Why is True North heading not the default for the HUD?

[imacken]

Just wondering why the HUD doesn't default to using true North heading. Instruments like the radar use it for the BRA info, so why the confusion?

I know there must be a good reason!

[=475FG= Dawger]

Just wondering why the HUD doesn't default to using true North heading. Instruments like the radar use it for the BRA info, so why the confusion?

I know there must be a good reason!

 

Navigation is done in reference to magnetic north and the airplane spends most of it time in navigation.

[imacken]

I get that, but I'm asking why!

Is it just for historical pre-GPS reasons that planes navigate to magnetic?

Is there a reason why certain instruments show true data and others magnetic?

[Flamin_Squirrel]

I get that, but I'm asking why!

Is it just for historical pre-GPS reasons that planes navigate to magnetic?

Is there a reason why certain instruments show true data and others magnetic?

 

As far as I'm aware (at least in civil flying) everything is referenced off magnetic heading (there will be occasional exceptions, e.g. flying at high latitudes).

 

The reason for this is you want all your instruments to crosscheck, including against your trusty standby magnetic compass.

 

Does AWACS really issue headings in true (in reality)? If so, the question I'd be asking is why do AWACS do that.

[imacken]

As far as I'm aware (at least in civil flying) everything is referenced off magnetic heading (there will be occasional exceptions, e.g. flying at high latitudes).

 

The reason for this is you want all your instruments to crosscheck, including against your trusty standby magnetic compass.

 

Does AWACS really issue headings in true (in reality)? If so, the question I'd be asking is why do AWACS do that.

 

Makes sense.

 

If you look at the BRA data on the radar, and put the TDC over your position (centre line) you will see that it is in true bearing not magnetic.

[Flamin_Squirrel]

If you look at the BRA data on the radar, and put the TDC over your position (centre line) you will see that it is in true bearing not magnetic.

 

Oh yeah I don't doubt you; I was just wondering if this was correct (as in, if it's not a bug and the real plane is like this) and if so it would be interesting to know why.

[imacken]

Oh yeah I don't doubt you; I was just wondering if this was correct (as in, if it's not a bug and the real plane is like this) and if so it would be interesting to know why.

 

Indeed. Let’s hope someone who knows will comment here?

[=475FG= Dawger]

Magnetic north is detectable by the aircraft. True north is not. It is that simple.

 

GPS is not as reliable a source for a reference point as magnetic north.

[QuiGon]

INS aligns to true north reference. How it's not detectable?

Ture, but not all aircraft have INS though.

[AvroLanc]

INS aligns to true north reference. How it's not detectable?

 

My Cessna 172 doesn’t have an INS.

 

 

Aviation uses Magnetic Headings for navigation output and ATC. It’s just how it works. Everyone needs a common reference.

[=475FG= Dawger]

INS aligns to true north reference. How it's not detectable?

 

I guess I should say detectable while in motion.

 

INS is a dead reckoning computer as soon as you start moving and subject to large error over time.

[AvroLanc]

This is F-18 forum - we are talking about F-18. The aircraft position is referenced to true north. Magnetic compass is just standby instrument, it doesn't connect to anything.

 

If user interface is set to magnetic reference it should be consistent through all menus and information displayed.

 

That’s not how flying works. You can’t have a bunch of airspace users flying around on Mag headings or tracks and a bunch of others on True. There needs to be a common standard, and it’s Magnetic. Both for historic and practical reasons.

[Flamin_Squirrel]

This is F-18 forum - we are talking about F-18. The aircraft position is referenced to true north. Magnetic compass is just standby instrument, it doesn't connect to anything.

 

If user interface is set to magnetic reference it should be consistent through all menus and information displayed.

 

Default HUD readout is magnetic IIRC.

[imacken]

We’re talking about the Hornet, and I guess the basic question is why is there no consistency in how data is presented?

[=475FG= Dawger]

We’re talking about the Hornet, and I guess the basic question is why is there no consistency in how data is presented?

 

It is consistent with standard international aviation practices.

[Lex Talionis]

This is a case where context is important. Keeping in context with how navigation and aviation evolved:

 

It wasn't untill the implementation of GPS that the oldest and most practical means of orienting to a map was by magnetic compas. (Celestial for you really old guys).

 

All navigation grew from magnetic orientation thus all navigation instrumentation reflects this. Even with GPS, If systems were to fail in the aircraft, navigation will ultimately degrade to magnetic. This is also why all IFR certified aircraft must still have that archaic wet compass installed somewhere in the cockpit.

 

When all one knows is a game with an F10 map that gives instant and absolute situational awareness, it is easy to wonder why that should not be what the aircraft is designed to associate its navigation instrumentation with. Its just not how it is in real life. Vary rarely if at all is true used in an aircraft.

Edited October 1, 2019 by Lex Talionis

[Txshooter38]

This is a case where context is important. Keeping in context with how navigation and aviation evolved:

 

It wasn't untill the implementation of GPS that the oldest and most practical means of orienting to a map was by magnetic compas. (Celestial for you really old guys).

 

All navigation grew from magnetic orientation thus all navigation instrumentation reflects this. Even with GPS, If systems were to fail in the aircraft, navigation will ultimately degrade to magnetic. This is also why all IFR certified aircraft must still have that archaic wet compass installed somewhere in the cockpit.

 

When all one knows is a game with an F10 map that gives instant and absolute situational awareness, it is easy to wonder why that should not be what the aircraft is designed to associate its navigation instrumentation with. Its just not how it is in real life.

 

 

Sorted. -Mic Drop-

[Flamin_Squirrel]

So, if you want BRA to be consistent, go to HSI > DATA > A/C > PB 13. That will set everything to true north. It's useful because everything in DCS is set to true north, even FC3 aircraft.

 

It won't set the standby compass to true north though :music_whistling:

[QuiGon]

This is a case where context is important. Keeping in context with how navigation and aviation evolved:

 

It wasn't untill the implementation of GPS that the oldest and most practical means of orienting to a map was by magnetic compas. (Celestial for you really old guys).

 

All navigation grew from magnetic orientation thus all navigation instrumentation reflects this. Even with GPS, If systems were to fail in the aircraft, navigation will ultimately degrade to magnetic. This is also why all IFR certified aircraft must still have that archaic wet compass installed somewhere in the cockpit.

 

When all one knows is a game with an F10 map that gives instant and absolute situational awareness, it is easy to wonder why that should not be what the aircraft is designed to associate its navigation instrumentation with. Its just not how it is in real life. Vary rarely if at all is true used in an aircraft.

Great answer! :thumbup:

 

That makes me wonder about celestial navigation though: Stars are not aligned to magnetic north, are they?

[Flamin_Squirrel]

I thought that DCS World 2 engine introduced curvature?

[Hog_No32]

This is a case where context is important. Keeping in context with how navigation and aviation evolved:

 

It wasn't untill the implementation of GPS that the oldest and most practical means of orienting to a map was by magnetic compas. (Celestial for you really old guys).

 

All navigation grew from magnetic orientation thus all navigation instrumentation reflects this. Even with GPS, If systems were to fail in the aircraft, navigation will ultimately degrade to magnetic. This is also why all IFR certified aircraft must still have that archaic wet compass installed somewhere in the cockpit.

 

When all one knows is a game with an F10 map that gives instant and absolute situational awareness, it is easy to wonder why that should not be what the aircraft is designed to associate its navigation instrumentation with. Its just not how it is in real life. Vary rarely if at all is true used in an aircraft.

 

Funnily though, in all commercial aircraft equipped with an FMS (which are 99.9% these days), lateral guidance is indeed done in true north. The FMS converts coded magnetic courses (depending on the ARINC 424 Path Terminator used) into true north courses because that is the reference system which is used by the INS. For the conversion there are a bunch of different sources for the magnetic variation, it could be table in which the world magnetic model is stored (updated every 5 years) or the magnetic variation of an airport or the station declination of a VHF Navaid. But that is a whole different discussion... :music_whistling:

[tom_19d]

Funnily though, in all commercial aircraft equipped with an FMS (which are 99.9% these days), lateral guidance is indeed done in true north. The FMS converts coded magnetic courses (depending on the ARINC 424 Path Terminator used) into true north courses because that is the reference system which is used by the INS. For the conversion there are a bunch of different sources for the magnetic variation, it could be table in which the world magnetic model is stored (updated every 5 years) or the magnetic variation of an airport or the station declination of a VHF Navaid. But that is a whole different discussion...

 

-The US commercial fleet isn't close to 99.9% FMS equipped, you won't find a source anywhere to back that. GPS and WAAS equipage rates are growing quickly as the ADS-B mandate approaches but GPS/WAAS does not an FMS make.

 

-Of all the commercial aircraft in service in the US equipped with FMS, a minority of them have an INS.

 

-Regardless of how the navigation system generating the course guidance arrives at its solution, it will be displayed for the pilot as a magnetic course overlaid on a magnetic heading instrument (this is true whether it is a conventional HSI, a digital projection of one in a glass cockpit, or even a basic DG and OBS head combination). One of the first things fledgling pilots learn about ded reckoning navigation is how to calculate a magnetic heading between two points; first a true course is measured off a chart, then it is adjusted for magnetic variation, wind, and possibly magnetic deviation to arrive at a magnetic heading to fly that will yield a given magnetic course (and ground track by extension). Whether done by hand with paper or in the background by a computer, the pilot is still not referencing true north in any way when actually airborne; he or she sees the world in reference to magnetic north.

 

Which brings us back to the OPs point: it is indeed strange and not realistic that BRAA calls from AWACs are given in reference to true north. After so long in this game I just unconsciously subtract 7 from any bearing given by an AWACs, and when I MP as GCI I convert into magnetic before transmitting (after telling the players all my calls will be in magnetic degrees and nautical miles of course). Perhaps the long awaited ATC upgrades will help this long standing issue.

[Hog_No32]

First off, where in my post did I say that pilots are exposed to true courses? I said it is the aircrafts navigation system that needs a true course, not the pilots.

 

Also, I‘d love to hear of a single aircraft (type) that flies these days that has an FMS or RNAV navigation system or however you want to call it AND that does NOT have a form of an INS.

 

And I really don‘t get where your guesstimates are coming from. I was talking about commercial aircraft of which Boeings and Airbusses and Embraers and Bombardiers are making up the vast majority. There is not a single Airbus or Boeing plane these days without an FMS or INS.

 

What are your sources?

[tom_19d]

Also, I‘d love to hear of a single aircraft (type) that flies these days that has an FMS or RNAV navigation system or however you want to call it AND that does NOT have a form of an INS.

 

CRJ 700. Want me to keep going? Because I will just keep rattling off RJs... By and large the RJ fleet isn't going to have an INS, they are completely unnecessary for domestic operations and just add weight.

 

I was talking about commercial aircraft of which Boeings and Airbusses and Embraers and Bombardiers are making up the vast majority.

 

In that case you are talking about the Part 121 fleet (14 CFR has very specific definitions for all of these terms which are helpful to avoid misunderstandings). Yes, there will be more INS equipage in the Part 121 fleet than in the combined air carrier fleet as a whole, but given the large market share of RJs, INS equipped aircraft are not nearly as prevalent as you seem to think. Fedex, for example, is 100% INS equipped but that is only because they like to keep their whole fleet legal for ETOPs/International. This isn't the case for regional airlines flying smaller equipment on domestic routes.

[Hog_No32]

CRJ 700 does not have an inertial navigation system? Are we talking about the regional jet built by Bombardier and which has a Collins Aerospace (former RockwellCollins) provided Pro-Line-4 cockpit suite and the FMS4200? Because that has two redundant INS...

 

Anyway, this gets pretty much OT here...