Waypoint Confusion

[IvanK]

I understand the PVI800 can have 6 waypoints and 2 Airfields.

 

I have made a simple map consisting of 2 airfields and 3 Waypoints

 

AF1 ------WP1------------WP2----------WP3-----------AF2

 

Whilst sitting on the ground at Airfield 1 with the PVI WYPT button activated and the display mode DTA, the DH/DTA switch in the DT position.

 

The PVI800 shows Range and bearing to WYPT1, The HSI yellow Captains bars show the HDG to WYPT1 but the white needle remains fixed. If I then select WYPT2 the HSI white needle then spins to show the bearing to WYPT 2.

 

Why wont the needle show the bearing to WYPT1 ?

 

VARIATION

Given the Variation in the area is 5 East. The Magvar control is set to 5 ?.

If this is incorrectly set what error rs occur in the KA50 NAV system ?

 

The PVI800 works in true .... correct ?

If so the Brg on the PVI800 is in true ?

 

The HSI, HUD and ABRIS work in Magnetic ... correct ?

Edited January 9, 2009 by IvanK

[Frederf]

The white needle is the desired track angle needle so it won't necessarily point at the waypoint. It shows track angle, not bearing. Also I'm not sure if the DTA white needle on the HSI even functions when in the typical automatic mode. I would guess it aligns with the yellow captain's bars when you are on track but I don't know.

 

I would assume the magnetic variation knob only has an effect when dealing with true/magnetic conversions. I think the HSI is a magnetic compass-updated gyroscopic instrument so if the HSI is in true then the knob would affect the accuracy of the HSI.

 

The PVI is in... I don't know magnetic or true. I assume the wind data is entered in true (since that's what weather data is done in).

 

Manual time! *goes reading*

[IvanK]

Ok thanks for that Frederf that explains the white needles behaviour... I have worn the manual out :)

 

Ref INS fundamentally they all work in True. Most western installations then use a Magvar lookup table to correct their output for display on magnetic referenced displays. A cockpit switch then allows Pilot selection of either Magnetic or True for all heading references.

 

Changing the value of the BS Magvar knob does not seem to affect the HSI or HUD heading scale which agrees with Standby compass ... so are in magnetic..... methinks the knob has no real effect in the sim.

 

The next thing is what does the HSI use for a heading reference ? Given the KA50 has always had an Inertial system I would presume it gets its heading from the Inertial. Rather than a Magvar table I think this is what the variation knob is meant to be for. It would be strange if the HSI had its own slaved Gyro system. Whilst we are discussing this what does the main AI use as its attitude source ... Inertial as well ?

Edited January 9, 2009 by IvanK

[miguez]

Hi guys,

 

I just ran a quick test and the white pointer and the heading bug behaved as expected, which is different than you described above.

 

I set up a flight plan with 4 waypoints. THis means the PVI-800 would have 4 waypoints, and 2 airfields. I then fired up the simulation and sat on the ground at the origin airport. I cycled through all 4 waypoints with the PVI-800 in WPT mode, and the white needle swung to indicate the correct track, as per the flight plan, for each waypoint. It matched what the track was in the ABRIS. The heading bug swung to show the instantaneous heading to each of those waypoints, from my present position.

 

I am guessing where people might get confused is when they look at the white needle. It has nothing to do with your present position, it simply indicates the track value for the selected leg. By the way, all of the above was without messing with magnetic variations.

 

Let me know if you need more info.

 

Best regards,

[Frederf]

Miguez, do you happen to know what the mag. var. knob affects in sim/real life?

 

EDIT: Yeah the TA white pointer works fine except when navigating to WPT1. Since it uses the angle between WPs to calculate the track angle for the pointer. There is no WP0 so the track angle to WP1 is not defined.

Edited January 10, 2009 by Frederf

[IvanK]

I don't think BS uses Mag variation at all, regardless of what the manual implies. So far twisting the variation knob has no effect on any heading reference display in the cockpit.

 

In addition in the ABRIS settings you can set the ABRIS reference to True or Mag. I have done this whilst sitting on the ground and the ABRIS track display (i.e the numbers) remains the same. All that changes is the letter next to the displayed track from M to T. In addition the track displayed by the ABRIS agrees exactly with the heading displayed in the HUD, HSI and stby compass.

 

Based on this I suspect that the only heading reference used by BS is in fact True .... this goes for the Stby compass as well.

 

The alternative is that the in game Magnetic variation is in fact 0 though in the Kuban region it should be around 5.5 deg East.

 

Devs comment ?

[GGTharos]

While I'm not a dev, I will speculate that this might in fact be working, but it is waiting for a terrain engine it can work -with-. Just my guess. :)

[miguez]

Miguez, do you happen to know what the mag. var. knob affects in sim/real life?

 

EDIT: Yeah the TA white pointer works fine except when navigating to WPT1. Since it uses the angle between WPs to calculate the track angle for the pointer. There is no WP0 so the track angle to WP1 is not defined.

 

Hi Frederf,

 

I do not know if the mag var affects the sim. I am sure it works in the real Kamov, but suspect they may do a lot of flying in True due to their relative proximity to magnetic North, which might induce some pretty large differences between airports/waypoints.

 

I agree with you, the track needle (white) in the HSI does not know what to do before waypoint 1. This seems wrong. In real life you'd think the system would have some workaround for this.

 

Thanks for helping track this down!

[Frederf]

If I was the Kamov Design Bureau I would make the PVI DT track needle for WP1 be the track between APT1 and WP1 since that is typically done in flight plans. Also I would have WP6-APT2 be the determining two points for the track angle when setting APT2 as the current waypoint.

 

When you say "I am sure it works in the real Kamov" I want to know... what does it really do. When is it referenced? What systems does it affect?

[miguez]

Hello Frederf,

 

These are all assumptions, since I have no real-world Kamov information, but based on every other aircraft I have worked with/on, the magnetic variation input affects the HSI and its needles, and the HUD, as well as everything else that shows heading or track, such as the ABRIS, with the exception, of course, of the magnetic compass, as that is always isolated from other systems, basically a "pure" indication of the local magnetic field.

[IvanK]

Most western INS equipped Airliners have a MAG TRUE switch that allows the pilot to select which Heading refrence he wants to use for the displays. You can quite happily select this in flight.

[Frederf]

Most western INS equipped Airliners have a MAG TRUE switch that allows the pilot to select which Heading refrence he wants to use for the displays. You can quite happily select this in flight.

 

The ABRIS has the preference setting like this (I think) but this knob doesn't really control what's displayed, moreover it sets the angular difference between the two for the benefit of converting magnetic heading information into true heading information.

 

However I guess if set the Mag Var knob in the Ka-50 to 0 then would display magnetic heading where normally there would be true.

 

Hello Frederf,

 

These are all assumptions, since I have no real-world Kamov information, but based on every other aircraft I have worked with/on, the magnetic variation input affects the HSI and its needles, and the HUD, as well as everything else that shows heading or track, such as the ABRIS, with the exception, of course, of the magnetic compass, as that is always isolated from other systems, basically a "pure" indication of the local magnetic field.

 

I happily accept your musings on the subject. Reasoned conjecture is often surprisingly accurate when later compared with "book fact." Half of what I say on this forum is conjecture stated as fact!

 

I'm trying to think what are the systems in the Ka-50 that use heading info:

 

1. Internal mag compass sensor

2. INU

3. PVI wind info (pre-flight entered in true?)

4. HSI

5. ADI

6. Shkval

7. INU update

[IvanK]

Anything working off the Inertials doesn't need Magnetic. INU update would only use relative bearing/laser range to measure the fix position this then applied directly to the INU calculated position its a straight Trig problem.

 

Shkval use is the same it has no need to know magnetic bearing, everything the Shkval does is relative to the BS itself.

 

The only real reason Magnetic heading is required is the ATC system still works in Magnetic, some navigation aids (VOR/TACAN) have a magnetic correction set in the station itself.

 

All INS systems think in True, Magnetics are only required as a downstream process for pilot display.

 

Magnetic Variation in BS just doesn't work. Either the BS world has 0 variation (my hunch) or the whole magnetic variation module in BS is bugged. As I stated in a previous post whether you have ABRIS in True or Magnetic the heading it displays is always the same. The MAGVAR knob has no effect on any display in BS.