Assalammualaikum,
i
read this piece of article via online @ CNN News. Thought of sharing with all. Let us pray and
hope for the best. In Shaa Allah.
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Editor's note: Bill Palmer, an Airbus A330
captain for a major airline, is the author of "Understanding Air France 447," an
explanation of the details and lessons of the crash of that aircraft in June
2009.
(CNN) -- Those trying to draw conclusions from the
information trickling from the investigation into the disappearance of MalaysiaAirlines
Flight 370 should go carefully.
It
is plausible that, as Malaysia's Prime Minister asserted, the plane's flying
for hours after losing contact with air traffic control was "consistent
with deliberate action," but it's not the only logical explanation of the
airplane's bewildering trajectory.
Statements
that the Aircraft
Communications Addressing and Reporting System was intentionally disabled,
for example, leave out the fact that the ACARS is required to send the
satellite contact requests (so-called "handshakes") that, according
to news reports, were reported to have occurred for hours after the flight's
disappearance.
The
plane has multiple functions and channels connected to the ACARS and at least
some of it must have still been working.
For
example, one part of this communications system is used for messages between
the airplane and air traffic control (clearances, position reports, etc).
Another is used to communicate, essentially with text messages, between the
airplane and the airline. Messages can also be sent automatically for maintenance
functions such as reporting faults and sending routine engine data. The range
of functions that would have been available for someone to disable is not yet
clear.
And
at least one news report described altitude excursions between 45,000 feet and 23,000,
which one pilot
suggested might have been done willfully to render passengers
unconscious. But this strikes me as behavior that would also be consistent with
the airplane flying completely unattended with the autopilot off. Though these
oscillations are larger than I might expect, it would be a natural behavior for
the airplane to fly relatively large but gentle pitch oscillations.
This
would be true especially if the airplane's auto-throttles were also for some
reason disabled. There have been statements made that such changes could only
be made by a skilled aviator, but what "skilled aviator" cannot hold
altitude within 20,000 feet?
Incapacitation
or something else that could prevent the crew from controlling the plane --
fire, collision, explosive depressurization -- could also be indicated, which
wouldn't necessarily mean the cockpit was breached by anyone.
The
airplane reportedly made "suspicious
turns." However, it is the nature of those turns that will
reveal if it was deliberate "heading" (directional) changes or if
nobody was flying the airplane at all. If the autopilot was off and the
airplane was essentially flying on its own, I would expect a variety of heading
changes. These changes could be initiated by turbulence during flight.
If
the airplane's routes were controlled intentionally by selecting the heading or
by programming the flight management computer, the flight path would be very
straight, then a turn that would last usually from 10 to 30 seconds, followed
by more straight flight.
While
a close-up analysis of the flight path would be required to determine the case,
it seems that officials are not even sure if the flight path headed northwest
toward Pakistan or southwest into the vast Indian Ocean.
On
the technical side, the Boeing 777-200ER is a fly-by-wire airplane -- that is,
movement of the controls is converted into electrical signals that interact
with flight-control computers and instruct the plane's control surfaces on the
wings and tail. Its characteristics may be able to explain much of the
airplane's behavior.
With
the autopilot off, the airplane will adjust the pitch (the up or down movement
of the nose of the plane) to maintain a speed set by the pilot. It will pitch
up if it's going faster than the desired speed and pitch down if slower. This
is called pitch trim. Anyone who has flown even a small aircraft will be
familiar with this concept. Therefore, when disturbed, it will fly a series of
pitch changes as it settles down on the trimmed airspeed.
Pitch
protections built into the system ensure that the airplane never goes too fast
or too slow. Temporary input on the control wheel, or changes in the airplane's
weight as it burns off fuel, temperature and other normal atmospheric changes
along the course can initiate the altitude changes as the airplane continues to
seek its trimmed speed.
Heading
changes are also what I would expect to see in an autopilot-off situation. The
777's fly-by-wire roll control law controls the tilt of the wings. The airplane
would be subject to atmospheric disturbances that could act to tip a wing up
every now and then, but built-in protections prevent the plane from exceeding
bank angles in excess of 35°. While a conventional airplane would tend to
spiral down in that situation, the 777 incorporates automatic pitch
compensation, so the airplane could easily hold its altitude in these turns.
The
fly-by-wire control system on the 777 makes it a very stable airplane, capable
of flying for hours with the autopilot off without crashing. If the
flight path can be shown to be very straight lines with neat turns followed by
another straight line, then I would throw out the "autopilot-off"
theory, but it seems as though officials can't even determine where the plane
was heading, much less the nature and cause of some heading changes.
The
consistent theme in the mystery of this flight has been very little data, and
the exact nature of that scant data is vague and changing. Whatever exact
scenario can account for the possible incapacitation or deliberate actions of
the crew, the loss of the transponder and other communications and the
airplane's mysterious flight path is likely to be a situation we have not seen
before.
I would urge that we not jump to
conclusions based on inconclusive evidence. The evidence we have may be
"consistent with deliberate acts," but it is also consistent with
other explanations as well.
