For Air France Flight 447, the A330 that disappeared enroute from Rio de Janeiro (GIG) to Paris (CDG), there are many news reports that state the pilots made no “Mayday” call. As an example, the AP story states, “The crew made no distress call before the crash, but the plane’s system sent an automatic message just before it disappeared, reporting lost cabin pressure and electrical failure.”
But how does the AP writer know this? It can be said that no distress call was received or heard, but we don’t know for sure if a distress call was made or not. If indeed no call was attempted, it could suggest that communication means were compromised or that the pilots themselves were incapacitated. The automatic system sent out a message of a loss of pressurization. In the Payne Stewart accident in the US in 1999, a Learjet flying Orlando to Dallas experienced a loss of pressurization which led to a drop in oxygen and thus consciousness, and the crew and passengers died of hypoxia (and the aircraft continued flying before ultimately crashing in a field in South Dakota).
But if the pilots were not incapacitated and the communication system was not compromised, there are two probable scenarios:
1) Attention was focused on the trying to navigate and control the aircraft given the emergency they were experiencing, particularly given the fact that a distress call may not be heard in the time they had available, particularly given communications constraints; or
2) They did issue a distress call but it was not heard given the limited communications available at their assumed location 650km NE of Brazil, in the middle of the Atlantic.
In scenario 1, above, priority was given—as it should have been—to fly the aircraft, just as the old saying goes, “aviate, navigate, communicate.”
In scenario 2, one must understand the difficulty of communications over the open ocean, and hence support for scenario 1. VHF radio does not extend very far offshore and thus communication back to land via VHF was not possible. VHF communication to other nearby aircraft is possible, but in AF447’s case, there may not have been any other aircraft in range at that moment. So a MaydDay issued on VHF may not have been heard by anyone. In the middle of the ocean, HF radio is the primary form of communication with ATC, but with significant noise and static, it is very difficult to hear one another, and issuing a distress call over HF could take numerous attempts and several minutes just to connect given poor reception, atmospheric conditions, or frequency congestion. And they may not have had several minutes waiting to connect.
Knowing this, if the pilots—if conscious—did indeed not issue a MayDay call, it may well be because they knew the challenges of communication over HF radio—even just connecting—and instead—quite understandably—focused their attention on managing the emergency they were experiencing. Or maybe they did try and never connected. Or they connected but were not heard or understood. Or they tried over the VHF and no one was nearby to hear them. Or maybe they were incapacitated by the time of catastrophic failure.
One thing we do is that we don’t know what really happened and that it’s too early to state with certainty such things as whether or not a distress call was made. And we never know…only that one was never heard.
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