1、MIL-C-7979B 21 OCTOBER 1959 SUPERSEDING MIGG7979A 23 JULY 1956 MILITARY SPECIFICATION CYLINDERS; HYDRAULIC BRAKE, MASTER, POWER ASSISTED This specificatiox has been approved bg the Departinent of Defense awd is man.- dUt0mJ for me by the Departments of the Amy, the Navy, and the Air Fome. 1. SCOPE M
2、IL-B-8584 -Brake Systems, W h e e 1, Aircraft, Design of. 1.1 This specification covers hydraulic M.IL-H-8775 - Hydraulic S y s t e m Components A i r- craft, G e n e r a 1 Specification for. power assisted master brake cylinders de- signed for use in aircraft hydraulic wheel brake subsystems which
3、operate at O to 1,500 pounds per square inch psessure and are wed in airplane hydraulic systems having STANDARDS power input pressures up to 3,000 pounds pei square inch. MILITARY 2. APPLICABLE DOCUMENTS 2.1 The following documents, of the issue MIGSTD-1U5 - Sampling Psocedures and Tables for In- in
4、 effect on date of invitation for bids, form spection by Att G e n - eral Tests for. MIL-H-5606 - Hydraulic Fluid, Pe- troleum Base, Ais- craft and Ord- nance. (Copies of specifications, standards, drawings, and publications required by contracbrs in connection with specific procurement functions sh
5、ould be ob- tained from the procuring activity or as directed by the contracting officer.) 3. REQUIREMENTS 3.1 Preproduction sample. Prior to begin- ning quantity production, prepsoduction samples shall be subjected to preproduction testing. The preproduction sample shall be produced by the same met
6、hod and of the Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-893110 materid that will be used for quantity production of the item. 3.2 General. The requirements of Specifi- cation M1LI-I-8776 apply as requirements of this specification, with the ex
7、ceptions and additions specified herein. When the two specifications conflict, this specification shall govern. Unless otherwise specified by the prociiring activity, the brake cylinders shall not bo used with any fluid other than that conforming to the requirements of Specification MIL-X-I-5f306. 3
8、.3 Design and construction. 3.3.1 The design of hydraulic power assist- ed master brake cylinders shall include the following : (a) A mechanically actuated pressure generator, (b) A control unit whereby fluid under pressure is used to boost the out- put of the pressure generator and provides input f
9、orce reac- tion (load-feel) . (c) A common communication line with the reservoir for the pressure generator and the power system return fluid. 3.3.1.1 The abovo features, where practi- CRI, shall be combined into one unit operable by the pilots brake peclal, A suitable means for attaching lhe brake
10、cylinder to the air- plans stittictiire and the operating linkage shall be inclticled in the design, See figure 1. 3.3.2 hptit piesszJYe. The unit shall be de- signed for an input pressure of 3,000 pouncls peil scliiiwe inch, 3.3.8 utput pressures, Output pressures shall FM those “power on” and “pow
11、er off brake operating pressures which are re- quired by the specific brake system being considered. 2 3.3.4 Boost ratio. The ratio of the output pressure generated by a given actuating force with power on, to the output pressure generated by the same given actuating force with power off, shall be k
12、nown as the boost ratio of the unit, and the boost ratio shall be such that the required output pressures can be generated. 3.3.5 Structzcral s“trength. The operation of the brake cylinder shall not be impaired, and no part of the unit or its mountings shall give evidence of failure under #the limit
13、 ap- plied mechanical operating forces for a given airplane installation or for the wrench- torque loads required for making the neces- sary connections. 3.3.6 Power assht cutoff. Power assist shall cease when the power-on -output pres- sure reaches a predetermined value as gov- erned by the specifi
14、c requirements of the brake system being considered (see fig- ure 2). 3.3.7 Brake line output. Means shall-be provided for limiting the output pressure of the brake cylinder with power on, to a value of the brake burst pressure divided by 1.67 (see figure 2). The force which shall be ap- plied to th
15、e unit for determining the limiti ing output pressure shall be that which cor- responds to the limit applied force at the brake pedal as defined in Specification MIL- B4584. 3.3.8 Bleeding. Provisions shall be made in the design of the brake cylinder such that, with no mechanical force applied to th
16、e pres- sure generator, aqy entrapped air can be bled from the unit. This may be accomplish- ed by proper internal design and does not necessarily require an external bleed port. A power bleeding feature whereby fluid from the pressure port can pass through the unit of the brake port is also require
17、d. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-C-7979B PRESSURE POINT OF ATTACHNENT TO AIRPLANE STRUCTURE RETURN PORT i L I- l f- BLU (OIJTPUT) %/ PORT 7- I I r POINT OF ATTACHMENT TO ATRPLANE BRAKE PEDAL -LINKAGE FOR APPLICATION OF ACTUATING
18、 FORGE F FIGURE 1. Cglinder; hgdraulic maste.r, brake, power asI given airplane installation shall then be taliplied to the unit while it is in the mid- travel position and held for a period of O riiiiutos. A levcr systcin mid weights may il:! iicecl to apply the force to the iiiiit. This teat shall
19、 ho repeated allowing for escape of fluid froin the pressure pewratw section in orcicr that the test load is applied when the actuating shzt is at a position Pepresenting 75 liercent of the stroke. There shall be no exteiml leaktzgc?. pei.manent distortion, fail- we, or malfunctioning of any part of
20、 the unit. 4.6.5 Smtnined force fmction. The brakc 1iort shall be connected to a gage, id input pressiire shall be applied to the pressure port with th return port connected to the re- seiavoip. Tho pessurs? gencratoi* shall then be lonciecl at approximateIy the midtravel posi- tion using an operati
21、ng lever and weights. Tho qicrating lever weizhts shall correspond to 25 percent followed by 100 percent of the pi- lot effort which corresponds to the maximum power-on output l)ressui*e. At each loacl, the atitput pressure shall be within k5 percent o the design maximum power-on output presuiire. A
22、 slow fuctiintioii of the output pressure is permissible. This flcctuation pces- stire range shall not exceed 5 percent of the design niiiximuin power-on output pressure. The leakage out the reservoir prt during this test shall not exceed 2 ciibic incies per minute after the first minute, and the po
23、si- tion of the piston shall remain unchanged. Tho duration of tlie test shall be 2 minutes at each o$ the 2-rod loads. When the load IS removed, al1 moving parts of the brake cylinder shall r0tiirn to the full off position, Tho test shall be repeated twice for the Pre- production tests. 8 4.6.6 Pow
24、er cutoff. A .test shall be con- ducted to determine the output pressures developed with various actuating forces ap- plied to the brake cylinder. A curve shall then be plotted to show that power assist ceases at the maximum power-on output pressure (see figure 2). For Individual tests, any means wh
25、ereby the proper cutoff func- tion may be observed will be acceptable. 4.6.7 Pzmping fwztzon. With zero psi at the input pressure port, the reservoir return port of the control unit shall be connected to a supply reservoii* and the brake port to a simulated brake consisting of a cylinder having a sp
26、ring-loaded piston. Line lengths, types, and sizes, together with reservoir head pressure used (or intended to be used) in the airplane installation shall be simulated in the test. The simulated brake shall re- quire a minimum hyclraulic pressure of 30 psi for initial movement of the piston, after w
27、hich pressure reaction shall increase linear- ly with displacement, Peaching at least 200 psi after having been displaced by a volume equivalent to 200 the unit shall be operated to con- tact the stop at the end of travel of the pressure generator. A free and continuous flow shall QCCUF out the brak
28、e pod. 4.6.10 Extrente temperature. 4.6.10.1 Gei2em2, The brake cylinder hav- ing all critical fits within 10 percent of the minimum allowed clearances as specified by the detail drawing tolerances shall be sub- jected to the extreme temperature tests as described below. A tabulation of the actual m
29、easured dimekions of the critical mating parts, together with the limit dimensions specified by the detail drawings, shalI be in- cluded in the test report. Transfer cylin- ders may be used to supply the volumes of stabilizeci temperature input fluid required for these tests. 4.6.10.2 H4gh temperatu
30、re, The brake cyl- inder anci its operating fluid shall be contain- ed in a chamber having an ambient temper- ature of 160 -cOF. for 24 hours. The test cylindei* shall then be subjected to the tests of this specification entitled Pumping func- tion (4.6.7) and Sustained force function (4.6.6) , and
31、it shall satisfactorily pass these tests. 4.6.10.3 LOTU teitLpercitzwe. The brake cyl- inder niid its operating fluid shall be con- tained in n chamber having an ambient tem- perature of -6tiOF. maximum for 24 hours, during which time a fiuid head of 2 psi shall be applied to dl the ports. There sha
32、ll be no external leakage. The unit shall then be sub- jected to the tests of this specification entitled Sustained force function (4.6.5) . In addition, the action of the unit shall be observed for any indication of binding, and any function- ing different from that at normal temper- attires shall
33、be reported. 4.6.10.4 Rapid uartiizq. The test chamber shall be warmed rapidly from the -65OF. temperature to the +160F. temperature. 10 A record of the test chamber temperature and the input and output fluid temperatures shall be maintained. The test entitled Sus- tained force function (4.6.5) shal
34、l be re- peated at 6-minute inteivals during the wamup, and the operation of the cylinder shall be observed for any indication of bind- ing or functioning different from that at nomal temperatures. This test may be ended after the test chamber ambient temperature has been stabilized at 16O0F. and th
35、e tem- perature of the input operating fluid, meas- ured at the cylinder return port, has in- creased to 100OF. 4.6.11 Endurance. The brake cylinder shall be tested for endurance as follows: (a) The test cylinder having all critical fits within 10 percent of the maxi- mum allowed clearances as speci
36、- fied by the detail drawing toler- ances shall be used for the En- durance test. (b) Prior to the test, the test cylinder shall be hot-soaked for 7 days in the applicable hydraulic fluid at a temperature of 160OF. if it con- tains packings not of the type or glands not of the design which complies
37、with the requirements of the applicable listed specifica- tions. (c) The test cylinder shall be mounted in the test fixture in its normal operating position. (d) Each cycling stroke shall be 90 per- cent minimum of the total stroke of the pressure generator, (e) The maximum power-on output pressure
38、or a greater pressure shall be generated for 20,000 cycles; and one half of the maxi- mum power-on output pressure shall be generated for an addi- tional 80,000 cycles. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-/ MIL-C-7777B Lb W 9977706 OL63b4
39、 7 W (f) The unit shall pump 25 percent of the pressure generator volume through a relief valve during each cycle. (g) The movement of the unit during the return stroke of each cycle shall not be externally assisted. (h) The rate of cycling shall be as rapid as the test conditions will permit. (i) P
40、rior to the Endurance test, after 20,000 and 60,000 Endurance test cycles, and at the conclusion of the Endurance test, the test cyl- inder shall be subjected to the tests of this specificartion entitled Individual tests, and the results shall be tabulated in detail in the test report (4.4). (j) The
41、 test of this specification en- titled Boost ratio (4.6.13) shall be performed prior to and at the end of the Endurance test. (k) The actual dimensions of ,the test cylinder parts which undergo relative motion shalI be recorded before and after the test. These dimensions, along with the dif- ference
42、 between the two dimen- sions (wear) and the limit dimen- sions specifred by the detail draw- ings, shall be tabulated in detail and included in the test report (4.4). (1) All parts of the test cylinder shall be inspected before and a$ter the test. A comparison of the condition of the parts shall th
43、en be made and in- cluded in the report. 4.6.12 Efficiency. 4.6.12.1 Volumetric effkiency (power off). The fluid displacement (power off) of the brake cylinder shall be measured by direct- ing the output flow through a relief valve MILC-7979B set at the maximum power-off pressure, into a fluid gradu
44、ate. The average value of dis- placement per stroke, for 5 successive LOO- percent strokes of the unit, shall be not less than the rated displacement of the unit. 4.6.12.2 Mechanical efficiency (power off). The brake cylinder shall be mounted in a test fixture with means provided for measuring. the
45、mechanical force applied to the unit. The unit shall then be operated (power off) through at least 90 percent of its available stroke to produce the maximum power-off output pressure, and the mechanical force of the unit required to produce this pressure shall be measured. The ratio of the force cal
46、culated to produce the same hydraulic pressure in the unit, neglecting packing, mechanical friction, and return mechanism forces, to the force actually required, shall be known as the mechanical efficiency. The contradtor shall establish the acceptable effi- ciency for each application, and test res
47、ults shall be included in the data submitted as required under 4.4. Efficiency (percent) = Calculated force (lb) X 100 Actual force (lb) (1) 4.6.13 Boost ratio. The brake cylinder shall be mounted in a test fixture with a means provided for applying various actuating forces to the cylinder. An input
48、 pressure source shall be connected to the pressure port, and a suitable gage shall be connected to khe brake port, Actuating forces from zero to the force required to produce the maximum power on output pressure shall be applied to the unit in 25-percent incre- ments of the force required to produc
49、e the maximum power on output pressure. At each actuating force, the output pressure developed ihall be recorded, and a curve of the actuating force versus the output pres- sure shall be plotted. The test shall then be repeated with the power off using the sama actuating forces as with ihe power on, The Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MILGi979B boost ratio shall then be calculated from the application, and test re
