[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
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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