service tours, does not jeopardize the worn brake RTO capabilities of the original or the replacement wheel and brake assemblies. Since dynamometer testing is generally impractical, the applicant should forward to the FAA an in-service plan to survey wear and wear patterns from a sampling of worn in-service brakes containing steel rollers from the original manufacturer only, from the applicant only, and from an intermix brake(s). Since the original manufacturer's brake often contains second, and possibly third tour reground steel rotors, at least two tours of inservice evaluation with replacement steel rotors may be required to assess equivalence. This data will provide guidance for approved worn brake RTO wear limits for brakes containing replacement rotors.
(E) Torque/pressure ratio-profiles. A torque/pressure ratio test plan and tests are required to demonstrate equivalent gain performances over a range of test speeds and test pressures. The test article conditions, break-in conditions and procedures, test speed range, and test pressure matrix, used to evaluate both the original and applicant wheel and brake assemblies, must be the same with tests conducted in the same order. The results of these tests will provide guidance for braking system control compatibility assessments.
(F) As a minimum, the five functional landings described in paragraph 55(c)(5)( i), above, are also a required part of this approval procedure.
(G) Continued Airworthiness. Past history with friction material cou ples has indicated the necessity of ongoing monitoring (by dynamometer test) of RTO capability to assure that the AFM limitations are not exceeded over the life of airplane programs. For larger transport category commercial airplanes, it has been shown that these monitoring plans have complemented the detection and correction of unacceptable deviations. The applicant must provide the FAA with a quality plan to demonstrate that the RTO capability of the friction couple is maintained with replacement steel rotors over time.
(6) Auto-braking. The following are required for auto-braking installations based on function, nonhazard, and non-interference on airplanes for which performance without auto-braking has been determined:
(i) The system design mus t be evaluated for integrity and non-hazard, including the probability and consequence of insidious failure of critical components. No single failure may compromise non-automatic braking of the airplane.
(ii) Positive indication of whether the system is operative or inoperative must be provided.
(iii) For each auto-brake setting for which approval is desired, the ground roll distance from touchdown to stop must be determined for the landing weights and altitudes within the envelope for which approval is desired. In determining ground roll distance, the performance must be established without reverse thrust, and any adverse effect upon performance associated with the use of reverse thrust must be established and accounted for.
Repeatability of initial application should be shown by comparing the onset of braking for each of the range of settings. Landing ground roll distance data determined as prescribed herein must be presented in the performance information section of the FAA-approved AFM as guidance material.
If the auto-braking system is to be approved for wet runways, auto-brake compatibility on a wet runway should be demonstrated. These tests may be limited to the highest auto-brake setting, where antiskid activity is expected to occur throughout the stop, and a single lower setting, where antiskid activity is expected to occur for only a portion of the stop. AFM stopping distances for other settings can be computed based on predicted wet-runway friction coefficients and do not require demonstrations on wet runways of all auto-brake settings. Landing ground roll distance data determined on a wet runway should also be presented in the AFM for all operating modes of the system. This information is considered necessary so that the pilot can readily compare the automatic brake stopping distance and the actual runway length available, so as to assess the effect of the use of the automatic braking system on the runway margin provided by the factored field length.
(iv) Automatic braking systems that are to be approved for use during rejected takeoff conditions should provide only a single brake setting that provides maximum braking. In the event that automatic brakes result in a longer rejected takeoff distance than manual brakes, the FAA-approved AFM must present the longer rejected takeoff distance.
(v) Procedures describing how the automatic braking system was used during the FAA evaluation and in determining the landing ground roll distance of paragraph 55c(6)(iii) must be presented in the AFM.
(vi) Compliance with operational requirements regarding landing runway length will continue to be predicated on landing distance data established using the requirements of § 25.125 for non-automatic braking.
(7) Wheel Fuse Plug Design.
(i) Wheel fuse plug integrity should be substantiated during braking tests where the energy level simulates the maximum landing energy. It should be demonstrated that the wheel fuse plugs will remain intact, and that unwanted releases do not occur. One acceptable method to determine this is as follows:
(A) Set engine idle thrust at the maximum value specified (if applicable).
(B) Taxi at least three miles (normal braking, at least three intermediate stops, and all engines operating).
(C) Conduct accelerate-stop test at maximum landing energy, maintaining the deceleration rate consistent with the values used to determine performance distance.
(D) Taxi at least three miles (normal braking, at least three intermediate stops, and all engines operating).
(E) Park in an area so as to minimize wind effects until it is assured that fuse plug temperatures have peaked and that no plugs have released.
(ii) In lieu of simulating the maximum kinetic energy landing during an accelerate-stop te st, an actual landing and quick turn-around may be performed; however, caution should be exercised in order to prevent jeopardizing the safety of the flightcrew and airplane if the wheel plugs release right after liftoff, requiring a landing to be made with some flat tires. The following elements should be included in the tests:
(A) Set engine idle thrust at maximum value specified (if applicable).
(B) Conduct a landing stop at maximum landing energy, maintaining the deceleration rate consistent with the values used to determine performance distance.
(C) Taxi to the ramp (three miles minimum with normal braking, at least three intermediate stops, and all engines operating).
(D) Stop at the ramp. Proceed immediately to taxi for takeoff.
(E) Taxi for takeoff (three miles minimum with normal braking, at least three intermediate stops, and all engines operating).
(F) Park in an area so as to minimize wind effects until it is assured that fuse plug temperatures have peaked and that no plugs have released.
(iii) Fuse plug protection of wheels and tires should be demonstrated to show that the fuse plugs will release when excessive energies are absorbed. Normally, this will occur during RTO performance tests.
56. SKIS - § 25.737 [RESERVED ]
Section 5. FLOATS AND HULLS
57. - 59. [RESERVED]
Section 6. PERSONNEL AND CARGO ACCOMMODATIONS
60. - 61. [RESERVED]
62. PILOT COMPARTMENT VIEW - § 25.773 .
a. Explanation. (Reserved.)
b. Procedures . For detailed guidance on complying with pilot compartment view requirements, refer to Advisory Circular 25.773-1, "Pilot Compartment View for Transport Category Airplanes," dated January 8, 1993.
63. - 72. [RESERVED]
Section 7. EMERGENCY PROVISIONS
73. [RESERVED]
74. EMERGENCY EVACUATION - § 25.810(c) .
a. Explanation.
(1) Installation of slip-resistant escape route. (See § 25.810(c), formerly § 25.803(e) See Advisory Circular 25-17, “Transport Airplane Cabin Interiors Crashworthiness Handbook,” § 25.803(e), for guidance regarding slip resistant material.
(2) The effect of the slip-resistant surfaces on airplane performance, flight characteristics, and buffet should be evaluated and should, if necessary, account for significant drag increments.
b. Procedures . None.
75. - 83. [RESERVED]
Section 8. VENTILATION AND HEATING
84. VENTILATION - § 25.831 .
a. Explanation.
(1) This requirement deals with minimum ventilation requirements for each occupant of the airplane, control of the ventilating air, accumulation and evacuation of smoke and harmful or hazardous concentrations of gases or vapors, and failure conditions of the ventilation system. Specific quantities of fresh air along with carbon monoxide and carbon dioxide concentration limits are specified in the rule. Reference should be made to the paragraphs in this AC dealing with Cargo and Baggage Compartments, § 25.855; Exhaust Systems, § 25.1121; and Fire Extinguishing Agents, § 25.1197. AC 25-20, “Pressurization, Ventilation, and Oxygen Systems Assessment for Subsonic Flight Including High Altitude Operations,” also provides guidance for ventilation requirements.
(2) The objective of the inflight smoke evacuation test is to confirm that the flightcrew emergency procedures and the ventilation system are capable of handling heavy smoke, and to show that when using the emergency procedures, the smoke will dissipate at a reasonable rate. This is a quantitative and qualitative evaluation.
b. Procedures .
(1) Flight testing should be conducted to ensu re the amount of ventilation air provided meets the requirements specified and the flightcrew is able to accomplish their duties without undue fatigue and discomfort.
Ventilation system controls in the flight deck should be demonstrated to perform their intended function.
(2) The passenger and crew compartment should be monitored for the presence of carbon monoxide.
Various flight and equipment configurations should be tested. A carbon monoxide test kit is normally used for this evaluation.
(3) Inflight smoke evacuation testing should be conducted in accordance with Advisory Circular 25-9A, "Smoke Detection, Penetration, and Evacuation Tests and Related Flight Manual Emergency Procedures," dated January 6, 1994.
85. - 86. [RESERVED]
Section 9. PRESSURIZATION
87. PRESSURIZED CABINS - § 25.841.
a. Explanation.
(1) Section 25.841(a) specifies cabin pressure altitude limits, as a function of the external pressure altitude, for cabins and compartments intended to be occupied. AC 25-20, “Pressurization, Ventilation, and Oxygen Systems Assessment for Subsonic Flight Including High Altitude Operation,” dated 9/10/96, provides additional guidance for pressurized cabins.
These cabin pressure altitude limits, to be demonstrated by flight testing, are:
(i) Not more than 8,000 ft., at the maximum operating altitude of the airplane, for normal operation of the pressurization system.
(ii) For airplanes to be operated above 25,000 ft., the airplane must be able to maintain a cabin pressure altitude of not more than 15,000 ft. in the event of any reasonably probable failure or malfunction in the pressurization system.
(2) Though not addressed by § 25.841, airplanes may incorporate a "high altitude mode" to permit takeoff and landing at airports above 8,000 ft. For takeoff and landing altitudes above 8,000 ft., the cabin pressure limits to be demonstrated by flight testing are:
(i) Prior to beginning a descent into a high altitude airport, not more than 8,000 ft.
(ii) During a descent into or climb out of a high altitude airport, not more than 15,000 ft.
(iii) After a takeoff from a high altitude airport and after the cabin pressure altitude decreases to 8,000 ft., not more than 8,000 ft.
(3) Section 25.841(b)(6) requires an aural or visual warning to the flightcrew when the cabin pressure altitude exceeds 10,000 ft. For airplanes incorporating a high altitude mode that resets the cabin pressure altitude warning threshold, the reset warning activation level should not exceed 15,000 ft.
b. Procedures. It is recommended that the test airplane have the maximum allowable leakage rate permitted by the type design specifications. If an airplane does not meet this criteria, it will be necessary to substantiate compliance by additional testing or analysis for the maximum leakage rate allowed by the type design.
(1) Normal Operating Conditions - 8,000 Ft. Cabin Pressure Altitude.
(i) With the pressurization system operating in its normal mode, the airplane should be stabilized in the cruise configuration at the maximum operating altitude it is to be certificated for.
(ii) The condition should be held long enough to record any cyclic fluctuations in cabin pressure due to relief valve operation.
(iii) The cabin pressure altitude should not exceed 8,000 ft.
(2) Failure Conditions - 15,000 Ft. Cabin Pressure Altitude.
(i) The critical reasonably probable system failure should be identified. The cabin pressure altitude warning system should be set to the high altitude side of its tolerance band or additional testing or analysis may be necessary for compliance.. If more than one system failure mode is determined to meet the "reasonably probable" criteria, the flight test should be conducted for each failure mode identified.
(ii) The airplane should be stabilized in the cruise configuration at the maximum operating altitude it is to be certificated to, with the pressurization system operating in its normal mode.
(iii) After initiating the critical failure to allow the cabin pressure altitude to increase, the flight test crew should immediately don their oxygen masks, but take no further corrective action until 17 seconds after the 10,000 ft. cabin pressure altitude warning activates.
Emergency descent procedures should then be initiated and the descent continued to an altitude below 15,000 ft.
(iv) The cabin pressure altitude should not exceed 15,000 ft. at any time during the test.
(3) High Altitude Takeoff Conditions (Greater than 8,000 Ft.).
(i) The pressurization system should be placed in its high altitude mode. It may be necessary to configure the oxygen system to prevent deployment of the oxygen masks at 10,000 ft., if the system is so designed. Airplane Flight Manual (AFM) procedures may need to be developed. The same applies to high altitude landings above 10,000 ft.
(ii) The cabin pressure altitude should not exceed 15,000 ft. during an actual climb-out from a high altitude airport to the maximum operating altitude the airplane is to be certificated for, or during an inflight simulation of such a climb-out. The simulation should commence the climb, from a starting altitude of 8,000 ft. or more, with the airplane unpressurized.
(iii) The cabin pressure altitude should eventually decrease to 8,000 ft. and then not exceed 8,000 ft. for the duration of the test.
(4) High Altitude Landing Conditions (Greater than 8,000 Ft).
(i) The airplane should be stabilized in the cruise configuration prior to beginning a descent.
(ii) The pressurization system should be placed in its high altitude mode.
(iii) The cabin pressure altitude should not exceed 15,000 ft. during the descent to an actual, or simulated, landing at a high altitude airport.
88. TESTS FOR PRESSURIZED CABINS - § 25.843.
a. Explanation.
(1) Section 25.843(b)(3) requires flight testing to evaluate the performance of the pressurization system and all related sub-systems at maximum altitude and under the dynamic conditions of climbing and descending flight. This testing substantiates the ability of the pressurization system to function correctly in stable and dynamic external pressure conditions.
(2) Section 25.843(b)(4) requires an investigation of the functionality of all doors and emergency exits after the flight test required by § 25.843(b)(3). The concern is the potential for jamming caused by the variable relative positions of doors and fuselage structure during the pressurization/depressurization cycle.
b. Procedures. The following tests may be initiated from an airport at any altitude within the airplane's proposed takeoff limitations. The pressurization system should be operated in its normal mode. The Master Minimum Equipment List (MMEL) dispatch may be taken into consideration and additional testing required to verify MMEL configuration.
(1) Steady Climb/Descent. The steady climb/descent pressurization system tests should be performed under conditions (i.e., weight, altitude, temperature, and configuration) that will result in rates of climb/descent corresponding to the maximum attainable within the operating limitations of the airplane.
(i) After takeoff, maintain a stable, continuous climb to the maximum operating altitude the airplane will be certificated to.
(ii) Maintain that altitude until the cabin pressure altitude has stabilized.
(iii) Initiate a steady, maximum rate of descent within the operating limitations of the airplane down to the airport.
(2) Stepped Climb/Descent. The stepped climb/descent pressurization system tests should be performed under conditions (i.e., weight, altitude, temperature, and configuration) that will result in rates of climb/descent corresponding to the maximum attainable within the operating limitations of the airplane.
(i) After takeoff, initiate a stepped climb to the maximum operating altitude the airplane will be certificated to. Step increments should be 5,000 to 7,500 ft.
(ii) Maintain each level-off altitude long enough for the cabin pressure altitude to stabilize.
(iii) Initiate a stepped descent from the maximum altitude allowing the cabin pressure altitude to stabilize at each level-off altitude. Step increments should be 7,500 to 10,000 ft.
(3) Positive Pressure Relief. If two valves are provided, one should be deactivated for this test.
(i) After takeoff, climb to the operating altitude that provides maximum cabin differential pressure.
(ii) Manually close the outflow valve, allowing the cabin differential pressure to increase.
(iii) Verify the cabin pressure differential pressure warning functions properly.
(iv) Verify that the relief valve functions and the maximum cabin differential pressure is not exceeded.
(4) Negative Pressure Relief/Emergency Descent. If two valves are provided, deactivate one for this test.
(i) At cruise altitude, perform an emergency descent with the airplane in the critical condition for negative pressure on the fuselage.
(ii) Verify that the maximum negative differential pressure for the fuselage is not exceeded.
(5) Manual Cabin Pressure Control. If manual means for pressure control are provided, these means should be evaluated under normal and emergency operations of the airplane and flight envelope.
(6) Testing of Doors and Exits.
(i) Prior to flight, all doors and exits should be checked for proper operation.
(ii) After returning from a flight where the airplane is subjected to the maximum certificated altitude and cabin pressure differential pressure, and immediately upon landing, all passenger doors and emergency exits should be opened. There should be no change in the operating characteristics of any door or emergency exit relative to its pre-flight operation.
Section 10. FIRE PROTECTION (RESERVED)
Section 11. MISCELLANEOUS (RESERVED)