[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]


-----------------------------------------------------------------------

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.

-----------------------------------------------------------------------

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]
BILLING CODE 4910-13-M