A fatal accident inquiry (FAI) found McRae had been "imprudent" in embarking on demanding manoeuvres in difficult terrain, "contrary to the principles of good airmanship".
Sheriff Nikola Stewart, who ruled the fatal crash could have been avoided, confirmed that the sportsman did not hold a valid flying licence and should not have been flying the aircraft at the time.
McRae, 39, his five-year-old son Johnny, the boy's six-year-old friend Ben Porcelli and Graeme Duncan, 36, all died when the aircraft came down near McRae's Jerviswood House home in Lanark on September 15 2007 as he flew home from a trip to see a friend.
The Eurocopter Squirrel helicopter crashed into trees in steep ground on the south bank of the Mouse Valley water before bursting into flames.
Ben's parents had no knowledge that their son was on the flight and had not been asked for their consent.
The inquiry, which sat over 16 days this year at Lanark Sheriff Court, today concluded the deaths could have been avoided if McRae had not engaged in unsafe low-level flying.
"It would have been a reasonable precaution to refrain from flying helicopter G-CBHL into Mouse Valley wherein the pilot engaged in low-level flying when it was unnecessary and unsafe for him to do so, and whilst carrying passengers on board," she stated.
The sheriff found there was "no operational or logistical reason" for McRae to have descended into the valley at speed.
"It is difficult to avoid the conclusion that his intention was to conclude the flight as he had started it, with a spectacular and dramatic fly-past of the valley and its vegetation, followed by a steep climb out prior to coming into land, all for the benefit of his passengers," she said.
In her written determination, the sheriff concluded: "The deaths and the accident resulting in the deaths might have been avoided had Mr McRae not flown his helicopter into the Mouse Valley.
"Such a precaution would have been entirely reasonable. There was no necessity to enter the Mouse Valley. There were no operational or logistical reasons to enter the Mouse Valley.
"Mr McRae chose to fly the helicopter into the valley. For a private pilot such as Mr McRae, lacking the necessary training, experience or requirement to do so, embarking upon such demanding, low-level flying in such difficult terrain, was imprudent, unreasonable and contrary to the principles of good airmanship."
The official purpose of an FAI, held under the 1976 Fatal Accidents and Sudden Deaths Inquiry (Scotland) Act, is not to apportion blame for any death in either the civil or criminal sense. It is said to be a "fact-finding exercise carried out in the public interest".
McRae's father Jimmy said he hoped the family would be able to "move forward" after four "extremely difficult" years for all the families concerned.
He said: "We still believe we will never know what caused the crash but we were never in any doubt as to Colin's prowess as a fine pilot.
"Everybody knows from Colin's rallying career that safety is always an issue and that his reactions and eye and hand co-ordination were world-class."
The ruling states that the accident happened when, due to an "unknown occurrence", the aircraft deviated from its path and crashed.
The sheriff said the cause of the change in route could not be determined but a technical malfunction, interference with the controls, or a bird strike could not be ruled out. Pilot "disorientation or misjudgment" from low flying at speed could not be discounted.
But the sheriff stated: "I remain firmly of the view that whatever occurred in the final seconds to prevent Mr McRae using his undoubted skills to avoid colliding with the trees, the accident would have been avoided had he not chosen to fly down into Mouse Valley."
Sheriff Stewart said a recording of the flight, filmed by Mr Duncan, a former quad bike racing champion, showed McRae had consistently flown the aircraft at unnecessarily low heights that day.
She wrote: "He undertook significant manoeuvring at low level and the helicopter seems to have encountered significant g-loading as a result, to the evident enjoyment of his passengers.
"The episodes of extremely low-level flying and the excessive manoeuvre parameters, particularly the descent into the valley by Larkhall, all as captured on the video recording, are indicative of an aircraft being flown imprudently, without due regard to the principles of good airmanship and in such a way that normal safety margins would be reduced."
The sheriff said the fact that McRae, who had "considerable flying experience" but no valid licence or authorisation for operating the helicopter, had shown a "somewhat cavalier attitude" to safety regimes.
Sheriff Stewart spoke of the "unimaginable" anguish which stemmed from the sportsman's decision to take the children on the flight.
"As a matter of simple, awful, logic, if Ben had not been on board the helicopter that day, he would not have died in the accident," she said.
"I do not doubt that his parents' suffering is compounded by their lack of knowledge that he was on board and their lack of opportunity to give or refuse informed consent to his being a passenger."
Married McRae, who also had a daughter, Hollie, was regarded as a local hero in his home town of Lanark after winning the world rally championship in 1995.
He was from a racing family as his father was a five-times British champion and his younger brother Alister also raced in the world championships.
His fame as a rally driver led to him becoming well-known on the high street as the computer game he lent his name to became a worldwide hit. He was awarded an MBE in 1996.
PA
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