Dead Man Zone

by John Robertson

On 11th April our training divided into two sessions. Karen took one in the main Station, making space by moving out the trucks. This was ‘introduction to FM1’. Malcolm and Manuel were joined by three recruits from other Beaudesert Group Brigades for this session. It all went well. Jenny has had a most favourable impact on our FM1 training making it organised and thorough.

For those with FM1 or well along the road to doing the assessment, there was a knowledge evening with emphasis on the ‘Dead Man Zone’ concept. Paul showed an excellent video featuring Dr Phil Cheney of CSIRO and a big team of firefighters. The images of massive firestorms were impressive and daunting. Given optimum conditions (from the fire’s point of view) tree-top flames and fire-induced cyclonic winds can attain levels far beyond man’s capacity to control directly. This is what happened at the Canberra fires and what has happened at other catastrophic Australian bush fires in the past.

The ‘Dead Man Zone’ is any position within a 5 minute spread time of the fire. The video described specific fire events where a sudden wind change converted a flank fire into a head fire which travelled far more rapidly than the original blaze. In each case firefighters were overrun by the conflagration and killed. Two especial points were made; the first was that the ‘traditional’ fire speed tables seriously underestimate, by a factor of up to 5, how fast a really bad fire can move; the second was that severe fires on a wide front move a lot faster, apples for apples, than those on a narrow front. This is highly relevant when a wind change converts a fire with a fairly narrow head but a long flank into a very wide and fast moving head fire on what was previously the flank. In worst case conditions such a fire can advance 1,000 metres in 5 minutes. Phil emphasised that this speed is that of the main fire front. ‘Spotting’ is a usual accompaniment of bad fires and brings its own very critical hazards but it is not what makes the main fire front advance at up to 1 km in 5 minutes. It is vital for fire crews to have a safe anchor point to which they can dependably retreat if such a thing happens. Generally this point will be ‘in the black’. There was a lot of discussion of the video and every member present told of one or more incident when they had experienced what was described on the video, albeit of a less grave nature. The discussion was as valuable as the excellent video itself. Paul is organising more such sessions.

We then had a video from Roger and Jenny about use of blowers in bush firefighting in SE Queensland. This showed how effective a blower can be as a ‘force multiplier’ – 1 person with a blower does the work of 4 with beaters or rakehoes. This is an invaluable feature when manpower is short. Our Brigade has seen this excellent multiplier effect of blowers in action, first at Ripley Valley in 2005 and recently at other fires where we have been supporting neighbouring Brigades. The video also laid stress on the need to use a blower with the largest engine and the biggest air blast available. (A lower powered blower may flip-flop from extinguishing the fire to fanning the flames and making them burn more fiercely.) The specified model is the very powerful Shindaiwa EB630.

The best news of the night came from TM1. John took the initiative to sort out the way our TMRFB pager system has worked, or failed to work, over the past two seasons. Brigade areas have been re-arranged to reflect the distance and speed of access to a given location rather than slavishly to follow local government boundaries. The QFRS person previously in charge of Firecom SE has been moved and a new officer is in that post. Does this mean that all our pages will work perfectly from now on? Of course not. Does it mean a substantial improvement taking us from an unacceptable outcome to an acceptable one? Yes. We look forward to seeing the benefits.

Posted in Training