Modern cockpits are all "glass" meaning they use display screens for instrumentation. Each pilot has a Nav Display, which provides a map, or map information in various forms. The basic course to which the pilot has assigned the airplane, the route, is depicted by a magenta line, and for the course of the flight, the aircraft follows the magenta line. Points in space, geographical coordinates, are called "waypoints," some of which are defined with five letter names, and many of which are simply lattitude/longitude coordinates.

If a crewmember puts in an incorrect coordinate, the magenta line simply takes the aircraft over that cordinate; being on the correct course, and being on the wrong course, looks the same, because the pilot has defined the course incorrectly. The display is identical.

For oceanic flights, positions are given in the pacific as both lat/long, and on airway routings, as named fixes that are alphabetical (DENNS, DRAYK, DUSAC, DIALO, etc), and in the Atlantic are defined by positions located every ten degrees of longitude, and every degree of latitude. A more recent development is half-degree tracks, putting aircraft closer together, and creating greater room for error, too.

The traditional oceanic waypoint convention, which predates the 1980 747 of this thread, uses a five letter number to denote position, and the number codes the location by hemisphere in a "naming convention" known as ARINC424. A flight going to 54 degrees north, 30 degrees west, would enter 5430N, and a flight going to 54 north 160 west would enter 54N60. On oceanic legs, the crew is required to verify the current and next waypoint, looking closely at the latitude/longitude, and many operators still use paper charts on which the crew plots a position ten minutes after crossing the fix.

The ten minute plot gives enough time for the aircraft to be off course enough to see on the plotting chart, such that a position check at that time will determine the airplane is on course. The cockpit display will show the airplane on course, on the magenta line, but the plotting chart will catch the error. In older times, plots were taken by a variety of means, including celestial (star plots). Today, the crew checks the output from all the navigation systems and the "triple mix" position where certain ones are integrated to form an average.

The big difference between nav today, and nav back then, other than nav today tends to be extremely accurate with a lot more information presented, is that position plots today use the same navigation computers and displays to check themselves and to determine position, whereas in times past, the crew was actually making an independent determination of position...something lost today.

There are those who do little more than follow the magenta line, and are sometimes referred to as "children of the magenta line." Those who were brought up in a world that required the pilot do a little more than blindly follow the little purple line, tend to view the children of the magenta line with some distain.

Here is another video that explains the 5 basic forms of navigation




Link to original video: https://www.youtube.com/watch?...&feature=emb_rel_end

They just flew south until the toilets started flushing the other way.

quote:

Originally posted by low8option:
When did commercial airlines stop using navigators as part of the crew?

Absolutely as soon as the bean counters could get away with it. It’s funny, the pilots only flew four engines jets because they didn’t have the option of eight engine jets. The bean counters only buy twin engine jets because it’s really hard to get ETOPS approval for a single engine jet.

quote:

There are those who do little more than follow the magenta line, and are sometimes referred to as "children of the magenta line." Those who were brought up in a world that required the pilot do a little more than blindly follow the little purple line, tend to view the children of the magenta line with some distain.

This is frightening.

I learned how to navigate with map and compass in Boy Scouts (learned that contour lines are pretty important when hiking). I furthered that knowledge with navigation for sailing, albeit I never learned celestial navigation only dead reckoning. I use a GPS for land and water travel but consider it advice, nothing overrides direct observation, dead reckoning and common sense. I am always amazed to read stories about folks that drove off the end of the road because "the GPS said so".

I hoped pilots train, and would adhere to, a higher standard since the consequences of system failure are far greater. Then again I think about the world today and realize I expect too much.

I went to Aerial Navigator school at Mather Air Force base. We were taught celestial navigation along with LORAN, OMEGA, pressure pattern navigation, radar and others.

As others have said time, speed and heading are used to estimate your position at a certain time. At that time you get a fix and find you location. Adjust and continue in 30 minute increments.

When it gets a little tricky is when you have a cloud layer overhead at night and cannot get a fix so you have to dead reckon longer. Remember why its called dead reckoning......if you reckon wrong you are dead.

The big difference between flying and driving or hiking is that there isn't any direct observation in an oceanic flight, or a flight conducted on instruments.

Dead reckoning is great, and effective when precision isn't required, but the north atlantic is the most congested airspace on the planet, and it demands precision. Flights are done by half a degree, and offsets by a tenth of a mile. The tolerances are tight enough that if one has an equipment malfunction and cannot operate to those required navigational performance levels, it must be reported, and one must leave the airspace. While much of the world's oceanic airspace allows up to RNP10 (within 10 miles of course, 95% of the time), the NAT tracks are RNP 4, and by the time one arrives at a destination, the tolerance is RNP .3. Some of those may sound like a lot, but remember that it's done at four fifths the speed of sound, for up to seven thousand miles, often with little or no other reference than the cockpit instrumentation.

The flip side of that is that while hiking up a hill, you have all the time in the world to consult a contour chart, compare it to what you see, take multiple cmopass shots, and correct, and you've got a pair of sneakers, a tin compass, and two eyes. Conversely, in the cockpit, there are a thousand instruments, lights, switches, bells, clackers, screens, warnings. One combination of all that, and the tens of thousands of choices in a single flight plan page on a flight management system, will produce the desired course...and once chosen, it all looks...the same.

Good airmanship is using the procedures and techniques that allow one to be sure, but there are numerous glaring examples over the years of crews that ran out of fuel thanks to metric conversions, landed at the wrong runway, programmed the wrong fix, or like the AA967 B757 flying to Cali, Colombia, that flew into a mountain when selecting a beacon fix because of a subtle misunderstanding in the clearance. There's a whole lot to go wrong, if one allows, and the lions share of cockpit duties is all about preventing such from happening.

An example of a crew struggling to fly a perfectly good airplane:

https://www.flightglobal.com/s...X1fl3-nJrvk.facebook

The only problem was that the autopilots failed. When pilots can't do the most basic task of flying the airplane, there's a huge problem. This is more prevalent in foreign operations than in the US, but we see competency issues that stem from pilots who don't seem to be able to operate without a crutch, in all areas. The Atlas 767 crash in Houston was such an example.

I just finished a simulator training session that culminated with a thrust reverser deployment in flight. I found that the autopilot couldn't keep up, so the solution was to hand fly the airplane. It shouldn't be that big a deal, and wasn't, but are those who engage the autoplot at 400' and disengage it on short final to land...and those are the ones that should be watched when the brown hits the fan blades.

Before I-80 was built,
There was 69 miles of Hgwy. 6

Between Iowa City and Davenport, Ia

And , there was a big barn with Iowa City and an arrow on the roof. Pointing west.
Then
There was another building down the road.

With 36 inch tall letters on the roof and an arrow pointing east,
That read Davenport.

quote:

Originally posted by bendable:
Before I-80 was built,
There was 69 miles of Hgwy. 6

Ummm, you're aging yourself

This will help,
They got our section of I-80 done just in time for
Herbert Hoover's grave side services in West Branch.

A friend of mine (niece's father-in-law) responds to my query. He was a navigator on Japan Air Lines flying between the US and Tokyo on 747's:

quote:

The 747 came out before GPS was available to non military users. GPS was just in its infancy then and controlled by the DOD. During that period the planes used inertial navigation systems. The same type system submarines used and still use. The sensor is a set of sensitive gyros mounted in all 3 planes which house accelerometers. The accelerometers sense movement in 3 directions. Up/down, left/right & fore/aft. This info is sent to a computer which keeps track of the aircraft's position. Before takeoff the pilots have to tell the computer where it is and the computer then does the rest. A good system had an error rate of a mile an hour. After an 8 hour flight the system might be off by 8 to 10 miles - more than accurate enough for a plane flying 8 miles a minute. For polar flights JAL used a 3 INS package while for normal latitude (below 60 deg. Lat.) flights only two systems were required to be on board. The INS system is what put flight navigators out of business.

I spoke with a submarine navigator years ago. He told me the sub’s INS was so accurate it sensed movement when the sub was tied up at dockside and a passing ship’s wave caused the sub’s lines to stretch! Pretty neat stuff.

Nowadays with GPS being so accurate aircraft vertical separation enroute has been reduced to 1000 ft from 2000.

quote:

Originally posted by sjtill:
A friend of mine (niece's father-in-law) responds to my query. He was a navigator on Japan Air Lines flying between the US and Tokyo on 747's:

quote:

The 747 came out before GPS was available to non military users. GPS was just in its infancy then and controlled by the DOD. During that period the planes used inertial navigation systems. The same type system submarines used and still use. The sensor is a set of sensitive gyros mounted in all 3 planes which house accelerometers. The accelerometers sense movement in 3 directions. Up/down, left/right & fore/aft. This info is sent to a computer which keeps track of the aircraft's position. Before takeoff the pilots have to tell the computer where it is and the computer then does the rest. A good system had an error rate of a mile an hour. After an 8 hour flight the system might be off by 8 to 10 miles - more than accurate enough for a plane flying 8 miles a minute. For polar flights JAL used a 3 INS package while for normal latitude (below 60 deg. Lat.) flights only two systems were required to be on board. The INS system is what put flight navigators out of business.

I spoke with a submarine navigator years ago. He told me the sub’s INS was so accurate it sensed movement when the sub was tied up at dockside and a passing ship’s wave caused the sub’s lines to stretch! Pretty neat stuff.

Nowadays with GPS being so accurate aircraft vertical separation enroute has been reduced to 1000 ft from 2000.

Vertical separation has nothing to do with GPS, and GPS doesn't determine altitude in aircraft. Below a certain altitude, which varies by country, it's set by the local barometric pressure in inches of mercury, and then the altimeter itself determines altitude above sea level based on input from an air data computer...but not GPS. Above a certain altitude, or transition altitude, all aircraft reference the same barometric standard, which is 29.92 inches of mercury, or 1013 milibars.

INS, which became IRS, is the standard today, and determines not only position, but also sends information to numerous other systems in the aircraft, from autobrakes to aircraft instrumentation, radar stabilization, etc. Light airplanes will recognize the idea of gyroscopes inside their instruments; these are gyros that are used for numerous functions; same gyros, but multiple functions, and they're not located in the instruments. They were originally an actual gyro, and later a laser ring. Some equipment uses solid state.

Eight miles of drift is far outside the oceanic tolerances in the North Atlantic, today. INS drift will put an aircraft outside the allowable limits for North Atlantic airspace, which is RNP-4, or required navigational performance 4 nautical miles, meaning that at it's extreme, the aircraft must be within 4 nautical miles of its reported position, 95% of the time. In reality, most aircraft are capable and routinely do 0.3 tolerances, which is what is required for terminal area and instrument approach operations. This cannot be done on INS.

with INS, three INS units independently calculate position, which provides three different positions, and then an average is taken, called a "triple mix." If tolerances are exceeded individually or in the triple mix solution, then one or more gyros are excluded or in certain cases, the units operate independently, sending and displaying entirely separate information to both pilots. With this in mind, when flying a routing using only INS, as time goes on, position degrades, and the captain might be seeing left of course, while the first officer shows right of course (the third gyro, an auxilliary, or backup gyro, combines with the others for certain functions, or serves as a spare for others). This was normal. Today, not so much.

The reason that accuracy is better today is because in addition to the INS/IRS/IRU systems, there is typically double or triple GPS input, as well as ground based inputs. These continually update the system, or provide refinement. They do not, however guide the aircraft. They provide refinement into the flight manageent system, which uses them to do it's calculations via the flight management computer, or FMC.

In the case of an FMC dual failure (had one last year over the pacific), the crew won't have access to GPS. The aircraft is still receiving it, but unlike a car which has a GPS receiver with navigation based on GPS, the aircraft does not...and can't navigate by GPS if the FMC is lost. The GPS is there, but the crew can't use it. The only function available to the crew becomes manually tuned ground based navigation aids (navaids) and INS, and position degrades to the INS level.

Operators can be approved for long range navigation with just one long range nav system on board, though most use multiples. I can operate with just one under certain rules, though of course that excludes redundancy and options.

8-10 miles would be a very bad system today, and twice the maximum allowed tolerance in some airspace...and over 30 times the max tolerance in others. Completely unacceptable. That degree of inaccuracy that was accepted in 1969, however, is the reason for 1 degree track spacing in the north atlantic high altitude airspace; 60 miles between tracks. Today it's half-degree spacing with 1,000' separation, within two minutes over a fix by time, constant mach numbers assigned to each flight to establish spacing, monitoring by computer data link, ADS systems, HF radios (still), and a 10 mile inaccuracy would trigger an international investigation as a GNE, or gross navigational error.

The 747 came out in 1969. GPS began in 1973, and the full constellation wasn't available until 1993, when it was still degraded for users outside the military. Selective availability ended in 2000, meaning everyone could use it. The military still frequently degrades the signal in certain locations.

Do your Nav systems use only GPS?

Do you ever use the Russian, Chinese, or EU equivalents?
.

quote:

Originally posted by usmc-nav:
When it gets a little tricky is when you have a cloud layer overhead at night and cannot get a fix so you have to dead reckon longer. Remember why its called dead reckoning......if you reckon wrong you are dead.

Yes, except it isn’t “dead reckoning”, it is “ded reckoning”, short for “deductive reckoning”. If the pilot can maintain a constant heading and airspeed, and if the winds don’t change, you can deduce where you are based on where you were and the heading and airspeed you maintained.

Dead reckoning *is* more catchy though.

quote:

Originally posted by slosig:

Yes, except it isn’t “dead reckoning”, it is “ded reckoning”, short for “deductive reckoning”. If the pilot can maintain a constant heading and airspeed, and if the winds don’t change, you can deduce where you are based on where you were and the heading and airspeed you maintained.

Dead reckoning *is* more catchy though.

Debatable. There are several schools of thought on that, and one version traces back to the old saying that it's dead reckoning, because if you don't reckon right, your'e dead. Goes back to pre WWI.

Needle, ball and airspeed. Good basic airmanship, but still got a lot of people killed.

quote:

Originally posted by sjtill:
A friend of mine (niece's father-in-law) responds to my query. He was a navigator on Japan Air Lines flying between the US and Tokyo on 747's:

quote:

The 747 came out before GPS was available to non military users. GPS was just in its infancy then and controlled by the DOD. During that period the planes used inertial navigation systems. The same type system submarines used and still use. The sensor is a set of sensitive gyros mounted in all 3 planes which house accelerometers. The accelerometers sense movement in 3 directions. Up/down, left/right & fore/aft. This info is sent to a computer which keeps track of the aircraft's position. Before takeoff the pilots have to tell the computer where it is and the computer then does the rest. A good system had an error rate of a mile an hour. After an 8 hour flight the system might be off by 8 to 10 miles - more than accurate enough for a plane flying 8 miles a minute. For polar flights JAL used a 3 INS package while for normal latitude (below 60 deg. Lat.) flights only two systems were required to be on board. The INS system is what put flight navigators out of business.

I spoke with a submarine navigator years ago. He told me the sub’s INS was so accurate it sensed movement when the sub was tied up at dockside and a passing ship’s wave caused the sub’s lines to stretch! Pretty neat stuff.

Nowadays with GPS being so accurate aircraft vertical separation enroute has been reduced to 1000 ft from 2000.

This was very interesting! Thanks for sharing that!

Sns3guppy,
I need your phone number,
If there comes a time when I need to know where I am,
Can I call you ?

So long as you're not driving. I get lost going around the block.

In the air, there's a lot less to hit, and navigation is greatly simplified.

I just got issued a samsung phone, and can't figure it out. If you call, I may not be able to answer.

1980's to 2000's, Army Aviation Unit, MT National Guard.

We had a big map of Montana on the wall. There was a nail in the wall over our base. With a long string attached. You stretched the string to your destination, noted the compass reading and away you went.

A lot of it following roads as well or shooting for familiar landmarks.

The good old days.