AC 29-2C, Chg 7 2/4/2016 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 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.
When recognized good practices for such installation are applied, an analysis may be sufficient to highlight that the maximum possible pulse generated into the squib circuit will have an energy contents' orders of magnitude below the squib no fire energy. If insufficient data is available for installation and/or squib no fire energy, 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.
(viii) Section 27.865(c)(3) Placarding and marking. For jettisonable HEC applications, the associated QRS placarding should be given special consideration to assure the proper level of occupant safety.
(8) Cargo hooks or equivalent devices and their related systems. All cargo hooks or equivalent devices should be approved to acceptable aircraft industry standards.
The applicant should present these standards, and any related manufacturer’s certificates of production or qualification as part of the approval package.
(i) General. Cargo hook systems should have the same reliability goals and should be functionally demonstrated under critical loads for NHEC and HEC, as appropriate. All engagement and release modes should be demonstrated. If the hook is used as a quick-release device, then release of critical loads should be demonstrated under conditions that simulate maximum allowable bank angles and speeds and any other critical operating conditions. Demonstration of any re-latching features and any safety or warning devices should also be conducted. Demonstration of actual in-flight emergency quick-release capability may not be necessary if the quick-release capability can be acceptably simulated by other means.
Notes: Cargo hook manufacturers specify particular shapes, sizes, and cross sections for lifting eyes to assure compatibility with their hook design (e.g., Breeze Eastern Service Bulletin CAB-100-41). Experience has shown that, under certain conditions, a load may inadvertently hang up because of improper geometry at the hook-to-eye interface that will not allow the eye to slide off an open hook as intended.
For both NHEC and HEC designs, the phenomena of hook dynamic roll out (inadvertent opening of the hook latch and subsequent release of the load) Page D - 156
should be considered to assure that QRS reliability goals are not compromised. This is of particular concern for HEC applications. Hook dynamic roll-out occurs during certain ground handling and flight conditions that may allow the lifting eye to work its way out of the hook.
Hook dynamic roll-out typically occurs when either the RLCs sling or harness is not properly attached to the hook, is blown by down draft, is dragged along the ground or through water; or is otherwise placed into the dangerous hookto-eye configuration.
The potential for hook dynamic roll-out can be minimized in design by specifying particular hook-and-eye shape and cross-section combinations.
For non-jettisonable RLCs, a pin can be used to lock the hook keeper in place during operations.
Some cargo hook systems may employ two or more cargo hooks for safety.
These systems are approvable. However, loss of any load by a single hook should be shown to not result in loss of control of the rotorcraft. In a dual hook system, if the hook itself is the quick-release device (i.e., if a single release point does not exist in the load path between the rotorcraft and the dual hooks), the pilot should have a dual PQRS that includes selectable, colocated individual quick releases that are independent for each hook used. A BQRS should also be present for each hook. For cargo hook systems with more than two hooks, either a single release point should be present in the load path between the rotorcraft and the multiple hook system, or multiple PQRS and BQRSs should be present.
(ii) Jettisonable cargo hook systems. For jettisonable applications, each cargo hook - (A) Should have a sufficient amount of slack in the control cable to permit cargo hook movement without tripping the hook release.
(B) Should be shown to be reliable.
(C) For HEC systems, unless the cargo hook is to be the primary quick-release device, each cargo hook should be designed so that operationally induced loads cannot inadvertently release the load. For example, a simple cargo hook should have a one-way, spring-loaded gate (i.e., "snap hook") that allows load attachment going into the gate but does not allow the gate to open (and subsequently lose the HEC) when an operationally induced load is applied in the opposite direction.
For HEC applications, cargo hooks that also serve as a quick-release device should be carefully reviewed to assure they are reliable.
(iii) Other load release types. In some current configurations, such as those used for high line (or long line) operations, a load release may be present that is not on Page D - 157
AC 29-2C, Chg 7 2/4/2016 the rotorcraft but is a remote release system. The long lines allow the pilot to not release the line itself during repetitive loading operations. Examples are a tension release device that lets out line under an operationally induced load, a personal rope cutter or dedicated switches at the pilot controls. The release of the load through the secondary hook on a long line presents additional risks due to the possibility of the long line to impact the tail or main rotor after a release due to its elasticity. These devices are acceptable if the:
(A) off-rotorcraft release is considered a "third release". This type of release is not a substitute for a required release (i.e., PQRS or BQRS);
(B) cargo hook release and the long line release are placed on the primary controls in a way to avoid confusion during operation. One example of compliance would be to place the cargo hook release on the cyclic and the long line release on the collective to avoid any possible confusion in the operation;
(C) RFM or RFMS includes a description of the new control in the cockpit and its function and an RFM or RFMS note to the pilot is included indicating that the helicopter hook emergency release procedures are fully applicable;
(D) release meets the same certification reliability criteria adopted for the helicopter certified hook, as well as other relevant requirements of § 29.865 and the methods of this guidance or equivalent methods; and (E) release has no operational or failure modes that would affect continued safe flight and landing under any operations, critical failure modes, conditions, or combination of either. The following points shoul d be considered:
(1) The long line should not be of an elastic material allowing spring up when unloaded or elevated dynamics when loaded.
(2) The long line should have a residual weight allowing its release from the helicopter hook when the long line is unloaded.
(3) The RFM or RFMS should include all operating procedures to ensure that the long line does not impact the rotors after cargo release and during unloaded flight phases.
(4) The hook should be designed to minimize inadvertent activation.
An example may be a protective device (cage) around the locking mechanism of the long line hook.
(5) A means should be provided to prevent fouling of cables in the event of rotation of the external load. An example may be the inclusion of a swivel or slipring.
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(6) Installation of long line provided with electrical wiring to control the hook will generally represent a new electromagnetic coupling path from external area to the internal systems that may not have been considered for type certification. As such, the impact of this installation on the coupling to helicopter systems, due to direct connection or cross talk to wirings, shall be addressed in accordance with § 29.1317,
29.1316 and 29.610 as a minimum.
(9) Cable
(i) Cable attachment. Either the cable should be positively attached to the hoist drum and the attachment should have ultimate load capability or equivalent means should be provided to minimize the possibility of inadvertent, complete cable unspooling.
(ii) Cable length and marking. A length of cable nearest the cable's attachment to the hoist drum should be visually marked to indicate to the operator that the cable is near full extension. The length of cable to be marked is a function of the maximum extension speed of the system and the operator's reaction time needed to prevent cable run out. It should be determined during certification demonstration tests.
In no case should the length be less than 3-1/2 drum circumferences.
(iii) Cable stops. Means should be present to automatically stop cable movement quickly when the system's extension and retraction operational limits are reached.
(10) Section 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. A PCDS may also be approved after the external load system certification. Including a limitation in the RFM or RFMS requiring an approved PCDS will permit more flexibility for operators to utilize their own approved PCDS (see paragraph d.(4) of this guidance). In either case, its compatibility with the helicopter should be approved.
Note: PCDS designs can vary from simple single occupant lifesaving devices to relatively complex multiple occupant cages or gondolas. The purpose of the PCDS is to 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.
(i) TSO C167 is an approved minimum performance specification for HEC body harnesses.
(ii) Static strength. The PCDS should be substantiated for the allowable ultimate load and loading conditions as determined under paragraph d.(6) above.
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AC 29-2C, Chg 7 2/4/2016
(iii) Fatigue. The PCDS should be substantiated for fatigue as determined under paragraph d.(6) above.
(iv) 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 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.
(v) 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 Document DO-160 Category Y.
(vi) Instructions for continued airworthiness. All instructions and documents necessary for continued airworthiness, normal operations, and emergency operations should be completed, reviewed, and approved during the certification process. There should be clear instructions to describe when the PCDS is no longer serviceable and should be replaced in part or as a whole due to wear, impact damage, fraying of fibers, other forms of degradation. In addition, any life limitations resulting from compliance with paragraphs d.(10)(ii) and (iii) should be provided.
(vii) Flotation devices. PCDSs 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.
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(viii) Flight testing. It should be shown by flight tests that the device is safely controllable and maneuverable during all requested flight regimes without requiring exceptional piloting skill. The flight tests should entail the PCDS weighted to the most critical weight. 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.
(ix) Medical design considerations. The PCDS should be designed to the maximum practicable extent and placarded to maximize the HECs 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.
(x) Hoist operator safety device. W hen hoisting operations require the presence of a hoist operator on board, appropriate provisions shall be provided to allow the hoist operator to perform his task safely. These provisions shall include an appropriate hoist operator restraint system. This safety device is typically composed of a safety harness and a strap attached to the cabin used to adequately restrain the hoist operator inside the cabin while operating the hoist. For certification approval, t he hoist operator safety device should comply with § 29.561(b)(3) for personnel safety. The applicant should submit a design evaluation that assures the necessary level of personnel safety is provided. The safety harness and strap should meet TSO C22g, TSO C114, or TSO C167 requirements; however, as a minimum, the following should be evaluated:
(A) The strap attaching point on the body harness should not be located in the back of the hoist operator due to safety issues in case of a fall or crash.
(B) The safety device should be designed to be adjustable so that the strap is tightened behind the hoist operator.
(C) The strap might include a QRS including a DAD to allow hoist operator detaching from cabin in emergency conditions (e.g., crash).
(D) The safety device should be easily and readily ingressed or egressed.
(E) It should be placarded for proper capacity and lifetime limitation.
(F) Any fabric used should be durable and should be at least flame resistant.
(11) Section 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 Page D - 161
AC 29-2C, Chg 7 2/4/2016 intercommunication under any operational conditions among crewmembers and the HEC. An intercommunications system may also be approved after the external load system certification as operators are standardizing communications equipment within their fleet for safety benefits. In lieu of an intercommunication system being provided as part of the external load system, this onus may be moved onto the operator through a limitation may be placed in the RFM or RFMS (see paragraph d.(4) of this guidance).
(12) Section 29.865(c)(6) HEC Operations Requiring Category A Rotorcraft. For jettisonable HEC operations, it may be required by Operations Requirements, § 133.45(e), that the rotorcraft meet the category A engine isolation requirements of part 29 and that the rotorcraft have OEI hover performance capability OGE in its approved, jettisonable HEC weight, altitude, and temperature envelope.
(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 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) Pilot reaction times used following the engine failure to maintain the stabilized hover flight condition will depend on the environment in which such operations are planned. For HEC operations planned for day visual meteorological conditions (VMC), normal pilot reaction times are acceptable. Recent certification projects for HEC operations planned to take place overwater at night while in VMC or in instrument meteorological conditions (IMC) required greater pilot reaction times. 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 then to transition to forward flight.
(iii) Consideration should also be given to the time required to recover (reel in and bring aboard) the HEC and then 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 stabilize the hover at the original hover height, recover the HEC (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. In accordance with the intent of OEI power ratings, recovery and transition procedures shall not utilize more than one iteration of either a 30-second / 2-minute power combination or a 2½-minute rating.
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(iv) For helicopters that incorporate 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 RFM or RFMS 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.
Engine failure procedures that permit safe recovery of the HEC and safe fly-away capability shall be included in the RFM or RFMS The OEI hover chart should be placed in the performance section of the RFM or RFMS. Allowable altitude extrapolation for the hover data should not exceed 2000 feet. The following statement (modified appropriately) should be included to indicate to operators which charts are applicable to these HEC operations.
• For external load equipment installations specifically intended for HEC applications requiring the use of Transport Category A rotorcraft, OEI hover performance data, and procedures may be found in Figures/Charts/Section XX - YY…
(13) Section 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 RFMS.
(14) Other Considerations.
(i) Agricultural Installation (AI). AIs 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 30 seconds (see paragraph c.(21)). Thus, these types of AIs shoul d 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 Page D - 163
AC 29-2C, Chg 7 2/4/2016 (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. Section AC 29 MG 5 of this AC discusses other AI certification methodology.
(ii) External Tanks. External tank 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.
(15) Noise Certification. 14 CFR part 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.
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SUBPART D - DESIGN AND CONSTRUCTION
MISCELLANEOUS 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 accu rate determination of weight and balance effects, particularly after modifications to the basic rotorcraft.
b. Procedures.
(1) Reference marks are sometimes provided 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 identify 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 provisions 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 conspicuous 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 Rotorcraft 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 substantiated 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 procedures acceptable for the airframe substantiation may be used for the ballast installation as well.
(4) Removable ballast will require attention to assure the ballast is secured easily and properly and will remain secured under the appropriate ballast design load factor requirements. The f light 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/AUTHORITY 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 Page D - 166
liquid water content (LWC) does not exceed 1.0gm/m3 and outside air temperature (OAT) is not below -20° C.
(3) Many rotorcraft operators have voiced a high priority on obtaining rotorcraft approved for operation in icing conditions.
(4) The icing characteristics envelope of FAR Part 25, Appendix C, has served as a satisfactory design criteria for fixed-wing operations for two decades. The envelope, as presented, extends to 22,000 feet with possible extents to 30,000 feet but does not present icing severity as a function of altitude. At the time the envelope was derived, it was assumed that all transport category airplanes would operate to at least 22,000 feet. For present state-of-the-art rotorcraft, this assumption is not valid. As such, an altitude limited icing envelope based on the same data used to derive the Part 25, Appendix C, and the Part 29, Appendix C, envelopes is presented as an alternate to the full icing envelope. In addition, a second icing envelope which effectively characterizes supercooled clouds from ground level to 10,000 feet is presented as a second alternative to the Part 29, Appendix C, envelope. The second altitude limited envelope described in reference 386d(2) was derived from recent additional airborne measurements.
b. Explanation.
(1) General.
(i) The discussion in this paragraph pertains generally to certifications to the full icing envelope of Part 29, Appendix C, within the altitude limitations of the rotorcraft or to one of the altitude limited icing envelopes based on a 10,000-foot pressure altitude limit. The actual icing envelope considered may be further restricted based on the actual pressure attitude envelope for which certification is requested. It envisions certification with full ice protection systems (rotor blades, windshields, engine inlets, stabilizer surfaces, etc.). With the exception of pilot controllable variables such as altitude and airspeed, limited certification (either in terms of icing envelope or protection capability) is not envisaged at this time due to the difficulty in forecasting the severity of icing conditions, relating the effects of the forecasted conditions to the type of aircraft, and relating the effects of reported icing among various types of aircraft, particularly between fixed and rotary-wing aircraft. In addition, with a limited protection capability, viable escape options may not be operationally available if limitations are exceeded.
(ii) The discussion in this paragraph, regarding rotor blade ice protection, is oriented primarily toward electrothermal rotor deicing systems, since these have the most widespread acceptance and projected use within the industry. Also, most of the testing and research into rotorcraft ice protection to date has been conducted with this type of system. Research is continuing with other types of systems such as anti -icing fluid systems, and information will be added to address certification of these as necessary. It should also be noted that most of the rotorcraft icing experience Page D - 167