13 drainage procedure instructions should be provided in the appropriate manual. Similarly, placement of the pressure sensor(s) should be evaluated to prevent misleading boot inflation indications.
(2) Electric Propeller Boots. When flying in dry air, the systems should be monitored to confirm proper function. It is suggested that system current, brush block voltage (between each input brush and the ground brush), and system duty-cycles be monitored to ensure that proper power is applied to the deicers. If not furnished by the manufacturer, surface temperature measurements may be made during dry air tests. These surface temperature measurements are useful for correlating analytically predicted dry air temperatures with measured temperatures or as a general indicator that the system is functioning and that each deicer is heating.
The system operation should be checked throughout the full r.p.m. and propeller cyclic pitch range expected during icing flights. Any significant vibrations should be investigated.
Consideration should be given to the maximum temperatures that a composite propeller blade may be subjected to when the deicers are energized. It may be useful to monitor deicer bond-side temperatures. When performing this evaluation, the most critical conditions should be investigated
(e.g., this may occur on the ground (propellers non-rotating) on a hot day with the system inadvertently energized).
(3) Electric Windshield Anti-Ice. Dry air flight tests should be conducted in support of the systems design, as required. Inner and outer windshield surface temperature evaluations of the protected area may be needed to support thermal analyses. Thermal analysis should substantiate that the surface temperature is sufficient to maintain anti-icing capability without causing structural damage to the windshield. In the case of add-on plates, temperatures of the basic airplane windshield, inside and out, may also be needed, particularly with pressurized airplanes.
An evaluation of the visibility, including distortion effects through the protected area, should be made in both day and night operations. In addition, the size and location of the protected area should be reviewed for adequate visibility, especially for approach and landing conditions. A probable single failure of a transparency heating system should not adversely affect the integrity of the airplane cabin or create a potential danger of fire.
(4) Pitot-Static and Static Pressure Sources. If the aerodynamic configuration of either the pitot or the static source(s) differs from that of the basic airplane, then airspeed and altimeter system calibrations should be evaluated for compliance with the certification requirements. A component surface temperature evaluation may be necessary to verify thermal analyses. Section
23.1325(b) requires that static pressure port design or location should be such that the correlation between air pressure in the static pressure system and true ambient atmospheric static pressure is not altered when the airplane encounters icing conditions. Section 23.1325(b)(3) allows an antiicing means or an alternate source of static pressure may be used in showing compliance with the requirement.
(5) Stall Warning and Angle-of-Attack Sensors. Ice could form on these sensors if these devices are not protected. When the icing approval requires installation of new or modified sensors, that sensor's function should be evaluated for compliance with the certification requirements. These sensors may not require heat for ice protection if substantiated by analyses. A surface temperature evaluation may be necessary to verify thermal analyses. Consideration should be given to ice formations on the airframe in the vicinity of the sensor mounting location that may affect the sensor’s operation.
(6) Pitot Tube. Section 23.1323 requires a heated pitot tube or an equivalent means of preventing malfunction due to icing. Section 23.1326 requires a pitot tube heat indicating system if a flight instrument pitot heating system is installed to meet ice protection requirements.
(7) Fluid Anti/Deice Systems. Dry air testing should include evaluation of fluid flow paths to determine that adequate and uniform fluid distribution over the protected surfaces is achieved. Means of indicating fluid flow rates, quantity remaining, etc., should be evaluated to determine that the indicators are plainly visible to the pilot and that the indications provided can be effectively read. An accessible shutoff should be provided in systems using flammable fluids. The fluid anti-ice/deice systems may be used to protect propellers and windshields, as well as leading edges of airfoils. The fluid for windshield fluid anti-ice systems should be tested to demonstrate that it does not become opaque at low temperature.
(8) Compressor Bleed Air Systems. The effect of any bleed air extraction on engine and airplane performance should be examined and shown in the AFM performance data. The surface heat distribution analysis should be verified for varying flight conditions including climb, cruise, hold, and descent. A temperature evaluation may be necessary to verify the thermal analyses.
(9) Ice Detection Light(s). Ice detection lights may be necessary if operations are dependent upon observing ice accumulations at night (§ 23.1419(d)). Ice detection lights should be evaluated both in and out of clouds during night flight to determine that adequate illumination of the component of interest is available without excessive glare, reflections or other distractions to the flight crew. These tests may be conveniently accomplished both in and out of clouds during dry air tests. Use of a hand-held flashlight for ice detection is not acceptable. As described in § 23.1419(d), “The Airplane Flight Manual or other approved manual material must describe the means of determining ice formation and must contain information for the safe operation of the airplane in icing conditions.”
b. Dry Air Tests with Artificial Ice Shapes. The installation of artificial ice shapes allows airplane performance and handling characteristics to be evaluated in stable dry air conditions with the critical ice shape being held constant (i.e., no change of ice accretion due to erosion, shedding, etc., that can occur with natural ice shapes). Dry air flight tests with artificial ice shapes installed also result in a considerable reduction in the amount of flight testing that would otherwise be required to accumulate the test ice shapes, and then evaluate their effects on airplane performance and handling characteristics in stable air. Dry air tests with artificial ice shapes can be hazardous if
15 not approached safely; therefore, the dry air flight test evaluation should be performed using a build-up technique, considering increases in spanwise coverage and dimensions of artificial ice shapes prior to full span ice shape tests The shape and texture of artificial ice shapes should be developed and substantiated using methods found acceptable to the FAA. Common practices include: use of computer codes, flight in measured natural icing conditions, icing wind tunnel tests, and flight in a controlled simulated icing cloud (e.g., behind an icing tanker). The validity of the ice shape predictions from analytical computations, simulated icing flight tests or icing tunnel tests should be confirmed by flight tests in natural icing. These predictive methods should be conservative and should address the conditions associated with the icing envelope of Part 25, Appendix C, that are critical to the airplane's performance and handling qualities in critical phases of the airplane's operational envelope, including climb, cruise, descent, holding pattern, approach, and landing.
Considerations should be given to the type of ice protection systems (e.g., mechanical, fluid, thermal, or hybrid) to the most adverse ice conditions (shape or shapes, texture, location, and thickness) for the relevant aerodynamic characteristics for the following, where appropriate:
1) delayed turn on; 2) inter-cycle conditions; 3) failure conditions; and 4) residual ice. See Item 11d.
The effect of the ice shapes on stall speeds and airplane climb performance should be determined. Stall warning margins and maneuvering capability should also be evaluated.
Operating speeds, stall warning speeds, and AFM performance information should be adjusted, if necessary, to provide acceptable performance capability and stall warning margins. The computation of the effects of ice on AFM performance should include the loss of engine power or thrust resulting from the applicable operating mode of the ice protection system.
Handling characteristics should be investigated to determine that an acceptable level of safety exists. The results of these tests may be used in preparing specific AFM operating procedures and limitations for flight in icing conditions.
c. Icing Flight Tests. Flight tests in measured natural icing and the use of simulated icing tools such as icing tankers and icing wind tunnels are normally employed to demonstrate that the ice protection system performs under flight conditions as the analysis or other tests indicated. They are also used to confirm the analyses used in developing the various components (e.g., ice detectors) and ice shapes and, in the case of natural icing tests, to confirm the conclusions reached in flight tests conducted with artificial ice shapes. Testing should be accomplished at various points in the icing envelope of Part 25, Appendix C, to verify the airplane's ability to safely operate throughout that icing envelope.
(1) Instrumentation. Sufficient instrumentation should be planned to allow documentation of important airplane, system and component parameters, and icing conditions encountered. The following parameters should be considered:
(i) Altitude, airspeed, and engine power.
(ii) Static air, engine component, electrical generation equipment, surface, interlaminate, and any other key temperatures that could be affected by ice protection equipment, by ice accumulation or other key temperatures that are necessary for validation of analyses.
(iii) Liquid water content can be measured using a hot-wire anemometer based instrument, calibrated drum, or other equivalent means.
(iv) Median volumetric droplet diameter can be approximately determined by using a drop snatcher to expose a gelatin oil or soot slide and then measuring the resultant impact craters, or by use of more sophisticated equipment such as a laser based droplet measuring and recording instrument.
(2) Simulated Icing. Testing in simulated icing environments such as icing tunnels or behind icing tankers represents one way to predict the ice protection capabilities of individual elements of the ice protection equipment. Due to the limited volume of the simulated icing environment, testing is usually limited to components having small exposed surfaces such as heated pitot tubes, antennas, air inlets including engine induction air inlets, empennage, and other surfaces having small leading edge radii and windshields. Small components are more sensitive to the higher accumulation rates associated with high liquid water content and large droplet size. These conditions are easily simulated and not frequently encountered in natural icing flight tests.
A simulated icing exposure may be obtained by the use of onboard spray nozzles forward of the component under examination or by flying the test airplane in the cloud generated by an icing tanker. Simulated icing clouds should be measured to ascertain that they contain the required cloud metrics (droplet sizes, liquid water content, temperature, etc.) and accretions from these clouds can be used to show compliance with icing criteria. For those components where small droplet sizes are critical, simulated icing tests should be evaluated to ensure the conditions of concern are accurately simulated.
(3) Natural Icing. Flight tests in natural icing conditions are necessary to demonstrate the acceptability of the airplane and ice protection system for flight in icing conditions. AC 20-73 (Items 25f and 25g(1)) provides additional information that would be useful when establishing a natural icing flight test program. At least one exposure to icing conditions should be obtained within Part 25, Appendix C, continuous maximum envelope. The exposure should be sufficiently stabilized to obtain valid data. It is often difficult to obtain temperature stabilization in brief exposures. Additional exposures may be required to allow extrapolation to the envelope critical conditions by analysis. Test data obtained during these exposures may be used to validate the analytical methods used and the results of any preceding simulated icing tests.
17 Past experience has shown that flight testing in natural intermittent maximum icing conditions may be hazardous due to accompanying severe turbulence and possible hail encounters that may extensively damage the test airplane. When design analyses show that the critical ice protection design points (i.e., heat loads, critical shapes, accumulation, and accumulation rates, etc.) are adequate under these conditions, and sufficient ground or flight test data exists to verify the analysis, then hazardous flight testing should be avoided.
During natural icing flight tests, ice accumulation on unprotected areas should be observed and documented. Remotely located cameras either on the test airplane or on a chase airplane have been used to document ice accumulations on areas that cannot be seen from the test airplane’s flight deck or cabin. Sufficient data should be taken to allow correlation with dry air tests using artificial ice shapes. Handling qualities should be subjectively reviewed and determined to be in general correlation with those found in dry air testing. Decreases in performance observed during natural icing flight tests should be compared to the decreases observed during flight tests with artificial ice shapes. In addition, flying qualities and performance should be qualitatively evaluated with the ice accumulations existing just prior to operation of deice (as opposed to anti-ice) components. The ice protection systems are to be activated by the flight crew in accordance with approved AFM procedures when icing conditions exist; however, for anti-ice components, tests should be conducted that simulate inadvertent icing encounters in which the pilot may not recognize that the airplane is about to enter an icing condition and the anti-ice component may not be activated until actual ice build-up is noticed.
A delayed ice accumulation event of 30 seconds to 2 minutes has been used in these tests to simulate the flight crew's failure to recognize an icing condition. For the delayed ice accumulation time event, consideration should be given to the icing conditions, the icing recognition means available, recommended crew procedures, and ice protection system performance of the particular aircraft. Handling qualities should remain acceptable to the test pilot and the airplane should be capable of operating safely.
All systems and components of the basic airplane should continue to function as intended when operating in an icing environment. Some considerations are:
(i) Engine and equipment such as generator under maximum ice protection load cooling should be monitored during icing tests and be found acceptable for this operation.
(ii) Engine alternate induction air sources should remain functional in an icing environment.
(iii) Fuel system venting should not be affected by ice accumulation.
(iv) Retractable landing gear should be available for landing following an icing encounter. Gear retraction should not result in an unsafe indication because of ice accretion.
(v) Ice shedding from components including antennas of the airplane should cause no more than cosmetic damage to other parts of the airplane, including aft-mounted engines and propellers.
(vi) With residual ice accumulations on the airplane, acceptable stall warning (aerodynamic or artificial) and stall protection system if installed should be provided. Biasing of the stall warning and stall protection system if installed may be required to achieve acceptable margins to stall.
(vii) Ice detection cues that the pilot relies on for timely operation of ice protection equipment should be evaluated in anticipated flight attitudes.
(viii) Ice detection lights should be evaluated in natural icing or simulated night conditions (darkened hangar) to verify that they illuminate ice build-up areas and that they are adequate under the conditions encountered.
(ix) Primary and secondary flight control surfaces should remain operational after exposure to icing conditions. Demonstrate that aerodynamic balance surfaces are not subject to icing throughout the airplane's operating envelope (weight, center of gravity, and speed), or that any ice accumulation on these surfaces does not interfere with or limit actuation of the control for these surfaces including retraction of flaps for a safe go around from the landing configuration.
d. Performance and Handling Qualities. Airplane performance and handling qualities are degraded by ice accumulations in various ways depending upon type, shape, size, and location of these accumulations. Because of these variations in degradation, it is difficult to establish a standard method of demonstrating such degradations. However, certain minimum tests, as suggested below, should be used to demonstrate that the airplane does not have unsafe features or characteristics that prevent it from being capable of operating safely in Part 25, Appendix C, icing envelope. If numerous unprotected areas exist, the weight and center of gravity effects of the ice formations should also be evaluated.
In accordance with § 23.1419(a), "capable of operating safely" means that airplane performance, controllability, maneuverability, and stability must not be less than required in Part 23, Subpart B.
The FAA and the Joint Aviation Authorities (JAA) are harmonizing the performance and handling qualities of Part 25. The Aviation Rulemaking Advisory Committee (ARAC) Flight Test Harmonization Working Group will complete the harmonization project to standardize performance, handling requirements, and additional guidance material for certification of Part 25/Joint Aviation Requirements 25 (JAR 25) airplanes to safely operate in the icing conditions of Appendix C. These performance and handling qualities issues will be considered for Part 23 requirements and guidance information (future rulemaking and AC’s that are being promulgated by the ARAC) where appropriate. The following guidelines are intended for certification basis prior to Amendment 23-43:
(1) Performance. For normal, utility, and acrobatic category airplanes, performance losses are normally demonstrated in icing conditions only for the all engines operating condition;
however, for commuter category airplanes, which have takeoff and landing weight limitations based on one engine inoperative climb performance, testing for one engine inoperative performance loss is appropriate. Climb performance losses should be established either by flight tests or by a conservative analysis acceptable to the FAA certifying office. Artificial ice shapes used for performance evaluation should be those critical shapes as found under the conditions in the icing envelope of Part 25, Appendix C, and the critical operating conditions under which such performance is expected. The following performance loss determinations are normally considered minimum:
(i) Section 23.65, Climb: All Engines Operating. Climb performance losses due to ice formation for the configuration defined in § 23.65 are normally not appropriate below 400 feet since the airplane should not depart with ice on the airplane. However, takeoff climb performance should be determined considering any losses associated with operating anti-ice/deice equipment since that equipment could be utilized for takeoff into an icing environment.
(ii) Section 23.67(e) (1), (2) and (3) (As of Amendment 23-43), Climb: One Engine Inoperative. Climb performance losses should consider related power extractions, additional icing drag, and any required changes to operational climb speeds for at least the following:
(A) One engine inoperative takeoffs to 400 feet are conducted without ice. Above 400 feet ice should be considered;
(B) Climb with one engine inoperative in the en route configuration; and (C) Climb with one engine inoperative in the approach configuration.
(iii) Section 23.75, Landing. The landing performance should be calculated or measured considering the effects of critical ice accumulations upon landing. Minimum speeds, landing configuration, and landing distance (based on increased stall speeds) degradation should be established.
(iv) Section 23.77, Balked Landing. For normal, utility, and acrobatic category airplanes, the airplane with ice accumulations and all icing systems operational (e.g., bleed air systems) should meet the all engine minimum climb requirements on a 32 °F day at sea level as is required on the non-iced (icing systems off) airplane under § 23.77(a) at sea level on a standard day. For commuter category airplanes, climb performance losses should be measured and the maximum weight adjusted, if required.
(2) Handling Qualities. Handling qualities evaluation should include actual flight investigation of at least the following with the artificial ice shapes:
(i) Stall characteristics and speeds;
(ii) Trim;
(iii) Lateral directional stability/control;
(iv) Longitudinal stability/control;
(v) VMC;
(vi) Landing approach speeds, maneuvering and landing characteristics; or
(vii) Appropriate high speed characteristics up to VMO/MMO/VNE, or 250 KCAS, whichever is less.
(3) Ice-Contaminated Tailplane Stall (ICTS). ICTS occurs due to airflow separation on the lower surface of the tailplane that is caused by the angle-of-attack of the horizontal tailplane being increased above the reduced stall angle-of-attack that can result when even small quantities of ice have formed on the tailplane leading edge. The increase in tailplane angle-of-attack can result from airplane configuration (e.g., increased flap extension increasing the downwash angle or trim required for the center-of-gravity position) and/or flight conditions (e.g., high approach speed resulting in an increased flap downwash angle and reduced angle-of-attack, gusts, maneuvering or engine power changes). ICTS is characterized by a reduction or loss of pitch control or stability while operating in, or recently departing from, icing conditions. For airplanes with longitudinal control systems that are not powered, the pressure differential between the upper and lower surfaces of the stalled tailplane may result in a high elevator hinge moment, forcing the elevator trailing edge down. This elevator hinge moment reversal can be of sufficient magnitude to draw the control column forward with a level of force that is beyond the combined efforts of the pilot and copilot to overcome. On some airplanes, ICTS has been caused by a lateral flow component coming from the vertical stabilizer, as may occur in sideslip conditions or due to a gust with a lateral component. An evaluation should be made to determine if this unsafe flight condition is likely to occur. Susceptible airplanes are those having a near zero or negative stall margin with contamination. A flight test procedure for determining susceptibility to ICTS will be included in a revision to AC 23-8A. The Small Airplane Directorate, ACE-100, issued a memorandum dated July 12, 1994, subject, “Recommended Method of Identification, Susceptibility to Ice Contaminated Tailplane Stall,” that provides interim guidance and procedures for determining susceptibility to ICTS.
e. Ice Shedding. Ice shed from forward airplane structure could result in damage or erode engine or powerplant components, as well as lifting, stabilizing, and flight control surface leading
21 edges. Fan and compressor blades, impeller vanes, inlet screens and ducts, as well as propellers, are examples of powerplant components subject to damage from shedding ice. For pusher propellers that are very close to the fuselage and well back from the airplane's nose, ice shed from the forward fuselage and from the wings may cause significant propeller damage. Control surfaces such as elevators, ailerons, flaps, and spoilers are also subject to damage, especially those that are thin metallic, non-metallic, or composite constructed surfaces. Trajectory and impingement analysis may not adequately predict such damage. Unpredicted ice shedding paths from forward areas such as radomes and forward wings (canards) have been found to negate the results of this analysis. For this reason, flight tests should be conducted to supplement analysis or a damage analysis should consider the worst case ice shed event. Video or motion pictures are excellent for documenting ice shedding trajectories and impingements, while still photography may be used to document the extent of damage. Any damage should be evaluated for acceptability.
f. Pneumatic Deicer Boots. Many AFM's specify a minimum ice accumulation thickness prior to activation of the deicer boot system. This practice has been in existence due to the belief that a bridge of ice could form if the boots are operated prematurely. Although the ice may not shed completely with one cycle of the boots, this residual ice will be removed during subsequent boot cycles. The recommended AFM procedure for boot operation should be to operate the boots in an appropriate continuous mode at the first sign of ice and not to wait for a specific amount of ice to accumulate.
For applicants that choose to recommend a measurable ice accumulation prior to activation of the boots, flight tests in simulated or natural icing conditions should be accomplished to verify that the crew can detect and recognize the specified ice accumulation thickness. The following test criteria have been accepted for previous flight test programs:
(1) The pilot or a crewmember should be provided a means to detect from his crew position, under both day and night operation, the accumulation level the applicant has specified for activation of the boot system for proper ice removal.
(2) The applicant should show that an ice accumulation margin exists that allows for errors in crew recognition of the ice accumulation level.
NOTE: Usually, selection of the deicing boots to operate causes one cycle of inflation and deflation of all boots, but not necessarily at the same time. Some systems are designed such that all the boots do not complete the cycle if the deicing boots are selected off during the middle of one cycle. For these systems, there should be an AFM warning to the flight crew to select the ice protection on for at least one complete cycle of the deicing boots. This note is equally applicable to any deicing system.
g. Emergency and Abnormal Operating Conditions. Flight investigations should be conducted to verify that, after pilot recognition of emergency and abnormal operating conditions,
22 the airplane handling qualities have not deteriorated to the extent that the AFM procedures for the condition are ineffective. These demonstrations should be conducted with anticipated residual ice accumulation on normally protected surfaces.
12. PLACARDING AND AFM. This AC provides guidance on airplanes for which the certification basis requires an AFM.
a. Placarding. Any placarding necessary for the safe operation of the airplane in an icing environment must be provided in accordance with § 23.1541. Examples of such placards are:
(1) Kinds of operation approved (e.g., "Flight in Icing Conditions Approved if Ice Protection Equipment is Installed and Operational”).
(2) Equipment limits (e.g., "Operation of Windshield Anti-Ice May Cause Compass Deviation in Excess of 10°").
(3) Speed restrictions (e.g., "Maximum Speed for Boot Operation—175 KIAS").
(4) Fluid fillerinlets for fluid freezing point depressants should bear a placard showing approved fluid type and quantity.
b. AFM. The AFM should provide the pilot with the information needed to operate the ice protection system. Information should include:
(1) Operating Limitations Section. Suggested areas to be addressed are as follows:
(i) Limitations on operating time for ice protection equipment if these limitations are based on fluid anti-ice/deice systems capacities and flow rates.
(ii) Speed limitations (if any).
(iii) Environmental limitations for equipment operations as applicable (e.g., minimum temperature for boot operation or maximum altitude for boot operation).
(iv) A list of all equipment required for flight in icing conditions. Section 23.1583(h) (CAR § 3.778) requires that this list be included in the KOEL.
(v) Minimum engine speed if the engine ice protection system does not function properly below this speed.
(vi) A list of required placards.
(vii) For commuter category airplanes, the balked landing climb weight, approach climb weight, and landing weight limitations for flight in icing should be presented. The variation in weight limitations may be presented in the Performance section of the manual and included as limitations by specific reference in the Limitations section of the AFM.
(viii) Minimum and maximum (as appropriate) airspeed that should be maintained during sustained operations in icing conditions.
(ix) For severe icing that may result from environmental conditions outside the icing envelope established as the basis of the approval defined in Part 25, Appendix C, information should be provided as follows (see Appendix 2 for an example):
(A) A means to identify an icing condition that exceeeds the limits of the ice protection system for which the airplane is certificated;
(B) Recommended procedures and configurations when exiting the exceedance icing conditions;
(C) Procedures to follow during and after flight in these conditions in the event of degraded performance or handling characteristics. Information should include recommended use of flight controls, configuration of high lift devices, drag devices, automatic flight guidance system, engine power/propeller settings (as appropriate), and ice-protection system operation.
Exceedance icing conditions may be primarily water content related for thermal ice protection systems, primarily droplet diameter related for mechanical ice protection systems or some combination thereof.
(2) Operating Procedures Section.
(i) Section 23.1585(a) requires the pilot be provided with the necessary procedures for safe operation. This should include any preflight action necessary to minimize the potential of en route emergencies associated with the ice protection system. The system components should be described with sufficient clarity and depth that the pilot can understand their function. Unless flight crew actions are accepted as normal airmanship, the appropriate procedures should be included in the FAA-approved AFM, AFM revision, or AFM supplement. These procedures should include proper pilot response to cockpit warnings, a means to diagnose system failures, and the use of the system(s) in a safe manner.
(ii) Procedures should be provided to optimize operation of the airplane during penetration of icing conditions, including all flight regimes. The AFM should include procedures that advise upon which conditions the ice protection equipment should be activated.
(iii) Emergency or abnormal procedures, including procedures to be followed when ice protection systems fail and/or warning or monitor alerts occur, should be provided.
(iv) For fluid anti-ice/deice systems, information and method(s) for determining the remaining flight operation time should be provided.
(v) For airplanes that cannot supply adequate power for all systems at low engine speeds, load shedding instructions should be provided to the pilot for approach and landing in icing conditions.
(3) Performance Information Section. A brief statement that supercooled cloud test environment and freezing rain, freezing drizzle, or mixed conditions (as appropriate) have not been tested. These severe icing environmental conditions outside the icing envelope of Part 25, Appendix C, may exceed the capabilities of the ice protection system, and it may result in a serious degradation of performance or handling characteristics.
(i) Normal, Utility, and Acrobatic Category Airplanes. For these airplanes, general performance information should be provided to give the pilot knowledge of allowances necessary while operating in ice or with residual ice on the airframe. The following items are only examples that provide some guidelines and are not requirements. These guidelines may be revised for specific airplanes as appropriate:
(A) An accumulation of inch of ice on the leading edges can cause a loss in rate of climb up to FPM, a cruise speed reduction of up to KIAS, as well as a significant buffet and stall speed increase (up to knots). Even after cycling the deicing boots, the ice accumulation remaining on the boots and unprotected areas of the airplane can cause large performance losses. With residual ice from the initial inch accumulation, losses up to FPM in climb, KIAS in cruise, and a stall speed increase of knots can result. With inch of residual accumulation, these losses can double.
(B) Airspeed—MAINTAIN BETWEEN KIAS AND KIAS with ____ inch or more of ice accumulation for appropriate configuration..
(C) Prior to a landing approach, cycle the wing and stabilizer deice boots to shed any accumulated ice. Maintain extra airspeed on approach to compensate for the increased stall speed associated with ice on unprotected areas. Use caution when cycling the boots during an approach since boot inflation with no ice accumulation may cause mild pitching and increase stall speeds by knots; it may decrease stall warning margin by the same amount; and it may cause or increase rolling tendency during stall.
(D) Holding in icing conditions for longer than 45 minutes may reduce margins and could result in inadequate handling and control characteristics.