Helicopter crash during aerial ignition operations likely caused by loose fuel line

This article was first published at Fire Aviation

The National Transportation Safety Board has released their factual report on the crash of an AS350 helicopter that occurred March 27, 2019 during operations on a prescribed fire in Texas. Three people were on board, a pilot and two firefighters. The surviving firefighter and pilot were able to exit the helicopter; however, the second firefighter was partially ejected and sustained fatal injuries. The pilot suffered serious injuries and the surviving firefighter’s injuries were minor. The two injured personnel were transported to a hospital in stable condition after rescuers extracted them from the wreckage using jaws and air bags.

The firefighter killed was Daniel Laird, a Captain on the Tahoe Helitack crew in California. He left behind a wife and young daughter.

Mr. Laird was a U.S. Forest Service employee who, along with the other firefighter and the pilot, were on an aerial ignition mission on the Sam Houston National Forest. Their equipment was dropping plastic spheres that burst into flame after hitting the ground, helping to ignite the prescribed fire. The ship came to rest outside the active area of the prescribed fire and there was no additional fire caused by the crash.

The pilot and surviving crew member reported that after completing the application of plastic spheres they began flying back to the staging area when the engine lost total power.

Most NTSB accident reports are fairly straightforward, but this report, due to the way it is written, still leaves a small amount of doubt about the cause of the engine failure. However, signs point toward a loose fuel line.

“The fuel line between the firewall and hydro-mechanical unit (HMU) was loose and the required safety wire was not installed,” it says, and no other discrepancies were found. It does not say if the fuel line was loose enough to cause the engine to lose power.

From the NTSB report:

Federal Aviation Administration inspectors from the Houston Flight Standards District Office interviewed Mountain Air’s Director of Maintenance, who stated that on February 14, 2019, the USFS requested to validate the helicopter’s weight and balance. The helicopter was defueled, which involved disconnecting the main fuel line. After the weight and balance were verified, the main fuel line was reconnected. The director of maintenance asked another mechanic to verify that the fuel lines were reconnected, which was reportedly accomplished. The mechanic that accomplished the work informed the operator that he “was confident” that he torqued and secured the line. There was no other maintenance work which involved opening the fuel line after that day. On February 23, 2019, the helicopter’s engine would not light, and the engine’s igniters and/or igniter box was replaced. A maintenance records review found that the helicopter flew about 24.9 hours after the weight and balance was conducted on February 14, 2019.

On March 25, 2019, the pilot reported to management that the fuel pressure light had “flickered” during a flight “a few days before;” the pilot turned on the fuel boost pump, turned it off, and the light never reappeared. The pilot was informed to monitor the situation and report if it occurred again.

Following the accident, the digital engine control unit (DECU) was removed and sent to the manufacturer for data download. On April 11, 2019, the DECU was downloaded under the auspices of the FAA. The last recorded fault was a “P3 drift or engine flame out.”

The helicopter, N818MC, was owned Mountain Air Helicopters, Inc.  The company has five other helicopters and a Cessna 414A registered with the FAA.

In 2015 two were killed in Mississippi under similar circumstances on a prescribed fire when engine failure brought down a helicopter conducting aerial ignition operations. A third person suffered serious injuries.

Our take

Flying low and slow in a single-engine helicopter while igniting fire below the aircraft is obviously very, very dangerous. These three fatalities offer very compelling justification for using drones for aerial ignition instead of manned aircraft.

 

Thanks and a tip of the hat go out to Sean.