RAF Navigation "Training"??

[homeguard]

Sea no Land.

The use of Radio Aids are an addition to basic Nav. The basics of navigation to PPL standard assumes that the aircraft is not fitted with such aids as VOR, DME, ADF or the likes of GPS or that the transmitters are not available. Such well developed root of the art techniques correctly applied work well. The techniques apply whether over the sea, desert or the satilite towns of the home counties and they do not need batteries or generators to function.

That is not to say MDR is wrong. The navigation section of the CPL Skill Test is a section that has the greatest rate of failure. Why - the mistakes are usually silly - well the pilot is under stress. Simple mental arithematic becomes a burden and the visual clues, like a mirage, become what the individual wants them to be, mistakes are made.

It is a fact that there is not a single unpredictable factor that will raise it's head on a flight and it is therefore within the pilot potential to pre-plan for them. Using Forcasts winds and calculation of headings prior to flight using the slide rule and common sense mental arithmetic is part of that philosophy.

Whether or not you are a supporter of MDR, don't thow out the baby with the bathwater! Supported with the basic skills of navigation MDR has a place. Indeed it is currently taught under the heading 'Unplanned Diversion'. Always has been.

[Blogg's Pal]

UAS flying training is aimed at producing potential fast-jet pilots. At 420 kts (7 nm/min) the effect of drift is very small. You need 70 kts of wind to get 10 degrees of drift! If you think I'm going to get a DC out at 250 ft at that sort of speed you must be mad.

Military navigation is based on the premis of maintaining track and regaining track asap, which is usually your only tactical option. MDR works very well for this. PPL level navigation seems to be based on blindly following a plan adjusted for imprecise winds until you find you are miles off track and then making a correction to achieve your planned turning point. What is the point of planning a route to carefully avoid problems like controlled airspace, resticted areas etc and allowing yourself to wander off track. Any wonder we see so many reports of PPL traffic infringing.

MDR is great for maintaining track. I would rather be on track than blunder into a restricted/danger area. It relies on a basic understanding of the triangle of velocities and provides a quick, simple and acurate (as acurate as the met man's wind forecast) means of getting from A to B. It'll do for me.

[BEagle]

No-one is suggesting that you should use a whizz-wheel for in-flight corrections when using pilot navigation.

The effect of drift is far greater at 'PPL' speeds; an accurate pre-flight plan with time at waypoints (exactly as used to be taught at UASs) is flown; corrections are made using, in the main, SCA and proportional timing. MDR is taught for unplanned diversions using clock-face and max drift.

I certainly agree that regaining track by the quickest rigorous means is preferable to flying direct to the turning point from a position miles off-track and blundering into restricted or controlled airspace as a result. Hence we haven't taught the ancient 'track error plus closing angle' based on the 1:60 for years - or the New Track Reference method either, for that matter.

KISS - Plan accurately, fly accurately and think ahead.

[blagger]

I have been taught to navigate both in the EFT system and the PPL way, and one observation I would add is that many civvy flyers plan and fly very long legs. I have always tried to keep the legs somewhat shorter and use good positive fixes - even if it means going out of the way a bit. I know some people will raise the issue of 'feature crawling' with this method, but I do believe that if you have a shortish leg with a decent half-way (or 1/3 and 2/3) position/time fix without long amounts of time in between them, it gives you the confidence and ability to dump the map in between fixes, fly and look out. Your route shouldn't take you that close to restricted areas etc.. that it means you are paranoid about staying exactly on track at the expense of lookout and sortie management.

Blagger

[hugh flung_dung]

Forgive my ignorance on two counts (at least ) but:
- Correctly applied, the Max Drift techniques are as nearly as accurate as the wizz wheel, what's the problem with using them for pre-flight planning as well as in flight?
- What's the "New Track Reference" method?

HFD

[The Trolls' Troll]

Thanking you Hugh Flung Dung for echoing my sentiments with respect to using MDR for pre-flight planning.
What difference does it make if the pre-flight is done by the brain or computer, mechanical or electronic?
As to the "new kit" I referred to in my earlier postings, may I suggest a click on the WWW opposite my name, to get a better idea of where I'm coming from.
All comments adverse or otherwise gratefully received.
System designed by a Scotsman, made by an Englishman and looking for (probably) a Welshman who can talk the knickers off a nun to market it.

[hugh flung_dung]

AWL: good luck with marketing it - it's a nice idea but I have a personal hate of gadgets. The MDR calcs can be done visually on the face of the DI to any accuracy that you care to use so I don't believe another gadget is necessary.

HFD

[BEagle]

A question for you MDR pre-flight planners. Having noted the proportion of max drift to apply for heading correction, do you also apply the head/tailwind component to your planned TAS to obtain a GS? If you do, and the result is something like 103 kts, how do you then calculate the time at a visual fix 17 miles along track? In your head, on your fingers - or with a calculator?

Or do you say "Well, 103 is nearly 105 which is 7/4 miles per minute. 4/7 of 17 is err, umm, seven fours are 28, four tens are 40, so that's 68/7 which is err, a bit under 10 minutes."

Which is a bit gash if you then try to estimate your revised ETA when you are early/late at the 17 mile fix 1/3 of the way along the leg!

[The Trolls' Troll]

Hello Beagle,
In the head. Something like this.
103kts, somewhere between 100kts and 110kts. 100kts factor 0.6. 110kts factor 0.55(the factor is the no. of nmls covered in 1 min.)
17mls,@100kts, time taken =8.5+1.7(0.1 is a 1/10 of 17) = 10.2mins.
17mls@ 110kts then 8.5+ 0.85 (0.05 is 1/10 of 0.5 which is ½ of 17 which is 8.5) = 9.3 mins.
If it takes 10 mins exactly Gspd will be 102kts.
(17 times 60/10 ie times 6=60+42=102). Use this as the base.
In the air. 10 mins=102kts. Shade over 11mins 90kts. 8.5 mins 120kts. Split the difference if accuracy is requd. Ie 10.5mins use 95kts. 9.5mins use 110kts.
Whatever the time taken, double it and add to the real time to get best ETA. if 17mls is 1/3 of the route which continues in a straight line.
Quite a good example, that shows the benefit of doing the MDR for pre-flight planning on the ground. You get an idea of the type of calculations and the sort of figures you’re using in advance, so when you come to do them in the air, you remember and recognise them. The 90kts to 120kts is a tricky area. 90kts is 2/3 or 0.66 and 120kts is 0.5 or ½ and 100kts is 0.6. In the example you gave, you used fractions. Sometimes decimals are easier, sometimes fractions are easier. Use whatever is easiest as accuracy is not paramount. Both can be used. What is required is a facility to switch between fractions and decimals and rounding up and down, something that has been lost in the calculator age.
In navigation, 60 is everywhere. Take 17 mls in 13 mins. If 17mls in 12 mins,17 times 5. If in 15 mins 17 times 4, then split the difference. But that involves three “reckonings.” For me that’s too many.
Using my method, I know that 60/13 =4.6(approx), so 17 times 4.6 = 40+28+9or 10 =78kts. Only one “reckoning”.
Although lots of nos divide into 60, the problems come from the ones that don’t. I’m not usually going to be flying a leg longer than 20mins without a pinpoint. So I’m only interested in the nos that don’t divide into 60 between 1 and 20. These are 7 8 9 11 13 14 16 17 18 19( so near to 20 it can be chucked out
Strangely the nos make an easily remembered sequence.
60/7=8.6
60/8=7.5
60/9=6.6
60/11=5.5
60/13=4.6
60/17 =3.5
As for 14,16 and 18 into 60, they are ½ that of 7,8,9, so 4.3, 3.75 and 3.3 respectively.
The benefit of committing this little table to memory is that you only have to do one multiplication in the air. It’s not super- accurate. There has been fairly liberal rounding up and down, but it meets the requirements for easier DR in the air. For any application there is always a balance between accuracy and speed. In the DR situation speed and facility get priority over accuracy, within limits.
Getting the wind vector can be done mentally but involves about 3 calculations using the 1in 60 rule and
gives the wind angle to the plane. Too much. The plastic gadgets win out on this one. Gspd +WCA, simple up down movement of protractor on Gspd scale and read-off. Simple Triangle of Velocities and very accurate. MDR thereafter, comparing what you thought you would get with what is actually happening.
I’m off to check the GPS still works and give it a chance to up-date the almanack and ephemeris. Great little things. Gives the passengers something to play with, keeps them strangely reassured as to where they are, where they’re going, and most important of all, answers the question( but only based on the current GSpd) “When are we going to get there?" Probably the mindset is "If it's on TV or something that looks like a TV it must be OK." Just a passing thought but may be not a few pilots have the same mindset.

[Tinstaafl]

Easiest & quickest method I know:


103 ......... 17 <---- outer scale on a whiz wheel
______________ <---- divisor on a whiz wheel
. / \
/60\ ..........10|| <---inner scale on a whiz wheel


Answer = 10 min

[BEagle]

9:54 to be precise. Which is why, as you so ably demonstrated, the whizz-wheel with its analogue scales is so useful and simple for pre-flight planning!

Using MDR, all those 'factors' and inverse 60 times table seems much, much more difficult, error prone and of somewhat nugatory efort. Moreover, errors introduced by MDR pre-flight planning for ETAs mean that it may well be not just the wind which may have caused a time error at the 1/3 leg point, so proportional timing correctio is not valid.

But MDR is fine, absolutely fine, for unplanned diversion work.

[The Trolls' Troll]

9:54 at 103kts compared to 10.00 at 102kts. 6secs and 1kt.
On the day in the air you wouldn't notice the difference.
Unnecessary accuracy for an environment in which too many factors are not able to be measured with great precision.
Going for such accuracy using precision instruments in the pre-flight plan is wasted effort because you are guessing the wind vector. A 5kt, 10 deg error in the wind vector will knock all that accuracy for six, especially at the six second level.
Once I've got the wind vector, that's when I start sharpening on my eta's.
MDR is fine for unplanned diversions. So presumably it won't hurt to use it for planned diversions. That's the way I see it, the whole route becomes a series of planned diversions.
As to the nugatory effort involved with the factors and the mental arithmetic of 60, there is little to learn, and you only have to learn the ones that cover the speeds within 35kts+ and 35kts- of the cruise speed of your aircraft. The factors make the mental arithmetic easier. That's what they're there for. True, they are less accurate than the whizz-wheel but the differences in practice are barely discernible.
On my last navex to the the West of Scotland and the Inner Hebrides, the rate of change in weather meant, that to stay VFR and avoid high ground, going anywhere was a series of diversions. If the MDR is good enough for 1 unplanned diversion then why isn't it good enough for 4 or five planned diversions in series?

[BEagle]

I too have a dislike of airborne gadgets, many of which slither about on the CAA's laminated chart and end up on the floor..... But pre-flight planning using the simple old Dalton is a different matter. It takes no more than a minute or so for a triangular route and the forecast wind is normally of sufficient accuracy for a typical 50 mile leg. Then it's 'Heading and time' between pre-planned fixes, correcting heading and ETA estimates by in-flight observation, not re-planning the whole leg after wind-finding which I find something of an over-complication for PPL level navigation. The difference with 'unplanned' diversion flying is that map reading is required to back up in-flight estimates to a somewhat greater extent than on planned legs.

Arrive at the 1/4 way fix with an error of 20 seconds between planned and achieved time would normally require a turning point ETA correction of 80 seconds by conventional proportional timing correction. But if 10 of those seconds were due to 'near enough' MDR planning and 10 were down to the wind, an 80 sec correction would clearly be incorrect. And it doesn't take much more to put you outside the timing error limit acceptable for the PPL Skill Test.

I shall stick to teaching the conventional wisdom of measuring twice and cutting once. Accurate pre-flight planning using the best forecast wind using a whizz-wheel; Standard Closing Angle and Proportional Timing in-flight, MDR using max drift and clock face for diversions, backed up with slightly more map reading (NOT track crawling) during the diversion.

[homeguard]

MDR

Beagle,

Absolutely correct!

[hugh flung_dung]

Sorry AWL, that's all a bit OTT - you must see very different PPL studes to mine if they can cope with that

I think there's a much simpler way:

• plan your IAS to give an easy TAS such as 90, 100, 120, 150, etc (using IAS=TAS-2% per 1000 ft and -2% per 10 deg above ISA)
• calculate your leg times based on still air and TAS (2/3, 0.6, 0.5, 0.4, etc)
• modify the leg time based on the head/tail wind component percentage of TAS.

In other words:
Flying at 3000ft at ISA, 120TAS = approx 115IAS.
Still-air time is now 0.5 x distance
If flying into a 10kt HWC the leg time is increased by about 8%

So, if the distance is 40 miles the estimated still air time is 20 mins and the estimated time with wind is 20+8% = 21.6 mins.
By CRP5: time = 21.8 mins.
QED

I think the wizz wheel is a great device but lots of PPLs don't seem to bother with it; also, if MDR isn't practised regularly they are unlikely to be able to use it if they need to divert. People need a way of visualising the effect of the wind and a simple set of rules with minimal sums. Any assessments should be based on simple visual proportions of known values whenever possible (eg using the DI as an "analogue computer" to <calculate> the proportion of max drift, head/tail wind components and crosswind components).

Beagle: What's the "New Track Reference" method that you mentioned? I can't recall anything of that name.

HFD

[BEagle]

1. There should be no need to use the word 'about' in pre-flight planning. Exact calculations should be made.

2. The NTR method I have consigned to the trash can of memory. I vaguely recall that an observed angular error was multiplied by the reciprocal of the proportion of track flown since the last known fix, or something like that. Too much hard in the way of hard sums - and excess error from incorrect assessment of observed angular errors.

Why are so many people so seemingly wary of teaching the basics of the whizz-wheel? It's hardly difficult - I learned it at 16!

The idea of planning an IAS to make the TAS 'easy' is a new one on me. OK - on Hunters I used to fly at M0.8 plus or minus the headwind, so it was somewhere between .75 and .85 most times so that 8 miles a minute could be used for rough calcs, but a light aroplane has a very restricted range of IAS. To teach students to set an RPM which would give 96 KIAS is a waste of time - just fly at the correct cruising speed having spent a few minutes with the whizz-wheel prior to flight.

[The Trolls' Troll]

There seem to be two types of navigation under discussion, yours for teaching the PPL and mine for after the PPL. Yours is based on an accurate flight plan which is modified if necessary by adding bits on or taking them off the computed figures in response to changing conditions and that should be fine for a triangular route lasting 1.5-2hrs, but for a 200-300 ml navex with varied weather?
Mine is less accurate at the planning stage, but only because I deliberately use MDR to get the practice. But that changes in the air with the ability to get an accurate up-to date wind vector. Instead of modifying existing calculations, you do them again using MDR, or the instruments will give you the relevant heading and groundspeed, to get to the next waypoint. Thanks to the new, large clear design (which gives. a visual appreciation as well as a quantitative evaluation of the wind vector) repetition and monitoring of the wind vector is an easy task. Yes you have to fiddle with the instruments, but at least they are easy to fiddle with, unlike the Dalton and they measure distances and bearings on the map.
Point taken about MDR for learners. I suppose they’re near overload at the testing stage but later on?
Just daring to try something new in the conservative area of aeronautical navigation, a last attempt to modernise the traditional methods before they collapse under the onslaught of GPS.
Thanks for the comments and info. It’s given me a few things to think about.
AWL

[BEagle]

One other point. Who in their right mind would use a GPS to derive a wind and then use that with MDR methods to refine a plan? If they've got a GPS, all they'd need to do would be to cross-check DTK and ETA values with the pre-flight calculated values, then keep the CDI centred and enjoy the view!

And why not, indeed!

[Send Clowns]

Ermmmmm - because it is not a legal way of navigating, perhaps? Or because it causes drastic loss of situational awareness, and the CAA at least blame this attitude for the recent increases in airspace infringements?

I agree that correcting heading by the track error given by GPS and using the ETA function is better than MDR for that leg. However what if the GPS does not have a signal for the next leg? At least the person you refer to would have a wind more accurate than the forecast, if a little out of date. He also keeps in pracdtice with his MDR for use when it is really needed.

[hugh flung_dung]

Beags: If I understand your comment about NTR it's to take reciprocal of fraction gone and multiply it by closing angle to regain track at destination - not exactly "new", although I guess it depends on your vintage - I'm a '53; a particularly good year (BTW, my formative years were spent in Lincoln, flashing morse code message to the Vulcans from my bedroom window - why didn't you write down the address and visit?). This is the method that's currently in vogue in a number of schools (including mine) and I don't like it. Since so much time was dedicated to studying the planned track it seems such a shame not to get back onto it at the earliest opportunity rather than at the destination. SCA seems a good way of doing it (although my boss (ex- groupie TP) is adamant that it doesn't work at GA speeds) or simply to double the error to regain track at double the distance gone.

Accuracy is laudible if it's to do with nuclear safety or something else where all parameters are accurately know. Pretending to calculate headings and times to the nth degree in aviation is pointless, it's a bit like the GCSE candidate writing down all 24 digits from the claculator having used a series of approximate parametric measurements as inputs. "Garbage in garbage out" comes to mind.
The wind is approximate, the IAS is approximately flown, the height is maintained approximately and the track may require minor tweaks. I suggest that 21.6 vs 21.8 minutes is pretty damn good, especially if the stude then has a picture of what's going on rather than a series of meaningless headings and times without a "picture".

Please don't misunderstand - I teach and (almost) praise the wizz wheel but, post-PPL, the evidence is that many people don't use it and rely on the great god of GPS (a wonderful tool but doesn't help with the big picture). In my day job (that's giving the game away a little) part of my role is to innovate and to think outside the box. Applying that to GA: why shouldn't we work backwards and set the IAS to give an easy TAS? Why do we have to force people to use a device that they don't use after the exams? Why do we have to teach slide rules to people who haven't even heard of log tables and who don't know about geometric series or how electronic calculators work? Why do we have to teach one method for planned Nav and a different method for unplanned Nav (which, BTW, they won't need to use for 4 years post-PPL and by then will have forgotten)?
The way we teach people to fly was set down nearly 90 years ago - maybe we should re-think a couple of areas in light of educational and technological changes.

I hope this makes sense when I read it tomorrow, after the wine has dissipated.

HFD