Bird strikes

July 24, 2012 by Tim McAdams

On March 5, 2009, an Agusta A109E helicopter hit a bird on a medical evacuation flight while approaching Gainesville, Florida. The pilot received minor injuries, while the crew and trauma patient were not injured. It was a night VFR flight from an automobile accident site in Trenton, Florida, to a hospital helipad.

According to the pilot, the incident occurred when the helicopter was about 3 minutes from landing at the hospital’s rooftop helipad. The helicopter was descending at 145 knots through 800 feet, when the windshield exploded and the pilot was pelted with Plexiglas and other debris. The master caution warning light started flashing, but the pilot had difficulty reading the caution warning panel as the left lens to his eyeglasses was missing. The pilot was eventually able to determine that SAS number 1 had been disengaged, and after resetting the switches the master caution light extinguished. The pilot also noted that the instrument panel lights were off on the pilot’s side, so he reached up to the overhead panel and turned the lights back on. He then noticed that several circuit breakers and switches were broken off, and that several other switches had been moved aft, to the off position. The entire overhead panel was covered in blood. The pilot said that despite the wind noise, the helicopter was still operating normally and he then landed at its home base without any further problems.

Examination of the helicopter revealed that a 2 to 3 pound duck hit the helicopter and came to rest inside the cabin at the feet of one of the medical crewmembers. The pilot also stated that aside from electrical control switches, the power control levers were also located on the overhead panel and that if they had been hit and moved aft there would have been a reduction of engine power.

Just two months prior to this incident, that is exactly what happened to a Sikorsky S-76C++ that was en route to an offshore oil platform with two pilots and seven passengers. Data from the helicopter’s flight data recorder indicated that the helicopter was established in cruise flight at 850 feet and 135 knots. About 7 minutes after departure, the cockpit voice recorder recorded a loud bang  followed by sounds consistent with rushing wind, a power reduction on both engines and a decay of main rotor rpm. Due to the sudden power loss, the helicopter departed controlled flight and descended rapidly into marshy terrain – only one person survived.

Examination of the wreckage revealed that both the left and right sections of the cast acrylic windshield were shattered. Feathers and other bird remains were collected from the canopy and windshield at the initial point of impact and from other locations on the exterior of the helicopter. Laboratory analysis identified the remains as coming from a female red-tailed hawk; the females of that species have an average weight of 2.4 pounds. Based on main rotor speed decay information provided by Sikorsky, the accident flight crew had, at most, about 6 seconds to react to the decaying rotor speed condition. Had they quickly recognized the cause of the power reduction and reacted very rapidly, they would likely have had enough time to restore power to the engines by moving the overhead engine control levers back into position. However, the flight crewmembers were likely disoriented from the bird strike and the rush of air through the fractured windshield; thus, they did not have time to identify the cause of the power reduction and take action.

As can be seen with these two accidents, bird strikes are disorienting and can require quick action to recover. One of the reasons helicopter pilots wear helmets is to protect their face and vision in case of a bird penetrating the windscreen.

4 Responses to “Bird strikes”

  1. Tonny Brohus Says:

    Hi Tim.
    Yes helmet is only one of the lessons here. As I read it , it looks good but very unpleassent with the swithes in the “deck”
    It too narrow and very diffcult to see and acknowledge in an emergency.

    Tonny

  2. Paul Mahon Says:

    800′ does not seem like a good altitude to cruise at. Is this common among medivac helicopters?

  3. Alan Barnes Says:

    Well, at some point, you have to go through 800′ when *descending* for a landing at a hospital helipad. They were hauling ass because they had an accident victim on board. But, no, they weren’t just cruising at 800′.

  4. Alex Kovnat Says:

    Three years ago there was an article in Vertiflite magazine (Formerly the quarterly, and now every-two-months publication of the American Helicopter Society) about a 94 GHz radar system called Sandblaster, which can image the ground through clouds of dust. Development of this system was initiated in response to the problem of rotor downwash kicking up clouds of dust when a helicopter carries out an off-airport landing for the purpose of carrying a wounded warrior to the nearest field hospital, in places like Afghanistan.

    So I wonder: If said radar were pointed ahead rather than downward, could it provide enough advance warning to enable a helicopter’s pilot in command to break right (or left) to avoid red-tailed hawks and other birds?

    For that matter one wonders how many bird strikes we may have, where the bird is actually a remotely piloted aircraft.

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