ETE and ETA

[James Roberts]

It appears that the ETE and ETA data fields are based on airspeed toward the field. This is correct however one can only see the ETE or ETA to the selected nav point when pointing directly at it. Recommend the ETE and ETA is computed using the current ground speed no matter if flying toward the nav point or not. This calculation will have some small errors while not pointed at the nav point (ie not accounting for time to turn or wind effects on ground speed when heading changes) but it will allow the ability to see a close approximation of ETE and ETA when pointed at some other direction other then directly to the field.  See screen shots below. As the aircraft turns from 90 degrees off to NBG, the ETE changes from 02:39 to 00:24 to 00:16. Also any time the aircraft is greater than 90 degrees off, the ETE/ETA is blanked. This is correct however it would be nice to see and approximate ETE/ETA if pointed away from the nav point also.

Thank you.

[Zubair Khan]

Ron to comment more as he implemented the geometry to calculate the ETA/ETE. It was previously based on horizontal distance / ground speed (GPS gives ground speed), which Ron made better with some geometry that considers direction / track.

Thanks

On Wed, Jul 9, 2014 at 8:45 AM, James Roberts <jwr...@gmail.com> wrote:

It appears that the ETE and ETA data fields are based on airspeed toward the field. This is correct however one can only see the ETE or ETA to the selected nav point when pointing directly at it. Recommend the ETE and ETA is computed using the current ground speed no matter if flying toward the nav point or not. This calculation will have some small errors while not pointed at the nav point (ie not accounting for time to turn or wind effects on ground speed when heading changes) but it will allow the ability to see a close approximation of ETE and ETA when pointed at some other direction other then directly to the field.  See screen shots below. As the aircraft turns from 90 degrees off to NBG, the ETE changes from 02:39 to 00:24 to 00:16. Also any time the aircraft is greater than 90 degrees off, the ETE/ETA is blanked. This is correct however it would be nice to see and approximate ETE/ETA if pointed away from the nav point also.

Thank you.

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Zubair Khan
apps4av.com
zk4u.blogspot.com
Sudbury, MA 01776

[James Roberts]

I agree that the ETE/ETA works. The problem is that the current mechanization is impractical. You have to physically turn the aircraft and point it toward the selected airfield in order to see the ETE/ETA. A better mechanization would be to use the current ground speed and horizontal distant to the selected airfield and give an ETE/ETA using those parameters. 

[IFLY152II]

On Friday, July 11, 2014 6:50:29 PM UTC-5, James Roberts wrote:

The problem is that the current mechanization is impractical. You have to physically turn the aircraft and point it toward the selected airfield in order to see the ETE/ETA. A better mechanization would be to use the current ground speed and horizontal distant to the selected airfield and give an ETE/ETA using those parameters. 

 I don't understand your request. First of all, it doesn't matter where you're pointing the aircraft (due to wind correction), it's your ground track that matters when calculating ETE/ETA. If your ground track doesn't point toward the destination (or close proximation), ETE/ETA is moot because you'll never get there. Let's say the track to your destination is 360. If your ground track is 270, you'll never get there, no matter what your ground speed and distance to the destination are.

[fly...@yahoo.com]

Hi.
I think that what James says is that there ares situations when you are pointing 180, more than 90, away from your Destination and may still want, need, to know what your time to Destination is, doing Pattern work, Missed appch, Vectored, Holds, etc.
Either way it may be better to Have it than Not to have it, unless it takes a lot more processing power, which should not if the simpler algorithm is used, Time, Speed, Distance and ignore the bearing, unless we used that result for something else?
This app is morphing into something quite different than what was originally intended for? I only hope we have sufficient processing power to handle it.   TV

[Zubair Khan]

Hi Guys
I think both sides have weight. I will add an option to interchange the eta estimation algorithm with straight line eta. Its not more processing power.
Zubair

[James Roberts]

The idea is that one is conducting maneuvers at a location away from an airport. If one had to be back at the airport at a certain time, it would be nice to know the ETA to that airport regardless of the aircraft's current ground track. Additionally if the ETE to the airport is displayed regardless of the aircraft's current ground track, one can apply the aircraft's fuel burn and know approximately how much fuel it will take to get there.

Since we are just getting estimates, using current aircraft ground speed and distance to the airport to figure out the ETE (and ETA) is close enough. When one turns the aircraft toward the destination airport to go there, this number will become a better estimate. 

Reference the attachment. The display shows that the ETE to NBG is 2:39 but I am pretty sure that is an inaccurate number. The aircraft will never get to NBG on the current track. Now if we used the current groundspeed and distance to NBG to figure out the ETE/ETA, that number would be a better estimate.

Thank you for a great program!

James

[John Wiley]

> ETE (and ETA)

Maybe just an option to toggle between the present guesstimate on
current route, and Direct? Maybe also an option so that tablet users
could have 2-line boxes with smaller text? For example:
ETE Next
0:31
ETE Dir
0:12

[Zubair Khan]

Already added option to toggle between direct route time and route via relative bearing time. Will be in next release tonight.
Z

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