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(x) Hoist system flight-tests . An in-flight demonstration test of the hoist system should be conducted for helicopters designed to carry NHEC or HEC. The rotorcraft should be flown to the extremes of the applicable maneuver flight envelope and to all conditions that are critical to strength, maneuverability, stability, and control, or any other factor affecting airworthiness. Unless a lesser load is determined to be more critical for either dynamic stability or other reasons, the maximum hoist system rated load or, if less, the maximum load requested for approval (and the associated limit load data placards) should be used for these tests. The minimum hoist system load (or zero load) should also be demonstrated in these tests.
(6) § 29.865(b)(3)(ii) Electromagnetic Interference : Protection of the QRS against potential internal and external sources of electromagnetic interference (EMI) and lightning is required. This is necessary to prevent inadvertent load release from sources such as lightning strikes, stray electromagnetic signals, and static electricity.
(i) Jettisonable NHEC systems - should be able to absorb a minimum of 20 volts per meter (i.e., CAT U) radio-frequency (RF) field strength per RTCA/DO-160.
(ii) Jettisonable HEC systems - should be able to absorb a minimum of 200 volts per meter (i.e., CAT Y) RF field strength per RTCA/DO-160.
NOTE 1: These RF field threat levels may need to be increased for certain special applications such as microwave tower and high voltage high line repairs. Separate criteria for special applications under multi-agency regulation (such as IEEE or OSHA standards) should also be addressed, as applicable, during certification. When necessary, the issue paper process can be used to establish a practicable level of safety for specific high voltage or other special application conditions. For any devices or means added to meet multi-agency regulations, their failure modes should not have an adverse effect on flight safety. Other certification authorities may require higher RF field threat levels than those required by § 29.865 (e.g., the European Joint Aviation Authorities Interim HIRF policy).
NOTE 2: An approved standard rotorcraft test that includes the full HIRF frequency and amplitude external and internal environments on the QRS and PCDS (or the entire rotorcraft including the QRS and PCDS) could be substituted for the jettisonable NHEC and HEC systems tests defined by d(6)(i) and d(6)(ii), respectively, as long as the RF field strengths directly on the QRS and PCDS are shown to equal or exceed those of d(6)(i) and d(6)(ii).
NOTE 3: The EMI levels specified in d(6)(i) and d(6)(ii) are total EMI levels to be applied to the QRS (and affected QRS component) boundary. The total EMI level applied should include the effects of both external EMI sources and internal EMI sources. All aspects of internally generated EMI should be carefully considered including peaks that could occur from time-to-time due to any combination of on-board systems being operated. For example, special attention should be given to EMI from
AC 29-2C, Chg 2 4/25/06 Page D - 156 hoist operations that involve the switching of very high currents. Those currents can generate significant voltages in closely spaced wiring that, if allowed to reach some squib designs, could activate the device. Shielding, bonding and grounding of wiring associated with operation of the hoist and the quick-release mechanism should be clearly and adequately evaluated in design and certification. This evaluation may require testing. One acceptable test method to demonstrate adequacy of QRS shielding, bonding and grounding, would be to actuate the hoist under maximum load together with likely critical combinations of other aircraft electrical loads and demonstrate that the test squibs (that are more EMI sensitive than the squibs specified for use in the QRS) do not inadvertently operate during the test.
(7) § 29.865(c)(1) QRS Requirement s for Jettisonable HEC Operations:
For jettisonable HEC operations, both the PQRS and BQRS are required to have a Dual Actuation Device (DAD) for external cargo release. Two distinct actions are required to minimize inadvertent jettison of HEC. The DAD is intended for emergency use during the phases of flight that the HEC is carried or retrieved. The DAD can be used for both NHEC and HEC operations. However, because it can be used for HEC, the instructions for continued airworthiness should be carefully reviewed and documented. The DAD can be operated by the pilot from a primary control or, after a command is given by the pilot, by a crewmember from a remote location. If the backup DAD is a cable cutter, it should be properly secured, placarded and readily accessible to the crewmember intended to use it.
(8) § 29.865(c)(2) PCDS : For all HEC applications, an approved PCDS is required. The PCDS may be either previously approved or is required to be approved during certification. In either case, its installation should be approved. The PCDS is required to be reliable. The failure of the PCDS, and its attachments to the rotorcraft should be shown to be extremely improbable (i.e., 1 x 10-9 failures per flight) for all failure modes that could cause a catastrophic failure, serious injury, or fatality. All significant failure modes of lesser consequence should be shown to be improbable (i.e., 1 x 10-5 failures per flight). An acceptable method of achieving this goal is to submit and achieve approval of all of the following:
(i) A failure modes and effects analysis (FMEA) showing that all potential failure modes of the PCDS which may result in catastrophic failures, serious injuries or fatalities are extremely improbable and any less significant failures are improbable.
(ii) A repetitive test of all functi onal devices that cycles these devices at least 30 times under critical structural conditions, operational conditions, or a combination.
(iii) An environmental qualificat ion review for the proposed operating environment.
Note: PCDS designs can vary from simple single occupant “donut” lifesaving devices to relatively complex multiple occupant cages or gondolas. The purpose of the PCDS is to
Page D - 157 provide a minimum acceptable level of safety for personnel being transported outside the rotorcraft. The personnel being transported may be healthy or injured, conscious or unconscious.
(iv) TSO C167 is an approved minimum performance specification for HEC body harnesses.
(v) Static strength. The PCDS should be substantiated for the allowable ultimate load and loading conditions as determined under paragraphs d(2).
(vi) Fatigue . § 29.865(f) requires the metallic components of the PCDS to be substantiated for fatigue in accordance with § 29.571 (Reference d(14)).
(vii) Personnel safety . For each PCDS design, the applicant should submit a design evaluation that assures the necessary level of personnel safety is provided. As a minimum, the following should be evaluated.
(A) The PCDS should be easily and readily ingressed or egressed.
(B) It should be placarded for proper capacity, internal arrangement and location of occupants, and ingress and egress instructions.
(C) For door latch fail-safety, more than one fastener or closure device should be used. The latch device design should provide direct visual inspectability to assure it is fastened and secured.
(D) Any fabric used should be durable and should be at least flameresistant.
(E) Safety harnesses and belts should meet TSO C22, TSO C114, or TSO C167 requirements.
(F) Occupant retention devices and related design safety features should be used as necessary. In simple designs, rounded corners and edges with adequate strapping (or other means of HEC retention relative to the PCDS) and head supports or pads may be all the safety features that are necessary. However, in more complex PCDS designs, safety features such as seat belts, handholds, shoulder harnesses, placards, or other personnel safety standards may be required.
(viii) EMI and lightning protection . All essential, affected components of the PCDS, such as intercommunication equipment, should be protected against RF field strengths to a minimum of RTCA/DO-160 CAT Y.
(ix) Instructions for continued airworthiness . All instructions and documents necessary for continued airworthiness, normal operations, and emergency
AC 29-2C, Chg 2 4/25/06 Page D - 158 operations should be completed, reviewed, and approved during the certification process.
(x) Flotation devices . PCDS's that are intended to have a dual role as floatation devices or life preservers should meet the requirements of TSO-C13f, "Life Preservers." Also, any PCDS design to be used in the water should have a floatation kit. The kit should support the weight of the maximum number of occupants and the PCDS in the water and minimize the possibility of the occupants floating face down.
(xi) Aerodynamic considerations . Litters and other types of PCDS designs may spin, twist or otherwise respond unacceptably in flight. These designs should be structurally restrained with devices such as a spider, a harness, or an equivalent device to minimize undesirable flight dynamics.
(xii) Medical design considerations . The PCDS should be designed to the maximum practicable extent and placarded to maximize the HEC's protection from medical considerations such as blocked air passages induced by improper body configuration and excessive loss of body heat during operations. Injured or water soaked persons may be exposed to high body heat loss from sources such as rotor wash and the airstream. PCDS occupant safety from transit induced medical considerations can be greatly increased by proper design.
(9) § 29.865(c)(3) QRS Design, Installation, and Placarding: For jettisonable HEC applications, the QRS design, installation, and associated placarding should be given special consideration to assure the proper level of occupant safety.
(10) § 29.865(c)(4) Intercom Systems for HEC Operations : For all HEC operations, the rotorcraft is required to be equipped for, or otherwise allow direct intercommunication under any operational conditions among crewmembers and the HEC. For simple systems, voice or hand signals to PCDS occupants are acceptable.
In more complex systems and for RCL Class D operations, more sophisticated devices such as or two-way radios or intercoms should be employed.
(11) § 29.865(c)(5) Flight Manual Procedures : Appropriate flight manual procedures and limitations for all HEC operations should be presented. All limitations are required to be approved for all RLC class A, B, or C employing HEC. The flight manual should clearly define the method of communication between the flight crew and the HEC. These instructions and manuals should be validated during TIA flight-testing.
(12) § 29.865(c)(6) Limitations for HEC Operations: For jettisonable HEC operations, it may be required by Operations Requirements, that the rotorcraft meet the Category A engine isolation requirements of Part 29 and that the rotorcraft have One Engine Inoperative/Out of Ground Effect (OEI/OGE) hover performance capability in its approved, jettisonable HEC weight, altitude, and temperature envelope.
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(i) In determining OEI hover performance, dynamic engine failures should be considered. Each hover verification test should begin from a stabilized hover at the maximum OEI hover weight, at the requested in-ground-effect (IGE) or OGE skid or wheel height, and with all engines operating. At this point the critical engine should be failed and the aircraft should remain in a stabilized hover condition without exceeding any rotor limits or engine limits for the operating engine(s). As with all performance testing, engine power should be limited to minimum specification power. Engine failures may be simulated by rapidly moving the throttle to idle provided a ‘needle split’ is obtained between the rotor and engine RPM.
(ii) Normal pilot reaction time should be used following the engine failure to maintain the stabilized hover flight condition. When hovering OGE or IGE at maximum OEI hover weight, an engine failure should not result in an altitude loss of more than 10 percent or four (4) feet, whichever is greater, of the altitude established at the time of engine failure. In either case, sufficient power margin should be available from the operating engine(s) to regain the altitude lost during the dynamic engine failure and to transition to forward flight.
(iii) Consideration should also be given to the time required to recover (winch up and bring aboard) the Class D external load and to transition to forward flight.
This time increment may limit the use of short duration OEI power ratings. For example, for a helicopter that sustains an engine failure at a height of 40 feet, the time required to restabilize in a hover, recover the external load (given the hoist speed limitations), and then transition to forward flight (with minimal altitude loss) would likely preclude the use of 30-second engine ratings and may encroach upon the 2 ½ -minute ratings. Such encroachment into the 2 ½ - ratings is not acceptable.
(iv) For helicopters that incor porate engine driven generators, the hoist should remain operational following an engine or generator failure. A hoist should not be powered from a bus that is automatically shed following the loss of an engine or generator. Maximum two-engine generator loads should be established so that when one engine or generator fails, the remaining generator can assume the entire rotorcraft electrical load (including the maximum hoist electrical load) without exceeding approved limitations.
(v) The Rotorcraft Flight Manual (RFM) should contain information that describes the expected altitude loss, any special recovery techniques, and the time increment used for recovery of the external load when establishing maximum weights and wheel or skid heights. The OEI hover chart should be placed in the performance section of the RFM or RFM supplement. Allowable altitude extrapolation for the hover data should not exceed 2000 feet.
(13) § 29.865(d) Fli ght-test Verification Work: Flight-test verification work (or an equivalent combination of analysis and ground testing, either in conjunction with or in addition to operations rules such as Part 133 for the U.S.) that thoroughly examines the operational envelope should be conducted with the external cargo
AC 29-2C, Chg 2 4/25/06 Page D - 160 carriage device for which approval is requested (especially those that involve HEC).
The flight-test program should show that all aspects of the operations applied for are safe, uncomplicated, and can be conducted by a qualified flight crew under the most critical service environment and, in the case of HEC, under emergency condition. Flight tests should be conducted for the simulated representative NHEC and HEC loads to demonstrate their in-flight handling and separation characteristics. Each placard, marking, and flight manual supplement should be validated during TIA flight-testing.
(i) General . Flight-testing (or an equivalent combination of analysis and testing) should be conducted under the critical combinations of configurations and operating conditions for which basic type certification approval is sought. Additional combinations of external load and operating conditions may be subsequently approved under relevant operational requirements as long as the structural limits and reliability considerations of the basic certification approval are not exceeded (i.e., equivalent safety is maintained). The qualification flight-test work of this subparagraph is intended to be accomplished primarily by analysis or bench testing. However, at least one in-flight, limit load drop test should be conducted for the critical load case. If one critical load case cannot be clearly identified, then more than one drop test might be necessary. Also, in-flight tests for the minimum load case (i.e., typically the cable hook itself) with the load trailing both in the minimum and maximum cable length configurations should be conducted. Any safety-of-flight limitations should be documented and placed in the rotorcraft flight manual. In certain low-gross weight, jettisonable HEC configurations, the PCDS may act as a trailing airfoil that could result in entangling the PCDS and the rotorcraft. These configurations should be assessed on a case-by-case basis by analysis or flight-test to assure any safety-of-flight limitations are clearly identified and placed in the rotorcraft flight manual.
(ii) Separation characterist ics of jettisonable external loads. For all jettisonable RLC of any applicable cargo type, satisfactory post-jettison separation characteristics of all loads should meet the minimum criteria that follow:
(A) Immediate "clean" operation of the QRS, including "clean" separate functioning of the PQRS and BQRS.
(B) No damage to the helicopter dur ing or following actuation of the QRS and load jettisoning.
(C) A jettison trajectory clear of the helicopter.
(D) No inherent instability of the jettisonable (or just jettisoned) HEC or NHEC while in proximity to the helicopter.
(E) No adverse or uncontrollable helicopter reactions at the time of jettison.
Page D - 161 (F) Stability and control characteristics after jettison should be within the originally approved limits.
(G) No unacceptable degradati on of the helicopter performance characteristics after jettison.
(iii) Jettison requirements for jettisonable external loads. For representative cargo types (low, medium, and high density loads on long and short lines), emergency and normal jettison procedures should be demonstrated (by a combination of analysis, ground tests, and flight-tests) at sufficient combinations of flight conditions to establish a jettison envelope that should be placed in the flight manual.
(iv) QRS demonstration . Repetitive jettison demonstrations should be conducted that use the PQRS. Except, the BQRS should be utilized at least once.
(v) QRS reliability (i.e., failure modes) affecting flight performance. The FMEA of the QRS (reference d(4)) should show that any single system failure will not result in unsatisfactory flight characteristics, including any QRS failures resulting in asymmetric loading conditions.
(vi) Flight-test weight and CG locations . All flight-tests should be conducted at the extreme or critical combinations of weight and longitudinal and lateral CG conditions within the applied for flight envelope. The rotorcraft should remain within approved weight and CG limits both with the external load applied and after jettison of the load.
(vii) Jettison Envelopes . Emergency and normal jettison demonstrations should be performed at sufficient airspeeds and decent rates to establish any restrictions for satisfactory separation characteristics. Both the maximum and minimum airspeed limits and maximum decent rate for safe separation should be determined.
The sideslip envelope as a function of airspeed should be determined.
(viii) Altitude . Emergency and normal jettison demonstrations should be performed at altitudes consistent with the approvable operational envelope and with the maneuvering requirements necessary to overcome any adverse effects of the jettison.
(ix) Attitude . Emergency and normal jettison demonstrations should be performed from all attitudes appropriate to normal and emergency operational usage.
Where the attitudes of HEC or NHEC with respect to the helicopter may be varied, the most critical attitude should be demonstrated. This demonstration would normally be accomplished by bench testing.
(x) Hoist and rescue hook systems or cargo hook systems . An in-flight demonstration test of the hoist system should be conducted for helicopters designed to carry NHEC or HEC. The rotorcraft should be flown to the extremes of the applicable maneuver flight envelope and to all conditions that are critical to strength,
AC 29-2C, Chg 2 4/25/06 Page D - 162 maneuverability, stability, and control, or any other factor affecting airworthiness.
Unless a lesser load is determined to be more critical for either dynamic stability or other reasons; the maximum hoist system rated load or, if less, the maximum load requested for approval (and the associated limit load data placards) should be used for these tests. The minimum hoist system load (or zero load) should also be demonstrated in these tests.
(14) § 29.865(e ) External Loads Placards and Markings: Placards and markings should be installed next to the external load attaching means, in a clearly noticeable location, that state the primary operational limitations - specifically including the maximum authorized external load. Not all operational limitations need be stated on the placard (or equivalent markings) only those clearly necessary for immediate reference in operations. Other more detailed operational limitations of lesser immediate importance should be stated either directly in the RFM or in a RFM supplement.
(15) § 29.865(f) Fatigue Substantiation : The fatigue evaluation of § 29.571 should be applied as follows:
NOTE: The term "hazard to the rotorcraft" is defined to include all hazards to either the rotorcraft, to the occupants thereof, or both.
(i) Fatigue evaluation of NHEC applications . Any critical components of the suspended system and their attachments (such as the cargo hook or bolted or pinned truss attachments), the failure of which could result in a hazard to the rotorcraft, should include an acceptable fatigue analysis in accordance with AC 27 MG 11, paragraph e.
(ii) Fatigue evaluation of HEC applications . The entire PCDS and its attachments should be reviewed on a component-by-component basis to determine which, if any, components are fatigue critical or damage intolerant. These components should be analyzed or tested (per AC 27 MG 11, AC 29 MG 11, or other equivalent methods) to assure their fatigue life limits are properly determined and placed in the limited life section of the maintenance manual.
(16) Other Considerations
(i) Agricultural Installation (AI): AI's can be approved for either jettisonable or non-jettisonable NHEC or HEC operations as long as they meet relevant certification and operations requirements and follow appropriate compliance methods.
However, most current AI designs are external fixtures (see definition) - not external loads. External fixtures are not approvable as jettisonable external cargo because they do not have a true payload (see definition), true jettison capability (see definition), or a complete QRS. Many AI designs can dump their solid or liquid chemical loads by use of a "purge port" release over a relatively long time period (i.e., greater than 30 seconds).
This is not considered true jettison capability (see definition) since the external load is not released by a QRS and since the release time span is typically greater than
Page D - 163 30 seconds (reference c(20) and d(7)). Thus, these types of AI's should be approved as a non-jettisonable external load. However, other designs that have the entire AI (or significant portions thereof) attached to the rotorcraft, that have short time frame jettison (or release) capability provided by a QRS that meets the definitions herein and that have no post-jettison characteristics that would endanger continued safe flight and landing may be approved as a jettisonable external load. For example, if all the relevant criteria are properly met, a jettisonable fluid load can be approved as a NHEC external cargo. AC 29 MG 5 discusses other AI certification methodology.
(ii) External Tanks: External t ank configurations that have true payload (see definition) and true jettison capability (see definition) should be approved as jettisonable NHEC. External tank configurations that have a true payload capability but do not have true jettison capability should be approved as non-jettisonable NHEC. An external tank that has neither a true payload capability nor true jettison capability is an external fixture; it should not be approved as an external load under § 29.865. If an external tank is to be jettisoned in flight, it should have a QRS that is approved for the maximum jettisonable external tank payload and is either inoperable or is otherwise rendered reliable to minimize inadvertent jettisons above the maximum jettisonable external tank payload.
(iii) Logging Operations: These operations are very susceptible to low-cycle fatigue because of the large loads and relatively high load cycles that are common to this industry. It is recommended that load-measuring devices (such as load cells) be used to assure that no unrecorded overloads occur and to assure that cycles producing high fatigue damage are properly considered. Cycle counters are recommended to assure acceptable cumulative fatigue damage levels are identifiable and are not exceeded. As either a supplementary method or alternate method, maintenance instructions should be considered to assure proper cycle counting and load recording during operations.
(17) Noise Certification : 14 CFR 36 is the noise certification standard.
Section 36.1(a)(4) specifically exempts helicopters that are designed exclusively for agricultural work, carrying firefighting materials, or external loads activity from the noise standards. Section 21.93(b)(4) also contains specific information regarding external loads and what configurations do not constitute an acoustical change.
(18) Instructions for Continued Airworthiness . Maintenance manuals (and RFM supplements) developed by applicants for external load applications should be presented for approval and should include all appropriate inspection and maintenance procedures. The applicant should provide sufficient data and other information to establish the frequency, extent, and methods of inspection of critical structure, systems and components. This information is required by § 29.1529 to be included in the maintenance manual. For example, maintenance requirements for sensitive QRS squibs should be carefully determined, documented, approved during certification, and included as specific mandatory scheduled maintenance requirements that may require either "daily" or "pre-flight" checks (especially for HEC applications).
AC 29-2C, Chg 2 4/25/06 Page D - 164
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SUBPART D - DESIGN AND CONSTRUCTION
MISCELLANEOUS (DESIGN AND CONSTRUCTION)
AC 29.871. § 29.871 LEVELING MARKS .
a. Explanation . Reference marks are required for leveling the rotorcraft on the ground. These marks are necessary for accurate determination of weight and balance effects, particularly after modifications to the basic rotorcraft.
b. Procedures .
(1) Reference marks are sometimes pr ovided in pairs, one high in the cabin and one low. The plumb weight is suspended from the high mark by an appropriate mechanical attachment, and the lower mark is used to level the rotorcraft by centering the plumb weight. The lower reference mark should be a raised or depressed target symbol and shall be applied to a permanent structural component or permanently attached plate in a readily accessible location. Seat tracks, floors, or door sills which are attached with permanent fasteners are typical locations.
(2) Horizontal reference marks for support of bubble levels may also be used, particularly for smaller rotorcraft.
(3) Proper reference should be made to i dentify the leveling marks or points on the rotorcraft. Design provisions should be made to ensure these locations are not obscured by equipment, fairings, repair, or rework.
AC 29.873. § 29.873 BALLAST PROVISIONS .
a. Explanation .
(1) This rule requires that ballast prov isions prevent inadvertent ballast shifting while in flight or as a result of a landing. Shifting of the ballast may cause a hazardous change in the center of gravity thereby affecting rotorcraft controllability.
(2) Other rules noted here allow removable and fixed ballast and require markings or placards to prevent overloading the ballast installation.
(i) Section 29.29 specifies that the rotorcraft empty weight will include any fixed ballast. Section 29.31 allows the use of removable ballast to comply with the flight requirements. However, ballast may not be adjusted (moved, reduced or increased) in flight.
(ii) Section 29.1541 requires c onspicuous and durable markings or placards. Section 29.1557 requires placards stating allowable maximum weight, distributed loading, if necessary, and other appropriate limitations for ballast installation.
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(3) Section 29.1583(c) concerns Roto rcraft Flight Manual instructions and information about removable ballast or loading information. The instructions must be included in the operating limitations section of the flight manual to allow ready observance of the limitations.
b. Procedures .
(1) The ballast installation may be subst antiated by analysis or by static test.
The design ultimate load may be derived from flight, landing, or minor crash conditions load factor specified in the rules. Substantiation by analysis will require use of the fitting factor prescribed by § 29.625 where appropriate. If static tests are to be conducted, a test plan should be prepared, submitted for evaluation and agreed upon prior to the test.
(2) Ballast installations in the aft part of the fuselage and tail boom may be subject to significant landing condition angular inertia load factors as well as the usual linear load factors.
(3) Substantiation methods and proc edures acceptable for the airframe substantiation may be used for the ballast installation as well.
(4) Removable ballast will require attent ion to assure the ballast is secured easily and properly and will remain secured under the appropriate ballast design load factor requirements. The flight manual instructions should be evaluated for compliance with § 29.1583(c) by flight test and airframe personnel.
(5) The installation must be designed and placarded or marked for the maximum allowable ballast load and for other appropriate loading limits. Normally compliance with § 29.1541 is accomplished with a drawing review by airframe personnel along with an EMDO compliance and conformity inspection. An additional compliance inspection by airframe personnel can be conducted if desired.
AC 29.877. § 29.877 ICE PROTECTION .
NOTE: § 29.877 was removed and replaced by § 29.1419 in Amendment 29-21. This material is retained since this is one way to show compliance with § 29.877.
a. Background .
(1) In March 1984, the FAA/AUTHORIT Y for the first time certificated a rotorcraft for flight into known icing conditions. Several other manufacturers are pursuing designs for icing flight capability with certification planned for 1985 or 1986.
(2) Most rotorcraft icing technology has been developed for military rotorcraft.
The only U.S. military rotorcraft equipped and approved for flight into icing conditions is the UH-60A (Blackhawk). The UH-60A is limited to supercooled cloud conditions where