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Pilot Navigation

Old 23rd Jul 2009, 14:45
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Pilot Navigation

Do any of the instuctors or examiners have any tips on Navigation? I'm doing navigation in my next lesson and a bit stuck on what to learn!!!!!! Can any of ya HELP me please!!!!!!!!!!!!
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Old 23rd Jul 2009, 14:52
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And in the next one, and the one after that probably ! So relax, listen to the brief and try to do what you're told !
 
Old 23rd Jul 2009, 21:21
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How about starting by considering it, not as an entirely new skill set, but merely an extension of straight and level flight, with occasional reference to a map.
In still air, if you start at a known point (A) and fly a steady heading at a steady speed for a given time, you will arrive at a destination (B), every time, without fail. The only reason this won't happen is if you induce errors by flying inaccurately or if you're not flying in still air - which is most of the time.

The "navigation" bit is all about learning how to calculate the heading and time to get from A to B, and making suitable corrections for the anticipated effect of the wind. Extra bits include pre-flight planning (devising a sensible route, checking the weather and NOTAM, formulating a fuel plan etc) learning how to check that the flight is going according to plan (comparing where you actually are with where you should be - some call it taking fixes) and making appropriate corrections if it isn't (revised heading and/or ETA). Hopefully you'll be taught a suitable work cycle whereby you divide your time between flying straight and level and looking out the window(most of the time), conducting routine airmanship checks (once every 7 or 8 minutes), liaising with ATC (if and as required) and consulting your map (occasionally). That should see you through the first couple of "navigation" lessons.

Thereafter you can anticipate learning how to cross controlled airspace, danger areas, MATZ etc, deviate around poor weather, cope with getting lost and incorporate the use of navigation aids and GPS into the plan to ease your workload. Finally to should learn how to fly to another, unfamiliar airfield having consulted the AIP for local procedures, frequencies, opening hours, availability of fuel, runway declared distances etc.

Enjoy

BJ
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Old 24th Jul 2009, 06:31
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Standard Closing Angle

....is the simplest pilot navigation technique; herewith my idiots' guide to the SCA method:


Most PPL text books give students a number of suggestions concerning methods of visual navigation. All these are based on the well-proven ‘1 in 60’ method which is a technique for calculating correction angles using estimates of off-track distance errors. Equally, it is also possible to make track corrections based upon estimates of angular track errors, a technique which is still quite popular.

However, most of these methods suffer from the drawbacks of either requiring relatively difficult mental arithmetic or correcting not back to the planned track with its associated pre-planned visual fixes, but direct to the next planned turning point. Recent advice from senior ex-CAA Examiners suggests that a rigorous navigation technique is required which instead does allow pilots to correct back onto their pre-planned track. Traditional techniques have not provided pilots with a simple method for achieving this; however a method originated in the RAF is available which makes track correction from observed off-track distances extremely straightforward.

Those of you whose eyes glaze over at the thought of elementary schoolboy trigonometry can skip this paragraph as far as the bold portion if you like, but for the rest of you it works like this: If you realise that you are a miles off track and wish to fly b miles back on to track, then you need to turn through an angle φ whose sine is equal to a/b. Now the 1 in 60 rule tells us that φ is more or less equal to (a/b)x60 and if you fly your distance b at v miles per minute for t minutes, then φ = (60/v)x(a/t). If a and t are made numerically the same, that is you fly for the same number of minutes as your number of miles off track, then a = t and a Standard Closing Angle φ of (60/v) can be used where v is expressed in miles per minute. Hence the SCA at 360 kts is 10°, at 120 kts it is 30° and at 90 kts the SCA is 40°.

This method is really only completely accurate when TAS equals GS; it was originally used for navigation in fast aircraft at low level where the difference between these two values is not significant. The error will be greater at lower speeds, but is quite acceptable as the SCA technique assists pilots in reducing track error to a point from which readily identifiable pre-planned visual fixes can be observed and overflown. Similarly, timing errors will be introduced with a large SCA as the aircraft’s along track velocity (more trigonometry, sorry!) is v cos φ rather than v. This can be overcome either by reducing the SCA and increasing the correction time correspondingly, or by making an appropriate timing correction. In practice it is better to return to track as soon as possible, but only if a simple method for correcting the timing error can also be achieved.

Considering the PA28 with a 90 kt cruising speed, things now become quite simple. The SCA is 40° and cos 40° is 0.766 which is as near as makes no odds 3/4, so what should have taken 3 minutes on track will now take 4 minutes on a 40° SCA, i.e. 1/3 longer. These values will later be used in summarising the SCA method for use by PPL students cruising at 90 kts. (In a Warrior at 105 kts, theoretically the SCA is 34° and the corresponding ETA delay is 1/4 the track correction time, but for all intents and purposes it’s easier just to stick to the same 40° and 1/3 as for the Cherokee).

It is also necessary to examine why the aircraft was off-track in the first place. Assuming that pre-flight planning was correctly completed, several factors could have caused the aircraft to be off-track. For example, was the DI correctly set against the compass and was the slip ball properly centred? Did the pilot fly the aircraft accurately on the planned heading? If the answer to all those questions is yes, then the only possible cause of the error (barring ATC or divine intervention) must be that the wind velocity was other than the forecast value – a not unknown phenomenon! Having regained track, due correction can also be made for the change in drift which can readily be deduced by reference to a drift line drawn on the map. Because, if the pilot flew the aircraft accurately and yet discovered a track angle error of ψ°, then when back on track and with the DI re-aligned, the heading may be altered by the same angle ψ to correct for drift. In the correct direction, of course!

To assist in making these estimates, consider now the subject of map preparation. The start point and turning points should be marked with a circle and the track between drawn in. Timing marks every 6 minutes may be added as must the exact elapsed time at readily identifiable visual fixes roughly corresponding to easy fractions of the way along the leg (to make proportional timing correction reasonably straightforward) and at the turning point. A single 10° fan line from the start point for each leg should be drawn, to allow assessment and correction of drift error as described above. Finally the heading (not track) for each leg should be written on the map and a note made of the W/V at the level being flown together with the associated max drift value, as well as the safety altitude. Estimating distance from the CAA ½ million chart is straightforward enough by reference to the known dimensions of ATZs, MATZs and, of course, the latitude marks.

Using the SCA technique is very straightforward. Let us imagine that we have been accurately flying the first leg of our navigation exercise at 90 kts on a heading of 040° when we notice that we are 4 miles left of track with some 7° of drift error as deduced from our single 10° fan line. The first correction is to turn right onto a heading of 080° and then to time for 4 minutes as we head back towards track. During this 4 minutes we can first reassess that it really was a 4 mile error and then jot down on the log that our ETA at the turning point will be 4/3 of a minute later than calculated and that there’ll be a 7° drift correction to apply when we’re back on track. When our 4 minutes are up, we turn back onto our original heading plus our drift correction, i.e. on to 047° in this example and recheck that the DI is properly aligned with the magnetic compass. With any luck and assuming that the wind doesn’t change yet again, our navigation exercise should now continue pretty well on track and we should only need to note the passing of visual fix points to revise the ETA at the turning point.

Although SCA has its sceptics, it is a very simple and easy way for pilots to correct navigation errors and to regain their pre-planned track and it’s the method I require to be taught to all new students. But none of this is going to be much use if a pilot hasn’t planned accurately in the first place, flown accurately or thought ahead!

If your instructor hasn't heard of this method, ask him/her to find out!
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Old 24th Jul 2009, 06:46
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I think Beagle has regurgitated a post he made some 5 or so years ago

SCA is good to get you back on track if that is what is required and I don't believe current CAA Examiner thinking is now as strong as Beagle puts it. Other techniques are far easier to apply as long as you want to get to your next fix.

SCA relies on some pretty big assumptions (TAS = GS - try that with a 35kt Scottish north easterly at 2000ft) and EETs can go out of the window. I'm a little disappointed that Beagle insists on it being the "method he requires to be taught to all new students"; I teach them all methods and allow them to decide which one suits them for a particular circumstance. Then again, I'm a NuLabour type who believes in choice
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Old 24th Jul 2009, 09:16
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SCA is good to get you back on track if that is what is required and I don't believe current CAA Examiner thinking is now as strong as Beagle puts it. Other techniques are far easier to apply as long as you want to get to your next fix.

Regaining the planned track unsing a defined technique in a reasonable time is required to be demonstrated.

It can be using SCA or other method or it can be as simple as realising that one should be "over there" and placing the aircraft where it should be. However, regardless of method used they all fall down unless something is done when back on track to try and prevent the same error repeating itself.

Fixing the aircraft position and tracking direct to the next turn point or destination when less than half way along track is very much frowned upon because firstly, the aircraft will no longer pass over the planned checkpoints and secondly, if the flight has been planned on the basis of terrain, obstacles and airspace within say +/-5nm of the planned track, should one decide to re-plan in flight for a new track between present position and destination then a new +/- 5nm corridor must be scanned in detail for terrain, obstacles and airspace.

One of the most important issues that is seldom explained is why use +/-5nm or +/- 10nm corridors when planning. If students understood the relationship between the accuracy of their navigation techniques and the size of the corridor it would be come obvious that unless one is starting from a on-track position it is possible that the errors expected could take the aircraft outside the planned corridor.

As long as the student is not moving their finger along the map and moving their eyes constantly between the map and the ground and the map then it is clear that some effort is being made to navigate the airraft rather than drive it crosscountry.

It must be remembered that SCA and similar methods will only bring the aircraft back to the "vicinity" of the planned track it will not put the aircraft exactly back on track. However, the error will be small enough to be corrected visually when closing in on the destination / turn point.

I find mostly that it is not tracking that needs better training but the ability to predict and adjust eta and fuel remaining / minimum fuel required when an unexpected change occurs.

Far too many instructors and students use the "fill the tanks" method of fuel planning i.e. the student plans what fuel is required but the tanks are filled and it is not ever checked if the fuel plan was accurate or not.

How many instructors ask the student to plan the fuel required correctly and on that basis chekcing that they arrive with at least departure fuel minus the planned amount in the tanks. If ATC require a hold or the flight has to divert round some showers then the student should be able to adjust the expected fuel remaining at destination accordingly.

Regards,

DFC
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Old 24th Jul 2009, 09:43
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Tongue in cheek.

I used to say to students, in a light hearted manner.

Do your P.A.T, then your H.A.T or you'll look like a tw%t.

Generally, if the power us not right then the attitude wont be right and trim not right. The concentrate on heading etc, etc.

Its just one of those things that a student will remember and it seemed to work OK.

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Old 24th Jul 2009, 16:31
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To the OP (I was tempted to say Master Bates but thought that would be too childish - oops, I said it ): the answer is simply that there are several methods for regaining track, but to avoid confusion you should let your FI teach you the method used at the school. Later you can explore the other methods and decide which one(s) you prefer.

I agree that SCA works well but it's better to tweak it when the wind gets strong or the speed is less than 90kts. To tweak for strong winds use SCA=3600/GS, to tweak for low speed use half SCA for twice the time.
It's important that everyone at a school teaches the same thing and at the moment we teach the double track error method which IMnsHO is nearly as easy and effective as SCA.
In practice SCA and double track error go well together and both benefit from a fan line from the start point.
The only method I don't like is the one which I was originally taught - closing angle based on proportion of distance gone and doing the base 1:60 sums - it's important to get back onto the prepared track line!

HFD
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Old 26th Jul 2009, 07:18
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Then again, I'm a NuLabour type
I'm amazed that someone would actually admit to that..... ; nuLabor has been the ruination of our traditional way of life and has swept away our freedoms in favour of its depressing surveillance society. A term first used by me and since widely used in the national press.

As for teaching a variety of navigation methods and letting the student decide, that is plain daft. Stick to one standard method and don't confuse the student with several different methods. The Flying School should have one standard method which all their FIs teach.
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Old 26th Jul 2009, 08:35
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Do you also have a standard method for x-wind approaches? Do you teach wind-up or wind-down? Do you prefer PnP over attitude for speed? (Rhetorical question as we've already had that discussion ) My point is that we should be teaching students to be pilots and by limiting the things we teach them we may just be teaching them to jump through a particular hoop. I know what I prefer and I also know what our CFI and tame examiner like to use. But, they are flexible enough to recognise the capability of a student using any particular method. Our students are not confused, they are shown a variety of methods, allowed to practise them and we then adjust our training delivery to meet their preferred (most comfortable?) method.

PS. The nuLabour was a vague attempt at humour. Must go, Ex 6&7 to teach.

PPS. Regarding SCA, whilst I'm not disputing that the CAA want people to get back on track rather than hit the next waypoint, I think this is exactly the sort of thing that should appear in Trainingcom.
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Old 26th Jul 2009, 09:01
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When would one actually use any of these methods?

If navigating by ground reference, with no electronics whatsoever, doing at most 120 kts or so, it is far more straightforward to use pilotage to get back on track.

Navigating using navaids, even just an NDB, it is far more straightforward to use the navaids to get back on track.

For real world navigation (i.e., not training exercises), any combination of pilotage and suitable navaids will do the trick nicely, with minimum effort and confusion and maximum success rate. I can't think of any situation when 1:60 would be the optimal choice, unless one is trying to DR across an ocean or a desert...

So what problem, applicable to PPL flying, is various reincarnations of 1:60 supposed to solve?

I was not taught any of that in my PPL training (although I did read up on and experiment with it afterwards), and I won't miss it.
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Old 26th Jul 2009, 21:48
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On a clear day, select something you can see in the direction you want to go and fly towards it. (as long as it's not another aircraft!) - it's what you do when you spot the airfield in the distance anyway!
On a more serious note, you must trust that if you fly the course you have calculated and the wind hasn't changed drastically there is every chance that you will arrive at your chosen destination in the time you calculated.
Also, as time goes on, you will find it easier to identify places on the ground from the chart.
Then, when you have your PPL buy a decent GPS like all sensible pilots do, still do your plog and check as you fly. but navigation with the assistance of a GPS leaves you more time to keep your eyes outside of the cockpit where they should be.
Then do some instrument training because this can make your life even more satisfying and give you that extra confidence.
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Old 27th Jul 2009, 08:40
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Well, for the last two posters, it is no good saying "Navigating using navaids, even just an NDB, it is far more straightforward to use the navaids to get back on track." or "when you have your PPL buy a decent GPS like all sensible pilots do," as this is someone still doing their PPL and they have to learn the basics and cannot at this stage resort to Radio navaids or GPS

I would say that if Bates wants something to learn before going in he could try learning the wizz wheel, though it is sometimes easier being shown this (yes I know electronic methods are better, but certainly in the UK you STILL have to know the wizz wheel for PPL!), he could also read up on the different ways of marking up the map - but do NOT go overboard on this, know how to calculate Max Drift (w.s.X 60/TAS) and apply it using the clock method.
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Old 27th Jul 2009, 09:41
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Well, for the last two posters, it is no good saying "Navigating using navaids, even just an NDB, it is far more straightforward to use the navaids to get back on track." or "when you have your PPL buy a decent GPS like all sensible pilots do," as this is someone still doing their PPL and they have to learn the basics and cannot at this stage resort to Radio navaids or GPS
My point was that I question whether to-a-degree calculations based on 1:60 really does constitute "the basics". Especially with the assumption that it is something few people will have a need for in real life, given that pilotage, GPS and radio navaids accomplish the same thing better.

If 1:60 calculations really is something that is only used during PPL training to "learn the basics", before you are allowed to navigate for real using any suitable means available, then that strengthens my opinion that it is not something that needs to be taught during PPL training.

Those who actually need it, or simply enjoy using it, can learn it afterwards...

Of course, that is a bit of thread drift prompted by the replies to the OP's question... But Black Jake already answered that anyway!
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Old 28th Jul 2009, 05:09
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Flying privately & commercially in Australia I used 1:60 all the time, even on straight legs up to 600nm across the desert. There are many, many areas where pilotage doesn't work. You can't just fly from one visible point to another - because there are so few visible points. You often can't even fly to some visible point that marks an on track position. You need some way to find an appropriate heading adjustment to arrive on track at a recognisable feature somewhere along track. And then some way to calculate the heading needed to remain on track afterwards. 1:60 meets those requirements.

It's not the only method eg drift lines are another method, but 1:60 requires no special tools or preparation other than a means to measure distance on a chart (scale rule, latitude marks, chart scale or whatever). I usually use my specially calibrated thumb but have also needed the accuracy of a scale ruler in particularly remote areas with little to see at a destination, turning point or next fix.

I used to have a scale rule with drift lines already drawn on it. It had the advantage compared to pre-drawn drift lines of not needing to pre-draw anything (duh) but also the origin of the drift lines could be anywhere, unlike pre-drawn ones. The disadvantage was its relatively large width compared to other rulers, and having to have that particular ruler available.

Standard Closing Angle (a special case of 1:60, by the way, with some parameters pre-computed or otherwise constrained) will get you back on track however it has limitations. It won't necessarily get you back on track at an easily recognised feature (or even the only recognisable feature in a reasonable distance). You're stuck with arriving back on track at wherever it leaves you, irrespective of whether anything noticeable is there or not. Because the track interception point is based on time and not a fix or pinpoint, it's only a DR position. It also has the limitation that if there's a significant wind change during the intercept then how does the SCA-limited 1:60 method adapt? It doesn't. At least, not easily. Not the best way to avoid getting lost in the middle of nowhere, in my opinion. I've used it, and in some circumstances it's appropriate, but it doesn't cover all situations.

Other navigational techniques include using funnel, line and likely area boundary features, deliberate track error if a line feature crosses through or near the destination, position lines (visual, radio & running position lines) and even pilotage to feature hop from one confirmed feature to another.

I'm of the belief that if you have a suite of tools so that the most appropriate one for the circumstances can used then you are far better off. Some tools are particularly specialised, others more generalised. If you *must* only have one tool at your disposal then I favour a generalist tool like 1:60 and not a single solution tool like SCA (or funnel features or whatever). I can't think of an occasion where I taught a single method although I *favoured* - but not exclusively - 1:60 for its generalist application. Christ, I had one student who held Masters Degree in Mathematics. His preferred method was mental trig where I used 1:60! No matter. Use the best tool of many that suits the job is my preference & that's what I taught.

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Old 28th Jul 2009, 13:37
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As for teaching a variety of navigation methods and letting the student decide, that is plain daft.
Only to a point. No matter what method one uses there will be situations where is will not work. For example, twice the track error will not work past half way and SCA will not work beyond the point where SCA will get you back on track after the destination or turn point and of course that point depends on a host of factors.



bjornhall,

I have no problem with the PPL student recognising that the constant heading they have been flying is in error and they are off track followed by the aircraft being visually positioned to a point that is on track. However, I expect that having done so, the next heading flown is a sensible one which should not repeat the error.

For the CPL student, I (and their future employer) expects a more efficient method of regaining track.

Simple pilotage?

When one looks at it in detail it gets quite complicated. With constantly varying groundspeeds and various unknown delays being able to predict the fuel remaining on arrival at destination is quite difficult. Pilotage in reduced visibility of say 5K requires fequent reading of the map unless one knows the area well. Pilotage limits the student to either spending too much time looking at the map, only flying in known areas or along known routes.

Funfly,

On a clear day, select something you can see in the direction you want to go and fly towards it. (as long as it's not another aircraft!) - it's what you do when you spot the airfield in the distance anyway!
That is the most common error made by students - They have held a constant heading for the past 30nm and it is taking them directly to the destination - a 100% score in terms of navigation, efficiency and following the flight plan. Then they spot the airfield and the next thing we know the heading has changed and the aircraft is drifting off track. OK, they get to the airfield but not on the panned track and not in the time they expected. Of course, that is ignoring the students that are flying with 30 degrees of drift and expect the airfield to be in their 12 O'Clock.

In terms of visual navigation I provide pilots with the tools so that they can operate in accordance with the privileges of their licence.

-------

While everyone talks about SCA in terms of regaining track after a track error has been discovered, the SCA method can also be used to position the aircraft Xnm to the left or right of track for a period and then regain track. For example;

You are flying from A to B at 3000ft. The chosen heading is maintaining track and you will pass over XYZ airfield in about 15nm. You call them and find out that there is aerobatic practice in the overhead. So you want to position the aircraft 3nm right of track - simple turn onto the sca heading for 3 minutes and hey presto, you are 3nm off track. You then fly the original heading until past the aerodrome and apply SCA in the opposite direction top regain track in 3 minutes.

What makes the above sooooo simple is that you don't even have to see the airfield to avoid it!

The techniques we teach for navigation are not confined to getting back on track when there is an error!

Regards,

DFC
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Old 28th Jul 2009, 13:55
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Pilot Navigation

In my days flying VFR in the west of New South Wales, I used a system of the first reference point that was the aerodrome that I was departing from and the second was a reference point or area on the track to the destination. The second reference point would be 10 or 15 nm from the take - off point. I flew a steady heading to make good the desired track. This heading took into account the actual wind of the day and so in due course we would arrive at the destination.

It worked for me.

Tmb
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Old 31st Jul 2009, 02:36
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I usually didn't use my departure place as the starting point for my enroute groundspeed & 1:60. Winds are too different at altitude compared to the surface, TAS is changing & so is GS. The higher the cruise altitude then the worse the problem usually becomes. Instead I'd do a 'double the track error' correction about half way up the climb to be pretty close to track at top of climb.

I use a convenient feature just after TopC to start the GS & 1:60. By then the wind isn't so variable and both TAS & GS are constant which makes for more accurate navigation. If it was a really barren area then I'd use whatever feature I could find as close as possible to TopC, even if was during the climb. Worst case was using the departure point. I prefered somewhere just after levelling off but sometimes there's not much choice.
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Old 31st Jul 2009, 07:48
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Pilot Navigation

Tinstaafl:

In a C172, VFR, the final cruising altitude is quite low and in the region that I mentioned, the possibile change of wind direction in the lower altitudes for the enroute times used, did not cause much of a problem.

It did work for me.

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Old 31st Jul 2009, 17:01
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Even in a C172 I'd try to get high. 6 or 8000, depending on wind. If at MTOW in summer then climbs even to the lower levels can be slow, extending the period not in cruise conditions. I just found it easier to not to include a 'built in' nav. error at the start. Especially on longer legs over the desert.

Certainly around the East Coast it's not really practical. Airspace limiting the climbs & routing, for example.
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