compass turns with high mounted compass (Cessna 152)

On Fri, 1 Apr 2005 02:33:35 -0800, "Ray" wrote:

I'm just starting out my instrument training in a Cessna 152 that has a
compass mounted at the top of the windshield. Here's a sample picture for
those who have never seen it, http://www.airliners.net/open.file/643201/M

Can anyone tell me if it's still possible to do compass turns under the hood
with this kind of setup? I've seen a lot of planes with high mounted
compasses, so I imagine this isn't a new question.


What is a compass turn?

I've done timed turns, (my instructors wouldn't even let me call it a
compass turn) but you can't do a turn while under the hood or in
actual while watching the compass. It'll even go the wrong way at
times and it'll change directions when you speed up or slow down when
on anything other than a north or south heading.

You look at the compass, figure how long to make a standard rate turn
(3 degrees per second), figure how many degrees to turn and then how
many seconds. Make the turn for how ever many seconds, roll out and
then check the compass to see how close you came to getting it right.

Short hand method... standard rate is 360 degrees in 2 minutes, 180
degrees in one minute, 90 degrees in 30 seconds, 45 degrees in 15
seconds and 10 degrees in roughly 3 seconds, or 30 degrees in 10
seconds. If you memorize these basic numbers you will be able to work
out any turn time in your head.

If you are referring to flying with a DE and will they let you use the
compass mounted way up there, the odds are no, but they will give you
the heading at the start and stop of the turn.

BTW, I find a vertical card compass "on the glare shield" to be great,
but the ones mounted at the top of the windshield to be a royal pain
when under the hood. They aren't quite so bad in actual, but I prefer
the compass closer to the rest of the instruments.

The new glass panels with all the flight instruments are great and
very easy to use although some pilots just can't seem to get used to
them. I find them to be natural. OTOH I don't think we'll see many
150s with glass panels soon :-)) They'd be worth more than the
airplane.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com
- Ray

On Fri, 1 Apr 2005 02:33:35 -0800, "Ray" wrote:

I'm just starting out my instrument training in a Cessna 152 that has a
compass mounted at the top of the windshield. Here's a sample picture for
those who have never seen it, http://www.airliners.net/open.file/643201/M

Can anyone tell me if it's still possible to do compass turns under the hood
with this kind of setup? I've seen a lot of planes with high mounted
compasses, so I imagine this isn't a new question.


What is a compass turn?

I've done timed turns, (my instructors wouldn't even let me call it a
compass turn) but you can't do a turn while under the hood or in
actual while watching the compass. It'll even go the wrong way at
times and it'll change directions when you speed up or slow down when
on anything other than a north or south heading.

You look at the compass, figure how long to make a standard rate turn
(3 degrees per second), figure how many degrees to turn and then how
many seconds. Make the turn for how ever many seconds, roll out and
then check the compass to see how close you came to getting it right.

Short hand method... standard rate is 360 degrees in 2 minutes, 180
degrees in one minute, 90 degrees in 30 seconds, 45 degrees in 15
seconds and 10 degrees in roughly 3 seconds, or 30 degrees in 10
seconds. If you memorize these basic numbers you will be able to work
out any turn time in your head.

If you are referring to flying with a DE and will they let you use the
compass mounted way up there, the odds are no, but they will give you
the heading at the start and stop of the turn.

BTW, I find a vertical card compass "on the glare shield" to be great,
but the ones mounted at the top of the windshield to be a royal pain
when under the hood. They aren't quite so bad in actual, but I prefer
the compass closer to the rest of the instruments.

The new glass panels with all the flight instruments are great and
very easy to use although some pilots just can't seem to get used to
them. I find them to be natural. OTOH I don't think we'll see many
150s with glass panels soon :-)) They'd be worth more than the
airplane.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com
- Ray

On 1 Apr 2005 06:26:48 -0800, "paul kgyy" wrote:

I think the problem is that, with a high-mounted compass, you are
looking out the window every time you look at the compass. I'm not
sure how examiners deal with this.

When I took the instrument flight test, I asked the DE about it. He
asked me if I could see out when doing that. I replied, "I wear
bifocals. If you mean can I see any thing the answer is no, but if
you mean can I see light and dark and I could probably figure out
where the horizon was if the conditions were just right. If they
weren't just right I would probably come up with a false horizon". He
said not to worry, he'd just give me readings when appropriate.

Whether he read the vertical card compass on the glare shield for me,
or I read it made no difference to me. Actually it was probably
easier as I didn't have to look up away from the panel. Compasses
that are not very close to your flight instruments are a royal pain in
the real world.

Whether they let you look at it, or not should make no difference to
you. You know how to make timed turns and they are *not* going to
have you make turns while watching the compass. I seriously doubt any
one in their right mind would even ask for it in VFR conditions. They
just want the student to be aware of the quirks of a magnetic compass.
I've never head of them expecting the student to make turns with one.
However if I had to use the compass I'd cheat by getting the heading,
then rolling into the turn and ignoring what the compass was doing.
Just remember that 2 minute standard rate turn, one minute for a 180,
half a minute for 90, 15 seconds for 45. you can interpolate for
anything in between.

Timed turns are not the same thing.

Even VFR you should be looking at the compass to get a heading, make
the turn for so many seconds, roll out and then check the compass
again. If you are VFR, who cares if you miss the heading, you make a
correction and check again.

I had an instructor cover up everything except the TC, air speed, and
altimeter to see how long I could fly a straight course. After five
minutes, he said, never mind...we were still on course. :-))

Now when he had me close my eyes and fly, I lasted about a minute and
a half before "we had to recover". (mainly due to the plane being
well trimmed and rigged and little to do with any skill of mine) He
said he saw very few students who managed more than 15 to 20 seconds.
I admitted I was letting the plane do most of the flying with me just
nudging the controls from time to time.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com