- Lessons learned from an indepth analysis of 40 years of Australian Bushfire Tanker Burnovers.

Introduction

The overrunning of a Bushfire tanker by fire remains a significant cause of bushfire fighter deaths in Australia, with over 25 such incidents, involving some 38 fatalities, recorded. This paper analyses all known cases of bushfire appliance fire overrun, or "Burnover", on record in Australia, and suggests vehicle modifications to improve crew survivability in such situations.

A review of previous Burnovers in Australia

Table 1 lists, in order, all known fire appliance burnovers in Australia. The causes of these incidents has been discussed previously (1). Below is a selection of cases which may prove informative with regard to crew survival.

Wandilo, 5 April 1958: Several Forestry Department trucks were part of a group of vehicles attempting to control a fire in a pine plantation when a "sudden and dramatic increase in the wind resulted in a fire storm". In their efforts to escape, 3 of the vehicles became stuck in the soft sand of a firebreak and were overrun by the fire. Three of the firefighters survived with moderate burns, 2 by sheltering in the cabin of one vehicle and another by lying down in a deep wheel rut in the sand. The other 8 men were all killed by the fire as they fled. All 3 trucks were destroyed.

Longwood, 22 February 1980: The Bridgewater Tanker was engulfed by a fast uphill running grassfire on a day of extreme fire danger. It reversed out of the flames after a 15 second immersion, but immediately ran into a tree which immobilised the truck, and shut down the pump, disabling the sprinkler system. The truck was then burned over whilst the crew sheltered in the cabin. All 5 survived with moderate burns.

Waterfall, 3 November 1980: Headquarters Brigade Tanker 81was trapped on a firetrack in bush after being ordered from the area. The tanker was apparently caught by a finger of fire coming out of a gully in a sudden "blowup" . The crew of 5 were burned to death sheltering under the truck. The truck did have 38mm hoselines that could have been used for self defense, but none had been used.

Grays Point, 9 January 1983: Heathcote Tanker 81 was a 1964 Bedford RLHC 4x4, essentially similar to the Headquarters 81 Tanker destroyed in the same area 3 years before. The tanker and its 10 crew was one of a number of vehicles engaged in fire suppression in bushland on "Anana Hill". All the vehicles were ordered clear as changing conditions made the hill dangerous. The crew of Heathcote 81 apparently did not appreciate the danger and were too slow to depart, and found their only exit blocked by fire. The tanker reversed back up the track away from the fire then stopped. At about the same time, a civilian on foot was spotted further up the hill and 2 crew were despatched to bring her back to the tanker. She declined to be rescued and was instead accompanied safely off the hill by one of the crew. The other man returned to the tanker. The tanker crew then lit a self defense back burn, although this apparently flared up and did not assist them. A few minutes later, the tankers engine stalled and could not be restarted. This however did not cause the burnover as the vehicle was already trapped. It was then overun by fire whilst parked on the firetrack. All of the crew sheltered outside of the truck, initially behind the front wheel, and then in a huddle in the middle of the road. Three of the crew were fatally burned, and the other 6 seriously. No attempts were made to operate hose lines for protection. The drivers cabin was too small to hold the whole crew, but survived the burnover with superficial scorching and could have provided a refuge for some.

Upper Beaconsfield, 16 February 1983: The Panton Hill and Narre-Warren Tankers were part of a 5 tanker group attempting to secure the quietly burning eastern flank of a major fire on a day of extreme fire danger and multiple major fires. A forecast westerly wind change arrived early, with a 90 degree windshift and 80 km/h winds, and the eastern flank became active. The 2 tankers attempted to depart, but were overrun on a narrow fire track by fire running uphill in heavy bush. The 7 crew of the Narre-warren Tanker were all found dead, 3 in the front cabin of the truck, and 4 on the ground around the truck. The 5 crew of the Panton Hill Tanker were also found dead on the ground around their burned out truck. Two other tankers were also overrun in a clearing nearby at about the same time, sustaining serious scorching but remained operational without crew casualties.

Mount Bonython, 16 February 1983: The Carey Gully Tanker with 5 highly experienced crew was in transit down a steep, narrow firetrack in heavy bush on a day of extreme fire weather. They discovered a small spot fire on the uphill side of the road and were stationary fighting it when another fire "appeared from nowhere" across the track in front. The driver attempted to reverse back up the firetrack, but ran off onto the shoulder in heavy smoke and reversed into a tree. Almost immediately, the fire overran the truck "we had about 3 seconds before a fireball hit". Two crew sheltered on the floor of the driver’s cabin, suffering minor burns. The rear of the truck had high sides for radiant heat protection, but the 3 dismounted crew were unable to climb back onto the rear as it was fully immersed in flame. They ran back up the fire track seeking safety. One was rescued uninjured by a private motorist further up the track, the other 2 took shelter, one in a clearing where he sustained serious burns, and the other in a culvert where he perished. The rear of the truck caught fire during the burnover, and fire subsequently consumed the truck. The cabin filled with smoke, but did not ignite until after the crew evacuated. The truck petrol tank was found to still contain fuel after the fire burned out

Ridgeway, 1990: An ISUZU 4x4 dual cab diesel Tanker was parked in front of houses on a ridgetop with fire approaching uphill in heavy bush. The fire was still a kilometre away when it spotted over the ridgetop onto the base of the slope behind the vehicle then ran back upslope towards the truck. With their escape route cut, the crew were forced to park in a clearing on the ridgetop and await the arrival of converging crown fires. Spray Bars were used, driven by truck pump. The fire passed over ín a deluge of sparks whilst the crew sheltered in the cabin. All 3600 litres of water available were consumed by the spray system during the burnover and the crew then bailed out during the burnover and sheltered behind a nearby house. The truck was seriously scorched, and the rear caught fire with significant external damage, but no crew injuries.

Toolara, 22 September 1991: 3 crew in 2 light Toyota 4WD traytop units responded to a fire in a pine forest in unusually severe fireweather conditions (McArthur FDI 48) and attempted to hold the fire on a fire track within the plantation. None donned the available protective clothing. They underestimated the fires rate of spread, and Vehicle 1 was quickly engulfed by flames. The occupant abandoned the vehicle and ran for safety. He survived, but was seriously burned. The 2 occupants of Vehicle 2 attempted to drive to safety along the track, but were trapped on a dead end. They turned the vehicle around and attempted to drive back through the flames to safety. In the process, the vehicle became beached on a stump and the crew sheltered inside the cabin, spraying themselves with water from the knapsack as the fire passed over. They abandoned the vehicle after about 10 minutes, at that stage finding the tyres well alight. Both suffered minor burns.

Creswick, 21 January 1997: The Glen Park Tanker was fighting a spot fire from a fire track in a Eucalyptus forest. Weather conditions were severe, and when threatened by the main fire, the driver turned the truck around to depart, but the engine stalled and would not restart, possibly due to an electrical fault rather than ingestion of heat and smoke ("it just ‘clicked’ and would not turn over"). The truck was then burned over from the rear. 2 crew sheltered in the cabin under a blanket and 3 in the crew haven on the rear, operating 2 fog lines for protection. The diesel pump motor continued to operate, but the remaining 1000 litres of water was expended during the burnover and the rear tyres caught fire, subsequently destroying the truck. All 5 crew survived uninjured.

Gwabegar, 2 December 1997: State Forests Tanker FC 5296 with 2 crew was patrolling a newly bulldozed firebreak in light bush. They stopped to deal with a small, small low intensity spotfire which had crossed the break when they were suddenly overrun by the main fire. They attempted to reverse to safety, but reversed off the track in dense smoke and stopped. They sheltered in the cabin as the fire passed. The cabin filled with thick smoke "from the door seals" whilst the crew sheltered under a blanket. After 3-5 minutes, the 2 were forced to bail out of the tanker. They sheltered under blankets as they ran to a clearing. One sustained moderate burns after exiting the tanker, the other was only slightly burned. The truck was destroyed.

Wingello, 1 January 1998: The Wingello Tanker crewed by 8 members of the Wingello Rural Fire Brigade was conducting a back burn with State Forests units in calm conditions from a fire trail in eucalypt forest (about 12 tonnes per hectare) to contain a small fire (caused by lightning strike) until a bulldozer arrived. A change in behaviour of the main fire was noticed and the crew withdrew from the back burn area along the fire trail. An intense transient wind, probably from a microburst from a cloud formation about 1 to 2 kilometres away, rapidly pushed the original fire up across the fire trail as the tanker was exiting along it. Two crew sheltered in the drivers cabin, and the other 6 sheltered in the crew compartment under fire blankets. The driver was killed within the cabin. The other crew members bailed out when conditions became untenable and evacuated onto burned ground, suffering further burns from the hot ground. All 7 survivors were burned, 3 critically. The back burn area was not affected by the main fire over-run. A State Forests unit, exiting ahead of the tanker, escaped damage.

Linton, 2 December 1998: The Snake Valley Tanker with 5 crew was attacking a small spot fire from a fire track in heavy bush when the fire suddenly flared up and overran the truck. The driver "drove through 200m of flame" to reach a clearing. The rear crew used charged lines for protection but exhausted their water supply (approx. 700 litres was available) and were forced to lie down on the tray as the vehicle travelled through flames. The vehicle was seriously scorched, with the battery and external fittings melting, One crewmember seriously burned his hands on the hot door handle climbing into the cabin and 2 of the rear crew suffered minor burns.

Linton, 2 December 1998: The Geelong West Tanker was one of 3 similar tankers on a firetrack leaving the fireground at night in mild conditions. Two trucks were over run by a sudden flare up of the fire due to a wind change in heavy bush. The 5 crew of Geelong West sheltered in the truck, but it was out of water and was destroyed in the burnover and all 5 were killed. The similar Geelong City Tanker was on the track just ahead and was also burned over in the same incident: "within about 2 seconds we were fully engulfed, with flames coming right over the cabin the wind was horrific". Two crew sheltered in the cabin under blankets, the other 3 in the crew haven on the rear, operating self defense hoselines, exhausting the available 1000 litres of water just after the fire passed. The truck survived with superficial damage and no crew casualties.

Wandilo, 1958: early lessons regarding vehicular resistance to fire.

The inquiry into the Wandilo disaster (2) identified radiant heat as the principle threat and suggested a number of vehicular improvements to allow survival in similar incidents. These included the provision of "properly protected vehicle cabins", large enough to accommodate the entire crew, or "the use of survival tents". Initial recommendations also included the use of asbestos lining in the doors of the vehicles, though this suggestion was later changed to the use of a cheaper reflective blanket on the premise that radiant heat (not flame contact) was the chief threat. It should be noted, however, that the Wandilo burnover occurred on a wide firebreak in a pine forest, and subsequent experience has suggested that Wandilo was not a typical Australian Burnover. The majority of incidents occurring subsequently have occurred on narrow tracks in Eucalyptus forest and many have involved significant flame contact (1). In such circumstances, direct flame contact, not radiant heat, may be the greater threat. Other recommendations from Wandilo included the provision of high sides to protect the deck crew from radiant heat, and water sprays to protect the deck crew and the vehicle.

The Wandilo enquiry also concluded that petrol vaporisation may have contributed to the immobilisation of one of the trucks preceding the burnover. Subsequent experience on Ash Wednesday 1983 confirmed that this was a frequent problem when carburetor induction, petrol fuelled vehicles were used under severe conditions and has led to the adoption of diesel engines and pump motors as standard for Australian bushfire appliances. Also noted was the claim that the petrol tanks of 2 of the Wandilo trucks had exploded. Subsequent trials (3) and real world experience has suggested that this occurrence is unlikely, although the recommendation that fuel lines be protected remains valid.

The 1969 Emergency Fire Service Manual (4) largely agreed with the Wandilo report, suggesting that a safely designed vehicle should include high sides, fuel and electrical system protection, water sprays and a crew haven on the working deck.

The Longwood Burnover, captured on video.

The loss of the Bridgewater Tanker on Ash Wednesday 1, 1980 involved a vehicle incorporating many past and present protective features and was captured on video by a professional TV crew. As such it is one of the most informative incidents ever documented in this country. The vehicle was a 1967 Bedford Tanker. Though petrol engined, it incorporated high sides which extended below tray level, protecting the fuel and electrical systems and was fitted with an electric auxilliary fuel pump to reduce the risk of fuel vaporisation. In addition, fixed sprinklers were fitted to the grab rails around the edges of the heat shields and were in operation at the start of the burnover.

The Bridgewater Tanker was stationary on the roadway above an uphill running grassfire of severe intensity on a day of extreme fire weather when it was engulfed by the fire. The video clearly shows the sprinklers in operation at the start of the burnover. They are throwing a considerable curtain of water to both sides of the vehicle. As fire engulfs the vehicle, it begins to reverse out of the flames. There is direct contact with flames exceeding 20 feet in height for about 15 seconds as the vehicle reverses. Despite this, the vehicle does not become immobilised. One of the crew is visible lying down on the tray as flames engulf the truck. The high sides clearly provide useful protection. Despite the sprinkler system, the high winds and intense flames still allow direct flame contact with the vehicle as it is immersed in flames. The vehicle is successfully reversed out of the flames, but almost immediately runs off the road shoulder and into a tree. The contact with the tree disabled the pump, shutting down the sprinkler system and immobilised the truck, allowing it to be burned over again by the fire whilst the crew sheltered in the drivers cabin. The truck was destroyed and all 5 crew sustained moderate burn injuries.

This incident illustrated a number of points, firstly that, contrary to other reports, the typical Australian burnover may well involve a significant component of direct flame contact, not just radiant heat exposure. It documented the severe wind and flame conditions that may be experienced during even a grassfire burnover, and demonstrated the need to ensure that the defensive sprinkler system is resistant to both heat and impact. The phenomenon of reversing "out of trouble into trouble", frequently into a tree, has occurred repeatedly in Australian burnovers.

Lessons from Linton: an illustration of the benefits of "active defense" with water

The Linton burnover was highly informative in that 2 essentially similar tankers were burned over simultaneously whilst only one was defended with water. The undefended tanker was destroyed with the loss of its 5 crew whilst the other tanker survived with superficial damage. The incident starkly illustrated the potential benefits of "active defense" of the vehicle with water. As such, it has sparked considerable interest in the provision of defensive sprinkler systems. Real world experience, however, suggests that the amount of water required for successful vehicle defense is large. Data is available on 5 Australian burnovers in which active defense with sprinklers or hoses was used (1). In each case, large volumes of water (from 700-3600l) were exhausted, and all the vehicles were still destroyed or damaged, albeit with crew survival. The Linton and Creswick burnovers were both typical Australian burnovers in that they occurred on narrow trails in eucalyptus forest. In each case, the vehicles were defended with 1000 litres of water using hand held hoses. In both cases the crews survived without serious injury, although both tankers caught fire during their burnovers. The Glen Park Tanker was subsequently consumed by fire, though the Geelong City Tanker survived with superficial damage. These 2 cases suggest that crews can survive a typical Australian burnover if they defend their vehicles with hand held hoses and 1000 litres of water.

Fixed sprinkler systems have also been fitted to Australian Bushfire appliances since the 1970’s. Such systems have usually been designed and installed on an individual basis by local brigades. Typically they consist of a number of small sprinkler nozzles on a rail or ‘spray bar’ and are intended to project a curtain of water over both sides of the vehicle in the event of a burnover.

Appendix 1 contains a theoretical calculation of the minimum water requirements for self defense sprinkler systems during fire tanker burnovers. This calculation concludes that a minimum of 2000 litres of water (1000 lpm for 2 minutes) would be required to fully protect a typical Australian Heavy Bushfire Tanker from a typical burnover using present ‘all over’ sprinkler systems. The use of 1000 litres (500 lpm for 2 minutes) might allow survival, albeit with serious vehicle damage and the possibility of significant crew injury.

It should be noted that sprinklers and hoselines have many dissimilarities as defensive tools. The primary role of the sprinkler is to create a curtain of water between the vehicle and the heat source, thus absorbing radiant heat. Whilst such a system can function independently of an operator, allowing the crew to shelter in the cabin, its efficiency is limited by its vulnerability to winds and its lack of aimability. Conversely, a hoseline may be more effectively aimed in the direction of the threat, and can knock the fire down at a greater distance, but may expose the operator to greater risk. Of the 5 Australian burnovers in which active defense was used, 2 involved fixed sprinklers and 3 hand held hoses. All of the trucks were damaged, and one of each group was destroyed.

Finally, it should be noted that pumps are a vital part of any defensive system involving water, and so they should be running at all times on the fireground, protected against heat, and resistant to impact with tree branches if, as often happens, the vehicle is reversed into or through trees or bushes whilst attempting to escape.

Other lessons learned

The typical Australian burnover occurs on a narrow track in eucalyptus bush following a sudden intensification of the fire, usually following a wind change. What follows is a short, intense burnover, probably involving first a period of radiant heat contact, and then a period of direct flame contact for a total of 1-2 minutes. The time to prepare for the burnover is often extremely short, sometimes mere seconds, so protective systems need to be designed for speedy operation. In addition, protection must be provided for the crew on the tray, even in dual cab designs, as there may not be time to enter the cab. On occasions, crews will be unable to return to their vehicles, or forced to evacuate from them into a still hostile environment. In these situations, some form of portable protection, e.g. a personal fire shelter, may provide useful additional protection.

In many cases, bushfire appliances appear to have been constructed with little regard for their resistance to heat. Vital components are frequently flammable and exposed, including fuel lines, brake lines and batteries and electrical wiring. Damage to these components may contribute to vehicle entrapment. Extension of existing heat shields a small distance below tray level would provide useful protection for these systems, but could compromise off road ability if excessive. Flammable external fittings or stores, including fuel containers, plastic Bull Bars, mudflaps and traffic control cones are frequently found, and may contribute to vehicle ignition during a burnover. Bushfire appliances should be constructed to minimise these unnecessary vulnerabilities.

Modern truck cabins are incorporating larger glass areas and increasing amounts of flammable materials. Early ignition of these materials is possible and may force the crew from the cabin during an otherwise survivable burnover. Modifications are needed to reduce transmission of heat loads through vehicle windows and door skins.

Conclusions

Many of the systems required to protect bushfire appliances from fire have been available for many years. Despite this, available solutions are not always used, and existing vehicles are often unnecessarily vulnerable to heat. Analysis of 40 years of incidents suggests that a typical Australian Tanker Burnover occurs suddenly, on a narrow trail in Eucalyptus forest, and involves 1-2 minutes of exposure to both radiant heat and direct flame contact. Survival requires both active and passive defensive systems. Active defenses (fixed sprinklers and hand held hoses) are effective but require large volumes of water, hence passive defenses are also required. Passive defenses include high sides, reflective window curtains and heat shields for vehicle doors. The minimum protective equipment for bushfire tankers should be:

Discussion and conclusion

It seems therefore, that present active defensive systems using sprinklers are useful but limited, and should be regarded as adjunctive defenses. Attention to passive defensive systems (eg heat shields) is also required. Several further points should also be noted with respect to defensive sprinklers: Firstly, whilst large volumes of water are required to absorb all of the energy of a burnover, it is not of course necessary to absorb all of the energy of the burnover to provide useful benefits for vehicle and crew. Conversely, however, even if the sprinkler system is capable of absorbing all of the energy of a burnover averaging 100kW/m2, there will still be times during the burnover when peak intensity exceeds this and some degree of damage to the vehicle will still be likely. Finally, it should be noted that the large water requirements for existing defensive sprinkler systems relate principally to their low efficiency. Simply dividing the sprinkler system into separate halves could double its water efficiency. Other research initiatives currently underway in New South Wales may identify other means of significantly improving sprinkler system efficiency. In the final analysis, however, active defensive systems will always be reliant on an adequate supply of water and the continued operation of the pump. As such, they should always remain adjunctive defenses, and proper attention to passive defenses will also be required.

Last updated 4 November 2014