R.I. Compass Repeater

[Nereid]

What should the R.I. Compass Repeater display? Magnetic heading? So it is linked to the compass or it has its own? Or should it display true heading? Then how it is adjusted?

And currently it displays neither. Not true heading nor magnetic heading but it is always a bit off. A bug? Or is it working as it should?

Edited November 20, 2022 by Nereid

[DD_Fenrir]

It's used exclusively for getting bearings to specific Radio Navigation Beacons; unless you (a) have one set for a specific purpose in mission or (b) know an airfield you wish to navigate to that has a beacon and tune accordingly, it's next to useless for any other navigation.

In reality you'd reset the P8 compass (below and in front of the throttle quadrant) after a turn point and use that to correct your Direction Indicator (centre of your instrument panel) and fly off that, updating the DI every 15 minutes in case of drift.

[Bozon]

On 11/20/2022 at 12:57 PM, Nereid said:

What should the R.I. Compass Repeater display? Magnetic heading? So it is linked to the compass or it has its own? Or should it display true heading? Then how it is adjusted?

And currently it displays neither. Not true heading nor magnetic heading but it is always a bit off. A bug? Or is it working as it should?

 

The Remote Indicator repeater is electrically connected to a “remote” compass unit (I don’t know where it was installed) and “repeats” its reading. Therefore it is a magnetic reading - our unit does not have the ability to add a true north correction.

The P8 compass is a different instrument that is a reliable backup - for example, electric problems will cause you to lose the RI repeater. Since both measure magnetic heading they are “supposed” to show the same heading, up to possible issues with interferences for which P8 is more sensitive (I don’t believe DCS includes that). Note that since P8 is located low next to your left knee, you are observing it from a funny angle. You need to move your perspective to get a proper reading. I will not be surprised if there is a bug and they don’t show the same heading - I never look at the P8 due to its location.

[Nereid]

3 hours ago, Bozon said:

The Remote Indicator repeater is electrically connected to a “remote” compass unit (I don’t know where it was installed) and “repeats” its reading. Therefore it is a magnetic reading - our unit does not have the ability to add a true north correction.

Thanks. So the P8 is just a backup. That explains a lot - and it's a pain in the *ss to read it.

On 11/30/2022 at 5:04 PM, DD_Fenrir said:

It's used exclusively for getting bearings to specific Radio Navigation Beacons; unless you (a) have one set for a specific purpose in mission or (b) know an airfield you wish to navigate to that has a beacon and tune accordingly, it's next to useless for any other navigation.

So what is correct? Is the compass just a backup ore the main source for a heading? I'm confused now...

[Bozon]

2 hours ago, Nereid said:

Thanks. So the P8 is just a backup. That explains a lot - and it's a pain in the *ss to read it.

So what is correct? Is the compass just a backup ore the main source for a heading? I'm confused now...

Look here, I think this is supposed to be similar to what the mosquito has, but I don’t really know. They say this unit was typical for RAF bombers:

https://rochesteravionicarchives.co.uk/collection/navigation-inertial/distant-reading-dr-compass-mk-1
 

Apparently this unit has a variation correction on the main unit, probably adjusted on the ground before the flight.

[Nereid]

On 12/1/2022 at 7:53 PM, Bozon said:

Apparently this unit has a variation correction on the main unit, probably adjusted on the ground before the flight.

Seems we have to wait for an after early access manual...

[Holbeach]

The RI unit is a repeater for the Electrical Magnetic Compass, down on the left, (wrong), remotely located, which is used in conjunction with a gyro which feeds the repeater placed on the panel where it is easy to read.

Part of the pre T/O checks is to align the Gyro DI to the Main Compass, then check the DI to the RI Compass as a cross reference.

These will be checked again during taxi to make sure they stay in line.

It has a course setter, to help read a pre set course such as runway approach or cross country route. (All Magnetic).

. 

Edited December 5, 2022 by Holbeach
Made corrections.

[Bozon]

17 hours ago, Holbeach said:

The RI unit is a repeater for the Magnetic Compass, down on the left, placed on the panel because it.s much easier to read.

Part of the pre T/O checks is to align the Gyro DI to the Main Compass, then align the DI to the RI Compass as a cross reference.

These will be checked again during taxi to make sure they stay in line.

It has a course setter, to help read a pre set course such as runway approach or cross country route. (All Magnetic).

The elecrical output from the main compass, would also be used for an autopilot, if it had one. E.G. V-1.

I can’t find any indication that P.8 compasses had an electric input/output of any sort, for a remote indicator or otherwise. It seems that it was just a compass.

This site mentions the use of P.8 as a check for aircraft with a remote indicating compass:

Quote

The grid steering compasses (Type P8 to Type P11) were fitted in World War II era aircraft. They were used for course setting and reading, and as a check compass on aircraft fitted with a remote indicating compass.

https://saskaviation.ca/aircraft-grid-steering-compass-type-p8/
 

Another site mentions a compass and repeater on RAF bombers. They refer to the whole system (main unit and remote indicators) as “distance reading compass”. I can’t copy&paste from that page so just scroll down to “D.R - Distance Reading” section title:

https://compassmuseum.com/aero/aero.htm
They mention that the main unit feeds compass reading to the bomb-sight for the bombers. Since the mosquito was designed initially as a bomber I suppose that FB.VI shares this compass unit with the B models.

So, from what I could find it seems most likely that the RI repeater has nothing to do with the P.8 compass, and it has its own main unit installed remotely.

It is the internet so grab a fistful of salt, but this is all I could find.

[Terry Dactil]

6 hours ago, Bozon said:

So, from what I could find it seems most likely that the RI repeater has nothing to do with the P.8 compass, and it has its own main unit installed remotely.

Exactly.

They are two entirely separate systems. Each has different advantages and disadvantages.

• The P8 compass does not require any power, but is in a terrible magnetic location with nearby metal objects ans varying electrical circuits. There will be a card nearby listing the corrections (the deviation) to apply to get the actual magnetic heading from what you see on the P8 compass.
• The remote compass requires power, but is in a much better location out on a wingtip or in the tail somewhere where any deviation errors do not vary and can be permanently corrected. Hence what you see on the indicator in the cockpit is the real magnetic heading and does not need correcting.

Basically, the RI is the one to use until you get shot up and lose electrical power, then the P8 (commonly called the "standby" compass) will get you home.

 

[Holbeach]

Is this what we require?

RAF DR.

As you say, it's a completely independant system from the P8 magnetic compass.

Mine shows 26 deg difference from the mag compass? (W - E).

I was expecting them to all read the same, (apart from deviation)..

..

 

 

Edited December 6, 2022 by Holbeach