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How in the World do you Read a Whiskey Compass?

L

Lionheart

SOH-CM-2014
Hey all,

For you guys that know how to read a Whiskey Compass, what is your secret?

For years, since I was a kid, I have flown with family, become a FS FREAK, and have logged many hours with planes (in FS and some in real world) that have Whiskey Compasses, and still I cannot figure out how to calculate 90 degree turns, etc. My mind goes blank. Is there a secret that enables you to visualise the compass disc? Or do you at one point just 'click' with how to read it?



Bill
 
I take it you mean the 'floating ball' type Bill and not the 'flat type' compass used in terrestrial navigation?

I personally don't have a problem with them. If I know my heading I know which way I have to turn to get to a new heading. Having said that I suppose I do a transposition in my head as I mentally 'see' a regular flat compass and know if I have to turn left or right. Once I know which way to turn it's just a matter of watching for the required number/line to appear in the centre. The only thing thats a bit confusing at first is the fact that the numbers run the opposite way to normal and it appears to rotate in the wrong direction.
 
A left turn will always "decrease" the numbers. A right turn will always "increase" the numbers. I mentally add or subtract the numbers. It is easy on a flat card DI or HSI. less so with the whiskey compass.

If you are flying an airplane with only a whiskey compass, use a compass rose. You will find one on any sectional with VORs. If you are flying an airplane with JUST a whiskey compass, you should have a sectional of the area with you.
 
I think that a whiskey compass is somewhat counter intuitive when you first use it. Just remeber that the floating ball or disk inside the unit does not turn to any degree and keeps its magnetic north orientation at all times. The plane revolves around the compass. Once you have accepted that, it is easy to fly by or boat by the whiskey style compass.

Magnetic compasses indicate the magnetic field of the earth and not true, grid or polar north. Depending where you are, you will have either an easterly or westerly declination between magnetic and true north and it can vary from a degree to over 25 degrees. FS and CFS both have built in magnetic declination that is reasonably accurate, so always check a magnetic declination map before flying any long distance on just your magnetic reading. You could miss your target by more miles than you care to if you don't convert your magnetic readings to keep you oriented to your true or map azimuth.

Many military tactical maps have a "Declination Diagram" in the marginal information that indicates the difference at the location of the map at the date that it was surveyed or published. The magnetic pole is constantly changing, so older map info may be somewhat suspect for accuracy by a degree or two.
 
Use your ball and slip indicator to give you the correct bank angle for a standard rate turn, then use your clock or timer. 180 degrees should about a minute so for a 90 degree turn should be about 30 seconds at standard rate. So what you do is start straight and level, note your heading, note time/start timer, smoothly enter standard rate turn, about a second or two before the desired time, begin a smooth rollout and you should be pretty close to your desired heading.

So we know 30 seconds is about 90 degrees and then logically 3 seconds would be about 9 degrees To make minor 10 degree corrections, I was taught to bank to desired side, count 3 seconds and roll out and it works out about right.

There is another effective way that escapes my mind at the moment, perhaps Ken or James might know this one, it has to do with a forumula by taking the local deviation. OSUN....Overshoot South, Undershoot North...I cant quite remember the forumla off hand but it was really handy. Basically it would tell you by how many degrees to over shoot or undershoot when rolling on to a desired heading. I vaguley remember the Prescott area being about 30 degrees under/overshoot for north and south, then 20-10 as you got closer to East/West. So if you were flying East and wanted to turn north, you would bank left, watch the mag compass until it hit 30 degrees and roll out. If you were flying East and wanted to turn to South, bank right, watch the mag compass until it hit 210 then roll out. I remember practicing on FS at the time and it seemed to match.

Cheers
TJ
 
Its not easy, is it, lol...

Thanks for the input gang. I'll keep working at it.

Knowing which way it turns and increases/decreases does help. Thanks for that JMIG. I had never really noticed that. I guess thats why I could never picture it correctly in my mind was that it is opposite in design and turns/moves opposite from which it actually should turn, a mirror reflection of a Card compass.

You gotta love those Card compasses....


Bill
 
math:
left=X - 100 + 10
right=X + 100 - 10
(degrees for the 90 deg turn)
(substitute base course for 'X'), if I'm feeling REALLY good that day,
Left=X + 270
Right=X - 270
:p
 

“Compass arithmetic“ has always been a pain for me too. Military pilots can do it quickly, as they have to mentally calculate intercept headings based on limited information presented on a radar display. For example, you're going 315 degrees. Target on radar is displayed 25 degrees left of your nose, with a “target aspect” (TA) of 40 degrees LEFT. (TA is the relative bearing (left or right) YOU are FROM the target heading). So, which heading must you fly to be on an intercept course...? The pilots drill these problems constantly so they can quickly determine the right answer. Amazing! The newer radars, like in the FA-18, solve some of the math for you, but in the “olden days” of the F-14, the aircrew had to figure that out in their head, fast, for each target.
 
Faculty in the aviation program at the university here indicate that the arithmetic (mostly ratios and some trig) needed is often hard for beginning students. This includes mechanics, ATC, pilots, and the aviation management programs.

Multiple pilots (one civilian background, and one military background) here have recommended the book Mental Math for Pilots (ASA publication). There are no shortcuts in the book, just the admonition to practice basic calculations.

Compass arithmetic isn't any harder the clock (12 hour) arithmetic, we just don't practice it as much (not required in kindergarten).
 
oops,

remember North Lags, South Leads.....On a Northerly a turn to either East or West will result in a lag on the compass -- how much depends on the declination (in Florida it's about 30 degrees). Southerly heading turn to the East or West the compass will lead you in the turn. Bottom line, you have to adjust your turn to come out right (turning to 150 from 200 you will need to stop your turn around 180 if you're flying around Orlando). Flying due East or West, the compass will track your turn as long as it's a consistent turn.

Declination is on the charts...East is Least, West is Best (an Easting means less declination in the Western Hemisphere, a Westing means more declination). In Florida, we are between -3 and -5. This makes sense if you think of where the magnetic pole is versus the actual pole.
 
Well, It's not that hard after a little bit of practice. PRB, I'd be very shocked to find out that F-14s didn't have gyros since they had some of the world's first microprocessors to calculate wingsweep, and there were jillions of other aircraft with gyros by that point. Every pilot should be able to do it with ease before recieving their instrument rating, it's the stuff that failed gyro or 'partial-panel' flying is made of.

in the two piper warriors I flew for my instrument rating, we used 30 degrees. I'm sure I'll screw it up, but I think West and East were reliable for rollouts; we overshot north by 30 degrees and undershot south by 30 degrees.

Also mentioned were the timed turns. At standard rate, it should take 2 minutes to peform a 360 degree turn. Even in rough air, you should be able to nail timing your turns and reading the whiskey compass before you're ready to fly IFR by yourself.
 
tigisfat said:
Well, It's not that hard after a little bit of practice. PRB, I'd be very shocked to find out that F-14s didn't have gyros since they had some of the world's first microprocessors to calculate wingsweep, and there were jillions of other aircraft with gyros by that point. Every pilot should be able to do it with ease before recieving their instrument rating, it's the stuff that failed gyro or 'partial-panel' flying is made of. ...
Click to expand...

Well of course it has “gyros”. I'm talking about the air-to-air radar display, which presents data in an azimuth vs. range format, which requires the back seat guy to do the same sort of “compass arithmetic” that the OP of this thread is talking about, gyros or no gyros. In this case for calculating intercept courses, “collision bearings”, “stern conversions” and other air-to-air stuff.
 
PRB said:
Well of course it has “gyros”. I'm talking about the air-to-air radar display, which presents data in an azimuth vs. range format, which requires the back seat guy to do the same sort of “compass arithmetic” that the OP of this thread is talking about, gyros or no gyros. In this case for calculating intercept courses, “collision bearings”, “stern conversions” and other air-to-air stuff.
Click to expand...


My apologies! You said 'pilots' twice before you said aircrew members, so I figured that you were referring to F-14 pilots as only having a whiskey compass for navigation, not the RIO working his radar. I know nothing of radar built before the B-1 stuff. :icon_lol:
 
Lionheart said:
Hey all,

For you guys that know how to read a Whiskey Compass, what is your secret?

For years, since I was a kid, I have flown with family, become a FS FREAK, and have logged many hours with planes (in FS and some in real world) that have Whiskey Compasses, and still I cannot figure out how to calculate 90 degree turns, etc. My mind goes blank. Is there a secret that enables you to visualise the compass disc? Or do you at one point just 'click' with how to read it?



Bill
Click to expand...

Bill,

Here are the methods (and to confirm, this is only the magnetic compass and NOT the directional gyro stabilized compass):

1. NOSS = North Opposite, South Same. Meaning, when you heading northbound and you turn, the whiskey compass initially rotates opposite the direction of turn. When heading South, it actually rotates faster than the turn in the direction of the turn! What does this mean? Well, it means you do not reference the whiskey compass unless you are flying level and stable (not turning).

2. So, how do you use it to performs turns (especially when IMC) and your DG or HSI is broken? Here is how: You rely upon the mathematical fact that a standard coordinated turn takes precisely two minutes of time to complete 360 degrees of heading change. So, to turn 180 degrees, a standard coordinated turn takes one minute. To turn 90 degrees, it takes 30 seconds. To turn 45 degrees it takes 15 seconds. In other words, you turn at a rate of 3 degrees per second. So, to turn referencing the whiskey compass, you simply hack a clock and count the seconds once you are established in a standard rate turn using your turn/bank indicator. When the time you need expires, you roll out level and reference the whiskey compass to see how close you are.

Hope this helps!

Ken
 
tigisfat said:
My apologies! You said 'pilots' twice before you said aircrew members, so I figured that you were referring to F-14 pilots as only having a whiskey compass for navigation, not the RIO working his radar. I know nothing of radar built before the B-1 stuff. :icon_lol:
Click to expand...

Wrong again. Even the first F-14As of course had an RMI. (Just below the standby horizon).
 
The Old Whiskey Compass

When using a standard compass (gyro or glass) yu are in the center and point out so to head north you put N in front of you because you are positioned south of where you want to go. With a wet compass you ar outside of it and so have to fly (move around) it to find the heading your want. You are outside looking in to North so to turn to the east the compass will move right to left.

Learn to box a compass and you will never be confused - N, North by East, North North East, etc the numbers are just the decimal translation. Remember you and your aircraft are not the cernter of the world you are just flying in the world!

Hooligan 56 View attachment 9630
 
TeaSea said:
Lionheart....

Are you confused yet?

'cause we can keep going.....
Click to expand...

lol... Yep. I think Ive got it now. Thanks all for the input.

I was kind of hoping it would be some basic secret that enables all things to come together in the mind concerning looking at that dang thing and figuring what your next 90 heading would be, but nope.

My little 'home made' invention of sorts for calculating headings for 90 degree turns, is to use N, S, E, W as markers, and then measure the clicks or lines in to each side of the Direction marker letter. Thus if the runway heading is say 350, then its 1/8th inch or half a click to the 'left' of the main letter, then remember the main heading letter that orients with the runway. That way, I can just start making my turns, remembering 'half click to the left' , etc....

Its basic and helps me to 'see' the headings better without having to do math. I should be doing the math though so my mind will last longer.

:d
 
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