[Federal Register Volume 62, Number 248 (Monday, December 29, 1997)]
[Rules and Regulations]
[Pages 67555-67556]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-33753]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 91
[Docket No. 28870; Amendment No. 91-254]
RIN 2120-AE51
Reduced Vertical Separation Operations
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Disposition of comments on final rule.
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SUMMARY: On March 27, 1997, the FAA adopted requirements for Reduced
Vertical Separation Minimum (RVSM) airspace. The rule provided
requirements for operating in airspace between flight level (FL) 290
and FL 410, with assigned altitudes separated by a minimum of 1,000
feet, rather than the 2,000 foot minimum separation previously required
above FL 290. The amendment made more tracks and altitudes available
for air traffic control to assign to operators, thus increasing
efficiency of operations and air traffic capacity. The action
maintained a level of safety equal to or greater than that provided by
the previous regulations by requiring improved altitude-keeping
performance to participate in RVSM. This action is a summary and
disposition of comments received on the final rule.
ADDRESSES: The complete docket for the final rule on RVSM may be
examined at the Federal Aviation Administration, Office of the Chief
Counsel, Attn: Rules Docket (AGC-200), Room 915-G, Docket No. 28870,
800 Independence Ave., SW, Washington, DC 20591, weekdays (except
federal holidays) between 9:00 a.m. and 5:00 p.m.
FOR FURTHER INFORMATION CONTACT:
Roy Grimes, AFS-400 Technical Programs, Division, Flight Standards
Service, Federal Aviation Administration, 800 Independence Avenue SW.,
Washington, DC 20591, telephone (202) 267-3734.
SUPPLEMENTARY INFORMATION:
Background
With air traffic increasing annually worldwide, FAA airspace
planners and their international counterparts continually study methods
of enhancing the air traffic control (ATC) system's ability to
accommodate this traffic in a safe and efficient manner. The traffic
problem has become particularly acute in the North Atlantic (NAT)
airspace, where the number of flight operations increased 30 percent
from 1988 through 1992, according to the NAT Traffic Forecasting Group.
The forecast indicated that traffic will rise 60 percent over the 1992
level of 228,200 operations by 2005. Currently, 27 percent of
operations in the NAT airspace receive clearances on tracks and to
altitudes other than those requested by the operators in their filed
flight plans because of airspace limitations. These flights are
conducted at less than optimum tracks and altitudes for the aircraft,
resulting in time and fuel inefficiencies.
One limitation on air traffic management at high altitudes is the
required vertical separation. At altitudes lower than FL 290, air
traffic controllers can assign aircraft operating under Instrument
Flight Rules (IFR) altitudes a minimum of 1,000 feet apart, however,
above FL 290, the required vertical separation was a minimum of 2,000
feet prior to this final rule. (Note: Flight levels are stated in
digits that represent hundreds of feet. The term flight level is used
to describe a surface of constant atmospheric pressure related to a
reference datum of 29.92 inches of mercury. Rather than adjusting
altimeters for changes in atmospheric pressure, pilots base altitude
readings above the transition altitude (in the United States, 18,000
feet) on this standard reference. FL 290 represents 29,000 feet; FL 310
represents 31,000 feet, and so on.)
The 2,000 ft minimum vertical separation above FL 290 previously
restricted the number of flight levels available, even though many more
air carrier and general aviation aircraft are capable of high altitude
operations now than when the 2000-foot separation standard was
established. Flight levels 310, 330, 350, 370, and 390 are flight
levels at which aircraft crossing between North America and Europe
operate most economically, thus causing congestion at peak hours. Now,
with the issuance of the RVSM final rule, air traffic can make
available other flight levels, such as 320, 340, 360, and 380.
Exhaustive technical studies showed that a 1,000 ft minimum vertical
separation was both feasible and safe. The solution was based on marked
improvement in altitude-keeping technology and provided relief from the
fuel and time inefficiencies seen in the North Atlantic Minimum
Navigation Performance Specifications (NAT MNPS) airspace prior to the
issuance of the RVSM final rule.
Discussion of Comments
The FAA received three comments on the RVSM final rule.
The first commenter, the Air Line Pilots' Association (ALPA),
states that some pilots have been receiving traffic advisories (TA's)
from their Traffic Alert and Collision Avoidance Systems (TCAS). The
TA's have been encountered between same direction aircraft separated by
1000 feet, that are in close longitudinal proximity to each other with
similar cruising speeds. ALPA writes that pilots have reported TA's
lasting as long as twenty minutes, requiring innovative actions to
eliminate them. They point out a lack of defined procedures for
handling annoying TA's. Although ALPA is not aware of an occurrence,
they believe the current TCAS logic leaves open the possibility of a
disruptive long duration resolution advisory (RA) in the RVSM
environment. Their concern is the possibility that this type of event
could cause a serious problem in RVSM airspace from the close proximity
of traffic and pilot training that requires compliance with RA
commands.
ALPA's second area of concern is wake vortex encounters. Pilots
have reported numerous encounters with turbulence produced by B-747 and
B-777 aircraft using RVSM separation. Although ALPA is not aware of any
serious cases reported, these operational characteristics did not exist
when the 2000 foot standard was in use. ALPA points out the absense of
procedures to help pilots avoid or exit areas of descending vortex.
ALPA recommends the development of an operations plan by the North
Atlantic Systems Planning Group (NATSPG) which would provide procedures
that could resolve both the TCAS and wake vortex problems. Some
suggestions included lateral offset, Mach number change so as to change
longitudinal geometries, and planned offset of each odd or even flight
level.
ALPA also suggests a centralized data collecting effort that
ensures the reporting of TCAS and wake vortex events. They believe the
two problems could best be evaluated through the collection of data for
analysis and processing.
The FAA appreciates ALPA's comments regarding the effect of RVSM on
TCAS operations. The FAA, in conjunction with the other North Atlantic
air traffic service (ATS) providers has requested that the ARINC
[[Page 67556]]
Corporation conduct a study of TCAS in NAT RVSM airspace. (ARINC
already provides contract support to the FAA TCAS Program Office as
well as the NATSPG). The purpose of this study is to better understand
the parameters that can lead to multiple traffic alerts and also to
understand better the performance of TCAS change 7 in the RVSM
environment. This study began in September 1997.
In regards to wake turbulence encounters, the FAA, in coordination
with the NAT ATS providers, has published a contingency procedure that
gives a pilot encountering wake turbulence the option of offsetting
from the track to avoid the turbulence. This procedure has been
coordinated with the International Federation of Air Line Pilots'
Association (IFALPA) and was published by the NAT ATS providers in
September, 1997.
The second commenter, National Air Transportation Association
(NATA), states concern that future expansion of the RVSM operational
altitudes would not address the hundreds of business aircraft currently
operating over the North Atlantic. NATA's concern comes from the
apparent lack of concern from ``aircraft manufacturers to provide
support for upgrading a previously manufactured aircraft's systems to
meet RVSM specifications.'' NATA also believes that a substantial
financial investment is required to meet RVSM specifications, and that
expenditure is beyond the ability of many aircraft operators.
The FAA will be working with the user community to develop a
position on the expansion of RVSM flight levels in the NAT. A U.S.
position on this issue will be needed for the December 1997 meeting of
the NAT Implementation Managers' Group. To accomplish this, the FAA
held a meeting of the RVSM Steering Group in September 1997. At this
meeting, the user community, including NATA, was given the opportunity
to express their views on RVSM expansion. There will also be a follow-
up meeting in December, 1997. Also, the International Business Aviation
Council has been given the opportunity to provide a representative to
the December meeting. A major issue to be addressed is the readiness of
the business aircraft fleet to operate within RVSM.
The third commenter, an individual pilot, believes the
implementation of RVSM is too broad. The commenter asked why the
program was not implemented in `The Tracks' first. Then asked, why is
there an absence of a `Non RVSM' corridor similar to the VFR corridor
in Los Angeles.
In response, the final rule provided for the phased implementation
of RVSM over the North Atlantic between FL 330 and FL 370 initially.
Other non-RVSM equipped aircraft are free to operate above or below the
RVSM altitudes. The FAA has determined that the benefits of the
increased efficiency within the RVSM airspace far outweigh the
inconvenience this rule may impose on a small percentage of aircraft
without the needed equipment.
Conclusion
After consideration of the comments submitted in response to the
final rule, the FAA has determined that no further rulemaking action is
necessary. Amendment 91-254 remains in effect as adopted.
Issued in Washington, DC on December 19, 1997.
Jane F. Garvey,
Administrator.
[FR Doc. 97-33753 Filed 12-24-97; 8:45 am]
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