[Federal Register Volume 59, Number 31 (Tuesday, February 15, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-3448]


[[Page Unknown]]

[Federal Register: February 15, 1994]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM-90; Special; Conditions No. 25-ANM-79]

 

Special Conditions; Cessna Aircraft Company, Model 560 Block 
Point Change, S.N. 560-0260 and on, Airplanes, Lightning and High-
Intensity Radiated Fields (HIRF)

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final special conditions.

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SUMMARY: These special conditions are issued for the Cessna Aircraft 
Company (Cessna), Model 560 Block Point Change, S.N. 560-0260 and on, 
airplanes. These new airplanes will utilize new avionics/electronic 
systems that perform critical or essential functions. The applicable 
regulations do not contain adequate or appropriate safety standards for 
the protection of these systems from the effects of lightning and 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 that established by the 
existing airworthiness standards.

EFFECTIVE DATES: March 17, 1994.

FOR FURTHER INFORMATION CONTACT:Mark Quam, FAA, Standardization Branch, 
ANM-13, Transport Airplane Directorate, Aircraft Certification Service, 
1601 Lind Avenue SW, Renton, Washington, 98055-4056; telephone (206) 
227-2145.

SUPPLEMENTARY INFORMATION: 

Background

    On December 2, 1992, Cessna Aircraft Company (Cessna), applied for 
an amended type certificate in the transport airplane category for the 
Model 560 Block Point Change, S.N. 560-0260 and on, airplanes. The 
Cessna Model 560 Block Point Change is a modified Cessna Model 560. The 
two Pratt and Whitney, Canada JT15D-5A engines will be replaced will be 
replaced with JT15D-5D turbo fans which will have an increase of 
approximately 5 percent thrust. One 8x7-inch primary flight instrument 
display (PFD) will be installed at each pilot's station and an 8x7-inch 
Multifunction Display (MFD) (without engine indication and crew 
alerting system (EICAS)) will be installed in the center panel as 
standard equipment. Copilot's standard instruments will be an electro-
mechanical attitude system driven by the VG-14 gyro and an electro-
mechanical horizontal situation indicator (HSI) driven by the C-14D 
gyro. An option is offered to replace these copilot instruments with a 
copilot's 8x7-inch display. A Honeywell Primus 1000, digital autopilot/
flight director system will be installed. This system will operate in 
conjunction with a suite of Collins radios (dual Com, Dual Nav, dual 
distance measuring equipment (DME), dual Mode S Transponder, and 
automatic direction finder (ADF)). Optional available avionics will be 
a second ADF, emergency locator transmitter (ELT) and cockpit voice 
recorder (CVR).
    The Cessna 560 Block Point Change will also include adhesive bonded 
cabin side stringers, rather than riveting. Other structural, thermal 
and acoustic improvements will be installed. The zero fuel weight will 
increase from 11,200 pounds (lbs.) to 11,700 lbs., the ramp weight will 
increase from 16,100 lbs. to 16,500 lbs. and the takeoff weight will 
increase from 15,900 lbs. to 16,300 lbs.

Type Certification Basis

    Under the provisions of Sec. 21.17 of the FAR, except as provided 
in Sec. 25.2, the certification basis of the Model 560 Block Point 
Change, S.N. 560-0260 and on, will include the applicable provisions of 
Part 25, as amended by Amendments 25-1 through 25-17; Secs. 25.251(e), 
25.934, and 25.1091(d)(2) as amended through Amendment 25-23; 
Sec. 25.1401 as amended through Amendment 25-27; Sec. 25.1387 as 
amended through Amendment 25-30; Secs. 25.787, 25.789, 25.791, 25.853, 
25.855, 25.857, and 25.1359 as amended through Amendment 25-32; 
Secs. 25.1303(a)(2) and 25.1385(c) as amended through Amendment 25-38; 
Sec. 25.305 as amended through Amendment 25-54; Sec. 25.1001 as amended 
through Amendment 25-57; Part 34 of the FAR; Part 36 of the FAR as 
amended by Amendments 36-1 through 36-18. Also included in the 
certification basis are Special Conditions 25-25-CE-4 and 25-ANM-21, 
and the special conditions issued herewith.
    For the Honeywell Primus 1000, compliance will be shown with the 
following regulations: Secs. 25.1301, 25-1303(b), 25.1322 as amended 
through Amendment 25-38, Secs. 25-1309, 25.25.1321 (a), (b), (d), and 
(e), 25.1331, 25.1333, and 25.1335 as amended through Amendment 25-41.
    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 Cessna Model 560 Block Point 
Change 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 Secs. 11.28 
and 11.29, and become part of the type certification basis in 
accordance with Sec. 21.17(a)(2).

Novel or Unusual Design Features

    The Model 560 Block Point Change, S.N. 560-0260 and on, 
incorporates new avionic/electronic installations, including one 8x7-
inch PFD at each pilot's station, and 8x7-inch MFD (without EICAS) in 
the center panel, an optional copilot's 8x7-inch display, a Honeywell 
Primus 1000 digital autopilot/flight director system to operate in 
conjunction with a suite of Collins radios (dual Com, Dual Nav, dual 
DME, and ADF) and optional second ADF. These systems may be vulnerable 
to lightning and high-intensity radiated fields external to the 
airplane.

Discussion

    The existing lightning protection airworthiness certification 
requirements are insufficient to provide an acceptable level of safety 
with new technology avionic systems. There are two regulations that 
specifically pertain to lightning protection: one for the airframe in 
general (Sec. 25.581), and the other for fuel system protection 
(Sec. 25.954). There are, however, no regulations that deal 
specifically with protection of electrical and electronic systems from 
lightning. The loss of a critical function of these systems due to 
lightning could prevent continued safe flight and landing of the 
airplane. Although the loss of an essential function would not prevent 
continued safe flight and landing, it could significantly impact the 
safety level of the airplane.
    There is also no specific regulation that addresses protection 
requirements for electrical and electronic systems from 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, these special 
conditions are issued for the Cessna Model 560 Block Point Change, S.N. 
560-0260 and on, which require that new technology electronic systems, 
such as the primary instrument flight displays, multifunction display, 
digital autopilot/flight director, etc., be designed and installed to 
preclude component damage and interruption of function due to both the 
direct and indirect effects of lightning and HIRF.

Lightning

    To provide a means of compliance with these special conditions, 
clarification of the threat definition of lightning is needed. The 
following ``threat definition,'' based on FAA Advisory Circular 20-136, 
Protection of Aircraft Electrical/Electronic Systems Against the 
Indirect Effects of Lightning, dated March 5, 1990, is proposed as a 
basis to use in demonstrating compliance with the lightning protection 
special condition, with the exception of the multiple burst 
environment, which has been changed to agree with the latest 
recommendation from the Society of Automotive Engineers (SAE) AE4L 
lightning committee.
    The lightning current waveforms (Components A, D, and H) defined 
below, along with the voltage waveforms in AC 20-53A, will provide a 
consistent and reasonable standard that is acceptable for use in 
evaluating the effects of lightning on the airplane. These waveforms 
depict threats that are external to the airplane. How these threats 
affect the airplane and its systems depends upon their installation 
configuration, materials, shielding, airplane geometry, etc. Therefore, 
tests (including tests on the completed airplane or an adequate 
simulation) and/or verified analyses need to be conducted in order to 
obtain the resultant internal threat to the installed systems. The 
electronic systems may then be evaluated with this internal threat in 
order to determine their susceptibility to upset and/or malfunction.
    To evaluate the induced effects to these systems, three 
considerations are required:
    1. First Return Stroke: (Severe Strike--Component A, or Restrike-
Component D). This external threat needs to be evaluated to obtain the 
resultant internal threat and to verify that the level of the induced 
currents and voltages is sufficiently below the equipment ``hardness'' 
level; then
    2. Multiple Stroke Flash: (\1/2\ Component D). A lightning strike 
is often composed of a number of successive strokes, referred to as 
multiple strokes. Although multiple strokes are not necessarily a 
salient factor in a damage assessment, they can be the primary factor 
in a system upset analysis. Multiple strokes can induce a sequence of 
transients over an extended period of time. While a single event upset 
of input/output signals may not affect system performance, multiple 
signal upsets over an extended period of time (2 seconds) may affect 
the systems under consideration. Repetitive pulse testing and/or 
analysis needs to be carried out in response to the multiple stroke 
environment to demonstrate that the system response meets the safety 
objective. This external multiple stroke environment consists of 24 
pulses and is described as a single Component A followed by 23 randomly 
spaced restrikes of \1/2\ magnitude of Component D (peak amplitude of 
50,000 amps). The 23 restrikes are distributed over a period of up to 2 
seconds according to the following constraints: (1) The minimum time 
between subsequent strokes is 10ms, and (2) the maximum time between 
subsequent strokes is 200ms. An analysis or test needs to be 
accomplished in order to obtain the resultant internal threat 
environment for the system under evaluation.
    And,
    3. Multiple Burst: (Component H). In-flight data-gathering projects 
have shown bursts of multiple, low amplitude, fast rates of rise, short 
duration pulses accompanying the airplane lightning strike process. 
While insufficient energy exists in these pulses to cause physical 
damage, it is possible that transients resulting from this environment 
may cause upset to some digital processing systems.
    The representation of this interference environment is a repetition 
of short duration, low amplitude, high peak rate of rise, double 
exponential pulses that represent the multiple bursts of current pulses 
observed in these flight data gathering projects. This component is 
intended for an analytical (or test) assessment of functional upset of 
the system. Again, it is necessary that this component be translated 
into an internal environmental threat in order to be used. This 
``Multiple Burst'' consists of repetitive Component H waveforms in 3 
sets of 20 pulses each. The minimum time between individual Component H 
pulses within a burst is 50 microseconds, the maximum is 1,000 
microseconds. The 3 bursts are distributed according to the following 
constraints: (1) The minimum period between subsequent bursts is 30ms, 
and (2) the maximum period between subsequent bursts is 300ms. The 
individual ``Multiple Burst'' Component H waveform is defined below.
    The following current waveforms constitute the ``Severe Strike'' 
(Component A), ``Restrike'' (Component D), ``Multiple Stroke'' (\1/2\ 
Component D), and the ``Multiple Burst'' (Component H).
    These components are defined by the following double exponential 
equation:

i(t) = I o (e-at -- e -bt)

    where:

t = time in seconds,
i = current in amperes, and 

                                                                                                                
                                                                             Multiple stroke                    
                                        Severe strike         Restrike       (\1/2\ component    Multiple burst 
                                        (component A)      (component D)           D)            (component H)  
----------------------------------------------------------------------------------------------------------------
Io, amp                            =        218,810            109,405             54,703             10,572    
a, sec.-1                          =         11,354             22,708             22,708            187,191    
b, sec.-1                          =        647,265          1,294,530          1,294,530         19,105,100    


                                                                                                                
This equation produces the following characteristics:                                                           
                                                                                                                
ipeak                                  =  200 KA            100 KA            50 KA             10 KA           
and,                                                                                                            
(di/dt)max (amp/sec)                   =  1.4  x  1011      1.4  x  1011      0.7  x  1011      2.0  x  1011    
                                          @t = O+sec        @t = O+sec        @t = O+sec        @t = O+sec      
di/dt, (amp/sec)                       =  1.0  x  1011      1.0  x  1011      0.5  x  1011                      
                                          @t = .5s               m>s               m>s                              
Action Integral (amp2 sec)             =  2.0  x  106       0.25  x  106      @0.625  x  106                    
                                                                                                                

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 electronic command and control of the airplane, the 
immunity of critical digital avionics systems to HIRF must be 
established.
    It is not possible to precisely define the HIRF to which the 
airplane will be exposed in service. 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. 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 10 KHz 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-70 MHz........................................       30        30
70 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-2 GHz..........................................    5,000       990
2 GHz-4 GHz..........................................    6,680       840
4 GHz-6 GHz..........................................    6,850       310
6 GHz-8 GHz..........................................    3,600       670
8 GHz-12 GHz.........................................    3,500     1,270
12 GHz-18 GHz........................................    3,500       360
18 GHz-40 GHz........................................    2,100       750
------------------------------------------------------------------------

    The envelope given in paragraph 2 above is a revision to the 
envelope used in previously issued special conditions in other 
certification projects. It is based on new data and SAE AE4R 
subcommittee recommendations. This revised envelope includes data from 
Western Europe and the U.S.

Discussion of Comments

    Notice of Proposed Special Conditions No. SC-93-6-NM for the Cessna 
Aircraft Company, Model 560 Block Point Change, S.N. 560-0260 and on, 
Airplanes, was published in the Federal Register on November 24, 1993 
(58 FR 62051). One comment was received. The commenter (Cessna Aircraft 
Company) called to our attention that the description of the avionics 
system is different than the configuration being presented for type 
certification. They stated that the standard equipment configuration 
will have an 8x7-inch PFD at each pilot's station vs the Federal 
Register publication description of two PFD's at the pilots station 
with an optional copilot PFD. This change was noted and incorporated in 
these final special conditions.

Conclusion

    This action affects only certain unusual or novel design features 
on one model of airplane. It is not a rule of general applicability and 
affects only the manufacturer who applied to the FAA for approval of 
these features on the airplane.

List of Subjects in 14 CFR Part 25

    Air transportation, Aircraft, Aviation safety, Safety.
    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, the following special conditions are issued as part of 
the type certification basis for the Cessna Aircraft Company, Model 560 
Block Point Change, S.N. 560-0260 and on, Airplanes.
    1. Lightning Protection: (a) Each new or modified 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 
airplane is exposed to lightning.
    (b) Each essential function of new or modified electronic systems 
or installations must be protected to ensure that the essential 
function can be recovered in a timely manner after the airplane has 
been exposed to lightning.
    2. Protection from Unwanted Effects of High-Intensity Radiated 
Fields (HIRF). (a) Each new or modified 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 airplane is 
exposed to high-intensity radiated fields external to the airplane.
    3. For the purpose of these special conditions, the following 
definitions apply:
    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.
    Essential Functions. Functions whose failure would contribute to or 
cause a failure condition that would significantly impact the safety of 
the airplane or the ability of the flightcrew to cope with adverse 
operating conditions.

    Issued in Renton, Washington, on January 31, 1994
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service, ANM-100.
[FR Doc. 94-3448 Filed 2-14-94; 8:45 am]
BILLING CODE 4910-13-M