Clod Revision - Setting Compass& D/f In Raf Fighters

[DD_Fenrir]

Another refresher for those who need some reminding of how to set your compass and direction finder in the RAF aircraft in CloD:

[CaptJackG]

Fenrir I use a little different procedure for navigation with the RAF aircraft. I look at the map and estimate the desired course I need to fly and put that in my course setter. I do not use the DG (Directional Gyro). This is a gyro that requires the AC to be running in order to operate and it precesses and tumbles when maneuvering. When I takeoff I turn the aircraft until the magnetic compass needle lines up with my course setter, the t of the needle pointed to north on the course setter. When in flight I'll look at the mag compass and if the needle has moved off of north I'll correct it back to north on the course setter. When correcting just think of the compass needle showing you which way to turn. If it is left of my course I'll turn left to bring back to on course.

 

Another thing trying to use the DG it has to be reset during flight and that can only be done when flying straight and level which can be hard to do when your looking down at the compass and your trying to align the course setter to the compass needle and the next thing you know your in a turn and your needle is moving.

[BluBear]

I will try both methods, but it will probably go wrong haha.

Thankfully I should be able to rely on my local knowledge, unless deep over France...

[slicker55]

Thanks Fenrir for putting this tutorial up...  I've just watched the other one  on 'Take-off & Landing' .. these really are great resources for newbies like me and are very much appreciated. I have been practising the method used in the above tutorial (Snacko covered this method in a recent 'training' session with me).

 

CaptJack, thank you for taking the time to explain your preferred method - I'm looking forward to trying it out... many thanks to you sir.

[Painless]

Watched and digested, thanks Tom.

[Snacko]

I'm glad you posted that Jack.  After our little class in this the other night, I thought you did use the DG to navigate.  And that we just pointed our airplanes north so you could show me something as an example.  Now that makes sense.

 

Now I'm wondering why you showed me how to set the DG?  Maybe that was the example?      Either way, I get your point about using the CS.  

 

Why does't the CS get screwed up when we make wild turns?  Because it has an actual magnetic compass and the gyro only has a gyro to hold it on point?

[CaptJackG]

I've watched the compass in Clod and it behaves like a real compass.

 

The DG is a gyro which I'm pretty sure they used a vacuum system to spin the gyro. The gyro gives you rigidity in space, you cage the gyro, set your heading in reference to your mag compass, and uncage the gyro. Now when you turn, because the gyro maintains the same position it appears that your dg turns when in reality you are just moving the ac around the gyro. The problem with gyros are they precess, they will slowly move off your original heading reference. They also can be tumbled due to wild maneuvers. So you have to reset them using the mag compass.

 

The magnetic compass in the RAF is the round dial mounted like a ships' compass. The t needle mounted inside always points to N (just like the little compass you use to get in a Cracker Jacks box). The Course Setter part is the mechanical outer dial you can rotate with the red N indicator.

 

So why not use the mag compass all the time. It has errors that have to be understood. There are turn errors, lead/lag. Lead to the south lag to the north. How much lead/lag depends on your latitude, London being 51 degrees N. So if I'm making a turn to the N say from the SW (230 to 360) when I'm at 360 the mag compass will be lagging 51 degrees behind or 309. If turning to the S the compass when I'm on 180 with be leading 51 degrees ahead of me depending on the direction of turn. So you need to be straight and level when reading the mag compass. I also think, but no absolutely sure  that ANDS is also modeled in Clod, Accelerate North Decelerate South. When on a E or W heading if you accelerate the ac the compass will swing N and if you decelerate the compass will swing S.

 

So with those errors in mind, most normal flying from point a to point b you would set your DG and use that for primary heading ref keeping in mind that you have to reset it about every 15 minutes due to normal precession. And you always make sure you're in stable flight to get a good mag compass reading.

BUUUUUUUUT since we're in a high performance fighter plane and the first turn after takeoff is usually done at about 70 to 90 degrees of bank we immediately tumble the DG, then we have to get back straight and level to reset the DG making sure were not turning while setting. So just remember that the Course Setter is mechanical and does not move except by you mechanically setting a course. The compass t needle inside you can not control as it always points to magnetic north so you have to fly the plane to a new heading to make the compass needle point to your desired course.

 

I've just found it easier to navigate in Clod with the course setter set to my desired course and then I fly the plane to make my compass t needle line up with N on my course setter instead of trying to reset the DG continuously.

 

We'll save a discussion on magnetic variation for later.

[BluBear]

Woooooooooooooooooooooosh!

That was the sound of all that flying over my head (admittedly after a few drinks!)

I sure am glad that i'm a local and can, to a certain extent rely on landmarks etc for navigation.

 

Thanks for the in-depth analysis CJack, I shall try to put it to practice at some point!

[Snacko]

I think I got most of that Jack.  

 

Just to I understand.  When you say:

 

So if I'm making a turn to the N say from the SW (230 to 360) when I'm at 360 the mag compass will be lagging 51 degrees behind or 309. If turning to the S the compass when I'm on 180 with be leading 51 degrees ahead of me depending on the direction of turn. So you need to be straight and level when reading the mag compass.

 

This lag is only temporary until you return to straight and level flight.  It only happens when you are in the turn?  After the turn the T returns to North, right?

[CaptJackG]

Correct, ie if you are on a steady 360 heading and the compass is showing 360 and you start a right turn to 090 the compass will jump behind you 51 degrees but as you turn it will catch up until at 090 it will indicate 090. If you continue the turn to 180 the compass will start to lead ahead of you until when you reach 180 degrees it will be 51 degrees in front of you showing 231 degrees. So you roll level when the compass indicates 231 and it will then return to 180 degrees when you are level.

 

This 51 degrees I use here is for the latitude of London. If you were on the Equator there would be no lead/lag error. If you are at the poll the compass will just be pointing straight down, pretty much becoming unusable.

[slicker55]

Thanks CaptJack...

 

My wife says this is crystal clear!

 

[T_O_A_D]

Thanks!

[Jabo]

I look out of the window, note the position of the sun as I take off so if I get separated from the formation I can find my way home by working out a rough heading and before that happens I use the compass to sort my heading according to what I can see outside, seems to work for me, the less time spent with my head in the cockpit so much the better for situational awareness.

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[BadAim]

I prefer to let smarter people do the navigating; I just follow them. Should I get lost, I just watch for something that looks English, land there, have a cup of tea and ask for directions.

 

Simples