Primary Radar Coverage and use by ATC
There have been some posts regarding the use of primary radar (PSR) by ATC. The normal configuration for radars used by ATC in Malaysia is a 60 nm range PSR, co-mounted with a 200 nm range SSR, turning at 15 RPM. Of course these ranges are limited by the radar horizon and any terrain obstructions to the line of sight signal. The Military ATC radars are configured as a 50 nm PSR co-mounted with a 250 nm SSR, rotating at 15 RPM. See the Malaysian AIP ENR 1.6 for details.
The PSR/SSR configuration described above is common in many other countries, including Australia. In theory you can do without the PSR and just use SSR, however for busy approach control airspace (within 60 nm), PSR is used as an insurance against non-transponder aircraft (equipment failure, not switched on etc.). The PSR/SSR co-mounted configuration is the most economical way to provide ATS.
Long range PSR is much more expensive, and the rotation rate has to be slowed to about 5 RPM to obtain ranges to about 200 to 230 nm. 5 RPM will not normally support the use of 3 nm separation in approach airspace, thus reducing capacity. Hence the use of short range PSR/long range SSR @ 15 RPM – it provides surveillance for both approach control using PSR and SSR, and enroute surveillance using SSR only. ADS-B and Multilateration surveillance data are now also displayed at many ATCCs, but these, like SSR, are dependant or cooperative systems – no transponder and you are not seen.
It should be noted that at the time when MAS 370 disappeared, the airports and approach control services at Kota Bharu and Langkawi were closed. However the radars were turning to send SSR data to the KL ATCC at Subang for enroute surveillance. Butterworth/Penang, Kuantan, Subang and KL were open. In all cases all radar data would have been recorded.
Singapore ATCC has 220 nm range PSR, and 250 nm SSR coverage surveillance. However the LKP is 340 nm from Singapore, 96 nm from Kota Bharu and 290 nm from HCM and would be out of ATC PSR coverage. The Air Defence Radars are/should be a different story.
As an ex ATC (including time in Malaysia) I agree that the transcript shows a normal situation. I would be more interested in the transcripts of air/ground and ATC coordination communications after the MAS 370 data block disappeared from the ATCC displays. These may be revealed when the initial investigation report is released.