airspeed). As before, there is an obvious discrepancy only regarding all pitch-related symbols. Looking at the pitch scale it almost seems, as if the AS CRJ would have a significantly higher pitch, which is not the case. At this attitude both the Flight Path Symbol and the Zero Degree Pitch Line ("Horizon Line") already start to disappear behind the HSI block. This is incorrect for several reasons and renders the system almost useless.




Collimation would not make any difference here, because it affects all symbols on the screen in the same way - the difference would persist. And even with collimation you have to adjust your seat to a correct position using the "Eye Reference Point" as stated previously. This tool acts as a front and rear sight and defines a so called "Pilot's Eye Box", a 3D area where the holographic image is visible - when moving outside of this box IRL the screen would start to get blank. I don't know about HGS implementations in more modern aircraft, but the CRJ does behave like that.


Dear Aerosoft Devs/Reps,

I would appreciate a confirmation that this is on your list.


  • Like 1
Link to comment
Share on other sites

I see now what you were trying to say with regards to pitch symbology.  Sadly I still don't think this is a problem that can really be addressed until the collimation issue is fixed.  The pitch reference line and boresight symbol is useless without an adequate tracking of the correct horizon line.  The image you posted on the right also appears to have a much higher pitch attitude (which would cause the horizon line and boresight symbol to drop off of the collimator screen).  I would test this further to see if I can get closer to the image on the left with the current model (the image on the right seems correct to me given the pitch attitude) but the new update has bricked the HGS completely on the RJ.  I'm interested to see how things progress once they have collimation implemented correctly; I feel like once that is in place the rest will follow, or will be easier to address at any rate.  It's hard to make an accurate judgement of whether or not the display is correct when its implementation is fundamentally flawed.

Link to comment
Share on other sites

After updating last night I can see that the seat position is in fact now correct (Based on the positioning balls) but the HUD Ladder is still incorrect with the collimation implemented and stuck to the horizon (The horizon zero pitch bar is in the same position that it was in prior to seat adjustment and collimation). It actually appears that the entire VC needs to be rotated down by a couple of degrees to emulate the proper negative pitch of the aircraft on the ground, this would also correct the ladder while in Cruise and Landing. I do love the collimated effect, using Smoothtrack the simulation is spot on, flying the aircraft was great but the symbols were way too low on the HUD when in correct pitch and trim for TO, landing, and cruise. 





Link to comment
Share on other sites

15 hours ago, Jeremy Jeffreys said:

since the collimation is now incorporated has the proper pitch ladder position and the default seat height been corrected for the collimated HUD?


Not at all, I am afraid. It's just the visual viewing system of the HGS that is now modelled correctly. As I explained in my previous post, collimation affects ALL displayed symbols equally: It cannot eliminate a mismatch between individual symbols.


With collimation the original problem now shifted to the non pitch-related symbology being displayed too high when the seat position is adjusted according to the "Eye Reference Point" (see screenshots below):

  • Altitude tape, speed tape, Flight Mode annunciator etc. get cut off by the upper frame of the combiner.
  • HSI (PRI mode in flight) revealing a gap underneath. As a result the Flight Path Symbol, Guidance Cue, Zero Degree Pitch Line still disappear behind the HSI block.







Link to comment
Share on other sites

so what needs to be tweaked by Hans is the placement and spacing of the various symbology:


1. HSI is too high, shift lower so there's more space between the horizon bar and HSI

2. contain the top, left, right boundaries as shown below, it's too wide now and too high 


here the waterline is ~3deg and +/-5deg pitch ladders are visible, the screen shot in previous post doesn't even show the horizon.


i hope this gets fixed.



Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Create New...