(A) Range and Accuracy. Tune in a number of radio beacons spaced throughout the 200 - 415 kH range and located at distances near the maximum range for the beacon (see (a) Range and Accuracy). The identification signals should be clear and the ADF should indicate the approximate direction to the stations.
Beginning at a distance of at least 15 NM from a compass locator in the approach configuration, fly inbound on the localizer front course and make a normal ILS approach. Evaluate the aural identification signal for strength and clarity and the ADF for proper performance with the receiver in the ADF mode. All electrical equipment on the aircraft should be operating and all pulse equipment should be transmitting. Fly over a ground check point with relative bearings to the facility of 0, 45, 90, 135, 180, 225, 270, and 315 degrees. The indicated bearings to the station should correlate within 5 degrees.
(B) Needle Reversal. Fly the aircraft over an H, LOM, or LMM facility at an altitude of 1,000 to 2,000 feet above ground level. The indicator needle should make only one reversal.
(C) Indicator Response. With the ADF indicating station dead ahead, switch to a station having a relative bearing of approximately 175 degrees. The indicator should indicate within +5 degrees of the bearing in not more than 10 seconds.
(D) Antenna Mutual Interaction. If the ADF installation being tested is dual, check for coupling between the antennas by using the following procedure.
(1) With #1 ADF receiver tuned to a station near the low end of the ADF band, tune the #2 receiver slowly throughout the frequency range of all bands and determine whether the #1 ADF indicator is adversely affected.
(2) Repeat (A) with #1 ADF receiver tuned to a station near the high end of the ADF band.
(8) Distance Measuring Equipment (DME).
(1) The DME system should:
(A) Continue to track without dropouts when the rotorcraft is maneuvered throughout the air space within 100 NM of the VORTAC station and at altitudes from the radio line of sight to the maximum altitude for which the rotorcraft is certificated. This tracking standard should be met with the rotorcraft in the cruise configuration, at bank angles up to 10 degrees, climbing and descending at normal maximum climb and descent attitude, and orbiting a DME facility.
(B) Provide clearly readable identification of the DME facility.
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(C) DME operation should not interfere with other systems aboard the rotorcraft (some interference with the transponder may be acceptable) and DME operation should not be adversely affected by other equipment.
(D) DME Hold.
The DME should continue to operate and track when DME Hold is activated and the channel switch is varied.
(E) DME Override. When an override switch is provided, proper operation should be demonstrated.
(ії) Technique.
(A) Climb and Maximum Distance. Determine that there is no mutual interference between the DME system and other equipment aboard the rotorcraft. Beginning at a distance of at least 10 NM from a DME facility and at an altitude of 2,000 feet above the DME facility, fly the rotorcraft on a heading so that the aircraft will pass over the facility. At a distance of 5 to 10 NM beyond the DME facility, operate the rotorcraft at its normal maximum climb attitude up to an altitude of 7,000 feet maintaining the aircraft on a station radial (within 5 degrees). The DME should continue to track with no unlocks to a range of 100 NM. Record the maximum altitude flown.
(B) Long Range Reception. Perform two 360 degree turns, one to the right and one to the left, at a bank angle of 8 to 10 degrees at least 100 NM from the DME facility. A single turn will be sufficient if the antenna installation is symmetrical.
There should be no more than one unlock not to exceed one search cycle (maximum 35 seconds) in any 5 miles of radial flight.
(C) Penetration. From an altitude of above 7,000 feet (AGL) perform a let-down directly toward a ground station (DME facility) at a normal maximum rate of descent so as to reach an altitude of 5,000 feet above the DME facility 5 to 10 NM before reaching the DME facility. The DME should continue to track during the maneuver with no unlocks.
(D) Approach. Make a normal approach to land at a field with a DME located on the airport. The DME should track without an unlock (station passage excepted).
(E) DME Hold. With the DME tracking, activate the DME hold function. Change the channel selector to a localizer frequency. The DME should continue to track on the original station.
(9) Transponder Equipment.
Par 776 1201
Performance Criteria. The ATC transponder system should furnish a strong and stable return signal to the interrogating radar facility when the rotorcraft is flown in straight and level flight throughout the air space within 100 NM of the radar station from radio line of sight to within 90 to 100 percent of the maximum altitude for which the rotorcraft is certificated. The airborne system should be controllable so that objectionable ring-around, spoking and clutter will not persist. The transponder system should not interfere with other systems aboard the rotorcraft and other equipment should not interfere with the operation of the transponder system (some interference from DME operation may be acceptable). When the rotorcraft is flown in the following maneuvers within the air space described above, the dropout time should not exceed 20 seconds.
(A) In turns at bank angles up to 10 degrees.
(B) Climbing and descending at normal maximum climb and descent attitude.
(C) Orbiting a radar facility.
(i) Technique.
(A) Climb and Distance Coverage: Beginning at a distance of at least 10 NM from and at an altitude of 2,000 to 3,000 feet above that of the radar facility and using a transponder code assigned by the ARTCC, fly on a heading that will pass the rotorcraft over the facility. At a distance of 5 to 10 NM beyond the facility, operate the rotorcraft to maintain an altitude above radio line of sight while maintaining the aircraft at a heading within 5 degrees from the radar facility to 100 NM from the radar facility.
(B) Communicate with the ground radar personnel for evidence of transponder dropout. During the flight, check the "ident" mode of the ATC transponder to assure that it is performing its intended function. Determine that the transponder system does not interfere with other systems (except possibly the DME) aboard the rotorcraft and that other equipment (except possibly the DME) do not interfere with the operation of the transponder system. There should be no dropouts, that is, when there is no return for two or more sweeps. The operation of the ATC transponder should be verified over the station, at 25 NM, and at 100 NM.
(C) Long Range Reception. Perform two 360-degree turns, one to the right and one to the left, at bank angles of 8 to 10 degrees with the flight pattern at least 100 NM from the radar facility. During these turns, the radar display should be monitored and there should be no signal dropouts (two or more sweeps).
(10) Weather Radar Equipment.
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7130/97 AC 29-2B (i> Bearing Accuracy. The indicated bearing of objects shown on the display should be within 5 degrees of their actual magnetic bearing within the sectors 40 degrees right and left of the aircraft longitudinal axis. Beyond 40 degrees right and left, bearing accuracy should be +10 degrees.
(її) Distance of Operation. The radar should be capable of displaying prominent targets throughout the distance and angular range of the display.
Antenna Stabilization. When antenna stabilization is provided, it should eliminate blurring of the display for the ranges of pitch and roll for which it is designed.
(iv) Beam Tilting. The radar antenna should be installed so that its beam is adjustable to any position between 10 degrees above and 10 degrees below the plane of rotation of the antenna.
(V) Technique.
(A) Bearing Accuracy. Fly under conditions which allow visual identification of a target, such as an island, a river, or a lake, at a range within 10 percent of the maximum range of the radar. When flying toward the target, select a course that will pass over a reference point from which the bearing to the target is known. When flying a course from the reference point to the target determine the error in displayed bearing to the target on all range settings. Change heading in increments of 10 degrees and determine the error in the displayed bearing to the target.
(B) Contour Display (Iso Echo). If heavy cloud formations or rainstorms are reported within a reasonable distance from the test base, select the contour display mode. The radar should differentiate between heavy and light precipitation. In the absence of the above weather conditions, determine the effectiveness of the contour display function by switching from normal to contour display while observing large objects of varying brightness on the indicator. The brightest objects should become the darkest when switching from normal to contour mode.
(C) Stability. While observing a target return on the radar indicator, turn off the stabilizing function and put the aircraft through pitch and roll movements.
Observe the blurring of the display. Turn the stabilizing mechanism on and repeat the roll and pitch movements. Evaluate the effectiveness of the stabilizing function in maintaining a sharp display.
(D) Ground Mapping. Fly over areas containing large, easily identifiable landmarks such as rivers, towns, islands, coastlines, etc. Compare the form Par 776 1203
of these objects on the indicator with their actual shape as visually observed from the cockpit.
(E) Mutual Interference. Determine that no objectionable interference is present on the radar indicator from any electrical or radio/navigational equipment when operating, and that the radar installation does not interfere with the operation of any of the rotorcraft's radio/navigational systems.
(11) Area Navigation. Advisory Circular 90-45A is the basic criteria for evaluating an area navigation system, including acceptable means of compliance to the FAR.
(12) Inertial Navigation. Advisory Circular 25-4, Inertial Navigation Systems, is the basic criteria for the engineering evaluation of an inertial navigation system (INS) and offers acceptable means of compliance with the applicable Federal Aviation Regulations which contain mandatory requirements in an objective form. The engineering evaluation of an INS should also include awareness of Advisory Circular 121-13, Self-Contained Navigation Systems (Long Range), which presents criteria to be met before an applicant can get operational approval. For flights up to 10 hours, the radial error should not exceed 2 nautical miles per hour of operation on a 95 percent statistical basis. For flights longer than 10 hours, the error should not exceed +20 NM crosstrack or 125 NM along track error. A 2-nautical-mile radial error is represented by a circle, having a radius of 2 nautical miles, centered on the selected destination point.
(13) Doppler Navigation. Doppler navigation system installed performance should be evaluated in accordance with Advisory Circular 121-13. (See FAR 121, Appendix G).
(14) Radio Altimeters. Radio altimeter system installed performance should be evaluated in accordance with RTCA Document DO-123, Appendix A, Part II.
(15) Emergency Locator Transmitters (ELT).
(i) Emergency locator transmitter performance should be evaluated in accordance with TSO-C91. ELT installations should be examined for potential operational problems. There have been numerous instances of interaction between ELT and other VHF installations. ELT antenna installations in close proximity to other VHF antennas should be suspect. Antenna patterns of previously installed VHF antennas should be measured after an ELT installation. Some problems caused by ELT installations are:
(A) Loss of radiated power from VHF communications.
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(B) Reradiation of VHF transmitter energy such that navigation crosspointers are affected.
(C) Reception of FM broadcast, at high level, in VHF communications.
(D) Inadvertent activation of the ELT by VHF transmitted energy.
(See AD 72-22-3.)
(ii) ELT Installation. TSO-C91 specifies that the ELT be automatically activated when subjected to a force of 5.0 (+2,-0)g in the direction of the longitudinal axis of the aircraft. This recommendation for mounting is considered satisfactory for rotorcraft. In recognition of the significant vertical impact velocity that rotorcraft commonly have an optional placement of the ELT pitched down 30° from the horizontal axis of the rotorcraft is also satisfactory.
(16) Audio Interphone Systems. Acceptable communications should be demonstrated for all audio equipment including microphones, speakers, headsets, and interphone amplifiers. All modes of operation should be tested, including operation during emergency conditions (i.e., emergency descent, and oxygen masks) with all rotorcraft engines running, all rotorcraft pulse equipment transmitting, and all electrical equipment operating.
(17) Portable Battery Powered Megaphones (AC 121-6). Megaphone performance should be evaluated in accordance with AC 121-6.
(18) Omega and Omega/LF Navigation Systems. Omega and Omega/LF Navigation systems should be evaluated in accordance with the following AC's that apply to the type of approval requested:
(1) AC 120-37, Approval of Omega Systems, as a sole means of overwater long range navigation.
(it) AC 120-31A, Approval of Airborne Omega Navigation Systems, as a means of updating self-contained navigation systems.
(Ш) AC 20-101B, Approval of Omega and Omega/LF Navigation.
(19) Rotorcraft Condition Monitoring System Installations.
(i) General. Avionics equipment and systems are being installed in rotorcraft to collect data to be used in assessing engine/rotorcraft performance and frequency of maintenance. Some of the items monitored are engine operating exceedances, hot starts, power assurance, and cycle counts. The monitoring systems being addressed by this paragraph are those used to collect data for maintenance Par 776 1205
purposes not those monitors which are utilized as part of the control system for autopilot/flight controls or engine controls. At present, optional approvals are being requested for most of these systems not performing any required functions. However, most of the applicants anticipate requesting approval for the systems to be used in the future to perform some required function or to allow required maintenance to be predicated on the operation of the system. This consideration becomes particularly important if the system is software based. A further discussion of system software is included in Paragraph 776b(19) (IlI) (B).
(i) System Installation. The system installation should be shown to be free from hazards considering both normal operation and possible malfunctions.
Malfunctions which might be caused by software errors are discussed under Paragraph 776b(19) (ili)(B). The accuracy and response of the monitoring device/system should be sufficient to allow the operational and maintenance personnel to relate the data obtained to required maintenance actions. The exceedance (engine limit) information being acquired by these systems is or will be used in place of information previously acquired from field reports of operational personnel utilizing the basic aircraft instruments. In this case, the automated system will generally produce results which are more accurate than the basic aircraft instruments. However, in this circumstance, it is not appropriate to require the monitor system to be more accurate than the previously approved methods used to provide the required exceedance data.
If the data collected by the system require filtering prior to use, it is equally acceptable to accomplish this filtering either as the data are being acquired (airborne function) or when the data are analyzed (ground based function) and used in the maintenance of the rotorcraft.
(Ш) System Components.
(A) Hardware. The hardware of the system when operating under the control of the imbedded software should be shown to comply with § 29.1301.
Additionally, in showing compliance to § 29.1309(a), laboratory testing to the appropriate portions of the latest revision of RTCA Document DO-160 should be performed.
(B) Software. If the function of the monitor system depends on embedded airborne software to determine all or part of its functioning, Document DO-178 is the recommended standard to be used for the approval of the system software. A further discussion of the use of this document is included in Paragraph 621. The selection of the software level should be carefully considered because system approval is sometimes initially sought on the basis of the system being a non-required optional system. If it has further been shown that no dependence is made on the system software to preclude a hazardous failure mode, then a low sottware level would be acceptable. However, it is very difficult to qualify software to higher levels of "quality" once the software has been initially certified. Because of this, it is recommended that the software be chosen to the level consistent with the ultimate 1206 Par 776
use to which approval of the system is planned. If the system is to be approved only as non-required optional equipment, then the choice of a low level of software qualification may be appropriate. However, when more experience is gained with the operation of the system, and it is ultimately planned to seek approval to perform required functions, then an appropriate higher level of software should be initially obtained.
NOTE: Extensive service experience should not be considered as a basis for level of criticality without accomplishing RTCA DO-178 procedures.
(20) Night Vision Goggles (NVG).
(i> Background. Night vision goggles (NVG) have been used by U.S.
military pilots since the early 1970's. The first units (first generation or GEN I) were constructed from the rifle "Sniper-Scopes." These units did not provide much light amplification. The second generation (GEN II) were still primarily designed for ground use. Second generation high performance units (military designation AN/PVS-5C) had some consideration for flight use but were still lacking in several aspects. A light level of at least a quarter moon well above the horizon was required for operation of these NG. At first the normally helmet-mounted units covered the pilot's entire upper face and the pilot could only see through the NVG. In order to protect the light amplification system these NVG had an automatic shutoff feature when brighter than relatively low levels of light were encountered. Normal incandescent and especially red incandescent lights would cause these NG to shut down. Aircraft cockpit lights, especially the red warning lights, would cause "blooming" (an increased brightness of all or portions of the NVG field of view with the disappearance of the "picture" in that area or a total shutdown of the NVG. Military aircraft cockpits and lighting systems were significantly modified to avoid this problem. In the late 1980's the military pushed technology for better and aircraft compatible NVG. Third generation (GEN III, military designation ANVIS or AN/AVS-6) NVG systems became available about 1988. These systems require only star light for satisfactory operation.
(¡i) Procedures. As of January 1990, no approvals for civil rotorcraft operations with NVG have been issued. Since NVG are not installed in the rotorcraft, they are not required to be approved as part of the type design. However, since an operational approval would be required for use of NG, they should meet some acceptable performance standard. The minimum standard recommended is the GEN III NVG. The performance of these NVG are rated as their spectral response to irradiated light sources, measured as density of incident photons per square meter.
Third generation, AN/AVS-6, NVG have been evaluated for compatibility with a limited number of rotorcraft and were generally found to be usable during en route operations with no cockpit lighting systems modifications. It is anticipated, however, that some aircraft may require significant modifications to the existing cockpit lighting system. The FAA/AUTHORITY policy is that modification of the cockpit to a non-compliant configuration to accommodate NVG use is not acceptable. For instance, alteration of the required red warning annunciators to some other color is not acceptable. Since Par 776 1207
individual rotorcraft may have been modified with additional lights or systems, each rotorcraft being considered for use with NG should be evaluated by an FAAJAUTHORITY representative during a night flight. If it is anticipated that cockpit lighting system modifications will be required to achieve an adequate level of NVG compatibility FAA/AUTHORITY involvement should be arranged as soon as possible.
Preferably this evaluation flight would be made with two pilots or a pilot and safety observer, over a known area, where all the aircraft and cockpit lights are operated and their effect on the NVG determined. Reflections of landing or searchlights on windshields or other glass during approach or landing may affect NVG and may impose a minimum altitude restriction for use of NG. Failure of the NVG should be evaluated during any critical flight phase.
Note that the above discussion is purposely limited in scope. Issues such as crew training and operating limitations would have to be addressed in detail to obtain an operational approval.
(21) Rotorcraft Health and Usage Monitoring Systems (HUMS).
General. HUMS can be divided into two major categories: Health Monitoring Systems and Usage Monitoring Systems. The provisions of § 29.1301 are used to determine that the system performs its intended function. The provisions of § 29.1309(a) and (b) are used to look at the impact of environmental conditions and malfunctions. To date (mid-1990) HUMS have not been approved to replace service life or other specific physical limits but several systems are now in the process of seeking approval. Health monitoring systems are considered to be the serious applications of this technology, and it will probably be some time before the necessary data base to allow full reliance on this technology is available. There have been numerous approvals of usage monitoring systems as optional equipment, and a good example of this technology is a condition monitoring system described in 776b(19) above.
(iI) Health Monitoring Systems.
(A) It is anticipated these systems will begin as "optional" systems in order to build a data base to support expansion of the approval to achieve credit for extension of maintenance intervals, and so forth. Systems range from low to high integrity requirements depending on the determined criticality of application.
(B) Some systems that are being considered will utilize off aircraft processing of data. If this is to be pursued it should be assumed that the aircraft data will be lost or misplaced at the processing center, and the aircraft system design should consider this possibility. Some on-board data storage is one way to account for this lost data. The integrity of the processing center's software should be equal to that of the aircraft software. In addition the intervals for processing the data from each flight should be specified as part of the approval.
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(C) Due to the limited experience with these systems it is suggested the issue paper process be utilized to record the progress of the approval, and to provide information for later updating of this AC material.
777. STANDARDIZED TEST PROCEDURE FOR ROTORCRAFT DC ELECTRICAL SYSTEM TESTS.
a. Test Requirements.
(1) General. The following functions and characteristics are to be evaluated:
(1) Normal System Operation.
(il) Parallel Load Division.
(IlI) Excitation.
(iv) Stabilization.
(v) Systems Malfunction.
(vi) Environmental Capability.
(vii) Electromagnetic Compatibility.
(vili) Cooling Capability.
(ix) Surge Characteristics, Ripple Voltage, and Voltage Spikes.
(2) Instrumentation. Calibration records should be available for all instrumentation. Current and voltage vs. time should be recorded in a permanent form.
Enough specific currents and voltages should be recorded to allow reconstruction of any sequence of events that would happen as a result of any system testing described herein.
(3) Regulatory References. Sections 29.1301, 29.1307(c), (d), (e), 29.1309,
29.1351, 29.1353, 29.1355, 29.1357, 29.1363.
(4) Miscellaneous. The assigned FAA/AUTHORITY systems and equipment engineer normally witnesses these tests and should be notified as far in advance of the testing as possible to minimize scheduling problems. Conformity of the test setup must be established prior to conducting any testing. Most of the above test categories can be conducted on a bench test setup. A bench test setup is especially recommended in the case of the system malfunction tests. It is the applicant's option to demonstrate his Par 776 1209
equipment either on the bench or installed for ground tests. When a bench setup is used, it should represent the actual aircraft installation to the extent that components and wiring (type, gage, and length) are duplicated. Some retesting may be necessary on the aircraft to verify the bench test results.
b. Ground and Bench Test Procedures.
CAUTION: Prior to disconnecting the battery and removing or adding large loads, either isolate the avionics systems or assure that transients induced are within limits of the avionics equipment.
(1) Normal System Operation.
NOTE: Equipment should be operated for at least 10 minutes prior to each test as a warmup.
Minimum electrical load for paralleling and minimum engine RPM.
(il) Vary RPM of all engines from low to high and back to low.
(iii) Repeat b(1)(iI) for maximum and 50 percent of maximum electrical loads.
(2) Parallel Load Division (if parallel system).
Minimum electrical load for paralleling and minimum engine RPM.
(ii) Fifty percent of maximum electrical load and minimum engine RPM.
(iii) Maximum electrical load and minimum engine RPM.
(iv) Minimum electrical load for paralleling, vary No. 1 engine RPM from low to high and back to low while holding the RPM of the other engine at minimum (low).
(V) Repeat b(2)(d) for each other engine on the rotorcraft.
(vi) Repeat b(2)(d) and b(2)(e) procedures with 50 percent of maximum electrical load.
(vii) Repeat b(2)(d) and b(2)(e) procedures with a maximum electrical load.
(3) Excitation.
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NOTE: All of these tests are to be conducted with the battery OFF since the purpose of the tests is to determine if the ship's battery is necessary for excitation of the alternators)/generator(s).
(i> Minimum anticipated electrical load, low engine RPM, and alternator(s)/generator(s) OFF. Demonstrate that when an alternator/generator is turned ON, it will come on the line. Repeat for any other alternators/generators in the system.
(ii) Maximum electrical load, low engine RPM, and alternator(s)/generator(s) OFF. Demonstrate that each alternator/generator will individually come on the line.
(iii) Minimum anticipated electrical load, high engine RPM, and alternator(s)/generator(s) OFF. Demonstrate that each alternator/generator will individually come on the line.
(4) Stabilization.
NOTE: All of these tests are to be conducted with the ship's battery OFF, since the purpose of the tests is to determine if the ship's battery is necessary for stabilization of the alternator/generator. In each case, if the ship's battery is not necessary for stabilization, the alternator/generator should be on the line and remain there at a satisfactory voltage level.
(i) Minimum anticipated electrical load, low engine RPM, alternator(s)/generator(s) ON. Switch on the heaviest electrical load that is anticipated to be installed on the aircraft.
(її) Repeat b(4)(i) for a maximum electrical load and low engine RPM.
(iii) Repeat b(4)(i) for a minimum anticipated electrical load and high engine RPM.
(iv) Repeat b(4)(i) for a maximum electrical load and high engine RPM.
(5) System Malfunctions.
(i) Overcurrent faults (faults to airframe ground that are less than
5.0 Milliohms) should be applied to buses and feeders as necessary to demonstrate that the system's overcurrent circuit protective devices are properly coordinated and provide adequate protection/fault isolation.
(ii) Simulate an overvoltage condition on each alternator/generator to demonstrate satisfactory operation of the overvoltage sensing network. On a Par 777 1211