Special Conditions; Twin Commander Aircraft Models 690C, 690D, 695, 695A, and 695B; Protection of Systems for High Intensity Radiated Fields (HIRF), 19257-19259 [05-7430]
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Federal Register / Vol. 70, No. 70 / Wednesday, April 13, 2005 / Rules and Regulations
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. 05–7427 Filed 4–12–05; 8:45 am]
BILLING CODE 4910–13–P
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)
Federal Aviation
Administration (FAA), DOT.
ACTION: Final special conditions; request
for comments.
AGENCY:
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,
VerDate jul<14>2003
16:30 Apr 12, 2005
Jkt 205001
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.
19257
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, § 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.
Background
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 § 21.16.
Special conditions, as appropriate, as
defined in § 11.19, are issued in
accordance with § 11.38 after public
notice and become part of the type
certification basis in accordance with
§ 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 § 21.101.
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,
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
PO 00000
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Fmt 4700
Sfmt 4700
E:\FR\FM\13APR1.SGM
13APR1
19258
Federal Register / Vol. 70, No. 70 / Wednesday, April 13, 2005 / Rules and Regulations
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,
VerDate jul<14>2003
16:30 Apr 12, 2005
Jkt 205001
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
meter)
Frequency
Peak
10 kHz–100 kHz ...............
100 kHz–500 kHz .............
500 kHz–2 MHz ................
2 MHz–30 MHz .................
30 MHz–70 MHz ...............
70 MHz–100 MHz .............
100 MHz–200 MHz ...........
200 MHz–400 MHz ...........
400 MHz–700 MHz ...........
700 MHz–1 GHz ...............
1 GHz–2 GHz ...................
2 GHz–4 GHz ...................
4 GHz–6 GHz ...................
6 GHz–8 GHz ...................
8 GHz–12 GHz .................
12 GHz–18 GHz ...............
18 GHz–40 GHz ...............
50
50
50
100
50
50
100
100
700
700
2000
3000
3000
1000
3000
2000
600
Average
50
50
50
100
50
50
100
100
50
100
200
200
200
200
300
200
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.
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Frm 00006
Fmt 4700
Sfmt 4700
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 § 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.
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Federal Register / Vol. 70, No. 70 / Wednesday, April 13, 2005 / Rules and Regulations
SUMMARY: The FAA is adopting a new
airworthiness directive (AD) for GE
CF6–45 and CF6–50 series turbofan
engines. This AD requires reviewing
accumulated cyclic-life records of 10
Citation
life-limited rotating parts, correcting
those records, and removing from
I The authority citation for these special
service parts that exceed the low-cycleconditions is as follows:
fatigue (LCF) life limits published in the
Authority: 49 U.S.C. 106(g), 40113 and
Engine Manual Chapter 5,
44701; 14 CFR 21.16 and 21.101; and 14 CFR
Airworthiness Limitations Section
11.38 and 11.19.
(ALS). This AD results from an error in
The Special Conditions
a tracking database that subtracted flight
cycles of certain serial number (SN)
I Accordingly, pursuant to the authority
parts from the actual accumulated
delegated to me by the Administrator,
cycles. We are issuing this AD to
the following special conditions are
prevent rotating parts that may have
issued as part of the type certification
exceeded their LCF life limit from
basis for the Twin Commander Aircraft
Models 690C, 690D, 695, 695A, and 695B failing, leading to uncontained engine
failure.
modified by Twin Commander Aircraft
LLC. to add a digital Air Data computer. DATES: This AD becomes effective April
1. Protection of Electrical and
28, 2005.
We must receive any comments on
Electronic Systems from High Intensity
this AD by June 13, 2005.
Radiated Fields (HIRF). Each system
that performs critical functions must be
ADDRESSES: Use one of the following
designed and installed to ensure that the addresses to comment on this AD.
• DOT Docket Web site: Go to
operations, and operational capabilities
https://dms.dot.gov and follow the
of these systems to perform critical
instructions for sending your comments
functions, are not adversely affected
electronically.
when the airplane is exposed to high
• Government-wide rulemaking Web
intensity radiated electromagnetic fields
site: Go to https://www.regulations.gov
external to the airplane.
and follow the instructions for sending
2. For the purpose of these special
your comments electronically.
conditions, the following definition
• Mail: Docket Management Facility;
applies: Critical Functions: Functions
U.S. Department of Transportation, 400
whose failure would contribute to, or
Seventh Street, SW., Nassif Building,
cause, a failure condition that would
Room PL–401, Washington, DC 20590–
prevent the continued safe flight and
001.
landing of the airplane.
• Fax: (202) 493–2251.
Issued in Kansas City, Missouri on April 1,
• Hand Delivery: Room PL–401 on
2005.
the plaza level of the Nassif Building,
David R. Showers,
400 Seventh Street, SW., Washington,
Acting Manager, Small Airplane Directorate,
DC, between 9 a.m. and 5 p.m., Monday
Aircraft Certification Service.
through Friday, except Federal holidays.
[FR Doc. 05–7430 Filed 4–12–05; 8:45 am]
FOR FURTHER INFORMATION CONTACT:
BILLING CODE 4910–13–P
Karen Curtis, Aerospace Engineer,
Engine Certification Office, FAA, Engine
and Propeller Directorate, 12 New
DEPARTMENT OF TRANSPORTATION England Executive Park, Burlington, MA
01803; telephone (781) 238–7192; fax
Federal Aviation Administration
(781) 238–7199.
SUPPLEMENTARY INFORMATION: In March
14 CFR Part 39
of 2005, GE informed us that a records
review of a certain engine revealed that
[Docket No. FAA–2005–20932; Directorate
Identifier 2005–NE–11–AD; Amendment 39– the number of cycles accumulated on
14056; AD 2005–08–04]
that engine, and its life-limited rotating
parts, were recorded incorrectly in the
RIN 2120–AA64
operator’s database in 1989. GE has
advised us that the engine and rotating
Airworthiness Directives; General
parts actually have more cycles
Electric Company (GE) CF6–45 and
accumulated than currently recorded.
CF6–50 Series Turbofan Engines
Upon further investigation, GE has
confirmed that that engine was affected
AGENCY: Federal Aviation
by an error in a tracking database that
Administration (FAA), DOT.
subtracted flight cycles from the actual
ACTION: Final rule; request for
accumulated cycles on a total of 32
comments.
rotating parts.
PART 23—AIRWORTHINESS
STANDARDS; NORMAL, UTILITY,
ACROBATIC, AND COMMUTER
CATEGORY AIRPLANES
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16:30 Apr 12, 2005
Jkt 205001
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19259
GE advises that 22 of the 32 affected
rotating parts are in the control of a
foreign operator, and under the
jurisdiction of the Direction Generale de
L’Aviation Civile (DGAC), which is the
airworthiness authority for France. The
DGAC advises that there are three of the
32 parts installed on foreign registered
airplanes, but not under the jurisdiction
of the DGAC. The location, current cycle
count, and corrected cycle count are
known for these 25 parts. None of these
25 parts have exceeded their LCF life
limit. GE advises that they do not know
the locations or current cycle counts of
the remaining seven affected rotating
parts. These seven parts could be in
service with accumulated cyclic life
exceeding their LCF life limit. We are
including the three parts mentioned
previously with the seven parts, as
being affected by this AD, to ensure
their cyclic lives get corrected. This
condition, if not corrected, could result
in failure of rotating parts that may have
exceeded their LCF life limit, leading to
uncontained engine failure.
FAA’s Determination and Requirements
of This AD
The unsafe condition described
previously is likely to exist or develop
on other GE CF6–45 and CF6–50 series
turbofan engines of the same type
design. For that reason, we are issuing
this AD to prevent rotating parts that
may have exceeded their LCF life limit,
from failing, leading to uncontained
engine failure. This AD requires:
• Reviewing the engine records
within 10 days after the effective date of
this AD, for the existence of rotating
parts listed by SN in this AD; and
• Correcting the records for those
parts; and
• Within 100 cycles-in-service after
the effective date of this AD, removing
from service those parts exceeding their
LCF life limits.
FAA’s Determination of the Effective
Date
Since an unsafe condition exists that
requires the immediate adoption of this
AD, we have found that notice and
opportunity for public comment before
issuing this AD are impracticable, and
that good cause exists for making this
amendment effective in less than 30
days.
Comments Invited
This AD is a final rule that involves
requirements affecting flight safety and
was not preceded by notice and an
opportunity for public comment;
however, we invite you to send us any
written relevant data, views, or
arguments regarding this AD. Send your
E:\FR\FM\13APR1.SGM
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]]>Agencies
[Federal Register Volume 70, Number 70 (Wednesday, April 13, 2005)]
[Rules and Regulations]
[Pages 19257-19259]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 05-7430]
-----------------------------------------------------------------------
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.
-----------------------------------------------------------------------
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
