APPENDIX 1
PROCEDURE FOR EVALUATING PULSE SHAPES 1 This graphical procedure may be used to evaluate the impact pulse shape acquired from a test.
While this procedure is based on graphical concepts, an accurate evaluation of the pulse parameters should be obtained using the digitized data and computer algorithms that provide the analysis illustrated in the following steps:
2. On the plot of the acquire pulse, identify the peak deceleration point, Gpk, and points on the onset of the pulse equal to 0.1 Gpk and 0.9 Gpk. Construct an onset line through the points 0.1 Gpk and 0.9 Gpk. Extend the constructed onset line to the base line of the data plot, C=O. Identify the intersection of the constructed onset line and baseline as the start of the acquired pulse, Tl. For the acquired pulse to be acceptable, the magnitude of Gpk must equal or exceed the minimum required pulse, Greq for the specified test condition.
3. Using T1 as the start time, construct the ideal pulse required for the test condition. Draw a vertical line and a horizontal line through the peak of the ideal pulse, Greq. The vertical line through Greq will intersect the time axis at the maximum allowed rise time, T 3. Draw another vertical line at the first intersection of the horizontal line through Greq and the acquired pulse after T 1. This vertical line will intersect the time axis at T 2. The actual rise time, Tr = T 2 – T1, must be less than or equal to Treq for the acquired pulse to be acceptable.
4. Compute the velocity change, Vra, of the acquired pulse during the interval T 1 to T 3. Note that T 3 will usually occur after the peak, Gpk, of the acquired pulse. For the acquired pulse to be acceptable, Vra must be at least one-half the total velocity V, required for the specified test condition.
5. If the total velocity change for the test is calculated from the acquired pulse, use the interval starting at T1 and ending:
a. At the point T4, where the acquired pulse first intersects the baseline, G = 0, after the time of Gpk, or
b. At the time equal to: TI+ 2.3x Treg, whichever occurs first.
Sled Impact Pulse
5.0 i Treq ideal Pulse
5.0 Greq Gpk 100 150 200 250 300 350 Time (Milliseconds) Figure 3
Sled Impact Pulse
5.0 Treq T1 +ị2.3 X Tịeq
0.0 -5.0
- 10.0
- 15.0 -20.0 +
• 50 100 150 200 250 300 350 Time (Milliseconds) Figure 4 4
6. Construct a line parallel to the ideal pulse and offset by 2 G's in magnitude less than the ideal during the time interval between T1 and T2. If the magnitude of the acquired pulse is 2 G's less than the ideal at any point during the interval between T1 and T2, the pulse is not acceptable. Figure 2 is an example of an .acceptable pulse shape. The acquired pulse shown in Figure 5 is unacceptable.
APPENDIX 2
SEAT DEFORMATION
1. General Seats that are evaluated in accordance with the tests discussed in this AC may deform either due to the action of discrete energy absorber systems included in the design or due to residual plastic deformation of their structural components. If this deformation is excessive, it could impede the airplane emergency evacuation process.
Each seat design may differ in this regard and should be evaluated according to its unique deformation characteristics.
If floor deformations are applicable, consistency in pre and post -test measurements shall be maintained. If the pretest measurements are made before floor deformations are applied, the post -test measurements shall be made- after floor deformations have been removed. Conversely, if the pretest measurements are made after floor deformations are applied, the post -test measurements shall be made before removal of floor deformations.
2. Fixed Seats . The following post -test deformations and limitations regard ing emergency exit egress may be used for showing compliance with §§ 25.561(d) and 25.562(c)(8). Dimensions specified for undeformed seat rows assume the maximum permanent deformation discussed below, and are given to enable evaluation of an installation without having to make reference to test reports. In those cases where the actual permanent deformations are less than maximum, the specified dimensions for undeformed seat rows could be correspondingly decreased.
a. Forward or Rearward Directions. Seats that exhibit forward or rearward deformations should not exceed a maximum of 3.0 inches (75 mm). In this case, the clearance between undeformed seat rows, measured as shown in Figure 1, Dimension A, of this appendix, should be 9.0 inches (228 mm) or, alternatively, 6.0 inches (150 mm), plus the actual fore/aft deformation. Seat rows that lead to Type III exits are subject to the specific access requirements for those exits. This will result in greater spacing at those seat rows in the undeformed case. For seats with deformations that exceed 3.0 inches, the undeformed clearances should be increased accordingly. In addition, at seat rows leading to Type III or IV exits, 20 inches (508 mm) minimum clearance, measured above the arm rests, shall be maintained between adjacent seat rows. This measurement may be made with the seat backs returned to their upright position, using no more than original seat back breakover forces, typically 25-35 pounds (111-155 N). At other seat rows, the most forward surface of the seat back shall not deform to a distance greater than one half the original distance to the forwardmost hard structure on the seat (see Figure 2 of this appendix).
b. Downward Direction. There is no limitation on downward permanent deformation, provided it can be demonstrated that the feet or legs of occupants will not be entrapped by the deformation.
c. Seat Rotation The seat bottom rotational permanent deformation shall not result in an angle that exceeds 20 degrees pitch down or 35 degrees pitch up from the horizontal plane. This rotational deformation shall be measured between the fore and aft extremities of the seat pan 1
at the centerline of each seat bottom (Figure 3 of this appendix). Rotation of the seat pan shall not cause entrapment of the occupant.
d. Sideward Direction.
(1) The deformed seat should not encroach more than 1.5 inches (38 mm) into the required longitudinal aisle space at heights up to 25 inches (635 mm)above the floor. The determination of which parts of the seat are at what heights is determined prior to testing.
(2) The deformed seat should not encroach more than 2.0 inches (50 mm)into the longitudinal aisle space at heights 25 inches (635 mm) or more above the floor.
e. Additional Considerations. In addition, none of the above deformations shall permit the seat to:
(1) Affect the operation of any emergency exit or encroach into an emergency exit opening for a distance from the exit not less than the width of the narrowest passenger seat installed in the airplane.
(2) Encroach into any required passageway.
(3) Encroach more than 1.5 inches (38 mm) into any cross -aisle or flight attendant assist space.
f. Deployable Items . Certain items on the seat, such as food trays, legrests, arm caps over in -arm tray tables, etc., are used by passengers in flight and are required to be stowed for taxi, takeoff and landing. Deployment of such items should be treated as "permanent deformation" if the item deploys into an area that must be used by multiple passengers (in addition to the occupant of the seat) for egress. Such deployments can be considered acceptable, even if they exceed the dimensions specified above, if they are readily pushed out of the way by normal passenger movement, and remain in a position that does not affect egress.
3. Stowable Seats . Stowable seats, that may impede egress, must stow post -test and remain stowed to the extent necessary in order to satisfy the above criteria.
a. Seats that are Stowed Manually . A post -test stowage force no greater than 10 pounds (451 above the original stowage force may be used to stow the seat.
b. Seats that Stow Automatically . For a seat that may interfere with the opening of any exit, it must automatically retract to a position where it will not interfere with the exit. For determining encroachment into passageways, cross -aisles, andassist spaces, a post -test stowage force no greater than 10 pounds (45 N), applied at a single point, may be used to assist automatic retraction .
(Measurement to be taken over full width of seat bottom cushion) Figure 1 Pre-test Condition Post-Test Condition Dimension "C" must be at least 50 percent of Dimension "B" Figure 2 3
UNDEFORMED SEAT
DEFORMED SEAT
PITCH DOWN ANGLE SEAT PAN HORIZONTAL SECTION A-A
FROM HORIZONTAL NOT TO EXCEED 20° FLOOR
UNDEFORMED SEAT
SEAT PAN
FROM HORIZONTAL PITCH UP ANGLE -DEFORMED SEAT NOT TO EXCEED 35°
HORIZONTAL SECTION A-A FLOOR Figure 3. Maximum Post-test Seat Pan Rotation 4