[Federal Register Volume 72, Number 85 (Thursday, May 3, 2007)]
[Notices]
[Pages 24656-24674]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E7-7302]



[[Page 24656]]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration


Airworthiness Criteria: Airship Design Criteria for Zeppelin 
Luftschifftechnik GmbH Model LZ N07 Airship

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of availability of proposed design criteria and request 
for comments

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SUMMARY: This notice announces the availability of and requests 
comments on the proposed design criteria for the Zeppelin 
Luftschifftechnik GmbH model LZ N07 airship. The German aviation 
airworthiness authority, the Luftfahrt-Bundesamt (LBA), forwarded an 
application for type validation of the Zeppelin Luftschifftechnik GmbH 
(ZLT) model LZ N07 airship on October 1, 2001. The airship will meet 
the provisions of the Federal Aviation Administration (FAA) normal 
category for airships operations and will be certificated for day and 
night visual flight rules (VFR); additionally, an operator of this 
airship may petition for exemption to operate the airship in other 
desired operations.

DATES: Comments must be received on or before June 4, 2007.

ADDRESSES: Send all comments on the proposed design criteria to: 
Federal Aviation Administration, Attention: Mr. Karl Schletzbaum, 
Project Support Office, ACE-112, 901 Locust, Kansas City, Missouri 
64106. Comments may be inspected at the above address between 7:30 a.m. 
and 4 p.m. weekdays, except Federal holidays.

FOR FURTHER INFORMATION CONTACT: Mr. Karl Schletzbaum, 816-329-4146.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to comment on the proposed design 
criteria by submitting such written data, views, or arguments as they 
may desire. Commenters should identify the proposed design criteria on 
the Zeppelin Luftschifftechnik GmbH model LZ N07 airship and submit 
comments, in duplicate, to the address specified above. All 
communications received on or before the closing date for comments will 
be considered by the Small Airplane Directorate before issuing the 
final design criteria.

Discussion

Background

    Under the provisions of the Bilateral Aviation Safety Agreement 
(BASA) between the United States and Germany, the German aviation 
airworthiness authority, the Luftfahrt-Bundesamt (LBA), forwarded an 
application for type validation of the Zeppelin Luftschifftechnik GmbH 
(ZLT) model LZ N07 airship on October 1, 2001. The LZ N07 has a rigid 
structure, 290,330 cubic foot displacement and has accommodations for 
twelve passengers and two crewmembers. The airship will meet the 
provisions of the Federal Aviation Administration (FAA) normal category 
for airships; additionally, an operator of this airship may petition 
for exemption to operate the airship in other desired operations. The 
airship will be certificated for day and night visual flight rules 
(VFR).

Proposed Design Criteria

Applicable Airworthiness Criteria Under 14 CFR Part 21

    The only applicable requirement for airship certification in the 
United States is FAA document FAA-P-8110-2, Airship Design Criteria 
(ADC). This document has been the basis of bilateral validation of 
airships between Germany and the United States for many years. However, 
in 1995, the LBA issued the initial version of the 
Luftt[uuml]chtigkeitsforderungen f[uuml]r Luftschiffe der Kategorien 
Normal und Zubringer (hereafter referred to as the LFLS), which added a 
commuter category to German airship categories and also added 
additional requirements for normal category airships. Due to this, 
where the previously mutually accepted ADC can be considered to be 
harmonized in practice, the issuance of the LFLS created regulatory 
differences for normal category airships between the United States and 
Germany.
    In keeping with its bilateral obligations, the FAA has, with 
assistance from the LBA, determined that regulatory differences exist 
between the two requirements (ADC versus LFLS). This determination is 
the Significant Regulatory Differences analysis. In the case of the LZ 
N07 airship, the German certification was accomplished to the higher 
standard of the commuter category of the LFLS, with various LBA 
modifications and additions. The FAA desires to accept the Zeppelin 
airship model LZ N07 at the same airworthiness standard as it was 
certificated to in Germany, so we have decided to accept the 
requirements of the LFLS and the supplemental requirements issued by 
the LBA as the U.S. certification basis. With this decision, the bulk 
of the regulatory differences are not relevant, as the FAA is accepting 
the provisions of the German LFLS certification in the commuter 
category in its entirety. The FAA has, after comparing the normal 
category ADC to the commuter category LFLS requirements, determined 
that all of the LFLS requirements are at least equivalent to and, in 
many cases, more conservative than the requirements for the normal 
category contained in the ADC.
Regulatory Differences
    The LFLS was developed considering the ADC at Change 1, but Change 
2 provisions were not considered. There will be one regulatory 
difference due to this; ZLT will show compliance to ADC Sec.  4.14 at 
Change 2.
Additional and Alternative Requirements
    The German aviation authority, the Luftfaht-Bundesamt (LBA) issued 
additional requirements, special conditions, and equivalent levels of 
safety to deal with certain design provisions and airworthiness 
concerns specific to the design of the LZ N07 that were not anticipated 
by the LFLS. These requirements will also become part of the U.S. 
certification basis for this airship.
    The U.S. certification basis for the LZ N07 will be proposed as an 
entire certification basis, including those changes required by the FAA 
and the LBA. Based on the provisions of 14 Code of Federal Regulations 
(CFR) part 21, Sec. Sec.  21.17(b), 21.17(c) and 21.29, the following 
airworthiness requirements were evaluated and found applicable, 
suitable, and appropriate for this design, and they will remain active 
until August 31, 2007 or to a future date extended by the FAA, and form 
the Certification Basis.
Certification Basis
    The German regulation Luftt[uuml]chtigkeitsforderungen f[uuml]r 
Luftschiffe der Kategorien Normal und Zubringer, (referred to as the 
LFLS), effective April 13, 2001; except:
    (1) In lieu of compliance to LFLS section 673 the LZ N07 will 
comply with ADC Sec.  4.14.
    (2) B-1 LBA, Equivalent Safety Finding for Section 76 LFLS, Engine 
Failure.
Discussion
    The LFLS requires that the airship restore itself to a state of 
equilibrium after the failure of any one engine during any flight 
condition. In the case of the LZ N07, a state of equilibrium using 
designated ballast cannot be achieved as required by the LFLS. ZLT

[[Page 24657]]

met this requirement with an equivalent level of safety.
    In lieu of the provisions of LFLS Sec.  76 the following is 
required:
    In the case of failure of any one engine (of three) it must be 
shown that a zero vertical speed condition can be established for any 
flight condition by using the thrust vectoring capability of the 
remaining two engines and aerodynamic lift.
    The time to achieve this zero vertical speed will be demonstrated 
to be not more than when using a designated ballast system with a 
minimum discharge rate established in LFLS Sec.  893(d).
    (3) B-2 LBA, Equivalent Safety Finding for LFLS Section 143(b), 
Controllability and Maneuverability, General [all engines out].
Discussion
    LFLS section 143(b) requires that the airship be capable of a safe 
descent and landing after failure of all engines under the conditions 
of LFLS section 561. ZLT met this requirement with an equivalent level 
of safety.
    Even in the event of all engines failing, a limited means to 
control the descent of the airship is available, but only with the 
airship in equilibrium. With the airship heavy, there is no means to 
modulate the descent once speed has dissipated, since the descent rate 
is determined by heaviness only. However, descent will be stable and no 
unsafe attitude will result and the worst-case descent rate is still in 
compliance with the emergency landing conditions of LFLS section 561. 
This fulfills the safety objective of LFLS section 143(b).
    To satisfy the provisions of LFLS section 143(b), the following is 
required:
    A qualitative safety analysis will be performed to show that the 
simultaneous occurrence of a loss of all engines (combined with worst 
case weight conditions) is extremely improbable.
    (4) B-3 LBA, Equivalent Safety Finding for LFLS Section 33(d)(2), 
Propeller Speed and Pitch Limits.
Discussion
    LFLS section 33(d)(2) requires a demonstration with the propeller 
speed control inoperative that there is a means to limit the maximum 
engine speed to 103 percent of the maximum allowable takeoff rotations 
per minute (rpm). The LZ N07 is designed so that in case of a zero 
thrust condition in flight, the affected engine is shut off. The 
shutoff rpm is above 103 percent of the maximum allowable takeoff rpm.
    The LZ N07 airship is not equipped with a traditional propeller 
governor system. The propeller speed control function is provided by 
the AIU (engine control board). If the AIU fails, a means to shut down 
the engine is provided: Called the Limiting System (Lasar). The 
limiting system provides two functional stages; the first stage limits 
rpm between 2725 and 2750, in case the AIU engine control board is 
unable to limit engine speed with the propeller in zero thrust pitch 
condition. The second stage shuts down the engine at 2900 rpm in case 
of limiting system first stage failure in order to avoid engine and 
propeller disintegration hazard to the airship. The shutdown of one 
engine is considered a major hazard. (Note: maximum rpm = 2700, 103 
percent maximum rpm = 2781.)
    In traditional governor systems during in-flight operation with 
zero thrust pitch selected, overspeed protection is not assured in case 
of a governor failure. The LZ N07 design is considered to provide 
equivalent or improved safety compared to previously certified 
(traditional) governor systems.
    To satisfy the provisions of LFLS section 33(d)(2), the following 
is required:
    The proper function of the systems will be demonstrated by 
performing a system ground test simulation.
    The propeller overspeed capability of 126 percent of the maximum 
rpm will comply with the provisions of JAR P certification, (JAR P 
section 170(a)(2)).
    (5) B-4 LBA, Equivalent Safety Finding for LFLS Section 145, 
Longitudinal Control.
Discussion
    LFLS section 145 requires a demonstration of nose-down pitch change 
out of a stabilized and trimmed climb and 30 degree pitch angle at 
maximum continuous power and a nose-up pitch change out of a stabilized 
and trimmed descent and -30 degree pitch angle at maximum continuous 
power on all engines. ZLT met this requirement with an equivalent level 
of safety. The LZ N07 ballonet system limitations prevent stabilized 
climbs or descents above certain vertical speeds. The procedure 
required in LFLS section 145 cannot be demonstrated by flight test 
without modification.
    ZLT demonstrated through flight test that sufficient control 
authority was available to recover from a steep climb or descent when 
the airship is trimmed for the appropriate climb or descent and is 
operated under maximum continuous power.
    Additionally, it was also shown that it is possible to produce a 
nose-down pitch change out of a stabilized and trimmed climbing flight 
and a nose-up pitch change out of a similar descent. The LZ N07 
ballonet systems limitations prevent this from being demonstrated at 
maximum continuous power and 30-degree pitch angle because the climb or 
descent rates are too high at the resulting airspeed.
    To satisfy the provisions of LFLS section 145 the following is 
required:
    A flight test procedure will demonstrate that it is possible to 
produce:
    (1) A nose-down pitch change out of a stabilized climb with a nose-
up flight path angle as limited by the ballonet system for the relevant 
true airspeed or 30 degrees, whichever leads to a lower absolute value.
    (2) A nose-up pitch change out of a stabilized descent with a nose-
down flight path angle as limited by the ballonet system for the 
relevant true airspeed or -30 degrees, whichever leads to a lower 
absolute value.
    (6) C-1 LBA, Additional Requirement for a Reliable Load Validation; 
14 CFR part 25, Sec.  25.301(b).
Discussion
    The present LFLS does not include the requirement for the 
manufacturer to validate the load assumptions used for stress analyses. 
14 CFR part 25, Sec.  25.301(b) requires that methods used to determine 
load intensities and distribution must be validated by flight load 
measurement unless the methods used for determining those loading 
conditions are shown to be reliable.
    The following is added as an additional requirement:
    The provisions of 14 CFR part 25, Sec.  25.301(b) will be complied 
with.
    (7) D-1 LBA, Additional Requirements for LFLS section 853(a), 
Compartment Interiors [Flammability of Seat Cushions].
Discussion
    LFLS section 853 does not provide requirements for flammability 
standards for seat cushions as introduced by Amendment 59 of 14 CFR 
part 25. The LBA requested a proof test for seat cushions with the oil 
burner as specified in 14 CFR part 25, Appendix F, part II or 
equivalent for passenger seats, except for crew seats.
    To satisfy the provisions of LFLS section 853(a), the following is 
required:
    A proof test for seat cushions with the oil burner as specified in 
14 CFR part 25, Appendix F, part II or equivalent for passenger seats 
will be performed successfully.
    (8) D-5 LBA, Additional Requirements for LFLS Section 673(d), 
Primary Flight Controls.

[[Page 24658]]

Discussion
    LFLS section 673(d) requires that airships without a direct 
mechanical linkage between the cockpit and primary flight control 
surfaces be designed with a dual redundant control system. The 
terminology ``dual redundant'' is considered ambiguous in that it does 
not clearly define the degree of redundancy required.
    To satisfy the provisions of LFLS section 853(a), the following is 
required:
    Compliance with LFLS section 1309 will show that continued safe 
flight and landing is assured after complete failure of any one of the 
primary flight control system lanes.
    (9) D-6 LBA, Equivalent Safety Finding for LFLS Section 771(c), 
Pilot Compartment [Controls Location with Respect to Propeller Hub].
Discussion
    LFLS section 771(c) requires that aerodynamic controls and pilots 
may not be situated within the trajectories of the designated propeller 
burst area. Since a thrust vectoring (including a non-swiveling lateral 
propeller) system has been incorporated into the airship, with two 
engines forward and one aft engine, formal non-compliance in some cases 
cannot be avoided.
    To satisfy the provisions of LFLS section 771(c), the following is 
required:
    A qualitative safety analysis will be accomplished that considers 
the mitigating effects of:
    (1) The relationship of overall swivel angle of propeller 
rotational plane versus crucial swivel angle of propeller rotational 
plane, (2) The distance between aft propeller and aerodynamic controls, 
and
    (3) The potential energy absorbing and deflecting structure between 
aft propulsion unit and controls and pilot.
    The analysis will consider the following:
    The lateral propeller is continuously operating in idle with the 
exception of ground maneuvering and approach phases.
    The rear propeller transitions through its crucial angle only, 
while swiveling from the horizontal to the vertical position from a 
takeoff/approach/landing/hover to a level flight configuration.
    Aircraft Flight Manual (AFM) procedures, cockpit placarding, and 
swivel lever markings shall be established to restrict normal operation 
in the crucial swivel range.
    (10) D-7 LBA, Equivalent Safety Findings for LFLS Section 777(c), 
Cockpit Controls; 1141(a), Powerplant Controls: General; 1143(c), 
Engine Controls; 1149(a)(2), Propeller Speed and Pitch Controls; 
1167(c)(1), Vectored Thrust Controls
Discussion
    LFLS section 777(c), 1141(a), 1143(c), 1149(a)(2), and 1167(c)(1) 
all involve requirements governing the configuration and 
characteristics of throttle, propeller pitch, mixture, and thrust 
vectoring controls. Due to the constant speed throttle control concept 
allowing infinitely variable thrust vector control between maximum 
reverse and maximum forward thrust, a non-conventional control system 
was developed that is partially non-compliant with the requirements. 
The requirements and the configuration of the LZ N07 are summarized in 
Table 1 below.
    To satisfy the provisions of LFLS section 777(c), 1141(a), 1143(c), 
1149(a)(2) and 1167(c)(1) the following is required:
    In the case of an identified non-compliance to the LFLS, as shown 
in Table 1, compliance will be by an evaluation of the airship and a 
finding that there are safe handling characteristics using the type 
design engine thrust control/thrust vectoring controls as described in 
Table 1.

                                                     Table 1
----------------------------------------------------------------------------------------------------------------
                                                                                      Description of equivalent
        LFLS  paragraph                Requirement        Compliant/ non-compliant     level of safety finding
----------------------------------------------------------------------------------------------------------------
777(c)........................  throttle, propeller       1. Non-compliant.         Propeller speed, thrust, and
                                 pitch, mixture                                      mixture controls are
                                 controls:                                           arranged in this order from
                                1. Order left to right..                             left to right. Propeller
                                                                                     speed and mixture are
                                                                                     grouped together forward of
                                                                                     the THRUST levers because
                                                                                     they are preset for
                                                                                     individual operating
                                                                                     conditions. The THRUST
                                                                                     levers are located
                                                                                     separately with the L/H and
                                                                                     R/H THRUST levers and
                                                                                     swivel controls grouped
                                                                                     together in order to
                                                                                     achieve convenient vector
                                                                                     operation.
                                2. arrange to prevent     2. compliant............  >Rear engine thrust control
                                 confusion.                                          set is offset to the rear
                                                                                     of the center pedestal,
                                                                                     which makes its allocation
                                                                                     to the rear engine obvious.
1141(a).......................  1. Arrangement like 777.  1. Compliant as           See 777(c) above.
                                                           described above.
                                2. markings like 1555(a)  2. compliant............  compliant.
1143(c).......................  1. Separate control of    1. Compliant............  1. Compliant
                                 engines.
                                2. simultaneous control   2. simultaneous control   2. simulteneous control of
                                 of engines.               virtually compliant.      forward engines allows for
                                                                                     symmetric thrust
                                                                                     applications, which are
                                                                                     essential for effective
                                                                                     handling of the airship.
                                                                                     The aft engine THRUST lever
                                                                                     is not located between the
                                                                                     forward THRUST levers
                                                                                     because it requires
                                                                                     individual control
                                                                                     especially during take-off,
                                                                                     hover, landing, and ground
                                                                                     maneuvering. Unintentional
                                                                                     operation of the aft engine
                                                                                     is prevented by this
                                                                                     arrangement.
1149(a)(2)....................  simultaneous speed and    Non-compliant for take-   In contrast to conventional
                                 pitch control of          off, hover, landing,      propeller controls, a
                                 propellers.               and ground maneuvering.   constant propeller pitch is
                                                                                     commanded directly by the
                                                                                     THRUST lever and propeller
                                                                                     speed is preselected by the
                                                                                     RPM lever and is
                                                                                     automatically governed by
                                                                                     means of throttle
                                                                                     variation.

[[Page 24659]]

 
                                                                                    In this operating mode, full
                                                                                     RPM is selected and pitch
                                                                                     control is commanded
                                                                                     directly from the THRUST
                                                                                     levers, which are not
                                                                                     grouped together, thus not
                                                                                     allowing simultaneous pitch
                                                                                     control. The reason for
                                                                                     this arrangement is
                                                                                     explained in issue 1143(c)
                                                                                     above. In FLIGHT
                                                                                     configuration maximum pitch
                                                                                     is preselected by the
                                                                                     THRUST levers, speed
                                                                                     control is now accomplished
                                                                                     by movement of the RPM
                                                                                     levers, which are grouped
                                                                                     together allowing
                                                                                     simultaneous speed control.
1167(c)(1)....................  Thrust vectoring:
                                1.--Independent of other  1. Compliant............  1. Compliant.
                                 controls.
                                2.--separate and          2. non compliant........  2. simultaneous vectoring
                                 simultaneous control of                             control of forward engines
                                 all propulsion units.                               allows for symmetric
                                                                                     vectoring. Asymmetric
                                                                                     control of forward swivel
                                                                                     angle is made impossible in
                                                                                     order to prevent pilot
                                                                                     confusion during vector
                                                                                     control.
                                                                                    Aft swivel adjustment is
                                                                                     limited to 0[deg] for
                                                                                     cruise and -90[deg] for T/
                                                                                     L. The aft swivel is
                                                                                     separated due to the
                                                                                     individual control
                                                                                     requirement.
----------------------------------------------------------------------------------------------------------------

    (11) D-8 LBA, Equivalent Safety Findings for LFLS Section 807(d) 
and Section 807(d)(1)(i), Emergency Exits.
Discussion
    LFLS section 807(d) and (d)(1)(i) for commuter category airships 
carrying less than 15 passengers requires at least three emergency 
exits. Refer to Table 2.

                                                     Table 2
----------------------------------------------------------------------------------------------------------------
        Category versus exits                 First exit              Second exit               Third exit
----------------------------------------------------------------------------------------------------------------
Normal Category (Less than 10          External door/ Main      One exit 19 x 26 inches  No requirement.
 passengers.).                          door: Sec.   783(a)      opposite of main door:
                                        (19 x 26 inches).        Sec.   807(a)(1).
Commuter Category (Less than 15        Main door must be floor  Same as above..........  In addition one exit 19
 passengers.).                          level: Sec.                                       x 26 required.
                                        807(d)(1).
Commuter Category Zeppelin LZ N07....  Floor level main door    Second floor level main  Not provided.
                                        much larger as 19 x 26   door much larger as 19
                                        inches.                  x 26 inches provided.
Design comprising 12 passengers......                                                    Equivalent safety
                                                                                          requested for greater
                                                                                          than 9 passengers.
----------------------------------------------------------------------------------------------------------------

    The design of the LZ N07 fully complies with the requirement for 
the Normal Category; however, the third exit required for compliance in 
the Commuter Category is not provided. This results in a formal 
noncompliance.
    To satisfy the provisions of LFLS section 807(d) and 807(d)(1)(i), 
the following is required: Compliance for LFLS section 807(d) and 
807(d)(1)(i) will be shown by:
    (1) The first and second exits provided are both floor level exits 
and oversized compared to 19 by 26 inches.
    (2) The evacuation demonstration required in section 803(e) shall 
be accomplished within 60 seconds, (with one exit blocked) instead of 
90 seconds.
    (12) D-9 LBA, Equivalent Safety Finding for Section 881(a), 
Envelope Design [Envelope Tension].
Discussion
    LFLS section 881(a) requires that the envelope maintain tension 
while supporting limit load conditions for all flight conditions. The 
rigid design of the LZ N07 allows for limited wrinkling of the envelope 
under limit load conditions with no effect on airship handling and 
performance.
    Due to the unique kind of rigid structural design, the structural 
integrity of the LZ N07 airship is not dependent on the tension of the 
envelope, as rigid structure replaces the load-carrying envelope. The 
alignment of structure, engines, empennage, cabin and other components 
affecting handling qualities, performance, and other factors is 
independent of any wrinkling condition of the envelope.
    To satisfy the provisions of LFLS section 881(a), the following is 
required:
    Safe handling characteristics will be demonstrated by flight test, 
the limit load carrying capability by analysis.
    (13) D-10 LBA, Equivalent Safety Finding for LFLS Section 881(f), 
Envelope Design [Rapid Deflation Provisions].
Discussion
    LFLS section 881(f) requires that provisions be maintained to allow 
for rapid envelope deflation of the airship should it break loose from 
the mast while moored. The present design does not include such a 
provision. For German certification, ZLT had to demonstrate an 
equivalent level of safety. As part of this, ZLT presented that, due to 
the unique kind of rigid structural design of the airship, any rapid 
deflation provision will not significantly reduce the effective cross 
section of the envelope; thus, the uncontrolled drift of the airship 
due to surface winds once free of its moorings could not be brought 
under control. ZLT presented that the overall level of safety is 
negatively affected by the potential unwanted operation of the required 
rapid deflation provision when unintentionally operated or operated due 
to individual failure conditions,

[[Page 24660]]

and that this could lead to a potentially severe failure condition.
    ZLT was required by the LBA to provide an equivalent level of 
safety by means of a qualitative safety analysis and by showing that 
the reliability of the mast coupling system design is significantly 
improved over typical non-rigid airship systems. It also provided proof 
of safe life design for the structural parts and to prove the fail-safe 
design of the hydraulically powered locking mechanism. These systems 
are part of the ground based mooring vehicle.
    We understand that the rigid structure of the airship complicates 
or eliminates the deflation design feature expected of non-rigid types 
of airships, and we believe that this requirement cannot be met without 
an equivalent level of safety. The rapid deflation feature of a non-
rigid airship is provided to allow emergency egress without the ship 
lifting and to deflate the envelope in case an airship is blown off of 
the mast and is subsequently uncontrolled. These concerns still apply 
to a rigid airship.
    We accept the evacuation procedure, described in the section 
discussion LFLS section 809(e), as an acceptable equivalent feature for 
the evacuation requirement.
    In the event that the airship is blown off of the mast, we believe 
that a rigid airship will present the same or enhanced hazard as the 
requirement for non-rigid type airships was developed to mitigate, that 
being of an unmanned and, or, uncontrolled airship in controlled 
airspace in the proximity of persons, property, or other aircraft.
    To satisfy the provisions of LFLS section 881(f), the following is 
required:
    Safe life design for the structural parts and fail-safe design of 
the hydraulically powered locking mechanism of the mooring vehicle will 
be shown.
    The Airship Flight Manual will contain mast procedures for all 
approved mast mooring conditions. These procedures will also include a 
requirement to have transponder equipment active when the airship is 
moored on the mast, and define conditions when a pilot must be in the 
airship.
    (14) D-11 LBA, Equivalent Safety Finding for LFLS Section 883(e), 
Pressure System.
Discussion
    LFLS section 883(e) requires that provisions be maintained to blow 
air into the helium space in order to prevent wrinkling of the 
envelope. The present design of the airship does not include this 
provision; therefore, ZLT had to demonstrate equivalent level of 
safety.
    Due to the unique kind of rigid structural design, the structural 
integrity of the airship is not dependent on the tension of the 
envelope. Rigid structure replaces the load-carrying envelope. The 
alignment of structure, engines, empennage, and cabin, etc., affecting 
handling qualities and airship controllability is independent of any 
wrinkling condition of the envelope.
    To satisfy the provisions of LFLS section 883(e), the following is 
required:
    Safe operation at reduced helium pressures will be demonstrated.
    (15) D-12 LBA, Interpretation of LFLS Section 785(b), Seats, berths 
and safety belts [Approval of].
Discussion
    The LFLS requires approval for seats; the LBA required approval of 
passenger and crew seats according to TSO C39b. The ZLT uses seats that 
are TSO C39b approved by a seat vendor; if this is not done, the seats 
used will demonstrate compliance to TSO C39b.
    To satisfy the provisions of LFLS section 758(b), the following is 
required:
    Seats will comply with the provisions of TSO C39b.
    (16) D-13 LBA, Additional Requirement; LFLS Section 1585(a)(10), 
Operating Procedures [Ditching, Emergency Evacuation].
Discussion
    The LFLS does not provide requirements for ditching exits; the LBA 
requested a floatation analysis to be done, to analyze the case of an 
unplanned ditching. Helium loss during the emergency evacuation 
procedure was not considered. It was determined by calculation that the 
passenger cabin provides enough buoyancy for safe egress with the 
requirement that one emergency exit shall be usable above the static 
waterline for at least 90 seconds for emergency evacuation.
    To satisfy the provisions of LFLS section 758(b), the following is 
required:
    It shall be demonstrated by test or analysis that an emergency 
evacuation exit will remain above the waterline for at least 90 seconds 
after finally settling on the water. Relevant instructions will be 
included in the Airship Flight Manual.
    (17) D-14 LBA, Interpretative Material; LFLS Section 803(e), 
Emergency Evacuation Demonstration.
Discussion
    LFLS section 803(e) requires an emergency evacuation demonstration. 
This evacuation must be completed within 90 seconds. Compliance with 
LFLS section 881(g) must be considered in conjunction with section 
803(a) through (e).
    This requirement demonstrates the ability of the entire cabin to be 
evacuated within 90 seconds using the maximum number of occupants, with 
flight crew preparation for the emergency evacuation. Normal valving of 
helium to provide emergency deflation on the ground during the 
emergency evacuation, according to section 881(g), is assumed.
    To satisfy the provisions of LFLS section 803(e), the following is 
required:
    (1) It will be demonstrated that the cabin can be emergency 
egressed within 90 seconds.
    (2) In addition, the evacuation method established will include the 
preparation of the airship for the ground phase of the emergency 
evacuation on the ground. The applicant will demonstrate by analysis 
supported by tests that the preparation for cabin emergency evacuation 
could be conducted within 30 seconds (from time of landing until start 
of cabin emergency evacuation). This technique will be published in the 
AFM. Refer to Figure 1, ``ZLT Emergency Evacuation Technique.''

[[Page 24661]]

[GRAPHIC] [TIFF OMITTED] TN03MY07.019

    (3) The evacuation method established will include four steps:
    (a) After the occurrence of the emergency situation, the pilot has 
to prepare the airship for an emergency landing.
    (b) The pilot has to land the airship.
    (c) The pilot has to prepare the airship for the evacuation. This 
includes providing enough heaviness so that the airship cannot leave 
the ground during the passenger evacuation. Also, the pilot must keep 
the airship in a safe position before starting the evacuation. By 
controlling the deflation, the pilot must try to prevent trapping of 
the envelope over the occupants during the evacuation.
    (d) The actual evacuation will only begin when a safe position of 
the airship can be maintained and when enough heaviness is provided.
    These steps will be reflected in the AFM.
    (18) D-15 LBA, Additional Requirements; 14 CFR part 23, Sec. Sec.  
23.859 and 23.1181(d), [cabin heating; fuel burner].
Discussion
    ZLT wishes to install fuel burner heating equipment for a cabin 
heating and ventilation system in the lower shell of the passenger 
cabin. The LFLS does not provide adequate requirements for the 
installation of fuel burner equipment. The LBA required the application 
of 14 CFR part 23, Sec. Sec.  23.859 and 23.1181(d), revised as of 
January 1, 1998, in addition to other applicable requirements of the 
LFLS. The LBA interpretation of Sec.  23.859 (a) is such that the 
entire heater compartment will be considered a fire region and has to 
be of fireproof construction. Part 23 Sec.  23.859, paragraphs (a)(1) 
to (a)(3), will be complied with also. Other applicable FAA regulations 
introduced by reference to Sec. Sec.  23.859 and 23.1181(d) by the LBA 
will be complied with by compliance to applicable LFLS sections.
    The airship will comply with the provisions of 14 CFR part 23, 
Sec.  23.859, Combustion Heater Fire Protection, and Sec.  23.1181(d), 
Firewalls.
    (19) E-1 LBA, Additional Requirements Remote Propeller Drive 
System.
Discussion
    The LZ N07 propellers of both forward and aft propulsion systems 
are not conventionally installed directly on the engine crankshaft. A 
remote propeller drive system consisting of torque shafts, swivel 
gears, friction clutches and a belt drive unit (on the aft engine only) 
is installed between engine and propeller to provide thrust and vector 
capability for the propellers. The LFLS does not contain requirements 
for such power transmission designs.
    The LBA required compliance as described in LBA guidance paper I-
231-87, applicable to components installed between engines and 
propellers. I-231-87(01) requires compliance with JAR 22H or 14 CFR 
part 33; however, instead of JAR 22H or 14 CFR part 33 compliance, 
compliance with applicable sections of JAR P (Change 7) as listed in 
Table 3 will be required.

                                 Table 3
               [Applicable sections of JAR P and I-231-87]
------------------------------------------------------------------------
                  Section                              Summary
------------------------------------------------------------------------
I-231-87..................................  Remote torque shafts/
                                             Fernwellen.
I-231-87(01)..............................  Alle Bauteile zwischen Motor
                                             und Propeller FAR 33.
I-231-87(02)..............................  Kr[auml]fte auf
                                             k[uuml]rzestem Weg in
                                             tragende Bauteile.
I-231-87(03)..............................  Konstruktive Ma[szlig]nahmen
                                             gegen ungleiche Dehnung.
I-231-87(04)..............................  Bei Drehgelenken
                                             ungleichf[ouml]rm.
                                             Drehbewegung meiden.
I-231-87(05)..............................  Abstand Struktur zu
                                             rotierenden Teilen >13mm.
I-231-87(06)..............................  FVB: Erweichungstemperatur
                                             TGA nicht
                                             [uuml]berschreiten.

[[Page 24662]]

 
I-231-87(07)..............................  Nicht feuersichere Wellen:
                                             Feuerschutz zum Motor.
I-231-87(08)..............................  Keine Gef[auml]hrdung durch
                                             angetr. Rest gebroch.
                                             Welle.
I-231-87(09)..............................  Unterkritischer Lauf/
                                             Kritische Drehzahl
                                             1,5*nmax.
I-231-87(10)..............................  Schwingungsversuch mit
                                             Anla[szlig]-
                                             Abstellvorg[auml]ngen.
JAR-P.....................................  Propellers: Change 7, dated
                                             22.10.87.
JAR-P01...................................  Section 1--Requirements.
JAR-P01 1A................................  SUB-SECTION A--GENERAL.
JAR-P030(a)(1)............................  Specification detailing
                                             airworthiness requirements.
JAR-P040(b)...............................  Fabrication methods.
JAR-P040(b)(1)............................  Consistently sound structure
                                             and reliable.
JAR-P040(b)(2)............................  Approved process
                                             specifications, if close
                                             control required.
JAR-P040(c)...............................  Castings.
JAR-P040(c)(1)............................  Casting technique, heat
                                             treatment, quality control.
JAR-P040(c)(2)............................  AA Approval for casting
                                             production required.
JAR-P040(e)...............................  Welded structures and welded
                                             components.
JAR-P040(e)(1)............................  Welding technique, heat
                                             treatment, quality control.
JAR-P040(e)(3)............................  Drawings annotated and with
                                             working instructions.
JAR-P040(e)(4)............................  If required, radiographic
                                             inspection, may be in
                                             steps.
JAR-P070..................................  Failure analysis.
JAR-P070(a)...............................  Failure analysis/assessment
                                             of propeller and control
                                             systems.
JAR-P070(b)(2)............................  Significant overspeed or
                                             excessive drag.
JAR-P070(c)...............................  Proof of probability of
                                             failure.
JAR-P070(e)...............................  Acceptability of failure
                                             analysis, if more on 1 of:
JAR-P070(e)(1)............................  A safe life being
                                             determined.
JAR-P070(e)(2)............................  A high level of integrity,
                                             parts to be listed.
JAR-P070(e)(3)............................  Maintenance actions,
                                             serviceable items.
JAR-P080..................................  Propeller pitch limits and
                                             settings.
JAR-P090..................................  Propeller pitch indications.
JAR-P130..................................  Identification.
JAR-P140..................................  Conditions applicable to all
                                             tests.
JAR-P140(a)...............................  Oils and lubricants.
JAR-P140(b)...............................  Adjustments.
JAR-P140(b)(1)............................  Adjustments prior to test
                                             not be altered after
                                             verification.
JAR-P140(b)(2)............................  Adjustment and settings
                                             checked/unintentional
                                             variations recorded.
JAR-P140(b)(2)(i).........................  At each strip examination.
JAR-P140(b)(2)(ii)........................  When adjustments and
                                             settings are reset.
JAR-P140(b)(3)............................  Instructions for (b)(1)
                                             proposed for Manuals.
JAR-P140(c)...............................  Repairs and replacements.
JAR-P140(d)...............................  Observations.
JAR-P150..................................  Conditions applicable to
                                             endurance tests only.
JAR-P150(a)...............................  Propeller accessories to be
                                             used during tests.
JAR-P150(b)...............................  Controls (ground and flight
                                             tests).
JAR-P150(b)(1)............................  Automatic controls provided
                                             in operation.
JAR-P150(b)(2)............................  Controls operated in
                                             accordance with
                                             instructions.
JAR-P150(b)(3)............................  Instructions provided in
                                             Manuals.
JAR-P150(c)...............................  Stops (ground tests).
JAR-P160..................................  General.
JAR-P160(b)...............................  Pass without evidence of
                                             failure or malfunction.
JAR-P160(c)...............................  Detailed inspection before
                                             and after tests complete.
JAR-P170(c)...............................  Spinner, deicing equipment,
                                             etc., subject to same test.
JAR-P190(c)...............................  Propellers fitted with
                                             spinner and fans.
JAR-P200..................................  Rig tests of propeller
                                             equipment.
JAR-P200(a)...............................  Tests for feathering, beta
                                             control, thrust reverse.
JAR-P200(b)...............................  Test to represent the amount
                                             of 1000 hour cycles.
JAR-P200(c)...............................  Evidence of similar tests
                                             may be acceptable.
JAR-P210..................................  Endurance tests.
JAR-P210(b)...............................  Variable pitch propellers.
JAR-P210(b)(1)............................  Variable pitch propellers
                                             tested to one of following:
JAR-P210(b)(1)(i).........................  A 110-hour test.
JAR-P210(b)(1)(i)(A)......................  5 hours at takeoff power.
JAR-P210(b)(1)(i)(B)......................  50 hours maximum continuous
                                             power.
JAR-P210(b)(1)(i)(C)......................  50 hours consisting of ten 5-
                                             hour cycles.
JAR-P210(b)(2)............................  At conclusion of the
                                             endurance test total
                                             cycles.
JAR-P210(b)(2)(ii)........................  Governing propellers: 1500
                                             cycles of control.
JAR-P210(b)(2)(iv)........................  Reversible-pitch propellers:
                                             200 cycles + 30 seconds.
JAR-P220..................................  Functional tests not less 50
                                             in flight.
JAR-P220(b)...............................  Variable pitch (governing)
                                             propellers.
JAR-P220(b)(1)............................  Propeller governing system
                                             compatible w. engine.
JAR-P220(b)(2)............................  Stability of governing under
                                             various oil temperatures
                                             conditions.
JAR-P220(b)(3)............................  Response to rapid throttle
                                             movements, balked landing.
JAR-P220(b)(4)............................  Governing and feathering at
                                             all speeds up to VNE.

[[Page 24663]]

 
JAR-P220(b)(5)............................  Unfeathering, especially
                                             after cold soak.
JAR-P220(b)(6)............................  Beta control response and
                                             sensitivity.
JAR-P220(b)(7)............................  Correct operation of stops
                                             and warning lights.
JAR-P220(c)...............................  Propeller design for
                                             operation in reverse pitch
                                             50 landing.
------------------------------------------------------------------------

    To satisfy the additional required provisions, the following is 
required:
    Compliance will be shown for the Remote Propeller Drive System to 
the requirements of LBA document I-237-87, dated September 1987, and 
the Joint Aviation Requirements (JARs) summarized in Table 3.

                                 Table 3
                               [Repeated]
------------------------------------------------------------------------
                  Section                              Summary
------------------------------------------------------------------------
I-231-87..................................  Remote torque shafts/
                                             Fernwellen.
I-231-87(01)..............................  Alle Bauteile zwischen Motor
                                             und Propeller FAR 33.
I-231-87(02)..............................  Kr[auml]fte auf
                                             k[beta]rzestem Weg in
                                             tragende Bauteile.
I-231-87(03)..............................  Konstruktive Ma[szlig]nahmen
                                             gegen ungleiche Dehnung.
I-231-87(04)..............................  Bei Drehgelenken
                                             ungleichf[ouml]rm.
                                             Drehbewegung meiden.
I-231-87(05)..............................  Abstand Struktur zu
                                             rotierenden Teilen >13mm.
I-231-87(06)..............................  FVB: Erweichungstemperatur
                                             TGA nicht
                                             [uuml]berschreiten.
I-231-87(07)..............................  Nicht feuersichere Wellen:
                                             Feuerschutz zum Motor.
I-231-87(08)..............................  Keine Gef[auml]hrdung durch
                                             angetr. Rest gebroch.
                                             Welle.
I-231-87(09)..............................  Unterkritischer Lauf/
                                             Kritische Drehzahl
                                             1,5*nmax.
I-231-87(10)..............................  Schwingungsversuch mit
                                             Anla[beta]-
                                             Abstellvorg[auml]ngen.
JAR-P.....................................  Propellers Change 7, dated
                                             22.10.87.
JAR-P01...................................  Section 1--Requirements.
JAR-P01 1A................................  SUB-SECTION A--GENERAL.
JAR-P030(a)(1)............................  Specification detailing
                                             airworthiness requirements.
JAR-P040(b)...............................  Fabrication Methods.
JAR-P040(b)(1)............................  Consistently sound structure
                                             and reliable.
JAR-P040(b)(2)............................  Approved process
                                             specification, if close
                                             control required.
JAR-P040(c)...............................  Castings.
JAR-P040(c)(1)............................  Casting technique, heat
                                             treatment, quality control.
JAR-P040(c)(2)............................  AA Approval for casting
                                             production required.
JAR-P040(e)...............................  Welded Structures and Welded
                                             Components.
JAR-P040(e)(1)............................  Welding technique, heat
                                             treatment, quality control.
JAR-P040(e)(3)............................  Drawings annotated and with
                                             working instructions.
JAR-P040(e)(4)............................  If required, radiographic
                                             inspection, may be in
                                             steps.
JAR-P070..................................  Failure Analysis.
JAR-P070(a)...............................  Failure analysis/assessment
                                             propeller/control system.
JAR-P070(b)(2)............................  Significant overspeed or
                                             excessive drag.
JAR-P070(c)...............................  Proof of probability of
                                             failure.
JAR-P070(e)...............................  Acceptability of failure
                                             analysis, if more on 1 of:
JAR-P070(e)(1)............................  A safe life being
                                             determined.
JAR-P070(e)(2)............................  A high level of integrity,
                                             parts to be listed.
JAR-P070(e)(3)............................  Maintenance actions,
                                             serviceable items.
JAR-P080..................................  Propeller Pitch Limits and
                                             Settings.
JAR-P090..................................  Propeller Pitch Indications.
JAR-P130..................................  Identification.
JAR-P140..................................  Conditions Applicable to All
                                             Tests.
JAR-P140(a)...............................  Oils and Lubricants.
JAR-P140(b)...............................  Adjustments.
JAR-P140(b)(1)............................  Adjustment prior to test not
                                             be altered after
                                             verification.
JAR-P140(b)(2)............................  Adjustment and settings
                                             checked/unintentional
                                             variations recorded.
JAR-P140(b)(2)(i).........................  At each strip examination.
JAR-P140(b)(2)(ii)........................  When adjustments and
                                             settings are reset.
JAR-P140(b)(3)............................  Instructions for (b)(1)
                                             proposed for Manuals.
JAR-P140(c)...............................  Repairs and Replacements.
JAR-P140(d)...............................  Observations.
JAR-P150..................................  Conditions Applicable to
                                             Endurance Tests Only.
JAR-P150(a)...............................  Propeller accessories to be
                                             used during tests.
JAR-P150(b)...............................  Controls (Ground and Flight
                                             Tests).
JAR-P150(b)(1)............................  Automatic controls provided
                                             in operation.
JAR-P150(b)(2)............................  Controls operated in
                                             accordance with
                                             instructions.
JAR-P150(b)(3)............................  Instructions provided in
                                             Manuals.
JAR-P150(c)...............................  Stops (Ground Tests).
JAR-P160..................................  General.

[[Page 24664]]

 
JAR-P160(b)...............................  Pass without evidence of
                                             failure or malfunction.
JAR-P160(c)...............................  Detailed inspection before
                                             and after tests complete.
JAR-P170(c)...............................  Spinner, deicing equipment,
                                             etc., subject to same test.
JAR-P190(c)...............................  Propellers Fitted with
                                             Spinner and Fans.
JAR-P200..................................  Rig Tests of Propeller
                                             Equipment.
JAR-P200(a)...............................  Tests for feathering, Beta
                                             Control, thrust reverse.
JAR-P200(b)...............................  Test to represent the amount
                                             of 1000 h cycles.
JAR-P200(c)...............................  Evidence of similar tests
                                             may be acceptable.
JAR-P210..................................  Endurance Tests.
JAR-P210(b)...............................  Variable Pitch Propellers.
JAR-P210(b)(1)............................  Variable Pitch Propellers
                                             tested to one of following:
JAR-P210(b)(1)(i).........................  A 110-Hour Test.
JAR-P210(b)(1)(i)(A)......................  5 hours at Takeoff Power.
JAR-P210(b)(1)(i)(B)......................  50 hours Maximum Continuous
                                             Power.
JAR-P210(b)(1)(i)(C)......................  50 hours consisting of ten 5-
                                             hour cycles.
JAR-P210(b)(2)............................  At conclusion of the
                                             Endurance Test total
                                             cycles.
JAR-P210(b)(2)(ii)........................  Governing Propellers: 1500
                                             cycles of control.
JAR-P210(b)(2)(iv)........................  Reversible-pitch Propellers:
                                             200 cycles + 30 sec.
JAR-P220..................................  Functional Tests not less 50
                                             in flight.
JAR-P220(b)...............................  Variable Pitch (Governing)
                                             Propellers.
JAR-P220(b)(1)............................  Propeller governing system
                                             compatible with engine.
JAR-P220(b)(2)............................  Stability of governing under
                                             various oil temperature
                                             conditions.
JAR-P220(b)(3)............................  Response to rapid throttle
                                             movements, balked landing.
JAR-P220(b)(4)............................  Governing and feathering at
                                             all speeds up to VNE.
JAR-P220(b)(5)............................  Unfeathering, especially
                                             after cold soak.
JAR-P220(b)(6)............................  Beta control response and
                                             sensitivity.
JAR-P220(b)(7)............................  Correct operation of stops
                                             and warning lights.
JAR-P220(c)...............................  Propeller Design for
                                             Operation in Reverse Pitch
                                             50 landing.
------------------------------------------------------------------------

LBA Document I-237-87

Preliminary Guideline for Compliance of Transmission-Shafts in 
Powerplant Installations of Airplanes (part 23) and Powered 
Sailplanes (JAR 22)

LBA Document: I231-87

Issue: 30. September 1987

Change record: Translated into English, May 2002

    Translation has been done by best knowledge and judgement. In 
any case, the officially published text in German language is 
authoritative.
    At the present time the Airworthiness Requirements for motorized 
aircraft assume only propeller-engine-combinations, where the 
propeller is directly fixed at the engine flange.
    Clutches, transmission shafts, intermediate bearings, angular 
drives (gearboxes), universal joints, shifting sleeves, etc., are 
accommodated for neither by JAR-22, nor by part 23 (JAR-23), or part 
33 (JAR-E).
    The necessity to supplement/amend the Airworthiness Requirements 
became obvious for a powered sailplane, where a transmission shaft 
from the engine in the middle of the fuselage runs through the 
cockpit between the pilots (side-by-side seats) to the bow of the 
fuselage where the propeller is mounted.
    The rupture of a so installed transmission shaft can, besides 
the loss of thrust, also by the whirling of the parts that remain 
attached to the run-away engine have catastrophic effects to pilots 
and aircrafts/aeroplanes.
    Also differently arranged transmission shafts that do not pass 
through the cockpit can endanger the surrounding primary structure, 
the controls or other important systems critically.
    For transmission shaft installations the following Special 
Requirements have to be applied for powered sailplanes and aircraft 
(aeroplanes) in addition to JAR 22 and part 23 (JAR 23), 
respectively part 33 (JAR-E):
    (1) All parts between engine and propeller, that serve the 
transfer of engine-power to the propeller are regarded as parts of 
the engine and are, as far as practicable/applicable, to be shown to 
comply with JAR-22 Subpart H Engines or part 33 Aircraft Engines 
(JAR-E), respectively.
    (2) Propeller thrust, lateral loads and gyroscopic moments have 
to be transferred to load carrying members on the shortest possible 
way.
    (3) Dissimilar expansion/deformation between structural and 
powerplant parts, may it be under loads or/and temperatures has to 
be accounted for by appropriate means.
    (4) Universal joints used in the transmission shaft installation 
have to be selected and arranged/installed so that an unsteadiness 
of the rotation speed is avoided.
    (5) Wrappings, guidances, protective covers and all other 
structural members must have such a spacing from rotating parts, 
that under deformation due to flight or ground loads and if pressure 
is exerted by parts of the body (pilot or passenger) a radial or 
respectively longitudinal distance of at least 13 mm (0.5 inch) 
remains.
    (6) It has to be guaranteed that parts made of fibre-reinforced 
materials during operation do not exceed (reach) the softening 
temperature. Softening temperature: TGA according to DIN 29971. 
Compliance has to be sought in a ``cooling test flight'' according 
to JAR 22.1041/22.1047 or part 23, Sec. Sec.  23.1041/23.1045/
23.1047 (or JAR 23 * * *), respectively.
    If the difference between the corrected maximum operational 
temperature and the softening temperature is less than 15 [deg]C, 
the operational temperature has to be monitored (continuously) by an 
instrument.
    (7) If parts of the transmission shaft installation are made 
from material not being fireproof, these parts have to be protected 
against the effects of fire in the engine compartment.
    (8) It has to be shown, that the whirling rest of a broken 
transmission shaft, still driven by the engine does neither directly 
endanger occupants (pilots included) nor parts of the primary 
structure in a way that the flight cannot be brought to a safe end. 
Compliance has to be sought in a test under the assumption that the 
shaft is broken at a place most critical for compliance and the 
engine running at take-off power.
    (9) The repeated in-flight-stopping and re-starting of the 
engine is common practice for powered sailplane. To avoid passing 
through a critical RPM-range, transmission shaft installation must 
operate in a sub-critical RPM-range.
    The critical RPM of any transmission shaft must be at least 1.5 
times the maximum operational RPM. When determining the critical RPM 
the influences of the maximum imbalance to be expected from the 
manufacturing process, as well as the bending of the shaft under 
load factor and probable forced bending by fuselage deformation has 
to be considered.

[[Page 24665]]

    (10) The vibration test required by JAR 22.1843 or FAR 
33.43(a)(b)/(JAR-E) respectively must comprise the complete 
transmission shaft installation (engine-transmission-shaft-
propeller). The effects of engine stopping and restarting must be 
investigated.
    The stresses derived from the test above have to be superimposed 
with the stresses directly originating from load factors acting on 
the transmission shaft or are forced on the transmission shaft by 
deformation of the airframe.
    The resulting peak stresses must not exceed the fatigue limit of 
the material used for the transmission shaft installation.

Figure 2: LBA Document

    (20) E-2 LBA, Equivalent Safety Finding; LFLS Section 1167(d), 
Vectored Thrust Components [Auxiliary Thrust Vectoring].
Discussion
    LFLS section 1167(d) (subpart E) requires an auxiliary means be 
provided to return the vectoring thrust system into a normal operating 
position should the primary means fail. The current design does not 
include this design feature. The LZ N07 is equipped with a system of 
swiveling propellers. This system is used for conventional cruise 
flight with the propellers in a vertical position and also for steering 
the airship at low airspeeds with the propellers in swiveled positions. 
This results in no one ``normal position'' of the propeller than can be 
specified. Even if the propeller swiveling system fails, such a stuck 
position might be useful for the pilot. Also, since all three engines 
are operating individually, a single vectoring failure does not 
interfere with the two remaining propulsion units.
    Instead of providing auxiliary means to return the system to the 
normal operating position, the design, operation, and function of the 
vectoring system on the Zeppelin LZ N07 airship provides an equivalent 
level of safety.
    To satisfy the provisions of LFLS section 1167(d), the following is 
required:
    It will be shown by flight test that continued safe flight and 
landing is possible with a propeller stuck in any one position with the 
affected engine (still) running or shut off.
    (21) F-1 LBA, Additional Requirements; LFLS Section 1301, Function 
and Installation; and LFLS Section 1309, Equipment, Systems and 
Installations (HIRF)
Discussion
    The LZ N07 utilizes new avionics/electronic systems that provide 
critical data to the flight crew. The applicable regulations do not 
contain adequate or appropriate safety standards for the protection of 
these systems from the effects of high intensity radiated fields 
(HIRF). The LBA's required additional safety standards considered 
necessary to establish a level of safety equivalent to that established 
by existing airworthiness standards.
    There is no specific regulation that addresses protection 
requirements for electrical and electronic systems from HIRF. Increased 
power levels from the ground based radio transmitters and the growing 
use of sensitive electrical and electronic systems to command and 
control the airship, especially under IFR conditions, have made it 
necessary to provide adequate protection. To ensure that the level of 
safety is achieved equivalent to that intended by the regulations 
incorporated by reference, additional requirements are needed for the 
LZ N07 to require that new technology electrical and electronic systems 
be designed and installed to preclude component damage and interruption 
of critical functions due to effect 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 electrical and electronic command and control of an 
airship, the immunity of critical systems to HIRF must be established. 
It is not possible to precisely define the HIRF to which the airship 
will be exposed in service. There is also uncertainty concerning the 
effectiveness of gondola shielding for HIRF. Furthermore, coupling of 
electromagnetic energy to gondola-installed equipment through the 
windows apertures is undefined. Based on surveys and analysis of 
existing HIRF emitters, an adequate level of protection exists when 
compliance with the HIRF special condition is shown.
    To satisfy the provisions of LFLS section1301 and LFLS section 1309 
the following is required:
    The airship systems and associated components, considered 
separately and in relation to other systems, must be designed and 
installed so that:
    (a) Each system that performs a critical or essential function is 
not adversely affected when the airship is exposed to the normal HIRF 
environment.
    (b) All critical functions must not be adversely affected when the 
airship is exposed to the certification HIRF environment.
    (c) After the airship is exposed to the certification HIRF 
environment, each affected system that performs a critical function 
recovers normal operation without requiring any crew action, unless 
this conflicts with other operational or functional requirements of 
that system.
    The following definitions apply:
    (a) Critical function: A function whose failure would prevent 
continued safe flight and landing of the airship.
    (b) Essential function: A function whose failure would reduce the 
capability of the airship or the ability of the crew to cope with 
adverse operating conditions.
    (c) The definitions of normal and certification HIRF environments, 
frequency bands, and corresponding average and peak levels are defined 
in Table 4 and Table 5.

General Guidance Material

    The User Guide for AC/AMJ 20-1317 The Certification of Aircraft 
Electrical and Electronical Systems for Operation in the High Radiated 
Fields (HIRF) Environment dated 9/21/98 must be used. In case of 
conflicting issues, this notice will supersede, unless otherwise 
notified.

Criticality Definitions

    In order to perform hazard assessments, the table below defines 
equivalence:

                                 Table 4
------------------------------------------------------------------------
                            Guidance according to    LFLS certification
  Definition CRI F-1/HIRF      AC/AMJ  20-1317             basis*
------------------------------------------------------------------------
Critical..................  Catastrophic.........  Multiple failure
                                                    analysis will not
                                                    apply in general.
Essential.................  Hazardous............  Multiple failure
                            Severe...............   analysis will not
                            Major................   apply in general.
------------------------------------------------------------------------
* Since the LFLS is based on 14 CFR part 23, multiple failure analysis
  will not apply in general. However, common mode failures, or failures
  if one failure would lead inevitably to another failure, have to be
  considered.


[[Page 24666]]

Equipment Test Requirements

    If ZLT can demonstrate for Level A, B, or C equipment that 
equipment testing is adequate for showing compliance, the following 
equipment test requirement will be used:
    RTCA DO-160 D, if equipment development was launched in 1996 or 
later a no TSO or JTSO certification will be obtained by the supplier.
    RTCA DO-160 C, or earlier if equipment development was launched in 
1995 or earlier, or if the equipment affected already holds a separate 
TSO or JZSO certification.

                                 Table 5
------------------------------------------------------------------------
                     Frequency                         Peak     Average
------------------------------------------------------------------------
10 kHz-100 kHz....................................         40         40
100 kHz-500 kHz...................................         40         40
500 kHz-2 MHz.....................................         40         40
2 MHz-30 MHz......................................        100        100
30 MHz-70 MHz.....................................         20         20
70 MHz-100 MHz....................................         20         20
100 MHz-200 MHz...................................         50         30
200 MHz-400 MHz...................................         70         70
400 MHz-700 MHz...................................        730         30
700 MHz-1 GHz.....................................       1300         70
1 GHz-2 GHz.......................................       2500        160
2 GHz-4 GHz.......................................       3500        240
4 GHz-6 GHz.......................................       3200        280
6 GHz-8 GHz.......................................        800        330
8 GHz-12 GHz......................................       3500        330
12 GHz-18 GHz.....................................       1700        180
------------------------------------------------------------------------

Certification HIRF Environment
    Field Strengths in Volts/Meter, (V/m).

    Note: At 10 kHz-100kHz a Height Impedance Field of 320V/m peak 
exists.


                                 Table 6
------------------------------------------------------------------------
                     Frequency                         Peak     Average
------------------------------------------------------------------------
10 kHz-100 kHz....................................         20         20
100 kHz-500 kHz...................................         20         20
500 kHz-2 MHz.....................................         30         30
2 MHz-30 MHz......................................         50         50
30 MHz-70 MHz.....................................         10         10
70 MHz-100 MHz....................................         10         10
100 MHz-200 MHz...................................         30         30
200 MHz-400 MHz...................................         25         25
400 MHz-700 MHz...................................        730         30
700 MHz-1 GHz.....................................         40         10
1 GHz-2 GHz.......................................       1700        160
2 GHz-4 GHz.......................................       3000        170
4 GHz-6 GHz.......................................       2300        280
6 GHz-8 GHz.......................................        530        230
------------------------------------------------------------------------

Normal HIRF Environment
    Field Strengths in Volts/Meter, (V/m).

Abbreviations

GHz--Gigahertz
IFR--Instrument Flight Rules
kHz--Kilohertz
m--Meter
MHz--Megahertz
V--Volt
    (22) F-2 LBA, Additional Requirements; LFLS Section 1301, Function 
and Installation, and LFLS Section 1309, Equipment, Systems and 
Installations [Software development and transition to RTCA DO-178B/ED-
12B]
Discussion
    The LZ N07 will be certificated with microprocessor-based systems 
installed that contain software. The LBA considered that there was 
limited policy or guidance for transitioning to the use of RTCA DO 
178B/ED-12B from earlier guidance regarding means of compliance for 
software-based systems. Specific transition criteria were specified for 
the LZ N07 compliance program.
    RTCA DO 178B/ED-12B, ``Software Considerations in Airborne Systems 
and Equipment Certification,'' dated December 1, 1992, provides 
guidance for software development where industry and regulatory 
experience showed RTCA document DO 178A/ED-12A, ``Software 
Considerations in Airborne Systems and Equipment Certification,'' dated 
1985, required revision. Through RTCA, Inc./EUROCAE, a joint committee 
comprised of representatives from both the public and private sectors, 
created DO 178B/ED-12B to reflect the experience gained in the 
certification of aircraft and engines containing software based systems 
and equipment and to provide guidance in the area not previously 
addressed by DO 178A/ED-12A. DO 178B/ED-12B contains more objectively-
determinable compliance criteria and considerably enhances the 
consistency of software evaluations. The use of DO 178B/ED-12B provides 
for a more thorough and sure compliance finding to objective standards, 
reducing the likelihood of software errors.
    Due to being superseded for the reasons discussed above, DO 178A/
ED-12A and prior versions were not recognized by the LBA as acceptable 
means of compliance for software being developed or being modified for 
an airship certification program (in Germany) whose application date 
was later than January 11, 1993 (except as noted in subparagraph 1(a) 
and 1(b) below). The LZ N07 program fell into this category. ZLT was 
allowed to propose exceptions to the use of DO 178B/ED-12B (or 
equivalently acceptable means of compliance) for specific systems or 
equipment. These requests were evaluated on a case-by-case basis and 
were considered when:
    (a) The LBA determined that the software modification is so simple 
or straightforward that an upgrade of the applicant's processes to DO 
178B/ED-12B from earlier revisions of DO 178/ED-12 is not necessary for 
assuring that the modification is specified, designed, and implemented 
correctly, and verified appropriately; or
    (b) Where a straightforward and readily obvious determination could 
be made by the LBA that airworthiness will not be affected if some 
specific objectives of DO 178B/ED-12B were not met.
    One example might be the modification of a code table or local or 
private data that can be readily verified by inspection. A second 
example might be minor gain changes necessary for adoption of existing 
equipment to a new airframe. A third example might be the modification 
of a small percentage of code that has no effect on common or global 
data or other forms of coupling between modules nor interfaces with 
other equipment or where such effects are easily limited and where such 
limiting is easily verifiable. A fourth example might be where a non-
essential system with Level 3 software per DO 178A/ED-12A would be 
appropriately re-categorized during the system safety assessment and DO 
178B/ED-12B processes as Level E software. Exemptions such as the above 
were, for the most part, directed at previously approved software-based 
equipment that had an established and acceptable service history 
performing the same function in the same installation environment as 
the new application and for which only significant changes were being 
made such as outlined above.
    Regardless of which version of DO 178/ED-12 was used, ZLT was 
required to submit to the LBA a Plan for Software Aspects of 
Certification (PSAC), a Software Configuration Index (SCI), and a 
Software Accomplishment Summary (SAS) containing the information 
specified in DO 178B/ED-12B, paragraphs 11.1, 11.16, and 11.20, 
respectively, in addition to any other information required by the 
version of DO 178/ED-12 used for the software approval.
    For the software being modified, two acceptable methods of 
upgrading to DO 178B/ED-12B were specified:
    (a) ZLT was allowed to upgrade the entire development baseline, 
including all processes and all data items per the provisions of DO 
178B/ED-12B, section 12.1.4. Existing processes and data items that can 
be shown to already meet the objectives for DO 178B/ED-12B will not 
need upgrading.
    (b) Alternatively, ZLT was allowed to choose an incremental 
approach, using DO 178B/ED-12B processes to make modifications and 
upgrading the

[[Page 24667]]

products (data items) of the life cycle processes only where they are 
affected by the modification. A regression analysis should identify 
those areas of the code and other data items affected by the 
modification. Data items were upgraded in those areas where they were 
directly affected by the modification (for instance, new requirements) 
and where required in order to satisfy the objectives of DO 178B/ED-
12B, Annex A (for instance, where otherwise unmodified requirements 
must be upgraded to provide sufficient data for the requirements-based 
testing of the modified code sections).
    In planning the transition activities using either alternative, ZLT 
should perform an analysis to see where the processes and products of 
the software life cycle do not satisfy the DO 178B/ED-12B objectives. 
This will provide a limit to the activity required and criteria for 
assessing the upgrade.
    To satisfy the provisions of LFLS section 1301 and LFLS section 
1309, the following is required:
    Software development for the LZ N07 will be accomplished according 
to DO 178B/ED-12B (or equivalently acceptable means of compliance) for 
specific systems or equipment. Deviations from this requirement will be 
considered when:
    (a) The software modification is so simple or straightforward that 
an upgrade of the applicant's processes to DO 178B/ED-12B from earlier 
revisions of DO 178/ED-12 is not necessary for assuring that the 
modification is specified, designed, and implemented correctly, and 
verified appropriately; or
    (b) Where a straightforward and readily obvious determination can 
be made by the certifying authority that airworthiness will not be 
affected if some specific objectives of DO 178B/ED-12B were not met.
    The applicant will submit a Plan for Software Aspects of 
Certification (PSAC), a Software Configuration Index (SCI), and a 
Software Accomplishment Summary (SAS) containing the information 
specified in DO 178B/ED-12B, paragraphs 11.1, 11.16, and 11.20, 
respectively, in addition to any other information required by the 
version of DO 178/ED-12 used for the software approval.
    For software modifications, two methods of upgrading to DO 178B/ED-
12B are acceptable:
    (a) Upgrade the entire development baseline, including all 
processes and all data items, per the provisions of DO 178B/ED-12B, 
section 12.1.4. Existing processes and data items that can be shown to 
already meet the objectives for DO 178B/ED-12B will not need upgrading.
    (b) Choose an incremental approach, using DO 178B/ED-12B processes 
to make modifications and upgrading the products (data items) of the 
life cycle processes only where they are affected by the modification. 
A regression analysis should identify those areas of the code and other 
data items affected by the modification. Data items were upgraded in 
those areas where they were directly affected by the modification (for 
instance, new requirements), and where required in order to satisfy the 
objectives of DO 178B/ED-12B, Annex A (for instance, where otherwise 
unmodified requirements must be upgraded to provide sufficient data for 
the requirements-based testing of the modified code sections).
    In planning the transition activities using either alternative, an 
analysis will be performed to determine where the processes and 
products of the software life cycle do not satisfy the DO 178B/ED-12B 
objectives.
    Equipment comprising software that is already certified under TSO, 
JTSO, FAA-STC, or LBA requirements, will be excluded from this 
requirement. However, the software qualification standard of such 
equipment will be at least according to DO 178A.
    Equipment comprising software that is specifically developed for 
use in LZ N07 and modifications to equipment comprising software 
specific for LZ N07 that is not, or is not yet, certified under TSO, 
JTSO, FAA-STC, or LBA requirement, will be certified according to this 
requirement.
    (23) F-3 LBA, Additional Requirements, LFLS Section 1301, Function 
and Installation, and LFLS Section 1309, Equipment, Systems and 
Installations [Electronic Hardware Design Assurance (ASIC)]
Discussion
    The LZ N07 will utilize electronic systems that may perform 
critical and essential functions. During its certification of the 
airship, the LBA made the determination that LBA airworthiness 
requirements did not contain adequate standards or guidance for the 
assurance that the internal hardware of these electronic systems are 
designed to meet the appropriate safety standards. There was no 
existing LBA policy or guidance for showing compliance to the existing 
rules for those aspects of certification associated with Application 
Specific Integrated Circuits (ASICs) and Electronic Programmed Logic 
Devices (EPLDs). Recently, EUROCAE Working Group 46 ``Complex 
Electronic Hardware'' was established to work in cooperation with RTCA 
SC-180 to consider this subject.
    LFLS section 1309 was intended by the LBA as a general requirement 
that should be applied to all systems and powerplant installations (as 
required by LFLS section 901(a)) to determine the effect on the airship 
of a functional failure or malfunction. It is based on the principle 
that there should be an inverse relationship between the severity of 
the effect of a failure and the probability of its occurrence.

Definitions

    a. Continued Safe Flight and Landing: The capability for continued 
controlled flight and landing, possibly using emergency procedures, but 
without requiring exceptional pilot skill or strength. Some airship 
damage may be associated with a Failure Condition, during flight or 
upon landing.
    b. Error: An occurrence arising as a result of incorrect action by 
the flight crew or maintenance personnel.
    c. Event: An occurrence that has its origin distinct from the 
airship, such as atmospheric conditions (e.g., gusts, temperature 
variations, icing, and lightning strikes) runway conditions, cabin and 
baggage fires. The term is not intended to cover sabotage.
    d. Failure: A loss of function, or a malfunction, of a system or 
part thereof.
    e. Failure Condition: The effect on the Airship and its occupants, 
both direct and consequential, caused or contributed to by one or more 
failures, considering relevant adverse operational or environmental 
conditions. Failure Conditions may be classified according to their 
severities as follows:
    (1) Minor: Failure Conditions that would not significantly reduce 
Airship safety and which involve crew actions that are well within 
their capabilities. Minor failure conditions may include, for example, 
a slight reduction in safety margins or functional capabilities, a 
slight increase in crew workload, such as routine flight plan changes, 
or some inconvenience to occupants.
    (2) Major: Failure Conditions that would reduce the capability of 
the Airship or the ability of the crew to cope with adverse operating 
conditions to the extent that there would be, for example, a 
significant reduction in safety margins or functional capabilities, a 
significant increase in crew workload or in conditions impairing crew 
efficiency, or discomfort to occupants, possibly including injuries.
    (3) Hazardous: Failure conditions that would reduce the capability 
of the airship or the ability of the crew to cope

[[Page 24668]]

with adverse operating conditions to the extent that there would be:
    (a) A large reduction in safety margins or functional capabilities;
    (b) Physical distress or higher workload such that the flight crew 
cannot be relied upon to perform their tasks accurately or completely; 
or
    (c) Serious or fatal injury to a relatively small number of the 
occupants.
    (4) Catastrophic: Failure conditions that would prevent Continued 
Safe Flight and Landing.
    f. Redundancy: The presence of more than one independent means for 
accomplishing a given function or flight operation. Each means need not 
necessarily be identical.

Technical Discussion

    LFLS section 1309(b) and (d) require substantiation by analysis 
and, where necessary, by appropriate ground, flight, or simulator 
tests, that a logical and acceptable inverse relationship exists 
between the probability and the severity of each Failure Condition. 
However, tests are not required to verify Failure Conditions that are 
postulated to be Catastrophic. The goal is to ensure an acceptable 
overall Airship safety level, considering all Failure Conditions of all 
systems.
    a. The requirements of LFLS section 1309(b) and (d) are intended to 
ensure an orderly and thorough evaluation of the effects on safety of 
foreseeable failures or other events, such as errors or external 
circumstances, separately or in combination, involving one or more 
system functions. The interactions of these factors within a system and 
among relevant systems should be considered.
    b. The severities of Failure Conditions may be evaluated according 
to the following considerations:
    (1) Effects on the Airship, such as reductions in safety margins, 
degradations in performance, loss of capability to conduct certain 
flight operations, or potential or consequential effects on structural 
integrity.
    (2) Effects on crewmembers, such as increases above their normal 
workload that would affect their ability to cope with adverse 
operational or environmental conditions.
    (3) Effects on the occupants; i.e., passengers and crewmembers.
    (4) For convenience in conducting design assessments, Failure 
Conditions may be classified according to their severities as Minor, 
Major, Hazardous, or Catastrophic. Chapter 1, ``Definitions'' provides 
accepted definitions of these terms.
    (a) The classification of Failure Conditions does not depend on 
whether or not a system or function is the subject of a specific 
requirement. Some ``required'' systems, such as transponders, position 
lights, and public address systems, may have the potential for only 
Minor Failure Conditions. Conversely, other systems that are not 
``required,'' such as flight management systems, may have the potential 
for Major, Hazardous, or Catastrophic Failure Conditions.
    (b) Regardless of the types of assessment used, the classification 
of Failure Conditions should always be accomplished with consideration 
of all relevant factors; e.g., system, crew, performance, operational, 
external, etc. Examples of factors would include the nature of the 
failure modes, any effects or limitations on performance, and any 
required or likely crew action. It is particularly important to 
consider factors that would alleviate or intensify the severity of a 
Failure Condition. An example of an alleviating factor would be the 
continued performance of identical or operationally similar functions 
by other systems not affected by the Failure Condition. Examples of 
intensifying factors would include unrelated conditions that would 
reduce the ability of the crew to cope with a Failure Condition, such 
as weather or other adverse operational or environmental conditions.
    The probability that a Failure Condition would occur may be 
assessed as Probable, Improbable (Remote or Extremely Remote), or 
Extremely Improbable. Each Failure Condition should have a probability 
that is inversely related to its severity.
    1. Minor Failure Conditions may be Probable.
    2. Major Failure Conditions must be no more frequent than 
Improbable (Remote).
    3. Hazardous Failure Conditions must be no more frequent than 
Improbable (Extremely Remote).
    4. Catastrophic Failure Conditions must be Extremely Improbable.
    c. An assessment to identify and classify Failure Conditions is 
necessarily qualitative. On the other hand, an assessment of the 
probability of a Failure Condition may be either qualitative or 
quantitative. An analysis may range from a simple report that 
interprets test results or compares two similar systems to a detailed 
analysis that may (or may not) include estimated numerical 
probabilities. The depth and scope of an analysis depends on the types 
of functions performed by the system, the severities of Failure 
Conditions, and whether or not the system is complex. Regardless of its 
type, an analysis should show that the system and its installation can 
tolerate failures to the extent that Major and Hazardous Failure 
Conditions are Improbable and Catastrophic Failure Conditions are 
Extremely Improbable:
    (1) Experienced engineering and operational judgment should be 
applied when determining whether nor not a system is complex. 
Comparison with similar, previously approved systems, is sometimes 
helpful. All relevant systems Attributes should be considered; however, 
the complexity of the software used to program a digital-computer-based 
system should not be considered because the software is assessed and 
controlled by other means, as described in paragraph 2.i.
    (2) An analysis should consider the application of the fail-safe 
design concept described in paragraph 5 and give special attention to 
ensuring the effective use of design techniques that would prevent 
single failures or other events from damaging or otherwise adversely 
affecting more than one redundant system channel or more than one 
system performing operationally-similar functions. When considering 
such common-cause failures or other events, consequential or cascading 
effects should be taken into account if they would be inevitable or 
reasonably likely.
    (3) Some examples of such potential common-cause failures or other 
events would include rapid release of energy from concentrated sources 
such as uncontained failures of rotating parts or pressure vessels, 
pressure differentials, non-catastrophic structural failures, loss of 
environmental conditioning, disconnection of more than one subsystem or 
component by over temperature protection devices, contamination by 
fluids, damage from localized fires, loss of power, excessive voltage, 
physical or environmental interactions among parts, human or machine 
errors, or events external to the system or to the Airship.
    d. Compliance for a system or part thereof that is not complex may 
sometimes be shown by design and installation appraisals and evidence 
of satisfactory service experience on other Airships using the same or 
other systems that are similar in their relevant Attributes.
    e. In general, a Failure Condition resulting from a single failure 
mode of a device cannot be accepted as being Extremely Improbable. In 
very unusual cases, however, experienced engineering judgment may 
enable an assessment that such a failure mode is not a practical 
possibility. When making such an assessment, all possible and relevant 
considerations should be taken

[[Page 24669]]

into account, including all relevant Attributes of the device. Service 
experience showing that the failure mode has not yet occurred may be 
extensive, but it can never be enough. Furthermore, flight crew or 
ground crew checks have no value if a Catastrophic failure mode would 
occur suddenly and without any prior indication or warning. The 
assessment's logic and rationale should be so straightforward and 
readily obvious that, from a realistic and practical viewpoint, any 
knowledgeable, experienced person would unequivocally conclude that the 
failure mode simply would not occur.
    f. LFLS section 1309(c) provides requirements for system 
monitoring, failure warning, and capability for appropriate corrective 
crew action. Guidance on acceptance means of compliance is provided in 
paragraph 8.g.
    g. In general, the means of compliance described in this Appendix 
to CRI F-ASIC's are not directly applicable to software assessments 
because it is not feasible to assess the number or kinds of software 
errors, if any, that may remain after the completion of system design, 
development, and test. RTCA DO-178A and EUROCAE ED-12A, or later 
revisions thereto, provide acceptable means for assessing and 
controlling the software used to program digital-computer-based 
systems. The documents define and use certain terms to classify the 
criticalities of functions. These terms have the following 
relationships to the terms used in this Appendix to CRI F-ASIC's to 
classify Failure Conditions: Failure Conditions adversely affecting 
non-essential functions would be Minor, Failure Conditions adversely 
affecting essential functions would be Major or Hazardous, and Failure 
Conditions adversely affecting critical functions would be 
Catastrophic.
    h. Functional Hazard Assessment. Before an applicant proceeds with 
a detailed safety assessment, it is useful to prepare a preliminary 
hazard assessment of the system functions in order to determine the 
need for and scope of subsequent analysis. This assessment may be 
conducted using service experience, engineering and operational 
judgment, or a top-down deductive qualitative examination of each 
function performed by the system. A functional hazard assessment is a 
systematic, comprehensive examination of a system's functions to 
identify potential Major, Hazardous and Catastrophic Failure Conditions 
that the system can cause or contribute to not only if it malfunctions 
or fails to function but also in its normal response to unusual or 
abnormal external factors. It is concerned with the operational 
vulnerabilities of the system rather than with the detailed hardware 
analysis.
    Each system function should also be examined with respect to 
functions performed by other Airship systems because the loss of 
different but related functions provided by separate systems may affect 
the severity of Failure Conditions postulated for a particular system. 
In assessing the effects of a Failure Condition, factors that might 
alleviate or intensify the direct effects of the initial Failure 
Condition should be considered, including consequent or related 
conditions existing within the Airship that may affect the ability of 
the crew to deal with direct effects, such as the presence of smoke, 
acceleration vectors, interruption of communication, interference with 
cabin pressurization, etc.
    When assessing the consequences of a given Failure Condition, 
account should be taken of the warnings given, the complexity of the 
crew action, and the relevant crew training. The number of overall 
Failure Conditions involving other than instinctive crew actions may 
influence the flight crew performance that can be expected. Training 
requirements may need to be specified in some cases.
    A functional hazard assessment may contain a high level of detail 
in some cases, such as for a flight guidance and control system with 
many functional modes, but many installations may need only a simple 
review of the system design by the applicant. The functional hazard 
assessment is a preliminary engineering tool. It should be used to 
identify design precautions necessary to ensure independence, to 
determine the required software level, and to avoid common mode and 
cascade failures.
    If further safety analysis is not provided, then the functional 
hazard assessment could itself be used as certification documentation.
    (1) Analysis of Hazardous and Catastrophic Failure Conditions
    (a) A detailed safety analysis will be necessary for each Hazardous 
and Catastrophic Failure Condition identified by the functional hazard 
assessment. Hazardous Failure Conditions should be Improbable 
(Extremely Remote), and Catastrophic Failure Conditions should be 
Extremely Improbable. The analysis will usually be a combination of 
qualitative and quantitative assessment of the design. Probability 
levels that are related to Catastrophic Failure Conditions should not 
be assessed only on a numerical basis, unless this basis can be 
substantiated beyond reasonable doubt.
    (b) For simple and conventional installations, i.e., low complexity 
and similarity in relevant Attributes, it may be possible to assess a 
Catastrophic Failure Condition as being Extremely Improbable on the 
basis of experienced engineering judgment, without using all the formal 
procedures listed above. The basis for the assessment will be the 
degree of redundancy, the established independence and isolation of the 
channels and the reliability record of the technology involved. A 
Failure Condition resulting from a single failure mode of a device 
cannot generally be accepted as being Extremely Improbable, except in 
very unusual cases.
    To satisfy the provisions of LFLS section 1301 and LFLS section 
1309 Equipment, Systems and Installations with respect to Electronic 
Hardware Design Assurance (ASIC), the design considerations and 
analyses described in the above Discussion and Technical Discussion 
will be utilized to accomplish the following:
    Correct operation will be demonstrated by test or analysis under 
all combinations and permutations of conditions of the gates within the 
device for electronic hardware whose anomalous behavior would cause or 
contribute to a failure of a system resulting in a catastrophic or 
hazardous failure condition for the airplane as defined in Advisory 
Circular 23.1309-1C.
    Correct operation will also be demonstrated by test or analysis 
under all combinations and permutations of conditions at the pins of 
the device for electronic hardware whose anomalous behavior would cause 
or contribute to a failure of a system resulting in a major or minor 
failure condition for the airplane as defined in Advisory Circular 
23.1309-1C.
    If the testing and analysis methods outlined above are impractical 
due to the complexity of the device, the electronic hardware should be 
developed using a structured development process. The applicant may use 
the guidelines in RTCA DO-254, ``Design Assurance Guidance for Airborne 
Electronic Hardware'' or another process that is acceptable to the FAA. 
If the applicant chooses to use the guidelines in RTCA DO-254, the 
hardware development assurance levels should be the same as the 
software development assurance levels agreed to by the applicant and 
the FAA.
    (24) F-4 LBA, Additional Requirements concerning LFLS Sections 
1301, 1303, 1305, 1309, 1321, 1322, 1330, and 1431 with respect to 
Liquid Crystal Displays

[[Page 24670]]

Discussion
    ZLT proposed to use Liquid Crystal Displays (LCDs) for presentation 
of Airspeed/Altitude/Attitude/Engine/Warning and Caution information to 
the pilots. The LBA had no published approval criteria for LCD 
technology.
    The LCDs to be installed in the LZ-N07 flight deck will display 
flight information, including functions critical to safe flight and 
landing. There is presently no existing guidance material for Liquid 
Crystal Display airworthiness certification in the LFLS. For the LZ-N07 
certification, the following Guidance Material for LCD airworthiness 
approval was developed. The following Guidance Material provides 
acceptable guidance for airworthiness approval of display systems using 
LCD technology in the LZ-N07.

Guidance Material

Guidance Material for Electronic Liquid Crystal Display Systems 
Airworthiness Approval

Purpose
    This Guidance Material provides guidance for certification of 
Liquid Crystal Display (LCD) based electronic display systems used for 
guidance, control, or decision-making by the pilots of an Airship. Like 
all guidance material, this document is not, in itself, mandatory and 
does not constitute a regulation. It is issued to provide guidance and 
to outline a method of compliance with the rules.
Scope
    The material provided in this section consists of guidance related 
to pilot displays and specifications for LCDs in the cockpit of an 
Airship. The content of the Appendix is limited to statements of 
general certification considerations, including color, symbology, 
coding, clutter, dimensionality, and attention-getting requirements, 
and display visual characteristics.
    a. Information Separation.
    (1) Color Standardization.
    (a) Although color standardization is desirable, during the initial 
certification of electronic displays, color standards for symbology 
were not imposed (except for cautions and warnings in LFLS section 
1322). At that time, the expertise did not exist within industry or the 
LBA, nor did sufficient service experience exist to rationally 
establish a suitable color standard.
    (b) In spite of the permissive LCD color atmosphere that existed at 
the time of initial LCD display certification programs, an analysis of 
the major certifications to date reveals many areas of common color 
design philosophy; however, if left unrestricted, in several years 
there will be few remaining common areas of color selection. If that is 
the case, information transfer problems may begin to occur that have 
significant safety implications. To preclude this, the following colors 
are being recommended based on current-day common usage. Deviations may 
be approved with acceptable justification.
    (c) The following depicts acceptable display colors related to 
their functional meaning recommended for electronic display systems.
    1. Display features should be color-coded as follows:
Warnings--Red
Flight envelope and system limits--Red
Cautions, abnormal sources--Amber/Yellow
Earth--Tan/Brown
Engaged modes--Green
Sky--Cyan/Blue
ILS deviation pointer--Magenta
Flight director bar--Magenta/Green
    2. Specified display features should be allocated colors from one 
of the following color sets:

------------------------------------------------------------------------
                                        Color set 1        Color set 2
------------------------------------------------------------------------
Fixed reference symbols...........  White..............  Yellow \*\
Current data, values..............  White..............  Green
Armed modes.......................  White..............  Cyan
Selected data, values.............  Green..............  Cyan
Selected heading..................  Magenta * *........  Cyan
Active route/flight plan..........  Magenta............  White
------------------------------------------------------------------------
\*\ The extensive use of the color yellow for other than caution/
  abnormal information is discouraged.
\**\ In color Set 1, magenta is intended to be associated with those
  analogue parameters that constitute ``fly to'' or ``keep centered''
  type information.

    (d) When deviating from any of the above symbol color assignments, 
the manufacturer should ensure that the chosen color set is not 
susceptible to confusion or color meaning transference problems due to 
dissimilarities with this standard. The Authority test pilot should be 
familiar with other systems in use and evaluate the system specifically 
for confusion in color meanings.
    (e) The LBA does not intend to limit electronic displays to the 
above colors, although they have been shown to work well. The colors 
available from a symbol generator/display unit combination should be 
carefully selected on the basis of their chrominance separation. 
Research studies indicate that regions of relatively high color 
confusion exist between red and magenta, magenta and purple, cyan and 
green, and yellow and orange (amber). Colors should track with 
brightness so that chrominance and relative chrominance separation are 
maintained as much as possible over day/night operation. Requiring the 
flight crew to discriminate between shades of the same color for symbol 
meaning in one display is not recommended.
    (f) Chrominance uniformity should be in accordance with the 
guidance provided in SAE Document ARP 1874. As designs are finalized, 
the manufacturer should review his color selections to ensure the 
presence of color works to the advantage of separating logical 
electronic display functions or separation of types of displayed data. 
Color meanings should be consistent throughout all color LCD displays 
in the cockpit. In the past, no criteria existed requiring similar 
color schemes for left and right side installations using electro-
mechanical instruments.
    (2) Color Perception versus Workload.
    (a) When color displays are used, colors should be selected to 
minimize display interpretation workload. Symbol coloring should be 
related to the task or crew operation function. Improper color-coding 
increases response times for display item recognition and selection, 
and it increases the likelihood of errors in situations where response 
rate demands exceed response accuracy demands. Color assignments that 
differ from other displays in use, either electromechanical or 
electronic, or that differ from common usage (such as red, yellow, and 
green for stoplights), can potentially lead to confusion and 
information transferal problems.
    (b) When symbology is configured such that symbol characterization 
is not based on color contrast alone but on shape as well, then the 
color information is seen to add a desirable degree of redundancy to 
the displayed information. There are conditions in which pilots whose 
vision is color deficient can obtain waivers for medical qualifications 
under National crew license regulations. In addition, normal aging of 
the eye can reduce the ability to sharply focus on red objects or 
discriminate blue/green. For pilots with such deficiency, display 
interpretation workload may be unacceptably increased unless symbology 
is coded in more dimensions than color alone. Each symbol that needs 
separation because of the criticality of its information content should 
be identified by at least two distinctive coding parameters (size, 
shape, color, location, etc.).
    (c) Color diversity should be limited to as few colors as practical 
to ensure adequate color contrast between symbols. Color grouping of 
symbols, annunciations, and flags should follow

[[Page 24671]]

a logical scheme. The contribution of color to information density 
should not make the display interpretation times so long that the pilot 
perceives a cluttered display.
    (3) Standard Symbology. Many elements of electronic display formats 
lend themselves to standardization of symbology, which would shorten 
training and transition times when pilots change airplane types.
    (4) Symbol Position.
    (a) The position of a message or symbol within a display conveys 
meaning to the pilot. Without the consistent or repeatable location of 
a symbol in a specific area of the electronic display, interpretation 
errors and response times may increase. The following symbols and 
parameters should be position consistent:
    (1) All warning/caution/advisory annunciation locations.
    (2) All sensor data: Altitude, airspeed, glideslope, etc.
    (3) All sensor failure flags. (Where appropriate, flags should 
appear in the area where the data is normally placed.)
    (4) Either the pointer or scale for analogue quantities should be 
fixed. (Moving scale indicators that have a fixed present value may 
have variable limit markings.)
    (b) An evaluation of the positions of the different types of 
alerting messages and annunciations available within the electronic 
display should be conducted, with particular attention given to 
differentiation of normal and abnormal indications. There should be no 
tendency to misinterpret or fail to discern a symbol, alert, or 
annunciation due to an abnormal indication being displayed in the 
position of a normal indication and having similar shape, size or 
color.
    (c) Pilot and copilot displays may have minor differences in 
format, but all such differences should be evaluated specifically to 
ensure that no potential for interpretation error exists when pilots 
make cross-side display comparisons.
    (5) Clutter. A cluttered display is one that uses an excessive 
number and/or variety of symbols, colors, or small spatial 
relationships. This causes increased processing time for display 
interpretation. One of the goals of display format design is to convey 
information in a simple fashion in order to reduce display 
interpretation time. A related issue is the amount of information 
presented to the pilot. As this increases, tasks become more difficult 
as secondary information may detract from the interpretation of 
information necessary for the primary task. A second goal of display 
format design is to determine what information the pilot actually 
requires in order to perform the task at hand. This will serve to limit 
the amount of information that needs to be presented at any point in 
time. Addition of information by pilot selection may be desirable, 
particularly in the case of navigational displays, as long as the basic 
display modes remain uncluttered after pilot de-selection of secondary 
data. Automatic de-selection of data has been allowed in the past to 
enhance the pilot's performance in certain emergency conditions.
    (6) Interpretation of Two-Dimensional Displays. Modern 
electromechanical attitude indicators are three-dimensional devices. 
Pointers overlay scales; the fixed airplane symbol overlays the flight 
director single cue bars that, in turn, overlay a moving background. 
The three-dimensional aspect of a display plays an important role in 
interpretation of instruments. Electronic flight instrument system 
displays represent an attempt to copy many aspects of conventional 
electromechanical displays but in only two dimensions. This can present 
a serious problem in quick-glance interpretation, especially for 
attitude. For displays using conventional, discrete symbology, the 
horizon line, single cue flight director symbol, and fixed airplane 
reference should have sufficient conspicuity such that the quick-glance 
interpretation should never be misleading for basic attitude. This 
conspicuity can be gained by ensuring that the outline of the fixed 
airplane symbol(s) always retains its distinctive shape, regardless of 
the background or position of the horizon line or pitch ladder. Color 
contrast is helpful in defining distinctive display elements but is 
insufficient by itself because of the reduction of chrominance 
difference in high ambient light levels. The characteristics of the 
flight director symbol should not detract from the spatial relationship 
of the fixed airplane symbol(s) with the horizon. Careful attention 
should be given to the symbol priority (priority of displaying one 
symbol overlaying another symbol by editing out the secondary symbol) 
to assure the conspicuity and ease of interpretation similar to that 
available in three-dimensional electromechanical displays.

    Note: Horizon lines and pitch scales that overwrite the fixed 
airplane symbol or roll pointer have been found unacceptable in the 
past.

    (7) Attention-Getting Requirements.
    (a) Some electronic display functions are intended to alert the 
pilot to changes: Navigation sensor status changes (VOR flag), computed 
data status changes (flight director flag or command cue removal), and 
flight control system normal mode changes (annunciator changes from 
armed to engaged) are a few examples. For the displayed information to 
be effective as an attention-getter, some easily noticeable change must 
be evident. A legend change by itself is inadequate to annunciate 
automatic or uncommanded mode changes. Color changes may seem adequate 
in low light levels or during laboratory demonstrations but become much 
less effective at high ambient light levels. Motion is an excellent 
attention-getting device. Symbol shape changes are also effective, such 
as placing a box around freshly changed information. Short-term 
flashing symbols (approximately 10 seconds or flash until acknowledge) 
are effective attention-getters. A permanent or long-term flashing 
symbol that is non-cancelable should not be used.
    (b) In some operations, continued operation with inoperative 
equipment is allowed (under provisions of an MEL). The display designer 
should consider the applicant's MEL desires because in some cases a 
continuous strong alert may be too distracting for continued dispatch.
    (8) Color Drive Failure. Following a single color drive failure, 
the remaining symbology should not present misleading information, 
although the display does not have to be usable. If the failure is 
obvious, it may be assumed that the pilot will not be susceptible to 
misleading information due to partial loss of symbology. To make this 
assumption valid, special cautions may have to be included in the AFM 
procedures that point out to the pilot that important information 
formed from a single primary color may be lost, such as red flags.
    (9) For Both Active Matrix and Segmented Liquid Crystal Displays
    Viewing Envelope: The installed display must meet all the following 
requirements when viewed from a rectangle centered on the design eye 
position and sized 1-foot vertical dimension and 2-feet horizontal 
dimension.
    General: The display symbology must be clearly readable throughout 
the viewing envelope under all ambient illumination levels ranging from 
1.1 lux (0.10 fc) to sun shaft illumination of 86,400 lux (8000 fc) at 
45 degrees incidence to the face of the display.
    Symbol Alignment: Symbols that are interpreted relative to each 
other must be aligned to preclude erroneous interpretation.

[[Page 24672]]

    Flicker: Flicker must not be readily discernible or distracting 
under day, twilight, or night conditions, considering both foveal and 
full peripheral vision, and using a format most susceptible to 
producing flicker.
    Multiple Images: Multiple display images produced by light not 
normal to the display surface must neither be distracting nor cause 
erroneous interpretation.
    Luminance: The display luminance must be sufficient to provide a 
comfortable level of viewing under all conditions and provide rapid eye 
adaptation when transitioning from looking outside the flight deck.
    Minimum Luminance: Under night lighting, with the display 
brightness set at the lowest usable level for flight with normal 
symbology, all flags and annunciators must be adequately visible.
    Lighting: In order to aid daylight viewing, the displays' 
backlighting must be designed such that adequate daylight backlighting 
is provided when the cockpit discrete lighting control is set to the 
`bright' position. In ``non-bright'' positions, the displays must be 
modulated in a balanced fashion in conjunction with other cockpit 
lighting.
    (10) For Active Matrix Displays.
    Matrix Anomalies: For both static and dynamic formats, the display 
must have no matrix anomalies that cause distraction or erroneous 
interpretation.
    Line Width Uniformity: Lines of specified color and luminance must 
remain uniform in width at all orientations. Unintended line width 
variation must not be readily apparent or distracting in any case.
    Symbol Quality: Symbols must not have distracting gaps or geometric 
distortions that cause erroneous interpretations.
    Symbol Motion: Display symbology that is in motion must not have 
distracting or objectionable jitters, jerkiness, or ratcheting effects.
    Image Retention: Image retention must not be readily discernible 
day or night and must not be distracting or cause an erroneous 
interpretation or smearing effect for motion dynamic symbology.
    Defects: Visible defects on the display surface (such as ``on'' 
elements, ``off'' elements, spots, discolored areas, etc.) must not be 
distracting or cause an erroneous interpretation. Service limits for 
defects must be established.
    Luminance Uniformity: Display areas of a specified color and 
luminance must have a luminance uniformity of less than 50 percent 
across the utilized display surface. The rate of change of luminance 
within any small area shall be minimized to eliminate distracting 
visual effects. These requirements apply for any eye position within 
the display viewing envelope.
    Contrast Ratios: The average contrast ratio over the usable display 
surface must be a minimum of 201 at the design eye position and 101 for 
any eye position within the display viewing envelope when measured 
under a dark ambient illumination. This requirement is based on a 0.5 
mm (0.0201) line width. Smaller line widths must have a comparable 
readability, which may require a higher contrast ratio.
    (11) For Segmented Displays.
    Activated Segments: Activated segments must have a contrast ratio 
with the immediately adjacent inactivated background of 21 for viewing 
angles of on-axis to 50 degrees off-axis.
    Inactivated Segments: When segments are not electrically activated, 
there must be no obtrusive difference between the normal background 
luminance, color, or texture and the inactivated segments of the area 
surrounding them. The contrast ratio between inactivated segments and 
the background must not be greater than 1.151 in a light ambient when 
viewed from an angle normal to the display up to an angle 50 degrees 
off-axis.
    For the purpose of this Issue Paper, the following definition 
applies:

Luminance Uniformity = (Lmax - Lmin / Lave (expressed in percent)
Where Lmax = Maximum luminance measured anywhere on the utilized 
display surface
Lmin = Minimum luminance measured anywhere on the utilized display 
surface
Lave = Average luminance of the utilized display surface

    To satisfy the provisions of LFLS sections 1301, 1303, 1305, 1309, 
1321, 1322, 1330, and 1431 with respect to Liquid Crystal Displays, the 
design considerations and analyses described in the above Guidance 
Material will be utilized:
    (a) Equipment comprising LCDs that is not specifically developed 
for use in the LZ-N07, and which is already certified under TSO, JTSO, 
FAA-STC, or LBA Kennblatt, will be excluded and not certified according 
to these guidelines.
    (b) Equipment comprising LCDs that is specifically developed for 
the use in LZ-N07, and modifications to equipment comprising LCDs 
specific for the LZ-N07, and that is not, or not yet, certified under 
TSO, JTSO, FAA-STC, or LBA Kennblatt, will be certified according to 
these guidelines.
    (25) F-5 LBA, Additional Requirements; LFLS Section 1301, Function 
and Installation, and LFLS Section 1309, Equipment, Systems and 
Installations, Use of Commercial Off-The-Shelf (COTS) Software in 
Airship Avionics Systems

General Discussion

    The LZ N07 will be certificated with digital microprocessor based 
systems installed that may contain commercial off-the-shelf (COTS) 
software. This Guidance Material identifies acceptable means of 
certifying airborne systems and equipment containing COTS software on 
the airship.

Background

    Many COTS software applications and components have been developed 
for use outside the field of commercial air transportation. Much of the 
COTS software has been developed for systems for which safety is not a 
concern or for systems with safety criteria different from that of 
commercial airships. Consequently, for COTS software, adequate 
artifacts may not be available to assess the adequacy of the software 
integrity. Available evidence may be insufficient to show that adequate 
software life cycle processes were used. RTCA DO 178B/ED-12B recognizes 
the above and addresses means by which COTS may be shown to comply with 
airship certification requirements.

Technical Discussion

    Document RTCA DO 178B/ED-12B provides a means for obtaining the 
approval of airborne COTS software. For those systems that make use of 
COTS software, the objectives of RTCA DO 178B/ED-12B should be 
satisfied. If deficiencies exist in the life cycle data of COTS 
software, DO 178B/ED-12B addresses means to augment that data to 
satisfy the objectives. If Zeppelin chooses to utilize a means other 
than DO 178B/ED-12B, the LBA requests Zeppelin to propose, via the Plan 
for Software Aspects of Certification (PSAC), how it intends to show 
that all COTS software complies with Airship Requirements LFLS sections 
1301, 1309. Zeppelin should obtain agreement on the means of compliance 
from the LBA prior to implementation.

Abbreviations Used in This Guidance

                                 Table 7
------------------------------------------------------------------------
               Abbreviation                          Explanation
------------------------------------------------------------------------
COTS......................................  Commercial Off-the-Shelf
                                             Software.
CRI.......................................  Certification Review Item.
EUROCAE...................................  European Organization for
                                             Civil Aviation Electronics.
LBA.......................................  Luftfahrt Bundesamt.

[[Page 24673]]

 
LFLS......................................  Airworthiness Requirements
                                             for Airships.
PSAC......................................  Plan for Software Aspects of
                                             Certification.
RTCA......................................  Radio Technical Commission
                                             for Aeronautics.
------------------------------------------------------------------------

    To satisfy the provisions of LFLS Section 1301, Function and 
Installation, and LFLS Section 1309, Equipment, Systems and 
Installations, Use of Commercial Off-the-Shelf (COTS) Software in 
Airship Avionics Systems the design considerations and analyses 
described in the above Guidance Material will be utilized:
    Equipment comprising COTS that is not specifically developed for 
use in the LZ-N07, and which is already certified under TSO, JTSO, FAA-
STC, or LBA Kennblatt, will be excluded and not certified according to 
this Guidance Material.
    Equipment comprising COTS that is specifically developed for use in 
the LZ-N07, and modifications to equipment comprising COTS specific for 
LZ N07, and that is not, or not yet, certified under TSO, JTSO, FAA-
STC, or LBA Kennblatt, will be certified according to this Guidance 
Material.
    (26) F-6 LBA, Sections 1301, 1322, 1528, and 1585; LFLS (Equivalent 
Safety Finding) Envelope Pressure Indicator--Color Coding
Discussion
    To indicate the envelope pressure of the LZ-N07, ZLT will propose 
an instrument (Envelope Pressure Indicator, EPI) that will provide 
annunciation of the Helium and Ballonet Pressure as well as indications 
of the aft and forward Fan and Sensor Fail status using LED columns. 
The measurement range covers a red, amber, and green band by a colored 
scale adjacent to the LED columns. The LED columns are continuously of 
an amber color, due to the technical solution possible only. In 
addition, any out-of-limit pressure determination will trigger a 
discrete warning output to the Integrated Instrument Display System 
(IIDS) for crew alerting and generation of an appropriate warning 
message.
    Using the pressure indications, the flight crew is able to monitor 
and control the airship throughout the flight. Furthermore, the ground 
crew will utilize the EPI to maintain constant pressures in the hull.
    Messages on displays should be unambiguous and easily readable and 
should be designed to avoid confusion to the crew. The use of an amber 
colored LED column, indicating possible red, amber, and green status of 
the associated systems, is not in line with the general color 
philosophy of the LZ N07 cockpit and the applicable LFLS requirements, 
and it was considered by the LBA as an unusual design feature.
    While the LBA allowed the use of amber based on an equivalent 
safety finding, we believe that the provisions of LFLS section 1322, 
where an amber indication is reserved to indicate where immediate crew 
awareness is required and subsequent crew action will be required, 
should be adhered to.
    The control and indicating systems will, therefore, comply with the 
provisions of LFLS section 1322.
    (27) F-7 LBA, Equivalent Safety Finding Section 1387(b) LFLS, Bow 
Light Dihedral Angle
Discussion
    LFLS section 1387(b) requires a dihedral angle formed by two 
intersecting vertical planes making angles of 110 degrees to the right 
and to the left. LFLS appendix table 10 requires, in addition, a 
minimum light intensity of 20 cd throughout the dihedral angle. The LZ-
N07 system only attains the required intensity over 100 degrees but is 
still visible from 100 degrees to 110 degrees (left and right) at a 
reduced intensity. The LBNA granted an equivalency to LFLS section 
1387(b) based on the greater dihedral angle coverage of the aft light, 
+/-80 degrees rather than +/-70 degrees at the specified intensity. 
This is acceptable to the FAA.
    To satisfy the provisions of LFLS section1387(b), the following is 
required:
    The LFLS section 1387(b) required dihedral angle will be no less 
than 100 degrees at the intensities specified in Table 10 of the 
appendix of the LFLS. In addition, the rear light will have an included 
angle of +/-80 degrees at the specified intensity from Table 10 of the 
appendix of the LFLS. Refer to Figure 3.

[[Page 24674]]

[GRAPHIC] [TIFF OMITTED] TN03MY07.020

    (28) Ballast Water.
Discussion
    To minimize the possibility of environmental contamination from 
ballast water, there will be provisions in the airship or servicing 
provisions that ensure that biological or chemical contamination does 
not occur due to the servicing of ballast water of one location and 
dumping of water in a different location. This provision will be added 
to the certification basis as a special environmental requirement:

    Under no circumstances may water ballast be loaded or released 
that does not comply with the provisions of 40 CFR part 141, 
National Primary Drinking Water Regulations. Obtaining water from a 
water supply use for human consumption is acceptable; water aerially 
released or otherwise dumped cannot degrade beyond the limits set by 
40 CFR part 141. If ballast water is contaminated, it can only be 
released into appropriate sewage facilities in accordance with 
national and local laws and regulations. These provisions will be 
explained in the Airship Flight Manual and ground operations 
materials and manuals. Procedures will also be developed that will 
eliminate the possibility of biological contamination growing in the 
ballast system and then being jettisoned or dumped, unless detected 
and treated. The ballast system will have a method of securing 
filler locations to eliminate the possibility of tampering with the 
system.

    Issued in Kansas City, Missouri, on April 10, 2007.
Charles L. Smalley,
Acting Manager, Small Airplane Directorate Aircraft Certification 
Service.
[FR Doc. E7-7302 Filed 4-17-07; 8:45 am]
BILLING CODE 4910-13-P