Wenatchee Helicopter Longline Accident (Washington) – August 11, 2004

Category: 
This Day in History
Page Last Modified / Reviewed: 
Aug 2021

 

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 the outcome. What are the conditions? What are you thinking? What are YOU doing?

Incident Summary:

Firefighters arrived to suppress two lightning fires near each other on the Wenatchee National Forest on August 10. The area was 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 was dispatched with a tandem sling load to deliver to the firefighters, one net for each fire.

A pink flagging "X" was placed near the stream at the southern end of a cut bank overlooking a sand bar. There was a tall snag located on the cut bank. The helicopter’s approach was from the southwest, perpendicular to the drainage. The snag was on the helicopter’s right side. One of the firefighters established communications with the pilot and said that if he didn’t like the established drop zone, it is okay to choose his own spot. The pilot acknowledged the firefighter and indicated that he would give their drop zone a try. The pilot was 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 began to lift to depart. Near the top of the snag, the pilot (sitting left seat) slowly turned the nose to the left. The tail of the helicopter struck the snag causing the helicopter to spin. It impacted the ground just upstream of the drop zone. The pilot was 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 at 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 pilot’s 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, what other hazards will you be looking out for as a lookout for a helicopter?

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.

E Helicopters delivering external loads via longline will be flying in the Height-Velocity Curve (aka, dead man’s curve, see NWCG Standards for Helicopter Operations [NSHO], PMS 510 which diminishes the pilot’s ability to land safely or recover from a loss of control or power.

  • Consider the pilot’s and your crew’s escape routes if the helicopter were to lose control or power. Where will the helicopter 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 to operate without hazards. For a helicopter, this is considered to be a minimum of 1½ 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 the IRPG for safety circle sizes. How big should the safety circle (zone) be for a Type 3 helicopter? Type 2? Type 1?

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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