Accuracy of the "1 in 60" rule for navigation.

[facthunter]

If you aren't map reading at all you have a big disconnect that I suggest you should maintain when flying X country.. It's a good policy in aviation to never entirely rely on ONE source of information but have an entirely separate one as well available to confirm . Recall the MT Erebus DC-10 event

 

     A "Go To' from any place/point doesn't actually define a  track on a hypsometricaly tinted WAC map (Height contours) which is absolutely required to determine a LSALT  (lowest safe) for your ACTUAL track. Ie the one you end up flying as distinct from the planned one.  Prominent hills are also amongst the highest in reliability for position fixing. Against your waypoints you should have an actual time of arrival and a fuel (plus or minus ) notation. (A Howgozit) in case you have to divert in flight you have recorded positions at related times to go back to. If you are recalculating your in flight reserves (% of flight time remaining) all this is part of doing the proper process of  a flight FUEL log.

 

        It's easy to get lulled into a false sense of security with a GPS. I think most of us have found that out at some time or other. Nev

 

 

[old man emu]

I always found pre-flight planning and then the execution of that plan part of the enjoyment of a cross-country flight. The closer the actual flight corresponded to the planned flight, the bigger the pat on the back. I reckon it would be boring to follow a cursor on a screen during a longish flight. Even sight-seeing at the countryside gets a bit tedious at times.

 

 

[Jabiru7252]

I'm dyslexic with numbers .

 

Bernie . 

 

8 out of 3 are to some degree...

 

 

[facthunter]

I asked for a dyslexic train from antSa at easter. next Century.  Nev

 

 

[Student Pilot]

Never used 1 in 60, I look out the window and use maps before GPS. Now just use GPS. 

 

 

[Bleve97]

Well, well, well. I based my assessment of the 1 in 60 rule on the assumption that you would measure how far you had actually flown, not how far you had hypothetically gone down the original track. The video uses the example of the intended track. That version of the 1:60 rule will be accurate up to about 10 degrees off track, as others have said. Bob Tait, in his RA-Aus cross country endorsement seems to switch between methods. 

 

 

Using the original track is easier because you don’t have to measure the hypotenuse. 

 

 

The hypotenuse is the better method for navigation because, for example that is the only method that tells you your ground speed and allows you to determine what the winds actually are - not that I would attempt to do that alone in flight. 

 

The 1:60 is essentially a dumbed down version of the Small Angle Approximation. It works because the hypotenuse and the adjacent are close enough in length that it doesn't matter in the case of using a compass or gyro for navigation in a very imprecise environment.  See https://en.wikipedia.org/wiki/Small-angle_approximation

 

In the charter world, if you did any of this, you'd be looking for a new job.  That's what TSO'd GNSS is for.

 

 

[facthunter]

That concept is what caused the Mt Erebus disaster. Don't just base any critical operation on ONE information source. You can't beat tracks on maps especially for lower altitude ops and colour tinted contour lines. You can do it digitally. While the LSALT is not a concept that strictly applies to VFR to "FIND" a LSALT you need something like a WAC chart to derive one for non standard routes where that info is not provided. Nev

 

 

[facthunter]

That concept is what caused the Mt Erebus disaster. Don't just base anything on ONE information source. You can't actual beat tracks on maps especially for lower altitude ops and colour tinted contour lines.  . Could be done digitally. Only way to derive a LSALT on routes when it's not shown on a chart. LSALT is not an element of VFR strictly speaking but It's helpful if things go bad. Smoke fog etc. WAC charts are good for plotting with regard to terrain.  but I regard  google maps as almost essential for planning the Visual situation where you are going if you are unfamiliar with a fairly complex ill defined aerodrome "somewhere". You need all you can get to do these things well. Good planning pre flight makes the job easier and safer.

 

 Sorry ran out of edit time due to a phone call hence the repeat performance . Nev

 

 

[Student Pilot]

Agreed, use maps as well. LSAT has no place in VFR really, if it's non VFR then no fly.

 

 

[turboplanner]

Agreed, use maps as well. LSAT has no place in VFR really, if it's non VFR then no fly.

 

LSAT is for IMC or NVFR, however.......

 

If you get caught out by weather, knowing the LSAT for your route envelope gives you immediate knowledge of what you can drop down to, and breathing space, and you have your course marked on a WAC chart, you can immediately see which way you can turn without being trapped by high ground, and you can plan a way out by immediately finding the low ground, and you can avoid being trapped up a narrow valley and so on.

 

Just those things would have saved several lives in the past few years.

 

 

[Yenn]

I wonder how we managed to fly years ago, before the time of GPS and without VOR capabilities. I managed to fly from Rocky to Archerfield, using just a DG. I also flew fairly extensively in Vic and SA without missing my destination, usually in good VFR weather, but occasionally I had to divert because of poor weather.

 

I really think that to rely on anything that requires connections to a computer means that the old alternative should be learnt.

 

I have had failures of GPS equipment resulting in being given incorrect headings to fly. I have at this time one GPS which has completely failed, luckily I use it for bushwalking not flying, but that can have serious consequences if I had to rely on it.

 

 

[Mike Borgelt]

Yes an individual GPS can fail which is why you have two or three or four. Use ones with internal, charged batteries and plug in to aircraft power.

 

Very old GPS receivers can have a problem. There was a GPS week rollover in 2000 and another in April 2019 so if your GPS doesn't seem quite right (slow to acquire satellites and easy to dropout) your particular receiver may not have firmware that handled it. There may be a firmware upgrade available.

 

Don't count on a TSO'd GNSS being any more reliable than your iPad, Android device etc. It just means it was designed and tested to a specific set of environmental conditions and to specified performance.

 

Any GPS receiver nowadays is as accurate as any other in a aircraft, including the TSO'd ones.

 

TSO'd GNSS systems are expensive. Easy way to get better reliability is redundancy. You can specify every part of a system and rigorously test or you can look at what the overall system has to do. The latter is usually a cheaper approach and easy to make more reliable. TSO'd GNSS systems are not more accurate than any other GNSS system unless you have augmentation. Even that can mostly be added to to your off the shelf GPS. Do you really need 2 cm accuracy of position? Isn't 10 meters good enough?

 

The point about the modern equipment is it gives you more time to look out and manage the flight. Diversions are easy too. Webcams from airfields and significant points. Live METARS. Lost of good information, not just navigation.

 

I also don't want to run in to somebody who is head down with map, ruler, whiz wheel etc for several minutes at a time.

 

I've taken evasive action several times on cross country flights while enroute. The other aircraft in each case showed no signs of having seen us.

 

Last time was going in to Caloundra from the south. About 10 miles out low enough to just make a shadow on the ground my wife noted there were TWO shadows. Quick look around and nothing, no warnings on PCAS (tells of nearby transponder returns) so figured he'd be below and in front and so when lowering nose there he was, just below and to the right, 200 meters converging slowly  and we had an overtake.  Low wing two seat ultralight returning to Caloundra. Would we have hit? Probably not but it sure would have been close. Turned right to keep him in sight while passing behind. Probably counts as in vicinity of airfield rather than cross country. Didn't hear any radio calls from him.

 

 

[turboplanner]

Last time was going in to Caloundra from the south. About 10 miles out low enough to just make a shadow on the ground 

 

I don't think he would have his head down doing 1 in 60 calcs at that point, although you never know.

 

 

[Student Pilot]

Couple of things, firstly I have been using GPS (For work) since they came out commercially available, only once has it stopped working, just after they first started being used, that was for half an hour. That's since around 1991. Next VFR flying is just that, looking out the window. If you are worried about flying into rising ground then knowing LSA won't have any impact, you shouldn't be flying that low. Yes I know weather can throw curved balls, training should cover this.

 

 

[Mike Borgelt]

In 1991 the satellite constellation was not complete. There were outages when you couldn't get a fix. The 1991 Gulf War had plenty of times when GPS wasn't available when the coalition forces were trying to locate for later reference, Iraqi graves in the featureless desert.

 

So tell me guys.  Suppose I'm going to fly my BD-4 to New Zealand via Lord Howe and Norfolk Islands. It is well with the capability of the aircraft. How do I find the islands? Dead reckoning or multiple GPS's?

 

 

[turboplanner]

In 1991 the satellite constellation was not complete. There were outages when you couldn't get a fix. The 1991 Gulf War had plenty of times when GPS wasn't available when the coalition forces were trying to locate for later reference, Iraqi graves in the featureless desert.

 

So tell me guys.  Suppose I'm going to fly my BD-4 to New Zealand via Lord Howe and Norfolk Islands. It is well with the capability of the aircraft. How do I find the islands? Dead reckoning or multiple GPS's?

 

Well since we're in the pretend area, after reading "We the Navigators" and trying it out. I'm pretty confident about flying direct to New Zealand by the stars only. The Pacific Islanders used to travel longer distances than that and not only hit a minute island, but arrive at the entrance to the reef.

 

BTW you keft out the Navigation Beacons I would probably use as a backup.

 

 

[Jabiru7252]

Well since we're in the pretend area, after reading "We the Navigators" and trying it out. I'm pretty confident about flying direct to New Zealand by the stars only. The Pacific Islanders used to travel longer distances than that and not only hit a minute island, but arrive at the entrance to the reef.

 

BTW you keft out the Navigation Beacons I would probably use as a backup.

 

Yea, but out all the trips they did I bet most were lost at sea. These days we seem to create 'touchy-feely-stories' that defy the odds. Some are so ridiculous, it's laughable.

 

 

[turboplanner]

Yea, but out all the trips they did I bet most were lost at sea. These days we seem to create 'touchy-feely-stories' that defy the odds. Some are so ridiculous, it's laughable.

 

Others are well documented though.

 

 

[facthunter]

Why does it have to be ONE or the OTHER?. Your line drawn backs up the GPS. /inertial/radio nav. or whatever you are using.

 

    1 in 60 is easy so you can do it in your head .  It's no more difficult than meeting a clearance to be at a certain level By (waypoint" whatever"..) or hold at Bindook  AT   FL180.. or meet the level requirements in Victor One .   Nev

 

 

[Bleve97]

Others are well documented though.

 

https://en.wikipedia.org/wiki/Survivorship_bias

 

You don't hear from the ones that didn't make it.

 

 

[turboplanner]

https://en.wikipedia.org/wiki/Survivorship_bias

 

You don't hear from the ones that didn't make it.

 

Have you read "We, the Navigators?"

 

 

[Yenn]

Modern pilots seem to think that because GPS works so well, that they should not have to have any knowledge of DR navigation. That works well while there GPS keeps working. Than what?

 

 

[Flyingfish]

iPad shutting down when too hot seems to be the most likely to affect us - much more likely than satellites being unavailable. Happened to me a couple of years ago when flying through the Sydney basin (was glad to have paper maps and radio frequency notes handy), and recently even before take-off from home airfield on a 35° day.

 

Other similar equipment such as backup iPads would be equally affected at the same time. Perhaps panel mounted aviation GPS instruments will handle heat better?

 

 

[old man emu]

Absolute trust in the GPS leads to absolute trust in fuel gauges. This misplaced trust could leave you dead-sticking into a paddock, but at least you would know where you are.

 

 

[Mike Borgelt]

Depressing. Having been told that the backup for a GPS is one two or three more, all with independent power supplies we still get silly posts.

 

Turbs, why don't you please depart for NZ using stellar navigation? Report back in when you make it.

 

Lord Howe island has ONE NDB for a beacon. Great. the chances of that failing while you are en route is probably like that of a single GPS failing, probably significantly more. There is only ONE.

 

Pilotage and DR aren't going to find you that island. If the entire GPS system goes down - well that is extremely unlikely. There are 24 + satellites and 3 ground  stations all tended by some very dedicated people from the USAF. If it all goes down WW3 has started.