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Back to the Stone Ages - Almost

JoeLofton

Well Known Member
Sunday, on a VFR flight to Las Cruces, I lost the GPS signal to my Trutrak ADI about 80 miles east of El Paso. Then lost the GPS signal to the 796 about 10 miles east, which also took out the ADS-B traffic. Suddenly I was faced with navigating through the interesting mix of Class C airspace, restricted areas, mountains and rain showers armed only with a finger on the (electronic) sectional and landmarks on the ground. I pulled out the iPad for the larger SkyViewPro sectional and was surprised that the iPad still had a good GPS signal. A close call - I almost had to do it the old-fashioned way.

In retrospect, I'm surprised at how comfortable I've become with the little airplane symbol on the magenta line. It took a few minutes to mentally switch over to old-fashioned pilotage and I was relieved to see the iPad working.

Don't know what caused the GPS signal loss. The 796 reacquired about 10 miles out from Las Cruces. I think I'll practice my pilotage more in the future.

Joe Lofton
RV-3
 
Thanks - I'll send a note if I can figure out where to send it. And pay better attention to Navigation NOTAMs in the future.
 
I've been brushing up on my XC's and I'm mostly using the Lindbergh Technique. Took no time at all to get back into the VOR swing of things and GPS makes it so that you have to be really working hard to get lost.

But I know those electrons can stop flowing and/or GPS signals weaken and so I always fly with paper. And I'm maintaining the skills to use it.
 
What I am confused about is - if GPS was not available, how did the iPad have maps? I would guess the sat view factor for the iPad is not as good as a mounted antenna.
 
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Navigation

The Lindbergh way was a compass heading, using a compass that was considerably better then most magnetic compasses used today. Any charts that he may have had available were very basic, probably ships charts.
For may years I have amused myself on a semi regular basis with dead reckoning. Draw a line on the chart, after takeoff, turn off the nav radios and fly a compass heading for 1 hour or more, 500 agl. If one makes a reasonable wind correction you can come amazingly close.
Years ago I had some regular passengers on a pilot services deal. I would do a one hour run across NE PA without looking at a chart. One of the passengers asked the aircraft owner how I found my way. The aircraft owner said he used the navigation radios. The passenger said-no he turns all the radios off. The owner got a big laugh out of that and told me about it later.
 
Nav

In the Lindbergh era there were not even any aeronautical charts. The first Sectional chart was published in 1930, full coverage of the "lower 48" was not available until 1937.
Experiments with low frequency navigation began in the late 20's. Low frequency ranges became available in the early 30's and were the only means of navigation until the late 40's when VOR's were first installed. There was celestial navigation but this depended on being above the clouds, which often did not occur on the N Atlantic.
So virtually all ocean flying in the WWII era was a combination of dead reckoning and low frequency beacons and ranges.
The Earnest Gann books are a fascinating read on the subject.
 
My Trutrak ADI has a hockey puck antenna mounted under the canopy behind the pilot. It was the first to go. The 796, mounted just above the stick, was using the internal antenna, which has always been rock solid. It was the next to go. The iPad, with internal antenna, was stuffed deep down in the cockpit beside me until I turned it on. It never lost position. Go figure.
 
We be jammin!

I've seen a NOTAM out the last few days indicating that they (military) are jamming gps signals in the White Sands area NE of LRU. I talked to many pilots that reported losing their GPS signal in that area. You can't always trust that the signal will be there.
 
GPS NOTAM

10/105 - NAV (WSMR GPS 14-09) GPS (INCLUDING WAAS, GBAS, AND
ADS-B) MAY NOT BE AVAILABLE WITHIN A 544NM RADIUS CENTERED AT
324440N1060817W (ELP357056) FL400-UNL DECREASING IN AREA WITH A
DECREASE IN ALTITUDE DEFINED AS:
513NM RADIUS AT FL250,
403NM RADIUS AT 10000FT,
381NM RADIUS AT 4000FT AGL,
373NM RADIUS AT 50FT AGL. 25 OCT 03:00 2014 UNTIL 25 OCT 09:00 2014. CREATED:
21 OCT 00:05 2014
 
The Lindbergh way was a compass heading, using a compass that was considerably better then most magnetic compasses used today. Any charts that he may have had available were very basic, probably ships charts.



Well I will admit using the DG and not the wet compass. And yes we have great aeronautical charts - better than in Lindy's day. But keeping pilotage skills up takes some practice, but I think that, for me, it's worth it.
 
alternatives?

Is anyone developing a MEMS based experimental inertial navigation device to augment this kind of situation of all the eggs in one basket?

Maybe an iPhone based app that can augment system GPS and take over when GPS goes off line?
 
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Is anyone developing a MEMS based experimental inertial navigation device to augment this kind of situation of all the eggs in one basket?

Maybe an iPhone based app that can augment system GPS and take over when GPS goes off line?

GRT Horizon already does this - goes into inertial navigation mode for its moving map following loss of gps - but also displays a warning that accuracy is degraded.
 
Don't the later iDevices also receive the Russian GLONASS signal? The European Space Agency is or will be launching their own nav sats, I just read where the Indians have plans for same, and I'm sure the Chinese will have their own as well. The more the better, as long as we civilians can use them. They've become too important to be shut down at will by the US military.
 
Don't the later iDevices also receive the Russian GLONASS signal? The European Space Agency is or will be launching their own nav sats, I just read where the Indians have plans for same, and I'm sure the Chinese will have their own as well. The more the better, as long as we civilians can use them. They've become too important to be shut down at will by the US military.

You can get a Garmin GLO Portable GPS and GLONASS Receiver with Vehicle Power Cable for 100 bucks form Amazon.

Not sure I want to place my navigational safety in the hands of the Russkies ;)
 
Say what you will about GLONASS

... but Vlad found his way here okay. Now it seems we're stuck with him.
 
On my recent trip east (and back) I used PAPER sectionals (ask your grandparents) even though I had a portable GPS in the panel. I don't have a VOR.

It was great fun to use them again and I could also write all over them with times etc, matching stuff on the ground to stuff on the paper.

Paper never blinks off. :D
 
Is anyone developing a MEMS based experimental inertial navigation device to augment this kind of situation of all the eggs in one basket?

Maybe an iPhone based app that can augment system GPS and take over when GPS goes off line?

This really isn't possible with the errors in MEMS sensors. They drift multiple degrees per minute. There's a reason strap down INS units use individual sensors that are $20K plus. They also generally require 10+ minutes of warm up time on the ground before you can move the vehicle at all. They can pick up the heading of the vehicle by detecting the quarter degree per minute that the earth rotates!

Then in a portable device, you have the problem to deal with which is that it isn't strapped to the vehicle. It has no idea if the rotation it sees is due to the plane moving or just because you picked it up and moved it.

Also, just for accuracy, the GRT units switch to dead reckoning, which is very different than a full INS mode. Dead reckoning cannot deal with changing airspeed or winds. From the manual:

dead-reckoning using the AHRS heading, true airspeed, last known winds and time. This data is used to estimate changes in position, which are applied to the last known GPS position to give an approximate navigation solution.
The accuracy of the dead-reckoning function will degrade with time depending on the accuracy of this data and changes in the winds.
 
... I pulled out the iPad for the larger SkyViewPro sectional and was surprised that the iPad still had a good GPS signal. ...

Was it a GPS signal or perhaps the iPad using cell towers to compensate? The SIM9xxx chips I have played with will fall back to cell tower "triangulation" on loss of GPS. Well... with some code tweaking.

I wonder if these GPS outages are tests to deal with the recent uprising of drones and the associated paranoia in today's climate. Quick... somebody call Bob Lazar. LOL!
 
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