Special Conditions: Modified Canadair Model CL-600-1A11, -2A12, and -2B16, Series Airplanes; Lightning and High Intensity Radiated Fields (HIRF)

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM-94; Special Conditions No. 25-ANM-83]

Special Conditions: Modified Canadair Model CL-600-1A11, -2A12,

and -2B16, Series Airplanes; Lightning and High Intensity Radiated

Fields (HIRF)

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final special conditions with request for comments.

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SUMMARY: These special conditions are issued for Canadair Model CL-600-

1A11, -2A12, and -2B16 series airplanes modified by Service Corporation

International, of Houston, Texas. The modification includes the

installation of high-technology digital avionics systems or other

electronic systems that perform critical or essential functions. The

applicable type certification regulations do not contain adequate or

appropriate safety standards for the protection of these systems from

the effects of lighting and high intensity radiated fields (HIRF).

These special conditions provide the additional safety standards that

the Administrator considers necessary to ensure that the critical and

essential functions that these systems perform perform are maintained

when the airplane is exposed to lightning and HIRF.

DATES: The effective date of these special conditions is March 21,

1994. Comments must be received on or before May 13, 1994.

ADDRESSES: Comments on these special conditions may be mailed in

triplicate to: Federal Aviation Administration, Transport Airplane

Directorate (AMN-100), Attn: Docket No. NM-94, 1601 Lind Avenue SW.,

Renton, WA, 98055-4056; or delivered in triplicate to the Transport

Airplane Directorate at the above address. Comments must be marked;

Docket No. NM-94. Comments may be inspected weekdays, except Federal

holidays, between 7:30 a.m. and 4 p.m.

FOR FURTHER INFORMATION CONTACT:William Schroeder, FAA, Standardization

Branch, ANM-113, Transport Airplane Directorate, Aircraft Certification

Service, 1601 Lind Avenue SW., Renton, WA 98055-4056; telephone (206)

227-2148.

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 or

special conditions number and be submitted in triplicate 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 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 these comments a

self-addressed, stamped postcard on which the following statement is

made: ``Comments to Docket No. NM-94.'' The postcard will be date

stamped, and returned to the commenter.

Background

On November 16, 1993, Service Corporation International, 7744

Airport Boulevard, Houston, Texas 77061, applied for a supplemental

type certificate to modify Canadair Model CL-600-1A11 series airplanes.

The proposed modification includes the installation of digital

avionics, including an electronic flight instrument system (EFIS) and a

Laseref Inertial Reference System (IRS), which are vulnerable to

lightning and HIRF external to the airplane. Other similar

modifications often installed when updating the digital avionics

include attitude and heading reference systems (AHRS). Because these

are typical modernization modifications for retrofitting state-of-the-

art avionics and electronics to older type certificates, it is expected

that Service Corporation International will apply for installation of

similar modifications on Canadair Model CL-600-1A11, -2A12, and 2B16

series airplanes in the near future. Therefore, Service Corporation

International will need appropriate lightning and HIRF criteria

available for application to those projects.

Canadair Model CL-600-1A11, 2A12, and -2B16 series airplanes are

all listed on Type Certificate A21EA. The airplanes are pressurized,

have a seating capacity of 6 to 12 passengers (depending on the

specific model and airplane configuration), and are corporate transport

type airplanes that have a maximum operating altitude of 51,000 feet.

The airplanes are powered by two aft fuselage-mounted turbojet or

turbofan engines, depending on the specific model and airplane and

configuration.

Supplemental Type Certification Basis

Under the provisions of Sec. 21.101 of the FAR, Service Corporation

International, must show that the modified Canadair Model CL-600-1A11,

-2A12, and -2B16 series airplanes continue to meet the applicable

provisions of the regulations incorporated by reference in Type

Certification No. A21EA, 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 certification No.

A21EA include the following: Part 25 of the FAR, dated February 1,

1965, including Amendments 25-1 through 25-37. In addition, the

certification basis includes certain special conditions and exemptions

that are not relevant to these special conditions. These specifications

will form an additional part of the type certification basis when

critical or essential digital avionics/electronic systems are being

modified or installed by Service Corporation International.

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 Canadair Model CL-600-1A11, -2A12,

and -2B16 series airplanes 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(b), and become part of the type certification basis in

accordance with Sec. 21.101(b)(2).

Discussion

The existing lightning protection airworthiness certification

requirements are insufficient to provide an acceptable level of safety

with new-technology avionics and electronic 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 would 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 would significantly impact the

safety level of the airplane.

There is also no specific regulation that addresses protection

requirements for electrical and electronic systems for 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 Canadair Model CL-600-1A11, -2A12, and -

2B16 series airplanes that would require that new technology electrical

and electronic systems, such as electronic flight instrument systems,

and digital avionics systems 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 the lightning special

conditions, clarification of the threat definition of lightning is

needed. The following ``threat definition,'' based on FAA Advisory

Circular (AC) 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 recommendations from the Society of Automotive Engineers (SAE)

AE4L 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. The effect of these

threats on the airplane and its systems depends upon several factors,

including 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.

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

analysts need 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 10 ms, and (2) the maximum time between

subsequent strokes is 200 ms. An analysis or test needs to be

accomplished in order to obtain the resultant internal threat

environment for the system under evaluation.

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 the some digital processing systems.

The representation of this interference environment is a repetition

of low amplitude, high peak rate of rise, double exponential pulses

which 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 function 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 1000 microseconds. The 3

bursts are distributed according to the following constraints: (1) the

minimum period between bursts is 30ms, and (2) the maximum period

between 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)=Io (e-at-e-bt)

where:

t=time in seconds,

i=current in amperes, and

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Severe Multiple Multiple

strike Restrike stroke (\1/ burst

(component (component 2\ component (component

A) D) D) H)

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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=0+sec @t=0+sec @t=0+sec @t=0+sec

(di/dt), (amp/sec)................................. = 1.0 x 1011 1.0 x 1011 0.5 x 1011

@t=.52 sec)......................... = 2.0 x 106 0.25 x 106 0.0625 x 106

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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, such as the EFIS, 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 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 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.

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Peak (V/ Average

Frequency M) (V/M)

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10 KHz-100 KHz...................................... 50 50

100 KHz-500 KHz..................................... 60 60

500 KHz-2 MHz....................................... 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-1 GHz....................................... 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 1270

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. It will also be adopted by the European

Joint Aviation Authorities.

Conclusion

This action affects only certain unusual or novel design features

on the Canadair Model CL-600-1A11, -2A12, and -2B16 series airplanes.

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 Canadair Model CL-600-1A11, -2A12 and -2B16 series airplanes.

The substance of the special conditions for these airplanes 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 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 have not been submitted in

response to the prior opportunities for comment described above.

List of Subjects in 14 CFR Part 25

Aircraft, Aviation safety, Federal Aviation Administration,

Reporting and recordkeeping requirements.

The authority citation for these special conditions is as follows:

Authority: 49 U.S.C. app. 1344, 1348(c), 1352, 1345(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. 49 U.S.C. 105(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 type certification basis for Canadair Model 600-1A11, -2A12, and -

2B16 series airplanes modified by Service Corporation International of

Houston, Texas.

1. Lightning Protection

a. 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 airplane is exposed to

lightning.

b. Each electrical or electronic system that performs essential

functions must be protected to ensure that the 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)

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 airplane is exposed to

high-intensity radiated fields external to the airplane.

3. The Following Definitions Apply With Respect To These Special

Conditions

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.

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 March 21, 1994.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service, ANM-100.

[FR Doc. 94-7456 FIled 3-29-94; 8:45 am]

BILING CODE 4910-13-M