Importance of accurate course setting in overhead

[beammeupscottie]

This is going to sound like a stupid question, but I'll ask it anyway:

When you go off on a cross country, and set course in the overhead, how accurately overhead the runway must you be prior to taking up your track, to avoid flying a parallel course to the one you want to follow.

For example, (in the extreme), if you took off, flew around, and missed the aerodrome, then set course 10 minutes later, you would be flying a parallel track to where you wanted to go. I know this is an extreme example, but hopefully, It'll give an idea of what I'm getting at.

Thanks . .bmus

[Keef]

Weeelll...

If you were three feet away from the runway centreline when you set heading, then you're going to be 3 feet out at the other end, plus the 2 miles for the difference in the wind.

If you're approximately AT the airfield, that'll do. You should certainly see the airfield at the other end, if you were destined to do so in the first place.

Remember - you have to keep checking your position against the map and the view outside anyway...

[Chuck Ellsworth]

Lets try a little logic to answer your question.

We will examine two senarios when setting course and then staying on track when navigating VFR and map reading.

Senario number one:

We set course at one hundred feet above the airport runway and fly the trip at one hundred feet.

Obviously remaining right on course will be necessary as our field of view of the ground ( Your track ) will be very limited. And if we wander several miles off track getting re oriented will be a real problem.

Senario number two:

We set course at one thousand feet above the airport and fly the trip at one thousand feet. We now have a far greater field of view to map read our track and wandering a mile or so off track is easy to correct due to our increased field of view.

. .Try starting your mind picture from this simple example of map reading.

Then do not get to carried away with all the exotic problems and solutions that will be part of the training process, in other words don't let bull**** baffele brains as it really is very simple to navigate VFR with the proper map and the proper picture and understanding of what you are doing.

Here is a hint:

Note the point of departure then find the point of arrival, make a fold of your map from the start to the finish of your trip, jump in the flying machine and map read the track by following the fold crease on your map. So you don't even have to draw a line with a pencil or pen....for distance measuring use the side of your thumb to determing milaege. Anyone who trys to tell you that you must be accurate to the mile and to the minute is just missleading you.

. ...................

The hardest thing about flying is knowing when to say no.

[FNG]

One technique that you might try is selecting an "entry point" for your nav plan, such as a clearly recognisable road junction or other prominent feature a few miles away from your departure aerodrome. You climb out of the circuit, get yourself all sorted out, then run in over the entry point at desired height, on desired heading, at desired speed, hacking your watch as you pass over the chosen feature.

[Whirlybird]

FNG got there before I did.

This is not at all a stupid question, considering the way nav is usually taught to PPLs. I too was taught that everything had to be 101% accurate. But it doesn't.

If you leave the airfield and set heading immediately, you'll be circuit distance from where you want to be, at the most. And since you can see the runway from the circuit, you can see your next turning point from where that'll take you to (useful to note it though, or you'll make a heading correction you don't need). Very simple really, once you know.

On a different but related point, your compass has markings at 5 degree intervals, so can you fly to the absolute accuracy you will have worked out on your whizwheel? This is expected in ground exams and for your instructor, but in reality it doesn't matter. If you're 5 degrees out, you'll be five miles off track 60 miles away (1 in 60 rule). So as long as you fly accurately and check ground features every ten miles or so, you'll never be more than a mile off track. And if you can't see that far you should be on the ground.

This is not an excuse for incomplete pre-flight planning or sloppy flying. It's just that from what I've seen there tend to be two types of PPLs: those who check everything to the nth degree, and those who've given up all that as being impractical, draw a line on the map and hope for the best, or use the GPS. So I think the PPL course needs a lot more in the way of understanding of what VFR nav is really about and what is actually needed in practice. Anyone else agree?

And for those who care, I still use my whizwheel. I actually rather like it.

[tacpot]

If you are monitoring your progress along your planned track, you will probably be making a heading correction at either the quarter-way ot half-way points anyway, so any error introduced by setting out from somewhere ever so slight different from where you had planned leave from should be eliminated by this course correction.

The other posts have it right, you don't have to be 100% accurate. VFR navigation is visual navigation, if you can see how far off track you are, you can make any correction you need to.

Often I will set course from a local landmark 3 or 4 miles way from the field, navigating to the landmark visually, i.e. not worrying too much about the time for that short leg. Into that leg I factor the fuel to climb to cruise altitude, I do calculate a heading to fly, as it's more efficient to take account of the wind than ignore it, but I only use this heading as a guide, as I won't necessarily know from which point in the circuit I'll be starting from, e.g. if the runway is changed between flight planning and departure.

The landmark I use is such that if I can't see it to navigate to it, I shouldn't be flying anyway. But this approach is driven to some degree by the fact that my home field has Controlled Airspace above it, so we can't set course from the overhead normally. Setting course from a nearby landmark is certainly described in the Jeremy Pratt PPL books, so it counts as a valid technique in my book.

[ 22 February 2002: Message edited by: tacpot ]</p>

[niknak]

A small, but VERY important point;always check before you get airborne that you can set course from the overhead.. .At our place, because of the close proximity of a H24 fast jet military airfield, overhead joins and setting course from the overhead is not permitted.. .Even though this is clearly published, and pilots are briefed if they ring up prior to departure, we still get requests from them to carry out the manouvre.

[Chuck Ellsworth]

Setting course overhead:

Only in the goofy makebelieve world of ab-initio flight training could someone think up such a waste of time as the overhead course setting.

In the real world of flying you plan your trip so as to take off and conform to the traffic patterns of the airfield you are using to set course when safe to do so.

In IFR flying we are given SIDS ( Standard instrument departures ) in our clearances, once airborne the SIDS are usually cancelled by ATC with heading and climb instructions. Can you in your wildest thoughts imagine jets climbing for an overhead departure?

VFR map reading is straight foward, you compare what you see on the map with where you should be. If you are not on track change heading sufficient to fly yourself back to the desired track then maintain it as bset you can.

Whirley brings up a good point, the stupidity of planning for heading accuracy that is impossible to maintain. When flying you will end up averaging the compass (H.I.) readings, as you gain experience your averaging will become more precise.

Then one day you will be able to roll your cigarettes whilst holding the localizer dead center to the runway. Then you can sit at your computer making a fool of yourself because you are bored to death. I can't wait until I get back to work.

.................... . The hardest thing about flying is knowing when to say no.

[Aussie Andy]

beammeupscottie = its not a dumb question at all mate - I remember puzzling over this as well. This is a function of the way we're taught, as everyone else has said. Everyone else has already given you the practical answers you need above.

I actually think the way we're taught is OK because it gives us a step-by-step fool-proof approach... however, the trick is to realise as time goes on and you gain experience that you can cut corners and relax a bit with it. But until you feel OK with this, definitely keep asking the "dumb" questions!

Enjoy the weekend everyone - if the bl**dy wx lets us!

Andy

[twistedenginestarter]

My advice, particularly for any flight tests, is to climb overhead. You have to get to the right place and within 2 mins of estimate so why make things more difficult for yourself?

[Beethoven]

Overhead to overhead is obviously the most accurate but means nothing if the destination does not allow overhead joins,which many dont.Just think of your field of vision from 2500 feet.All that matters is that you can SEE your destination at the end so that you can adjust for your join.Its no good putting yourself overhead a field only to be told to join right base!!I would say,that as long as you depart in sight of your departure field,then if your plan works out,you should arrive in sight of your arrival field and that,to me,is a good vfr nav.As for a PPL flight test,just do as your instructor says and experiment when you have your licence,as you will find,there are many ways to navigate successfully.. .Ludwig

[Chuck Ellsworth]

Within two minutes?

Within two minutes in how many miles? Or better still exactly what is the two minutes requirement?

As to the overhead departure and overhead arrival why would anyone with half a brain require such an unorthodox procedure in 2002?

[Whirlybird]

Cat Driver,

An overhead departure makes no sense at all usually. But it's perhaps fairly useful for student pilots who have difficulty understanding nav; I remember on my qualifying cross country getting very confused because a power station a few miles away wasn't where it should be. Just flying was enough for me at the time without working that out; I worried for several miles until I realised my heading was working, and only realised afterwards on the ground what had happened. But for anyone with even a minimal amount of experience it makes no sense at all.

Overhead joins I have mixed feelings about. It does mean you can circle around in safety and work out how to join the circuit, which can be very useful for the inexperienced, especially those of us with spatial perception difficulties. <img src="eek.gif" border="0"> I used to always do it, for that very reason. Also, there are a lot of quite busy airfields in the UK with only A/G radio. Some would say that it makes sense to have everyone joining those overhead, well out of the way, descending deadside etc, rather than having them all joining the circuit where they feel like it. I'm not sure, since it means the whole world can theoretically be flying around overhead at 2000 ft in any direction. I do remember one time when it made a lot of sense; I arrived at Shoreham at the same moment as an aircraft making an emergency (or do I mean precautionary) landing after a vibration problem mid-channel. I'd been earlier told I could join the circuit etc, but I saw what was happening, asked if I should wait as I could see all the fire engines etc and knew they wouldn't want anyone else around. I then circled overhead until the aircraft landed safely before asking if I could now descend. Probably easier for both me and ATC then anything else, under the circumstances.

But do we get too hung up on overhead departures and joins? Yes, definitely. And getting asked to join overhead in a helicopter makes no sense whatsoever - and it happens! <img src="eek.gif" border="0">

[Rusty Cessna]

My opinion:

Yes, Overhead to Overhead is the shortest route, but I have to agree with the points raised that if you are actually inbound to an aerodrome and an overhead join isnt either available or issued, then what? In the practical world I would beleive a lot of pilot's stop flying their nav route accurately when they either get visual with the field or have received the joining info,I'm talking VFR here. I don't know a lot about it but as someone said when you start doing IFR stuff SIDs start to come into play.

Everyone seems to be clear about reasons why Overhead to Overhead is or isn't practical, but something that I dont think has been mentioned yet is the actual performance issue. The approach I take now to planning routes is I start the route from either a VRP or a prominent feature, (as FNG, tacpot and whirly suggested), this enables yourself to get sorted and start the leg immediately.

The reason I take this approach is because I find it easier, I have time to get everything sorted and once I'm over the VRP all I have to do is "hack" the watch. Another reason (probably because I'm lucky to have VRPs within 3 miles North East and West of my field) is that by the time I have climbed to the overhead I could have got to my VRP, which is also a little more en route.

That's just my opinion, I prefer the VRP approach, as does my instructor, I was taught both, but decided against the overhead route. I won't bother restating the issues already raised about the approximation involved with flying routes such as compass markings and drift, but I do think they are apparent, however, adequate post PPL experience is needed before you can accruately approximate I think, so best stick to your plan and definate drift corrections.

With regards to the test, I would do what you have been taught, this will probably be what you are most comfortable with, be as precise as possible, there are limits on the test, I think its + or - 100 feet on altitude holds, + or - 10 knots on speed, and 2 mins on time, but I'm not deffinate on that. I tried to be as precise as possible, 37 mins was the calculated leg time on my test, 37 mins 13 seconds I think was the actual leg time, it works!

Of course this is totally relative, sometimes overhead to overhead may be appropriate, I woul'd be reluctant to say "i'm only going to fly this type of nav", it restricts your options.

One final point, as tacpot suggests, I'm very wary where and when I do my drift corrections, unless you have the post PPL experince to approximate accurately, which I yet don't , I would stick to correcting for apparent drift at quater or half way points, this is again my prefered method, simply because its nicely spaced intervals, that are easy to calculate using the drift angle, closing angle method, but hey, ways of correcting drift is another thread totally!

Gawd that was a long one! hope it makes sense and helps.

Rusty.

P.S as Cat river says, Height = Sight, and yes I know spelling is awfull, but I'm tired ;-)

[ 23 February 2002: Message edited by: Rusty Cessna ]</p>

[twistedenginestarter]

Cat Driver

My point is that the only reason most people do this sort of navigation is because they are in training. Once you've got your CPL (this is in the UK) you wont bother with this again. You either become an airline pilot or use your GPS, VOR etc.

I believe for the CPL you need to arrive at your turning points within 2 mins of estimate. The legs are of the order of 50-100 miles. I guess you can correct your estimate at half way. I'm not sure at what point you can no longer adjust your eta without failing.

Clearly you would never climb in the overhead for any real-world reason.

[Zlin526]

I think Catdriver talks a lot of sense.. .Whats wrong with setting course from a point, say a mile from the airfield??? My own airfield has parachuting all day, everyday, so setting course overhead is for bozo's. Take off, fly to the selected point and then turn on track your destination - easy. . .I admit CPL and ATPL standards are higher, but why can't the ordinary PPL also have high standards too? Reminds me of the guy who mistook his destination of Compton Abbas for Bournemouth a few years ago. A large Tarmac runway 2 miles from the sea as opposed to a small grass strip 40 miles inland! Would setting course overhead the departure airfield have helped him??? Makes you think about pilots personal standards....... <img src="frown.gif" border="0">

[ 24 February 2002: Message edited by: Zlin526 ]</p>

[Chuck Ellsworth]

Twistedenginestarter:

When I learned to fly we were taught several very important things, first and foremost was good airmanship, which simply put is common sense.

(By the way before I was allowed to fly for my first employer I was required to spend several years working as a mechanic in the hangar.)

Common sense dictates that "all" pilots conform to a safe and workable pattern of flying.

Overhead departures and arrivals are not the norm for aviation if they were everyone would be required to use that method. Just imagine the chaos that would entail.

To suggest that a student pilot cannot start a x/country from any portion of an aerodrome traffic circuit is just plain stupid. I defy anyone to convince me that you cannot see the airport from any portion of the circuit pattern unless you are in cloud.

Now to examine this mindless notion that a student must start from overhead so as to be able to get an accurate fix for time and course corrections that is just not intelligent thinking. Because once on route there is no guarantee you will have check points that are as positive as the airport you just left. So common sense dictates the student should start the x/country navigation from any point and fly to any other point by "map reading" and accurate heading and time management.

Remember the bureaucrats who dream up all these exotic requirements for flight training and written exams are not necessarily the brightest and most gifted among us.

Flight instructors are victims of the system.

................

. . The hardest thing about flying is knowing when to say no.

[FNG]

Twisty, forgive me if I am misreading your post, but are you implying that primary navigation skills are just for studes, and that, once licensed, you can just switch on the GPS, dial up the VOR, and have a snooze?

[twistedenginestarter]

FNG

Exactly that.

You really must embrace technology when it provides a clear-cut advantage.

I learned to fly using visual navigation because they didn't put radio aids in any of my FTO's singles and I couldn't afford a Decca at the time.

Nowadays everyone can have gps and I haven't been in a plane for 30 years that didn't have VOR and ADF. So if you want to fly from Newcastle to Lands End it would surely make sense to use radio aids and gps as your prime navigation. If the GPS/DME says you are two miles from controlled airspace then most likely you are. What's the point in trying to work out which dual carriageway that is crossing which railway line?

Unfortunately there is no promulgated Modern VFR Navigation Method. Perhaps we should develop one on a thread here?

[ 25 February 2002: Message edited by: twistedenginestarter ]</p>

[Chilli Monster]

Twisted

I thought there was now by the introduction of the JAA PPL which includes the use of radio aids in the syllabus.

Of course,what happens when the alternator/battery fails <img src="wink.gif" border="0">

But to get back to the original thread: +/- 5 degrees is normally a good enough accuracy for PPL flying - but don't expect to do it from the overhead - pick a start point on track. It's a lot tidier form of nav.

CM