[Federal Register Volume 61, Number 80 (Wednesday, April 24, 1996)]
[Rules and Regulations]
[Pages 18220-18223]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-10004]
[[Page 18219]]
_______________________________________________________________________
Part V
Department of Transportation
_______________________________________________________________________
Federal Aviation Administration
_______________________________________________________________________
14 CFR Part 31
Airworthiness Standards; Manned Free Balloon Burner Testing; Final Rule
Federal Register / Vol. 61, No. 80 / Wednesday, April 24, 1996 /
Rules and Regulations
[[Page 18220]]
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 31
[Docket No. 27543; Amendment No. 31-7]
RIN 2120-AE87
Airworthiness Standards; Manned Free Balloon Burner Testing
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule.
-----------------------------------------------------------------------
SUMMARY: This final rule amends the certification test requirements for
burners used on manned free balloons. The current test requirements do
not test the burner's most critical operating conditions. This
amendment will increase the current level of safety by requiring more
realistic tests and cut the fuel costs to balloon manufacturers seeking
certification.
EFFECTIVE DATE: May 24, 1996.
FOR FURTHER INFORMATION CONTACT:
J. Lowell Foster, Standards Office (ACE-110), Small Airplane
Directorate, Aircraft Certification Service, Federal Aviation
Administration, 601 East 12th Street, Kansas City, Missouri 64106;
telephone (816) 426-5688.
SUPPLEMENTARY INFORMATION:
Background
Statement of the Problem
The current burner certification requirement resembles the testing
requirement for airplane engines. Airplane engines are operated
continuously at high percentage powers, while balloon burners are
operated on an intermittent basis to maintain level or buoyant flight.
The burner requirement calls for maximum fuel flow burning over the
majority of the test time. This requirement does not reflect the fact
that a burner is continually turned on and off every few seconds or
that a minimum heat output condition is much more critical than a
maximum heat output condition. The challenging test conditions for a
burner are short blasts to maximize the thermal shock and operation on
vapor, which can result in the burner coils glowing red.
Since certification testing should simulate flight conditions and
the critical concern is not the duration of operation but the number of
mechanical and thermal cycles, this final rule would change the balloon
burner requirements to include testing of mechanical and thermal
cycles, and testing of operation on vapor. As a result, the burners
would be tested over a 40-hour period instead of 50-hour period.
The Proposal
This amendment is based on Notice of Proposed Rulemaking (NPRM),
Notice No. 93-16, which was published on December 7, 1993 (58 FR
64450). The Federal Aviation Administration (FAA) proposed to amend
Sec. 31.47(d) to remove 30 test hours at maximum heat output and
require, instead, additional testing that focuses on critical functions
experienced during flight. More specifically, the FAA proposed changes
in the balloon burner requirements to include testing of mechanical and
thermal cycles, and testing of operation on vapor. The burners would be
tested over a 40-hour period instead of 50 hours. The testing would be
for specified periods at maximum, intermediate, and minimum fuel
pressures and would include burn times of 3 to 10 seconds per minute
instead of continuous burning. The term ``intermediate fuel pressure''
would be defined as 40 to 60 percent of the range between the maximum
and minimum applicable fuel pressures in order to provide for testing
the burners near the mid-point of their ranges of operation.
The FAA also proposed to change the word ``heater'' to ``burner''
in Sec. 31.47. The industry universally uses the term ``burner,'' and
this change reflects accepted industry terminology.
Discussion of Comments
Comments to the NPRM were requested with a closing date of February
7, 1994. All comments received have been considered in adopting this
amendment.
The FAA received comments from Transport Canada, which supports the
proposal, and from two prominent balloon manufacturers. One
manufacturer agrees in general with the proposals, but offers three
suggestions that are outside the scope of this proposal. The other
recommends that the FAA adopt the British standard for Sec. 31.47. The
FAA will address these comments in the order they were submitted.
Concerning proposed Sec. 31.47(d)(1)(i), the commenter states,
``Mechanically cycling the main blast valve not only demonstrates wear
but provides the hydraulic shock necessary to adequately test the
entire fuel system. However, the on/off cycle for each system should be
different because of its thermal mass. For example, our burner has two
cast alloy base plates and thin wall Inconel vaporizing coils. Some
burners have very heavy coils and only pipe-type tubing to and from the
blast valve. A pre-test should be done to determine the widest possible
temperature swing of any of the elements that will be `in the fire' and
subject to heat-stress failures. This will provide the on/off time.''
The commenter proposes that the rule be reworded to include, ``a burn
time for each one minute cycle which has been previously established
[by a pre-test to determine the widest possible temperature change of
any of the elements, as discussed above] to provide the maximum thermal
shock to temperature effected [sic] elements, but in no case less then
four seconds.''
The FAA recognizes the merit of this comment concerning a burn time
that would provide the maximum thermal shock to temperature-affected
elements. The intent of proposed Sec. 31.47(d)(1)(i) was to allow each
applicant to pre-determine a burn time for the particular system
undergoing certification testing such that the thermal cycle used in
the testing would provide approximately the maximum difference between
the coolest and hottest temperatures the burner coils and affected
hardware would experience in service. Although the preamble to Notice
No. 93-16 did not refer specifically to testing that would achieve the
maximum temperature differential, it did emphasize the need to simulate
actual flight conditions, during which the burner is subjected to
thermal shock from its intermittent operation. Referring to the extreme
temperature change that occurs when vaporized fuel cools the entire
assembly followed by flames engulfing the vaporizing coils, the notice
stated that the critical concern was the number of mechanical and
thermal cycles.
In order to achieve the necessary thermal shock, the FAA proposed a
burn time range of from three to ten seconds for each one minute cycle
of the test. From within that time range, an applicant, through pre-
certification testing, would determine the burn time that would
maximize the temperature differential experienced by the system's
temperature-affected elements. Although Notice No. 93-16 did not
explain how the FAA arrived at the proposed 3 to 10 second range for
the burn time, that range was proposed because the FAA had learned from
previous certification testing that this time range is reasonable and
reflects the range of burn times within a one-minute cycle from which
the maximum temperature differential may be obtained.
Nevertheless, because, as pointed out by the commenter, the
requirement as proposed did not make clear that the purpose of the 3 to
10 seconds of burn
[[Page 18221]]
time was to ensure that the burner being tested is subjected to the
maximum thermal shock, the regulatory text of Sec. 31.47(d)(1)(i) is
being clarified by adding a sentence to state explicitly that
requirement. The FAA believes that the added requirement to assure that
the maximum thermal shock is achieved during testing reflects the
intent of the proposed amendment and is necessary to increase safety by
more closely simulating flight conditions. Although the commenter
suggested a minimum burn time of four seconds, based on the FAA's prior
certification experience the burn time requirement for each minute
cycle of testing remains at 3 to 10 seconds as proposed.
Referring to Sec. 31.47(d)(1)(iv), the commenter states, ``A pilot
who consistently uses incorrect fuel management techniques may get into
situations where he subjects the burner to the stress of running on
vapor. The degradation of some parts is cumulative and it would be good
to be assured that vaporizing coils, for example, would not fracture
without warning in flight.'' To achieve this goal, the commenter
recommends the FAA double the time for this test.
The FAA has determined that testing for a total of 15 minutes, as
specified in the proposal, should provide confidence that the burner
will not suffer from undue thermal stresses while not imposing an
unwarranted burden on the manufacturer. Manufacturers have told the FAA
that their balloons would not fly long on vapors before the pilot would
notice the balloon descending. The manufacturers state that the heat
output from a burner operating on vapor is not enough for the balloon
to hold altitude. Even with vapor burning constantly, the balloon will
develop an increasing rate of descent. For this reason, several
manufacturers suggested that 30 minutes was extreme and would
constitute a burden to them. The FAA could not justify, based on any
adverse service history, requiring a test of more than the originally
proposed 15 minutes total time of burner operation on vapor; therefore,
the Sec. 31.47(d)(1)(iv) will retain the 15 minute standard as
proposed.
The same commenter offers the following suggested rewrite for
Sec. 31.47(d)(1)(v): ``Fifteen hours of normal flight operation during
which backup burner and pilot lights must be extinguished and relighted
at least twice in each flight hour.'' The commenter justifies this
recommended change by explaining that backup burner and pilot lights
may be easy to relight on the ground when the burner is mounted in a
test fixture but may be difficult to relight when it is in position
during flight.
The FAA acknowledges the merits of this comment concerning backup
burners and notes that currently Sec. 31.47(e) does not specify testing
the backup burner. However, the FAA may not impose an additional burden
on the public without offering the public an opportunity to comment on
the proposed requirements. This comment addresses a matter that is
beyond the scope of the proposed rule change; therefore, it can be
considered only for future rulemaking projects. Section 31.47(d)(1)(v)
is adopted as proposed.
The commenter recommends rewording the proposal for
Sec. 31.47(d)(2) to read as follows: ``The test program for the
secondary or backup operations of the burner must include two hours of
operation of the backup burner with a continuous cycle time of five
minutes on and five minutes off. Test must include extinguishing and
relighting this burner, without the use of the pilot light system, at
least one time per 30 minutes of testing, while under a crosswind
airflow, the speed of which must be equal to the highest demonstrated
maximum sink rate for the balloon systems for which approval is being
sought.'' The commenter's explanation follows:
``The use of the backup burner in flight may include operation for
up to three or four minutes at a time. During several certification
flights, we were required to use only the backup for some flight
maneuvers. For example, on several occasions we did an entire recovery
from Maximum Sink Rate Descent and on another we did almost an entire
flight using the backup burner alone.''
``It is important to do this test with some airflow to simulate
conditions in flight should the burner have to be used during a high
speed descent. Each balloon flies at a different rate because of the
drag coefficient/gross weight, hence the air velocity requirement. In
our testing we use 1300 fpm as a descent rate maximum and if we exceed
it in our certification flights we reduce allowable Max Gross System
Weight. This figure appears in the LIMITATIONS and PERFORMANCE section
of the Aircraft Flight Manual.''
``A condition may occur in flight where the backup burner is
metered down to a low flame and is used as a pilot light system. It is
important that it be demonstrated to light without the use of pilots
[lights].''
Again, the FAA recognizes the merit of this comment concerning
backup burner flameouts and relights. Because this comment addresses a
matter that is beyond the scope of the proposed rule change, it can be
considered only for future rulemaking projects. Accordingly,
Sec. 31.47(d)(2) is adopted as proposed.
The commenter recommends adding new paragraphs (3) and (4) to
Sec. 31.47(d). The recommendation for a new Sec. 31.47(d)(3) is to
require two hours of operation of the pilot light system while under a
crosswind airflow with the wind speed equal to the highest demonstrated
maximum sink rate. The test would induce extinguishing and relighting
the pilot light at least one time per 10 minutes of testing. This test
would include testing a piezo-electric element or other electrical
means of igniting the pilot lights. Again, the commenter's reasoning is
that backup burner and pilot lights may be easy to relight on the
ground when the burner is mounted in a test fixture but may be
difficult to relight when in position during flight. Also, the
commenter believes that the piezo-electric igniters are not as reliable
in airflow as devices currently used.
This comment is also beyond the scope of the proposed rule change
and can be considered only for future rulemaking projects.
The recommendation for a new Sec. 31.47(d)(4) concerns a post-test
teardown of the burner. The commenter proposes adding the following
requirement: ``A teardown of the burner should be done to reveal any
abnormalities.'' Current Sec. 31.47(f) requires that each element of
the burner system be serviceable at the end of the test. The FAA agrees
with the commenter that a teardown inspection at the end of testing is
an acceptable procedure and a means of demonstrating compliance.
However, a teardown inspection is not an airworthiness safety standard.
The term ``serviceable,'' as used in aviation, defines a standard for
airworthiness based on certification testing of the burner and its
components.
The second commenter states that if the goal of international
harmonization is to be approached, the FAA should take into account the
British, German, and French codes in proposing changes to 14 CFR part
31. The commenter also notes that a number of balloon manufacturers and
representatives of European regulatory authorities met at London
Heathrow Airport in March 1992 to consider the member nations'
airworthiness requirements for balloons, and to make recommendations
for a future JAR 31. The commenter includes the British Civil
Airworthiness Requirements (BCAR) wording that was recommended for JAR
31.47. BCAR Sec. 31.47(d) reads as follows:
[[Page 18222]]
The heater system (including the burner unit, controls, fuel
lines, fuel cells, regulators, control valves, and other related
elements) must be substantiated by an endurance test designed to
reflect the limiting conditions likely to be encountered in service,
both in kind and duration. The endurance test proposed by the
manufacturers must be approved by the certification authority.
Though the commenter expresses the view that the version of
Sec. 31.47(d) proposed in No. 93-16 is better than the existing
version, the commenter, nevertheless, asserts that the proposed
requirement is over-specified and will soon be rendered obsolete by
technical change. The commenter further states that the proposals
leaves out some important points, but the commenter did not identify
them.
To adopt the British testing requirement would be beyond the scope
of the NPRM. The FAA does recognize the importance of harmonization and
is currently expending extensive resources to harmonize the Federal
Aviation Regulations with the European Joint Aviation requirement
(JAR). Though the requirements in BCAR Sec. 31.47(d) may accommodate
new technology more readily than those proposed in Notice 93-16, the
British rule requires the manufacturer to develop an endurance test and
have it approved by the certification authority even for current
technology. The proposed amendment of Sec. 31.47(d) provides a specific
minimum requirement for all burners to meet. If changing technology
were to render the proposed requirements obsolete for a new burner, the
FAA may apply ``special conditions'' for new and novel technology (14
CFR 21.16). Accordingly, the rule is adopted as proposed.
International Compatibility
The agency has reviewed corresponding International Civil Aviation
Organization international standards and recommended practices and
Joint Aviation Authorities requirements and has identified no
differences in these amendments and the foreign regulations.
Regulatory Evaluation Summary
Proposed changes to Federal regulations must undergo several
economic analyses. First, Executive Order 12866 directs that each
Federal agency shall propose or adopt a regulation only upon a reasoned
determination that the benefits of the intended regulation justify its
costs. Second, the Regulatory Flexibility Act of 1980 requires agencies
to analyze the economic effect of regulatory changes on small entities.
Third, the Office of Management and Budget directs agencies to assess
the effects of regulatory changes on international trade. In conducting
these analyses, the FAA has determined that this rule: (1) will
generate benefits that justify its costs; (2) is not a ``significant
regulatory action'' as defined in the Executive Order and is not
``significant'' as defined in DOT's Regulatory Policies and Procedures;
(3) will not have a significant economic impact on a substantial number
of small entities; and (4) will not constitute a barrier to
international trade. These analyses, available in the docket, are
summarized below.
Benefits and Costs
The rule will enhance safety by targeting critical functions and
conditions experienced in actual flight and will significantly reduce
certification testing costs. The current requirements call for a total
of at least 50 hours of testing, which typically consumes about 7,000
gallons of fuel per type certification. The new requirements, in
contrast, are expected to consume about 350 gallons of fuel because the
burners will be tested over a total of 40 hours instead of 50 hours and
be tested about 3 to 10 seconds per minute instead of the full 60
seconds. Applying a price of $1.20 per gallon of propane, the revised
requirements are expected to yield almost $7,800 in net cost savings
per type certification. Accordingly, the FAA finds the rule to be cost-
beneficial.
Regulatory Flexibility Determination
The Regulatory Flexibility Act (RFA) of 1980 was enacted by
Congress to ensure that small entities are not unnecessarily or
disproportionately burdened by Government regulations. The RFA requires
a Regulatory Flexibility Analysis if a rule is expected to have a
``significant (positive or negative) economic impact on a substantial
number of small entities.'' Based on the standards and thresholds
specified in FAA Order 2100.14A, Regulatory Flexibility Criteria and
Guidance, the FAA has determined that the rule will not have a
significant economic impact on a substantial number of small entities.
International Trade Impact Assessment
The rule will have little or no effect on the sale of U.S. balloons
in foreign markets and the sale of foreign balloons into the United
States.
Federalism Implications
The regulations herein will not have substantial direct effects on
the States, on the relationship between the national government and the
States, or on the distribution of power and responsibilities among the
various levels of government. Therefore, in accordance with Executive
Order 12866, it is determined that this regulation will not have
sufficient federalism implications to warrant the preparation of the
Federalism Assessment.
Conclusion
The FAA proposed to amend the airworthiness standards for testing
balloon burners because test requirements did not test the burner's
most critical operating conditions. This amendment will cut the cost to
balloon manufacturers seeking certification and increase the current
level of safety by requiring more realistic tests.
For the reasons discussed in the preamble, and based on the
findings in the Regulatory Flexibility Determination and the
International Trade Impact Analysis, the FAA has determined that this
regulation is not significant under Executive Order 12866.
In addition, the FAA certifies that this regulation will not have a
significant economic impact, positive or negative, on a substantial
number of small entities under the criteria of the Regulatory
Flexibility Act. This regulation is not considered significant under
DOT Regulatory Policies and Procedures (44 FR 11034; February 26,
1979). A regulatory evaluation of the regulation, including a
Regulatory Flexibility Determination and International Trade Impact
Analysis, has been placed in the docket. A copy may be obtained by
contacting the person identified under FOR FURTHER INFORMATION CONTACT.
List of Subjects in 14 CFR Part 31
Aircraft, Aviation safety.
The Amendment
In consideration of the foregoing, the Federal Aviation
Administration amends part 31 of the Federal Aviation Regulations (14
CFR part 31) as follows:
PART 31--AIRWORTHINESS STANDARDS: MANNED FREE BALLOONS
1. The authority citation for part 31 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701-44702, 44704.
2. Section 31.47 is amended by revising the heading and paragraphs
(a) and (d) to read as follows:
[[Page 18223]]
Sec. 31.47 Burners.
(a) If a burner is used to provide the lifting means, the system
must be designed and installed so as to create a fire hazard.
* * * * *
(d) The burner system (including the burner unit, controls, fuel
lines, fuel cells, regulators, control valves, and other related
elements) must be substantiated by an endurance test of at least 40
hours. Each element of the system must be installed and tested to
simulate actual balloon installation and use.
(1) The test program for the main blast valve operation of the
burner must include:
(i) Five hours at the maximum fuel pressure for which approval is
sought, with a burn time for each one minute cycle of three to ten
seconds. The burn time must be established so that each burner is
subjected to the maximum thermal shock for temperature affected
elements;
(ii) Seven and one-half hours at an intermediate fuel pressure,
with a burn time for each one minute cycle of three to ten seconds. An
intermediate fuel pressure is 40 to 60 percent of the range between the
maximum fuel pressure referenced in paragraph (d)(1)(i) of this section
and minimum fuel pressure referenced in paragraph (d)(1)(iii);
(iii) Six hours and fifteen minutes at the minimum fuel pressure
for which approval is sought, with a burn time for each one minute
cycle of three to ten seconds;
(iv) Fifteen minutes of operation on vapor, with a burn time for
each one minute cycle of at least 30 seconds; and
(v) Fifteen hours of normal flight operation.
(2) The test program for the secondary or backup operation of the
burner must include six hours of operation with a burn time for each
five minute cycle of one minute at an intermediate fuel pressure.
* * * * *
Issued in Washington, DC, on April 8, 1996.
David R. Hinson,
Administrator.
[FR Doc. 96-10004 Filed 4-23-96; 8:45 am]
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