Age of Raisi's US-made helicopter and poor flying conditions may have led to Iran crash

Experts say flying helicopters through mountain ranges poses a number of risks

Rescuers work at the scene of the crash of a helicopter carrying Ebrahim Raisi in Varzaghan, in north-western Iran, on Monday. Moj News Agency via AP

Sunday’s fatal air crash involving Iran’s President Ebrahim Raisi, Foreign Minister Hossein Amirabdollahian and several other government officials could have been the result of dangerous flying conditions and the age of the US-made Bell 212 helicopter in which they were travelling.

There was heavy fog at the time the disaster occurred, according to Iran’s Interior Minister Ahmad Vahidi, who said the weather and mountainous terrain had made it difficult to locate the aircraft.

“If the weather is bad, the pilot has choices and if you cannot go above the weather, you should turn around or land. There really aren't any technical solutions here,” Simon Sparkes, a military helicopter test pilot and aviation expert, told The National.

It may emerge that the crash was caused by a mix of factors. The Bell 212 entered service in 1968 and the state bought a number of the helicopters in the 1970s when the Shah of Iran, a close US ally, ruled the country.

Iran continued to use many of its US aircraft after the 1979 Islamic Revolution that overthrew the monarchy, including advanced jet fighters, but faced difficulty obtaining spare parts due to American sanctions. Some of the aircraft purchased in the early 1970s, such as F-4 Phantom and F-14 fighter jets, are still in service.

Over the years, Iran’s fleet of US-made aircraft has slowly dwindled as it cannibalised parts from some to keep others operational.

Iran managed to obtain some spare parts for the Bell 212 from the US in 1986, during backchannel negotiations between Washington and Tehran over US hostages held by Iran-backed groups in Lebanon, but has also resorted to smuggling networks.

Bell denied supplying the parts but United Technologies Corp, a US defence contractor, later confirmed the shipment.

In 2011, Spanish authorities foiled a plot by Venezuela to sell Bell 212 spare parts, as well as complete aircraft, to Iran.

Sanctions on spare parts

The lack of spares to replace parts that suffer wear and tear threatens the safety of the aircraft. Iran’s air force has suffered numerous fatal accidents over the years involving US-made aircraft purchased in the Shah era.

In 2021, aviation authorities in Canada grounded Bell 212s after investigators looking into a fatal crash found that metal pins securing the main rotor blades had broken off during flight.

But old aircraft with good maintenance can keep flying for decades, with one notable example being the British Army’s Bravo November, a Chinook helicopter that remained in service – with numerous upgrades – from 1982 to 2022.

Iran has managed to reverse engineer some parts for US-made aircraft, so it is possible that helicopter carrying Mr Raisi was airworthy. However, there are high risks in flying in low visibility through mountainous terrain, where ice can build up on the airframe and high winds present additional strain.

Deadly mountain flying

The European Union Aviation Safety Agency said “being surrounded by high mountains and flying over deep valleys can disorientate a pilot” and navigating through such terrain “can be very mentally and physically tiring”.

According to the EU regulator, wind speed and direction can change suddenly and unpredictably in deep valleys, leading to “significant fluctuations in airspeed potentially leading, in extremes, to loss of control”.

Fog is particularly dangerous and was likely the leading cause of a 1994 helicopter crash in Scotland that killed 25 British intelligence operatives and four crew. Their Chinook flew into a hillside in near-zero visibility at the Mull of Kintyre.

“Inadvertent entry into cloud or fog is one of the biggest causes of helicopter accidents globally. It is a major focus of helicopter safety organisations. The problem isn't the certification of the helicopter or the pilots, it is the decisions made by the pilots when presented with the conditions,” Mr Sparkes said.

“In mountainous areas you must fly very high to be safe and it may be the weather or height of the mountains that was beyond the capability of the helicopter. In addition, without oxygen helicopters cannot fly over 10,000 feet due to issues with hypoxia,” he added, referring to low levels of oxygen, which can cause problems such as mental confusion.

“So pilots have choices to make. Sometimes they are difficult choices because the passengers don't want to be told they cannot travel because of the weather. Comparable accidents are probably too numerous to mention but there was a similar one in Kenya a few weeks ago,” he said, referring to a crash involving a Bell UH-1H Huey II helicopter that had been in operation for eight years.

The crash killed the head of Kenya's armed forces, Gen Francis Ogalla.