Table 3 – Coefficients of Restitution Surface Type Coefficient of Restitution Vertical Impact Speed (ft/s) Soft soil or water 0 𝑣𝑣𝑚𝑚𝑚𝑚𝑖𝑖𝑚𝑚𝑐𝑐𝑔𝑔 > 340 Soft soil or water 0.09 − 0.39(𝑆𝑆𝑜𝑜𝑔𝑔10 − 2.301) 340 > 𝑣𝑣𝑚𝑚𝑚𝑚𝑖𝑖𝑚𝑚𝑐𝑐𝑔𝑔 > 200 Soft soil or water 0.2 − 0.0.845(𝑆𝑆𝑜𝑜𝑔𝑔10 − 1) 200 > 𝑣𝑣𝑚𝑚𝑚𝑚𝑖𝑖𝑚𝑚𝑐𝑐𝑔𝑔 > 10 Soft soil or water 0.2 10 > 𝑣𝑣𝑚𝑚𝑚𝑚𝑖𝑖𝑚𝑚𝑐𝑐𝑔𝑔 Hard 0 𝑣𝑣𝑚𝑚𝑚𝑚𝑖𝑖𝑚𝑚𝑐𝑐𝑔𝑔 > 300 Hard 𝑆𝑆𝑜𝑜𝑔𝑔10�300/𝑣𝑣𝑚𝑚𝑚𝑚𝑖𝑖𝑚𝑚𝑐𝑐𝑔𝑔 � 0.5 𝑆𝑆𝑜𝑜𝑔𝑔10(300/40) 300 > 𝑣𝑣𝑚𝑚𝑚𝑚𝑖𝑖𝑚𝑚𝑐𝑐𝑔𝑔 > 40 Hard 0.5 40 > 𝑣𝑣𝑚𝑚𝑚𝑚𝑖𝑖𝑚𝑚𝑐𝑐𝑔𝑔
12.4.2.1 The contact with the Earth’s or waterborne vessels’ surface should account for changes in the rotation rate of the fragment. During initial approach of the fragment, the angular speed can be assumed to be zero, which results in the angle of reflection equal to the angle of incidence. Conservation of momentum should be applied during contact with the surface to determine the post-bounce angular rate. The angular rate can be assumed to remain constant while the fragment is airborne and should be applied on subsequent bounces to compute the next angle of reflection.
12.4.2.2 The elliptical path, formed by the fragment’s trajectory between bounces, should be tracked to identify which body parts are struck both during the ascent and descent to convert to effective casualty area. In the absence of data on the average height of exposed persons, a height of a five feet should be used when accounting for areas where a fragment bounce over a person’s head and poses no hazard. The bouncing phase of the fragment should stop when the maximum rebound height drops below a threshold, such as 0.5 feet.
12.4.3 Slide and Roll Hazard Area.
When the fragment bouncing phase has ended, the motion of the fragment should be continued in the forward direction, accounting for the reduction in horizontal speed due to friction. The radius of the rolling fragment should be used to determine which body part(s) the fragment impacts. Obstacles such as trees, rocks, and similar items can be 67
/2" ·Plyvyood Joists ' Purlins sheath1n ignored if a bound is placed on the maximum distance that the fragment can travel once surface impact occurs. A typical bound is about a couple hundred feet.
12.5 Probability of Casualty Area.
In accordance with § 450.135(b)(4)(i), the vulnerability of people to debris impacts or effects must be represented by an effective casualty area. The hazard is due to fragments that penetrate the roof, causing potential injury to the people on the floor(s) below from the roof hazardous debris and the original fragment itself. The probability of casualty should be evaluated in the form 𝑒𝑒𝑐𝑐𝑚𝑚𝑠𝑠𝑠𝑠𝑚𝑚𝑓𝑓𝑔𝑔𝑔𝑔 = 𝐶𝐶𝐴𝐴/𝐴𝐴𝑟𝑟𝐶𝐶𝐶𝐶𝑟𝑟. The probability of impact is computed separately and is evaluated over the effective roof area. This area should include the projected radius of the fragment if casualty can occur when the fragment clips the edge of the building.
12.6 Potential for Roof Penetration.
Evaluation of the potential for roof penetration should consider the fragment’s weight, projected area, angle of incidence, and impact vertical speed. The horizontal speed component of the velocity can be ignored. The construction of the building’s roof and frame should also be considered such as dimensions, spacing of any joists or girders, and beam section properties. Figure 6 shows the layout of a typical wood roof and different impact configurations.
Figure 6 – Illustration of a Wood Built-Up Roof
12.6.1 Hazardous debris that impacts the floor surface directly under the roof may penetrate the next floor level and cause potential injury to people two levels below the roof, and so on. Hazards tend to diminish the farther down a floor is from the roof. This means that risk values can be reduced by computing it for all floors in a building where people reside. However, it becomes more of a challenge to obtain accurate risk values for the lower floors beyond two or three down. As a tradeoff, risks can be evaluated for just 68
some of the uppermost floors, and then to account for people in lower floors a conservative approach is to move them up to the lowest level that is being considered. It is acceptable to place everyone in the uppermost floor, although excessive risk might result and there might be greater chance that the thresholds are exceeded.
12.6.2 The sheltering model should account for variability of the fragment and building parameters. It can be assumed that a uniform impact probability distribution is applicable for the impact points on a roof. To avoid dealing with the orientation of a person as that person is struck, a conservative approach is to model only vertical head impacts. If extended roof hazardous debris, e.g., a beam, impacts a person, then its orientation should be accounted for when it strikes the head.
12.6.3 Typically, it is not necessary to evaluate individual buildings. Instead, a small number of building classes can be defined to assess the protection afforded to sheltered persons.
Unique buildings, particularly in the immediate launch vicinity, may need to be decomposed into sections corresponding to the representative buildings. If a specific building is not represented by a class, then a separate analysis needs to be performed on it. A representative building can be modeled without any bounds on the roof size. If the resultant effective casualty area is larger than the roof of the actual building it is being applied to, then the area should be cropped to that roof size.
12.6.4 The four roof classifications represented in Table 4 of this AC were analyzed for penetration by six ballistic coefficient classes for the hazardous debris. The hazardous debris were assumed to impact the roofs at terminal velocity and had weights ranging from 0.1 lb. to 10,000 lb. The resulting effective casualty areas for people in the top floor of the structures impacted by inert hazardous debris are shown in Figure 7 through Figure 10. Each figure provides the effective casualty area for a given roof-type as a function of fragment weight in each of the beta classes.
Table 4 – Representative Building Classes Structure Roof Class Building Description Typical Construction Conservative Glass/Floor Area Ratio A Mobile home and trailers; Temporary office trailers Wood studs with plywood used for walls and roof 20 percent B Single residential units of all types, single family dwellings, duplex, apartments, town homes, condos Un-reinforced masonry walls with wood stud roof 30 percent C Commercial buildings less than 15,000 ft2 of all kinds, including retail, offices, restaurants, gas stations, strip malls Metal stud and metal panel walls, steel moment resisting frame, metal panel roof 35 percent D Commercial buildings more than 15,000 ft2 of all kinds, including retail, offices, warehouses, manufacturing, malls Lightly reinforced concrete tilt-up walls with wood or metal decking over steel joists 10 percent
12.6.5 The effective casualty areas in the figures are based on many impact points over a roof for each fragment weight and roof type. In some cases, penetration will not occur every time, because the fragment is stopped by the joist supporting the surface. The average effective casualty area accounts for the contributions of those cases where there is no penetration.
1,000.0
100.0 ¢' rj- 1/) "' ~ "' ~ ni 10.0 ::, 1/) "' " ., "' ~ ., > <(
1.0
0.1 1,000.0
100.0 ¢' ,j- IJ) "' ~ "' ~ 100 ni ::, IJ) "' " ., "' ~ ., > <(
1.0
0.1 Ballis1ic Coefficient (BC) Class 1
(1.8 to 3 psi) does not penetrate.
All other classes penetrate.
- Be Class 2: 3to 10 psi
- Be Class 3: 1010 17.5 psi
- BC Class 4: 17.5 to 30 psi
- BC Class 5: 30 to 55 psi
- BC Class 6: 55 to 69.9 psi Line endings on the left ,_ ___ _,~ --+--- ~~----+ ~,_ _____ +--< within the boundary of the
0.1 1.0 10.0 100.0 Fragment mass - lbs.
Ballistic Coefficient (BC) Class 1
(1.8 to 3 psi) does not penetrate.
All other classes penetrate .
- Be Class 2: 3 to 10 psi
- Be Class 3: 10 to 17.5 psr
- Be Class 4: 17.5 to 30 psr
- Be Class 5: 30 to 55 psr
- Be Class 6: 55 to 100 psi chart indicate th at the fragment class does not penetrate beyond that point in either direction 1,000.0 Line endings on the left t------ -<----t---------t-----------t-----1 within the boundary of the chart indicate that the fragment class does not penetrate beyond that point in either direction
0.1 1.0 10.0 100.0 1,000.0 Fragment mass - lbs 10,000 .0 10,000.0 08/02/2024 AC 450.115-1B Figure 7 – Effective Casualty Areas of Hazardous Debris Hitting a Light Metal Roof (Class A) Figure 8 – Effective Casualty Areas of Hazardous Debris Hitting a Wood Roof (Class B) 71
,000 .0
100.0 =i ci- "' "' ~ "' j;' 10.0 "' :, "' "' 0 ., OJ ~ ., > <(
1.0
0.1
0.1 Ballistic Coefficient (BC) Class 1
(1.8 to 3 ps~ does not penetrate.
All other classes penetrate.
- BC Class 2: 3to 10 psi
- Be Class 4: 17 .5 to 30 psf
- BC Class 5: 30 to 55 psi
- BC Class 6: 55 to 100 psi
- BC Class 3: 10 to 17.5 psi
1.0 10.0 100.0 Fragment mass - lbs.
Line endings on the left within the boundary olthe chart indicate that the fragment class does not penetrate beyond that point in e~her direction 1,000.0 10,000 .0 08/02/2024 AC 450.115-1B Figure 9 – Effective Casualty Areas of Hazardous Debris Hitting a Composite Roof (Class C) 72
,000.0
100.0 <le!
0- "' ' "' ~ "' ~ 10 .0 ni => "' "' u "' Cl ~ "' > <(
1.0
0.1
0.1 Ballistic Coefficient (BC) Classes 1 and 2
(1.8 to 10 psn do not penetrate.
All other classes penetrate.
- BC Class 3: 10 to 17.5psf
- BC Class 4: 17.5 to 30 psi
- BC Class 5: 30 to55 psi
- Be Class 6: 55 to 100 psi
1.0 10.0 100 .0 Fragment mass - lbs Line endings on the left w~hin the boundary of the chart indicate that the hgment class does not penetrate beyond that point in either diredion 1,000.0 10,000.0 08/02/2024 AC 450.115-1B Figure 10 – Effective Casualty Areas of Hazardous Debris Hitting a Concrete Reinforced with Steel Roof (Class D)
12.7 People in Waterborne Vessels (Ships).
In accordance with § 450.135(b)(4)(i), the vulnerability of people to debris impacts or effects from inert hazardous debris to people on ships must be represented by an effective casualty area. Effects from inert hazardous debris impacts in the water near the ships can be ignored. The probability of casualty is 𝑒𝑒𝑐𝑐𝑚𝑚𝑠𝑠𝑠𝑠𝑚𝑚𝑓𝑓𝑔𝑔𝑔𝑔 = 𝐶𝐶𝐴𝐴/𝐴𝐴𝑠𝑠ℎ𝑚𝑚𝑖𝑖, and the probability of impact is computed separately and is evaluated over the ship deck area.
12.7.1 Several sources of casualty should be considered for inert hazardous debris impacts on ships as described in the reference [22] of paragraph 3.4 of this AC. The effective casualty area should account for injuries to people from direct strikes, deck penetration, hull penetration, and onboard fuel explosions. The most severe is a catastrophic event that is defined as one leading to a large number of casualties or a loss of ship. One catastrophic event that should be evaluated is a ship sinking due to hull penetration.
12.7.2 If the ship’s hull is penetrated by hazardous debris and causes significant hull damage resulting in a catastrophe (e.g. sinking), and the estimated time to rescue the ship occupants exceeds the time they would be expected to survive without serious injuries, then the effective casualty area should be set to the maximum possible value, (i.e. to that of the ship area: 𝐶𝐶𝐴𝐴 = 𝐴𝐴𝑠𝑠ℎ𝑚𝑚𝑖𝑖). An inert fragment will penetrate the hull if it has sufficient impact kinetic energy and mass. If the speed of a ship is significant relative to 73
the impact speed of a fragment, the impact velocity of the fragment relative to the ship may need to account for the ships speed.
12.7.3 Table 5 of this AC provides thresholds for hull damage based on the size of the ship.
The effective casualty area should be set to zero if both criteria listed in the table are not satisfied for a given ship size, and then other sources of casualty should be evaluated.
Table 5 – Threshold Values for Significant Hull Damage Ship Category Penetration Criteria Length (ft) Ship Types Deck/hull Material Minimum Mass (lbs) Minimum Kinetic Energy (ft lbf) < 25 Small fishing vessels and pleasure craft One plywood layer: 0.75 inch 0.6 25 25-50 Small to medium size fishing vessels and pleasure craft Two plywood layers:
0.5 and 0.75 inches
0.7 115 50-100 Medium sized fishing vessels and pleasure craft, tug boats Two plywood layers
0.75 inch each
1.0 205 100-200 Large fishing vessels, pleasure craft, and coast guard patrol ships Two steel layers:
0.1 and 0.2 inches 35 40,000 200-295 Large fishing vessels, pleasure craft, and coast guard patrol ships Two steel layers
0.2 and 0.3 inches 115 71,000 > 295 Container ships, tankers, other cargo ships, pleasure cruise ships, military ships Two steel layers
0.2 and 0.4 inches 6,300 1,250,000
12.7.4 Another catastrophic event is an explosion/fire from stored fuel being ignited by tank penetration or a collapsing deck. Ships tend to store fuel below the cabin or deck. A determination should be made of the total area 𝐴𝐴𝑟𝑟𝑠𝑠𝑟𝑟𝑓𝑓 that could be penetrated leading to ignition and subsequent explosion of the fuel. If the fuel is ignited, then the effective casualty area should be set to the fuel storage area: 𝐶𝐶𝐴𝐴𝑟𝑟𝑠𝑠𝑟𝑟𝑓𝑓 = 𝐴𝐴𝑟𝑟𝑠𝑠𝑟𝑟𝑓𝑓.
12.7.5 An inert fragment will penetrate the deck if it has sufficient kinetic energy and weight.
12.7.6 Table 6 of this AC provides thresholds for deck damage based on the size of the ship.
The effective casualty area should be set to zero if both criteria are not satisfied for a given ship size.
Table 6 – Threshold Values for Ship Cabin and Deck Penetration Ship Category Penetration Criteria Length (ft) Roof Material Minimum Mass (lbs) Minimum Kinetic Energy (ft lbf) < 25 No roof assumed n/a 11 25-50 1/2-inch plywood 0.055 23 50-100 3/4-inch plywood 0.137 75 100-200 0.10-inch steel 1.2 1,300 200-295 0.20-inch steel 4.4 7,800 > 295 0.3125-inch steel 10.0 16,000
12.7.7 The analysis should assume that the location of people on the ship or below deck is not coincident with that of the fuel storage area. The effective casualty area that accounts for both fuel explosion and casualty hazardous debris should be the sum 𝐶𝐶𝐴𝐴 = 𝐶𝐶𝐴𝐴𝑑𝑑𝑟𝑟𝑠𝑠𝑟𝑟𝑚𝑚𝑠𝑠 + 𝐶𝐶𝐴𝐴𝑟𝑟𝑠𝑠𝑟𝑟𝑓𝑓. Replace the sum with the ship area if the latter sum is smaller.
12.7.8 For unsheltered people, 𝐶𝐶𝐴𝐴𝑑𝑑𝑟𝑟𝑠𝑠𝑟𝑟𝑚𝑚𝑠𝑠 is evaluated in the same method used in paragraph
12.1.1 of this AC. If the deck is not penetrated, then 𝐶𝐶𝐴𝐴𝑑𝑑𝑟𝑟𝑠𝑠𝑟𝑟𝑚𝑚𝑠𝑠 includes the contributions from a direct hit, as well as bounce and roll. If the fragment penetrates the deck, then 𝐶𝐶𝐴𝐴𝑑𝑑𝑟𝑟𝑠𝑠𝑟𝑟𝑚𝑚𝑠𝑠 only accounts for the direct hit and ignores the bounce and roll. For people below deck, Table 6 may be applied to determine if the hazard exists. Since ship decks tend to be strong material, the effective casualty area should be set to three times the projected hazardous area of the fragment 𝐶𝐶𝐴𝐴𝑑𝑑𝑟𝑟𝑠𝑠𝑟𝑟𝑚𝑚𝑠𝑠 = 3𝐴𝐴𝑟𝑟𝑟𝑟𝑚𝑚𝑓𝑓𝑚𝑚𝑟𝑟𝑚𝑚𝑔𝑔 to account for secondary hazardous debris if deck penetration occurs.
12.8 People in Aircraft.
In accordance with § 450.135(b)(4)(i), the vulnerability of people to debris impacts or effects to people in aircraft must be represented by an effective casualty area. An accurate method for aircraft risk examines the aircraft passing through the 3-dimensional hazardous debris cloud. Since the aircraft is in motion, there are a series of casualty areas where each is active for a short period of time, typically a few seconds or less. Each casualty area corresponds to that of the lateral cross-section of the volume that the aircraft sweeps out during the time the aircraft passes through the debris cloud.
This area is a projected area, relative to the direction of travel of the aircraft. Chapter 10 75
of reference [1] in paragraph 3.4 of this AC provides additional discussion of the calculation of aircraft risk.
12.8.1 The application of vulnerability that leads from a casualty area to an “effective” casualty area comes from both the aircraft and the people on board. The term “aircraft vulnerability” refers to the combination of the two sources. The aircraft may be modeled as a rectangular box with top area 𝐴𝐴𝑔𝑔𝐶𝐶𝑖𝑖, front area 𝐴𝐴𝑟𝑟𝑟𝑟𝐶𝐶𝑚𝑚𝑔𝑔 , and a side area 𝐴𝐴𝑠𝑠𝑚𝑚𝑑𝑑𝑟𝑟. The side area can be ignored because almost all fragments are likely to strike the front or top of the aircraft, and only graze the aircraft sides.
12.8.2 Applying aircraft vulnerability, the casualty area is reduced to the effective casualty area, and the corresponding volume swept out leads to a projected vulnerability volume.
When the aircraft is moving through a hazardous debris cloud, the aircraft consequence probabilities should be summed over a series of snapshot times when both the aircraft and hazardous debris cloud are frozen. The projected vulnerable volume is the space that the aircraft’s projected vulnerable area sweeps out during the time interval 𝛥𝛥𝑆𝑆 between snapshot times, 𝛥𝛥𝑐𝑐𝑆𝑆𝛥𝛥𝑖𝑖𝑟𝑟𝐶𝐶𝑗𝑗𝑟𝑟𝑐𝑐𝑔𝑔𝑟𝑟𝑑𝑑 = 𝛥𝛥𝑐𝑐𝑆𝑆𝐴𝐴𝑖𝑖𝑟𝑟𝐶𝐶𝑗𝑗𝑟𝑟𝑐𝑐𝑔𝑔𝑟𝑟𝑑𝑑 × 𝑣𝑣𝑟𝑟𝑟𝑟𝑓𝑓 × 𝛥𝛥𝑆𝑆 𝑣𝑣𝑟𝑟𝑟𝑟𝑓𝑓 is the relative speed (magnitude of the velocity vector of impact) between the aircraft and the hazardous debris cloud:
𝑣𝑣𝑟𝑟𝑟𝑟𝑓𝑓 = �𝑣𝑣 ⃗𝑚𝑚𝑚𝑚𝑟𝑟𝑐𝑐𝑟𝑟𝑚𝑚𝑟𝑟𝑔𝑔 − 𝑣𝑣 ⃗𝑑𝑑𝑟𝑟𝑠𝑠𝑟𝑟𝑚𝑚𝑠𝑠�.
The probability of consequence is the product sum 𝑁𝑁𝑡𝑡𝑡𝑡𝑡𝑡𝑐𝑐𝑐𝑐 𝑒𝑒𝑐𝑐𝐶𝐶𝑚𝑚𝑠𝑠𝑟𝑟𝑐𝑐𝑠𝑠𝑟𝑟𝑚𝑚𝑐𝑐𝑟𝑟 = � 𝑒𝑒𝑔𝑔𝐶𝐶𝑓𝑓𝑠𝑠𝑚𝑚𝑟𝑟�𝑆𝑆𝑗𝑗� × 𝛥𝛥𝑐𝑐𝑆𝑆𝛥𝛥𝑖𝑖𝑟𝑟𝐶𝐶𝑗𝑗𝑟𝑟𝑐𝑐𝑔𝑔𝑟𝑟𝑑𝑑�𝑆𝑆𝑗𝑗� 𝑗𝑗=1 where 𝑒𝑒𝑔𝑔𝐶𝐶𝑓𝑓𝑠𝑠𝑚𝑚𝑟𝑟 is the probability of finding a fragment in the volume.
12.8.3 The vulnerable area of an aircraft depends on the fragment’s mass, size, and shape.
Models to compute 𝛥𝛥𝑐𝑐𝑆𝑆𝐴𝐴𝑖𝑖𝑟𝑟𝐶𝐶𝑗𝑗𝑟𝑟𝑐𝑐𝑔𝑔𝑟𝑟𝑑𝑑 for aircraft are called the Probabilistic Aircraft Vulnerability Models (PAVM). A full discussion and details of the modeling process is given in reference [24] of paragraph 3.4 of this AC. The models consider potential hazardous debris damage and penetration of components of the aircraft, and apply human vulnerability models to evaluate serious injury for passengers. Rather than treat each fragment type individually, a conservative approach may be taken to model the hazardous debris fragments as steel cubes.
12.8.4 Above the maximum mass for which a PAVM is valid, the full size of the aircraft is used:
𝑐𝑐𝑓𝑓𝐶𝐶𝑠𝑠𝑑𝑑 𝑐𝑐𝑓𝑓𝐶𝐶𝑠𝑠𝑑𝑑 𝛥𝛥𝑐𝑐𝑆𝑆𝛥𝛥𝑖𝑖𝑟𝑟𝐶𝐶𝑗𝑗𝑟𝑟𝑐𝑐𝑔𝑔𝑟𝑟𝑑𝑑 = (𝐴𝐴𝑔𝑔𝐶𝐶𝑖𝑖 × 𝑣𝑣𝑔𝑔𝑟𝑟𝑟𝑟𝑔𝑔𝑚𝑚𝑐𝑐𝑚𝑚𝑓𝑓 + 𝐴𝐴𝑟𝑟𝑟𝑟𝐶𝐶𝑚𝑚𝑔𝑔 × (𝑣𝑣𝑚𝑚𝑚𝑚𝑟𝑟𝑐𝑐𝑟𝑟𝑚𝑚𝑟𝑟𝑔𝑔 + 𝑣𝑣ℎ𝐶𝐶𝑟𝑟𝑚𝑚𝑧𝑧𝐶𝐶𝑚𝑚𝑔𝑔𝑚𝑚𝑓𝑓)) × 𝛥𝛥𝑆𝑆 The vertical cloud speed may correspond to a cloud that is either ascending or descending. For aircraft for which no PAVM applies, all fragments above one gram should be considered hazardous to the entire aircraft. PAVM modeling was not done for masses over 300 grams since the analysis becomes very complicated due to multiple 76
.._, ctl Q) 4:
"C .El (.J Q) ·a .... a..
Q) :0 ctl ai C :i > 10000 1000 100 10 ------·--------- -- -- -·- ------------
- BJ Casualty
- CT Cas ualty
- - - Jumbo CT Cas ualty -------,----------------------,-----------,----_______ , ___ _ -------,----------------------,-----------,----_______ , ___ _ '' ''' • L .I. i ..>.L •• - • - • -'• - • -
• ~ •1• T -,-,- • • • • • • -,• • • • ·r·,-y;-,-------,--- ·r -,- ,-.·r-··----._---
- ~ •1• T -,-r •••• - • -,- - • -
• L .1. i .;.L. •••••• -'• •••
I I I I I I
• ~ ·1· T -.-,- • • • - • - -,- • - • -- ---,- -,- ----,--- y ·-,--,- ,-,-y-,-------y- ---,--- 1 I I I I I I I I I ----►--•--•--•-◄---•---------•----•--- ' I I I I I I I I I
- - - -~ - -:--:- -:-~ -~: ~- - - - - -~ _..~-- -
I I I I I I ____ ,_ __ i __ , __ ,_
••--r---T--1- ---------,------- --- -,--- - ----,--- ----,--- ----- ---------,--,- ----,--- ,..=.=----,---_-_-__ -_---•~ ~ ~ ~ ~~ ~~ g ~ ~ ~l~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~ ~ ~ -------,----------------------,---- -------,--,- -----------,----------,---- - - , - - .. -.- -,- ~, -,- - - - - - - , - - - -,- - -_______ , ___ _
•• J •• L.L->.LJ.1 ••••••• .; •••• L ••
I I I I I I I I I
- - ., - - ,- -,- -,- ~., -1- - - - - - - ., - - - -,- - - - -,- -,- T -,- - - - - - - - - - -,- - -
I I I I I I I --◄ -->-- .. ◄-► ◄-•-- -----◄---- .. -- --◄ -->-- .. ◄-►◄-•-------◄-------- ' I I I I I I I ---,- ---,- ---,- ---,- 1 ~-~-~~~~~~--~~~~~~~~-~-~~~~~~--~~-~~~~
0.1 10 Fragment Mass (g) 100 1000 08/02/2024 AC 450.115-1B aircraft components that can be damaged during the same event. Instead, the analysis should assume that any impact by a fragment with a mass over 300 grams is casualty producing.
12.8.5 Below 300 grams, PAVM models have been developed for several aircraft types.
Figure 11 of this AC, presents curves of 𝛥𝛥𝑐𝑐𝑆𝑆𝐴𝐴𝑖𝑖𝑟𝑟𝐶𝐶𝑗𝑗𝑟𝑟𝑐𝑐𝑔𝑔𝑟𝑟𝑑𝑑 for three classes of aircraft.
These curves assume terminal velocity for the hazardous debris cloud fragments moving only in a vertical direction and aircraft flying only in the horizontal direction.
For all other aircraft, all debris larger than one gram should be considered catastrophic.
The reference [22] of paragraph 3.4 of this AC provides additional details on the proper use of these aircraft vulnerability models.
Figure 11 – Sample Aircraft Vulnerable Projected Areas
12.9 Explosive Hazardous Debris.
In accordance with § 450.135(b)(1), consequences must be evaluated for all types of hazardous debris. This section discusses the hazard cases where explosive hazardous debris consequences arise, how to model explosions for risk analysis, and provides guidelines for evaluating such consequences.
• Explosive risk must be computed for unsheltered people, people in buildings, and people on or below deck on waterborne vessels. Explosive impacts on aircraft may be ignored, although treating the propellants as inert must be evaluated.
• Impacting SRMs, liquid fueled rockets, intact tanks, and major segments of SRMs should be evaluated to determine whether they are expected to explode on impact.
The explosion will cause a blast overpressure wave that may reach several thousand feet for large propellant weights. A general discussion of yield models exists in AC 450.137-1, Distant Focusing Overpressure (DFO) Risk Analysis.
12.10 Yield Models.
12.10.1 Characterizing the hazard from a blast wave that results from the impact of an explosive propellant fragment, requires the TNT equivalent yield of the explosive. Yield Y is the TNT equivalency of an explosive propellant weight w.
12.10.2 These parameters are related through a “TNT equivalency factor” 𝑌𝑌 = 𝐹𝐹𝑇𝑇𝑁𝑁𝑇𝑇𝑤𝑤.
In general, the factor FTNT may depend on propellant type, the type of surface that the propellant strikes, and the impact speed.
12.10.3 An accurate means to evaluate the consequences of an overpressure wave on people is to compute the peak overpressure 𝑃𝑃(𝑑𝑑) and impulse 𝐼𝐼(𝑑𝑑) of the blast overpressure wave at a distance d from the impact point.
12.10.4 To convert yield into these parameters, it is convenient to use the scaled distance 𝑑𝑑𝑠𝑠𝑐𝑐𝑚𝑚𝑓𝑓𝑟𝑟𝑑𝑑 = 𝑑𝑑/𝑌𝑌1/3 .
12.10.5 The peak overpressure as a function of scaled distance may be obtained from Figure 12, and impulse as a function of scaled distance, in units of ft/lb1/3, may be obtained from Figure 13 of this AC. The reference listed as [14] of paragraph 3.4 of this AC provides further information.
12.10.6 These curves have been in use for decades by the Federal Ranges. A publication search may uncover various versions of updated curves that have been published since then, and with proper justification can be used as replacements to gain more accuracy.
1.0E-03
1.0E-02
1.0E-01
1.0E+00
1.0E+01
1.0E+02
1.0E+03
1.0E+04
1.70E-01 7.10E-01 2.97E+00 1.24E+01 5.18E+01 2.16E+02 9.03E+02 3.77E+03 Pressure (psi) Scaled Distance Figure 12 – Peak Overpressure vs. Scaled Distance from Blast Waves 78