Archive for January, 2014

NTSB top 10

Sunday, January 19th, 2014

On January 16, 2014 the National Transportation Safety Board released its 2014 Most Wanted List, the top 10 advocacy and awareness priorities for the agency for the year. With the high accident rate in the helicopter industry, helicopter operations have been added to the list. According to the NTSB, between January 2003 and May 2013, 1,470 helicopter accidents have occurred, with 477 fatalities and 274 serious injuries.

The NTSB understands that helicopters are used for a range of operations, each of which presents unique challenges. For example, helicopter emergency medical services (HEMS) operators transport seriously ill patients and donor organs to emergency care facilities, often creating pressure to conduct these operations safely and quickly in various environmental conditions.  These include flying in marginal weather, at night, and landing at unfamiliar areas. Air tour operators and airborne law enforcement units face similar issues.

These and other operational issues have led to an unacceptably high number of helicopter accidents and the NTSB stated there is no simple solution for reducing helicopter accidents. However, they have recommended some safety improvements to mitigate risk. For instance, helicopter operators should develop and implement safety management systems that include sound risk management practices, particularly with regard to inspection and maintenance. Moreover, establishing best practices for both maintenance and flight personnel that include duty-time regulations that take into consideration factors like start time, workload, shift changes, circadian rhythms, adequate rest time, and other factors shown by recent research, scientific evidence, and current industry experience to affect crew alertness. Operators should also make sure that their pilots have access to training that includes scenarios such as inadvertent flight into instrument meteorological conditions and autorotation. Also noted as invaluable when an accident occurs is a crash-resistant flight recorder system that will assist investigators, regulatory agencies, and operators in identifying what went wrong and how to keep it from happening again.

Recent NTSB investigations of 3 accidents resulted in the issuance of 27 safety recommendations pertaining to issues that include risk management, pilot training, maintenance, and flight recorders.  These include a June 2009 accident near Santa Fe, New Mexico, involving a helicopter on a search and rescue mission, an August 2011 HEMS accident near Mosby, Missouri and a December 2011 air tour accident near Las Vegas, Nevada.

During the last 10 years the NTSB has issued over 100 safety recommendations. If the high helicopter accident rate continues, the FAA could step in and enact regulatory changes that would force changes on the entire industry.

 

High voltage

Thursday, January 9th, 2014

The flight characteristics of a helicopter make it suitable for a variety of interesting missions. One such job is the repair of live high voltage lines. The voltage on these lines is typically between one hundred thousand to one million volts.

A typical configuration uses a platform mounted to the helicopter’s skids with a wire attached to the helicopter’s airframe. The lineman sits on the edge of the platform as the pilot hovers the helicopter next to the line that needs repair. In some cases, the pilot must maneuver the lineman within several inches of the power line. Because this is considered an external load operation, the platform can be jettisoned. However, the lineman’s harness is attached to the helicopter.

The helicopter and the high voltage wire have different electrical potentials, so to equalize them a metal wand is brought close to the wire. When the wand is close enough the voltage jumps across causing an arc. Once the wand makes contact with the wire, a clamp is connected to the platform with a 5 or 6 foot cable that is attached to the helicopter insuring the voltage potential remains equal. The wand is then removed and the repairs can begin. In the event of an emergency the clamp will break away from the power line. The helicopter now has a high electrical potential and the pilot must be careful to not let the helicopter get to close to an object (a tree, for example) that will allow the voltage a path to ground. This will significantly increase the current flow through the helicopter causing high heat and serious damage to equipment and personnel.

Several accidents have happened from engine failures or the rotor system coming in contact with part of the power line infrastructure. One such accident happen in August of 2013 and according to the NTSB the helicopter was conducting an electrical power line construction operation with a lineman standing outside on the skid. The wire was temporarily suspended by a hoist and the lineman was inserting a fiber shoe to attach the wire to the arm of the tower. While the helicopter was hovering next to the wire at about 200 feet above ground level the hoist slipped and the wire fell onto the top of the helicopter’s skid. Control was briefly lost and four of the helicopter’s main rotor blades impacted the tower resulting in substantial damage to the main rotor blades. The pilot quickly regained control and made an emergency landing in tall corn about 200 feet from the accident location.  Fortunately, the pilot did an excellent job and no one was injured.

Even when everything goes right, high voltage power lines create a very strong electromagnetic field. This field produces an induced current that anyone close to the line will feel along their skin. As such, the pilot and lineman wear a special suit with a metal weave that allows the current to flow around the skin. Even with the suit, the sensation has been described as a feeling of pins and needles.