How KAL 007 was Lost
KAL 007, a Boeing 747 carrying 269 passengers and crew, was shot down by the Soviets on Sept. 1, 1983, just west of Sakhalin Island, after having entered twice into Soviet airspace due to a navigational error. This is the a summarizing of the International Civil Aviation Organization's analysis and presentation of that error.
Transoceanic passenger planes, such as KAL 007, use a number of navigational aids, the primary one at the time being the Inertial Navigation System (INS). The INS employs navigational "landmarks" called "way points." Up to nine way point co-ordinates are inserted into the three electrically linked INS units (one in front of the Pilot, one in front of the Co-pilot and one a "hot spare). The first two way points (after Anchorage) on KAL 007's flight from Anchorage to Seoul were Cairn Mountain (28 minutes into the flight) and Bethel (50 minutes into the flight). Along the route is a range of permissible deviation from the planned route termed the "Desired Track Capture Envelope." As long as the flight stays within this envelope, the autopilot can be captured and controlled by the INS when the pilot switches from Magnetic Heading to INS, and the plane can be brought back on track if it has strayed.
The plane was put on autopilot shortly after take-off and the "NAV Mode" set to "Magnetic Heading" (determined by the magnetic North Pole in northeast Canada, some 1,300 miles from true north). The plane began to deviate from its planned course about ten minutes into the flight and while navigated in Magnetic Heading mode. No reason is given in the ICAO report for this. The pilots were to switch the mode from Heading to INS prior to leaving the last U.S. continental way point - which was Bethel at the tip of Alaska. But the INS did not successfully engage the autopilot.*
There are two possible reasons why the INS had not captured the autopilot 
1. The pilots never set the autopilot mode to INS.
2. The pilots set the autopilot mode to INS but only after the deviating flight had passed outside of the 7.5 nautical mile (NM) envelope. This occurred shortly after the Cairn Mountain way point. At Cairn Mountain, the flight was already 6.5 miles off course but still within the envelope. If Air Traffic Control had notified KAL 007 that they had deviated from the course, they could have still corrected the situation by switching the NAV mode from Magnetic Heading to INS. At the hearing afterwards, the Air Traffic Controller for that sector acknowledged that he had not advised KAL 007 of its deviation as it was at that point negligible, and there was yet another continental reporting point and navigational aid yet to come (Bethel). Of all the flights that day, Air Traffic Control failed to mark the positions of only two - KAL 007 and KAL 015 which was 15 minutes behind. Congressman McDonald was aboard KAL 007; Senators Helms and Symms and Congressman Hubbard were aboard KAL 015. This failure of Air Traffic Control to mark down the position of KAL 007 and KAL 015 (and only those two flights) is both unfortunate and curious.
The pilots would have been assured by means of an indicator light that they had selected the autopilot for INS but they would have had no means of knowing through the INS diplay unit that since they were already outside the 7.5-mile envelope, the autopilot had, in fact, not come under the control of INS. "The lack of an indication on the flight director mode deprived the crew of a cue which might have drawn their attention to the fact that the autopilot was not being controlled by the INS."  The pilots would also have been able to correct "actual track" to desired track without using the INS by using Bethel's VORTAC (Very High Frequency Omni-Directional Range Tactical Air Navigation system) as a "course provider" instead of as just a "reporting station"
The VOR at Anchorage was out of order from 10:17 pm, August 23, to 12:39 am, September 2. (The crew of the flight had been warned of this fact via a Notice to Airmen or NOTAM.) If it had not been out of order and if flight 007 had been notified, it could have used the Anchorage "radial" to correct course—the VOR display on the plane would have read "from" instead of "to."
Normally, aircraft departing Anchorage for the Far East would be "tracking out", that is, using the Anchorage VOR radial for navigation along the desired track. Knowing that the Anchorage VOR was out should have increased the pilots' sense of the importance of verifying their position by using the radial from the VOR(TAC) at the next (and last) continental navigation station—the "gateway" station at the small fishing village of Bethel, Alaska.
By the time flight 007 reached way point Bethel, it was 12.6 NM off course. Continuing on its magnetic north heading, rather than the desired tracked set by its Inertial Navigation System (INS), KAL 007 would continue its deviation—60 nautical miles (NM) off course at way point NABIE, 100 NM at way point NUKKS, and 160 NM at waypoin NEEVA—until it would enter Soviet territory just north of Petropavlovsk on the Kamchatka Peninsula and then into harm's way over Sakhalin Island.
At 49 minutes after take-off, the pilot was reporting to be on course and at Bethel, "007, Bethel at forty-niner." But, in reality, they were far off course. For at 50 minutes after take-off, U.S. Air Force radar at King Salmon, Alaska had tracked KAL 007 at a full 12.6 nautical miles north of where it should have been (Bethel)--exceeding by more than six times, its permissible "leeway" drift from the course set by the INS.
The pilots could also have been apprised of their being off course by their Horizontal Situation Indicator (HSI), one in front of each pilot. The HSI, whose primary function was to show the aircraft's position with respect to the horizon, would also have shown that the aircraft was more than 8 miles deviated, as at 12.6 miles deviated, the indicator needle would be pegged all the way to the side to its 8-mile indication limitation. This not being noticed, was one of the indications to the ICAO analysts that the flight crew of KAL 007 displayed a "lack of situational awareness and flight deck coordination".
- (In order for the INS (calibrated to true north) to capture the autopilot and keep it on the desired track, the autopilot had to be set to "INS." The Digital Flight Data Recorder (DFDR) shows that the INS never captured the autopilot. KAL 007 flew at a "constant magnetic heading" of 245 or 246 degrees for the entire flight. If the INS had captured the autopilot, the magnetic heading would not have been constant but would have changed with each leg of the desired track since the waypoints were not in a straight line)
- Korean Airlines Flight 007
- Water Ditching
- KAL 007: Timeline of Interception and Shootdown
- Attack on KAL 007: From Inside
- Inertial Navigation System
- ICAO '93,Conclusions, 3.18, pg.59
- ICAO '93. conclusions, 3.11, pg. 59
- U.S. District court for the District of Columbia, Oct. 6, 1984,
- ICAO 1993, Pg. 43.
- ICAO '93, 2.6.1, pg. 43