787 Problèmes électriques

Les Boeing 787 Dreamliner cloués au sol



Publié le 17 janvier 2013 à 07h00 par François Duclos dans Actualité, Info pratique, Technologie - 0 commentaire


L’autorité américaine de l’aviation civile FAA a suspendu hier soir tous les vols en Boeing 787 Dreamliner jusqu’à ce que la fiabilité des batteries au lithium-ion soit prouvée, une décision suivie immédiatement par les autres pays.

La mesure annoncée par la FAA dans la soirée du 16 janvier 2013 ne concernait que la compagnie aérienne United Airlines,
seule américaine à avoir mis en service le dernier-né de Boeing (six au
total), mais elle a été immédiatement appliquée par la DGAC du Chili,
les deux 787 de LAN Airlines devant à leur tour être
immobilisés. Le régulateur américain estime que les défaillances de
batterie, rencontrées à deux reprises sur des Dreamliner de Japan Airlines puis All Nippon Airways, pourraient endommager les structures critiques et les systèmes, voire provoquer un incendie.

L’annonce a été faite suite à l’incident mercredi au Japon
d’un Dreamliner d’ANA, un atterrissage en urgence ayant été nécessaire
l’apparition de fumée due à une surchauffe de batterie. ANA et Japan
Airlines ont immédiatement suspendu tous leurs vols en 787 jusqu’à
aujourd’hui au plus tôt (elles en opèrent 24 sur les 50 en service),
annulant 38 vols pour la première et huit pour la seconde. Et le
gouvernement japonais a déclaré ce matin qu’il appliquera la directive
de la FAA.

L’Inde a suivi le mouvement, les six Dreamliner d’Air India
étant cloués au sol depuis ce matin après une enquête ordonné la veille
par le gouvernement. En Pologne le vol inaugural du 787 de LOT Polish Airlines
entre Varsovie et Chicago a décollé hier, mais les célébrations prévues
à l’arrivée ont été annulées, tout comme le vol retour. Les deux 787
avaient passé des vérifications hier selon le transporteur.

Pas de réaction officielle au Qatar à l’heure d’écrire ces lignes, mais les journaux australiens annonçaient ce matin que Qatar Airways repousserait le lancement du Dreamliner vers Perth, prévu en février. Ethiopian Airlines, qui a mis en service quatre 787, n’a pas communiqué depuis le dernier incident.

Boeing a réagi hier à la directive de la FAA par la
voix de son PDG Jim McNerney, qui s’est déclaré « confiant dans le fait
que le 787 est sûr », et mettra toutes les ressources de la compagnie au
service du régulateur et des compagnies « afin de trouver des réponses
le plus rapidement possible ». Tout en regrettant « l’impact des
évènements récents » sur les programmes de vol des clients et leurs
passagers.
http://www.air-journal.fr/2013-01-17-les-dreamliner-de-united-airlines-lan-airlines-cloues-au-sol-564474.html

The battery failures resulted in release of flammable electrolytes, heat
damage, and smoke on two Model 787 airplanes. The root cause of these
failures is currently under investigation. These conditions, if not
corrected, could result in damage to critical systems and structures,
and the
potential for fire in the electrical compartment.

CHICAGO, Jan. 16, 2013 /PRNewswire/ -- Boeing Chairman, President and
CEO Jim McNerney issued the following statement today after the U.S.
Federal Aviation Administration (FAA) issued an emergency airworthiness
directive that requires U.S. 787 operators to temporarily cease
operations and recommends other regulatory agencies to follow suit:


"The safety of passengers and crew members who fly aboard Boeing airplanes is our highest priority.


"Boeing is committed to supporting the FAA and finding answers as
quickly as possible. The company is working around the clock with its
customers and the various regulatory and investigative authorities. We
will make available the entire resources of The Boeing Company to
assist.


"We are confident the 787 is safe and we stand behind its overall
integrity. We will be taking every necessary step in the coming days to
assure our customers and the traveling public of the 787's safety and
to return the airplanes to service.


"Boeing deeply regrets the impact that recent events have had on the
operating schedules of our customers and the inconvenience to them and
their passengers."

Hot chemicals sprayed out of the battery on the 787 Dreamliner in
this week’s emergency landing in Japan, leaving a gooey dark residue and
suggesting a different malfunction than last week’s 787 battery fire in
Boston, according to two people with knowledge of the situation.

The residue covered the battery and splattered over nearby
instruments inside the forward electronics bay. It left a 12-foot-long
dark streak from the battery to an outflow valve through which some of
the spray vented overboard during the flight.

The people with knowledge of what was found inside the forward
electronics bay after the incident said the battery was not blackened
and cracked open like the battery in the Japan Airlines 787 fire a week
earlier at Logan airport in Boston.

“It’s not as bad as the earlier incident,” one person said, speaking
on condition of anonymity. “It looks like there wasn’t a fire. But
there was a significant overheating.”

Two further sources confirmed that there was no fire inside the airplane.

The residue may have been from smoke or from hot, vaporized electrolyte, the potentially flammable chemical inside the battery.

But even without a fire, “it’s still a problem” that the electrolytes sprayed out of the battery box, said one person.

Four independent control circuits govern how the battery charges, ensuring that it neither over-charges nor discharges too much.

Boeing believes these circuits may have done their job as designed
and stopped the overheating before a fire could start, one person said.

Boeing senior vice president Mike Sinnett, who is responsible for the
plane’s electrical systems, said in an interview last week following
the Logan fire that those controls, two inside the battery and two
external, would prevent any serious battery incident.

He added that Boeing tests showed that any smoke from a less serious
battery overheating incident in flight would exit through the outflow
valves overboard, ensuring none entered the passenger cabin or the
cockpit.

But the Federal Aviation Administration (FAA), announcing its
decision Wednesday to ground the 787 fleet, indicated it is not
satisfied that these systems worked as designed. It stated that both
battery incidents resulted in the “release of flammable electrolytes,
heat damage, and smoke.”

ANA said Wednesday that the pilots did smell something that they
thought was smoke, and that this smell was also in the passenger cabin.

That, along with warnings of battery trouble on the instrument panel,
is what impelled the pilot to make the emergency landing, deploy the
emergency exit slides and evacuate all 137 passengers and crew.

Two people with knowledge of what happened said the pilot received
three battery warning messages during take-off after an initial status
message.

One of those messages warned that the battery was overheating.

The 787 batteries are made by GS Yuasa of Japan. Its manufacturing
processes will likely be the immediate focus of attention once
investigators learn precisely what went wrong in each of the two
incidents.

Boeing
must demonstrate that it has eliminated any risk of a battery-ignited
fire before the grounding will be lifted. Jim McNerney, Boeing's chief
executive, says the entire resources of the company will be put at the
disposal of the effort to discover the source of the battery fire risk
and to correct it.

The company needs to find out whether the emergency landing
in Japan yesterday was caused by an issue with the battery or
the entire electrical system is at fault, its spokesman Hiroharu
Nakano said by phone today. The plane’s electrical system needs
to be dismantled for the full investigation, which may take
months, he said.

From the Buckingham note

We think BA does have alternatives if it decides to replace the current Li-Ion batteries.

1. We recently spoke with EaglePicher, a competitor to GS Yuasa (787 battery maker).
   
2. EaglePicher has a Li-Ion battery technology currently being certified for a business jet.
   
3. EaglePicher notes it could have a 787 Li-Ion battery designed and certified in 12-15 months.
   
4. EaglePicher’s Li-Ion battery conforms to current (and far stricter) FAA standards for Li-Ion batteries.
   
5. Consequently, we think BA has design alternatives if it decides to replace the current battery.

Les Boeing 787 Dreamliner interdits de vol dans le monde entier

L'Expansion.com avec AFP - publié le 17/01/2013 à 06:36, mis à jour à 10:37
L'autorité
américaine de sécurité aerienne a interdit tous les vols de Boeing 787
Dreamliner à travers le monde, suite à la série d'incidents. L'enquête
se concentre sur le système de batterie.



Les boeing 787 Dreamliner sont cloués au sol par les autorités américaines, japonaises et indiennes.Le français Thales sera

REUTERS/Kyodo


La FAA, l'autorité américaine de sécurité aérienne, a interdit dans
la nuit de mercredi à jeudi tous les vols de Boeing 787 Dreamliner à
travers le monde en raison des problèmes de batterie rencontrés au Japon, a-t-on appris auprès de l'autorité européenne AESA à Cologne (ouest).
"C'est
une décision rare", a déclaré un porte-parole, soulignant que seul le
pays de fabrication de l'appareil était habilité à prendre une telle
décision au niveau mondial.
La FAA américaine avait auparavant
ordonné mercredi aux six Boeing d'United Airlines de rester au sol, une
annonce qui a conduit le ministère japonais des Transports à faire de
même pour les 17 appareils d'All Nippon Airways (ANA) et les 7 de Japan
Airlines (JAL), déjà rivés sur le tarmac depuis la veille. Un Dreamliner
d'ANA a dû atterrir d'urgence mercredi matin à Takamastu (sud du Japon)
à cause d'une alarme signalant la présence de fumée et d'une odeur
forte à bord en provenance de la batterie.
Il s'agit du deuxième
incident ce mois-ci impliquant une batterie au lithium-ion. "La batterie
a changé de couleur", a expliqué ANA. L'autre problème ressemblant,
constaté la semaine passée à Boston sur un appareil de JAL, a aussi
entraîné des fuites d'électrolytes inflammables, des émanations de
chaleur et de la fumée, selon la FAA, laquelle n'autorisera pas les
Dreamliner enregistrés aux Etats-Unis à redécoller tant que les
batteries ne seront pas jugées sûres.
Au Japon, les enquêteurs
dépêchés par le Bureau de l'aviation civile et la Commission de sûreté à
Takamatsu se concentrent également sur l'examen de la batterie,
fabriquée par la société japonaise GS Yuasa, et intégrée dans un
ensemble électrique conçu par le groupe français Thales. "La batterie
montre des anomalies visibles à l'oeil nu, mais le système électrique
est complexe et exige d'autres investigations", a déclaré le
vice-ministre des Transports japonais.
Le Français Thales en cause?ANA
a par ailleurs précisé que la batterie en question était neuve, un
remplacement ayant été effectué récemment, le 17 octobre, après un souci
sur celle d'origine. A la demande des autorités, la société qui
fabrique la batterie lithium-ion, GS Yuasa, a dépêché jeudi matin trois
ingénieurs à Takamatsu. "Nous avons confiance dans nos batteries
lithium-ion, mais nous voulons coopérer pleinement avec les enquêteurs",
a indiqué à l'AFP une porte-parole de GS Yuasa.
"A ce stade,
nous ne savons pas si le problème provient de la batterie elle-même ou
du système électrique dans lequel elle est intégrée", a-t-elle ajouté.
Et de préciser: "GS Yuasa ne fournit pas directement les batteries à
Boeing, mais les livre à Thales qui les assemble dans un ensemble de
conversion électrique". Des techniciens de GS Yuasa s'étaient déjà
rendus aux Etats-Unis la semaine dernière après un départ de feu dû à
une batterie sur un autre Boeing 787 de Japan Airlines (JAL) qui venait
d'atterrir à Boston.
Outre les deux incidents de batterie, cinq
autres avaries se sont produites sur des exemplaires japonais du
dernier-né de Boeing en deux semaines: deux fuites de carburant, un
écoulement d'huile, un pare-brise ébréché en vol et un souci sur le
système de frein. Vendredi la FAA avait annoncé le lancement d'une
enquête "approfondie" sur le 787. Le Bureau américain de la sécurité des
transports (NTSB) a par ailleurs annoncé mercredi l'envoi d'une
enquêtrice au Japon.
Face à cette succession de revers, le PDG de Boeing Jim McNerney s'est voulu rassurant.
"Nous
prendrons toutes les mesures nécessaires dans les jours à venir pour
rassurer nos clients et les voyageurs sur la sûreté du 787 et pour que
ces avions reprennent leur service", a réagi M. McNerney dans un
communiqué publié après la décision des autorités américaines. "Nous
avons confiance dans le fait que le 787 est sûr", a-t-il martelé.

Not only the 50 Dreamliners already in service with airlines around
the world have been grounded — Boeing can’t even conduct test flights on
the newly built planes parked outside its Everett factory.

The interim solution Boeing has offered to the FAA includes stringent
one-time inspections of the lithium ion batteries on the jets, as well
as detailed instructions for pilots to do preflight battery checks, said
a person with knowledge of the situation.

“Boeing is proposing a way of doing a complete health check on every
battery as part of a solution to get the planes back in the air,” the
person said, speaking on condition of anonymity.

“It’s also proposing some measures that would hopefully allow pilots
to catch error messages that might be a precursor to battery failure
before a plane leaves the ground.”

However, that person and another with indirect knowledge of the
negotiations said it’s unclear whether the FAA will accept such interim
fixes until the underlying reason for the battery problems is known.

And as of Thursday afternoon, the first person said, “nobody has a clear answer yet.”

That leaves considerable doubt that the grounding can be resolved quickly.

In the case of the 787, two 32-volt li-ion primary batteries provide
power as key elements of the aircraft’s more-electric architecture. The
main battery, located forward in the electric/electronic equipment bay
below the cabin floor by the front passenger doors, provides power for
aircraft startup, ground operations such as refueling and towing, and
acts as a back up power for the electrically actuated brake system. It
can also assist the second battery, located in the aft E/E bay, in
starting up the auxiliary power unit (APU) and, in the event of a power
failure, energizes essential flight instruments in the flight deck until
the drop-down ram air turbine spools up.
The battery that caught
fire on the Japan Airlines 787 in Boston was the second main battery.
This unit’s primary purpose is to electrically start the APU when
neither of the engines is running and the aircraft is not connected to
external ground power. In this case, the battery energizes the right
hand of the two starter/generators connected to the APU. The aft battery
also provides another minor role, namely power to the navigation lights
during battery-only towing operations. The unit in the second incident,
which forced an ANA 787 to make an emergency landing in Japan on Jan.
16, involved the main battery in the forward E/E bay. In this case,
there was less damage, though spilled electrolytes, fumes and minor
thermal damage indicated signs of overheating.
Need For Power
Mike Sinnett, 787 VP and chief project engineer,
says the li-ion battery has “the right chemistry it takes to have a
large amount of energy in a short time to do the APU start, and allows
us to recharge that in a short amount of time.” These qualities, added
to the low weight, were sufficient to swing Boeing in favor of the
technology in 2005, when it awarded the battery contract to Japan-based
battery manufacturer GS Yuasa as part of the Thales-supplied electrical
power conversion system. The 787 contract marked the first commercial
aviation application of li-ion technology and was selected over
contemporary nickel-cadmium because it provided 100% greater energy
storage capacity and double the energy from the same-sized unit.
“Li-ion wasn’t the only choice, but it was the right choice for us at the time,” said Sinnett.
However
Boeing knew the outstanding performance of li-ion technology comes at a
cost, namely development of an elaborate series of safeguards to
prevent the battery catching fire.
The GS Yuasa unit and its
charging system are designed to modulate and control the energy flow, so
that over-charging, one of the identified causes of li-ion battery
fires, cannot occur. Similarly, Boeing developed safeguards both inside
and outside the battery, to prevent it from over-discharging, or
over-heating, both triggers for fires. However, in the worst case
scenario, which is known as a thermal runaway, once the reaction begins
there is very little to be done. As Sinnett says, “Fire suppressants
just won’t work. It’s very difficult to put out with suppressants and
you just have to assume it’s going to go.”
The problem lies with
the lithium at the heart of the battery. Although this has twice the
electrochemical potential of other materials, it also melts at much
lower temperature than other battery fuels, such as nickel. Energy
experts tell Aviation Week lithium melts at 357 degrees F versus 2,800
degrees F for nickel, and acts “like molten sodium” in the process.
The
other issue associated with the battery design is that to generate the
high energy density the unit is made up of a stack of tightly packed
cells. Each cell consists of a layer of lithium, acting as the cathode,
separated from an oxidizer, or anode, by a thin layer of ion conductive
polymer. If a short occurs and the lithium melts, the lithium reacts
first with the electrolyte and then the oxidizer before propagating to
other cells. This process, which does not occur with nickel-cadmium or
nickel-metal hydride batteries is the thermal runaway circumstance cited
by Boeing.
Chain Reaction
If the chain reaction starts, as
is believed to be in the case of the Boston event, the current procedure
in flight is to vent smoke overboard from the E/E bay. The energy
release from the lithium, however, cannot be stopped and will only cease
once the material has been consumed by the reaction. The initial NTSB
investigation found that although the APU battery had been severely
damaged by the fire, the thermal damage to the surrounding structure and
components was “confined to the area immediately near the APU battery
rack (within 20 in.) in the aft electronics bay.”
However, while
this would appear to be good news in terms of containment, an update
from the NTSB released on Jan. 14, indicated that Boston fire fighters
had been “able to contain the fire using a clean agent (Halotron),”
suggesting that without their efforts the damage would almost certainly
have been far worse.

The urgency of protecting the plane from smoldering or burning power
packs is heightened by the fact that the batteries can't simply be left
disconnected until necessary fixes are made. That's because the 787's
main lithium battery serves as the primary source of electricity for
some key systems when the jetliner is flying.