PPL Diversions
 

Unplanned diversions
 

Locate "direct to" button on GPS, press, enter desired destination, follow lovely magenta line, disregard any other colour of line that magenta line may cross, do not look out of windows.:ok:

Sorry, I'm sure someone will be along soon with a sensible answer for you,

Find your current location on the map. Find your diversion on the map. Pinch both locations between thumb and index finger so a crease forms between those points. Run your fingers along the crease so it becomes sharper.

See if there's any airspace that you don't want to be in in the way. If so pick a waypoint that keeps you clear, make creases as required.

If there are line features that run in more or less the proper direction, find these line features and fly along them. Even if it makes the flight five minutes longer.

Look at the known wind. If wind from the left, steer left 5 degrees. If wind from the right, steer right 5 degrees. One thumb lenght, from the tip of your nail to the first knuckle, is 10 miles/five minutes. Add 5% if there's a headwind component, subtract 5% if there's a tailwind. Give ETA to instructor/examiner.

Look for waypoints along the way, increase or decrease your drift compensation as required. At each recognizable waypoint, measure the ETA again, give updates to instructor/examiner as required.

It may sound incredibly crude but it's good enough for PPL style flying.

Bonus points for informing ATC (actually a requirement if you're on a flight plan) and getting some sort of assistance, whether that's "flight following" or "basic service" or whatever. Frequency of your destination is on the map, so pre-select this in the COM box early, then locate the approach plates for your diversion and start planning the approach.

More bonus points for using radio nav. If the destination has an NDB or VOR it's virtually impossible (but not 100% impossible) to miss it. If it's got a DME (or TACAN) you'll know your groundspeed and ETE very accurately. GPS, as mentioned, is even easier. In addition to mrmums method, you can also go to the "nearest" page and select the destination from there.

I once witnessed a student do a practice diversion while I was observing from the back. It took him five minutes with the E6B, a ruler, a protractor and everything to plot his diversion. By which time the aircraft nearly entered a spiral dive twice, was of course 10 miles from the initial diversion point with the student hopelessly lost, and during which time zero lookout was kept. Boy, was I glad there was an instructor in the RHS who could fly the airplane in the meantime. The diversion calculation was eventually spot-on but we could've been killed a few times over in the meantime.

Construct a wind-star at the same time as writing up your PLOG.

Assuming you use the wind-down method, spin the computer round to the 8 compass points, and you can directly read off your groundspeed and drift angle.
Write them down somewhere on your kneeboard for reference.
(16 numbers sounds a lot, but it only takes 30 seconds to do this)

When you do the diversion, just look up the closest one to the direction you want to head in, and use that correction angle and groundpseed.
(Or you can estimate between the two nearest values for more accuracy)

I think you have to seperate the PPL flight test from real world flying. The most accurate way to locate yourself (the whole point of navigation !) is with a GPS. Frankly with the ready availabilty and very reasonable cost of modern aviation portable GPS I think anybody who does not avail themselves of this powerfull navigation tool is foolish. That doesn't mean you mindlessly follow the magenta line. Your Map should be out at all times with your thumb following along as well as a regular time/speed/distance/fuel remaining calculations. But why on earth would you not want real time position information ?

So with respect to the topic at hand if you need to divert first ask yourself what is the aim of the diversion. If it is to get to the nearest airport than the nearest function on the GPS is your first step. If it is to get around weather than the first question should be "do I really want to push on, or is it time to turn around/land". Assuming it is just an isolated area of bad weather than pick a nice obvious point to one side or the other, head for that and then when overhead turn back the same number of degrees and adjust track as required based on what you see ground to map and the GPS track guidance.
No GPS ? well then my advice is use the KISS principal. Is there a road/river/railroad going in your direction ? If Yes than follow it.

MrBrightside

I agree with BPF on diversion PPL vs real world.
If diverting per examiner, he wants to see some mental work in use.

Simple diversion is, when the examiner requests a diversion to X, draw a circle where you ARE and a circle where he said GO, DRAW a line between the two.
Look at the compass rose around a VOR etc and estimate the heading to your destination based on how the line you drew would overlay the compass rose.
eg. take a pencil and place along diversion line, hold pencil at same angle and move to nearest VOR and read heading.

Now use Lat/Lon lines 20-21 NM east/west, 30nm north/south on a VNC VFR 1:500000 to estimate distance. If 180kts GS, then 3miles/min.
Now the most important part...with a/c STABLE set HDI to agree with Mag compass, record time. Then start diversion. Tell examiner the ETA to first chk pt.

My instructor had a way which managed to get through to this particularly navigationally challenged pilot when I was a student - I'll give him a nudge to see if he'll either put it on here or send something by PM. :ok:

My instructor taught me a very simple "clock code" method for working out drift & GS on un/p diversions, i.e. :

Wind angle <15 deg off track, no drift & full wind speed effect on GS
Wind angle <30 deg off track, half max. drift & half wind speed
Wind angle <45 deg off track, 3/4 max. drift & 1/4 wind speed
Wind angle 60-90 deg off track, max. drift & no wind speed effect on G/S

Very generic and simple but works for me

Smithy

• Calc MD before departure and write it on the PLOG, together with Wind details.
• Decide where to divert from/to.
• Sketch and estimate track. Check for gotchas
• At start point turn on to TRACK and note time
• Use DI to assess proportion of max drift on that heading and adjust heading accordingly, add variation and write down resultant heading (so far no calcs)
• Find wind direction on outside of DI and project horizontally to estimate proportion of windspeed that as head/tail component, write down groundspeed (still no calcs)
• Mark the rack with 6 minute markers (1/10 of groundspeed) and estimate ETA.
• Now run normal nav process.

Simples! and no calculations whatsoever.

HFD

This sounds like a bit of a mish-mash of calculating the crosswind component (say, for an approach), which has turned into something which its not. For example, the "clock code" as you call it works like this (assume wind is 20kts)

wind @ 15 deg off track. Crosswind component = 1/4 of wind = 5kts
wind @ 30 deg off track. Crosswind component = 1/2 of wind = 10 kts
wind @ 45 deg off track. Crosswind component = 3/4 of wind = 15kts
wind @ 60 deg or more off track. Crosswind component = max wind = 20 kts

I use the above all the time for approaches but never tried it enroute so I can't say that it would work in the same ratios if you are travelling at say 150kts?

You're right, it is.

It's a very rough, balpark rule-of-thumb that as long as you've noted the max drift beforehand is useful.

Interesting to note the different methods people use! All handy to remember in case things go TU.

Smithy

1. Maintain VMC!
2. Choose somewhere visually significant from which to divert.
3. Fly to this ‘divert point’.
4. The back of the checklist (ours are laminated and have a blank back with a 50 mile half-mill scale on one edge!), a chinagraph and the CAA half-mill chart are the only planning tools needed:
5. Use the edge of the checklist as a ruler between divert point and diversion and draw the track line on the chart. Then lookout.
6. Measure the length of the line, write it on the checklist – then lookout again
7. Make sure the divert point is still in sight!
8. 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.
9. Read off the track angle – which, of course, is conveniently in degrees magnetic – write it on the checklist. Lookout again.
10. The 2 most important values, track and distance, are now known. Apply MDR to track (the pre-calculated max drift value is on the chart, of course!) and estimate the heading.
11. 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.
12. The hardest sum next! Time = Distance / Speed! Either mentally or on the back of the checklist. Write it down, then lookout.
13. Pre-HAAT check, overfly the divert point, post-HAAT check.
14. Fly heading and time diligently. Lookout and look down for visually significant points to confirm track maintenance.
15. At this point, I would certainly allow a student, who had demonstrated the ability to cope using 1-14 above, to use radio navigation or GPS to confirm his/her work.

I suggest you keep your head in the cockpit for the minimum amount of time you can. Keep looking out and going back to your calculations. Otherwise the aircraft will start flying itself for a short period!

Write down the max drift on your chart and use the clock code as already mentioned.

Alternatively, buy a copy of Diversion Planning by Martyn Smith for £8.50. It solved everything for me.

Groundspeed = Airspeed plus or minus Wind Component. If the Wind is behind you, or in front of you the Component equals the Wind Speed. Hopefully you drew this on your chart before you started
0-30 degrees use full WC
30-60 degrees use 2/3 WC
60-90 degrees use 1/3 WC

For simple distance/time measurement your thumb is 10nm from the end to the knuckle on a 1/500k chart:
Thats 6 minutes at 100kts
5 minutes at 120 Kts
7 minutes at 85kts

Here is an old post that may help

Gillespie
9th July 2006, 12:37
Leo45 is bang on. I use the exact same method, but to help you remember think of the clock face..

eg, if the wind is 30* off the nose, 30 minutes on the clock is half it's face therefore use half the max drift. 45* = 3/4 of the face so use 0.75ish..so on and so forth...

you can also use the clock face method to mentally calculate ground speed. For wind angles of 0-30* use all the wind, for 30 t0 45 use 3/4, for 45-60 use 1/2, for 60 to 70ish use 1/4 and for any angle beyond ignore it.

This is the method I was taught and find very useful. The wind-star should contain the drift for that particular heading along with the expected groundspeed.

1. When told to divert draw a line from your start point to the destination. Measure that distance with your ruler (I use a CPM 1 in flight).
2. Estimate the track to fly.
3. Adjust that track for the drift indicated on your wind-star to get your heading.
4. Consult the wind-star again for the groundspeed. With that in mind use a CPM 1 to find the time it will take to fly to the point of diversion - with that you can work out your eta.

Monitor your progress as usual and update ETA and headings if they appear to be different in reality.

Personally I really enjoy practising diversions, you have to be on your toes to stay ahead of the situation. If you are finding them hard then ask an instructor to go through them with you. Good luck.

Actually, instead of a wind star I simply keep my E6B, with the wind dot still plotted on it from creating the plog, in my (tri-fold) kneeboard. If a higher accuracy is required than simply using my thumb and max drift, I can operate the rotating and sliding bits with one hand, without even taking it off the kneeboard, and get a dead-accurate solution in about 10 seconds.

Rather than having to use any kind of CRP1/E6B/CPM1 in flight. I just made up a quick help sheet that I kept under the PLOG.
No calculations or fiddling necessary, just look up the values. :ok:

Here is the one I used for a C152.

Look at map, guess heading, sanity check by looking at ground features, correct as necessary as you go along. Need an ETA? My thumb is 6nm wide. Or tune in DME at destination and read the ETA from the screen. Guess a wind correction, if it's strong enough to worry about - for a PPL test, as opposed to a real life diversion, you'll have flown long enough before the diversion to have sussed out the wind (you've drawn the forecast wind arrow and written the speed on your map, haven't you).

Or you could use the GPS, if you've bothered to switch it on.

Faff around with CRP-1 and rulers and pens and arithmetic in the air? No ta, I'd rather do my spiral dive recoveries when I'm expecting them. Besides, there's too many gliders around to spend that much time not looking out the window.

Agreed, but why not use the KISS principle to start with, GPS or not? In my diversions it goes something like this: "Allo, la tour??? Give me a vector to the nearest runway/toilet/restaurant/clear bit of sky please". Only takes one button press :ok:

Backpacker - I like your post number 3 = helpful :)

BEagle: "12. The hardest sum next! Time = Distance / Speed! Either mentally or on the back of the checklist. Write it down, then lookout."

Avoid the random number generator known as "hard sums" by simply marking the track line at intervals of 1/10 of groundspeed (equivalent to 6 minutes) and adding-up the 6s (e.g. groundspeed 140 equates to 14 miles in 6 minutes).

HFD

Hugh, you're a genius. I honestly can't understand why I didn't think of that.

And your name is a belter :)

Couple of other useful tips regarding diversions: (1) Treat your current (known) position with (hopefully) a good landmmark as your 'local area' and don't set off from it until planned & ready. Once you set off, if it looks like you've made a gross error calculation then do a quick 180 and return to your known point to figure out your error.
Other tip (2) is to always note if you are north/south or east/west of good line features such as motorways/canals/railways etc. That way you will always know what 'grid sector' you are in.

it helped me on my ppl diversions very usefull devise
 

You can use any size intervals you want. Time between two intervals - let's say that took 3 minutes, there are 6 more - well that'll be 1.5 x 6 = 9 minutes. Job done.

You don't care about groundspeed in knots, you just need it in minutes per mark on the chart.

I learned to navigate flexwing microlights that way, and still use the system in an open cockpit.

G

At Sywell I was taught to use the knightson computer for diversions:
www.knightson.org.uk
Quite expensive for what it is :sad:, but very quick and efficient :ok:.

Tip: Put a bit of bluetack on the back so it can be stuck to the chart. That way if you have to look out of the window whilst using it you don't have to restart from scratch.:8

W

I go with the windstar method. Draw a cross somewhere on your map where you can see it easily (N,S,E,W) and then another for NE,NW,SE,SW.

You then work out the drift to apply using your CRP-1 calculator, as well as groundspeed, for each point. Write these figures against each of the points (eg. N -5/86). You can interpolate fairly accurately in the air for headings between the cardinal points.

I also had a small piece of paper with pre-defined GS and distances marked on it

e.g

Speed
5 10 15 20 25 30 (nM Distance)
80 <Fill in times prior to flight>
85
90

and fill in the times. You can then interpolate when you know the actual distance and groundspeed.

This worked for me during the PPL.

I don't like to take my eyes from outside the window if diverting due to weather - at least not until I'm well clear of the weather. Too much risk of entering cloud. But I suppose things will be different if you're trying to pass an examination.

Pathetic; the examiner expects you to plan a diversion with head down, doing the maths etc etc. In the real world, tell him, (or her) that would NOT be your plan. Radio OK? Ask for a vector! Say Student pilot, uncertain of position! I had to do that to find my way back to Booker from Blackbush when it all got a bit fuggy......and was located just about directly overhead RAF Benson, who were actually the kind folks advising me! Cloud base getting so low I had to creep up the motorway to clear the Chiltern ridge.

Never never hesitate to ask for help.

But you won't need help if you follow motorways or coastlines. Or use your GPS. Or get your instrument rating and the enroute controller will TELL you where to go!

All the other advice given in this thread is why glider pilots don't trust power pilots to be keeping a decent lookout. The emphasis is on the gadgets rather than the mark one eyeball.

Not quite all, I did say:

Quite right, Gertrude. There's a glider pilot in Coroner's court in Oxford this week giving evidence; he was able to parachute to safety when hit from behind.....the occupants of the power plane not so fortunate.

A unique case, but then every case is. Please maintain a good lookout, as Gertrude sensibly recommended..

Irrespective of the gliders, I go flying because the view is good. Why should I want to spend any more time looking inside the cockpit than absolutely essential to safety?

G

Because that's where all the blinking lights and colorful displays are?:E

(Hat, coat, and I'll have another glass of wine...:))

I'm not surprised glider pilots don't trust power pilots when you see the number of threads asking about GPS, IPADS, Mobile fone apps etc. When does flying the bloody aircraft fit in??

Well quite, you can play computer games rather more cheaply on the ground.

Though I have to say that flying a GPS approach on a G1000 is a good computer game to play in the air :)

(Mind you, I feel the same way about aerobatics - you can buy sick-making G forces far cheaper at a fairground - and I'm sure there are those here who would disagree with me on that one.)

Helicopter PPLs seem to manage diversions OK without writing or marking anything at all on the chart while flying. A bent thumb is a convenient ruler.

Pre-flight planning also helps...



PS hugh flung-dung you have a PM from a while back.

Silvaire's comment seems quite sensible. Except that when I did my PPL last March the documentation stated that I mustn't feature crawl, and had to work out a course to fly. And specify an arrival time +/- a couple of minutes.

Most things covered already, personally I use clock method applied to max drift for heading and thumb for distance/time. Agree that there are some that have you with head down too much, and for those with GPS - not all of us have one and, IMHO, even if you use one you should still know the basic techniques.

A couple of other tips :-

if you are diverting for weather you might want to do a 180 - to do this just look at the bottom of the DI - that is your reciprocal heading, turn onto this then adjust by DOUBLE the drift you had on the original heading - look at the wind arrow you have drawn on the chart to confirm which direction to apply it, you already have waypoints you have seen and head/tailwind will be the same as outbound but in the reverse sense.

To draw a line on the chart, put your pencil at one end of the line, lookout, look back in at the point you want to draw to and looking at that point draw your line - might not be perfect, but close enough and takes no time at all.