[Federal Register Volume 60, Number 149 (Thursday, August 3, 1995)]
[Rules and Regulations]
[Pages 39625-39627]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-19140]



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  Federal Register / Vol. 60, No. 149 / Thursday, August 3, 1995 / 
Rules and Regulations  


[[Page 39625]]


DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM-115; Special Conditions No. 25-ANM-103]


Special Conditions: Modified Learjet Model 55, 55B and 55C 
Airplanes; High Intensity Radiated Fields (HIRF)

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final special conditions; request for comments.

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

SUMMARY: These special conditions are issued for the Learjet Models 55, 
55B, and 55C airplanes modified by Duncan Aviation, Inc., of Lincoln, 
Nebraska. These models will be equipped with a Flight Visions 
Corporation, FV-2000 Head-Up Display System (HUD) that will perform 
critical functions. The applicable regulations do not contain adequate 
or appropriate safety standards for the protection of the HUD from the 
effects of high-intensity radiated fields (HIRF). These special 
conditions provide the additional safety standards that the 
Administrator considers necessary to ensure that the critical functions 
performed by this system are maintained when the airplane is exposed to 
HIRF.

DATES: The effective date of these special conditions is July 26, 1995. 
Comments must be received on or before September 18, 1995.

ADDRESSES: Comments on these final special conditions, request for 
comments, may be mailed in duplicate to: Federal Aviation 
Administration, Office of the Assistant Chief Counsel, Attn: Rules 
Docket (ANM-7) Docket No. NM-115, 1601 Lind Avenue SW., Renton, 
Washington, 98055-4056; or delivered in duplicate to the Office of the 
Assistant Chief Counsel at the above address. Comments must be marked 
``Docket No. NM-115.'' Comments may be inspected in the Rules Docket 
weekdays, except Federal holidays, between 7:30 a.m. and 4:00 p.m.

FOR FURTHER INFORMATION CONTACT:
Mark Quam, FAA, Standardization Branch, Transport Airplane Directorate, 
Aircraft Certification Service, 1601 Lind Avenue SW., Renton, 
Washington 98055-4056; telephone (206) 227-2145.

SUPPLEMENTARY INFORMATION:

Comments Invited

    The FAA has determined that good cause exists for making these 
special conditions effective upon issuance; however, interested persons 
are invited to submit such written data, views, or arguments as they 
may desire. Communications should identify the regulatory docket and 
special conditions 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. These 
special conditions may be changed in light of the comments received. 
All comments submitted 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. Persons wishing the FAA to acknowledge receipt of their 
comments submitted in response to this request must submit with those 
comments a self-addressed, stamped postcard on which the following 
statement is made: ``Comments to Docket No. NM-115.'' The postcard will 
be date stamped and returned to the commenter.

Background

    On May 2, 1995, Duncan Aviation, Inc., of Lincoln, Nebraska, 
applied for a supplemental type certificate to modify the Learjet 
Models 55, 55B, and 55C airplanes. The Learjet Model 55 series airplane 
is a business jet with two aft-mounted turbofan engines. The airplane 
can carry two pilots and 8 passengers, depending on the exit and 
interior configuration, and is capable of operating to an altitude of 
51,000 feet. The proposed modification incorporates the installation of 
a digital avionics system that will present critical functions on the 
Head-up Display System (HUD), which is potentially vulnerable to high-
intensity radiated fields (HIRF) external to the airplane.

Supplemental Type Certification Basis

    Under the provisions of Sec. 21.101 of the Federal Aviation 
Regulations (FAR) Duncan Aviation, Inc., must show that the altered 
Learjet Model 55 Series airplane continues to meet the applicable 
provisions of the regulations incorporated by reference in Type 
Certificate No. A10CE, or the applicable regulations in effect on the 
date of application for the change. The regulations incorporated by 
reference in the type certificate are commonly referred to as the 
``original type certification basis.''
    The regulations incorporated by reference in Type Certificate No. 
A10CE include the following for the Learjet Model 55, 55B and 55C 
airplanes: 14 CFR part 25, dated February 1, 1965, as amended by 25-2 
and 25-4.
    In addition, for the Models 55 and 55B: Amendments 25-3, 25-7, 25-
10, 25-12, 25-18, 25-21 and 25-30, plus Sec. 25.955(b)(2) of Amendment 
25-11; Sec. 25.954 of Amendment 25-14; Secs. 25.803(e), 25.811(f), 25-
853(a), 25.853(b), and 25-855(a) of Amendment 25-15; Sec. 25.1359 of 
Amendment 25-17; Sec. 25.785(c) of Amendment 25-20; Secs. 25.251(c), 
25.251(d), 25.251(e), 25.303, 25.305(b), 25.307(d), 25.331(a)(3), 
25.335(b), 25.335(f), 25.337(b), 25.349(b), 25.351(a), 25.363, 
25.395(a), 25.395(b), 25.471(a)(1), 25.471(a)(2), 25.473, 25.493(b), 
25.499(b), 25.499(c), 25.499(d), 25.509(a)(3), 25.561(b)(3), 25.581, 
25.607, 25.615, 25.619, 25.625, 25.629, 25.677, 25.697, 25.699, 25.701, 
25.721, 25.723, 25.725, 25.727, 25.729, 25.733, 25.735, 25.865, 25.867, 
25.871, 25.903(d), 25.934, 25.994, 25.1103(d), 25.1143(e), 25.1303, 
25.1307, 25.1331, and 25.1585(c) of Amendment 25-23; Sec. 25.1013(e), 
25.1305(c)(4), and 25.1305(c)(6) of Amendment 25-36; Secs. 25.815, 
25.1322, and 25.1403 of Amendment 25-38; Secs. 25.903(e), 25.939, and 
25.943 of Amendment 25-40, Sec. 25.255 of Amendment 25-42; Sec. 25.1326 
of Amendment 25-43; Part 36 of the FAR effective December 1, 1969, as 
amended through Amendment 36-10; Special Federal Aviation Regulation 
(SFAR) 27 effective February 1, 1974, as amended through Amendment SFAR 
27-2; and Special Conditions 25-99-CE-14.

[[Page 39626]]

    For the Model 55 configured per ECR 2377A or modified per AAK 55-
83-4: In addition to the basis listed above, Special Conditions 25-ANM-
2 dated June 24, 1983.
    For the Model 55C: Amendments 25-3, 25-7, 25-10, 25-12, 25-18, 25-
21, and 25-30; plus Sec. 25.955(b)(2) of Amend-Amendment 25-11; 
Sec. 25.954 of Amendment 25-14; Sec. Sec. 25.803(e), 25.811(f), and 
25.855(a) of Amendment 25-15; Sec. 25.1359 of Amendment 25-17; 
Sec. 25.785(c) of Amendment 25-20; Sec. Sec. 25.251(c), 25.251(c), 
25.251(e), 25.303, 25.305(b), 25.307(d), 25.331(a)(3), 25.335(b), 
25.335(f), 25.337(b), 25.349(b), 25.351(a), 25.363, 25.395(a), 
25.395(b), 25.471(a)(1), 25.471(a)(2), 25.473, 25.493(b), 25.499(b), 
25.499(c), 25.499(d), 25.509(a)(3), 25.561(b)(3), 25.581, 25.607, 
25.615, 25.619, 25.625, 25.629, 25.677, 25.697, 25.699, 25.701, 25.721, 
25.723, 25.725, 25.727, 25.729, 25.733, 25.735, 25.865, 25.867, 25.871, 
25.903(d), 25.934, 25.994, 25.1103(d), 25.1143(e), 25.1303(a)(1), 
25.1303(a)(3), 25.1303(b), 25.1303(c), 25.1307, 25.1331, and 25.1585(c) 
of Amendment 25-23; Sec. Sec. 25.1013(e), 25.1305(c)(4), and 
25.1305(c)(6) of Amendment 25-36; Sec. Sec. 25.815, 25.1303(a)(2), 
25.1322, and 25.1403 of Amendment 25-38; Sec. Sec. 25.903(e), 25.939, 
and 25.943 of Amendment 25-40; Secs. 25.255 and 25.703 of Amendment 25-
42; Sec. 24.1326 of Amendment 25-43; Sec. 25.853 of Amendment 25-51; 
Sec. 25.851 of Amendment 25-54; Part 36 of the FAR effective December 
1, 1969, as amended through Amendment 36-15; SFAR 27 effective February 
1, 1974, as amended through Amendment SFAR 27-6; Special Conditions 25-
ANM-2 dated June 24, 1983; and Special Conditions 25-99-CE-14 dated 
March 10, 1981.
    Compliance with structural provisions of Sec. 25.801(b) through (e) 
and Sec. 25.807(d) has not been shown for Models 55, 55B, and 55C.
    For Ice Protection: Sec. 25.1419. When ice protection system is 
installed per ECR 1906, Model 55, 55B, and 55C.
    For Noise Standards: Part 36 of the FAR. Compliance with Noise 
Standards, Part 36, has been established for Models 55, 55B, and 55C 
airplanes, when modified according to ECR 1511.
    For Equivalent Level of Safety: Sec. 25.201(c)(2) (except Model 
55C); Sec. 25.773(b)(2); Sec. 25.1305(r); Sec. 25.1505(b)(1) (except 
Model 55C).
    In addition, under Sec. 21.101(b)(1), the following sections of the 
FAR apply to the HUD installation: Sec. 25.1309; Sec. 25.1321(a)(b)(d), 
and (e); Sec. Sec. 25.1331, 25.1333, and 25.1335, as amended by 
Amendment 25-41. These special conditions will form an additional part 
of the supplemental type certification basis.
    If the Administrator finds that the applicable airworthiness 
regulations (i.e., part 25, as amended) do not contain adequate or 
appropriate safety standards for the Learjet Model 55 Series airplane 
because of a novel or unusual design feature, special conditions are 
prescribed under the provisions of Sec. 21.16 to establish a level of 
safety equivalent to that established in the regulations.
    Special conditions, as appropriate, are issued in accordance with 
Sec. 11.49 of the FAR after public notice, as required by 
Sec. Sec. 11.28 and 11.29, and become part of the type certification 
basis in accordance with Sec. 21.101(b)(2).
    Special conditions are initially applicable to the model for which 
they are issued. Should the applicant apply for a supplemental type 
certificate to modify any other model 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(a)(1).

Discussion

    There is no specific regulation that address protection 
requirements for electrical and electronic systems from high-intensity 
radiated fields (HIRF). Increased power levels from ground-based radio 
transmitters, and the growing use of sensitive electrical and 
electronic systems to command and control airplanes, have made it 
necessary to provide adequate protection.
    To ensure that a level of safety is achieved equivalent to that 
intended by the regulations incorporated by reference, special 
conditions are needed for the modified Learjet Model 55 Series 
airplanes that would require that the HUD be designed and installed to 
preclude component damage and interruption of function due to the 
effects of HIRF.

High-Intensity Radiated Fields (HIRF)

    With the trend toward increased power levels from ground-based 
transmitters, plus the advent of space and satellite communications, 
coupled with the electronic command and control of the airplane, the 
immunity of critical digital avionics systems, such as the Head-Up 
Display, to HIRF must be established.
    It is not possible to precisely define the HIRF to which the 
airplanes will be exposed in service. There is also uncertainty 
concerning the effectiveness of airframe shielding for HIRF. 
Furthermore, coupling of electromagnetic energy to cockpit-installed 
equipment through the cockpit window apertures is undefined. Based on 
surveys and analysis of existing HIRF emitters, an adequate level of 
protection exists when compliance with the HIRF protection special 
condition is shown with either paragraphs 1 or 2 below:
    1. A minimum threat of 100 volts per meter peak electric field 
strength from 10KHz to 18 GHz.
    a. The threat must be applied to the system elements and their 
associated wiring harnesses without the benefit of airframe shielding.
    b. Demonstration of this level of protection is established through 
system tests and analysis.
    2. A threat external to the airframe of the following field 
strengths for the frequency ranges indicated:

------------------------------------------------------------------------
                                                        Peak (V/ Average
                       Frequency                           M)     (V/M) 
------------------------------------------------------------------------
10 KHz--100 KHz.......................................       50       50
100 KHz--500 KHz......................................       60       60
500 KHz--2000 KHz.....................................       70       70
2 MHz--30 MHz.........................................      200      200
30 MHz--100 MHz.......................................       30       30
100 MHz--200 MHz......................................      150       33
200 MHz--400 MHz......................................       70       70
400 MHz--700 MHz......................................    4,020      935
700 MHz--1000 MHz.....................................    1,700      170
1 GHz-2GHz............................................    5,000      990
2 GHz-4GHz............................................    6,680      840
4 GHz-6GHz............................................    6,850      310
6 GHz-8GHz............................................    3,600      670
8 GHz-12GHz...........................................    3,500    1,270
12 GHz-18GHz..........................................    3,500      360
18 GHz-40GHz..........................................    2,100      750
------------------------------------------------------------------------

    As discussed above, these special conditions are applicable to the 
Learjet Model 55 Series airplane, modified by Duncan Aviation. Should 
Duncan Aviation apply at a later date for a supplemental type 
certificate to modify any other model included on Type Certificate No. 
A10CE 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(a)(1).

Conclusion

    This action affects only certain unusual or novel design features 
on Learjet Model 55, 55B, and 55C airplanes modified by Duncan 
Aviation. It is not a rule of general applicability and affects only 
the applicant who applied to the FAA for approval of this feature on 
these airplanes.
    The substance of these special conditions has been subjected to the 
notice and comment procedure in several prior instances and has been 
derived without substantive change from those previously issued. It is 

[[Page 39627]]
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 immediately. Therefore, these special 
conditions are being made effective 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 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

    The authority citation for these special conditions is as follows:

    Authority: 49 U.S.C. app. 1344, 1348(c), 1352, 1354(a), 1355, 
1421 through 1431, 1502, 1651(b)(2), 42 U.S.C. 1857f-10, 4321 et 
seq.; E.O. 11514; and 49 U.S.C. 106(g).

The Special Conditions

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the following special conditions are issued as part of 
the supplemental type certification basis for the Learjet Model 55, 
55B, and 55C airplanes, as modified by Duncan Aviation:
    1. Protection from Unwanted Effects of High-Intensity Radiated 
Fields (HIRF). Each electrical and electronic system that performs 
critical functions must be designed and installed to ensure that the 
operation and operational capability of these systems to perform 
critical functions are not adversely affected when the airplanes is 
exposed to high intensity radiated fields external to the airplane.
    2. The following definition applies with respect to this special 
condition: Critical Function. 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 Renton, Washington, on July 26, 1995.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service, ANM-100.
[FR Doc. 95-19140 Filed 8-2-95; 8:45 am]
BILLING CODE 4910-13-M