Wenatchee Helicopter Longline Accident - August 11

Category: 
This Day in History
Page Last Modified / Reviewed: 
Aug 2019

 

This Day in History is a brief summary of a powerful learning opportunity and is not intended to second guess or be judgmental of decisions and actions. Put yourself in the following situation as if you do not know what the outcome will be. What are the conditions? What are you thinking? What are YOU doing?

Incident Summary:

August 10th 2004, firefighters arrive to suppress two lightning fires nearby each other on the Wenatchee National Forest. The area is heavily wooded and mountainous. That evening the firefighters request supplies be flown into a drop zone they have established in a creek bed. The firefighters estimate the trees in the drainage to be an average of 80 feet tall with some 120 foot tall trees near the drop zone. A 150 foot longline is requested. The next morning, a Bell 205 A1 helicopter is dispatched with a tandem sling load to deliver to the firefighters, one net for each fire.

A pink flagging “X” is placed near the stream on a sand bar at the southern end of a cut bank overlooking the sand bar. There is a tall snag located on the cut bank. The helicopters approach is from the SW perpendicular to the drainage and the snag is on the helicopters right side. One of the firefighters establishes communications with the pilot and says that if he doesn’t like the drop zone they chose that it is okay to choose his own spot. The pilot acknowledges the firefighter and indicates that he will give it a try. The pilot is not told about the snag. The pilot places both nets on the drop zone; one of the firefighters unhooks their net and re-hooks the load for the other crew. The helicopter begins to lift to depart. Near the top of the snag, the pilot (sitting left seat) slowly turns the nose to the left. The tail of the helicopter strikes the snag causing the helicopter to spin, and impacts the ground just upstream of the drop zone. The pilot is killed.


Size up - The snag was cut down and measured at 169’5” tall. Adding the height of the cut bank to the height of the snag, the tree was 172’11” above the drop zone surface. The longline was measured and was 160 feet long. The strike marks were found 15’4” down from the top of the snag.

  • When you and your crew are sizing up a potential cargo drop zone, what are some methods to estimate tree and obstacle height?
     

L - A pilots’ ability to see their surroundings is fairly limited, especially when looking down at an external load. The ability of the ground personnel to see the helicopter in relation to the surrounding hazards can often be better. When a helicopter pilot is working with an external load, consider yourself and your crew to be a “Lookout” for that pilot just as you would other members of your crew. Watch the main rotor and tail rotor, not just the load. When any hazard encroaches on the safety circle (zone) communicate it immediately. Never assume that the pilot sees it or that someone else will say something. IF YOU SEE SOMETHING…SAY SOMETHING.

  • In addition to trees and snags, as a lookout for a helicopter, what other hazards will you be looking out for?

C -You and your crew must be able to communicate with the pilot by radio. Before the helicopter arrives at your site, brief the pilot on hazards including trees and their estimated height. It is generally considered better to over-estimate the height than to under-estimate it.

  • When communicating to a pilot, how do you refer to the direction of a hazard in reference to the helicopter? (IRPG cover)

E - Helicopters delivering external loads via longline will be flying in the Height-Velocity Curve (aka “dead man’s curve”, page 11-1 IHOG) which diminishes the pilot’s ability to land safely or recover from a loss of control or power.

  • Consider the pilots and your crews’ escape routes if the helicopter were to lose control or power. Where will it go? Where will you go?

S - Consider the safety zone and a safety circle to be very similar places. It needs to be big enough for the helicopter to operate without hazards and is considered to be a minimum of 1 ½ times the rotor diameter. The rotor diameter of this helicopter was 48 feet. The snag was 36 feet from the drop zone marker.

  • Refer to page 49 in your IRPG for safety circle sizes. How big should the safety circle (zone) be for a Type III? Type II? Type I?

 

Additional Resources

Incident Management Situation Report (IMSR)
Incident Response Pocket Guide (IRPG), PMS 461
NWCG Standards for Helicopter Operations, PMS 510
RT-130, Wildland Fire Safety Training Annual Refresher (WFSTAR)
Interagency Standards for Fire and Fire Aviation Operations (Red Book)
Wildland Fire Lessons Learned Center

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