Trump's Notre-Dame advice 'risible', says French fire chief

French fire chiefs on Tuesday dismissed comments by Donald Trump on how to tackle the fire which engulfed Notre Dame Cathedral, with one describing the US president's advice as "risible".

As the fire raged on the roof of the iconic Paris landmark Monday, Trump tweeted that "perhaps flying water tankers could be used to put it out. Must act quickly!"

But doing that would have brought the ancient cathedral crashing down, the fire chiefs said, in comments backed up by experts in Britain.

"Everything would have collapsed," said Lieutenant-Colonel Michael Bernier, a fire chief who speaks for France's civil defence organisation and who described the suggestion as "risible".

Releasing even one load from a Canadair water bomber used to fight forest fires on Notre-Dame would be "the equivalent of dropping three tonnes of concrete at 250 kilometres per hour (155mph)" on the ancient monument.

"It would have been like bowling at the cathedral... the two towers might have fallen.

"It was technically impossible, undoable and most of all would have been utterly useless" to douse the flames from the air, Bernier added.

Such a move would also have put the lives of firefighters and anyone in the area at risk, he added.

"Neighbouring buildings would have been hit by flying blocks of hot stone, and the whole area would have had to be evacuated."

- 'ATTENTION-GRABBING' -
Even using a helicopter to drop 1,500 litres of water would have left only the towers standing, Bernier insisted.

"The nave would have collapsed, the flying buttresses would have gone," he said.

Lieutenant-Colonel Gabriel Plus of the Paris fire brigade said that "everything was against" the first firefighters on Monday.

"Time and the wind were against us and we had to get on top of it fast. We had to make a rapid choice... and the priority we gave ourselves was to save the two bell towers, and both were saved," he added.

"Imagine if the woodwork in the belfries had been weakened, the huge bells would have collapsed" and that might have brought the towers down."

While armchair critics have suggested more could have been done to slow the fire, tough choices had to be made, said Plus.

Guillermo Rein, Professor of Fire Science at Imperial College in London, praised the work of the French firefighters.

"The Fire Brigade had to be aggressive fighting the big roof fire with the aerial ladders designed for high-rise buildings, but at the same time be gentle with the vulnerable structure of the stone vaults and walls. They did a fine job, and how they tackled this fire will probably be studied in the years ahead."

Consultant Martin Kealy, a member of the UK Institution of Fire Engineers, called Trump's advice on tackling the Notre Dame blaze "attention-grabbing".

"While dumping huge quantities of water may be an effective way to fight huge forest fires, it is unlikely to be an effective tactic on a city-centre building."