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364 T.Konishietal./FireSafetyJournal43(208)363-375 arehighlydangerous.Topreventthefirespreading，itis a
Topview
Mock-uphouses
|7.2m
‘l
obviouslyimportanttodumpwaterontothefiresasmuch andasearlyasposibleduringthelimiteddaytime.This leadstotheotherdefect.Thewaterdumpbyhelicoptersis not always suficient to control large fires，since the Japanesefirefightinghelicoptersoperatedbyfiredepart- mentsoflocalgovernmentscancarylesthan1.5tonsof waterandtheamountofwaterthatcanbecariedaloftisa criticalisue.Althoughmanyhelicoptersflyingparalelcan dumplargeramountofwater，theposibilityofcolisions duetothefrequentflightsmayincreasesubstantialy[9，10].
Nevertheles，ifaerialfirefightingcaninhibitfirespread- inguntilagroundfirebrigadearivesatthefirefield，even thoughthefireisnotcompletelyextinguished，itcanbe judgedthataerialfirefightingis~ffective. Inorderforaerial firefightingtobemostefective，acurateengineringdata ontheoptimumwaterdumpfromhelicopterstofiresis ne eded. The fiow pat terns of the dropping water from helicoptersandaircraftsareinvestigatedinCFDsimula- tions[3，1，] andbyrealaircrafttestsandwatersuply [1，12，13].Whatiscrucialyimportantindeterminingthe firefighting strategies [12，14，15] are fiying sped，the quantity ofwater and water release intervals.National ResearchInstituteofFireandDisaster(NRIFD)inJapan conducted thre large-scale experiments in order to
Winddirection
investigate advantages and disadvantages of aerial fire
問
b
自ghtingusinghelicoptersinTokyoin196and197andin Hokkaidoin19[16-18].
Thispaperisareportofaseriesofexperimentsthatwere conductedinOitain 19incoperationwiththefire department authorities of Oita city government，four prefectural governments and the Japan Ministry of Defense.Thisexperimentexaminedtheposibilityofaerial firefightinginanurbanareawithcombustiblesscateredon theroadandwithrofsofhousesdamaged.Thisextensive experiment，whichhasprovideddetailedinformationabout aerialfirefightingagainsturbanfires，isthefirstofitskind intheworld，asfarastheauthorknows.Thedataprovided by this report wil be very helpful in determining fire- fightingstrategiesusinghelicoptersinemergenturbanfires.
2. Experimental methods 2.1.Mock-uphouses
We conducted two experiments，one using mid-size helicoptersandtheotherusinglargehelicopters.
Insimulatingurbanfiresafteranearthquake，agroupof
mock-uphouseswereassembledforboththeexperiments.
Fig. 1(a) shows a schematic il lustration of the mock-up
housesusedforthefirstexperiment.Thefirstexperiment
field，whichwaspreparedforaerialfirefightingbymid-size
helicopters，consistedoffivewoodenhouses.Althewals
andcolumnsweremadeofwood.Thelargecenterhouse， theirsizewasthesame，7.2mlong，7.2mwideand0.5m
7.2mlong，7.2mwideandl.8m high，wasbuiltinthe centeroftheexperimentalfield.Theotherfourhouseswere built3m apartfromtheouterwalofthecenterhouseand
Sideview
L ア dm|
ザメ
Mock-uphouses Topview
Mock-uphouses
Ignitionbymethanol-soaked coUonrags
Wodtrails W=50kg/m2
|陶減問|
Fig. 1. Schematic il1ustration of mock-up houses used for (a) the first
high.Onlythecenterhousehadaroof，andtheothersdid not.Inordertoimitatescrapwoodthatwouldbescatered ontheroadafteranearthquake，pilesofwoodwerelaid
Wodtrails W=25kg/m2
idevi巴w
| 陶 凶 W 1 :1 1 地 碕 即 |
ーい
Mock-uphou回 S /
ア一二
experimentand(b)thesecondexperiment.
Ignitionbymethanol-soaked cotonrags
川-v
