Navigational Question

[gertcoetzee]

Have a look at this picture - I have transposed the magnetic rose on my track flown yesterday, giving the magnetic bearing for the different legs. Will the compass bearing read the same?

What if I am flying in a strong crosswind, and am crabbing. Since I have no rudder the trike is at an angle to the course and the compass still remains fixed to true magnetic north. Will the compass bearing and my track be same? Ie in the first section I am flying at a 60 degrees magnetic bearing. In 0 wind my compass reads 60, will it read the same at a stronf crosswind?

Put it another way - on the runway, standing still, my compass reads 02 for the runway. Now I am flying over the runway, with a strong wind at right angles, crabbing - what will the compass read?

[John Young]

Since I have no rudder the trike is at an angle to the course and the compass still remains fixed to true magnetic north.

This is the answer to your own question. The compass doesn’t move. It’s one of the hardest things to teach an apprentice on the helm of a sailing vessel [especially at night !!].

Will the compass bearing and my track be same?

No - If "bearing" means the direction you are pointing / facing, then magnetic heading and course made good [track] can be very different.

In the first section I am flying at a 60 degrees magnetic bearing. In 0 wind my compass reads 60, will it read the same at a strong crosswind?

A compass always reads the same [fluctuations in deviation and variation excluded].

Put it another way - on the runway, standing still, my compass reads 02 for the runway. Now I am flying over the runway, with a strong wind at right angles, crabbing - what will the compass read?

As per your example, if you “drew” an imaginary line through your compass parallel to the runway, this line would read 02. If you took a magnetic heading in terms of where you are pointing, this reading may be 04.

I sure hope that I understood your questions properly.

Kind regards - John ZS-CIB

[gertcoetzee]

Thanks, yes it explains what I thought. Which makes navigating in a trike over unknown territory difficult with unknown windspeed, and on top of that a compass which, especially if it is bumpy, seems to resemble a roulette wheel.

[John Young]

My pleasure. Gert – add poor visibility [no distant horizon] to your post and you have all the ingredients for a pilot to get very lost and confused.

I see that I signed off as John ZS-CIB

Regards John ZU-CIB

[kb]

One of thie things I learnt on Nav, is when you are airborne, try and set up the plane on the correct "heading" (the nose of the a/c) then, fix a point on the horizon, and fly to that. It may mean that you have to turn onto the downwind side of your track to get it lined up, but then, regardless of the wind, you fly to that point on the horizon.

regards

[IFLYHI]

Somebody training hard for an upcoming championship
Gert your dedication to our sport leaves me in awe :D

[Biggles]

Gert, for navigating in cross winds, I get the nose pointing in the right direction spot the piont on the horizon and then draw a line back along the ground (noting features along the track), then adjust your heading for the wind so that you are tracking this line, its is quite easy if you sight on the tip of your boot and the ground and see if your track is lined up with the piont on the horizon. spot visual references that you should be over-head if you are tracking correctly.

Good luck with the comp:) will try and make a turn!!!

[Morph]

Good luck with the comp:) will try and make a turn!!!

Grab your instructor and come and join in

[John Young]

Gert, for navigating in cross winds,

Hi Biggles,

Yes – everybody and hopefully every student knows this.

But as stated in the thread, put a combination of factors together such as;

• Severe turbulence [pre-frontal conditions for example]
• Cross wind ["white horses" on the water of the dams]
• Unfamiliar terrain
• Poor visibility with no horizon
• Compass rotating like a gyroscope
• Ceiling descending [forcing a lower AGL – 600’ foot above monster mountains]
• Drizzle
• So cold [pilot’s torso shaking uncontrollably inside thermal flight suit], hands dead - “moving bar with elbows”, plus right thumb now unable to reach and press the PTT and respond to a direct call.
• And – all this found during a great weather forecast and the best of planning.

Ja Boet – ask me [except for the compass – I don’t have one]!!

Regards - John ZU-CIB

[Biggles]

Ja, I suppose... keeping a track and being hurled all over the sky is difficult, ...

Morph... Eish, you should have seen my last dead stick spot landing I had a nice view of the spot from about 50ft up!! Need much more practise and by the way the wind is howling I am not getting it this week P.S. Finished all my solo hours, just a dual and solo cross-country left :D

[Tower]

Hi Guys,

I had a simmilar experience with GPS on Tuesday, Flew from Microland to Bronkies dam, had quite a wind coming from the north, my track being almost due east, fortunately I knew the route well and had a visual on my destination. My Gps was pointing almost 70 degress off track, then i realised, just because my nose is pointing north, my track could well be easterly, so I kept on flying, making sure the GPS arrow points "up" and it worked. I was lucky because I had visual, but a good training lesson for in case one day I dont have visual!

A bit of instrument flying in a trike!

[Oddball]

As far as I can see, trying to use a compass on a trike is almost impossible. On bigger aircraft the problem is the same- one of the issues is that when you climb or descend, or accelarate and decelarate, the compass will swing and provide you with an incorrect reading; same thing when you turn. Thus you can only rely on the compass when you are straight and level.

In these bigger aircraft the problem is solved by employing a DI (Direction Indicator) which is a gyroscopic instrument that stays very steady and reads accurately through most manoeuvers (gentle ones that is).

Aside from the GPS map reading seems to be the best method of navigation, especially in competitions (where a GPS is not allowed in any case). Correctly interpereting a map works very well, particularly because we fly slowly and you have time to match things on the map to features on the ground.

[John Young]

I was lucky because I had visual, but a good training lesson for in case one day I dont have visual!

Hello Tower,

May I suggest that it was an even “better lesson” for the day that you don’t have your GPS.

In my scenario, I was forced to go to IFR rules . Could see “squat” – followed the N3 past Nottingham Road, flew across Midmar Dam and bailed at Howick where luckily we could organise a hanger.

At some stages, will full power [582], bar slightly forward, good airspeed [52-55 mph although my ASI was fluctuating wildly in the turbulence], I was still being “rotored down” at >500 fpm while flying low level [<600’ AGL] due to the reducing ceiling over huge mountains.

Nah, I was not scared – I was just "effing" PETRIFIED

Regards
John ZU-CIB

[Morph]

John,

I hear you. One thing I have noticed with pilots going from good to bad conditions is they will try to push through it to find a safe landing spot, progressively getting deeper and deepr into the dwang where perhaps the better decision could sometimes be to turn back, to the better conditions, find a landing spot and then work out next what to do.

The most important is to first get safely on the ground.

This happened to Gr8-dad and myself, where we picked up a headwind so strong that my calculations told me we wouldn't even make halfway, which had a landing spot, but this was still very marginal. Potentially making a landing spot 1h30 away or definately making the airfield behind us 30 minutes away. A no brainer.

[John Young]

A no brainer.

Howdy Sir Morph Da Boss,

I was not lucky enough to have a “no brainer”.

Route was Dundee via Estcourt to Cato Ridge. By the time I was in deep K@K passing Nottingham Road, neither Estcourt nor Cato Ridge were possible. To have turned NE from my position would have put me in “ungaass land”.

In short, I found myself in a very undesirable position.

Regards – see you guys soon.
John ZU-CIB