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VFR problems - compass reading, DHI drift, lost

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VFR problems - compass reading, DHI drift, lost

Old 20th Apr 2017, 19:04
  #1 (permalink)  
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Join Date: Apr 2017
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VFR problems - compass reading, DHI drift, lost

Hello everyone,

I just finished PPL and starting my time building. Even I passed PPL check ride but I'm not very confident with my navigation skills. I'll try to list all of my problems down here, asking if any of you have any idea of how to solve my troubles

1. DHI drift: I don't know if this is because of the bad instrument or not, but the DHI drifts a lot (after turning, during straight and level flight...). Of course I was trained to check it some 15mins (I did every 5mins) but the reliability of this thing keeps making me worry if it shows me the right heading or not.

2. Compass: This is the most confusing thing, it never stays still, it was jumping for like 30-40 deg. Every times I think my DHI drifted, I need a bunch of time to stare at it and leading me nowhere. I can't read it, and I cant determine if my DHI is right or wrong.

3. Estimating wind direction/speed using leg's time: Of course we all have METAR with us every flight, but the wind changed a bit and making our heading isn't correct any more. Normally I'll base on landmarks to navigate and find a new heading. But I heard someone tell me: "If you can estimate the wind direction by taking aware of the previous leg's time (it related to GS)". For this I don't really understand...

For my training, I understand that I have many methods to navigation in VFR flight: using time, using heading, using landmarks....etc. But because of the reliability of the equipment, right now I keep flying major on Landmarks, IF I lost my landmarks during flight, then that's it. I have nothing to recover.

Do you guys have any experiences for my problems? So many thanks.
Cestlavie077 is offline  
Old 21st Apr 2017, 00:47
  #2 (permalink)  
 
Join Date: Nov 2013
Location: Australia
Posts: 30
I'm sure most people have had similar problems.

1. Some of the planes I learnt in had very quick and large precession of the DG. Just get into the habit of checking it every <5 mins.

2. Can be tricky in bumpy conditions. But get straight and level and it should settle. Just be patient with it.

3. To work out the ground speed you're doing. Work out the time between your last fix and your current fix en route. Then Measure the distance on the WAC (VNC VTC etc) chart and used the wiz wheel to get ground speed. Be careful with the scales but any error should be obvious. Then you have an accurate ground speed.
As far as en route drift or wind. This is probably the wrong thing. But I would just give it 10 mins or so, then do a 1:60 to get the proper heading to the destination. I guess that's a bad shortcut on featureless terrain.

Edit: Dead reckoning feels unreliable at first. But you'll do some long sectors with good accuracy and your confidence in holding a disciplined heading and keeping track of time will grow.
Dawn Patrol is offline  
Old 21st Apr 2017, 02:06
  #3 (permalink)  
 
Join Date: Apr 2004
Location: Up The 116E, Stbd Turn at 32S...:-)
Age: 78
Posts: 2,735
It might be that you are 'chasing' your compass readings...perhaps....

You could try picking a point on the horizon to steer for, and then keep the nose of the aircraft pointing at that.

Provided you are in relatively calm air, this should be fairly 'easy'.

If you can trim the aeroplane so that it flies 'hands off' then that is good.

As the aircraft 'settles down' into a steady flight, pointing at your selected point on the horizon, you will find that the compass also 'settles down'.

Remember the compass is 'nippy on North / sluggish on South' and an acceleration on an easterly or westerly heading will show an 'apparent change' also.
Refer to your theory books for an explanation of these 'anomalies' to refresh your mind.

This may take care of your paras. 1 & 2.

The use of the '1 in 60' rule should assist you in calculating your drift, and accurate timekeeping between groundpoints will assist you in calculating your groundspeed.
This should help you with #3.

See how you go......and consult with your instructor.

Good Luck
Cheers,
Ex FSO GRIFFO is offline  
Old 21st Apr 2017, 02:12
  #4 (permalink)  
 
Join Date: Apr 2008
Location: Sydney
Age: 58
Posts: 375
Originally Posted by Cestlavie077 View Post
Hello everyone,

I just finished PPL and starting my time building. Even I passed PPL check ride but I'm not very confident with my navigation skills. I'll try to list all of my problems down here, asking if any of you have any idea of how to solve my troubles

1. DHI drift: I don't know if this is because of the bad instrument or not, but the DHI drifts a lot (after turning, during straight and level flight...). Of course I was trained to check it some 15mins (I did every 5mins) but the reliability of this thing keeps making me worry if it shows me the right heading or not.

2. Compass: This is the most confusing thing, it never stays still, it was jumping for like 30-40 deg. Every times I think my DHI drifted, I need a bunch of time to stare at it and leading me nowhere. I can't read it, and I cant determine if my DHI is right or wrong.

3. Estimating wind direction/speed using leg's time: Of course we all have METAR with us every flight, but the wind changed a bit and making our heading isn't correct any more. Normally I'll base on landmarks to navigate and find a new heading. But I heard someone tell me: "If you can estimate the wind direction by taking aware of the previous leg's time (it related to GS)". For this I don't really understand...

For my training, I understand that I have many methods to navigation in VFR flight: using time, using heading, using landmarks....etc. But because of the reliability of the equipment, right now I keep flying major on Landmarks, IF I lost my landmarks during flight, then that's it. I have nothing to recover.

Do you guys have any experiences for my problems? So many thanks.
Sounds like poor flight training. Your primary method of navigation (VFR or IFR) is based on DR (planned heading/time) which is supported by aids such as map reading, ground based navigation systems (NDB/VOR) and GPS. Don't develop a habit of flying from landmark to landmark - ie "map crawling". It's the fastest way to get lost.
You should find yourself a decent instructor (ex military flight instructors are excellent) to address your concerns.
roundsounds is offline  
Old 21st Apr 2017, 02:34
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Join Date: Feb 2017
Location: Sydney
Posts: 295
The gyro compass can drift more quickly if it is needing an overhaul or there are faults/wear etc. It shouldn't drift that much in 15 minutes and at all times should reflect smoothly any heading changes.

FWIW I have jotted down some suggestions if you want to get better at using the magnetic compass - use them if it helps, ignore them if not.

The magnetic compass can difficult to use if you aren't familiar with its foibles. If you develop an understanding of how it behaves and practice a bit you can become quite comfortable with it and that will give you confidence.

It is a fun exercise to get used to using the magnetic compass. Do it somewhere you are comfortable with the surroundings so you can find where you are (or grab an instructor). Then practice a series of turns onto headings using only the magnetic compass. Ignore the DI altogether for a while.

Firstly - it seems to turn the wrong way to most people. Try to think of the inside compass part (what turns - where the numbers are) as being fixed to the earth *not* the aircraft. When deciding if you need to turn left or right using the compass, think how you would turn the outside of the compass housing (the aircraft) around the inside markings to get the heading you want.

Secondly rather than rolling out on headings based on the compass reading, try and estimate where the roll out point will be before turning (ie pick a feature on the horizon), and roll out on that point and then correct once the compass stabilises.

So eg you are flying on a heading of 270 and decide to turn right to 020. First estimate where on the horizon that heading will be (ie 110 to the right - a bit over 90). Then turn onto that point. Once you have rolled out, check what the compass says once it is stable. Correct with gentle turns if necessary using the same technique.

Finally, did you learn the mnemonics for compass use in your training?

When getting a feel of the compass, when turning in the northern hemisphere++, use gentle bank angles and say "OSUN" (I need to Overshoot South and Undershoot North) when turning through northerly or southerly headings (ie the northerly heading readings take a while to appear on the compass so you should roll out before the compass says you have hit the right heading. After getting level it will catch up).

Similarly in the Northern hemisphere++ use "ANDS" for accelerating (eg when pitching down) and deaccelerating (eg pitching up), ie you will see the compass goes North when accelerating and South when deaccelerating - don't chase it, wait until you are not accelerating to get an accurate reading.

In turbulence the aircraft will be accelerating and deaccelerating all the time, and this will make compass use trickier - try and get an 'average' value rather of how it is moving.

Picking a reference point on the horizon first is a good technique even when relying on the DI for navigation and as a way to hold a heading without constantly staring at the instruments.

Like I said, just some suggestions, feel free to ignore.

++(In the southern hemisphere use ONUS and SAND)
jonkster is offline  
Old 21st Apr 2017, 03:27
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Join Date: Apr 2004
Location: Up The 116E, Stbd Turn at 32S...:-)
Age: 78
Posts: 2,735
Why thankyou mr 'RS'.....

The query was about attempting to read a compass due to
"it never stays still"......

To develop the habit of smooth flying is a looong waaay from navigating 'point to point' as you say......

And your 'ex military instructors'...????

No Thanks - I had my share of those when I was a 'sprog' learning....and then I really learned with a 'civvie' who really knew his stuff - and what is more important, he knew how to 'pass it on'......
Ex FSO GRIFFO is offline  
Old 21st Apr 2017, 04:01
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Join Date: Aug 2006
Location: Oz
Posts: 131
Time for a new instructor, Cestlavie077.

A good one will answer your questions and explain these basic principles until you are comfortable with them. Best done in an aircraft over a few short nav legs rather than reading on a forum.

DR and an accurate flight plan is all you need. The map is an added bonus. Make sure they are teaching you the 1/60 check.

Congrats on gaining the PPL. Your hour building will be much more enjoyable when you are confident and can enjoy the view, rather than stressing over your position.

Good luck
strim is offline  
Old 21st Apr 2017, 07:47
  #8 (permalink)  
 
Join Date: Dec 2001
Location: YMML
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Hate to tell you, Jonkster....you are backwards
OZBUSDRIVER is offline  
Old 21st Apr 2017, 08:23
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Join Date: Feb 2011
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I know you didn't come here for criticism, which I'm not indenting to do.

However, if you passed a PPL by map crawling and not DR 1/60 navigation, your ATO needs a swift kick up the butt.

You obviously don't have confidence in navigation still, so good on you for seeking out assistance.

As discussed, you need to really start researching 1/60 navigation and then practice those skills with someone who can guide you along.

Dead reckoning navigation is all about getting yourself off track, and being completely fine with that. If you were flying from A to C and the map shows your going directly over B, 9 times out of 10 you won't fly directly over B - and that's completely okay.
Slippery_Pete is offline  
Old 21st Apr 2017, 08:55
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Join Date: Apr 2005
Location: Melbourne
Posts: 2,371
As much as you're not "supposed" to rely on it, once you get an iPad and subscription to Ozrunways, you'll wonder why you ever bothered with a compass :-)
Squawk7700 is offline  
Old 21st Apr 2017, 10:17
  #11 (permalink)  
 
Join Date: Feb 2017
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Originally Posted by OZBUSDRIVER View Post
Hate to tell you, Jonkster....you are backwards
in Oz or Northern hemisphere? I took "Location: Lithuania" as fair dinkum, if actually Lithuania is in Oz, use reverse of what I said.
jonkster is offline  
Old 21st Apr 2017, 11:04
  #12 (permalink)  
 
Join Date: Sep 2002
Location: Great South East, tired and retired
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The wind is 100% efficient. if you have a 10 kt crosswind, and you hold a fixed heading for an hour, it will blow you 10nm in its direction. The most simple method is: hold a fixed heading, and every 30 mins or less get a fix. You will be half the wind speed off track, or if it is a headwind, you will be on track but half the windspeed short of where you should be. Make a sensible correction, and keep going. It is rare to go more than an hour in one direction anyway, especially in a helicopter or in the training environment.

If your map reading is so poor that you haven't had a fix in the last hour and found yourself less than 10nm off track, you shouldn't bother getting off the ground.
Ascend Charlie is offline  
Old 21st Apr 2017, 15:57
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Join Date: Oct 2005
Location: Australia
Posts: 795
Surely this is a wind up?
Clare Prop is offline  
Old 21st Apr 2017, 21:28
  #14 (permalink)  

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I think so Clare. The post appears to be from Lithuania but via a US server - a Proxy server? Been watching the thread for a response by the thread starter.

Cestlavie077 - or is that C'est la vie - I suggest you take up your problems with your Instructor in Lithuania.

Or where ever!
tail wheel is offline  

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