AINS-70 History
Now to AINS-70:
There once was a booklet titled, "Everything you wanted to know about AINS-70, but were afraid to ask." Kinda' wish I still had a copy.
The Area Inertial Navigation System, AINS-70, was a milestone in commercial air navigation, and ahead of its time. It could fly the airplane hands-off from takeoff to touchdown. The FMS, Flight Management System, in the 767 a decade later, built on the concept of the AINS-70. In fact,the FMS copied significant parts of the AINS-70, including the CDU.
The AINS-70 was a collaboration of the KSSU group of airlines, McDonnell Douglas DC-10 group, and Collins Avionics.
There were two identical Control Display Units, CDU, located in the center pedestal. Each one consisted of a monochrome CRT, a full alphanumeric keyboard (non-qwerty), and line select keys. It displayed route, progress, performance and status info.
The two Navigation Computer Units, NCU, were located in the electrical and electonics equipment bay below the flight deck. They were about a foot wide, nine inches tall, and two feet deep, and weighed in excess of 60 pounds each. They contained plug-in modules along either side. The two NCU performed all calculations independently and communicated for comparisons.
Non-Volatile Memory consisted of two magnetic core memory modules, roughly 8 inches tall, 3 inches wide, and six inches deep. Each one had a capacity of 8 kilobytes of data, and they were 4-bit bytes, IIRC. Each bit was held by a tiny ferrite donut with five wires passing through it, and all the donuts were arrayed in a three dimensional grid. Being magnetic ferrites, they were not expected to survive a severe mechanical shock.
Two Flight Data Storage Units, FDSU, were located in the hat closet at the back of the cockpit. Each FDSU was a transport for a magnetic tape cartridge, which contained all route data. Swissair was the keeper of all KSSU member route data for the whole world, some 13,000 routes. Updated tape cartridges every provided on a 28 day cycle. Each route was identified with a five digit number. 92649, for example, might take you from Anchorage to Seoul.
Position sensors feeding the NCU included radials from dual VORs, distances from dual DME's, and data from three LTN-58 ISU, Inertial Sensor Units.
OPERATION:
To align the AINS-70, the pilot would enter the 5-digit route number. The computer would then bring up and display the route info. The pilot would select gate number of the departure airport from a list, and the NCU would then direct the alignment of the 3 ISU. One NCU was primary, and the other was automatically crossloaded for backup.
It took a noticeable amount of time for the NCU to build the route, selecting a swath of VORs and DMEs along the route. Once the route was complete, the pilot could select the SID and altitudes to fly. STARS were available for selecting at any time, also.
Once engaged for navigation, the AINS tuned the VOR/DMEs automatically, and navigated based on best inputs.
Once beyond VOR-DME reception, it relied solely on the three ISU. This was years before the LTN-72 triple mix became available.
AINS-70 to ANTARCTICA:
Participating airlines paid Swissair for creating the company routes and for update service. Swissair maintained the data base and Collins Avionics updated the tape cartridges. ANZ chose not to have routes created for the Antarctic flights, as it was only a few waypoints, and "What could go wrong?
The AINS-70 could be operated almost like a triple mix INS. That meant, however, the ANZ pilots had to enter full lat/long for probably their first time in a DC-10. No matter how many times the crew of 901 might have checked the numbers in the CDU to the numbers on the company flight plan given them, it was always right.
They "merely" failed to compare the numbers on the company flight plan to a chart.
-----------
GB