af3 advanced forest fire...

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AF3- Advanced Forest Fire Fighting Grant Agreement no: 607276

AF3

Advanced Forest Fire Fighting

D7.2.1 – Helicopter AAFF Survey report

PREPARED BY

Shlomo Alkaher Royi Bagg [Name 3] [Name 4]

Elbit Elbit [Beneficiary] [Beneficiary]

DISSEMINATION LEVEL

PU Public

PP Restricted to other program participants (including the Commission Services)

RE Restricted to a group specified by the consortium (including the Commission Services)

CO Confidential, only for members of the consortium (including the Commission Services)

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REVISIONS LOG

REV CHANGE REFERENCE DATE CHANGE DESCRIPTION PREPARED

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ABBREVIATIONS AND ACRONYMS

ABBREVIATION / ACRONYM

DESCRIPTION

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TABLE OF CONTENTS

TABLE OF FIGURES ................................................................................................................................................. 55

TABLE OF TABLES ................................................................................................................................................... 55

1. PURPOSE AND SCOPE ..................................................................................................................................... 66

2. REFERENCED DOCUMENTS ............................................................................................................................. 66

2.1 CONTRACTUAL DOCUMENTS ..................................................................................................................................... 66 2.2 APPLICABLE DOCUMENTS ......................................................................................................................................... 66

3. REQUIREMENTS FROM HELICOPTER INTEGRATED WITH AAFF ......................................................................... 77

3.1 OBJECTIVES .......................................................................................................................................................... 77 3.2 COVERAGE LEVEL ................................................................................................................................................... 77 3.3 MINIMUM LOAD ................................................................................................................................................... 77 3.4 SPEED .................................................................................................................................................................. 77 3.5 HELICOPTER TYPE .................................................................................................................................................. 88 3.6 INTEGRATION WITH AAFF COMPUTERIZED DELIVERY SYSTEM ......................................................................................... 88 3.7 DISPENSER ........................................................................................................................................................... 88 3.8 DISPENSER SAFETY REQUIREMENTS ........................................................................................................................... 88

4. COMPUTERIZED DELIVERY SYSTEM ................................................................................................................. 99

4.1 DROP COMPUTER .................................................................................................................................................. 99 4.2 INS/GPS ............................................................................................................................................................. 99 4.3 GPS ANTENNA ...................................................................................................................................................... 99 4.4 8” TOUCH SCREEN ................................................................................................................................................. 99

5. MEDIUM/LARGE SIZE HELICOPTER SURVEY FOR AAFF ................................................................................. 1111

5.1 GENERAL .......................................................................................................................................................... 1111 5.2 HELICOPTER CHARACTERISTICS: ............................................................................................................................. 1111 5.3 HELICOPTER FIREFIGHTING CONFIGURATION ............................................................................................................ 1212 5.4 EVALUATION CATEGORIES CRITERIA AND WEIGHTING (IN PERCENTS) ............................................................................ 1414 5.5 HELICOPTERS EVALUATION .................................................................................................................................. 1515 5.6 EVALUATION SUMMARY AND RECOMMENDATIONS ................................................................................................... 1717

ANNEX A – EXAMPLES OF HELICOPTER DISPENSER TANKS COMPATIBILITY ......................................................... 1919

APPENDIX B ‐ COVER LEVEL OF WATER FOR SUPPRESSION OF WILD FIRES .......................................................... 2323

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TABLE OF FIGURES Figure 1: System architecture Diagram ....................................................................................................... 1010 Figure 2: Example of screen location during drop run in CL-215 ................................................................ 1010 Figure 3 Images of Blackhawk U-60 named as S-70 "FireHawk" ............................................................... 1212 Figure 4 Images of S-64 “Sky Crane” .......................................................................................................... 1313 Figure 5 Images of S-61 “Sea King” ............................................................................................................ 1313 Figure 6 Images of Ka-32 with a sling bucket (left) and hard mounted tank (right) .................................... 1414

TABLE OF TABLES Table 1 – Helicopter characteristics ............................................................................................................ 1111 Table 2 – Helicopters Evaluation ................................................................................................................. 1717

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1. PURPOSE AND SCOPE

One of the main objectives of the AF3 program is to adapt and integrate the new AAFF system with the AF3 systems and fire fighting missions: forest and bush, forest infrastructure and wildland-urban interface fires.

This will be done by integrating the AAFF system on the selected operated aerial platforms in Europe with pellets dispensing capability, day and night targeting, post mission debrief tools and logistics accessories.

The integrated systems will serve as prototypes of the AAFF system for testing and evaluation (WP8) of the new fire fighting capabilities.

In this document we present a survey of potential helicopters (as one type of aerial platform, in addition to fixed wing platforms) and selection of one specific helicopter as a technology demonstrator for the AF3 program.

2. REFERENCED DOCUMENTS

2.1 CONTRACTUAL DOCUMENTS

2.2 APPLICABLE DOCUMENTS

2.2.1 Cover level of water for suppression of wild fires, derived from "The effectiveness and efficiency of aerial firefighting in Australia part 1 (M.Plucinski, J.Gould, G. McCarthy, J. Hollis - WIT.7541.001.0200_R" attached here as Appendix 1

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3. REQUIREMENTS FROM HELICOPTER INTEGRATED WITH AAFF

3.1 OBJECTIVES

The following paragraphs define the requirements from an helicopter that will be integrated with the AAFF system and provide the required improved firefighting performance.

The Main goal of the Helicopter is to enable the load and drop of pellets on the target (fire center or fire propagation line) using calculated ballistic trajectory, while flying straight and level and from high altitude (500-2000 ft) relative to the common practice without AAFF.

3.2 COVERAGE LEVEL

3.2.1 The current acceptable requirements for coverage levels with existing conventional aerial firefighting methods are presented in Applicable document 2.2.1 and summerized in Appendix 1. These coverage levels discuss conventional drop of water or retardant coverage level. Since at this stage we do not have a better criteria to be used with the drop of pellets with the new AAFF technology, this criteia will be used for the calculations hereinafter. The criteria will be evaluated later on in the program when dropped on real fire.

3.3 MINIMUM LOAD

3.3.1 The minimum load of pellets required to perform fire extinguishing effectively is 3 tons.

3.3.2 This amount is derived from the required coverage level needed on the ground according to Applicable document 2.2.1 as explained in the following.

3.3.3 The speed of the helicopter in firefighting mission can be from hovering to 100 knots, and dropping height with the AAFF system will be above 500 ft. At a height of 500 ft, the width spread of pellets dropped on the ground (based on empiric tests) is about 20 meters and the length covered in 1 second of flight at 100 knots is 50 meters. The total area covered in these conditions is therefore 1000 square meters per second, and if we want to achieve maximum coverage level of 8 GPC which equal to 3 Liters/Square Meter than the Helicopter is required to drop 3 tons in one second.

3.3.4 Since the drop rate depends on the implementation of the dispenser and in order to enable a simple and efficient design of the dispenser, it was determined that the nominal design goal for the dropping rate will be 1.5 tons per second rather than 3 tons per second. The coverage level will be maintained as above by flying the Helicopter at 50 knots (rather than 100 knots) covering a length of 25 meters per second.

3.3.5 We concluded that 50 meters would be the minimum length requirement of fire extinguishing, thus we derived the Minimum Load as 3 tons of Pellets.

3.4 SPEED

3.4.1 The speed of the Helicopter in Firefighting mode should be between 20 knots to 100 knots, although this action can be performed by hovering. This requirement is derived from actual helicopter capabilities and from required coverage levels. According to the required coverage levels in specific fires, higher coverage levels will be achieved by lower flight speeds while increasing the speed will result in lower coverage levels.

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3.5 HELICOPTER TYPE

3.5.1 The minimum load requirement in paragrpah 3.3 3.4 above requires Medium to Heavy Helicopters or Cargo Helicopters.

3.6 INTEGRATION WITH AAFF COMPUTERIZED DELIVERY SYSTEM

3.6.1 The Computerized Delivery System that will be used on the AAFF Helicopter is based on commercial rugged laptop, INS/GPS Sensor, and additional Display.

3.6.2 The Delivery System is an ADD ON System, and does not require any permanent installation in the Helicopter. This fact eliminate the need for special flight certifications – no structural or other changes are made in or on the Helicopter.

3.7 DISPENSER

3.7.1 In order to drop pellets from the Helicopter a Dispenser is required to enable to load and to drop the pellets in certain aerial position defined by the Computerized Delivery System.

3.7.2 The Dispenser is required to be ADD ON in order to enable the use of a General Cargo Helicopter without making any structural changes to the Helicopter.

3.7.3 In the case of a hard mounted dispenser, the installation of the Dispenser on the Helicopter should take few hours only, using general purpose tools.

3.7.4 This will enable to use the Helicopter in time of emergency – Fire Season, and return it back to other missions after the firefighting mission, by disassembeling the Dispenser from the Helicopter.

3.7.5 The Dispenser can be installed on the Helicopter prior to its mission or carried during the mission as a Slung System, provided that it is aerodynamically stabilized and it is not spining or swinging while flying to target.

3.7.6 The dispensing system including both the dispenser and the delivery computer, should enable the helicopter and its operators to achive the required accuracy and coverage levels.

3.7.7 Dual Use

3.7.7.1 It is prefered that the Dispenser will be Dual Use to Enable either water/retardant drop or pellets drop.

3.7.7.2 Water could be pumped in when hovering over water source using hovering pump.

3.7.8 Dropping Doors

3.7.8.1 The pellets are dropped on electric command via doors that open gravitationaly and enable free gravitational fall of the pellets.

3.7.8.2 In case of of hard mounted dispenser the doors should be closed after all pellets are dropped.

3.8 DISPENSER SAFETY REQUIREMENTS

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3.8.1 Hard Mounted Dispenser

3.8.1.1 The Pilot will be able to drop all pellets in case of emergency.

3.8.1.2 The Pilot will be able to land with the dispenser installed on the Helicopter with open doors.

3.8.2 Dispenser carried on Cargo Hook sling system

3.8.2.1 The Pilot will be able to drop all pellets in case of emergency.

3.8.2.2 The Pilot will be able to jettison the entire Dispenser in case of emergency (e.g. Crash Landing)

4. COMPUTERIZED DELIVERY SYSTEM The AAFF Delivery system consists of the following components:

4.1 DROP COMPUTER Panasonic Toughbook CF-52, Ruggedized PC The drop computer is hand held by the third crew member sitting on the jump seat. When not in use it can be easily located behind the left pilot, there is plenty of empty space there.

4.2 INS/GPS Microstrain GX3-45 The GX3-45 will be attached to the cockpit floor. A USB extension cord might be needed to connect the GX3-45 to the drop computer.

4.3 GPS ANTENNA The GPS antenna will be attached to the glare shield.

4.4 8” TOUCH SCREEN Lilliput 8” TFT LCD VGA Monitor w/ Touch screen, Model 813AHT The touch screen will be located on the glare.

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Figure 1: System architecture Diagram

Figure 2: Example of screen location during drop run in CL-215

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5. MEDIUM/LARGE SIZE HELICOPTER SURVEY FOR AAFF

5.1 GENERAL The evaluation regards to the following types of Cargo/Firefighting helicopters which are operational across the world in the field of firefighting and since they are able to meet the requirements of paragraph 3 3 above:

Blackhawk U-60 S-64 "Skycrane" S-61 "Sea King" Kamov KA-32

The objective of this survey is to predict the compatibility of the platforms above in terms of: a. Integration with the existing AAFF system components (Sensors, HMI and Mission

computer). b. Enable to complete the drop accuracy tests during the R&D phase. c. Maintaining high level safety standards for people and property. d. Number of operational platforms and past firefighting experience.

5.2 HELICOPTER CHARACTERISTICS:

Table 1 – Helicopter characteristics

Empty Weight (lbs.)

Total Payload(lbs.)

Crew Passengers

(without crew)

Water tank capacity (Gal)

Range (NM)

Endurance

(Hrs.)

Blackhawk U-60 13000 9000 2 18 1000 250 2

S-64 Erickson SkyCrane

19234 20000 3 2 2650 230 2.5

S-61 SeaKing

12336 8900 2 30 1000 350 4

14500

11000 (on external sling)

8700 (internal)

2 13 830/1215 400 4

KA-32 14330 8818 2-3 16 650 1300

(on external sling) 530

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5.3 HELICOPTER FIREFIGHTING CONFIGURATION The most common configurations for helicopter aerial firefighting are:

a. External bucket (Cargo hook mounted) b. Internal tank c. External tank (Belly tank)

It was decided not to include the external bucket solution in the survey due to the following reasons:

Difficulties of ballistic computations (required to enable effective high altitude drops) related to a sling bucket which spins, swings or rolls during flight and maneuvering

Pellets flow control as required for uniform and effective coverage is not possible. Pellets loading is inefficient (existing buckets are filled by immersion which cannot

be done with pellets).

However, since an external sling carried bucket can be carried by various helicopters without any modifications, which can be a major advantage, Elbit is examining the option to develop a new sling dispenser which will be aerodynamically stabilized to prevent the effects above while flying to target, and enable quick loading of pellets, pellets flow control and to comply with the AAFF requirements (see annex A7). The advantage will be that a single dispenser design may be carried by any Helicopter using cargo hook, limited only by its maximal takeoff weight. Both internal and external tank systems were explored during the survey. These systems are proven and operational as firefighting configurations for helicopters and were investigated under the focus of minimum modifications to existing systems. We have selected Medium and Large Size Helicopters for the survey, since we believe that the minimum effective weight of pellets to be dropped is 3,000 Kg. (3000 liters of water or retardant). Below this quantity, the effectiveness on fire will not be sufficient, since we want to achieve a coverage level of 3 liters per 1 square meter which is equivalent to the highest coverage level today for wild forest fires – 8 gallons for 100 square feet.

Figure 3 Images of Blackhawk U-60 named as S-70 "FireHawk"

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Figure 4 Images of S-64 “Sky Crane”

Figure 5 Images of S-61 “Sea King”

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5.4 EVALUATION CRITERIA AND WEIGHTING (IN PERCENTS) The following criteria were considered during the evaluation, with each criterion given a respective weight as follows:

a. Global market firefighting experience, number of operational platforms and seasonal firefighting operation extent. (20%)

b. HMI & Experimental requirements: i. Cockpit layout: Jump-seat location for 3rd crewmember (system operator).

(8%) ii. Cockpit system architecture: Screen location, Mission computer location.

(12%) iii. Target sighting: Maximum target visibility time during the drop leg

(monitoring, safety and debrief purposes). (15%) iv. Ground testing capability: System shall have all functions available for

ground tests prior to flight testing. (Mass pellets flow and timing tests prior to the flight tests). (10%)

c. Engineering requirements: i. Currents system compatibility for pellets dispensing: Internal/External tank

architecture for maximum mass flow and fast pellet loading capability. (15%) ii. Minimum modifications from current platform operational water dispensing

system. (20%)

Figure 6 Images of Ka-32 with a sling bucket (left) and hard mounted tank (right)

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5.5 HELICOPTERS EVALUATION Following are the evaluations of compatibility and scoring of the potential Helicopters for each of the above criteria:

a. Experience i. S-70 is Rare in civilian market, operated by 1 company for firefighting (LA

county 3 FireHawks) (40%) Widely in use in U.S. Army and national guard

ii. S-64 Widely common and operated for firefighting in the US civil market. (About 15 helicopters are used for firefighting in the US). Variable amount of platforms are operated by annual contracts in Australia, Canada and Europe. (95%)

iii. S-61: Widely common and operated for firefighting in the US civil market for. (About 12). (85%)

iv. KA32: Common in Greece (6), Spain (9) and South Korea (30) (80%)

b. HMI & Experimental v. Cockpit layout

1. S-70 – moderate, system operator seats in row 1, good crew communication – no target field of view. (60%)

2. S-64 – moderate, system operator seating in observer point without long distance target visibility. (70%)

3. S-61 - good, system operator in the jump seat, good target view and crew communication. (85%)

4. KA-32: moderate, system operator seat behind, good target view and crew communication (60%)

vi. System architecture

1. S-70 - moderate, legible FOV interference for pilot. (70%) 2. S-64 - good, minor FOV interference for pilot. (90%) 3. S-61 - good, minor FOV interference for pilot. (90%) 4. KA-32 - good, minor FOV interference for pilot. (90%)

vii. Target and sighting

1. S-70 – moderate from the cockpit and poor from system operator’s position. (40%)

2. S-64 – good from the cockpit (bobble window), moderate from system operator’s position (80%)

3. S-61 - good from the cockpit (bubble window), good from system operator position (jump seat). (90%)

4. KA-32 – good from the cockpit (bubble window), (?) from system operator’s position (80%)

viii. Ground testing

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1. S-70 – poor, utility hydraulic is not available from helicopter, electricity available. (30%)

2. S-64 - good, utility hydraulic is available from helicopter, electricity available, system can be tested while mounted on helicopter. (95%)

3. S-61 – good, utility hydraulic is available from helicopter, electricity available. (85%)

4. KA-32 – moderate with Bambi Bucket. Can be improved with stabilized dispenser (80%).

c. Engineering requirements (See images in annex 1) ix. System compatibility

1. S-70: poor, no external pellets loading solution (side mounted tanks are not an approved configuration), narrow doors are not suitable for pellet dispensing. (20%)

2. S-64: poor, tank needs to be disassembled for pellets loading; high friction with tank interior will affect flow (40%)

3. S-61: moderate, good door size for pellets flow, solution for pellets loading is required (80%)

4. KA-32 – poor – current solution –Simplex Belly Tank cannot be modified and alternate tank for pellets is not applicable for this Helicopter, since it cannot take off with fully loaded Belly tank (about 4 tons gross weight), but can carry it only after take-off and pull it up using cargo hook. A solution that is independent of the helicopter must be developed in order to carry it on Cargo hook, but accuracy is compensated (40%)

x. Minimum modification to Helicopter

1. S-70: poor, side mounted tanks are required (20%) 2. S-64: moderate, external loading doors should be added + new tank

interior design for friction reduction to enable the required pellets drop rate (50%)

3. S-61: good, new side mounted tank with external loading doors should be added. (90%)

4. KA-32 – good, minimum modification to the helicopter (95%)

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5.6 EVALUATION SUMMARY AND RECOMMENDATIONS

5.6.1 Evaluation results summary

The following table summarizes the evaluation results of the candidate helicopters.

Table 2 – Helicopters Evaluation

Category Weight S-70 S-64 S-61 KA-32*

Experience 20% 40 95 85 80

Cockpit layout 8% 60 70 85 60

System architecture 12% 70 90 90 90

Target sighting 15% 40 80 90 80

Ground testing 10% 30 95 85 80

System compatibility 15% 20 40 80 40

Minimum modification 20% 20 50 90 95

Weighted Total 37.2 72.9 86.6 76.6

5.6.2 Recommendations

1) The S-61 Helicopter is selected as the leading helicopter with maximal compatibility and minimum risk for adapting the AAFF Technology.

2) It is also recommended to examine the option to develop a dedicated AAFF sling carried dispenser, such as described in Annex A7, which will provide the capability to use the AAFF effectively and easily with any of the above helicopters or any other helicopter limited only by its maximal takeoff weight.

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*Note: The KA-32 can carry up to 5000 liters with an external sling bucket, but as described in para. 5.3 5.3 above it was decided not to consider the sling bucket method, and since the KA-32 external tank capacity is limited to 2500 liters, which is less than the minimum load requirement of 3000 liters in Para. 3.3 3.3, it cannot be considered as the selected helicopter. Moreover, its maintenance policy requires engine maintenance and overhaul per takeoff and landing cycles (as opposed to engine operation cycles in western helicopters), which can be found non cost-effective during firefighting operations which require frequent landing and take-off cycles for reloading pellets. However, we decided to leave it in the evaluation for farther discussion.

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ANNEX A – EXAMPLES OF HELICOPTER DISPENSER TANKS COMPATIBILITY

A1. C-64 Tank – Outside view, Tank have to be disassembled in order to load the

pellets

A2. C-64 Tank – Inner view, door module: Tank interior design will affect pellet flow due high friction with inner beams and operators.

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A3. Extensive tests done on Air tractor AT802 (with door mechanism similar to the S-64 tank) revealed that narrow doors with complex door opening mechanism prevent the pellets from flowing at the desired rate.

A4. S-61 Belly inner tank – Tank has to be disassembled in order to load the pellets

A5. S-61 External tank (Isolair) – Adding side modules will enable external pellets loading

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A6. S-70 tank – Pellets loading is impossible without significant modifications of the existing tank (external airframe modification)

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A7. Option for an Active Stabilized Sling Dispenser

Elbit is examining the option to develop a new cargo hook sling carried dispenser which will be designed for quick loading of pellets, pellets flow control and aerodynamically stabilized to comply with the AAFF requirements.

The advantage of such a dispenser will be that a single dispenser design may be carried by any Helicopter with a cargo hook, limited only by its maximal takeoff weight.

.

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APPENDIX B - COVER LEVEL OF WATER FOR SUPPRESSION OF WILD FIRES

Sources:

1. The effectiveness and efficiency of aerial firefighting in Australia part 1 (M.Plucinski, J.Gould, G. McCarthy, J. Hollis - WIT.7541.001.0200_R)

Drop patterns and coverage levels research Substantial research has been conducted to determine coverage levels and drop pattern characteristics for a large number of aircraft and delivery system combinations. This work has built on previous studies focused on the design of delivery systems (e.g. George and Blakely 1973). Most drop pattern studies have been conducted in open areas, such as airport runways, in low wind conditions. The term ‘bare ground pattern the suppressant on the ground and thereby determine the drop pattern. These studies have been described by a number of authors (George and Blakely 1973; Robertson et al. 1997b; Suter 2000; Biggs 2004a; Lovellette 2004; Plucinski et al. 2006). Factors that have been found to affect the drop pattern shape and coverage levels include aircraft speed and height, wind speed and direction, the flow characteristics of the delivery system and suppressant viscosity. A few studies (Rawson 1977; Newstead and Lieskovsky 1985; Robertson et al. 1997a) have also considered the effect of canopy interception on drop patterns and have conducted trials under a variety of canopy types. The wide range of aircraft delivery systems can be modified to deliver similar mounts of suppressants (Rees 1983). Effective retardant coverage levels range from <0.5L m-2 for grass fires to >1.5L m-2 for eucalypt forest (providing a holding time upto 2h. (Loane and Gould 1986). Theoretically the coverage level required for suppressing fires in heavy fuels or logging slash may be as high as 4.0L m-2, but in practice the effective coverage levels are considerably lower. An extensive operations study of the use of aerial suppression in the United States of America found that an average coverage level of 0.5L m-2 (range 0.3 – 0.8L m-2) was effective on fires with flame lengths up to 2m (intensity approximately 2000kW m-1) in a wide range of fuel types. (George et al. 1990). The drop pattern of a typical Australian firebombing aircraft (e.g. PZL Dromader, Air Tanker 602/802) is such that maximum ground level retardant coverage under canopy rarely exceeds 2.5L m-2. Within any given drop it is estimated to be less than 10% of the total area would be covered at this level.

2. Interagency Aerial Supervision Guide (January 2011PMS 505 NFES 2544)

Airtanker Operations a) Airtanker Tactical Considerations

i) Airtanker advantages: Often reserved for initial attack because: ii) High cruise speed: Airtankers fly fast and arrive at most fires long before helicopters can be dispatched. Airtankers may be the only aerial resource available if an incident has no dip sites or portable mixing plant options. iii) Long range: High speeds and fuel loads allow airtankers to cover broad geographical areas. They often respond to multiple incidents on one flight.

b) Permanent Reload Bases – Airtankers are loaded at permanent bases. Portable bases able to serve all types of airtankers may be set up for special situations.

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c) Factors Influencing Drop Effectiveness and Coverage Level – A number of factors affect drop accuracy, line width and length, and coverage level required for particular fuel model and fire intensity. These factors include:

i) Pilot Skill – Ability to make accurate drops. ii) Aircraft make and Model – Each aircraft make and model has advantages and disadvantages in different operating environments. Performance elements include power, maneuverability, pilot’s visibility and airspeed control. iii) Tanking, Gating or Door System – Quantity of liquid, tank configuration, flow rate and door release mechanism. iv) Airtanker Drop Height – The minimum safe drop height is 150 feet above vegetation. Normally drops are made from 150 to 250 feet above vegetation. Increased height reduces coverage level and increases line width. The most uniform and efficient retardant distribution is attained when near vertical fall of the retardant occurs. The optimum drop height is when the momentum of the load stops its forward trajectory and begins to fall vertically. SEAT drop height 60 feet is above vegetation. v) Airtanker Speed – Airtanker drops, depending on the type of aircraft, range from 120-140 knots. Faster speeds generally reduce peak coverage levels, increase pattern momentum, and increase low coverage length. vi) Diving vs. Climbing – A diving maneuver tends to shorten the pattern and increase coverage levels. Conversely, a rising maneuver tends to toss or loft retardant and elongate the pattern. vii)Wind – The effect of wind is to deflect retardant and greatly increase the pattern’s fringe area. The effectiveness of retardant/water drops should be closely evaluated when wind velocities reach 15 kts. Retardant drops are generally not effective in winds 25 kts or greater. (1) Headwind: The effect of dropping into the wind is to shorten the line length and increase coverage level. (2) Crosswind drops will result in increased line width and cover a larger area at reduced coverage levels. viii) Flame Lengths – Direct Attack with retardants at the prescribed coverage level is generally effective in flame lengths up to 4 feet. Flame lengths from 4 to 8 feet require increasingly higher coverage levels. Retardant, unless applied in heavy coverage levels and greater widths, is not generally effective when flame lengths are greater than 8 feet. Long term retardant is most effective when applied to available fuels outside of the fire perimeter. ix) Canopy Density – Drops in timber or fuel models with a dense concentration of tall trees are often ineffective. Canopy interception significantly reduces penetration to ground fuels. An open canopy allows for better penetration. x) Availability of Ground Forces – Except in light fuels where extinguishing the fire with retardant may be possible, the ATGS must determine if ground forces will be able to take advantage of the retardant within a reasonable time.

d) Retardant Coverage Levels – Coverage level refers to the number of gallons of retardant applied on fuels per 100 square feet. Fire scientists have determined how many gallons per 100 square feet (GPC) it takes to effectively retard flammability in fuel models under normal flame lengths. Coverage levels range from .5 to greater than 8. The ATGS instructs airtanker pilots to make drops at specific coverage levels.

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e) Recommended Coverage Levels – The chart below identifies the recommended coverage level for each fuel model. The coverage level may need to be increased under more adverse burning conditions or when retardant does not effectively penetrate a heavy tree canopy.

Coverage Level Fuel Model Description 1 Annual Perennial Western Grasses, Tundra 2 Conifer with Grass, Short-needle Closed.

Conifer, Summer Hardwood. Long-needle Conifer, Fall Hardwood. Sagebrush with Grass

3 Saw grass, Intermediate Brush (green), Light Slash 4 Short needle Conifer (heavy dead litter) 6 Southern Rough, Intermed. Brush (cured), Black Spruce

Grater then 6 California Mixed Chaparral; High Pocosin, Medium Slash, Heavy Slash

f) Airtanker Drop Patterns – By opening one or more doors simultaneously or in quick succession, a variety of patterns and coverage levels can be achieved. The ATGS must know the number of doors that can be dropped singly or in combination, various drop pattern options, and the coverage level required for various fuel models.

i) Salvo Drop: One or more doors are opened simultaneously. Generally used on small targets such as spot fires or targets requiring heavy coverage levels. Rarely is a full salvo ordered. ii) Trail Drop – With multiple tank systems, two or more doors are open sequentially and at specified intervals giving continuous overlapping flow over a desired distance at the required coverage level. The same result is obtained with constant flow systems by opening the doors partially.

g) Heavy Airtanker Line Length Production Table – This chart displays line production by coverage level and gallons dropped for drops made at the recommended drop height and airspeed. The chart should be used as a general guide and will need to be adjusted for specific tank systems, airtanker make and model and the actual drop conditions.

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