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Wake Turbulence behind an A-380



 
 
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Old November 22nd 05, 11:24 PM posted to rec.aviation.piloting
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Default Wake Turbulence behind an A-380

Yee-hah! Don't get too close to this whale...

Change in Rules
Needed for Wake
Of Big New Jet

By ANDY PASZTOR and DANIEL MICHAELS
Staff Reporters of THE WALL STREET JOURNAL
November 22, 2005; Page B1

Airliners may have to fly twice the normal distance behind the new
Airbus A380 superjumbo jet to avoid potential hazards from its
unusually powerful wake, according to preliminary safety guidelines.

The standards released to the industry by the International Civil
Aviation Organization earlier this month are tentative and almost
certainly more cautious than the formal rules expected next year. But
if the final air-traffic procedures end up close to ICAO's initial
proposal, they could undermine one of Airbus' top selling points for
the largest passenger plane ever built: greater efficiency at congested
hub airports.

Interim air-traffic control guidance from ICAO says the mammoth plane,
scheduled to go into service next year, produces "significantly
stronger" air turbulence than the largest jetliners now in use. Because
flight tests and data analyses "have raised concerns" about potential
safety issues, according to the guidance, it calls for minimum
separations of 10 nautical miles for all aircraft following a landing
A380, versus the typical five-mile mandatory buffer behind today's
largest aircraft.

For aircraft flying the same route directly behind an A380 at cruising
altitude, the recommended minimum spacing is tripled to 15 nautical
miles.

The interim rules are "very conservative" and will remain effective
"until conclusive guidance is issued mid-next year," said Paul Wilson,
a senior European air-traffic control official who is helping lead the
study. Initial plans called for the effort to be completed around
January, but now "there's a feeling more work needs to be done," Mr.
Wilson said yesterday in an interview. "What we want to do is get it
right" and rely on hard data, he added, because "we are leading the way
for all future aircraft" operating criteria.

The ICAO is a global aviation regulator whose standards and rules are
almost always accepted by individual governments.

Airbus, which touts the 555-seat A380 as "the economical solution for
heavily traveled routes," has sold it as a way to carry more traffic
without adding aircraft. The twin-deck jetliner can carry at least 35%
more passengers than Boeing Co.'s largest model, the 747-400. In some
configurations, the plane can handle more than 850 passengers.

The preliminary rules are already grabbing notice from Airbus
customers. A spokesman for Germany's Lufthansa, which has ordered 15
A380s, said "it is crucial for us that the separation is the same as
for a 747" because "we operate at congested airports."

The two-page ICAO advisory not only deals with the safety aspects of
air turbulence at low altitudes near airports but even raises questions
about potential hazards for nearby aircraft in midflight. The guidance
says the so-called wake vortices produced by the A380 -- twin cones of
turbulent air fanning out from its wingtips -- "will descend further
and be significantly stronger" than those from other large jets,
potentially even affecting jets traveling in the opposite direction
some 2,000 feet below. "Because it has not yet been possible to
establish the level of hazard" from such turbulence, the guidance
recommends "offset tracks or additional vertical spacing" for added
protection.

When an airborne aircraft runs into such turbulence, the impact can
jostle the trailing plane. In extreme circumstances, the result can
even be loss of control, though there haven't been any recent crashes
of jetliners attributed primarily to such encounters. Many years ago
the U.S. Federal Aviation Administration had to lengthen spacing
requirements for planes flying behind Boeing 757 jetliners, following a
fatal crash of a business jet that ran into a 757's wake.

Airbus has said the four-engine plane, with a maximum takeoff weight in
excess of a million pounds, is designed to fit seamlessly into
air-traffic systems world-wide without requiring greater spacing than
existing models or needing any other special handling by controllers.
An Airbus A380 marketing brochure in 2003, for example, said: "there is
no need to introduce any changes in separation standards" for the A380
because the aircraft's wake "is similar to that of the 747-400."

A spokesman for Airbus, which is owned 80% by European Aeronautic
Defence & Space Co. and 20% by Britain's BAE Systems PLC, declined to
comment, citing the ongoing studies. Despite the success Airbus has had
using computers to precisely predict handling and other characteristics
of the new plane, "we are still in the Stone Age for modeling" wake
turbulence, said Robert Lafontan, the A380's chief engineer, in an
interview several weeks ago.

The interim guidelines also recommend an additional wait of one minute
-- on top of today's typical two-minute spacing -- for smaller
jetliners taking off directly behind the giant A380. Once the A380
reaches cruising altitude, the guidance suggests that on "rare
occasions" its wake may be strong enough to shake planes flying nearly
half a mile below it and end up creating a "comfort issue" for
passengers in those jets.

With less than 160 orders and commitments for the A380, Airbus needs
about 90 more to break even. But the market is becoming more
competitive with Boeing's announcement that it is offering a larger 747
version.

The FAA, while particularly sensitive about any perception that it is
discriminating against the European planemaker, has been quietly
pushing for additional testing and more restrictive rules, industry
officials say. At the beginning of the year, an internal FAA report
projected that the A380's wake may result in fewer arrivals at some
airports; that the plane may require extra time or distance to execute
a missed approach to a runway; and it "may have an adverse impact" on
general airport operations. Air-traffic control officials, the report
concluded, are "uncomfortable" with the A380 and need answers quickly.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

 




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