Seconds before crashing into a Garden Route mountain, a Civil Aviation Authority (CAA) aircraft went into a mysterious dive, a preliminary accident report reveals.

The flight inspection aircraft, with three people aboard, lost 1,500ft in nine seconds, according to the flight data recorder.

Three seconds before it hit a mountainside near Friemersheim at 530km/h, the nose of the 33-year-old Cessna pitched up, but it was too late to avoid disaster.

The three crew members were killed on impact, wreckage was scattered over a 270m radius and the crash set mountain vegetation on fire.

The report said the crash of the CAA flight inspection aircraft was “not considered survivable because of the damage caused by impact forces”.

The three CAA staff who were killed were Captain Thabiso Collins Tolo, 49, first officer Tebogo Caroline Lekalakala, 33, and flight inspector Gugu Comfort Mnguni, 36.

It emerged from the report that the plane’s emergency locator transmitter did not send a signal after the crash and has not been found.

The Cessna did not have a cockpit voice recorder, meaning investigators were not able to determine if the plane’s terrain avoidance warning system alerted the crew that they were too near the mountain.

One of the recommendations in the preliminary report was a review of regulations to make voice recorders mandatory in all aircraft weighing 5,700kg or more, in line with international guidelines.

The 31-page document says the Cessna Citation and its crew began January 23 by taking off from Port Elizabeth on a flight path to George, hoping to conduct a calibration flight for the southern Cape airport’s very high frequency omni-directional range beacon.

Poor weather forced them to abandon the test so they landed, refuelled and at 8.42am took off at the start of a new attempt to test the beacon.

Four minutes later, they exited controlled airspace at 3,000ft and were advised by air traffic controllers to change their radio frequency.

At 8.50am, radar data showed the plane beginning a climb to 3,900ft, and a minute later “radar and radio contact were lost with the aircraft”.

The preliminary report described how air traffic controllers tried to contact the Cessna on three frequencies, and how an emergency was declared.

“The aircraft was located approximately an hour after going off radar by the [SA Air Force] search and rescue helicopter,” said the report, adding that the impact took place at 2,192ft.

“The emergency helicopter was dispatched to the site and arrived approximately 10 minutes after the wreckage of the aircraft was located.

“Due to inclement weather at the time, the search and rescue was suspended until the next day.”

The report also recaps three incidents involving the aircraft in the 10 months before the crash.

• On March 2 2019, one of its two turbo-fan engines did not respond to throttle movement due to a damaged cable, which was replaced;
• On November 7 2019, the plane was approaching Wonderboom airport in Pretoria when the cockpit filled with smoke; and
• The following day, when it was about to take off, the cockpit filled with smoke again. Take-off was abandoned and a leaking seal was found in an engine. “That resulted in the aircraft maintenance organisation replacing the defective engine,” said the report.

On Monday, transport minister Fikile Mbalula said an independent inquiry into the crash would be commissioned.

“I have deemed it appropriate and directed that an independent inquiry be undertaken, considering that the aircraft belonged to the CAA, and in order to be compliant with the legal principle of nemo iudex in re sua causa (no one is judge in his own cause)," said Mbalula.

"In the coming weeks, arrangements to appoint an independent authority to take the investigation to its logical conclusion will be expedited in line with the International Civil Aviation Organisation prescripts, and details thereof will be made public. We are committed to ensuring this investigation is finalised as quickly as possible.”