Posted on 06/27/2009 5:07:40 AM PDT by Erik Latranyi
A Northwest Airlines jet traveling from Hong Kong to Tokyo last Tuesday suffered a series of equipment and computer malfunctions strikingly similar to those encountered by Air France Flight 447 just before it crashed into the Atlantic Ocean on May 31.
The Northwest plane and its passengers, however, emerged unscathed. Details of the harrowing incident – described in a memo by one of the Northwest pilots and confirmed Friday by others familiar with the matter – highlight how cockpit crews can safely cope with something that is almost never supposed to happen: a system breakdown that prevented the crew from knowing how fast the plane was flying.
During the brief but dramatic event, the Northwest Airbus A330's crew was left without reliable speed measurements for three minutes. In addition, the computer safeguards designed to keep the aircraft from flying dangerously too fast or too slow were also impaired. Like the Air France A330 jetliner, the Northwest plane entered a storm and quickly started showing erroneous and unreliable airspeed readings.
(Excerpt) Read more at online.wsj.com ...
The question that comes to mind is this: Why hasn't this surfaced before on A330s? Suddenly, two events within a month?
I am willing to bet that such loss of airspeed sensors is more common than the average person thinks, but by reporting this, it makes it look like a design flaw.
Any aircrew out there who can comment?
Dont’ know about the big airliners, but when I was an undergrad pilot training instructor pilot, I’d have my students memorize power settings for a given airspeed, both in level flight, and during landing maneuvers. That way, a failure of the pitot/static system would not prove disastrous. Sounds like that pilot had the same training.
As for the Airbus - if it ain’t Boeing, I ain’t going.
While I am not an Airbus fan, it may be a more common problem that is not catastrophic.
Uh-oh! The next sound you hear is the mass scurrying of lawyers across the Atlantic!
Bookmark
And there's the key - the A330 was still working properly. The crew just had to know when to disregard incorrect feedback from the computers and instruments and do some old-fashioned flying - admittedly a tall order in an era when people have been conditioned to rely on automation for so many things.
GPS on Tomtom etc tells you how fast you’re going. 3d vs. 2d makes this impossible in the air?
The loss of airspeed sensing is extremely rare. However, crews are trained to set certain power settings and fly at specific pitch attitudes that will give them a margin of safety above the stall and below the buffet at the altitude and weight where they are operating. All modern aircraft have attitude indicators that are independent of the 'computer system' as back ups. 'Die by wire' systems are slightly different in that the power sensing and control may be more difficult to set manually due to the computer wanting to maintain authority. In any event, given the time and crew recognition of the problem it should be within their capability to safely fly the plane. Training,experience and knowledge of procedures...wash...rinse...repeat.
GPS shows ground speed, not air speed. There is a difference.
“GPS on Tomtom etc tells you how fast you’re going. 3d vs. 2d makes this impossible in the air?”
Aircraft GPS units are extremely accurate including airspeed.
I’m lost on why determination of air speed should be a problem then
A pilot on another thread noted that GPS only gives you ground speed. When you fly, the important thing is airspeed. If your airspeed is too low, you stall and crash. If too high, you break up and crash. Especially in a storm, airspeed may differ from ground speed by several hundred mph.
How do you measure air speed, as distinct from ground speed, with GPS?
The following is making the rounds among air line pilots and was sent to me by a Brazilian pilot of whom I am quite proud. He lived with us as an exchange student many years ago and knows my interest in aviation.
****************
Subject: Air France Accident: Smoking Gun Found
A Brazilian Naval unit reportedly found the complete vertical
fin/rudder assembly of the doomed aircraft floating some 30 miles from the
main debris field. The search for the flight recorders goes on, but given
the failure history of the vertical fins on A300-series aircraft, an
analysis of its structure at the point of failure will likely yield the
primary cause factor in the breakup of the aircraft, with the flight
recorder data (if found) providing only secondary contributing phenomena.
The fin-failure-leading-to-breakup sequence is strongly suggested in
the attached (below) narrative report by George Larson, Editor emeritus of
Smithsonian Air & Space Magazine.
It’s regrettable that these aircraft are permitted to continue in
routine flight operations with this known structural defect. It appears
that safety finishes last within Airbus Industries, behind national pride
and economics. Hopefully, this accident will force the issue to be
addressed, requiring at a minimum restricted operations of selected
platforms, and grounding of some high-time aircraft until a re-engineered
(strengthened) vertical fin/rudder attachment structure can be
incorporated.
Les(George Larson’s Report)-——————————
This is an account of a discussion I had recently with a maintenance
professional who salvages airliner airframes for a living. He has been at
it for a while, dba BMI Salvage at Opa Locka Airport in Florida. In the
process of stripping parts, he sees things few others are able to see. His
observations confirm prior assessments of Airbus structural deficiencies
within our flight test and aero structures communities by those who have
seen the closely held reports of A3XX-series vertical fin failures.
His observations:
“I have scrapped just about every type of transport aircraft from
A-310, A-320, B-747, 727, 737, 707, DC-3, 4, 6, 7, 8, 9, 10, MD-80, L-188,
L1011 and various Martin, Convair and KC-97 aircraft.
Over a hundred of them.
Airbus products are the flimsiest and most poorly designed as far as
airframe structure is concerned by an almost obsession to utilize composite
materials.
I have one A310 vertical fin on the premises from a demonstration I
just performed. It was pathetic to see the composite structure shatter as
it did, something a Boeing product will not do.
The vertical fin along with the composite hinges on rudder and
elevators is the worst example of structural use of composites I have ever
seen and I am not surprised by the current pictures of rescue crews
recovering the complete Vertical fin and rudder assembly at some distance
from the crash site.
The Airbus line has a history of both multiple rudder losses and a
vertical fin and rudder separation from the airframe as was the case in NY
with AA.
As an old non-radar equipped DC4 pilot who flew through many a
thunderstorm in Africa along the equator, I am quite familiar with their
ferocity. It is not difficult to understand how such a storm might have
stressed an aircraft structure to failure at its weakest point, and
especially so in the presence of instrumentation problems.
I replied with this:
“I’m watching very carefully the orchestration of the inquiry by French
officials and Airbus. I think I can smell a concerted effort to steer
discussion away from structural issues and onto sensors, etc. Now Air
France, at the behest of their pilots’ union, is replacing all the air data
sensors on the Airbus fleet, which creates a distraction and shifts the
media’s focus away from the real problem.
It’s difficult to delve into the structural issue without wading into
the Boeing vs. Airbus swamp, where any observation is instantly tainted by
its origin. Americans noting any Airbus structural issues (A380 early
failure of wing in static test; loss of vertical surfaces in Canadian fleet
prior to AA A300, e.g.) will be attacked by the other side as partisan,
biased, etc. “
His follow-up:
One gets a really unique insight into structural issues when one has
first-hand experience in the dismantling process.
I am an A&P, FEJ and an ATP with 7000 flight hours and I was absolutely
stunned, flabbergasted when I realized that the majority of internal
airframe structural supports on the A 310 which appear to be aluminum are
actually rolled composite material with aluminum rod ends. They shattered.
Three years ago we had a storm come through, with gusts up to 60-70
kts., catching several A320s tied down on the line, out in the open.
The A320 elevators and rudder hinges whose actuators had been removed
shattered and the rudder and elevators came off.
Upon closer inspection I realized that not only were the rear spars
composite but so were the hinges. While Boeing also uses composite
material in its airfoil structures, the actual attach fittings for the
elevators, rudder, vertical and horizontal stabilizers are all of machined
aluminum.”
“I’m lost on why determination of air speed should be a problem then”
GPS units aren’t part of the computerized automatic control system.
Unless the crew can quickly disconect the automatic control system and fly the aircraft by hand they are dead meat.
you would think your first checkoff on seeing a big change of groudspeed would be to see if the altitude were changing; a glass of water or the pit of your stomach ought to give you some idea.
This technique does not work in a storm where the wind direction and velocity may be shifting violently from second to second.
sorry to note...GPS indicates the speed over the ground not the airspeed...an example: one could be flying 400 MPH over the ground but have an airspeed of 450 MPH, it all depends on the wind speed and direction...tail winds add, head winds subtract...to add, this is an example, indicated airspeed is another topic....
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