Flight recorders to reveal final moments of MH17: A Malaysian investigator with one of the black box flight recorders at the handover. Credit:AP "It would have recorded the sound of the explosion, which under forensic analysis, would reveal what type of explosion it was," aviation security expert and commercial pilot, Desmond Ross said. The sound of the explosion would allow forensic analysts to determine if the missile fired at MH17 was indeed the SA-11 BUK. The BUK has been identified as the weapon that shot down MH17 by preliminary US intelligence reports. “Our assessment is that Malaysian Airlines Flight 17... was likely downed by an SA-11 missile, operated from a separatist-held location in eastern Ukraine,” US Ambassador to the United Nations Samantha Power told the UN Security Council earlier this week. Geoff Dell, an Australian accident investigator, agreed, but said the sound could come down to a nanosecond.

Inside the black boxes. "We do assume that if the crew doesn't get a may-day call out, it's all happened pretty quickly." Dr Dell also raised the possibility that the pilots may have seen the missile coming and attempted to avoid the catastrophic explosion. Crash investigators declare it a priority to secure crash site: A pro-Russian rebel examines the MH17 wreckage. Credit:AP "If it was fired from some distance away, then maybe the crew saw it coming and tried to take evasive action," he said.

The cockpit recorder and flight data would have recorded any evasive action taken by the pilots. Cockpit audio recorder will prove vital: Black box is discovered at the crash site. Credit:Reuters Crucial to establishing how fast the plane plummeted to earth are recorded losses in altitude and pressure, which the flight data recorder would have registered. In turn, the loss of cabin pressure would indicate whether the missile blew a single hole in the cabin, or thousands of smaller shrapnel holes. This would allow investigators to confirm the size and type of missile that struck the cabin.

A standard flight cabin is pressurised to 8000 feet as it climbs above the earth. MH17 was at an altitude of 33,000 feet when it was shot down. "[The data] would tell us about the instant depressurisation and decompression from 8,000 to 33,000 feet, " said Mr Ross. But determining what type of missile struck MH17 may ultimately hinge on the site investigation, experts say. In a normal crash investigation, the site would be secured and every piece of debris would be painstakingly marked, with a grid formation established. The evidence could then be carefully removed by investigators to a controlled environment.

After the 1988 Pan Am crash in Lockerbie, Scotland, investigators successfully re-constructed the fuselage of the plane and were able to determine the area, size and type of the explosion, leading to the eventual prosecution of the bomb makers. Mr Ross believes that such an approach would allow for the identification of the missile that brought down MH17, although with reports that rebels have cut large chunks out of the debris of MH17, that may prove a challenge. The post-crash fire would also make reconstruction difficult. Mr Ross said investigators would typically re-construct the aircraft in a controlled environment on a skeleton or jig, then try to match up the broken parts By locating the point of impact, it wiould allow them to identify the explosive residue that would have been left behind on the aircraft, he said. "This is very important as it will identify the precise missile."

Experts say that the priority is to secure the current crash site, as no thorough investigations can be carried out under the current conditions. "What has already happened since is absolutely criminal," said Mr Ross. "People should be charged with interference of a crime scene." For now at least, the black boxes are on their way to a controlled environment. On Tuesday night, the Malaysian Transport minister, Liow Tiong Lai, said that the black boxes had been obtained by an international investigation team after a deal was brokered with the Russian separatists. Loading

"The international investigation team, led by the Netherlands, has decided to pass the black boxes to the UK Air Accident Investigation Branch for forensic analysis," Mr Lai said. It is believed that once the boxes are received, information can be retrieved within 24 hours, depending on the condition of the recorders.