US Army Grounds Entire Fleet Of Chinook Helicopters After Reports Of "Engine Fires" US Army Grounds Entire Fleet Of Chinook Helicopters After Reports Of "Engine Fires" WSJ reported one of the US Army''s top heavy-lift helicopters was grounded in the last 24 hours due to a risk of engine fires. US officials said the Boeing CH-47 Chinook helicopter fleet (about 400 helicopters) had been grounded after numerous engine fires were reported. One of the officials said no injuries or deaths occurred during any of the incidents. They said the latest occurred a few days ago. The US Army Materiel Command grounded the fleet of CH-47s "out of an abundance of caution." Officials have narrowed down more than 70 helicopters that contained a part that could be the source of the fires. An Army spokeswoman told WSJ the defected part is causing fuel leaks that sparked "a small number of engine fires among an isolated number" of the helicopters. She said maintenance crews are taking steps to resolve the issue. "The grounding was targeted at certain Boeing Co.-made models with engines manufactured by Honeywell International Inc.," WSJ said, citing one of the US officials.