I’ve had two vertical card compasses and removed both of them due to ‘issues’ (which to be honest I’ve forgotten) The simple whisky compass type works OK for me, and was the theoretical primary navigation instrument on one of my planes. In reality the heading to hold in cruise is determined by making the plane move along the magenta line on the iPad Mini.
I have one of these in my Bonanza. I don’t use it much, mainly on the ground to verify that it is in agreement with the G500Txi. Mine has very good agreement. I don’t use a magnetic compass in turning flight anyway, primarily I make timed turns at standard rate and then cross check heading on the magnetic compass after it settles down. If I don’t see the desired heading, I correct with another timed turn.
I think these are 2 different things. As you get nearer to magnetic poles the needle dips downwards pointing towards the ground. Whereas in the other case when you accelerate the needle swings to the north and when you decelerate the needle swings to the south with it being the opposite in the southern hemisphere.
Does that apply to the floating sphere which seems to be the common SEP compass?
There should be bigger changes moving nearer the magnetic poles than crossing the equator, but staying between the tropics.
lionel wrote:
What you write makes sense, but my PPL courses did not teach me that the wet compass in the plane wouldn’t work well in the south hemisphere.
I don’t recall if it was in the PPL curriculum but the IR curriculum mentions the acceleration and turning errors that are caused by the asymmetric weight distribution of a wet compass.
Airborne_Again wrote:
Due to the inclination, you need to weigh it down on the “equator side”. If you didn’t, an ordinary wet compass would tilt so as to be unreadable at least in northern Europe.
Oh? What you write makes sense, but my PPL courses did not teach me that the wet compass in the plane wouldn’t work well in the south hemisphere. Indeed, wet compasses on aircraft spruce also have the two variants!
lionel wrote:
I realise these are sold in a “North Hemisphere” and a “South Hemisphere” version. It seems they are not usable in the “other” hemisphere. Most of us probably don’t fly across the equator that often, but worth knowing.
That’s more or less the case with all magnetic compasses, isn’t it? Due to the inclination, you need to weigh it down on the “equator side”. If you didn’t, an ordinary wet compass would tilt so as to be unreadable at least in northern Europe.
I realise these are sold in a “North Hemisphere” and a “South Hemisphere” version. It seems they are not usable in the “other” hemisphere. Most of us probably don’t fly across the equator that often, but worth knowing.
As I wrote on another thread I had to rely on the compass (in this case a horizontal fluid one) but both are useless during a turn, climbing or descending (not quite so bad) and acceleration and deceleration. @Peter is correct when using it partial panel you need to take 15% of your TAS to give you your rate 1 bank angle and then time of 3 degrees per second, levelling off once you have turned to the heading you want and then once straight and level cofirm the you are on that heading with the compass. In the IR theory exams we were always taught phrases like Never see North, Always see South to remind us that if turning North we should turn out of the turn before the heading comes up and if heading south we should turn out of the turn once you have passed the required heading on the compass rose.1
Another phrase was SAND(I think, its a long time since I learnt it) it refers to the way the compass needle will swing when accelerating or decelerating. It works the same on both horizontal and vertical compasses although it is more marked IMO on the vertical compass.
Of course this is all dependent on the hemisphere you are flying in.
But then no one uses the compass any more do they? Well not until it is the only instrument left to give you the heading you need.
Two identical threads merged.
I’ve had the standard vertical compass in the TB20 since 2002 – see post #1.
Would never go back to the previous (and basically unusable, unless you are a masochist) type.
There was that suspected issue, mentioned above, that it exhibits larger errors during turns, but I can’t substantiate that. I think any liquid compass is basically not intended to be useful except in straight and level flight, or very slow turns.
In instrument training, IME, you never look at the compass during turns when flying partial panel; you start with a straight and level heading and do a Rate 1 turn while counting off the seconds (3 deg/second) and if you do it anywhere near right, you roll out within a few degrees of the desired new heading. It works surprisingly well.
