Getting around using old INS Systems

[OBK!]

Just studying my ATPLs and doing the stuff about the old INS systems, where you have to input the coordinates of the waypoints of your flightplan into the system. Concorde uses this system if I am correct, and 737-200, 727's etc.

My question is, what happens when it comes to receiving an unplanned "Direct to" during your STAR, or maybe a just out of coinsidnce the ATC says "Direct BLUFA"....halfway through your route,....what happens? Does the FO have to input the cordinates, then insert all the route after BLUFA again?

Also, does the FO programme all the SID/STAR waypoints in the INS or does he just plug in the radials from the given VORs etc.

Thanks in advance.

[WOK]

I've used the carousel type INS on 747s and Conc. You need to understand that it was fitted to deal with "Nav" sectors - ie tracks without ground aids, and that is just how it is used.

So, you don't use INS to fly a SID - this type of system is no use for that - you fly off VOR and NDB. (On the Conc you do this raw data - the flight director is not available for take off.)

Before start you will have loaded waypoints useful to you; typically this would include, say, Woodley NDB out of LHR but in reality you would be using the ADF to find Woodley (Assuming you weren't on radar vectors). The first time you use the INS to navigate is usually when cleared to the accel point in the Bristol Channel. If you were sent to a point such as BLUFA it is easier to find it using VOR/DME than to find the Lat/Long, load and check 3 INSs.

En-route across the Atlantic you are using the INS for exactly what it was designed and it works well. You need to ensure you don't run out of waypoints, given the maximum of nine.

At the far end the situation is the same as for departure - in the terminal area you will be nav'ing off the needles. It's very IR type stuff - when JFK APP clear you direct to a fix on the approach you find it by flying a track based on the QDM to JFK VOR using the one-in-sixty rule to determine a heading based on dist from JFK and distance of the fix from JFK.

30miles from JFK at 4000' /350 kts is no time to have your head in the cockpit playing with INS'!

If you are used to modern FMS based cockpits this will sound like terribly hard work, but it's just FLYING! And it's one of the joys of flying the Conc - so long as you enjoy aviating.

As for programming - it's not done by the "FO": Before departure the INSs are loaded by the Handling pilot (Capt or FO) and once airborne the loading is done by the non-handler, for obvious reasons.

[oxford blue]

As WOK says, you are unlikely to be taking steers from the INS during a STAR. But you could be told to break out of a STAR to proceed direct to a waypoint already entered as part of the route (like BLUFA).

In this case (say BLUFA is waypoint 3 and you are not yet at WP2), you press TRACK CHANGE, 0, 3, ENTER. Your present position (wherever you are) becomes WP 0 and you get a direct steer to WP3. Waypoint 0 can only be used for present position. You cannot manually enter a lat and long into it.

If the place you are given a direct clearance to is not already one of your waypoints, then enter it as WP9 (or any other store you are not using at the time). Now press TRACK CHANGE, 0, 9, ENTER and you will be steered to it. When you get to it, you don't have to re-enter the rest of the route. Say the next WP is 4. When you get to your direct cleared point and want to proceed to WP 4, press TRACK CHANGE, 9, 4, ENTER. You are then back onto the original flight path, with no changes necessary.

[OBK!]

Many thanks! I can now fly a Concorde, easy as that ;) (Yeh right!)

[Georgeablelovehowindia]

With the Litton 72 system on the DC-10, you would agree which waypoints you were initially going to enter and allocate them numbers 1 to 9 sequentially, on the plog. Waypoint 1 would be the co-ordinates of the departure airfield. One pilot would read out the co-ordinates of each waypoint, off the plog, and the other pilot would insert them, monitored by the flight engineer. As each waypoint was inserted, all three INSs would be examined to confirm that they were displaying the correct co-ordinates before proceeding to insert the next one. (In my airline, the procedure was then to circle the appropriate number on the plog to confirm this.) Having inserted all nine waypoints, you then went back to the beginning and checked the True tracks and distances between the waypoints, inserting a tick on the plog next to the appropriate circle to confirm. All very tedious, but necessary.

The departure was always flown in conventional VOR/ADF type nav., with the Flight Guidance System in Heading Select. One very good reason for not putting it into INS, was that in INS mode, the CDIs referenced to True and the heading bugs parked in the six o'clock position. Not a good situation if you were given a radar heading! However, once cleared direct somewhere, you put the FGS into INS, confirmed the number of the waypoint cleared to e.g: "MASIT is Number 8, confirm?" "Check" from the other pilot. You then pressed Track Change 0 (Present Position) to 8, pause, "Check" from the other pilot, Enter. A further careful watch was made to ensure that the aircraft took up a sensible heading.

This action would render waypoints 1 to 7 obsolete. However busy you were, you would have to find time to insert and cross-check at least the new waypoint 1 before overflying waypoint 9 and in time the new 2 through to 7. (You might be busy, as the non-handling pilot, re-writing the tracks and distances on the plog because the oceanic track clearance was not the one planned and filed for.) Always good for a laugh that one... :eek:

The whole laborious process was repeated again and again and again as the waypoints became obsolete in turn, all the way to destination. Reversion to conventional nav. and Heading Select was at some point on the STAR, or even earlier, if the INS position had wandered off too much. (This position was the "Triple Mix" position of all three INSs, assuming you remembered to do it.)

The Litton 92, which was available as a retrofit, had a database and made life considerably easier.

(Thanks oxford blue, that'll teach me not to take a lunch break in between starting something and finishing it!)