The Olathe center also experienced an incident Aug . 5 when the primary radar failed for 70 minutes, but radio communications were never severed.
32.
Because primary radar generally gives bearing and range position information, but lacks altitude information, mode C and mode S transponders also report pressure altitude.
33.
Each primary radar had an associated secondary radar ( IFF ), SSR 750, with the smaller secondary radar mounted on the main primary radar aerial.
34.
Each primary radar had an associated secondary radar ( IFF ), SSR 750, with the smaller secondary radar mounted on the main primary radar aerial.
35.
In a transponder based system signals drop off as the inverse square of the distance to the target, instead of the fourth power in primary radars.
36.
The primary radar functions therefore results in detection and measurements of position if there is the presence of a target by the recognition of the useful signal.
37.
When primary radar information is restored at 9 : 05, controllers searching for Flight 77 to the west of its previous position are unable to find it.
38.
However, its primary radars, specifically its long-range 2D search radar, the Thales Nederland LW08, and its medium-range 3D surveillance radar, the Thales Nederland SMART-S, are to remain.
39.
Without the transponder, the controllers would have to rely on " primary radar, " microwave energy bounced off the plane's aluminum skin, but this is far less accurate.
40.
Boston Center could still track it on primary radar, but the operators in Rome would be hard-pressed to find it amid the jumble of blips on their screens.
