"Safety Aspects of Very Large Jet Operations Need to be Addressed"

Monday, January 22, 2001

Safety Aspects of Very Large Jet Operations Need to be Addressed
Air Safety Week


The monster jets are coming, and they bring with them safety challenges that
must be addressed. Some of the safety issues associated with these new, so-
called "Very Large Aircraft" (VLA) are controversial.

At the 80th annual meeting earlier this month of the Transportation Research
Board, manufacturers' representatives and airport officials discussed the
impact of these million pound-plus aircraft. The Transportation Research
Board (TRB) is an adjunct of the National Academy of Sciences, and the
annual meeting traditionally deals with aviation as a subset of other
transportation issues. This year, the session dealing with the looming
impact of VLA on an already strained U.S. airport infrastructure drew a
large audience.

Airbus Industrie already has formally launched its version, the 550-
passenger A380, and Boeing [BA] appears almost certain to counter with a
stretched and substantially redesigned version of its B747-400. Its VLA has
tentatively been dubbed the 747X Stretch. It will carry 504 passengers - 88
more than the current B747-400. The Airbus VLA is to enter service in 2006.

Both designs mark a substantial increase in size, with operating
implications both in the airspace around the airport and on the ground. The
B747X Stretch will be 262 feet long, with a wingspan of 237 feet. The
dimensions of the A380 match closely. The wingspan of the A380 pretty much
equals the length of the B747X Stretch, and the A380's length at 239 feet is
surprisingly close to the wingspan of the Boeing VLA. In other words, if one
were to place an A380 on top of and oriented 90? to the Boeing B747X
Stretch, the two super- jumbos would fit within the same size "box." The
"box" here is one that measures 80 meters (262 feet) on a side; this is the
current airport design template for jumbo jets. Sources advise that this box
involves reduced separation and will require "very accurate" docking at the
gate.

The manufacturers see their VLA designs as a cost-effective solution to the
capacity crunch (see ASW, 30 Oct. 2000, and Jan. 1). At a 5 percent annual
growth rate, 50 percent more passengers will be flying by 2008. There are
three ways to cope with this crush: (1) bigger aircraft, (2) new runways and
terminals at existing airports where there is space, or (3) new airports.
Airbus has concluded, and we quote, "When the frequency/slot limit is
reached, airport duplication or aircraft size increase is the only
solution." And, from this premise, Airbus concludes: "Adaptation to bigger
airplanes is more cost- effective than even more costly airports."

The contrary view is that the VLA could constrain capacity if it requires
handling the way some airports today deal with the arrival of the Russians'
giant six-engine AN-24. The area around the aircraft is kept well cleared.
Capt. Mack Moore, chairman of the airport and ground environment group for
the Air Line Pilots Association (ALPA), pointed out that the VLA is even
bigger than the AN-24. If it has to be treated similarly to assure adequate
margins of safety, the VLA "could turn out to constrain rather than enhance
capacity."

Various views about capacity are likely to persist until the VLA enters
service. Both the manufacturers and the skeptics have made their points. The
eventual adaptation to the VLA, however, involves the need to address a
number of safety-related issues (over and above more pedestrian
considerations, such as gate compatibility, jetway capacity, turnaround
time, impact of more passengers and baggage at peak airport hours, etc.).

Although there probably are more, five safety issues involving VLA emerged
at the TRB symposium: (1) wake vortex, (2) ground maneuvering, (3) balked
landings, (4) emergency evacuation, and (5) snow/ice removal on runways. We
address each, briefly, in turn:

Wake vortex. "The theoretic vortex strength of the A380 is only 10-15
percent higher than the B747," said John Lauber, head of safety for Airbus
Industrie North America. "We think the difference will be reduced basically
to zero through wing design," he predicted. That statement intimates the
hope that the separation standard for a "heavy" like the A380 and, say, a
B767 in trail during approach, will be virtually the same as for a B747 in
line ahead today. Lauber cautioned that "unnecessarily large vortex
standards must be avoided" (i.e., minimum separation distances). There is a
clear concern that excessive and potentially arbitrary separation standards
would impose a capacity constraint which, paradoxically, the VLA is intended
to relieve. The rules, Lauber said, "must be scientifically based." The
current standards are based only on maximum takeoff weight (MTOW). "Vortex
strength also depends on the wingspan loading and other aerodynamic
properties," Lauber explained. These parameters, he added, are not taken
into account for aircraft classification purposes.

Richard Marchi, senior vice president of technical and environmental affairs
for Airports Council International, believes the wake vortex issue is
manageable. The impact of reclassifying the B757 may have had a bigger
impact on capacity than the advent of the VLA, he suggested.

The pilots are more skeptical. Capt. Ross Sagun, chairman of ALPA's air
traffic control committee, described the wake vortex issue as "one of my
major areas of concern."

"You would be hard pressed to find an air carrier pilot that hasn't had a
frightening wake upset in his career," he said. Regarding the VLA, Sagun
declared:

"Here is my thought for the day: Any prudent and experienced sailor would
give a wider berth to the Exxon Valdez than he would a fishing trawler. I
think they are going to have a tough time selling the notion that there is
no difference. The answer lies with the science that has yet to be explored.
I am all for an engineering solution if they can come up with one. Having
said that, I think we can safely say that we would not be agreeable to the
'finger in the wind (it looks fine to us)' solution. We continually question
the adequacy of current wake separation standards. One only has to look at
the NASA database to see that we are experiencing far too many wake upsets
with the current standards."

Ground maneuvering. If anything can be concluded about taxiing a VLA, the
operative words that come to mind are "very carefully." Closed circuit
television, already installed in Boeing's B777-300 to facilitate taxiing,
likely will be featured in the VLA to assist pilots.

Capt. Ron Rogers, who has taxied the B777-300, said the turns require very
close attention. "I came within 18 inches of the edge," he said, recalling
the view of the main landing gear on the closed-circuit television screen in
the cockpit. Fillets, or edging at runway/taxiway intersections, may have to
be added to keep the main landing gear from rolling off the paved surface.
These modifications could impose millions of dollars in construction costs
to airports.

Lauber said the turning capability of the A380 would be similar to that of
the B777-300. Following the centerline, that turn would place the outer edge
of the right main landing gear about 14 feet farther out than a B747-400.
With airplanes like the B777-300 and the A340-600 needing more fillet space,
Boeing's David Nielson said, "The turning problem with today's pavement will
have to be solved well before the VLA."He suggested that the fillet
requirements could be reduced significantly through the use of
"oversteering." In this practice, pilots would not follow the centerline.
Rather, they would taxi farther into the intersection before initiating the
turn. The technique is sometimes called "judgmental oversteering." Boeing's
Nielson believes that with this technique the VLA "can use today's fillets."

Capt. Moore cautioned, "The bigger the airplane and the more restrictive the
pavement, the more accurate that judgment has to be."

Capt. Rogers is more hopeful. He said the practice of oversteering is
"pretty common" with today's stretched jets. Further, the most experienced
pilots are most likely to be the ones taxiing the VLA; thus, the taxiing
challenge will be in the hands of veterans. However, Rogers pointed out that
the Boeing graphic shows a case of turning from a 150-ft. runway to a 75
ft.-wide taxiway. It is "much tougher," he said, to turn from one 75-ft.
pathway to another that also is 75 ft. wide.

In any event, time is of the essence. If fillets are needed for an adequate
safety margin during turns, given the years it can take from project concept
to completion, "we have to get to work now on the fillets," urged Bill Fife.
He is vice president of New York based engineering consulting firm DMJM
Harris. Previous to his present position, Fife was involved in operations at
John F. Kennedy International Airport. He is acutely aware of the
operational impacts of the VLA, and of the long lead-time needed to pour
concrete.

Balked landings. A VLA on approach must be able to safely execute a balked,
or rejected, landing. The capability of the airplane to do so is not in
question. Rather, Marchi pointed out, the focus is on the airport. There
must be a sufficient obstacle-free zone. Presently, these zones appear
adequate if the aircraft is in the autoland mode. However, Capt. Moore
pointed out that in the vast majority of landings, the pilots are
hand-flying the aircraft using autothrottles and the flight director. With
respect to balked landings," he asked, "What kind of latitude do we need?
You have to look at the tail height of other aircraft." Analyses presently
are underway to determine the necessary size of the obstacle-free zone under
various landing conditions.

The balked landing was one of the particular concerns regarding land and
hold short operations (LAHSO) expressed by pilots at ALPA's 1999 safety
symposium (see ASW, July 26, 1999).

Emergency evacuation. "Can you get the people out of the upper deck in 90
seconds?" asked Marchi. The A380 marks the first full double-deck jetliner,
and literally hundreds of people will be on the upper deck. The 90-second
limit is based on the "burnthrough" time for the aluminum skin when exposed
to an external fire fed by a pool of spilled fuel. Airbus is designing the
A380 with new slides for the upper deck and a high-capacity stairway inside.

"Sooner or later there will be an actual evacuation of the A380," predicted
Capt. Tom Phillips, who also happens to be a firefighter serving as chairman
of ALPA's firefighting committee. "We will want to see a full-scale test,"
Phillips said. In other words, the use of computer simulations to
demonstrate compliance with the 90-second rule is likely to stir opposition.
Not only from ALPA, but also from the Association of Flight Attendants
(AFA). The flight attendants have strongly opposed the use of such
simulations to demonstrate compliance, and to certify smaller aircraft such
as the B777-300 (see ASW, April 6, 1998).

As for ALPA, Phillips said it would be "prudent" for the Federal Aviation
Administration (FAA) to investigate both the evacuation and the firefighting
issues. As an example, he said, the sheer number of people sliding to the
bottom of the evacuation slides presents a challenge. If not hustled quickly
to safe areas, these crowds of frightened, possibly traumatized or injured
passengers could impede the firefighting effort.

Firefighting, too, may become more of a challenge. "Because of the size of
the vessel (fuselage), we have a greater potential for people to survive,"
Phillips said. Firefighter training must heighten awareness of the potential
for "pockets of survivability" in such a large aircraft.

Runway snow/ice removal. The outboard engines on the four-engine VLA are
farther out from the airplane centerline. Far enough, in fact, to hang out
"beyond the edge lights," Fife observed. He pointed out that snow and ice
operations focus on clearing a 150 foot-wide runway, but with the VLA an
additional 60 feet must be cleared so the outboard engines will not collide
with snow and ice piled alongside. "You need an operating strategy," Fife
warned. Among the questions to be asked, he suggested: Do you need more snow
equipment? Can you push the snow and ice out to the side?

Capt. Rogers agreed there is a potential hazard for outboard engines.
"Snowbanks have already been an issue with the B747-400," he said.

The consensus among participants at the TRB symposium is that these issues
involving the VLA can be surmounted, but only if they are addressed now.

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