Question about Witches Hat// Harrier attitude at rest

[GinGin]

Good evening,

 

First all, a big thanks to Razbam for that nice Harrier. Top notch modelisation so far, and very good work with the fixes and following of the bug reports.

 

It is no really a bug I think, but I have some questions about the depressed attitude symbol.

It is written that it is located 8° below waterline, so 8 ° below X body axes at rest.

When on horizon and hovering, it gives the correct attitude for hover and it works well

 

So far no problem, witches hat is around 2° below horizon on the ground with a nose attitude at rest of 6° Normally And here come my question.

 

It is hard to see that rest attitude with intrusment on the ground, So I did it in flight.

 

Level flight, velocity vector on horizon and witches hat on horizon.

So it should give us an attitude of 8° , which we can read through the angle of attack equal to the pitch attitude in level flight.

 

Or I am reading 6° ( 5,5 on the screen, not a perfectly perfect straight line :) )

And confirmed on external view with the pitch around 6° instead the 8 expected with the witches hat on the horizon

 

 

 

 

 

 

 

 

Hope what I mean is understandable, no really a bug, but I maybe missing something.

Waiting for your inputs :)

 

And keep up the excellent work

[razo+r]

I don't know if that is a factor of what you are mentioning, but check your flaps.

[Dave317]

I wondered about this too. With the aircraft stationary on the tarmac should the stitches hat be in line with the horizon line in the hud?

[GinGin]

@ razor : good input, I will try. But I don't think it will change the outcome.

Flaps just change the speed for a given angle of attack basically. Outcome will be the same.

 

@ Dave :on ground the position is correct, around 2° below the horizon

So witches hat are at -2° on ground, which seems correct.

 

My guess is that rest attitude on ground is 4° instead of 6( placing the witches hat 6° below waterline instead of 8 )hence the 6° degrees of pitch attitude instead of 8 when in level flight with velocity vector and witches hat superposed

Edited December 7, 2017 by GinGin

[bart]

I wondered about this too. With the aircraft stationary on the tarmac should the stitches hat be in line with the horizon line in the hud?

 

 

Here's a really good clip of a GR7/9 HUD during landing at Cottesmore. Watch the "Witches Hat" during the landing and it's position after the aircraft touches down.

 

I can't explain it fully as I'm not 100% sure either! but the clip shows that the Witches Hat is around half way between the horizon line and the -5 deg on the HUD after touchdown.

 

Edited December 7, 2017 by bart

[Tango Lima]

I hope this can help you, sorry was my first flight and not my best one.

 

ZiIlt9Zi98Q

 

Regards

Tango Lima/Scorpion

Edited December 8, 2017 by Thomas Loeffelmann

[TonyZ]

Angle of attack has nothing to do with the levelness of the airframe. It is the angle between the relative wind and the chord line of the wing. It is not related to the witches hat at all. The aircraft wheels are arranged so that when the aircraft is 8 degrees nose up then both front and rear landing gear will touch down at the same time so that's why the witches hat is 8 degrees below the horizontal centerline of the fuselage and why the nozzles are set for 82 degrees when performing a vertical landing.By keeping the nozzles at 82 degrees and the witches hat on the horizon which equals to an 8 degree nose up attitude during descent then both wheels will touch down at the same time and thrust will be straight down and the AOA has nothing to do with it. Also the reason the witches hat is at 5.5 degrees or so on the ground is because with weight on the gear the front strut compresses and the nose settles downward a few degrees so the hat is now below the horizon line.

Edited December 8, 2017 by TonyZ

[GinGin]

I agree but when angle of attack is on the horizon , level flight , angle of attack equal pitch attitude which is 5,5 degrees in my screen

And moreover , witches hat is also on the horizon so We should read 8 degrees and not 6 degrees of pitch up

 

So now , we hover with witches on horizon at 6 degrees instead of 8, that is my guess

[Eldur]

Here's a really good clip of a GR7/9 HUD during landing at Cottesmore. Watch the "Witches Hat" during the landing and it's position after the aircraft touches down.

 

I can't explain it fully as I'm not 100% sure either! but the clip shows that the Witches Hat is around half way between the horizon line and the -5 deg on the HUD after touchdown.

 

 

That's the ~2° it comes down when resting on the gear. When sitting on the ground, it's AoA is indicated 2.7° (which is irrelevant as stated already, but just for completeness) and the external view pitch value is 2°.

 

 

 

Not even close to 6°...

 

That W indicator is "horizontal centerline of the fuselage", roughly at 2°. Witch hat appears 2° below horizon. Makes 4°, not 8°.

 

When sitting on the ground, as far as I understand, the W should be at 6° and the witch hat at -2°. When hovering everything +2°.

This comes to another interesting thing. Ever tried to gun AG? Notice how much you have to fly the TVV below the target to be able to hit it just like it's in the F-15C? Doesn't feel right for an AG aircraft though, risking to slam her into the ground half a mile short of the target just because you try to hit it with the Equalizer. We have to pull up very early or come in very steep and pull up really hard at the moment.

Edited December 8, 2017 by Eldur

[GinGin]

Hello Eldur, I think you get my point :)

 

There is something weird with the relation between witches hat and nose attitude at rest. We don't find the 8 degrees as described in manual .

 

Error is small around 2 degrees, so nominal operations and use of the witches hat is still very useful, but I would like to know from where the weird part is coming :)

[TonyZ]

If you read my previous post it tells you where the discrepancy comes from and again AOA HAS NOT A BLESSED THING TO DO WITH LEVELNESS OF THE Aircraft. I could be in level flight and still have my nose way above 5.5 deg of AOA since there are a number of factors that affect AOA including load, flap position, airspeed, thrust, winds, nozzle position...etc. point being that ..Who cares where the hat is pointing on the ground?...it's during landing before touchdown that matters.

Edited December 9, 2017 by TonyZ

[GinGin]

Hey Tony, take it easy, I read your post .

 

I know my basics with aerodynamics, so you don't need to yell that AOA has nothing to do with levelness , because of course it has . AOA, Pitch and slope are linked . So knowing one or two of them , you can deduce a third one

 

Pitch = AOA + slope

 

http://www.aeroskytech.com/english/firstnotions/anglesen.png

 

 

That's why in my screen I fixed the slope value to zero by putting Velocity vector on horizon, so Pitch equal AOA= 5.5

 

Witches hat is fixed at 8 degrees below the nose per definition, it's indépendant of all others factors.

So , in a stabilized flight with both hat and VV on the horizon like in my screen , we should read something around 8° Of angle of attack/ pitch and not around 5.

 

The whole point to be in level flight is to,have a direct reading of the pitch through the AOA, so don't tell me that AOA has nothing to do with levelness .

 

Maybe you don't care, but I do care to know from where it is coming.

 

 

Another real example ( check all the videos when Harrier is decelerating in level flight and hat cross the horizon, AOA hence the pitch is close to 8 or 9 like expected)

 

Look at that true HUD screen:

 

http://www.harrierpilot.com/apr02/hud2a.jpg

 

 

Level flight, no slope, AOA=pitch=7 and hat around 1 or 2 degrees below.horizon.

So if you put the hat on horizon still in level flight ( by decreasing the speed for example ) , you will increase your AOA/ pitch to 8 or 9degrees, as expected.

[Subferro]

Calm down, no one is trying to use the AOA to determine if the aircraft is level. All they're doing is using the AOA gauge as a way to measure the amount of depression of the of the Witches Hat. If the AOA gauge says 6º, then the VV should be 6º away from the aircraft chord (assuming the aircraft displays AOA in degrees rather than 'units', but that's another discussion). If the VV and Witches hat are overlayed, then you can use that to say the Witches Hat is also 6º away from nose.

 

 

As for the location of the Witches Hat, other than the Pocket Guide I can't find any documentation of where it should be. It doesn't seem to be specified in the NATOPS-000. But what I can find, is that in order for the nozzles to be straight down when at the 82º hover stop, then the Witches Hat should be at 6.5º:

 

The aircraft engine sits at an angle of 1.5º relative to the aircraft fuselage datum (that is in the NATOPS), thus at a nozzle angle of 0, the engines is actually angled down 1.5º relative to the aircraft. At a nozzle angle of 82, the engines will be at 83.5º (82+1.5) relative to the aircraft. To then point them straight down, the aircraft would need to pitch up 6.5º (90 - 83.5). Given that hovering involves putting the nozzles in the hoverstop and the witches hat on the horizon, I would assume that's actually the depression of the Witches Hat, which is more in line with what you're measuring in game. I could be way off with all this, but that's what I can deduce about all this.

 

 

 

EDIT: well I was ninja'd by another post. That image of the hud seems to negate what I was saying about the Witches Hat... I'll go back to brush up on my geometry :poster_oops:

Edited December 9, 2017 by Subferro

[GinGin]

Hello Subferro, for the definition of depressed attitude symbol, I got that one.

 

 

 

Very interesting stuff with engines datum, gonna look closer on that

[Subferro]

Ugh, thank you. I thought for sure it had to be in there but a Ctrl-F for Witches Hat wasnt finding it, obviously because they use the "depressed attitude" name in that section. I knew I was missing stuff on HUD symbology, but kept looking at the beginning of the document rather than closer to the end. Thank you for giving me more reading.:thumbup:

[GinGin]

No worries, took me time even with the search function :)

So yes, we should definitely read those 8 degrees ahah

[GinGin]

I tested differents scenario in depth and compared real HUD view, and for sure now, something is weird.

 

Hope Zeus or Captain Smiley could tell us more about that :)

Edited December 10, 2017 by GinGin

[GinGin]

Hello :)

 

Sorry to up the post, but still wondering why we have 5 or 6 degrees of pitch instead of 8 when witches hat are on horizon.

 

 

 

Another screen on Hover, witches hat on horizon, and 5 degrees of pitch.

 

[Terry Dactil]

I think we have to accept that the HUD is a dog's breakfast until this gets fixd.

(Along with the velocity vector not staying with pitch ladder and changing to vertical speed mode when <60kts).

[GinGin]

Hey Terry, It doesn't seem to be an issue with HUD, more with the inherent pitch attitude of the Harrier.

[Nealius]

Would this have anything to do with us having to use 84-degree nozzles for hover/VTOL? The NATOPS manual states 82 degrees for hover/VTOL, but I've noticed that doing so gives me forward movement with the Witch Hat on the horizon.

[GinGin]

Indeed it is linked in my opinion.

6 degrees for the hover attitude instead of the 8 we should have, hence 84 degrees of nozzle instead of 82 with witches on horizon works far better for me also.

[GinGin]

Good evening, quick note of what I observed since last update.

Very nice fixes on that one.

 

Attitude at rest seems far better, around 5 ° now( Nose strut less compressed than before) but witches hat are closer to the horizon line, weird.

 

 

Nose strut/ Attitude at rest

 

Last update

 

 

 

before last update( 2.2)

 

 

 

 

 

Witches hat

 

 

Before (2.2)

 

 

 

 

After last update

 

[fjacobsen]

It is not the witch hat that has moved. It is the pitch ladder that has moved due to change of attitude at rest.

Since the nose points more upward, the horizon line has dropped down accordingly.

Edited December 20, 2017 by fjacobsen

[GinGin]

Yep, so hat needs to be moved back to -2 degrees and it will be perfect :)

Edited December 20, 2017 by GinGin