Tail rotor strikes

May 25, 2012 by Tim McAdams

On March 16, 2003, a Bell 430 helicopter landed at an accident site at night. After the medical crew exited the helicopter the pilot decided to reposition the aircraft to face west for departure. During this repositioning the tail rotor hit a roadway sign and the aircraft became airborne to around five or six feet. The pilot lowered the collective and rolled the throttles to idle to stop the aircraft rotation. The helicopter touched down on the left rear skid first and came to rest 180 degrees from its initial heading. A post-accident examination revealed the tail rotor and gearbox had departed the helicopter.

Darkness certainly makes objects harder to see. However, two years prior to this accident, during daylight conditions, a Bell 222UT was damaged when its tail rotor impacted a barrel while landing on a paved traffic turn-around area. The pilot said that while hovering, he decided to reorient the aircraft to help with loading the patient. During the right pedal turn, the tail rotor struck a 55-gallon trash barrel. The helicopter yawed to the right and the pilot brought the throttles to flight idle and landed the helicopter. The tail boom was twisted, the tail rotor blades were damaged and the tail rotor gearbox was nearly separated from the airframe.

Not visible from the cockpit, a helicopter’s tail rotor is perhaps the most vulnerable component to striking objects in a hover. EMS pilots are especially at risk, as their job involves routinely landing in obstacle-rich environments. Although a tail rotor strike in a hover can cause serious damage, the potential for personal injury is low compared to what can happen in flight.

On May 17, 1999, a Bell OH-58A, operated by a public service agency on a photo flight, was destroyed on impact with the terrain and the private pilot and passenger sustained fatal injuries.

A witness reported that he saw a helicopter flying southbound at an altitude of approximately 350-400 ft. He saw what was possibly a large bird hit the rear rotor of the helicopter, after which two objects approximately the size of grapefruits fell to the ground. He said that the objects were falling slowly as though they were light, not fast like something heavy. The helicopter made three to four rotations during its descent.

The NTSB examined the tail assembly and found an elastic material with navy blue yarns wrapped around the tail rotor. The material, along with a sample of a navy blue warm-up jacket found along the reported flight path, was sent to the NTSB’s Materials Laboratory for examination. The color, size and texture of the navy-blue yarns in the elastic material were consistent with those found in the navy blue warm-up jacket.

The NTSB determined the probable cause of this accident was the tail rotor’s impact with the blue warm-up jacket and the subsequent overload of the tail rotor drive shaft. A contributing factor was the absence of the helicopter’s doors.

Removing a helicopter’s doors places the tail rotor at increased risk. In 1993, an R22 helicopter flying with its left door removed crashed after an aluminum kneeboard exited the helicopter and hit the tail rotor. The pilot and passenger were killed.

There have been numerous cases where objects have come out of the cabin or an unsecured baggage compartment and struck the tail rotor. In some cases the pilots have been able to enter autorotation or otherwise land with minor damage or injury. However, as with the two preceding accidents, the tail strike inflicted enough damage to cause the tail rotor assembly to come apart. In these cases, the resulting center of gravity shift made recovery impossible. The importance of protecting the tail rotor cannot be emphasized enough.

9 Responses to “Tail rotor strikes”

  1. Alan Barnes Says:

    Like a lot of the other accidents, those are ALL preventable, PILOT errors. It’s our responsibility to make sure that there is nothing loose that could fly out of the cockpit/cabin or off the helicopter itself. Doesn’t matter if it’s a kneeboard, sweatshirt, camera, loose fuel cap, cell phone, purse, etc.

  2. ed Says:

    Beirut 1969 60′s Bell 47g3b1 Alt about 2000 feet had just crossed ridge heading back down to the Beirut airport, airspeed about 80 mph a cardboard box was thrown from the rt seat, I felt it hit the T/R with a slight bump with no other effect. scared me beyond belief. Landed safely. The tab on the tail rotor was bent 180 degrees.
    End of story

  3. SpinDoctor Says:

    On a recent trip to Kauai, HI my sister and I sat up front in Hughes 500 for an aerial tour. The helo did not have doors and our pilot explained a week prior a passenger stuck their head too far out the door and ripped her headset off. The headset smacked the tail boom and left huge dent. The pilot felt had it hit the tail rotors h would not be alive. Scary stuff no doubt.

  4. Alan D. Resnicke Says:

    During a USAF career flying several models of helicopters in all kinds of environments, the only honest-to-goodness emergency I had was a main drive shaft failure on a UH-1N (Bell 212) that took out the tail rotor as well… on a moonless night… without NVGs… over the desert. I managed (by God’s miracles) to walk away with relatively minor injuries. Two others didn’t and a fourth barely survived. TAIL ROTORS ARE NOT TO BE FORGOTTEN OR IGNORED! Any helo pilot does so at his own peril…

  5. Jim Borger Says:

    It’s easy to forget how much helicopter is behind you, especially in the larger ships. The pilot sits well forward of the mast in a single rotor helicopter and all the pilot can see is the tip path, leading to an illusion that the part he can’t see is the same length as the part he can see.

    I witnessed a pilot dip his tal rotor in water, shearing the drive shaft. The first 90 degrees of turn seemed fairly slow but by the time he had spun 180 degrees he was really picking up speed. The pilot didn’t chop the throttle, he just slammed the collective full down. Luckily for him the water was only about a foot deep and the ground underneath was level so the aircraft stayed upright.

  6. Justin Says:

    So are there any rules of thumb or exercises anyone uses?

    One thing I did a couple times during my walk around is step off my available clearance from my seat to the back of the tailrotor, with that I step off that distance left, right and forward for cockpit visual references to give me an idea of what I have to work with prior to taking off (I know it’s hard to pick up visual references on the ramp, but I just do my best).
    I didn’t get that from a book or instructor, so that may be bogus info, but it’s what I use.

    Any others out there?

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