JD-EE
... by the time they changed over their selcal to Africa they were effectively out of range of VHF communications, as I recall.
To refresh your memory - here is an abbreviated version of events:-
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01:31:44z, the RECIFE VHF controller gave AF447 the ATLANTICO HF frequencies: 6649kHz (primary), 5565kHz (secondary), then 6535 kHz after the TASIL. The crew read back the three frequencies.
Note: TASIL is the boundary between the ATLANTICO and DAKAR Oceanic FIRs.
01:33:25z, the crew contacted the ATLANTICO controller on 6649kHz.
01:35:15z, they informed the controller that they had passed the INTOL point at 0133, at FL350. They announced the following estimates: SALPU at 0148 then ORARO at 0200. They also advised their SELCAL code: CPHQ.
01:35:26z, the ATLANTICO controller coordinated flight AF447 with the DAKAR controller.
01:35:32z, the ATLANTICO controller transmitted the following items to the DAKAR controller: TASIL estimated at 0220, FL350, Mach 0.82.
01:35:38z, the ATLANTICO controller sent a SELCAL call: CPHQ.
01:35:43z, the crew thanked the controller [assume that means, "SELCAL checks"].
01:35:46z, the controller asked them to maintain FL350 and to give a TASIL estimate.
01:35:53 ~ 01:36:14z, the ATLANTICO controller asked the crew three times for their estimated time passing the TASIL point. The crew did not answer.
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"Bear in mind that ATLANTICO and DAKAR don't share the same HF suite of frequencies,..." Of course not. Otherwise they'd spend the day talking to each other or at least interfering with each other.
There are limited Aeronautical HF frequencies available, and most oceanic FIRs share some if not all of the adjacent FIR's frequencies. RECIFE CONTROL operates remote VHF tx/rx from Fernando de Noronha (SBFN), and the SSR at SBFN is available to the RECIFE/ATLANTICO controlers (both in the ATC Recife Control Center). The ATLANTICO HF equipment is located near Natal (from memory). SSR was lost at around 0145 - 250NM from SBFN and VHF would have been marginal a few minutes later.
The talk of heavy QRN on the night in question is rather doubtful, as there has been no mention made of it by the BEA in their Reports, and no one to my knowledge has offered up any tapes to confirm it one way or the other. The only paths that matter are the a/c to ATLANTICO or DAKAR HF facilities.
AF459 reported -
On leaving the ATLANTICO FIR, through the TASIL waypoint, the crew attempted in vain to contact Dakar control in HF on the 5565 KHz and 6535 KHz frequencies, and on the other HF frequencies given in the on-board documentation. Likewise, the attempted ADS-C connection was unfruitful.
Strangely, they haven't made mention of static, and propgation or distractions at DAKAR could be the reason for the difficulty in making contact. In fact, it appears that 5565 is common to both FIRs and ATLANTICO gave AF447 the 6535 frequency, to get them "out of earshot" beyond TASIL.
Satellite observations reported no sign of lightning in the area during the critical period, i.e. 0200 ~ 0220z.
So in summary, the comms procedure with RECIFE/ATLANTICO was correct, and AF447 wouldn't normally be expected to call DAKAR until approaching TASIL, and if ADS-C had been established, DAKAR would give them a SELCAL check on HF along with further calling instructions. None of the final bit happened as the a/c became involved in some unscheduled events.
mm43