APPENDIX 1 to Special Condition P-27
TCDS A.064 ANNEX - Airbus A318, A319, A320, A321 - Special Conditions APPENDIX 1 to Special Condition P-27 1. Monte Carlo Analysis (a) A Monte Carlo analysis must be conducted for the fuel tank under evaluation to determine fleet average and warm day flammability exposure for the aeroplane under evaluation. The analysis must include the parameters defined in Appendices 1 and 2 of these special conditions. The aeroplane specific parameters and assumptions used in the Monte Carlo analysis must include: (1) FRS Performance – as defined by system performance.
(2) Cruise Altitude – as defined by aeroplane performance.
(3) Cruise Ambient Temperature – as defined in Appendix 2 of these special conditions.
(4) Overnight Temperature Drop – as defined in Appendix 2 of these special conditions.
(5) Fuel Flash Point and Upper and Lower Flammability Limits – as defined in Appendix 2 of these special conditions.
(6) Fuel Burn – as defined by aeroplane performance.
(7) Fuel Quantity – as defined by aeroplane performance.
(8) Fuel Transfer – as defined by aeroplane performance.
(9) Fuelling Duration – as defined by aeroplane performance.
(10) Ground Temperature – as defined in Appendix 2 of these special conditions.
(11) Mach Number – as defined by aeroplane performance.
(12) Mission Distribution – the applicant must use the mission distribution defined in Appendix 2 of these special conditions or may request EASA approval of alternative data.
(13) Oxygen Evolution – as defined by aeroplane performance or as defined in Appendix 2 of these special conditions.
(14) Maximum Aeroplane Range – as defined by aeroplane performance.
(15) Tank Thermal Characteristics – as defined by aeroplane performance.
(16) Descent Profile Distribution – the applicant must use either a fixed 2500 feet per minute descent rate or may request EASA approval of alternative data.
(b) The assumptions for the analysis must include: (1) FRS performance throughout the flammability exposure evaluation time; (2) Vent losses due to crosswind effects and aeroplane performance; Disclaimer – This document is not exhaustive and it will be updated gradually. Page 22 TCDS A.064 ANNEX - Airbus A318, A319, A320, A321 - Special Conditions (3) Periods when the system is operating properly but fails to inert the tank; Note: Localized concentrations above the inert level as a result of fresh air that is drawn into the fuel tank through vents during descent would not be considered as flammable.
(4) Expected system reliability; (5) The MMEL/MEL dispatch inoperative period assumed in the reliability analysis, (60 flight hours must be used for a 10-day MMEL dispatch limit unless an alternative period has been approved by the PCA), including action to be taken when dispatching with the FRS inoperative (Note: The actual MMEL dispatch inoperative period data must be included in the engineering reporting requirement of paragraph 1.5 of these special conditions); (6) Possible periods of system inoperability due to latent or known failures, including aeroplane system shut-downs and failures that could cause the FRS to shut down or become inoperative; and (7) Effects of failures of the FRS that could increase the flammability of the fuel tank.
(8) Ancillary tanks where significant vapour transfer takes place, such as surge tanks, must be considered flammable if any primary fuel tank connected to the tank contains flammable vapors. In addition, these ancillary tanks are considered inert if all primary tanks are inert.
(c) The Monte Carlo analysis, including a description of any variation assumed in the parameters (as identified under paragraph (a) of this appendix) that affect fleet average or warm day flammability exposure, and substantiating data must be submitted to EASA for approval.
Disclaimer – This document is not exhaustive and it will be updated gradually. Page 23
APPENDIX 2 to Special Condition P-27
TCDS A.064 ANNEX - Airbus A318, A319, A320, A321 - Special Conditions APPENDIX 2 to Special Condition P-27 1. Monte Carlo Model (a) The FAA has developed a Monte Carlo model that can be used to develop a specific analysis model for the Boeing 747 to calculate fleet average and warm day flammability exposure for a fuel tank. The program requires the user to enter the aeroplane performance data specific to the aeroplane model being evaluated, such as maximum range, cruise mach number, typical step climb altitudes, tank thermal characteristics specified as exponential heating/cooling time constants, and equilibrium temperatures for various fuel tank conditions. The general methodology for conducting a Monte Carlo model is described in AC 25.981-2.
(b) The FAA model, or one with modifications approved by the FAA, must be used as the means of compliance with these special conditions. Contact EASA Certification Directorate to obtain the correct version of the model to use. The following procedures, input variables, and data tables must be used in the analysis if the applicant develops a unique model to determine fleet average flammability exposure for a specific aeroplane type.
2. Monte Carlo Variables and Data Tables (a) Fleet average flammability exposure is the percent of the mission time the fuel tank ullage is flammable for a fleet of an aeroplane type operating over the range of actual or expected missions and in a world-wide range of environmental conditions and fuel properties. Variables used to calculate fleet average flammability exposure must include atmosphere, mission length (as defined in paragraph 1.2 Definitions, as FLEET), fuel flash point, thermal characteristics of the fuel tank, overnight temperature drop, and oxygen evolution from the fuel into the ullage. Transport effects are not to be allowed as parameters in the analysis.
(b) For the purposes of these special conditions, a fuel tank is considered flammable when the ullage is not inert and the fuel vapour concentration is within the flammable range for the fuel type being used. The fuel vapour concentration of the ullage in a fuel tank must be determined based on the bulk average fuel temperature within the tank. This vapour concentration must be assumed to exist throughout all bays of the tank. For those aeroplanes with fuel tanks having different flammability exposure within different compartments of the tank, where mixing of the vapour or NEA does not occur, the Monte Carlo analysis must be conducted for the compartment of the tank with the highest flammability. The compartment with the highest flammability exposure for each flight phase must be used in the analysis to establish the fleet average flammability exposure. For example, the centre wing fuel tank in some designs extends into the wing and has compartments of the tank that are cooled by outside air, and other compartments of the tank that are insulated from outside air. Therefore, the fuel temperature and flammability is significantly different between these compartments of the fuel tank.
(c) Atmosphere (1) In order to predict flammability exposure during a given flight, the variation of ground ambient temperatures, cruise ambient temperatures, and a method to compute the transition from ground to cruise and back again must be used. The variation of the ground and cruise ambient temperatures and the flash point of the fuel are defined by a Gaussian curve, given by the 50 percent value and a 1 standard deviation value.
Disclaimer – This document is not exhaustive and it will be updated gradually. Page 24 TCDS A.064 ANNEX - Airbus A318, A319, A320, A321 - Special Conditions (2) The ground and cruise temperatures are linked by a set of assumptions on the atmosphere. The temperature varies with altitude following the International Standard Atmosphere (ISA) rate of change from the ground temperature until the cruise temperature for the flight is reached. Above this altitude, the ambient temperature is fixed at the cruise ambient temperature. This results in a variation in the upper atmosphere (tropopause) temperature. For cold days, an inversion is applied up to 10,000 feet, and then the ISA rate of change is used. The warm day subset (see paragraph 1.3 (b) (1) of these special conditions) for ground and climb uses a range of temperatures above 80°F (26.7°C) and is included in the Monte Carlo model.
(3) The analysis must include a minimum number of flights, and for each flight a separate random number must be generated for each of the three parameters (i.e. ground ambient temperature, cruise ambient temperature, and fuel flash point) using the Gaussian distribution defined in Table 1. The applicant can verify the output values from the Gaussian distribution using Table 2.
(d) Fuel Properties.
(1) Flash point variation. The variation of the flash point of the fuel is defined by a Gaussian curve, given by the 50 percent value and a 1-standard deviation value.
(2) Upper and Lower Flammability Limits. The flammability envelope of the fuel that must be used for the flammability exposure analysis is a function of the flash point of the fuel selected by the Monte Carlo for a given flight. The flammability envelope for the fuel is defined by the upper flammability limit (UFL) and lower flammability limit (LFL) as follows: (i) LFL at sea level = flash point temperature of the fuel at sea level minus10 degrees F. LFL decreases from sea level value with increasing altitude at a rate of 1 degree F per 808 ft.
(ii) UFL at sea level = flash point temperature of the fuel at sea level plus 63.5 degrees F. UFL decreases from the sea level value with increasing altitude at a rate of 1 degree F per 512 ft.
Note: Table 1 includes the Gaussian distribution for fuel flash point. Table 2 also includes information to verify output values for fuel properties. Table 2 is based on typical use of Jet A type fuel, with limited TS-1 type fuel use.
Table 1. Gaussian Distribution for Ground Ambient, Cruise Ambient, and Flash Point Temperature in Deg F Flash Point Parameter Ground Amb. Cruise Amb. (FP) Mean Temp 59.95 -70 120 neg 1 std dev 20.14 8 8 pos 1 std dev 17.28 8 8 Disclaimer – This document is not exhaustive and it will be updated gradually. Page 25 TCDS A.064 ANNEX - Airbus A318, A319, A320, A321 - Special Conditions Table 2. Verification of Table 1 % Probability of Temps & Flash Point Being Below Flash Ground the Listed Values Ground Amb. Cruise Amb. Point Amb. Cruise Amb. Flash Point (FP) Deg F Deg F Deg F Deg C Deg C Deg C 1 13.1 -88.6 101.4 -10.5 -67.0 38.5 5 26.8 -83.2 106.8 -2.9 -64.0 41.6 10 34.1 -80.3 109.7 1.2 -62.4 43.2 15 39.1 -78.3 111.7 3.9 -61.3 44.3 20 43.0 -76.7 113.3 6.1 -60.4 45.1 25 46.4 -75.4 114.6 8.0 -59.7 45.9 30 49.4 -74.2 115.8 9.7 -59.0 46.6 35 52.2 -73.1 116.9 11.2 -58.4 47.2 40 54.8 -72.0 118.0 12.7 -57.8 47.8 45 57.4 -71.0 119.0 14.1 -57.2 48.3 50 59.9 -70.0 120.0 15.5 -56.7 48.9 55 62.1 -69.0 121.0 16.7 -56.1 49.4 60 64.3 -68.0 122.0 18.0 -55.5 50.0 65 66.6 -66.9 123.1 19.2 -55.0 50.6 70 69.0 -65.8 124.2 20.6 -54.3 51.2 75 71.6 -64.6 125.4 22.0 -53.7 51.9 80 74.5 -63.3 126.7 23.6 -52.9 52.6 85 77.9 -61.7 128.3 25.5 -52.1 53.5 90 82.1 -59.7 130.3 27.8 -51.0 54.6 95 88.4 -56.8 133.2 31.3 -49.4 56.2 99 100.1 -51.4 138.6 37.9 -46.3 59.2 (e) Flight Mission Distribution (1) The mission length for each flight is determined from an equation that takes the maximum mission length for the aeroplane and randomly selects multiple flight lengths based on typical airline use.
(2) The mission length selected for a given flight is used by the Monte Carlo model to select a 30-, 60-, or 90- minute time on the ground prior to takeoff, and the type of flight profile to be followed. Table 3 must be used to define the mission distribution. A linear interpolation between the values in the table must be assumed.
Disclaimer – This document is not exhaustive and it will be updated gradually. Page 26 TCDS A.064 ANNEX - Airbus A318, A319, A320, A321 - Special Conditions Table 3. Mission Range Distribution Aeroplane Maximum Range - Nautical Miles (NM) 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 Flight Length (NM) Distribution of missions Lengths(%) From To 0 200 11.7 7.5 6.2 5.5 4.7 4.0 3.4 3.0 2.6 2.3 200 400 27.3 19.9 17.0 15.2 13.2 11.4 9.7 8.5 7.5 6.7 400 600 46.3 40.0 35.7 32.6 28.5 24.9 21.2 18.7 16.4 14.8 600 800 10.3 11.6 11.0 10.2 9.1 8.0 6.9 6.1 5.4 4.8 800 1000 4.4 8.5 8.6 8.2 7.4 6.6 5.7 5.0 4.5 4.0 1000 1200 0.0 4.8 5.3 5.3 4.8 4.3 3.8 3.3 3.0 2.7 1200 1400 0.0 3.6 4.4 4.5 4.2 3.8 3.3 3.0 2.7 2.4 1400 1600 0.0 2.2 3.3 3.5 3.3 3.1 2.7 2.4 2.2 2.0 1600 1800 0.0 1.2 2.3 2.6 2.5 2.4 2.1 1.9 1.7 1.6 1800 2000 0.0 0.7 2.2 2.6 2.6 2.5 2.2 2.0 1.8 1.7 2000 2200 0.0 0.0 1.6 2.1 2.2 2.1 1.9 1.7 1.6 1.4 2200 2400 0.0 0.0 1.1 1.6 1.7 1.7 1.6 1.4 1.3 1.2 2400 2600 0.0 0.0 0.7 1.2 1.4 1.4 1.3 1.2 1.1 1.0 2600 2800 0.0 0.0 0.4 0.9 1.0 1.1 1.0 0.9 0.9 0.8 2800 3000 0.0 0.0 0.2 0.6 0.7 0.8 0.7 0.7 0.6 0.6 3000 3200 0.0 0.0 0.0 0.6 0.8 0.8 0.8 0.8 0.7 0.7 3200 3400 0.0 0.0 0.0 0.7 1.1 1.2 1.2 1.1 1.1 1.0 3400 3600 0.0 0.0 0.0 0.7 1.3 1.6 1.6 1.5 1.5 1.4 3600 3800 0.0 0.0 0.0 0.9 2.2 2.7 2.8 2.7 2.6 2.5 3800 4000 0.0 0.0 0.0 0.5 2.0 2.6 2.8 2.8 2.7 2.6 4000 4200 0.0 0.0 0.0 0.0 2.1 3.0 3.2 3.3 3.2 3.1 4200 4400 0.0 0.0 0.0 0.0 1.4 2.2 2.5 2.6 2.6 2.5 4400 4600 0.0 0.0 0.0 0.0 1.0 2.0 2.3 2.5 2.5 2.4 4600 4800 0.0 0.0 0.0 0.0 0.6 1.5 1.8 2.0 2.0 2.0 4800 5000 0.0 0.0 0.0 0.0 0.2 1.0 1.4 1.5 1.6 1.5 5000 5200 0.0 0.0 0.0 0.0 0.0 0.8 1.1 1.3 1.3 1.3 5200 5400 0.0 0.0 0.0 0.0 0.0 0.8 1.2 1.5 1.6 1.6 5400 5600 0.0 0.0 0.0 0.0 0.0 0.9 1.7 2.1 2.2 2.3 5600 5800 0.0 0.0 0.0 0.0 0.0 0.6 1.6 2.2 2.4 2.5 5800 6000 0.0 0.0 0.0 0.0 0.0 0.2 1.8 2.4 2.8 2.9 6000 6200 0.0 0.0 0.0 0.0 0.0 0.0 1.7 2.6 3.1 3.3 6200 6400 0.0 0.0 0.0 0.0 0.0 0.0 1.4 2.4 2.9 3.1 6400 6600 0.0 0.0 0.0 0.0 0.0 0.0 0.9 1.8 2.2 2.5 6600 6800 0.0 0.0 0.0 0.0 0.0 0.0 0.5 1.2 1.6 1.9 6800 7000 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.8 1.1 1.3 7000 7200 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.4 0.7 0.8 7200 7400 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.3 0.5 0.7 7400 7600 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.5 0.6 7600 7800 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.5 0.7 7800 8000 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.6 0.8 8000 8200 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.5 0.8 8200 8400 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.5 1.0 8400 8600 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.6 1.3 8600 8800 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.4 1.1 8800 9000 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.8 9000 9200 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.5 9200 9400 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 9400 9600 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 9600 9800 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 9800 10000 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 Disclaimer – This document is not exhaustive and it will be updated gradually. Page 27 TCDS A.064 ANNEX - Airbus A318, A319, A320, A321 - Special Conditions (f) Fuel Tank Thermal Characteristics (1) The applicant must account for the thermal conditions of the fuel tank both on the ground and in flight. The Monte Carlo model, available on the website listed above, defines the ground condition using an equilibrium delta temperature (relative to the ambient temperature) that the tank will reach given a long enough time, with any heat inputs from aeroplane sources. Values are also input to define two exponential time constants (one for a near empty tank and one for a near full tank) for the ground condition. These time constants define the time for the fuel in the fuel tank to heat or cool in response to heat input. The fuel is assumed to heat or cool according to a normal exponential transition, governed by the temperature difference between the current temperature and the equilibrium temperature, given by ambient temperature plus delta temperature. Input values for this data can be obtained from validated thermal models of the tank based on ground and flight test data. The inputs for the in-flight condition are similar but are used for in-flight analysis.
(2) Fuel management techniques are unique to each manufacturer’s design and variations in fuel quantity within the tank for given points in the flight, including fuel transfer for any purpose, must be accounted for in the model. The model uses a “tank full” time, specified in minutes, that defines the ti me before touchdown when the fuel tank is still full. For a centre wing tank used first, this number would be the maximum flight time, and the tank would start to empty at takeoff. For a main tank used last, the tank will remain full for a shorter time b efore touch down, and would be “empty” at touch down (i.e., tank empty at 0 minutes before touch down). For a main tank with reserves, the term empty means at reserve level rather than totally empty. The thermal data for tank empty would also be for reserve level.
(3) The model also uses a “tank empty” time to define the time when the tank is emptying, and the program uses a linear interpolation between the exponential time constants for full and empty during the time the tank is emptying. For a tank that is only used for long-range flights, the tank would be full only on longer range flights and would be empty a long time before touch down. For short flights, it would be empty for the whole flight. For a main tank that carried reserve fuel, it would be full for a long time and would only be down to empty at touch down. In this case, empty would really be at reserve level, and the thermal constants at empty should be those for the reserve level.
(4) The applicant must propose means to validate thermal time constants and equilibrium temperatures to be used in the analysis. The applicant may propose using a more detailed thermal definition, such as changing time constants as a function of fuel quantity, provided the details and substantiation information are acceptable and the Monte Carlo model programme changes are validated.
(g) Overnight Temperature Drop (1) An overnight temperature drop must be considered in the Monte Carlo analysis as it may affect the oxygen concentration level in the fuel tank. The overnight temperature drop for these special conditions will be defined using: A temperature at the beginning of the overnight period based on the landing temperature that is a random value based on a Gaussian distribution; and An overnight temperature drop that is a random value based on a Gaussian distribution.
Disclaimer – This document is not exhaustive and it will be updated gradually. Page 28 TCDS A.064 ANNEX - Airbus A318, A319, A320, A321 - Special Conditions (2) For any flight that will end with an overnight ground period (one flight per day out of an average of “x” flights per day, depending on use of the particular aeroplane model being evaluated), the landing outside air temperature (OAT) is to be chosen as a random value from the following Gaussian curve: Table 4. Landing OAT Landing Parameter Temperature °F Mean Temp 58.68 neg 1 std dev 20.55 pos 1 std dev 13.21 (3) The outside ambient air temperature (OAT) drop for that night is to be chosen as a random value from the following Gaussian curve: Table 5. OAT Drop OAT Drop Parameter Temperature °F Mean Temp 12.0 1 std dev 6.0 (h) Oxygen Evolution The oxygen evolution rate must be considered in the Monte Carlo analysis if it can affect the flammability of the fuel tank or compartment. Fuel contains dissolved gases, and in the case of oxygen and nitrogen absorbed from the air, the oxygen level in the fuel can exceed 30 percent, instead of the normal 21 percent oxygen in air. Some of these gases will be released from the fuel during the reduction of ambient pressure experienced in the climb and cruise phases of flight. The applicant must consider the effects of air evolution from the fuel on the level of oxygen in the tank ullage during ground and flight operations and address these effects on the overall performance of the FRS. The applicant must provide the air evolution rate for the fuel tank under evaluation, along with substantiation data.
(i) Number of Simulated Flights Required in Analysis In order for the Monte Carlo analysis to be valid for showing compliance with the fleet average and warm day flammability exposure requirements of these special conditions, the applicant must run the analysis for an appropriate number of flights to ensure that the fleet average and warm day flammability exposure for the fuel tank under evaluation meets the flammability limits defined in Table 6.
Table 6. Flammability Limit Number of Flights Maximum Acceptable in Monte Carlo Analysis Fuel Tank Flammability (%) 1,000 2.73 5,000 2.88 10,000 2.91 100,000 2.98 1,000,000 3.00 Disclaimer – This document is not exhaustive and it will be updated gradually. Page 29 TCDS A.064 ANNEX - Airbus A318, A319, A320, A321 - Special Conditions SPECIAL CONDITION S75 : Lightning Protection Indirect Effects APPLICABILITY: A318 / A319 / A320 / A321 REQUIREMENTS: JAR 25.581, 25X899, 25.954, 25.1309 ADVISORY MATERIAL: N/A Add to JAR 25.x899 new paragraph (f): (f) 1. Each system whose failure to function properly would prevent the continued safe flight and landing or the airplane, must.be designed and installed to ensure that the aircraft operation is not affected during and after exposure to lightning.
(f) 2. Each system whose failure to function properly would reduce the capability of the airplane or the ability of the flight crew to cope with adverse operating conditions, must be designed and installed to ensure that it can perform its intended function after exposure to lightning.
MEANS OF COMPLIANCE The lightning strike models to be used tor system justification shall be as follows: SEVERE STRIKE (FIRST RETURN STROKE) Peak Amplitude 200 KA Peak Rate or Rise 200 KA/Micro-second 6 2 Action Integral 2 x 10 Amp - sec Bi-exponential waveshape.
MULTIPLE STROKE FLASH (CLOUD TO CLOUD STRIKES) The model shall consist or 24 strokes randomly distributed within 2 seconds, with the following characteristics: First Stroke Peak Amplitude, 200 KA Peak Rate or Rise, 140 KA/micro-second 6 2 Action Integral, 2 x 10 Amp - sec 23 Strokes Peak Amplitude, 50KA Peak Rate of Rise, 70KA/micro-second 6 2 Action Integral, each 0.062 x 10 Amp - sec MULTIPLE BURST (CLOUD TO CLOUD STRIKES) The model shall consist of 24 sets of 20 strokes randomly distributed within 2 seconds, with the following characteristics: Peak amplitude = 10 KA Peak Rate of Rise = 200 KA/Micro-second.
Disclaimer – This document is not exhaustive and it will be updated gradually. Page 30 TCDS A.064 ANNEX - Airbus A318, A319, A320, A321 - Special Conditions SPECIAL CONDITION S76 - 1 : Protection from the effect of HIRF APPLICABILITY: A318 / A319 / A320 / A321 REQUIREMENTS: JAR 25.1309 (a) and (b), JAR 25.1431 (a) ADVISORY MATERIAL: N/A The JAA Interim Policy INT/POL/25/2 dated Feb 10, 1992 gives a definition of: - the Certification HIRF environment - the Normal HIRF environment.
Add to JAR 25.1431 new paragraph (d): The aeroplane systems and associated components, considered separately and in relation to other systems, must be designed and installed so that: (d) (1) Each system that performs a critical or essential function is not adversely affected when the aeroplane is exposed to the Normal HIRF Environment.
(d) (2) All critical functions must not be adversely affected when the aeroplane is exposed to the Certification HIRF Environment.
(d) (3) After the aeroplane is exposed to the Certification HIRF environment, each affected system that performs a critical function recovers normal operation without requiring any crew action, unless this conflicts with other operational or functional requirements of that system.
Disclaimer – This document is not exhaustive and it will be updated gradually. Page 31