ADS-B Optimism

[jrenwick]

John, I think it's more accurate to say that most aircraft do NOT fly directly between two points labelled "A" and "B". They fly between B, F, H, Q, T, and W.... to and from "A".

Furthermore, they do not fly exactly ON the direct courseline, even with RNAV. They depart the runway, climb on a random course to a point outside a traffic-area...THEN hit "Direct" and fly to the destination. (In fact, I'll bet the average pilot RE-directs toward the destination... or toward a random arrival-point in the area...of the destination, several times during a flight. When was the last time you actually didn't have to go around a particular airspace, or cloud, etc etc. and then RE-hit "direct"?)
In other words...with most aircraft RNAV equipped, ...there are few magenta course-lines from which we should all offset to the "right" thereof.

I may not be "most" pilots, but my practice is to set up the GPS before takeoff. Either a "Direct-to" or by actually programming a flight plan that can be reversed for the return trip. I usually then join that course once I'm in the air, rather than fiddling with the GPS while flying. But I take your point. Maybe changing my habits would improve safety!

[170C]

Regarding George's last post, I have been accustomed every since I got my first GPS to deviating either to avoid a cloud, some airspace or due to just not staying on course and from time-to-time hitting "direct to". Now as I am learning (hopefully) to use ForeFlight on my iPad, I have not yet found a way to do change the route (if I am off a bit) to direct to. Once the route is put into FF the only way I know to change the magenta route would be to reprogram the trip. Maybe one can pull the magenta line over to where the aircraft symbol is, but I haven't tried it yet.

[DaveF]

ForeFlight on my iPad, I have not yet found a way to do change the route (if I am off a bit) to direct to.

On the map display of your route, touch the next waypoint. A box will pop up. On the left side is an orange dot with the D-arrow symbol for "go direct". Touch that and Foreflight will update your current flight plan leg to "present position direct to XXX'.

[jrenwick]

Regarding George's last post, I have been accustomed every since I got my first GPS to deviating either to avoid a cloud, some airspace or due to just not staying on course and from time-to-time hitting "direct to". Now as I am learning (hopefully) to use ForeFlight on my iPad, I have not yet found a way to do change the route (if I am off a bit) to direct to. Once the route is put into FF the only way I know to change the magenta route would be to reprogram the trip. Maybe one can pull the magenta line over to where the aircraft symbol is, but I haven't tried it yet.

From the Foreflight v6.5 pilot guide, page 73:

To create a direct-to change to your route, tap a waypoint on the route. Then tap the orange Direct To button. An alternate method is to tap the arrow icon in the navigation log, or to tap the colored oval in the NavLog Edit view and choose Direct To.

Choosing Direct To removes all waypoints in the route prior to the selected waypoint and adds a new direct-to leg from present position to the selected waypoint.

Additionally, a direct-to change can be made to utilize a waypoint not already in the route. See the “Touch Planning” section for details.

[170C]

Thank you Dave! Always good to have access to more experienced users of vrs things

[GAHorn]

What is the advantage of having an RNAV unit... if all you are going to do is program it to fly over already-established routes?

Do you mean you program a route which begins directly over the departure airport to the destination airport... and after departure... you actually turn, not directly toward the destination,... but instead actually turn back toward the pre-flight-programmed courseline (originating from the center of the airport you just flew away from) ?
' If so, then aren't you actually adding miles to your trip? (and tossing away one of the major advantages of RNAV?)

What do you do when you get to the destination? Do you actually fly directly over the center of the destination airport and then enter a full PPL-course traffic pattern?
....or do you contact ATC who re-directs you to a point somewhere away from the destination and who then sequences you into traffic? (In that case, if the destination is landing to the North... then how inefficient is it to navigate so as to arrive directly over the airport? Why not navigate to arrive 5 miles South of the airport so as to be flowed into traffic and not waste miles getting sequenced?)

"It does you no good to go fast the wrong direction">Beryl Minard

[jrenwick]

What is the advantage of having an RNAV unit... if all you are going to do is program it to fly over already-established routes?...

I don't think we're talking about any significant difference in distance flown between airports. Flying VFR at small piston-powered aircraft speeds, I'm not very far from my takeoff point when I turn to join the course, and I join at a 30 degree angle or less. At the destination I don't try to anticipate where the tower is going to send me, so I fly direct to the airport ID and call them ten miles out.

By the way, I'm assuming this whole discussion is in the context of VFR cross-country flights in light aircraft, not IFR in jets....

The easiest way to set up flight plans these days is by programming the airport identifiers of your takeoff, waypoint, and destination airports into the GPS. It will get even easier to do that in the future as more and more panel units become integrated with Foreflight, as Dynon has just announced. I don't imagine very many pilots will create or use waypoints offset from an airport in anticipation of their takeoff and arrival patterns.

[GAHorn]

Exactly... not much difference at all.... so why do it?...(fly 1 mile to the right of some pre-flight-planned course arbitrarily selected)... when compared to simply taking off and hitting "direct" does the same thing...?

Yes, VFR, while taxying out I enter the departure point and the destination and let the courseline be generated. Then after takeoff...I don't retrace my flight to intercept a course that's a half-mile away from me... I simply hit "direct" destination and go there. I'm on a random course that virtualy NO one else is on. (And that is the point of all this Off-Set routing, right?)

As for IFR, I await my clearance and then enter that into the RNAV flight plan.
Then, true to form, after takeoff...ATC clears me DIRECT to a fix on that flight plan. (I'm automatically on a random route to that first fix.)
If I then follow the ATC clearance-route... while IFR.... why exactly do I need to worry about someone running into me on that same route while I'm under ATC surveillance?... so much so that I need to off-set away from where ATC wants and expects me to be? '

Direct routing between airports is not very "random". Getting away from those points a bit and then going direct is more so. IMO

[jrenwick]

Exactly... not much difference at all.... so why do it?...(fly 1 mile to the right of some pre-flight-planned course arbitrarily selected)... when compared to simply taking off and hitting "direct" does the same thing...?

Well, yes. That's similar to what I'm saying: fly to the right of the course. But it's harder to create an arbitrary course that's different from KANE to KEAU or other A<->B designated by airport identifier, and besides, if lots of people do that, they'll create courses that cross each other. Better, I think, if everybody uses the same course, and navigates to the right of it.

[GAHorn]

Crossing courses are better than closely-parallel courses. You have much more opportunity to see-and-avoid because of the apparent difference in motion.

[bagarre]

I actually do over fly the airport to get on course. It's how I was taught to set your time and compass.

On takeoff, keep climbing as you turn crosswind and upwind until you're 500 or so over the pattern. Then over fly the field to get on course and set your stopwatch. That way you start out with exactly what you penciled on the map.

I don't really bother with that now that I use GPS. In fact, I wander all over the place and just try to keep the pink line on the screen

[GAHorn]

What you describe David, is how we were all taught in primary, for the purpose of dead reckoning mostly.
Why would anyone time each leg these days with the GPS giving exact predictions and elapsed-time being constantly monitored by the same device? It's another case of the micrometer, grease-pencil, and hatchet.
The most valuable clock in my cockpit is the tach-hourmeter. It tells me when I last refueled and therefore when I'm nearing empty, and it tells me when to change the oil. I keep a log in my glovebox when I refuel and how many gallons it took to fill up, which helps me keep an eye on average hourly fuel burn (which in my airplane with my flying habits equals 7.8 gph regularly, so I flight-plan 8 gph and always plan to land for fuel between 3 and 3.5 hrs.

Back to the ADS-B... what I'd prefer to see would be FAA change the rule and allow flight at/below 12,500 and outside/below Class B and C to do without ADS-B. There should be an incentive grant program for private aircraft below a certain value or weight to acquire a system, and for developers to create an inexpensive portable system. After-all, the purpose is to improve the federal airways ATC system and we're key to that goal.

[Bruce Fenstermacher]

I'd prefer they eliminate the rule altogether. Lets start from that point.

[bagarre]

I'd prefer they eliminate the rule altogether. Lets start from that point.

I think we do need to accomplish the goals that ADS-B is trying to solve but not the way they are solving it.

For IFR, it makes good sense but I'm not IFR.


Further, coming from the Information Security industry, ADS-B is a catastrophe waiting to happen.