PAVING TRENDS
Funding, technical considerations
by Jim LaFrenz, American Concrete Pavement Association
Of the $3.2 billion available in AIP funds
for 2002, about $1.4 billion could be used for runways and other pave-ments.
Congress has also made it clear that AIP funds will not be used for security
purposes in order to safeguard much-needed construction funding.
Large airports, in the first year of AIR-21,
used their entitlements for fire equipment, vehicles, and other capital
equipment. They are now turning entitlements to con-struction. Small and
medium air-ports have been banking their enti-tlements that will now flow
into con-struction, beginning in 2003.
The need for expansion and facilities improvement
is greatest among the small to medium air-ports. Not used to having funds
available prior to the passage of AIR-21, these airports are in critical
need of pavement rehabilitation to meet increasing demand.
FOCUS SHIFTING TO SMALL AIRPORTS
Prior to AIR-21, there was a void in criteria
and standards for small air-ports, as well as a lack of funding. FAA never
had accurate design criteria for pavement supporting aircraft less than
100,000 lbs. With the passage of AIR-21 — and first-time funding
for general aviation airports — Congress is sending a strong message
to the industry. It not only seeks to ease the burden on pri-mary airports,
but demands that air travel be more accessible to people who happen to
live far from a primary airport.
Another trend is the significant increase
in air taxis flying out of non-primary airports as business people look
for convenient, no hassle alterna-tives to large busy airports. Plus,
many travelers, mindful of the threat of ter-rorists, feel smaller aircraft
are less like-ly to be a target.
Small airports in the Northeast and Upper
West parts of the country — Montana, Colorado, the Dakotas —
are experiencing increased customer demand. A growing number of airlines
are basing their business on flying in and out of small to medium airports
using smaller airplanes and more fre-quent flights.
BALANCED PAVEMENT DESIGN; LESS $$
Apart from safety concerns, the single
biggest priority of the small air-port operator regarding pavement is
initial cost. The reason so few small air-ports have concrete pavement
is its higher initial cost. Take cost out as a factor and most airport
owners would choose concrete.
Initial cost does not have to be an issue.
FAA doesn’t have separate stan-dards for pavements carrying less
than 100,000-pound aircraft, but requires a minimum eight-inch thickness
for all concrete airport pavements supporting turbine-engine aircraft.
That’s a lot more pavement than a general aviation airport needs.
Because smaller airports don’t need the pavement structure that supports
a large airport’s heavy aircraft and busy flight schedules, they
can save money by designing pavements to han-dle lighter loads.
The Airport Consultants Council has unofficially
agreed to review the new pavement design for smaller air-ports developed
by ACPA. The two organizations will then coordinate with industry to achieve
consensus on both small airport design specifications and a refined P501
concrete paving specifi-cation — prior to presentation to FAA.
Following are some examples of how new
design specifications mesh with current FAA standards:
• For the ATR 42, a typical
small regional jet weighing 36,000 pounds, the FAA criteria requires a
minimum eight-inch-thick concrete pavement. The correct criteria based
on the air-craft type calls for only a six-inch con-crete pavement thickness.
• For the Shorts 360, a small
cargo airplane weighing 27,000 pounds, the FAA says six-inch pavement
is enough. But because this specification does not pay attention to wheel
loads, the necessary pavement is actually seven inches thick. This reinforces
how important it is to incorporate aircraft type into the design of balanced
pavement.
• For the Gulfstream G-V, weighing
91,000 pounds, the FAA criteria call for 11-inch pavement. The small airport
criteria also require 11-inch pavement. This is because near the 100,000-pound
range, both criteria begin to concur; for aircraft over 100,000 pounds,
they are in complete agreement. Discrepancies in criteria only appear
for aircraft under 100,000 pounds.
These new specifications don’t nec-essarily
promote thinner pavement, but balanced pavement design — design features
of the pavement come togeth-er to produce the most economical structure
for a particular airport. Of course, there’s no optimum design for
airport pavement; aircraft weights, fre-quency of operations determine
design. Balanced design offers tremendous resource conservation by requiring
only the necessary amount of pavement for a specific kind of aircraft
and a specified number of landings and takeoffs.
In fact, the entire airline industry is
moving to aircraft designs with a lighter footprint — ones that don’t
require as thick a pavement. That allows large air-ports as well as smaller
ones to save on construction costs.
LESS MAINTENANCE
The second priority, after initial cost,
is reducing pavement mainte-nance and repair. CPR (concrete pave-ment
restoration) has always been an ongoing activity at airports, although
smaller airports never had funding for repairs prior to AIR-21. To guide
all air-port owners, a new publication from ACPA, available in July, describes
vari-ous methods to most economically repair and rehabilitate airport
concrete pavements.
One economical rehabilitation method, overlays
and UTW, have been used extensively on highways, city streets, and country
roads. These tech-niques are being refined to most effi-ciently meet the
needs of airports through education and training pro-grams and research
projects.
About the Author
Jim LaFrenz, P.E., is director of airports
for the American Concrete Pave-ment Associa-tion. He works closely with
the FAA, and serves as a technical resource to airport owners and consultants
through ACPA’s affili-ated Chapter/State associations.
He can be reached at [email protected].
