Question: HUD pitch ladder

[HawkEXO]

I'm not sure that I understand the pitch ladder on the Mirage F1 HUD. Why does the 0° line not coincide with the horizon like it does on the HUDs of other jets?  I couldn't find the answer in the manual.

See attached image.. I'm at nearly 0° pitch on the HUD ladder and I am in level flight (note my climb rate is near 0 ft/min on the vertical speed indicator), but the 0° position on the HUD is in the dirt some 15-20° below the actual horizon.

I tried adjusting the seat height to see if that made a difference, but it doesn't really change anything.

To be clear... I'm not saying it's modeled incorrectly. I just don't understand why it's different on the F1 than other aircraft where the 0° line is right on the physical horizon.

Edited June 28, 2023 by HawkEXO

[dorianR666]

3 hours ago, HawkEXO said:

Why does the 0° line not coincide with the horizon

why should it? there is no reason for it. remember: this hud doesnt have flight path vector. so there is nothing to be gained by having the ladder matched to horizon.

this is simply attitude indicator on collimated display, so you dont have to look down on an instrument all the time.

 

3 hours ago, HawkEXO said:

like it does on the HUDs of other jets?

this is actually how the jets of this era used to be, its normal. f-14a/b hud looks the same.

 

Edited June 28, 2023 by dorianR666

[Sacarino111]

3 hours ago, dorianR666 said:

this is actually how the jets of this era used to be, its normal. f-14a/b hud looks the same.

Yes.

And that bothered me a lot, to the point of not flying it for a long time... until I found the HUD trim knob, so now, every fly I make with the F-14, I trim the HUD display so the 0º line coincide with the horizon orwit  the V.V. when the plane is stoped on the runway and the alignement is done.

To me, having the V.V. on the 0 line helps a lot, I could not make myself to the other way.

I know the HUD is not the main nav instrument on those day planes, but I was so used to it from all my life as a simmer that I couldn' thandle it.

I don't have the F-1, so I can't tell if there is a HUD trim.

Saludos.

Saca111

[Bremspropeller]

As dorian said, there's no reason for the HUD pitch-ladder to coincide with the horizon, as there's no VV in normal mode. It's just a fancy attitude-indicator and in terms of doing it's job it's working perfectly fine. You'll also find the HUD to be geared, btw: The 10° pitch line is nowhere near actual 10°from the horizon line, yet you'll be at 10° when your nose (boresight symbol) is aligned with the line. Don't look at the horizon, look at the horizon-reference line in the HUD. You're on instruments!

There's got to be an engineering reason why it's the way it is, but as dorian also pointed out: Geared HUDs are (were) quite normal. My take on it is that if you're referencing the gun-line (which is about your true water-line), then you'd be running out of HUD-glass and windscreen on top. Hence you're just building a smaller sight with a depressed horizon. Once you stop thinking about it and just fly it, it stops being an issue. Just use it to ballpark set a pitch attitude and do the fine-tuning with the steam-gauges inside the cockpit. Don't chase the VSI, just reference the altimeter. It'll get to be second nature after a while.

If you want a horizon line that's actually referencing the horizon, switch to Landing mode and you'll also get a simple VV. I never use that mode at all, as flying 10° AoA and normally referencing the runway (or PAPI/ VASI) will get you there as well. If you're on the ILS or an NPA, you're looking elsewhere most of the time anyway.

Edited June 28, 2023 by Bremspropeller

[HawkEXO]

Interesting stuff.  It would certainly make bombing via depression tables easier if you could line up the target with the 10° or 20° line, for example.  But the lines are just arbitrarily placed on the HUD in the Standard Mode.

We have a flight path indicator in Approach Mode but not in the Standard Mode.  Also, upon further investigation, the horizon line in Approach Mode appears to coincide and the 10° increments are accurately placed I think.  Maybe I should be performing bombing and rocket attacks in Approach Mode.

Edit: Brems just covered most of that last part.  We were typing at the same time I guess

Edited June 28, 2023 by HawkEXO

[HawkEXO]

Nevermind on using Approach Mode for bombing.   I forgot the pipper is caged in that mode. 

[Bremspropeller]

Just use the pitch-ladder to get your dive angle and then transition/ cross-check to the pipper. It's all just a matter of getting used to and training.

After all, manual bombing is more an art than a science. Says the artist formerly known as "Missed"

Edited June 28, 2023 by Bremspropeller

[HawkEXO]

This was hardly a complaint... just me trying to learn everything about her.  I'm getting my preferred attack profiles worked out amidst many many enjoyable hours flying strike runs over Sanai.   

[IvanK]

"I never use that mode at all, as flying 10° AoA and normally referencing the runway (or PAPI/ VASI) will get you there as well. " .... you are depriving yourself of some good info Brem You can use the F1 VV and reticle in the same way as an E bracket on the F18/F16

[HawkEXO]

Yeah agree.  The approach HUD is slick

[Bremspropeller]

2 hours ago, IvanK said:

"I never use that mode at all, as flying 10° AoA and normally referencing the runway (or PAPI/ VASI) will get you there as well. " .... you are depriving yourself of some good info Brem You can use the F1 VV and reticle in the same way as an E bracket on the F18/F16

Never really thought about it from that perspective, but as you mention it - makes perfect sense!

I'm just trying to keep it as much "raw data" as possible and not trying to fly the VV but keeping connected to the airplane.

[Snappy]

While we are at this topic, I have one more more related question:

While in normal mode , (not approach mode)the HUD pitch ladder  (while not necessarily aligned with real horizon as mentioned above ) seems to show accurately your airplane attitude when referencing the radar reference symbol, ie. for example putting the radar  reference on the 20 degree pitch up line exactly matches your gyro main attitude indicator showing you at 20 deg nose up.

The manual seems to agree and also says about the sight:

Attitude scale: the attitude reticle consists of a main bar (horizon) and marks (attitude scale) that move in roll and pitch with respect to the radar reference. When the normal attitude reticle is selected with the sight selector, the attitude reticle provides the same attitude indications as the spherical indicator, in a scale of 1/5 in pitch.

Now my question

Why is the radar reference symbol showing correct aircraft pitch values when compared against the spherical main attitude indicator, when the same manual also says :

Radar reference: it is composed of two horizontal bars and a vertical bar, it is set 5° below the fuselage reference line (FRL) and shows the radar line.

Shouldn’t the attitude , as seen on  the HUD  , be 5 degrees less than on the main ADI, since it is not showing the aircrafts actual fuselage pitch?

Regards,

 Snappy 

Edited June 29, 2023 by Snappy

[IvanK]

The manual is quite specific and states that the HUD Pitch reference and the Spherical indicator (in normal mode) display the same pitch value.

If you delve into the manual you will find a series of diagrams that show how this is arranged. Even though the radar Datum and the Gyro ref datum differ in their depression from the FRL the output to the Gunsight is corrected and delivered to the sight by the Roll/Pitch Multipler box (R/P OM). So the pitch attitude displayed on the Spherical indicator and the sight are in agreement. This from the publicly available manuals for the F1K50ED. So the assumption is the F1 in game is the same.

 

Edited June 30, 2023 by IvanK

[Snappy]

Hey, thanks a lot! I had only looked in the module manual for info about this.

But I see now that the real world manual contains much more in-depth information. 

kind regards,

Snappy