Nav diversions

[white light]

Following on from the thread on nav, what are your favourite NON GPS, diversion techniques. I don’t use the one in 60, as I find it too complicated in the air. (Unless someone can simplify it).
I just go with drawing the line, turn to the track& using my thumb to measure. (Mine is 10nm)
anybody do anything differently?

[Flyingmac]

I ask ATC for vectors.

[Hot 'n' High]

An earlier related post worth looking at is here. I have no vested financial interest but knew they guy who developed it - a good bloke. We certainly used it when teaching students diversions at the Clubs where I was an Instructor.

[white light]

Thanks to those who answered.

I did a search, (which I probably should have done first, sorry) & found some useful old threads

[BEagle]

Here's what I wrote nearly 20 years ago:

Unplanned diversions are introduced in the latter stages of navigation training. By then you should have been introduced to MDR (Mental Dead Reckoning), including the calculation and application of Max Drift. I advocate:

Maintain VMC!

Know who to call for assistance if you doubt your ability to cope.

Choose somewhere visually significant to divert from as well as a suitable diversion.

Fly to the ‘divert point’.

The back of the checklist (ours are laminated and have a blank back with a 50 mile ½ mill scale on one edge!), a chinagraph and the CAA 1:500 000 chart are the only planning tools needed:

• Use the edge of the checklist as a ruler between divert point and diversion and draw the track line on the chart. Then lookout.
• Measure the length of the line, write it on the checklist – then lookout again
• Make sure the divert point is still in sight!
• Find a suitable VOR rose on the chart, use the checklist edge as a parallel rule and draw a line through the VOR rose parallel to the diversion track. Then lookout.
• Read off the track angle – which, of course, is conveniently in degrees magnetic – write it on the checklist. Lookout again.

The 2 most important values, track and distance, are now known. Apply MDR to track (you should have written down the pre-calculated max drift value on the chart, of course!) and estimate the heading.

Note the head or tailwind component and work out groundspeed to the nearest ¼ mile per minute. Then use it as a fraction (e.g. 5/4 miles per min rather than 75 knots) – the error over the short distance involved is unlikely to be significant.

The hardest sum next! Time = Distance / Speed! Either mentally or on the back of the checklist. Write it down, then lookout.

Pre-HAAT check, overfly the divert point, post-HAAT check.

Fly heading and time diligently. Lookout and look down for visually significant points to confirm track maintenance.

[white light]

Beagle
yes, I saw that. Wow! nearly 20 years ago!
(I didn’t look that closely at the date)

[Big Pistons Forever]

Beagles advice is a great way to pass the flight test. But for the the only for real divert I have ever done I went straight to the GPS, selected nearest airport then direct to. Wildrose Wisconsin turned out to be about 8 miles away and we were on the ground 3 minutes later just before the weather went completely to shyte. When the chips are down you want to use the best aids you have.

[Beaker_]

Here's how I'd do it personally:

• Pick your starting point and diversion point. Draw a line on your map, marking the half way point.
• Make a best guess for a wind-corrected heading and note the time.
• Use the DP-1 plotter to calculate the distance and refine the wind-corrected heading. You can also use this to estimate the arrival time.
• Refine your heading/ETA at the half way point as per usual.

Nice and simple

[Genghis the Engineer]

If I'm diverting, VFR, without use of GPS, I'll generally be looking for the best possible ground features and how I can use them.

If there's a large easily visible town with a railway running to the airfield I want to get to or a motorway in the vicinity, I'll be using those, not mucking about drawing lines on maps.

G

[Maoraigh1]

If not on a test, with an examiner to keep a lookout, how much time are you head down doing those calculations and risking an airprox in busy airspace?

[BEagle]

If not on a test, with an examiner to keep a lookout, how much time are you head down doing those calculations and risking an airprox in busy airspace?

If you read my post, you'll note that frequent l00kout was always required between elements of diversion planning!

[EXDAC]

I usually have 2 or 3 sets of current charts in my airplane and none is paper. Drawing lines on charts is anachronistic. Touch the destination and execute DIR To. Far less head down time and no mental arithmetic.

Yes, I used to navigate with map/chart and compass and flew thousands of miles that way in gliders before GPS was available and allowed in contests.

[Fred.Kite]

Here are the details of a pilots last flight who didnt like mucking about drawing lines on charts either. He won’t make that mistake again though!

https://assets.publishing.service.go...BXRG_10-12.pdf

[Fred.Kite]

Originally Posted by Maoraigh1

If not on a test, with an examiner to keep a lookout, how much time are you head down doing those calculations and risking an airprox in busy airspace?

With a good understanding of TEM and Resource Management you will be able to answer that question yourself. If the greatest threat is traffic, you concentrate on that threat more than navigation. Your greatest resource is the aircraft radio or GPS or VOR, if you have it, with a diversion. So shout out, ask for help and get a traffic service if possible. Mitigating the threat of controlled and regulated airspace can also be a major consideration with a change in plan. With any threat, which a change of plan requiring a diversion is, prioritise the threats, consider the mitigations and use every resource you can. This is aircraft management and it’s a skill sadly lacking, mainly because it’s not considered and not taught very well in the UK.

Single pilot flying is hard work when plans change. Practice is needed but attempting to think about possible diversions at the planning stage helps and improves SA. On our 10/15 minute en route checks we consider a suitable diversion each time the check is done. Surprises in flying are always better at the briefing stage!

[Pilot DAR]

So shout out, ask for help and get a traffic service if possible.

Yes!

I admit it, a few times I have decided that it would be better to tell ATC before I make a total fool of myself, and become a danger to others by being lost. Every time, ATC has been calm and gracious, and given 100% useful help, with zero backlash. That, to me is one of the very, very few times, where "communicate" should precede "navigate"! if you're lost, let the people around you know, we will look after each other! I have also been the pilot looking (with ATC radar help) for the lost plane to lead him home.

Your greatest resource is the aircraft radio or GPS or VOR, if you have it, with a diversion

With caution, and you still thinking for yourself - yes. That is to execute an unplanned diversion, in harmony with ATC and any traffic or airspace considerations. But, reverting to GPS to "get you out of trouble" does not relieve you of still being on guard. I had a very memorable bad experience while special VFR, in controlled airspace over the Baltic Sea. ATC was being very helpful, and the GPS gave me a magenta line to the diversion airport. 'Should be good, but was bad. Long story short, with a valid obstacle database, the screed decluttered itself with out any annuciation it had done that (an intended function, but very poorly thoughtout by the GPS manufacturer) As I was at 700 feet over the water in skuzz VMC, I could see the windmills on the shore, and I was not going to accept the GPS' offering of a magenta line across them at 700 feet! Maybe I'd clear, but I was in no mood to experiment with that. My spidey senses told me to intercept the localizer (way off the magenta line route), and follow that in - windmills are not on localizer approach paths. It worked, and I'm here to tell the tale.

A diversion suggests things are going wrong. Understand that's happening to you then, tell someone, ask for assistance, and still keep your head about you - be no more relaxed than normal!

[Fred.Kite]

All resources come with caveats and an understanding that error can never be totally eliminated.