Multiple module Info guide Understanding compass, RI and DG

[Pikey]

I don't know about the rest of you, but as a frequent flier of most of the warbirds and an expert in precisely none, I was trying to understand why I always got inconsistent and confusing heading behaviors with the navigation equipment in the Warbirds. There are numerous topics with queries with the same root cause. Searching for bugs I sat down and performed tests on all the warbirds except the I-16. There are some interesting results to share, not least because it will help demystify how they are setup and used.

First of all, what tests did I do?
Air start, active pause, known heading - record the Radio compass (RI), the magnetic compass, and any Directional Gyro (DG) readings to compare.
Runway start - known runway heading (single player only) same as above.

Findings
In the image, green numbers are as expected and within tolerance, orange is where there is some doubt, and red is just crazy silly.
See the chart.

Generally, the golden rule is to never trust your DG at the start of a mission.
Rule 2 is that the RI's and German birds can't handle the three point attitude on the floor so are only reliable in straight and level flight. This may confuse on the runway lineup or during turns. You have to keep returning to wings level and trim to ensure a good reading.

Spitfire, Mosquito and P-47's DG's are set to 000 ish for air starts
P-51 DG is strangely set to true/grid north for some reason.

For runway starts in Single Player the DG is about as useful as a chocolate teapot, you need to set it yourself.

Idiosyncracies

Spitfire - the hardest of these planes to navigate because the lubber line is missing on the P8 compass, the parallax is so great and the viewing angle so poor that you are better accepting a well-tuned DG setting at take-off and ignoring the P8 which is a really sad thing for navigators. That said, even the parallax is at most causing 5 degrees of ambiguity, so it's not completely useless if your DG really goes wrong. The P8 can also be used in 3 point attitude unlike all the other compass types, so there is that! However, the cockpit restrictions do not allow you to put a view right over the P8, so you cannot in 2D easily validate the heading from directly above. Advice: If route planning use short hops and visual handrails like rivers, coastlines or population centers. Unique buildings aside.

Mosquito - The Mossie does have a lubber line you can read and the P8 is easier to read than the Spitfires, especially if you want to setup a quick view you can put the camera in the cockpit right over it. But, the RI is easier to read overall than the P8 as long as you are flying straight and level so is most likely superior. Just remember not to set the DG on the runway by using the RI, only the P8 initially, then after, the RI for accuracy. Since it's not actually a repeater of the P8, it's a separate system, it needs power and RPM too. The final note I did get some 4 degrees of error I couldn't work out which might be the classic modeling of interference all magnetic compasses are prone to. Planes, even recently were placed on a disc and checked against a known magnetic north direction. Here's proof of that P8 working in three-point pitch which most of the wheel and repeater types cannot do.

P-47 - DG is messed up on the runway start and shows something random. The compass is quite tricky to read with 4 degrees of variance you may need to zoom in. Setup your DG once airborne because of the high three-point pitch in the Jug and the wheel type of compass. The DG is fairly redundant given the readability is the same as the compass. This might mean you can use the DG to tune specific legs of a course to 000 giving a better 'at a glance' use when holding a heading.

P-51 - This has a decent RI but suffers from bank and pitch restrictions. it also seemed accurate on the runway lineup, until I realized that the P-51 is the only plane to line up a few degrees left for some reason (single player start from runway). The DG is also set to true north if you jump in the cockpit, unlike all the others. No idea why it's like that.

German planes - All identical behavior, only work in level flight and since there is no DG to tune, you are Gucci from the get-go. I would advise setting the heading ring to align with the thick lines - i.e. turn the outer ring to the heading you need then line up the North arrow. The reason for this is visually it's so much easier to glance at the alignment of the two thick lines than squint at the smaller lines and try to work out what actual number in degrees this equates to. Do the hard work once by setting the heading for the leg, then the easy part is just aligning the north arrow, exactly how the P8 works.

I-16 I didn't try but has a single magnetic "reel type" like the American standard with no DG.

So that's it, since we have a map, a ruler a compass rose with true and magnetic readings, its no longer possible to get confused between any conversions. Trust the compass!

 

Edited April 9, 2023 by Pikey

[jaydee]

Thank you Pikey. I am in the middle of Reflecteds Beware,Beware Campaign (loving it) and could not get my compass to match the heading in the Info Bar. Trying to Adjust it in Flight is not going to end well when you are over enemy territory and want to RTB !  So I have to turn on info bar to navigate . (not very realistic). Thanks mate, I thought I was doing something wrong.! ~S~