[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]
BILLING CODE 4910-13-P