[Federal Register: April 13, 2005 (Volume 70, Number 70)]
[Rules and Regulations]
[Page 19257-19259]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr13ap05-3]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 23
[Docket No. CE221, Special Condition 23-161-SC]
Special Conditions; Twin Commander Aircraft Models 690C, 690D,
695, 695A, and 695B; Protection of Systems for High Intensity Radiated
Fields (HIRF)
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final special conditions; request for comments.
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SUMMARY: These special conditions are issued to Twin Commander Aircraft
LLC. 19010 59th DR. NE. Arlington, WA. 98223 for a Supplemental Type
Certificate for the Twin Commander Aircraft Models 690C, 690D, 695,
695A, and 695B. These airplanes will have novel and unusual design
features when compared to the state of technology envisaged in the
applicable airworthiness standards. The novel and unusual design
features include the installation of dual Innovative Solutions &
Support (IS&S) Air Data Display Units (ADDU) for which the applicable
regulations do not contain adequate or appropriate airworthiness
standards for the protection of these systems from the effects of high
intensity radiated fields (HIRF). These special conditions contain the
additional safety standards that the Administrator considers necessary
to establish a level of safety equivalent to the airworthiness
standards applicable to these airplanes.
DATES: The effective date of these special conditions is April 13,
2005.
Comments must be received on or before May 13, 2005 for domestic,
August 11, 2005 for foreign.
ADDRESSES: Comments may be mailed in duplicate to: Federal Aviation
Administration, Regional Counsel, ACE-7, Attention: Rules Docket Clerk,
Docket No. CE221, Room 506, 901 Locust, Kansas City, Missouri 64106.
All comments must be marked: Docket No. CE221. Comments may be
inspected in the Rules Docket weekdays, except Federal holidays,
between 7:30 a.m. and 4 p.m.
FOR FURTHER INFORMATION CONTACT: Wes Ryan, Aerospace Engineer,
Standards Office (ACE-110), Small Airplane Directorate, Aircraft
Certification Service, Federal Aviation Administration, 901 Locust,
Room 301, Kansas City, Missouri 64106; telephone (816) 329-4127.
SUPPLEMENTARY INFORMATION: The FAA has determined that notice and
opportunity for prior public comment hereon are impracticable because
these procedures would significantly delay issuance of the approval and
thus delivery of the affected aircraft. In addition, the substance of
these special conditions has been subject to the public comment process
in several prior instances with no substantive comments received. The
FAA, therefore, finds that good cause exists for making these special
conditions effective upon issuance.
Comments Invited
Interested persons are invited to submit such written data, views,
or arguments, as they may desire. Communications should identify the
regulatory docket or notice number and be submitted in duplicate to the
address specified above. All communications received on or before the
closing date for comments will be considered by the Administrator. The
special conditions may be changed in light of the comments received.
All comments received will be available in the Rules Docket for
examination by interested persons, both before and after the closing
date for comments. A report summarizing each substantive public contact
with FAA personnel concerning this rulemaking will be filed in the
docket. Commenters wishing the FAA to acknowledge receipt of their
comments submitted in response to this notice must include a self-
addressed, stamped postcard on which the following statement is made:
``Comments to Docket No. CE221.'' The postcard will be date stamped and
returned to the commenter.
Background
On April 5, 2004, Twin Commander Aircraft LLC. 19010 59th DR NE.
Arlington, WA. 98223, made application to the FAA for a new
Supplemental Type Certificate for the Twin Commander Aircraft Models
690C, 690D, 695, 695A, and 695B. The Twin Commander Aircraft Models of
concern are approved under TCDS No. 2A4. The proposed modification
incorporates a novel or unusual design feature, a digital air data
computer, which may be vulnerable to HIRF external to the airplane.
Type Certification Basis
Under the provisions of 14 CFR part 21, Sec. 21.101, Twin
Commander Aircraft LLC. must show that the Twin Commander Aircraft
Models 690C, 690D, 695, 695A, and 695B meet the following provisions,
or the applicable regulations in effect on the date of application for
the change. For those areas modified or impacted by the installation of
the IS&S ADDU (Air Data Display Unit) system, the following paragraphs
as amended by Amendments 23-1 through 23-54 must be complied with:
23.305, 23.307, 23.365, 23.603, 23.609, 23.611, 23.613, 23.625, 23.627,
23.771, 23.773, 23.777, 23.1301, 23.1303, 23.1309, 23.1311, 23.1321,
23.1322, 23.1331, 23.1335, 23.1351, 23.1357, 23.1359, 23.1361, 23.1365,
23.1367, 23.1381, 23.1431, 23.1529, 23.1541, 23.1543, 23.1581 and the
special conditions adopted by this rulemaking action. For systems that
are not modified or impacted by the installation, the original
certification basis listed on TCDS No. 2A4 are still applicable.
Discussion
If the Administrator finds that the applicable airworthiness
standards do not contain adequate or appropriate safety standards
because of novel or unusual design features of an airplane, special
conditions are prescribed under the provisions of Sec. 21.16.
Special conditions, as appropriate, as defined in Sec. 11.19, are
issued in accordance with Sec. 11.38 after public notice and become
part of the type certification basis in accordance with Sec. 21.101.
Special conditions are initially applicable to the models for which
they are issued. Should the applicant apply for a supplemental type
certificate to modify any other model already included on the same type
certificate to incorporate the same novel or unusual design feature,
the special conditions would also apply to the other model under the
provisions of Sec. 21.101.
Novel or Unusual Design Features
Twin Commander Aircraft LLC. plans to incorporate certain novel and
unusual design features into an airplane for which the airworthiness
standards do not contain adequate or appropriate
[[Page 19258]]
safety standards for protection from the effects of HIRF. These
features include the addition of a digital Air Data computer, which may
be susceptible to the HIRF environment, that were not envisaged by the
existing regulations for this type of airplane.
Protection of Systems From High Intensity Radiated Fields (HIRF)
Recent advances in technology have given rise to the application in
aircraft designs of advanced electrical and electronic systems that
perform functions required for continued safe flight and landing. Due
to the use of sensitive solid-state advanced components in analog and
digital electronics circuits, these advanced systems are readily
responsive to the transient effects of induced electrical current and
voltage caused by the HIRF. The HIRF can degrade electronic systems
performance by damaging components or upsetting system functions.
Furthermore, the HIRF environment has undergone a transformation
that was not foreseen when the current requirements were developed.
Higher energy levels are radiated from transmitters that are used for
radar, radio, and television. Also, the number of transmitters has
increased significantly. There is also uncertainty concerning the
effectiveness of airframe shielding for HIRF. Furthermore, coupling to
cockpit-installed equipment through the cockpit window apertures is
undefined.
The combined effect of the technological advances in airplane
design and the changing environment has resulted in an increased level
of vulnerability of electrical and electronic systems required for the
continued safe flight and landing of the airplane. Effective measures
against the effects of exposure to HIRF must be provided by the design
and installation of these systems. The accepted maximum energy levels
in which civilian airplane system installations must be capable of
operating safely are based on surveys and analysis of existing radio
frequency emitters. These special conditions require that the airplane
be evaluated under these energy levels for the protection of the
electronic system and its associated wiring harness. These external
threat levels, which are lower than previous required values, are
believed to represent the worst case to which an airplane would be
exposed in the operating environment.
These special conditions require qualification of systems that
perform critical functions, as installed in aircraft, to the defined
HIRF environment in paragraph 1 or, as an option to a fixed value using
laboratory tests, in paragraph 2, as follows:
(1) The applicant may demonstrate that the operation and
operational capability of the installed electrical and electronic
systems that perform critical functions are not adversely affected when
the aircraft is exposed to the HIRF environment defined:
------------------------------------------------------------------------
Field strength
(volts per
Frequency meter)
-----------------
Peak Average
------------------------------------------------------------------------
10 kHz-100 kHz........................................ 50 50
100 kHz-500 kHz....................................... 50 50
500 kHz-2 MHz......................................... 50 50
2 MHz-30 MHz.......................................... 100 100
30 MHz-70 MHz......................................... 50 50
70 MHz-100 MHz........................................ 50 50
100 MHz-200 MHz....................................... 100 100
200 MHz-400 MHz....................................... 100 100
400 MHz-700 MHz....................................... 700 50
700 MHz-1 GHz......................................... 700 100
1 GHz-2 GHz........................................... 2000 200
2 GHz-4 GHz........................................... 3000 200
4 GHz-6 GHz........................................... 3000 200
6 GHz-8 GHz........................................... 1000 200
8 GHz-12 GHz.......................................... 3000 300
12 GHz-18 GHz......................................... 2000 200
18 GHz-40 GHz......................................... 600 200
------------------------------------------------------------------------
The field strengths are expressed in terms of peak root-mean-square
(rms) values.
or,
(2) The applicant may demonstrate by a system test and analysis
that the electrical and electronic systems that perform critical
functions can withstand a minimum threat of 100 volts per meter,
electrical field strength, from 10 kHz to 18 GHz. When using this test
to show compliance with the HIRF requirements, no credit is given for
signal attenuation due to installation.
The applicant, for approval by the FAA, to identify either
electrical or electronic systems that perform critical functions, must
perform a preliminary hazard analysis. The term ``critical'' means
those functions, whose failure would contribute to, or cause, a failure
condition that would prevent the continued safe flight and landing of
the airplane. The systems identified by the hazard analysis that
perform critical functions are candidates for the application of HIRF
requirements. A system may perform both critical and non-critical
functions. Primary electronic flight display systems, and their
associated components, perform critical functions such as attitude,
altitude, and airspeed indication. The HIRF requirements apply only to
critical functions.
Compliance with HIRF requirements may be demonstrated by tests,
analysis, models, similarity with existing systems, or any combination
of these. Service experience alone is not acceptable since normal
flight operations may not include an exposure to the HIRF environment.
Reliance on a system with similar design features for redundancy as a
means of protection against the effects of external HIRF is generally
insufficient since all elements of a redundant system are likely to be
exposed to the fields concurrently.
Applicability
As discussed above, these special conditions are applicable to the
Twin Commander Aircraft Models 690C, 690D, 695, 695A, and 695B. Should
Twin Commander Aircraft LLC. apply at a later date for a supplemental
type certificate to modify any other model on the same type certificate
to incorporate the same novel or unusual design feature, the special
conditions would apply to that model as well under the provisions of
Sec. 21.101.
Conclusion
This action affects only certain novel or unusual design features
on one model of airplane. It is not a rule of general applicability and
affects only the applicant who applied to the FAA for approval of these
features on the airplane.
The substance of these special conditions has been subjected to the
notice and comment period in several prior instances and has been
derived without substantive change from those previously issued. It is
unlikely that prior public comment would result in a significant change
from the substance contained herein. For this reason, and because a
delay would significantly affect the certification of the airplane,
which is imminent, the FAA has determined that prior public notice and
comment are unnecessary and impracticable, and good cause exists for
adopting these special conditions upon issuance. The FAA is requesting
comments to allow interested persons to submit views that may not have
been submitted in response to the prior opportunities for comment
described above.
List of Subjects in 14 CFR Part 23
Aircraft, Aviation safety, Signs and symbols.
[[Page 19259]]
PART 23--AIRWORTHINESS STANDARDS; NORMAL, UTILITY, ACROBATIC, AND
COMMUTER CATEGORY AIRPLANES
Citation
0
The authority citation for these special conditions is as follows:
Authority: 49 U.S.C. 106(g), 40113 and 44701; 14 CFR 21.16 and
21.101; and 14 CFR 11.38 and 11.19.
The Special Conditions
0
Accordingly, pursuant to the authority delegated to me by the
Administrator, the following special conditions are issued as part of
the type certification basis for the Twin Commander Aircraft Models
690C, 690D, 695, 695A, and 695B modified by Twin Commander Aircraft
LLC. to add a digital Air Data computer.
1. Protection of Electrical and Electronic Systems from High
Intensity Radiated Fields (HIRF). Each system that performs critical
functions must be designed and installed to ensure that the operations,
and operational capabilities of these systems to perform critical
functions, are not adversely affected when the airplane is exposed to
high intensity radiated electromagnetic fields external to the
airplane.
2. For the purpose of these special conditions, the following
definition applies: Critical Functions: Functions whose failure would
contribute to, or cause, a failure condition that would prevent the
continued safe flight and landing of the airplane.
Issued in Kansas City, Missouri on April 1, 2005.
David R. Showers,
Acting Manager, Small Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 05-7430 Filed 4-12-05; 8:45 am]
BILLING CODE 4910-13-P