Determine if isolation diodes are checked during the application of battery or external power before starting the engines. (Example: Red low oil pressure light. If isolation diode is shorted, all panel segments will light as soon as battery or external power is applied.)
(iii) When the isolation diode can be checked before starting engines, further design review is not necessary.
(iv) If diodes are not automatically checked before starting, then additional isolation, should be considered.
c. Annunciator Panel Arrangement. The annunciator panels should be arranged in a logical manner to reduce the crew's time required to locate faults and to increase their efficiency in following Aircraft Flight Manual procedures. For example, engine annunciators on multiengine rotorcraft should be physically located on the panel to coincide with engine location (left or right) so that properly operating engines are not inadvertently shut down due to crew confusion over which engine has malfunctioned.
1218 Par 779
780. RESERVED.
Intentionally Left Blank Par 780 1219
781. Sections 29.1541, 29.1543, and 29.1549 (Amendment 29-12) INSTRUMENT MARKINGS.
a. Background and Explanation.
(1) Aircraft instruments have historically been marked in a variety of ways and with an interesting assortment of symbols. During this period, a limited number of regulatory requirements have been incorporated in the FAR 29, Subpart G, "Markings and Placards," and these efforts have standardized some basic aspects of instrument marking for rotorcraft. As rotorcraft have become increasingly complex with increased number of engines, one-engine inoperative ratings, more sophisticated instrumentation, etc., the need for more specific standards has greatly increased.
(2) It is vitally important that instrument markings be standardized among rotorcraft. When markings are not standardized, considerable confusion and additional workload may be introduced into the cockpit environment. If markings are not standard, it is conceivable that a marking in one rotorcraft could mean the opposite of a similar marking in another rotorcraft. The results of such a situation could be disastrous when pilots fly several rotorcraft models, and particularly in transport rotorcraft under 12,500 pounds, which do not require a pilot type rating.
(3) The following guidance is offered for the purpose of obtaining a general standardization of instrument markings. It is realized that there are a great many variations in instrument presentations for which all guidance may not apply. This is particularly true of new designs, such as cathode ray tube (CRT) displays currently being presented. It is of overriding importance that the philosophies included here be administered, even if specific guidance cannot be applied for particular designs.
Instrument markings are provided to aid interpretation of instruments quickly and accurately. Good instrument markings should indicate operating conditions at a glance.
The best markings are ordinarily the simplest markings.
b. Procedures.
(1) Limits. Each maximum allowable limit substantiated for safe operation must be marked with a red line. This marking should be a red radial line for circular gages. If there is a minimum allowable limit for safe operation, this value should also be marked with a red (radial) line. The use of multiple red (radial) lines should be avoided except where their use is readily usable by the pilot. Normally, no more than one maximum and one minimum red radial line should be incorporated on any one instrument to minimize confusion and avoid potential aircrew errors; however, use of multiple red radial lines may be permitted if such marking can be presented in an acceptable manner.
(2) Normal Operating Range. Each normal operating range should be marked with a green arc or green line which does not extend beyond the maximum and 1220 Par 781
minimum values for continuous safe operation. Discontinuities in width have been used when normal ranges vary with other parameters. Integrating instruments in place of these markings should be encouraged although there may be no regulatory requirement for them.
(3) Cautionary Ranges. Time limited ranges, precautionary ranges, or ranges for which special operating procedures are required should be marked with a yellow arc or yellow line. If a yellow range is used to indicate a special operating procedure, information describing the special procedure should be included in the Rotorcraft Flight Manual.
(4) One-Engine-Inoperative Markings. One-engine-inoperative (OEI) ratings represent a special challenge for retaining simplicity and clarity in powerplant instrument markings. OE ratings are eligible to be used only during an extremely small portion of total flight time; therefore, they should not dominate the presentation or obscure other markings. They are needed only for reference. Indices for 2½-minute and 30-minute power may be marked above the takeoff power redline on engine power instruments. OE reference markings should be clearly distinct from the normal all-engines operating markings. One acceptable means of marking OEl limits has been narrow dashed radials with yellow for 30-minute, and red for 2½-minute limits. OEI markings should be consistent between gages. For example, a 30-minute marking on an N1 or torque gage should be similar in appearance to the 30-minute marking on the engine temperature gage.
(5) Red Arcs or Ranges. Sections 29.1549(d) and 29.1553 allow the use of red arcs. Experience has proven that when red arcs are used to indicate maximum or minimum values, the meaning of a red line loses its significance. Therefore, the use of red ranges or arcs to indicate limit values should be discouraged. Red is conventionally used to represent a limit (maximum or minimum) for which an aircraft or component has been substantiated. A "range" of limits for a given parameter is not consistent with the definition of the terms "limit," "minimum," or "maximum." In addition, a red arc tends to imply that more than one value is limiting, that a scale is provided to show operation within a range of values, and that an absolute limit may not exist until the extreme of a red range is attained. These implications must be avoided wherever possible by specifying a single limiting value and marking it with a single red line (radial). If readings in excess of that value were indicated, it would then be obvious to the crew that a limit had been exceeded. A red arc may be used to indicate a transient vibration range as indicated in § 29.1549(d); however, if the range is a cautionary range and not a prohibited range, use of a yellow arc is recommended. The fuel gage configuration described in § 29.1553 is considered a special application of red arcs. Occasionally a red arc has been utilized when limits vary with other parameters. Discontinuities in width could conceivably represent limits when other parameters are considered. The use of integrating instruments would alleviate much of the problem and should be encouraged although it is recognized that there may be no regulatory requirement for them.
Par 781 1221
(6) Elight Evaluation. In evaluating gage markings, the final criterion must be, "Are the markings adequate for correct interpretation by the crew?" FAAJAUTHORITY evaluations of gage markings should begin early in a certification program utilizing a cockpit or aircraft mock-up whenever possible. All required gages and gage markings must be readable from each pilot station. Depending on cockpit and window geometry, gages should be evaluated in direct sunlight unless they are located high on the panel underneath a substantial glare shield. Evaluation in direct sunlight is especially important for any displays using light bars of digital lighting segments, such as digital radar altimeter presentations or vertical scale instruments using light segments.
Required gages must be readable without upper body movement or extensive head movement by the crew. Evaluators should be especially alert to any scale markings or range markings which are obscured by parallax, as such features are unacceptable. If the aircraft is to be approved for night operation, each required indicator must also be evaluated during night lighting conditions. The same visibility requirements apply for night; however, the evaluator should particularly look for lighting features which may change or obscure the colored markings. For example, in one case, red gage markings were totally obscured by red instrument lighting. Except for minor changes, lighting should be evaluated in flight in order to correctly evaluate vibration effects and various background lighting conditions.
(7) Digital Instruments.
For purposes of this discussion, two types of digital indicator are considered: (1) an indicator which consists of a column of light segments which illuminate sequentially to display changing values, and (2) an indicator which consists of horizontal and vertical line segments in the configuration of a block "g" to display numerical values. Both indicator types work well for parameters where trend information is generally not needed such as engine oil pressure or temperature.
However, for rapidly changing parameters such as engine exhaust gas temperature, torque, or RPM, trend information may not be attainable. Advisory Circular 20-88 (guidelines on the marking of power plant instruments) specifies that instrument markings are intended to provide necessary information at a glance. Trend information for power indicators is vitally important for safe operation of a rotorcraft, and this information must be obtainable at a glance. For the columnar light segments, the ability to quickly detect trend information is largely a function of the resolution provided by single segments (e.g.; if there are two segments for each percent RPM, the ability to detect trend information is better than if there is only one segment for each percent RPM). For digital indicators displaying numerical values, trend information may be unattainable because rapidly changing parameters produce a blur, and this design may be unsuitable as a single source of information. The evaluator should use a great deal of caution to assure adequate trend information is available in primary power and rotor indicators of digital design.
1222 Par 781
7/30/97 АС 29-2B (її) Another area of concern in digital and moving tape instruments is the ability to determine when limits are being approached. Color code markings are frequently incorporated on the moving face of a tape or digital presentation. In such cases, it is mandatory that limit markings be affixed adjacent to the presentation, or that another means be provided so that the pilot can anticipate approaching a limit. The beginning and end of normal and cautionary ranges should be marked adjacent to the display. The entire range need not be color coded adjacent to the display if the colors are integral on the face of the tape or in the individual digital segments. Marking of limit values solely on the tape or in the colored light segments alone is unsatisfactory.
Marking of digital indicators displaying numerical values is adequately addressed in AC 20-88, Paragraph 3, General.
(iii) Appropriate failure modes should be evaluated during the system analysis. This will ordinarily include portions of the digital display. Such failures should be detectable whenever they affect reading accuracy. As a result of this analysis, the system may incorporate a test feature which assures all digital segments operate satisfactorily. This feature should be encouraged.
(8) Additional Markings. To keep markings standardized and uncomplicated, only the FAA/AUTHORITY-approved ranges and limits should be included. Items such as manufacturer's recommended values or manufacturer's warranty information are inappropriate for instrument markings and should not be included. Such information may be presented elsewhere. Transient limits may be indicated by a small red index such as a dot or triangle. Information defining allowable conditions for each transient index should be in the rotorcraft flight manual (e.g., maximum for starting, 12 seconds).
(9) Airspeed Indicator. While the foregoing information is generally applicable to airspeed indicators, some particular features warrant additional attention.
(i> A red cross-hatched radial line should be located at power-off VNE if that value is less than power-on VNE:
Many rotorcraft have erratic, unreliable, or nonrepeatable airspeed indications at low speed which warrant caution when operating in that speed range. In such cases, a yellow arc on the instrument with appropriate flight manual explanation has been found acceptable.
(ill) Indicated airspeed values should be utilized for all airspeed indicator markings.
(iv) Airspeed "bugs" may be used to highlight important takeoff, landing, or limit speeds. This concept may generally be encouraged; however, there are a maximum number of "bugs" that can be utilized without confusion for any given indicator. Typically, two "bugs" are acceptable; three or more are questionable. "Bugs" may also be used on a variety of instruments other than the airspeed indicator.
Par 781 1223
(10) Additiona Reference Material. Additional procedures for marking powerplant instruments are contained in Advisory Circular 20-88. Where conflicts for rotorcraft exist between AC 20-88 and this document, the more recently dated publication should be utilized.
781A. § 29.1549 (Amendment 29-34) POWERPLANT MARKINGS.
a. Explanation. Amendment 29-34 introduces the optional ratings of 30-second/2-minute OEl. Paragraph 29.1549(e) has been revised to show that the limits for the 30-second OE rating are not required to be marked. Use of the 30-second OEI rating is limited to critical phases of operation after a failure or precautionary shutdown of an engine. During this critical stage of operation the crew should not be required to monitor engine instruments to avoid exceedances. Automatic control of the 30-second OEl limits are required by Paragraph 29.1143(e), therefore the 30-second OEI limits are not required to be marked.
b. Procedures. The method of compliance is unchanged except the marking of 30-second OE limits is unnecessary.
782. BOTORCRAFT AND SYSTEMS CERTIFICATION FOR CATEGORY I| OPERATIONS.
a. Explanation.
(1) Category Il instrument approach and landing minimums variations are based on ground facilities and environment, aircraft equipment, crew training, crew proficiency, and maintenance programs. For the pilot, the approach and landing minimums final consideration is the runway visibility which can be, and usually is, related to a cloud ceiling, although the concept is that if there is a runway visibility of 4,000 feet, as an example, there is a very high probability that the ceiling will be at least 300 feet. Therefore, Category I minimums are weather conditions of not less than a 200-foot ceiling and ½-mile visibility or runway visual range (RVR) of 2,400 feet.
Category Il minimums permit approaches at less than 200 feet decision height/RVR 2,400 to as low as 100 feet/RVR 1,200. Category III approach minimums are less than Category Il but will not be discussed here.
(2) The ground facilities required for a Category Il approach and landing include specific approach lighting extending more than 3,000 feet from the runway, thus eliminating any present heliports from being approved for Category Il operations.
Therefore, the following Category Il approvals procedures for rotorcraft assume an approach to a runway at airspeeds at or above MINI
(3) The regulations and advisory material covering the approval for IFR Category Il operations are included in Part 91, Appendix A, and AC 91-16, Category Il 1224 Par 781
Operations - General Aviation Airplanes. Those references address airplanes;
however, the concept is also suitable for the approval of rotorcraft for Category Il operations. The equipment to be required and the procedures to be followed are basically the same for a rotorcraft as for an airplane. Additional reference material concerning Category I approval is contained in FAA Order 8440.5A, General Aviation Operations Inspection's Handbook, and AC 120-29, Criteria for Approving Category I and Category II Landing Minimum for FAR 121 Operations.
(4) Authority for rotorcraft to use Category A airplane minimums is contained in § 97.3(d)(1). FAA Order 8440.5, §§ 97.3, 91.6, and Appendix A of Part 91 provide authority to consider the rotorcraft as a small, Category A aircraft and relief from the requirement for two pilots and two sets of instruments and equipment. Any rotorcraft that is presented for Category Il certification must first meet the requirements for rotorcraft instrument flight (Appendix B, Part 29, Paragraph 781 of this AC).
(5) In addition to the ground facilities and environment noted above, there are requirements in three other general areas to obtain Category Il approval. These are certification of the aircraft and systems, certification and continuation training of flightcrews, and a continuing maintenance program for the aircraft and Category II required systems. The entire Category Il approval requires a Category Il manual that covers all of these areas. FAA/AUTHORITY approval of this manual would normally be the responsibility of the operations and airworthiness inspectors that grant the approval to an operator for Category Il operations.
(6) The additional equipment necessary for a Category Il approval consists of the flight control guidance system. This system can be either a flight director system or an automatic approach coupler. A flight director system needs only to present computed steering data for the instrument landing system (ILS) localizer and should present at least raw glideslope data on the same instrument as the localizer steering commands. A single-axis steering autopilot could be used if it coupled to the ILS localizer. In a practical sense, however, contemporary rotorcraft flight director and automatic pilot systems use at least two-axes command guidance or coupling, and some provide coupling or guidance in three axes; localizer, glidepath, and airspeed. A marker beacon system or a radio altimeter is required for operations with decision heights of 150 feet or less. A rotorcraft flight manual (RFM) supplement is required to define the configuration limitations and procedures for Category Il operation.
b. Procedures.
(1) Instrumentation. Test instrumentation is required to provide a time history of the following parameters throughout each approach:
- Localizer deviation.
- Glideslope deviation.
Par 782 1225
- Radar altitude (if available).
These parameters can be acquired from the cockpit display for each one. The localizer and glideslope deviations are normally recorded as a microampere deviation from the centerline on a continuous strip recording. The radar altitude is continuously recorded as feet above the ground on the same recording device. Any type of recorder that produces a time history of these parameters throughout the approach would be satisfactory. However, a recorder that can be read during, or immediately after, each approach is recommended. This will allow the acceptability of the tracking during the approach to be determined immediately after each approach.
in addition to the above data, cockpit data should be hand recorded on a format similar to that shown in AC 91-16, Attachment 3 (Figures 782-1 and 782-2).
(2) Systems Evaluation.
The major portion of a Category Il approval is the evaluation of the flight guidance system. To certify the flight guidance system for a specific model rotorcraft, a demonstration of 50 LS approaches with a 90 percent success rate (as defined in Part 91) must be accomplished. If the flight guidance system has not been previously certificated in the rotorcraft, a certification program should be completed for the system before the Category Il evaluation is started. It should be determined that the flight guidance system does comply with all the certification requirements before 50 ILS approaches. This is particularly true of an autopilot system where hardover malfunctions must be considered.
(її) The equipment to be installed for Category Il operations must meet the performance criteria specified in AC 120-29, Appendix 1. This material details the criteria for approval of airborne equipment and its installations to meet Category Il performance. This appendix covers the rotorcraft flight manual, the systems ground tests, and the installation requirements and tests. Transport category rotorcraft should meet the same systems performance requirements as transport category airplanes.
(iii) The flight demonstration required for Category Il system approval is explained in Part 91, Appendix A, Paragraph (e). The accuracy requirements for the tracking equipment are included in Appendix 1 of AC 120-29. The usual method of determining the tracking accuracy is by measuring the localizer and glideslope deviations in microamperes and printing them on a continuous strip recorder. The observed cockpit date should also be recorded on a form similar to that in AC 91-16, Attachment 3 (Figures 782-1 and 782-2). Each approach made during the evaluation should have a complete set of data.
(iv) Coupler systems that require manual trimming by the pilot to center the AFCS actuators should be carefully evaluated, especially in turbulent conditions or 1226 Par 782
gusty crosswinds. These systems may not meet the trim requirements at the 100-foot decision height or may not provide sufficient tracking accuracy without excessive pilot attention and workload.
(V) The effects of coupler system hardover malfunctions should be evaluated in all axes to determine the minimum decision height. The altitude loss that would occur from a nose down hardover at the decision height should be determined.
This altitude loss should be included in the rotorcraft flight manual with the appropriate limitation on the minimum height above the ground for operation with the coupler engaged.
(vi) It is recommended that the demonstration approaches be made to Category II ILS facilities, although this is not required by either Part 91, Appendix A, or AC 91-16. Many Category I ILS installations do not provide good enough signals at the lower altitudes for the precise tracking required for Category Il operations. In many cases, this is due to the effects of terrain or buildings off the approach end of the runway. Nevertheless, if satisfactory accuracy can be attained, all the approaches required for a Category Il approval may be made at Category I facilities. During the flight test, especially if simulated IFR conditions are used in good weather, the approach control and control tower of the tacility being used should be advised that Category Il operations are being conducted. The Category II ILS clear areas must be kept unobstructed to allow satisfactory ILS signals. The air traffic control agencies should assure that taxiing aircraft, airfield maintenance trucks, and other airfield traffic are kept out of the critical areas during the data-gathering approaches. These agencies can also monitor the ILS facility for proper operation to Category Il standards and can advise the test aircraft if abnormal operation occurs.
(3) Rotorcraft Flight Manual. Upon satisfactory completion of an engineering inspection and test program, the FAA/AUTHORITY Rotorcraft Flight Manual (RFM), or supplements thereto, should reflect the following:
(1) The limitations, if any.
(il) Revision to the performance section, if appropriate.
(ill) A statement of Category Il approval to the effect that iThe airborne instruments and equipment meet the performance standards for Category Il approaches" and the following note:
"NOTE: Compliance with the performance standards referenced above does not constitute approval to conduct Category Il operations.
Par 782 1227
CATEGORY II APPROACH EVALUATION Pilot in Command Second in Command Date Registration No. Airport_ Runway _ Weather Wind FAA Inspector This form will be completed whenever an approach is attempted utilizing the airborne low approach system, regardless of whether the approach is abandoned or concluded succesfully.
APPROACH EVALUATION MPLI
1. Was the approach successful? YES NO
2. Flight control guidance system used
a. Auto-coupler SA
b. Flight director
c. If equipped and used, did a and b agree? YES NO Second in Command? YES NO FAA Inspector? YES NO
3. Airspeed at middle marker + _at 100' ‡ _from programmed speed?
4. If unable to initiate or complete approach (indicate which), was reason due to:
a. Airborne equipment Identify and describe nature of deficiency.
b. Ground equipment Identify and describe nature of deficiency.
c. Approach control or tower request
d. Other State reason.
5. Was airplane in trim at 100' for continuation of flare and landings?
YES NO
6. If approach and landing abandoned, state altititude above runway:
feet (State reasons)
7. Quality of overall performance: Good L Acceptable _ - Unacceptable L Pilot in Command's Signature FIGURE 782-1 1228 Par 782
CATEGORY II APPROACH EVALUATION (cont.)
INDICATE GLIDESLOPE AND LOCALIZER DISPLACEMENT AT MIDDLE MARKER AND 100 FT. A.G. POINT
MIDDLE MARKER 100 FT. A.G.
INDICATE AIRPLANE DISPLACEMENT & ORIENTATION WITH
RESPECT TO RUNWAY CENTERLINE AT MIDDLE MARKER AND 100 FT. A.G. BY SYMBOL AT AIRPORTS AND RUNWAYS LISTED.
THRESHOLD
RUNWAY WIDTHS SAMP
1.5 | 1. | 0.5| 10.5 11.0 11.5 0 1 100 FT. A.G.
MIDDLE MARKER REMARKS:
CL OF RUNWAY EXTENDED
TOUCHDOWN WAS FEET FROM THRESHOLD AND
FEET LEFT RIGHT OF CENTERLINE FIGURE 782-2 Par 782 1229