Navy Knocking out GPS in June over Mohave

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mekender
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Re: Navy Knocking out GPS in June over Mohave

Post by mekender »

tfbncc wrote:
I have no experience in aviation, but I have been told that aviators also learned to navigate prior to GPS.
Prior to GPS, most navaids were nothing more than fancy radio direction finders. It can get pretty interesting when your crew is flying a P-3C from Keflavik, Iceland up to Thule, Greenland circa 1978. There aren't a lot of radio stations or airfields that you can tune in. And Loran is a bit sketchy (anyone remember Loran? Anyone? Beuhler? Beuhler?) The last good position check was when the plane made landfall on the Southern Greenland coast. Halfway across the center of Greenland, the navigator comes up on the intercom: "I think I made a mistake in my math. We may be a couple hundred miles off course and I'm not quite sure where we are..." Long, pregnant silence.

We made it to Thule without burning too much extra fuel. But the navigator didn't get any dessert that night.
I believe that some of the higher altitude planes carried sextants for most of the last hundred years didnt they?
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JustinR
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Re: Navy Knocking out GPS in June over Mohave

Post by JustinR »

Private pilot training includes pilotage (navigating by landmarks on Visual Flight Rules=VFR charts as Termite said), dead reckoning (speed plus time equals distance adjusted for winds aloft), and basic radio navigational aid useage. Instrument training includes advanced radio navaid useage, including instrument approaches. Back when aviation got started, all they had were visual lighted airway beacons that were put on airmail routes. Then, they got AN radio beacons that had a morse code of A or N (or both) depending on what quadrant you were in. Then, Non Directional Beacons (NDB's) were established, which emitted AM frequencies and could be tracked by a bearing pointer in the cockpit. Then, VHF Omnidirectional Ranges (VOR's) allowed determination of exact radial and course offset from the range, and also usually had Distance Measuring Equiptment (DME) co-located. Localizer/glideslopes (Instrument Landing System or ILS) function on basically the same principal. LORAN was established for long distance nav outside the range VOR's could be picked up offshore. And then GPS came along, and eventually WAAS and LAAS augmentation.

When I was in instrument training, I learned to do approaches using NDB's, VOR's, ILS's, and GPS. LORAN wasn't still in operation, although one of our airplanes had a receiver. We certainly learned to use the GPS to its full abilities, but our instructors were careful to make sure we were not reliant on it for situational awareness.

NDB's are being phased out (finally) by the FAA, but NDB equipment can still be used to home in on AM radio stations, and the major stations with serious broadcast power like WBAP in DFW with 50 kW can be picked up a few states away at night on occasion. Basic RNAV systems allow position computing based on VOR/DME location, and VOR/DME is still the "primary" navigational method. Modern RNAV systems usually rely on DME/DME position computation, my aircraft is capable of receiving something like 20+ DME stations at the same time, with GPS used to augment and backup the computation, and VOR's if necessary.

Celestial nav of course has been around since forever, and was used by the airlines as late as the 70's. Older 747's had sextant ports in the cockpit, although they were most often used by smokers to suck the smoke out of the cockpit when they needed a nicotine break on a long flight by wedging it slightly open with a pencil. One of my instructors was a nav on the KC-135, and used celestial nav in the USAF during the 80's.

Inertial reference systems have also been in use for quite some time. The early IRS/IRU's were mechanical sensors, and had quite a bit of drift. They were usually calibrated to a known position by the navigator at the end of the runway before takeoff. Modern IRU's/combined AHRS use laser ring gyros and are pretty darn accurate, and can determine latitude location based on the spin rate of their location on earth while initializing.

What's neat is that aircraft like the 737 have the ability to display the computed position of all instruments on the moving map display. One time while I was jumpseating, they zoomed in and turned them on. The VOR/DME jumped around a bit, the IRU's had drifted off a bit toward the left wing, and the GPS position was dead center on the antenna above the cockpit (obviously the system prioritized GPS in the computation for navigation.)
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JustinR
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Re: Navy Knocking out GPS in June over Mohave

Post by JustinR »

mekender wrote: I believe that some of the higher altitude planes carried sextants for most of the last hundred years didnt they?
Long distance overwater aircraft, not dependent on altitude.

Oh, as an interesting aside, PanAm airlines and their flying boat routes were probably the first to establish using radio navigational aids to help their ships find the station, and were the first radio transmitters on many of the islands of the Pacific.
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JustinR
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Re: Navy Knocking out GPS in June over Mohave

Post by JustinR »

Oh, and new aircraft usually rely on GPS augmented by WAAS/LAAS where available, but can still use VOR/DME. I'm not sure why the Embraer Phenom is singled out, it may have something to do with the altitude ranges this interference is occurring, and the way that particular plane's navigational system operates.
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Netpackrat
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Re: Navy Knocking out GPS in June over Mohave

Post by Netpackrat »

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Termite
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Re: Navy Knocking out GPS in June over Mohave

Post by Termite »

JustinR wrote: Modern RNAV systems usually rely on DME/DME position computation, my aircraft is capable of receiving something like 20+ DME stations at the same time, with GPS used to augment and backup the computation, and VOR's if necessary.
When I left the LA-ARNG back in the early '90s, we were not using RNAV. And GPS was just beginning to "take off".

However, a couple of weeks ago I was a "safety pilot" for a guy who is getting his instrument rating. For those not in the know, during instrument hood practise in VFR conditions, there is a requirement for another rated pilot to not be under the hood, and keep his eyes outside looking for other traffic. That is what I was doing.
The other pilot shot the RNAV (GPS) RWY 270 approach into Esler(KESF). It was the first time I had ever participated in an RNAV approach. Afterwards, we were discussing it, and I told him it was very similiar to fully synthetic approaches(non-certified) that are possible using a Stratus 2 GPS, blue toothed to a Samsung Tab 4 running the NAVIATOR Pro App.

Also, I and a couple of other pilots flying "the lite stuff" have "played" with setting up our own approaches using either a Garmin 196 or even a Garmin GPS V. Both are WAAS enabled, and accurate to within 20 ft. By establishing at least 5 waypoints, with #1 being a waypoint 1/3 the way down the runway, it is quite possible to set up an un-certified GPS instrument approach as a GPS route, complete with MSAs at each point.
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MiddleAgedKen
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Re: Navy Knocking out GPS in June over Mohave

Post by MiddleAgedKen »

(anyone remember Loran? Anyone? Beuhler? Beuhler?)
I do, a little. Back in 'ninety and three :), I navigated my folks' Matthews sedan cruiser from St. Joseph, MI to Fairport Harbor, OH. Learned to read radar (a Seascan MKII) and do some dead reckoning. By the early '90s the Coast Guard was shutting down the Loran stations during the week, so fixes were wonky. Actually, they were still good for longitude, but latitude was...interesting. Fortunately, there's only so lost you can get on the Great Lakes.

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PawPaw
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Re: Navy Knocking out GPS in June over Mohave

Post by PawPaw »

I remember one night when I was in the walking Army. I had a team of 12, and we were reconnoitering positions in the woods around Fort Knox, KY. Moonless, high cloud cover, in deciduous forest,It was dark as my first wife's heart and I got lost. By-God Lost. However, I had two good NCO's with me... who were also lost.

I knew though, that my good buddy and drinking compadre, Doug, had a 4.2" mortar section with pre-plotted fires in the impact area. So, we established a hasty perimeter, while me, my RTO, and my NCOs got under a poncho, broke out the red light and the map. I got on the horn to Doug. "Can you fire one round on target Alpha?" I told my NCO's to point when they heard the mortars thump. They did. Then Doug called the Splash, and we got a good bearing on the impact. So, I called Doug back. "Give me one round on target Bravo". Same drill, shoot a back-azimuth on the mortar thump and the rounds impact. The lines on the map converged, and there we were. Off course, but no longer lost.

My NCOs thought that was cool. We completed the mission and, we got back to the TOC in time for breakfast.
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randy
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Re: Navy Knocking out GPS in June over Mohave

Post by randy »

tfbncc wrote: (anyone remember Loran? Anyone? Beuhler? Beuhler?)
We were introduced to it in basic AF NAV (AKA Undergraduate Navigator Training, UNT), but actual training was for the advanced nav courses for the heavies.
mekender wrote:I believe that some of the higher altitude planes carried sextants for most of the last hundred years didnt they?
During the 80's celestial was part of UNT no matter what aircraft your were slated for. The reason I didn't graduate is that apparently basic arithmetic skills are necessary when trying to resolve celestial sightings to a map. Who knew? :? (I did pass all the academics, just could not make it through a celestial check flight.).

Every AF tanker and transport at the time had a sextant port. We had Marine enlisted at the school that learned Cel for use on their KC-130's and the Navy NFOs slated for P3s also trained there (including Cel), but could not speak to sextant ports on those birds..

When I spent some time on KC-135's the Boom operator actually operated the sextant, feeding readings to the Nav.

We were also familiarized with AstroTrackers that did the sightings automatically based on inputs entered on a panel at the Nav position (used on B-52's and IIRC FB-111's)
JustinR wrote:What's neat is that aircraft like the 737
Heh. The trainer we flew at nav school was the T-43, a modified 737. It had at least 4 sextant ports
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NVGdude
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Re: Navy Knocking out GPS in June over Mohave

Post by NVGdude »

randy wrote:
When I spent some time on KC-135's the Boom operator actually operated the sextant, feeding readings to the Nav.
We replaced the nav on the KC-135 with the last AMP. It's now the boomers job (since he's enlisted) to use the sextant if necessary.
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