GFT Nav Test

[Steven JC]

Having completed my skills test (finally :D ) I am about to do my Nav test - this weekend, weather permitting.

I have a question for all those who have already done the Nav Test. When it came to your diversion, did you estimate your new heading and new ETA in your head (possibly based on the 3000ft winds at take off), or were you permitted to use your CPR-3 flight computer during the flight ? to calc/est them

I am slightly confused as my instructor said I could use the CPR-3 and then the following day told me he'd prefer it if I didn't ! :8


Anyone have any comments ?

[SteveR]

Cripes!!! I had enough problems trying to use that stupid thing on the ground, on the nice stable desk in the exam room - the thought of trying to use it in the air scares me witless.....

(Yes, estimate new heading and ETA - your examiner wants to see that you can get into the ballpark. A gert big wind arrow on the chart really helps).

Steve (who hasn't touched a whizz wheel since getting the licence to learn) R

[Steven JC]

I was hoping to draw on my wind vector whilst on the ground the all I would have to do is estimate an angle for the track to the diversion point - then spin the wheel to get my heading! !:E

Not to be however. I suppose it wouldn't be realistsic anyway since not many of us ever take them up in the air !

I had better start practicing my estimates ! :ouch:

[High Wing Drifter]

Leave the CRP wotsit whingy on the ground where it belongs!

Learn to do all the estimates in your head as you fly. It is impossible to imagine how you can fly safely twiddling away on a CRP at the same time!!!

Follow this advice from Aussie Andy. I did and it went like a dream (thanks Andy:)):

I was shown a really simple shortcut for readily working out drift and GS without the need for any mental gymnastics:. .. .In a corner of your PLOG, draw a small diagram consisting of the 4 lines that cross over each other - one vertical, one horizontal, and two diagonal - to represent the cardinal points of the compass, and the ones in between, ie. N, NE, E, SE, S, SW, W, NW. [Simpler than it sounds - I wish I could add a diagram here!]. .. .Now, before you depart, work out drift and GS on your whiz-wheel for each of these points, and write this near each of the points of the diagram as appropriate. E.g. you might write "+9deg / 85kts" above North, and South (might) be say "-8 deg / 105 kts", etc. This only takes about 2 minutes to do.. .. .Having done this, when you come to doing a diversion, you just need to work out the TRACK (pencil, eyeball whatever) in the usual way, then just look down to the PLOG to see that drift you need to add or subtract for the direction concerned, and the GS to use for your EET calculations.. .. .If this doesn't make sense, mayeb I can clarify by email with a diagram.. .. .I don't use this every time I fly - but it sure helped me get through the skills test diversion last year - it went really well!. .. .Hope this helps,. .. .Andy

In this thread:

http://www.pprune.org/forums/showthread.php?s=&threadid=42536&highlight=diversion+rose

[QNH 1013]

Well err yes, I did use my CRP1 to calculate the new heading for the diversion on my NFT, but I wouldn't dream of doing so now.
You have just been given one method of quickly getting the corrections for the new heading and there are plenty of other simple methods.
I had to do a diversion (re-route) to the Isle of Man on Saturday morning because I couldn't get over the Pennines in a PFA (VFR-only) aircraft, and I certainly didn't use a CRP1 or any other calculator.

[drauk]

Buy a WindProtractor from TransAir. It's a small circular plastic disc. You put one pencil dot on it before you take off to indicate the wind. Drop it on the diversion line on your map and read off the heading and the ETA. It is simple and will work without any ground preparation for once you've passed your test.

[Fly Stimulator]

Steven JC,

Further to Aussie Andy's suggestions quoted above, you might find the following little things I created useful.

This (http://www.theflyingschool.co.uk/windwheel.xls) is a spreadsheet which will do the actual calculations for you given the wind direction and strength, your airspeed and the magnetic variation. You could of course use your CRP-3 to do this bit, but do that on the ground first, not while you're flying. It's a bit hard to fly, use a whizz wheel and keep a lookout at the same time :eek:

Having worked that out, write the figures down as suggested by Andy on this (http://www.theflyingschool.co.uk/speed_and_distance_wind_wheel.pdf) and take it with you on your flight.

Good luck for your test!

[Steven JC]

Boy am I glad I asked this question. It seems that i might be able to pass after all. Thanks for your ideas. I really appreciate you taking the time out to help.

cheers


Steven

[hasell]

Hi,
Are you referring to the diversion part of the Nav for the GFT for a PPL? If so -please read on... if not ignore it.

I recall using the simple formula that

Max drift = 1/2 wind velocity.

So if the Wind was 12 Kts -drift would be 6 degrees.

ETA for arriving at a destination was calculated by:-

Time =2/3Dist + or - 10%.

Where the + or - refers to a headwind or tailwind.

So for example, you measured a diversion distance of approx 21 miles.
To get this distance you could have used a ruler or your thumb(=10 nm on 1:500,000 chart).

Time=2/3*21=14 mins.
Now suppose your flying into a headwind therefore add 1.4 mins.
So approx time= 14+1.4=16 mins. approx.
For tailwind -you need to subtract. So time to ETA would be approx 13 mins.

These worked for me during diversion practices for the GFT test and the test itself.

Best of Luck.

Has.

[Thirty06]

I bought a copy of 'Diversion planning' by Martyn Smith.

A pleasantly slim volume with some easy calculations and handy techniques.

I don't think it matters what you use to work out the corrections one you've sorted out the direction.

Basically:

On the ground draw a wind vector on the chart where you can see it.



Choose you diversion point.

Draw a line no matter how wobbly. From the point of diversion to the destination.

Guesstimate a halfway point.

Stick your pencil on the chart along the line.

Slide your pencil to the nearest VOR and read off the angle.
(Highlighter lines on the compass rose make this easier, using a VOR takes care of magnetic).

Do the drift calcualtion, refer to the DI to double check. (e.g course is 170, wind is 100, you'll need to steer into wind so the number will be smaller)


Divert over chosen point.
Write down the time.

Measure the wobbly line with a suitable object (ten mile thumb, pencil with lines on it or try to retrieve the plotter you've dropped on the floor)

Now calculate airspeed the journey time and hence the ETA.
(Again use DI for reference, is the wind against you or behind you ?)

Check course and speed at halfway point.

Achieve destination and pass nav test.

Don't hesitate to use whacking great line features that point directly towards your destination.

Since the DI only allows you to fly to within say 2.5 degrees there isn't a great call for ultra precise calcualtions.

Worked for me anyway.

30.06

[Steven JC]

Thanks again to all of you for help with this one. I had my test on Sunday and passed. I diverted to an airfield 22nm from my position and arrived almost dead on time (-10s). The chosen method was the cardinal points with drift and ground speed. It is straightforward enough to estimate a drift and g/s from these points and work out the ETA. The other methods sound useful also which means I can now try them without the pressure of an examiner !

Cheers guys

[Fly Stimulator]

:ok:

[Another St Ivian]

Just a quick tip regarding drawing lines from point to point on a chart. If the chart is small enough fold the chart through the two points, scribble your pen/chinograph along the fold and then open it out again. Admittedly the chart gets a little creased but as long as you folded it properly you have a dead straight line from point to point.

A.S.I

[High Wing Drifter]

Jolly good show!

:cool: