CEN13FA331

The pilot receiving instruction's failure to maintain adequate airspeed during a simulated hydraulics failure training maneuver, which resulted in his loss of control of the helicopter and its subsequent impact with terrain, and the flight instructor's delayed and inadequate remedial action.

The instructor pilot reported that he and the pilot receiving instruction departed on a local night instructional flight to perform a simulated hydraulics failure maneuver in the helicopter. On shallow approach to the runway with hydraulic power off, the instructor told the pilot to fly the helicopter to a designated point on the airfield, at which point, the pilot was to perform a go-around. As the helicopter was "getting a little slow," the instructor again mentioned to the pilot that he needed to go around. As the pilot increased power, the helicopter's nose started rising, and the instructor told the pilot to get the nose down to increase the airspeed. The pilot remarked that it was hard to apply right pedal, so the instructor also manipulated the controls to assist him. At this point, the helicopter had started to turn left, and the instructor applied forward cyclic. The helicopter pitched nose down, and the instructor thought he might have overcompensated. The instructor felt the pilot applying aft cyclic, and the helicopter again pitched nose down, so he made an additional control input to level the helicopter. However, the helicopter started spinning left, developed extreme pitch attitude changes, and was not climbing. The instructor again attempted to level the helicopter, reduced the power to slow the rotation, and reapplied power to cushion the landing. The helicopter subsequently impacted terrain and rolled onto its right side. Flight control continuity was established, and all observed separations were consistent with overload. No evidence of any preexisting failures of the helicopter's airframe or engine were found that would have precluded operational control of the helicopter. The recorded vehicle monitor data were consistent with impact and rollover occurrences, and no preimpact failures or overlimit events were recorded. The flight manual notes that the hydraulic failure safety speed is from 40 to 60 knots and contains a caution to not attempt hover flight or any low-speed maneuver without hydraulic pressure assistance. The caution noted that the intensity and direction of the control feedback forces will change rapidly, which will result in excessive pilot workload, poor aircraft control, and possible loss of control. It is likely that the pilot receiving instruction failed to maintain adequate airspeed during the simulated hydraulics failure maneuver, which resulted in his loss of control of the helicopter and its subsequent impact with terrain.

Air Methods is a commercial on-demand air taxi operator specializing in helicopter emergency medical services (HEMS). The company was established in 1980 in Colorado, and currently operates in 42 states. Air Methods received its Title 14 Code of Federal Regulations (CFR) Part 135 Operating Certificate, number QMLA253U, on March 1, 1992. In accordance with 14 CFR Part 135.21, Air Methods keeps current a General Operating Manual (GOM), which identifies management policies and responsibilities, training/currency policies, and the procedures under which flights are conducted. Chapter 3 of the Air Methods Pilot Training Program revision 9 dated June 07, 2013 "Initial Equipment and Transition Training" addresses the recurrent training curriculum. The curriculum consists of 4 hours of ground training each for IFR and VFR operations, and recommends a minimum of 4 hours of flight training for IFR and 2 hours for VFR operations. However, an instructor can recommend a flight test before the completion of the recommended hours. The flight training is broken down into four modules. Each module addresses various normal, instrument, emergency procedures, and the fourth module addresses night operations. Autorotations are practiced in module 2, and hovering autorotations are practiced in module 3. Each module appears to be organized around 1 hour of flight time. Annex 1 of the Pilot Training Program revision 8 dated January 31, 2012 delineates in detail all flight terms, definitions, and maneuver procedures for the Eurocopter AS350 helicopter. Sections 1-33 and 1-34 describe the procedures to practice simulated engine failure resulting in straight-in and turning autorotations. All practice autorotations are to conclude with a power recovery terminating in a 3- to 5-foot hover. A flight proficiency check (FAR 135.293 check) is preceded by a training flight. The training flight consists of standard commercial maneuvers, normal, shallow, and steep approaches, sloped landings, engine failures, hydraulics off flight, basic instruments, and an instrument approach. Three to five practice autorotations are performed towards the end of the training flight and terminate in a 3- to 5-foot hover power recovery. If a pilot is not performing to standards, the check airman has the authority to provide extra training. Additionally, if a pilot feels they need extra training they can request additional training, which is coordinated through the appropriate chain of command and approved by the Chief Pilot or Aviation Training Manager. This policy is set forth in section 2.4 of the Air Methods General Operations Manual. Air Methods has two dedicated training helicopters that are moved from base to base to conduct training and check flights. A training flight usually lasts 1-1.5 hours, and a check flight is usually 1 hour. On occasion, due to scheduling conflicts, the dedicated training helicopter is not available and the base's assigned helicopter is reconfigured to conduct training and check flights. In addition to dedicated training aircraft, Air Methods utilizes mobile and permanent advance aircraft training devices (AATD) as well as full-motion simulators in their training programs. The helicopter was equipped with a vehicle engine multifunction display (VEMD), part number B19030MC05, serial number 1177, which is a dual screen display that provided vehicle and engine information to the pilot during flight (known as flight mode). The VEMD also has a maintenance mode, which stored non-volatile data for specified vehicle and engine exceedances and/or overlimits and VEMD-system-related hardware or communication failures. The VEMD also recorded and stored flight reports, which can be found in the maintenance pages. A flight report begins when aircraft electrical power is applied and engine generator speed (NG) reaches 60 percent. The flight report ends when the NG decreases below 50 percent with aircraft electrical power still applied. During a normal landing and shutdown, the VEMD will display the flight report for the most recent flight when NG drops below 10 percent and main rotor rpm (NR) decreases below 70 rpm. The helicopter's engine was equipped with a single-channel digital engine control (DECU), part number 70BMB01020, serial number 1515, which monitors and controls engine operations. It incorporated a redundant electrical supply from the engine alternator and aircraft battery. The DECU was programmable and interfaced between the aircraft and system components. It was designed to capture and retain events that exceed certain pre-set parameters and store this data in its non-volatile memory. GPM, located approximately four miles southwest of Grand Prairie, Texas, was a publicly owned, towered airport, which was owned by the city of Grand Prairie. GPM's field elevation was 588 feet above mean sea level. GPM was serviced by runway 17/35, which was a 4,001 feet, by 75 feet, concrete runway. Runway 17 was marked as a non-precision approach runway and it had medium intensity runway edge lights. It was serviced by a four-box visual approach slope indicator system. A 25-foot tall tree, 824 feet from the runway's threshold and 145 feet right of its centerline, was listed as an obstruction. The VEMD initial examination was conducted on August 19, 2013, at American Eurocopter facilities near Grand Prairie, Texas, under FAA supervision. A follow-up examination under FAA supervision was conducted on August 20, 2013. The VEMD data showed the accident flight was about 20 minutes long. There were three failures recorded near the end of the data and two overlimits events. The first failure recorded was test reference code 122, which corresponds to a collective pitch potentiometer failure. The parameters associated with this failure are consistent with the parameters resulting from a main rotor blade ground impact. This failure was followed shortly afterwards by the fuel gage failures, which is consistent with fuel migrating away from its sensor during a helicopter rollover. The VEMD did not record any pre-impact failures or overlimits events. The DECU was examined and its data was downloaded by the engine manufacturer under FAA supervision on August 19, 2013, at Turbomeca facilities near Grand Prairie, Texas. Data from its non-volatile memory was recovered successfully when the unit was connected to a test bench. The DECU begins recording time as soon as the aircraft 28 volts is applied and since the VEMD does not start recording until the engine is started and reaches 60 percent Ng, it is probable for the DECU to show more time than the VEMD for a given flight. The first faults recorded by the DECU during the accident flight were 24 minutes 12 seconds after power up. The significant fault at that time was a collective pitch measurement that exceeded the applicable software parameters. The next and last faults recorded were 24 minutes 52 seconds after power up. The faults were recorded as raw torque measurement that exceeded the applicable software parameters and collective pitch measurement that exceeded the applicable software parameters. A real time check of the DECU was then performed and the DECU was found to be operating normally. The yaw load compensator was shipped to its manufacturer, Parker-Olaer, in Colombes, France, for examination under the supervision of the French aircraft accident investigation authority, the Bureau Enquetes-Accidents. The examination revealed that the accumulator was in good external condition and it held the precharge pressure. The core valve and bladder did not leak when it was pressurized during hydraulic testing. The core valve was in good condition. The compensator's bladder was in operational condition. The inspection further showed that witness marks were present, which were consistent with an accumulator operating at an undetermined time with very low, or nil precharge pressure. There was no other evidence found of any pre-exis