[Federal Register Volume 62, Number 68 (Wednesday, April 9, 1997)]
[Rules and Regulations]
[Pages 17048-17052]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-9152]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. NM-132, Special Conditions No. 25-ANM-124]
Special Conditions: Lockheed Martin Aerospace Corp. Model L382J
Airplane
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final special conditions.
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SUMMARY: These special conditions are for the Lockheed Martin Aerospace
Corp. Model L382J airplane. This airplane will have a novel or unusual
design feature(s) associated with the installation of a dual head up
display (HUD) to be used as a primary flight display (PFD) for all
regimes of normal operation. The HUD will satisfy the basic
requirements of Sec. 25.1321 and serve as the primary source of flight
[[Page 17049]]
director command information. These special conditions contain the
additional safety standards which the Administrator considers necessary
to establish a level of safety equivalent to that established by the
airworthiness standards of Part 25 of the Federal Aviation Regulations
(FAR).
EFFECTIVE DATE: May 9, 1997.
FOR FURTHER INFORMATION CONTACT: Dale Dunford, FAA, Flight Test and
Systems Branch, ANM-111, Transport Standards Staff, Transport Airplane
Directorate, Aircraft Certification Service, 1601 Lind Avenue SW,
Renton, Washington 98055-4056; telephone 206-227-2239.
SUPPLEMENTARY INFORMATION:
Background
On August 2, 1992, Lockheed Martin Aerospace Co. applied for an
amendment to their Type Certificate No. A1SO to include their new Model
L382J. The Model L382J is a derivative of the L382B/E/G currently
approved under Type Certificate No. A1SO, and features a new engine
(with approximately the same rated horsepower, but heavily flat-rated)
and propeller, both of which are controlled by a full authority digital
engine control. Additionally, the flight deck is substantially modified
by the installation of four liquid crystal flight displays, dual head-
up displays, and Mil-Std 1553 data buses. The flight engineer position
is deleted, requiring automation of some functions as well as redesign
of the front and overhead panels. Some structure has been modified but
the aerodynamics of the airplane are essentially unchanged. The latest
Part 25 requirement will be used for all significantly modified
portions of the Model 382J (as compared to the present L382), and, for
the unmodified portions of the airplane, the applicable certification
standard will be the Part 25 rules that were effective on February 1,
1965.
The existing rule, Sec. 25.1321, did not anticipate the design
features, symbology, chromatic limitations, and pilot view constraints
associated with most HUDs. This particular HUD application is the first
attempt to qualify the HUD as a PFD. Current head down displays (HDD)
provide all primary and other information without requiring the
flightcrew to transition from one lighting and information display
format to another and are very tolerant of pilot head position
regarding acquiring primary flight data. This HUD application would
require the flight crewmember using the HUD to limit head position in
order to ensure the ability to acquire the necessary flight information
and to frequently transition to a different lighting condition and
display format to acquire flight mode and navigation information. These
proposed special conditions provide all the necessary requirements to
determine acceptability of the HUD as a PFD. A proof of concept effort
is required to substantiate that for the particular application there
are no unsafe features.
Type Certification Basis
Under the provisions of Sec. 21.101, Lockheed Martin Aerospace
Corp. must show that the Model L382J meets the applicable provisions of
the regulations incorporated by reference in Type Certificate No. A1SO
or the applicable regulations in effect on the date of application for
the changes to the Model L382. In addition, the certification basis
includes certain special conditions and later amended sections of Part
25 that are not relevant to these proposed special conditions.
If the Administrator finds that the applicable airworthiness
regulations (i.e., Part 25 as amended) do not contain adequate or
appropriate safety standards for the Model L382J because of a novel or
unusual design feature, special conditions are prescribed under the
provisions of Sec. 21.16.
Special conditions, as appropriate, are issued in accordance with
Sec. 11.49 of the FAR after public notice, as required by Secs. 11.28
and 11.29(b), and become part of the type certification basis in
accordance with Sec. 21.101(b)(2).
Special conditions are initially applicable to the model for which
they are issued. Should the type certificate for that model be amended
later to include any other model that incorporates the same novel or
unusual design feature the special conditions would also apply to the
other model under the provisions of Sec. 21.101(a)(1).
Novel or Unusual Design Features
The Model L382J will incorporate a novel or unusual design feature
which is a dual head up display of primary flight information in a
monochromatic format using appropriate symbology that may be different
from similar information provided in the head down display.
As discussed above, these special conditions are applicable to the
L382J. Should Lockheed Martin Aerospace Corp. apply at a later date for
a change to the type certificate to include another model incorporating
the same novel or unusual design feature, the special conditions would
apply to that model as well under the provisions of Sec. 21.101(a)(1).
Discussion of Comments
Notice of Proposed Special Conditions No. SC-96-5-NM for the
Lockheed Martin Aerospace Corp. Model L382J Airplane, was published in
the Federal Register on September 17, 1996. One commenter submitted
comments.
The Civil Aviation Authority of the United Kingdom submitted
comments on the Notice of Proposed Special Condition for the L382J Dual
Head-up Display (HUD) installation for use as primary flight displays
(PFD) for all phases of flight.
The commenter suggests that paragraphs 1.e. and 2.b. imply a
supplementary HUD, because of the requirement for the pilot to transfer
attention between the HUD and the head down instrumentation. The
commenter requests clarification of the intended function of the HUD,
since this requirement to refer to other displays seems inconsistent
with the intended function of the HUD as a PFD. The commenter also
states that with such a requirement for this transfer in pilot
attention, the scan task workload is significantly increased and should
be separately assessed.
The FAA believes that pilot scan transitions between the HUD and
instrument panel are a natural, necessary pilot function which must be
accommodated and is not inconsistent with its use as a PFD. A PFD does
not provide all information required by the pilot in the normal
performance of duties. The pilot must also refer to other displays for
awareness of navigation, communication, engine, and other system
elements of information. The PFD HUD is not always the sole source of
primary flight information in the cockpit, and FAA experience has shown
that there are occasions when, though the HUD is proven fully
functional, the pilot prefers to use the instrument panel PFD. Two
prime cases are recovery from unusual attitudes, and when the sun is
near the horizon, directly behind the HUD. The FAA recognizes there is
a potential for scan transitions between the PFD HUD and instrument
panel to lead to delays, hazardous misinterpretation, and excessive
cognitive workload if the designs of these instruments are not mutually
compatible. Therefore, the FAA includes this compatibility requirement
in the special condition and intends to evaluate the integrated HUD/
instrument panel design for task performance, workload and pilot error
potential.
The commenter states that the HUD could not be approved as a PFD
under the provisions of JAR 25.1303 and ACJ
[[Page 17050]]
25.1303. JAR 25.1303 requires that the presentation of instruments be
``clear and unambiguous'', and ACJ 25.1303 specifies that the primary
attitude display should distinguish between ``earth and sky'' by the
use of contrasting shades or colors. The commenter states that there is
strong evidence that a monochrome HUD cannot provide for adequate
recognition and recovery from unusual attitudes, and that the pilot
must therefore use the color PFD on the instrument panel for this
purpose. Hence, the HUD cannot be a PFD.
The FAA notes that there are some differences between the FAR and
JAR language and associated advisory materials. In particular, the
portion of JAR 25.1303 quoted by the commenter is not found in
corresponding FAA documents. The FAA agrees with the fundamental
concern expressed by the commenter, and in paragraph 1.d. of the
special condition requires that all information be presented in a clear
and unambiguous manner. However, the FAA is not convinced that color is
an essential display feature of a PFD, and that the ACJ 25.1303
specification for the use of contrasting shades and colors for the
primary attitude display is not found in FAA advisory materials. FAA AC
25-11, Transport Category Electronic Display Systems, states that the
primary purpose of display color is to separate information, to make
the display easier to interpret with less time, workload, and error.
However, the document advises that symbol size, shape and location are
also useful for this purpose, and the AC recommends that at least two
of these features be employed for the display of critical information.
The FAA believes that the PFD must be clear and unambiguous, but is
willing to evaluate alternatives to the use of color in a monochrome
PFD HUD.
With regard to the ability to use the PFD to recognize and recover
from unusual attitudes, the FAA shares the concern of the commenter and
specifies in paragraph 1.g. of the special condition that the HUD be
demonstrated to be adequate for this purpose. In the past, the FAA has
required unusual attitude recovery functionality of some transport HUD
installations.
Compensating special features, in addition to the artificial
horizon and pitch scale, were provided in these monochrome HUD designs,
which the FAA evaluated in flight and found sufficient. Therefore, the
FAA believes that with careful evaluation, a HUD PFD may be found
suitable for the critical function of unusual attitude recognition and
recovery. The FAA also acknowledges that many pilots may prefer the
color PFD for unusual attitude recovery, as well as other flight
conditions referred to above, therefore we have included the
requirement to accommodate transition between the displays in paragraph
1.e.
The commenter states that a monochrome HUD cannot satisfy the color
coding criteria of AC 25-11 which specify the identification of system
limits and warnings with the color red.
The FAA agrees that the monochrome HUD cannot comply with color
coding criteria found in AC 25-11, because no color coding is employed.
The FAA, as stated previously, does not believe that the use of color
is absolutely required. An FAA policy memorandum, entitled Low and High
Speed Awareness Cues for Linear Tape Displays, issued by the Transport
Airplane Directorate on September 12, 1996, states that other
techniques, such as cross-hatching, may be used in a monchromatic HUD
to provide the required distinction between zones of different meaning.
The other purpose of the color coding criteria is to prevent the
use of hazardously misleading variations to the standard color coding,
in particular the use of red, amber and green. Since the monochrome
display does not assign any meaning to colors, it does not violate this
intent of the coding criteria. As stated before, the FAA intends to
evaluate the monochrome HUD for unsatisfactory delays, errors or
workload in the interpretation of the displayed information. For
example, the FAA intends to evaluate the monochrome display to provide
equivalent cues for high and low speed awareness in accordance with
Secs. 25.1303 and 25.1541. Beyond this, the FAA is willing to entertain
specific recommendations for monochrome display criteria.
The commenter states that for the dual HUD installation, the
simultaneous use of both HUDs should not be permitted and a means to
prevent simultaneous use should be provided. The commenter states that
the HUD is so compelling that pilots will not scan other instruments as
required for safe flight.
The FAA agrees that the crew must monitor cockpit instrumentation
to maintain awareness of aircraft system status and flight parameters
and to detect the onset of unsafe conditions. The FAA believes this
monitoring function to be central to the pilot's airmanship
responsibilities and training. A myopic concentration on a single task
or instrument would be contrary to competent, disciplined performance
of pilot duties, but the FAA does not have enough data to support the
contention that the use of a HUD causes unsatisfactory pilot monitoring
of aircraft systems. The use of a HUD, whether PFD or not, does not
inherently prevent or hinder the pilot from scanning other instruments
and displays.
The commenter states that during the cruise phase of flight, the
pilot might be seated at a relaxed sitting position, away from the
Design Eye Position, and unable to detect an upset condition with the
HUD. This may prevent the approval of the HUD as a PFD.
The HUD, in most cases, is not as tolerant of variant head
positions as other cockpit displays. The proposed special condition
requires that the HUD be installed so that the Eyebox is laterally and
vertically centered on the cockpit Design Eye Position (DEP). According
to Secs. 25.773 and 25.777, the DEP is the optimum, secure seating
position from which the pilot can see the instruments and the outside
view, and operate the airplane controls. The pilot responsible for
flying the airplane must be properly seated at or near the DEP in order
to monitor the displays and operate the controls. If that pilot is
using the HUD as a PFD, then the relaxed seating position normally used
by pilots in the cruise phase may not be satisfactory if the minimum
monocular Field of View is not visible.
The special condition states minimum HUD eye box dimensions, in
paragraph 2.g., and also states that a larger eyebox may be required
for a PFD HUD. The HUD must also not place unreasonable, or
physiologically burdensome limitations on head position when used
extensively on long flights. Given these requirements, the FAA believes
it is reasonable to require the pilot to be properly seated to perform
his/her duties, even if the permissible displacements from the DEP are
more limiting for use of the HUD than for use of head down displays.
The commenter states that since the head down displays would often
be used to display only navigation/engine information, the pilots would
not be able to cross monitor each other's primary flight information.
The commenter states that this is not acceptable.
The FAA does not have a specific requirement that one pilot always
be able to view the other pilot's primary flight display. The FAA
requires that the display of hazardously misleading data and the loss
of all indications of certain primary flight parameters be sufficiently
improbable. The ability to view the other pilot's primary flight data
can be a useful technique to detect misleading
[[Page 17051]]
information and to monitor airplane progress during some phases of
flight. But there are other techniques including automatic parameter
comparisons and annunciation of miscompares and excessive deviations.
In some airplanes, a pilot may be able to temporarily select the other
pilot's information for display. Therefore, the FAA does not believe
that a head down PFD for each pilot must always be displayed.
The commenter states that a monochrome HUD PFD would be
significantly cluttered and that the level of clutter must be carefully
assessed.
The FAA is also concerned, wants clutter to be minimized (paragraph
1.d.), and intends to carefully assess the level of clutter in the HUD.
Clutter is a concern both for the pilot's ability to see through the
display to the outside view, and the pilot's ability to quickly and
accurately pick out the desired/essential information from the clutter.
The commenter concludes that the application of Head Up Displays as
stand alone Primary Flight Displays should not be approved because the
monochrome HUD does not meet all current certification criteria for
PFD. Therefore, the commenter states that a dual HUD installation must
be supported by an installation of dual conventional, color, head down
PFDs, simultaneously displayed to each pilot.
The FAA acknowledges the commenter's concerns and intends evaluate
whether, and if so how, the dual-HUD installation should be supported
by the head down display of primary flight data. The FAA intends to
evaluate the adequacy of design features that provide automatic and on-
demand selection of the PFD mode on the head down displays.
Conclusion
This action affects only certain novel or unusual design features
on one model of airplanes. It is not a rule of general applicability,
and it affects only the manufacturer who applied to the FAA for
approval of these features on the airplane.
List of Subjects in 14 CFR Part 25
Air transportation, Aircraft, Aviation safety, Safety.
The authority citation for these special conditions is as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701-44702, 44704.
The Special Conditions
Accordingly, pursuant to the authority delegated to me by the
Administrator, the following special conditions are issued as part of
the type certification for the Lockheed Martin Aerospace Corp. L382J
airplanes.
1. Display Requirements
a. The HUD must provide adequate information to permit rapid
evaluation of the airplane's flight state and position during all
phases of flight. This must be shown to be adequate for manually
controlling the airplane, and for monitoring the performance of the
automatic flight control system. The monochrome HUD must be compliant
with the display criteria contained in Advisory Circular 25-11, except
for the color criteria. The HUD system adequacy for use while manually
controlling the airplane shall be demonstrated and evaluated according
to the rating levels outlined below. This task oriented evaluation must
consider all normal, abnormal and emergency operations, with single and
multiple failures not shown to be extremely improbable and is extended
to all HUD display formats, unless use of specific formats is
prohibited for specific phases of flight. The rating levels for this
evaluation are:
(1) Satisfactory: Full performance criteria can be met with routine
pilot effort and attention.
(2) Adequate: Adequate for continued safe flight and landing; full
or specified reduced performance can be met, but with heightened pilot
effort and attention.
(3) Controllable: Inadequate for continued safe flight and landing,
but controllable for return to a safe flight condition, safe flight
envelope and/or reconfiguration so that the handling qualities are at
least adequate.
The pilot workload and compensation will be allowed to
progressively vary with failure state, atmospheric disturbance level
and flight envelope. Specifically, within the normal flight envelope,
the ratings must not be less than adequate in moderate atmospheric
disturbance for probable failures, and must not be less than adequate
in light atmospheric disturbance for improbable failures.
b. The current mode of the flight guidance/automatic flight control
system, shall be clearly annunciated in the HUD unless it is displayed
elsewhere in close proximity to the HUD field of view and shown to be
equivalently conspicuous. Likewise, other essential information and
alerts which are related to displayed information and may require
immediate pilot action must be displayed for instant recognition. Such
information includes malfunctions of primary data sources, guidance and
control, and excessive deviations which require a go around.
c. If a wind shear detection system, a ground proximity warning
system (GPWS), or a traffic alert and collision avoidance system (TCAS)
is installed, then the guidance, warnings, and annunciations required
to be a part of these systems, and normally required, as part of the
approved design, to be in the pilot's primary field of view, must be
displayed on the HUD.
d. Symbols must appear clean-shaped, clear, and explicit. Lines
must be narrow, sharp-edged, and without halo or aliasing. Symbols must
be stable with no discernible flicker or jitter.
e. For all phases of flight, the HUD must update the positions and
motions of primary control symbols with sufficient rates and latencies
to support satisfactory manual control performance.
f. The HUD display must present all information in a clear and
unambiguous manner. Display clutter must be minimized. The HUD
symbology must not excessively interfere with pilots' forward view,
ability to visually maneuver the airplane, acquire opposing traffic,
and see the runway environment. Some data elements of primary flight
displays are essential or critical, and must not be removed by any
declutter function. Changes in the display format and primary flight
data arrangement should be minimized to prevent confusion and to
enhance the pilots' ability to interpret vital data.
g. The content, arrangement and format of the information must be
sufficiently compatible with the head down displays to preclude pilot
confusion, misinterpretation, or excessive cognitive workload.
Immediate transition between the two displays, whether required by
navigation duties, failure conditions, unusual airplane attitudes, or
other reasons, must not present difficulties in data interpretation or
delays/interruptions in the crew's ability to manually control the
airplane or to monitor the automatic flight control system.
h. The HUD display must be demonstrated to be adequate for airplane
recovery from unusual attitudes. This capability must be shown for all
foreseeable modes of upset, including crew mishandling, autopilot
failure (including ``slowovers''), and turbulence/gust encounters.
2. Installation Requirements
a. The arrangement of HUD display controls must be visible to and
within reach of the pilot from any normal seated position. The position
and
[[Page 17052]]
movement of the controls must not lead to inadvertent operation. The
HUD controls must be adequately illuminated for all normal background
lighting conditions, and must not create any objectionable reflections
on the HUD or other flight instruments.
b. The display brightness must be satisfactory in the presence of
dynamically changing background (ambient) lighting conditions. If
automatic control is not provided, it must be shown that a single
setting is satisfactory. When the brightness level is altered, the
relative luminance of each displayed symbol, character, or data shall
vary smoothly. In no case shall any selectable brightness level allow
any information to be invisible while other data remains discernible.
There shall be no objectionable brightness transients when
transitioning between manual and automatic control. The HUD data shall
be visible in lighting conditions from 0 fL to 10,000 fL. If certain
lighting conditions prevent the crew to adequately seeing and
interpreting HUD data (for example, flying directly toward the sun),
accommodation must be provided to permit the crew to make a ready
transition to the head down displays.
c. To the greatest extent practicable, the HUD controls must be
integrated with other controls, including the flight director, to
minimize the crew workload associated with HUD operation and to ensure
flightcrew awareness of engaged flight guidance modes.
d. The installation of the HUD system must not interfere or
restrict other installed equipment such as emergency oxygen masks,
headsets, or microphones. The installation of the HUD must not
adversely affect the emergency egress provisions for the flightcrew, or
significantly interfere with crew access. The system also must not
hinder the crew's movement while conducting any flight procedures.
e. The installation of the HUD system must not present the crew
with any objectionable glare or reflection in any lighting conditions.
This is equally applicable from glare or reflections visible on the HUD
system itself, or that originating from the HUD system and visible in
other areas such as the windshield. The installation of the HUD system
must not significantly obstruct either pilot's external field of view
when both combiners are deployed. The external view requirements of
Sec. 25.773 must be retained with both combiners deployed.
f. The HUD system must be designed and installed to prevent the
possibility of pilot injury in the event of an accident or any other
foreseeable circumstance such as turbulence encounter, hard landing,
bird strike, etc. The installation of the HUD, including overhead unit
and combiner, must comply with the head injury criteria of Sec. 25.562,
Amendment 25-64.
g. The design eyebox shall be laterally and vertically centered
around the respective pilot's design eye position, and must be large
enough that the minimum monocular field of view is visible at the
following minimum displacements from the cockpit Design Eye Position:
Lateral: 1.5 inches left and right
Vertical: 1.0 inches up and down
Longitudinal: 2.0 inches fore and aft
These requirements must be met for pilots from 5'2'' to 6'3'' tall,
while seated with seat belts fastened and with the pilot positioned at
the design eye position (ref. Sec. 25.777(c)). Larger eyebox dimensions
may be required for meeting operational requirements for use as a full
time primary flight display.
h. The HUD system combiner must not create any objectionable
distortion of the pilot's external view. The optical qualities
(accommodation, luminance, vergence) of the HUD shall be uniform across
the entire field of view. When viewed by both eyes from any off-center
position within the eyebox, non-uniformities shall not produce
perceivable differences in binocular view. Notwithstanding compliance
with these minimum eyebox dimensions, the HUD eyebox must be large
enough to adequately serve as a primary flight display without inducing
adverse effects on pilot vision and fatigue.
3. System Requirements
a. The HUD system must be shown to perform its intended function as
a primary flight display during all phases of flight. The normal
operation of the HUD system cannot adversely affect, or be adversely
affected by other airplane systems. Malfunctions of the HUD system
which cause loss of all primary flight information, including that
displayed on HUDs and head down instruments, shall be extremely
improbable.
b. The criticality of the HUD system's function to display flight
and navigation data, including the potential to display hazardously
misleading information, must be assessed according to Secs. 25.1309 and
25.1333, Advisory Circular (AC) 25-11 paragraph 4.a., and AC 25.1309-
1A. All alleviating flightcrew actions that are considered in the HUD
safety analysis must be validated during testing for incorporation in
the airplane flight manual procedures section or for inclusion in type-
specific training.
c. Since the display of hazardously misleading information on more
than one primary flight display must be extremely improbable, HUD
system software which generates, displays or affects the generation or
display of primary flight information shall be developed to Level A
requirements, as specified by RTCA Document DO-178B, ``Software
Considerations in Airborne Systems and Equipment Certification.''
d. The HUD system must monitor the position of the combiner and
provide a warning to the crew when the combiner position is such that
conformal symbols will be hazardously misaligned.
e. The HUD system must be shown adequate for airplane control and
guidance during an engine failure during any phase of flight.
f. There must be no adverse physiological effects of long term use
of the HUD system, such as fatigue or eye strain, that cause the pilot
to have to revert to the HDD. Use of the HUD system also cannot require
excessive cognitive workload or unreasonable limitations on head
position.
g. The HUD system must be shown to comply with the high intensity
radiated fields certification requirements specified in another special
condition, not yet finalized.
Issued in Renton, Washington, on March 24, 1997.
Stewart R. Miller,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service, ANM-100.
[FR Doc. 97-9152 Filed 4-8-97; 8:45 am]
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