1、MIL-A-8861B(AS)7 February 1986SUPERSEDINGMIL-A-8861(ASG)18 May 1960(See section 6.4)MILITARY SPECIFICATIONAIRPLANE STRENGTH AND RIGIDITYFLIGHT LOADSThis specification is approved for use within the Naval Air SystemsCommand, Department of the Navy, and is available for use by allDepartments and Agenc
2、ies of the Department of Defense.1. SCOPE1.1 Scope. This specification covers the requirements for strength andrigidity for flight loading conditions applicable to airplanes.2. APPLICABLE DOCUMENTS2.1 Government documents.2.1.1 Specifications. The following specifications form a part of thisspecific
3、ation to the extent specified herein. Unless otherwise specified, theissues of these documents shall be those listed in the issue of the Departmentof Defense Index of Specifications and Standards (DODISS) and supplementthereto, cited in the solicitation.AMSC N/A FSC 1510DISTRIBUTION STATEMENT A. App
4、roved for public release; distribution is unlimited.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-A-8861B(AS)SPECIFICATIONSMILITARYMIL-D-8706 Data and Tests, Engineering, Contract Require-ments for Aircraft Weapon Systems.MIL-D-8708 Demonstrati
5、on Requirements for Airplanes.MIL-A-8860 Airplane Strength and Rigidity General SpecificationforMIL-A-8866 Airplane Strength and Rigidity, ReliabilityRequirements, Repeated Loads, and Fatigue.MIL-A-8867 Airplane Strength and Rigidity, Ground Tests.MIL-A-8868 Airplane Strength and Rigidity, Data andR
6、eports.2.1.2 Other Government documents (publications). The following otherGovernment documents (publications) form a part of this specification to theextent specified herein. Unless otherwise specified, the issues shall bethose in effect on the date of the solicitation.PUBLICATIONSAIR FORCESEG TR 6
7、5-04 Environmental Conditions to be Considered in theStructural Design of Aircraft required to Operate atLow Levels.SEG TDR 67-28 Development of Improved Gust Load Criteria forUSAF Aircraft.(Copies of specifications and other Government documents (publicationsrequired by contractors in connection wi
8、th specific acquisition functionsshould be obtained from the contracting activity or as directed by thecontracting officer.)2.2 Order of precedence. In the event of a conflict between the text ofthis specification and the references cited herein, the text of thisspecification shall take precedance.N
9、othing in this specification, however,shall supersede applicable laws and regulations unless a specific exemptionhas been obtained.3. REQUIREMENTS.3.1 Applicability. Except as otherwise specified, the requirementsspecified herein apply to the complete airplane structure. Within thespecified ranges o
10、f center of gravity position, strength is required for thespecified values of the parameters and any lesser or intermediate values whichmay be critical and which are practicable of attainment.2Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-A-886
11、1B(AS)3.1.1 Cross Weight. The design gross weights for the flight loads andloading conditions specified herein shall be all gross weights fromthe minimum flying gross weight to the maximum design gross weight. Forweights up to the basic flight design gross weight, strength shall beprovided for all c
12、onditions for the values of parameters specified for thebasic flight design gross weights. At higher weight, strength shall beprovided for by maintaining a constant mass times load factor (nzW) product,except that the load factor shall be not less than that specified in Table Ifor the maximum design
13、 gross weight.TABLE I. Symmetrical flight parameters3Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-A-8861B(AS)3.1.1.1 Height distributions. The weight distributions for the basic,high drag, drive recovery, landing approach, and takeoff configur
14、ation shallbe all those that are critical as a result of all practicable symmetrical andasymmetrical distributions and shall be determined by consideration of allpossible arrangements of variable, disposable, and removable items, includingexternal stores, for which provision is required (including b
15、allast requiredfor structural demonstration tests) within the airplane strength andaerodynamic controllability limits.3.1.2 Center of gravity positions. The design center of gravity positionsat each weight and each aerodynamic configuration (position of variablegeometry surfaces, size and location o
16、f external stores) shall include atolerance beyond the actual maximum-forward and actual maximum-aft positions.Included shall be all weights and aerodynamic configurations which areattainable as a result of all practical symmetrical and asymmetricaldistributions of useful load up to the maximum desi
17、gn weight, airplaneattitudes and accelerations, fuel sequencing, and airplane flexibility. Thistolerance shall be + 1.5 percent of mean aerodynamic chord (MAC) or 15 percentof the distance between the most forward and most aft actual values from thecomplete center of gravity (CG) envelope, whichever
18、 is greater. Thistolerance shall be applied so as to move the design center of gravitiesforward of the actual most forward position and aft of the actualmost aft position. For airplanes with variable sweep wings, the reference MACshall be that for the wings landing or take-off position.3.1.2.1 Balla
19、st support-structure. When sufficient ballasts supportstructure strength cannot be identified and located for ballast weightdistribution necessary to meet the specified CG requirements with thespecified tolerances, the contractor may use a finite element distribution ofthe ballast weight throughout
20、the forward or aft portions of the fuselage, asappropriate. When a finite element distribution is used, strength provisionsshall be made and appropriately defined for the support-structure(s) for theballast weight(s) to allow for a 1.0 percent MAC tolerance on the maximumforward and aft design CG. T
21、his deviation shall apply for the design ofballast weight support-structure only.3.1.3 Aerodynamic configurations. For the flight load conditions of thisspecification, unless otherwise specified, all devices such as, but notlimited to flaps, slats, slots, cockpit enclosures, landing gear, speedlimit
22、ing devices, and bomb-bay doors shall be in their closed or retractedpositions. Alternately:a. Speed limiting devices (including landing gear, if it isused as a speed limiting device) and bomb-bay doors shall bein the full open or extended positions as limited by avail-able actuating (operating or h
23、olding) force or power, and,alternately, in all critical intermediate positions.4Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-A-8861B(AS)b. Aerodynamic devices used for maneuvering in flight otherthan take-off and landing, such as variable-pos
24、ition aerodynamicsurfaces which provide for changes in altitude, attitude,translational motion, roll, or camber, shall be in themaximum open or extended position for its scheduled programplus a tolerance of 50 percent on surface(s) deflections andmaximum surface(s) rate of deflection, and, alternate
25、ly, inall critical intermediate positions or stalled positions ifinsufficient power is available to achieve its scheduled position.Scheduled position shall include all commanded error signals andflight control time lags and possible air data computer sensorerrors.c. For airplanes having variable geo
26、metry surfaces, such aswing sweeping, variable camber or variable position thrustdevices, such as thrust-directed controls or engine nozzles,these surfaces or devices shall be in all positions within thelimits of their scheduled program of travel3.1.3.1 Stores configurations.3.1.3.1.1 Carriage. The
27、load factors at store stations shall be thoserequired at the appropriate design gross weight at the particular storelocation which includes the loads resulting from the structural dynamicresponses between the airframe and the rack-store installation. For externalstore installation, the angular rates
28、 and acceleration with basic mission loadand with heavier store items shall be those resulting from the requirements of3.3 and 3.4.3.1 .3.1.2 Programmed release of stores. The programmed release of allcombinations of stores by devices such as computers, or other electronic, orelectro-mechanical devi
29、ces, under any flight conditions including the effectsof firing of ejection racks (if required) and “G-jump”, shall not result inthe limit strength of the airplane being exceeded. For attack (VA) airplanes,limit strength shall be provided to include the “G-jump” and ensuing loadmagnification effect
30、after an initial release load factor of 6.0 or itsappropriate nzW product; this condition shall be considered for theprogrammed release of all combinations of stores. The gross weight shall bethat for the maximum stores loading less 40 percent fuel.3.1.3.1.3 Emergency stores release. Emergency relea
31、se of the mostcritical combinations of stores shall not result in unacceptable aircraftmotions or exceedance of limit strength of the airplane for the followingconditions:a. At speeds up to the maximum permissible speed for suchrelease with all values of vertical load factor between0.5 and 2.0.5Prov
32、ided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-A-8861B(AS)b. At speeds up to landing, approach, and take-off limitspeed (VLF), with devices extended or open in theirmaximum open or extended position for take-off, with allvalues of vertical load fact
33、or between 1.0 and 1.5.3.1.4 Air speeds. The airspeeds shall be those specified and anyattainable lesser or intermediate air speeds that result in critical loads.3.1.5 Altitudes. The altitudes used for the determination of flightloading conditions, other than take-off and landing approach, shall be
34、all thealtitudes that result in critical loads from sea level to those altitudes atwhich the limit equivalent air speed (EAS) and Mach number are maximums ormaximum performance (Cruise Altitude) requirement. Sea level shall be usedfor landing approach and take-off.3.1.6 Power settings. The power or
35、thrust for the conditions of thisspecification, including gusts combined with manuevers, shall be all valuesbetween zero and the maximum attainable using thrust augmentation or auxiliarypower devices, except that for consideration of air speeds applicable togusts, the power need not exceed normal ra
36、ted for reciprocating engines andmilitary thrust (non-afterburning) for all gas turbine engines.3.1.7 Pressurization. The limit pressure differential between pressurizedportions of the structure and the ambient atmosphere shall be:a. 1.33 times the maximum attainable pressure combined with1-G flight
37、 loads. The maximum attainable pressure shall bedefined as limited by the pressurization safety valve(s), plusthe tolerance limit on the safety valve(s).b. Zero and the maximum attainable pressure combined withflight loads.c. 1.33 times the maximum attainable pressure combined withthe loads due to g
38、round test support equipment forpressurization tests.3.1.8 Airload distributions. The distributions of airloads used in thestructural design shall be those determined by the use of acceptableanalytical methods and by the use of aerodynamic data which are demonstratedto reapplicable as approved by th
39、e acquisition activity. These data shallinclude the effects of Mach number, deformation of the surface due toaeroelasticity and thermoplastic effects, and nonlinear effects such as buffet.3.1.9 Positions of adjustable fixed surfaces. For each airplaneconfiguration associated with the loading conditi
40、ons of this specification,the position of fixed surfaces, which are adjustable in flight or on the6Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-A-8861B(As)ground shall be the extreme positions of the available range of settings ofthe configura
41、tion as limited by positive stops and also for all criticalpositions within that range.3.1.10 Positions of cockpit enclosures, bomb-bay doors, landing gear anddoors, dive recovery devices, and cowl flaps. Loads on cockpit enclosures,bomb-bay doors, landing gear and doors, dive-recovery devices, and
42、cowl flapsshall be those resulting from the loading conditions of this specification forthe fully opened, intermediate positions, and fully closed positions up to thelimit speed for which operation of these components is required. If theairplanes aerodynamic characteristics are significantly affecte
43、d by thepositions of these items, the loads on the airplane shall be those resultingwith these items fully opened as well as fully closed, considering each itemindividually.3.1.11 Torque on primary control surfaces. The torque on primary controlsurfaces resulting from the loads and loading condition
44、s of this specificationshall be modified as follows:a. Neglect the torque resulting from airloads forward of thehinge line of the control surface when this results in morecritical torque by assuming that these airloads act at thehinge line, andb. Assume tabs, other than those which can move relative
45、 to theirassociated surfaces only by virtue of the movement of theassociated surfaces, are in those positions within theirlimits of travel which result in the most critical torqueon the control surface, except that,c. In those cases where the requirements of 3.1.11a and b,result in hinge moments gre
46、ater than those which can besupplied by the control systems, the requirements of 3.1.11aand b, shall be modified, as necessary, in order that theresultant hinge movements are equal to those that can besupplied by the control systems, except 3.1.13. For thepurpose of this requirement, the hinge momen
47、ts that can besupplied by the control systems shall be those that resultfrom application of the limit pilot-applied cockpit controlforces in the case of manual or boosted controls or those thatresult from maximum control power or surface authority in thecase of powered systems. The manner in which t
48、he requirementsof 3.1.lla and b, are modified shall be such that thecritical distributions of torque, consistent with the maximumspecified value of resultant torque, are obtained.7Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-A-8861B(AS)3.1.12
49、Tab loads. Tabs shall be in all positions within their limit oftravel at all speeds up to the limit speed. The associated control surfacesshall be in their neutral positions. The local angle of attack of the tabsassociated fixed surface shall be zero. Airloads on portion of the airplaneother than tabs may be neglected.3.1.13 Unsymmetrical horizontal tail loads. The airloads on thehorizontal tail for symmetrical flight conditions and symmetrical gu
