MedFlight crash underscores value of helicopter TAWS

Aviation International News » June 2008
June 9, 2008, 6:49 AM

On May 10 at 10:40 p.m. local time, a Eurocopter EC 135T2+ crashed in an area of rapidly rising terrain six minutes after taking off from La Crosse, Wis. Municipal Airport. The three occupants, an instrument- rated pilot and the two-man medical crew, aboard the VFR Part 91 positioning flight were killed. It was the first crash in the 23-year history of the program. The accident resembles several others cited by the NTSB last December when it called for mandatory equipment upgrades on all EMS helicopters.

N135UW (a 2007 model) was operated by Air Methods for UW-MedFlight and was returning to the University of Wisconsin–Madison University Hospital.

Air Methods CEO Aaron Todd told AIN that the helicopter’s panel included a radar altimeter, weather radar, XM satellite weather, a satellite tracking system, dual Garmin GNS 430 GPS/coms, and a single-pilot IFR cockpit; however, the helicopter was not equipped with TAWS or night vision goggles (NVGs). The helicopter was slated to have those items installed later this year as equipment became available.

The NTSB has not yet determined a probable cause of the crash, but the circumstances suggest that the pilot could have benefited from having TAWS and/or NVGs on board. Weather at the time of the crash was reported as quickly deteriorating with four statute miles visibility in rain, calm wind, 3,500 feet broken to overcast ceiling and a two-degree temperature-dew point spread.

The helicopter hit a heavily wooded ridgeline approximately four miles southeast of the airport after taking on fuel there, in an area of rugged bluffs near several radio towers in the Town of Medary.

According to an NTSB spokesman, the wreckage was scattered over a tenth of a mile. The crash was detected by the satellite tracking system and a ground search was initiated by 11 p.m., but the wreckage was not located for nine hours due to rugged terrain and weather conditions that prevented an aerial search and rendered thermal-imaging FLIR devices ineffective.

The circumstances of the MedFlight crash are reminiscent of those the Safety Board highlighted in a December 2007 NTSB safety recommendation that urged that radar altimeters be installed in all EMS helicopters and be part of the minimum equipment list (MEL) of all EMS aircraft.

In its report, the Safety Board stated, “Helicopter emergency medical services (HEMS) flights typically operate under visual flight rules and at low altitudes. When flying during night conditions, HEMS pilots must be especially diligent in avoiding controlled flight into terrain (CFIT) because a lack of visual ground references during night flight can render a pilot susceptible to visual illusions and other conditions that can make it difficult to judge the helicopter’s attitude and actual height above the terrain.”

One year earlier, in 2006, the Board issued a “Special Investigation Report on emergency medical services (EMS) operations” that recommended the installation of TAWS in all EMS helicopters.

The recommendations came in the wake of 89 EMS helicopter crashes between 1998 and 2005 that killed 75; 47 of these crashes were at night and 56 percent of all fatal EMS crashes were at night, according to a Johns Hopkins University study.

In its 2007 report, the NTSB examined two EMS crashes as illustrations for its recommendations. One involved the night VFR crash of an EC 135 into the Potomac River near Oxon Hill, Md., in January 2005. The pilot and the flight paramedic were killed; the flight nurse was seriously injured. After being issued a traffic advisory, the pilot entered a gradual descending right turn until the helicopter hit the water.

The second crash cited occurred in April 2004 when an Air Evac Life Team Bell 206L-1 crashed into upsloping terrain in Boonville, Ind., during night VMC, killing the patient and seriously injuring the pilot and medical crew. The altimeter was set to the wrong barometric pressure, yielding an error that made the altimeter indicate 310 feet higher than actual altitude, and the radar altimeter aboard had a history of erratic function, according to another pilot who had previously flown the helicopter.

The NTSB concluded, “Radar altimeters are needed to maintain ground clearance when visual references to terrain are limited during night conditions.…a functioning radar altimeter provides a pilot with constant information about the helicopter’s height above ground level (agl) and has an alerter function that can visually and/or aurally alert a pilot when the helicopter approaches and then descends below a preselected altitude.”

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