U.S. Department Advisory of Transportation CircularFederal Aviation Administration AC 25-21 DATE: 9/1/99
CERTIFICATION OF
TRANSPORT AIRPLANE STRUCTURE
Page Paragraph CONTENTS Number
11. Section 25.303
23. Section 25.305
[36-44]
CHAPTER 1. STRUCTURE Section 1. GENERAL
1. Section 25.301
[2-10]
[12-22]
[24-34]
35. Section 25.307
Loads1
a. Rule text1
b. Intent of rule1
c. Background1
d. Acceptable compliance methods1
e. References1
[RESERVED]1
Factor of safety2
a. Rule text2
b. Intent of rule2
c. Background2
d. Acceptable compliance methods2
e. References2
[RESERVED]2
Strength and deformation2
a. Rule text2
b. Intent of rule3
c. Background3
d. Acceptable compliance methods3
e. References3
[RESERVED]3
Proof of structure4
a. Rule text4
b. Intent of rule4
c. Background4
d. Acceptable compliance methods5
e. References5
[RESERVED]5
Section 2. FLIGHT LOADS
45. Section 25.321 General51
a. Rule text51
b. Intent of rule51
c. Background51
d. Acceptable compliance methods52
e. References52
[46-54] [RESERVED]52
Section 3. FLIGHT MANEUVER AND GUST CONDITIONS
55. Section 25.331 Symmetric maneuvering conditions103
a. Rule text103
b. Intent of rule104
c. Background104
d. Acceptable compliance methods104
e. References104
[56-64] [RESERVED]104
65. Section 25.333 Flight maneuvering envelope105
a. Rule text105
b. Intent of rule105
c. Background105
d. Acceptable compliance methods105
e. References105
[66-76] [RESERVED]105
77. Section 25.335 Design airspeeds105
a. Rule text105
b. Intent of rule107
c. Background108
d. Acceptable compliance methods108
e. References108
[78-86] [RESERVED]108
vi
87. Section 25.337 Limit maneuvering load factors108
a. Rule text108
b. Intent of rule109
c. Background109
d. Acceptable compliance methods109
e. References109
[88-96] [RESERVED]109
97. Section 25.341 Gust and turbulence loads109
a. Rule text109
b. Intent of rule111
c. Background111
d. Acceptable compliance methods112
e. References112
[98-108] [RESERVED]112
109. Section 25.343 Design fuel and oil loads112
a. Rule text112
b. Intent of rule112
c. Background112
d. Acceptable compliance methods113
e. References113
[110-118] [RESERVED]113
119. Section 25.345 High lift devices113
a. Rule text113
b. Intent of rule114
c. Background114
d. Acceptable compliance methods114
e. References114
[120-128] [RESERVED]114
129. Section 25.349 Rolling conditions114
a. Rule text114
b. Intent of rule115
c. Background115
d. Acceptable compliance methods115
e. References115
[130-137] [RESERVED]115
vii
138. Section 25.351 Yaw maneuver conditions116
a. Rule text116
b. Intent of rule116
c. Background116
d. Acceptable compliance methods117
e. References117
[139-147] [RESERVED]117
Section 4. SUPPLEMENTARY CONDITIONS
148. Section 25.361 Engine torque193
a. Rule text193
b. Intent of rule193
c. Background194
d. Acceptable compliance methods194
e. References194
[149-157] [RESERVED]194
158. Section 25.363 Side load on engine and auxiliary power unit mounts
.194
a. Rule text194
b. Intent of rule194
c. Background194
d. Acceptable compliance methods195
e. References195
[159-168] [RESERVED]195
169. Section 25.365 Pressurized compartment loads195
a. Rule text195
b. Intent of rule196
c. Background197
d. Acceptable compliance methods197
e. References197
[170-177] [RESERVED]197
178. Section 25.367 Unsymmetrical loads due to engine failure197
a. Rule text197
b. Intent of rule198
c. Background198
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d. Acceptable compliance methods198
e. References198
[179-187] [RESERVED]198
188. Section 25.371 Gyroscopic loads198
a. Rule text198
b. Intent of rule198
c. Background198
d. Acceptable compliance methods199
e. References199
[189-199] [RESERVED]199
200. Section 25.373 Speed control devices199
a. Rule text199
b. Intent of rule199
c. Background199
d. Acceptable compliance methods200
e. References200
[201-208] [RESERVED]200
Section 5. CONTROL SURFACE AND SYSTEM LOADS
209. Section 25.391 Control surface loads: general275
a. Rule text275
b. Intent of rule275
c. Background275
d. Acceptable compliance methods275
e. References275
[210-217] [RESERVED]275
218. Section 25.393 Loads parallel to hinge line275
a. Rule text275
b. Intent of rule276
c. Background276
d. Acceptable compliance methods276
e. References276
[219-227] [RESERVED]276
228. Section 25.395 Control system276
a. Rule text276
b. Intent of rule276
ix
c. Background276
d. Acceptable compliance methods277
e. References277
[229-238] [RESERVED]277
239. Section 25.397 Control system loads277
a. Rule text277
b. Intent of rule278
c. Background278
d. Acceptable compliance methods278
e. References278
[240-249] [RESERVED]278
250. Section 25.399 Dual control system278
a. Rule text278
b. Intent of rule278
c. Background278
d. Acceptable compliance methods279
e. References279
[251-259] [RESERVED]279
260. Section 25.405 Secondary control system279
a. Rule text279
b. Intent of rule279
c. Background279
d. Acceptable compliance methods279
e. References279
[261-268] [RESERVED]279
269. Section 25.407 Trim tab effects280
a. Rule text280
b. Intent of rule280
c. Background280
d. Acceptable compliance methods280
e. References280
[270-275] [RESERVED]280
276. Section 25.409 Tabs280
a. Rule text280
b. Intent of rule281
c. Background281
d. Acceptable compliance methods281
e. References281
[277-286] [RESERVED]281
x
287. Section 25.415 Ground gust conditions281
a. Rule text281
b. Intent of rule282
c. Background282
d. Acceptable compliance methods282
e. References282
[288-297] [RESERVED]282
298. Section 25.427 Unsymmetrical loads283
a. Rule text283
b. Intent of rule283
c. Background283
d. Acceptable compliance methods283
e. References283
[299-307] [RESERVED]283
308. Section 25.445 Auxiliary aerodynamic surfaces284
a. Rule text284
b. Intent of rule284
c. Background284
d. Acceptable compliance methods284
e. References284
[209-318] [RESERVED]284
319. Section 25.457 Wing flaps284
a. Rule text284
b. Intent of rule284
c. Background285
d. Acceptable compliance methods285
e. References285
[320-328] [RESERVED]285
329. Section 25.459 Special devices285
a. Rule text285
b. Intent of rule285
c. Background285
d. Acceptable compliance methods285
e. References285
[330-339] [RESERVED]285
xi
Section 6. GROUND LOADS
340. Section 25.471 General361
a. Rule text361
b. Intent of rule361
c. Background361
d. Acceptable compliance methods362
e. References362
[341-349] [RESERVED]362
350. Section 25.473 Landing load conditions and assumptions362
a. Rule text362
b. Intent of rule362
c. Background363
d. Acceptable compliance methods363
e. References363
[351-361] [RESERVED]363
362. Section 25.477 Landing gear arrangement363
a. Rule text363
b. Intent of rule363
c. Background363
d. Acceptable compliance methods363
e. References363
[363-369] [RESERVED]363
370. Section 25.479 Level landing conditions364
a. Rule text364
b. Intent of rule365
c. Background365
d. Acceptable compliance methods365
e. References365
[371-380] [RESERVED]365
381. Section 25.481 Tail down landing conditions365
a. Rule text365
b. Intent of rule366
c. Background366
d. Acceptable compliance methods366
e. References366
[382-389] [RESERVED]366
xii
390. Section 25.483 One gear landing conditions366
a. Rule text366
b. Intent of rule366
c. Background366
d. Acceptable compliance methods367
e. References367
[391-398] [RESERVED]367
399. Section 25.485 Side load conditions367
a. Rule text367
b. Intent of rule367
c. Background367
d. Acceptable compliance methods367
e. References367
[400-409] [RESERVED]367
410. Section 25.487 Rebound landing condition368
a. Rule text368
b. Intent of rule368
c. Background368
d. Acceptable compliance methods368
e. References368
[411-420] [RESERVED]368
421. Section 25.489 Ground handling conditions368
a. Rule text368
b. Intent of rule368
c. Background368
d. Acceptable compliance methods369
e. References369
[422-434] [RESERVED]369
435. Section 25.491 Taxi, takeoff, and landing roll369
a. Rule text369
b. Intent of rule369
c. Background369
d. Acceptable compliance methods369
e. References369
[436-446] [RESERVED]369
447. Section 25.493 Braked roll conditions370
a. Rule text370
b. Intent of rule371
xiii
c. Background371
d. Acceptable compliance methods372
e. References372
[448-458] [RESERVED]372
459. Section 25.495 Turning372
a. Rule text372
b. Intent of rule372
c. Background372
d. Acceptable compliance methods372
e. References372
[460-468] [RESERVED]372
469. Section 25.497 Tail-wheel yawing372
a. Rule text372
b. Intent of rule373
c. Background373
d. Acceptable compliance methods373
e. References373
[470-477] [RESERVED]373
478. Section 25.499 Nose-wheel yaw and steering373
a. Rule text373
b. Intent of rule374
c. Background374
d. Acceptable compliance methods374
e. References374
[479-482] [RESERVED]374
483. Section 25.503 Pivoting374
a. Rule text374
b. Intent of rule374
c. Background374
d. Acceptable compliance methods375
e. References375
[484-488] [RESERVED]375
489. Section 25.507 Reversed braking375
a. Rule text375
b. Intent of rule375
c. Background375
d. Acceptable compliance methods375
e. References375
[490-495] [RESERVED]375
xiv
496. Section 25.509 Towing loads375
a. Rule text375
b. Intent of rule376
c. Background377
d. Acceptable compliance methods377
e. References377
[497-508] [RESERVED]377
509. Section 25.511 Ground load: unsymmetrical loads on multiple-wheel
units377
a. Rule text377
b. Intent of rule378
c. Background378
d. Acceptable compliance methods379
e. References379
[510-519] [RESERVED]379
520. Section 25.519 Jacking and tie-down provisions379
a. Rule text379
b. Intent of rule379
c. Background379
d. Acceptable compliance methods380
e. References380
[521-528] [RESERVED]380
Section 7. WATER LOADS
529. Section 25.521 General455
a. Rule text455
b. Intent of rule455
c. Background455
d. Acceptable compliance methods455
e. References455
[530-540] [RESERVED]455
541. Section 25.523 Design weights and center of gravity
positions455
a. Rule text455
b. Intent of rule456
xv