On Thursday morning, 5 November, a white-and-red C-130 Hercules sat on the apron at Jakarta's Halim Perdanakusuma with the words NSW Rural Fire Service painted above its cabin windows. A few hours later it was on its way to Borneo, where months of peatland fires have filled the sky over East Kalimantan with smoke.

Australia has lent Indonesia one of its own bushfire tools, a C-130 air tanker. The Australian Embassy in Jakarta says a New South Wales Rural Fire Service C-130 Large Air Tanker, a Cessna Citation lead aircraft and a 20-person team will support Indonesian firefighting in East Kalimantan. Indonesia's disaster agency, BNPB, says the air operation runs for seven days, from 6 to 12 November.

A civilian tanker, not a warplane

Several early international reports described the aircraft as a military transport. The primary sources say otherwise. The Australian Embassy's release of 5 November names it as an NSW Rural Fire Service C-130 Large Air Tanker, and BNPB's own photographs from Halim show a tanker wearing Coulson Aviation and NSW Rural Fire Service titles, with an Australian flag beside the cockpit and the name Balder on the nose.

That matters, because the airframe is a Lockheed C-130 Hercules that has been converted for firefighting rather than a Royal Australian Air Force transport. Coulson Aviation, a Canadian company, flies large air tankers on contract to fire agencies, and the NSW Rural Fire Service has contracted its C-130s for Australian fire seasons before. Neither government has published the aircraft's registration, so Afterburner is not naming one.

The Cessna Citation travelling with it is the lead plane. In large air tanker operations a lead aircraft flies the drop run first, showing the tanker crew the line and checking the route for hazards before the heavy aircraft commits at low level.

Fifteen tonnes of water per pass

According to the embassy, the tanker can drop 15,000 litres of water per sortie, or just over 100,000 litres per day. Reuters quoted Ambassador Rod Brazier as saying the aircraft can fly up to six sorties a day. Indonesian officials have said the drops will be aimed at hotspots already mapped by the two countries' technical teams.

The choice of East Kalimantan came out of a joint technical assessment led by BNPB. In its release, the agency said the province had the second-highest number of hotspots on 5 November, behind only Central Kalimantan. It also said the area of land being worked on in East Kalimantan had grown 53 percent in its 4 November daily report.

BNPB said the Australian sorties are meant to complement ground crews and Indonesia's weather-modification operations, the cloud-seeding flights Afterburner reported on in August. The flag-off at Halim was led by BNPB head Lieutenant General Kristomei Sianturi and attended by Ambassador Brazier.

The 20 Australians include pilots, flight crew and paramedics. BNPB said the two countries would follow up with a further joint technical assessment to coordinate the operation.

ABC News Australia reports on the Australian firefighting team heading to Indonesia's fire season.

The worst fire season in 11 years

The deployment lands in a grim season. Reuters reports that Indonesia is battling its most intense wildfires in 11 years, mainly on Sumatra, Borneo and Papua, and that health ministry data counted more than 400,000 cases of acute respiratory infection in seven provinces as of 2 November. AFP cites the deforestation monitor Nusantara Atlas as estimating that more than 1.9 million hectares burned in the first nine months of the year.

The haze has also crossed borders, which is why outside help has been arriving. AFP notes that Japan sent about 350 Self-Defense Forces personnel and three helicopters to West Kalimantan in September, a mission Afterburner covered at the time.

Returning a 2020 favour

Both governments framed the mission as neighbours helping each other. The embassy points out that during Australia's 2020 bushfires Indonesia sent personnel from its national disaster management agency and its military to help, under Operation Bushfire Assist.

For the NSW crews the work is familiar, even if the terrain is not. A large air tanker over burning peat faces the same problem as one over Australian bush: the fire often smoulders underground, so water from above can knock down flames and slow the spread, but it cannot put out the peat by itself. The air operation is scheduled to end on 12 November. Any extension will depend on what the next joint assessment finds.

For now the job is simple to describe and hard to do. One converted Hercules, a lead jet and 20 people will try to drop as much water as they can on the hotspots BNPB has mapped in East Kalimantan, six times a day if the weather and the smoke allow it.

Sources: Australian Embassy Jakarta, BNPB (Indonesian National Disaster Management Agency), Reuters, AFP via Bangkok Post and TRT World, The Jakarta Post, Liputan6, ABC News (Australia)