The official report into the Clutha tragedy in Glasgow, Scotland, in which 10 people died has renewed calls for police helicopters to be fitted with flight recording equipment.
The long-awaited conclusions of the Air Accidents Investigation Branch (AAIB) confirmed that the helicopter which crashed in to the packed pub did not have a flight recorder.
Following a fatal air ambulance crash in July 1998 the AAIB recommended that the Civil Aviation Authority (CAA) should "encourage the development" of lightweight and low-cost flight recorders and "consider" whether they should be used in emergency service helicopters.
Similar statements were made by the AAIB to international aviation regulators following private helicopter crashes in July 2003 and January 2005.
Following the Clutha crash, the AAIB has gone further and recommended that the CAA "requires" all police helicopters to be "equipped with a recording capability that captures data, audio and images in crash survivable memory".
But new helicopters should only be required to have full black box flight recorders from January 2018, the AAIB added.
The AAIB report concluded that the pilot did not follow emergency procedures after a fuel warning in the cockpit.
Investigators found that two fuel supply switches were off yet the helicopter continued to carry out three surveillance jobs over nearby Lanarkshire rather than land.
The pilot, David Traill, who was attached to Police Scotland's air support unit, was a highly experienced former RAF and training pilot with more than 5,500 flying hours in helicopters.
The report stated that it remains unclear why the fuel supply switches were in the off position, ultimately leading to both engines cutting out.
It also found that the helicopter's low fuel warnings were triggered and acknowledged five times during the flight.
The AAIB added that the pilot did not complete the emergency shutdown checklist following the first engine failure. The second engine failed 32 seconds later.
It was not known why a successful autorotation - the landing of a helicopter without power - was not achieved.
Aviation safety expert David Learmount said police forces have not previously used flight recorders because "they are expensive".
He explained: "It's just budget. That is all it's about because they could have put things on board."
Mr Learmount, who is consulting editor of Flightglobal magazine, said technology has developed which means devices to record flight information can be made small enough to be used on helicopters.
"With big airliners you can put on a large heavy box, but a helicopter is lightweight and hasn't got much space," he said.
Flight recorders for helicopters have to be "small and light", he added.
"A number of years ago miniaturised, clever pieces of electronics were difficult to design and expensive, but they're less so now.
"(The AAIB) can make recommendations for things that would not have been practical previously."