The heater pipes came down from the engines to a 90-degree elbow with a valve on it - this has been known to fracture and blow off, leaving a ton of shredded soundproofing and a really loud noise that you can't turn off!
Which lead, I believe, to the quote from the pilot to the Radop (who was standing between the pilot seats):
"Crikey Eric, I thought that you had exploded!"