Bell 525 Prototype N525TA Fatal Flight Test Accident

Bell 525 Relentless Prototype N525TA Fatal Flight Test Accident

On 6 July 2016, Bell Helicopter lost the first prototype Bell 525 Relentless super-medium helicopter in a flight test accident in Texas.  Both test pilots on-board died were killed.

B525 FTV1 Accident Site (Credit: NBC)

B525 FTV1 Accident Site (Credit: NBC)

N525TA, Flight Test Vehicle (FTV) 1 was undertaking flight tests, accompanied by a chase helicopter (believed to have been Bell 427 N427F).  During test flights aircraft are monitored from one of three telemetry rooms housed at XworX.  Data is transmitted via a line of sight data link.

Bell 525 FTV1 During Earlier Flight Testing (Credit: Bell Helicopter)

Bell issued the following statement:

On July 6, 2016, a Bell 525 was involved in an accident while conducting developmental flight test operations south of our Xworx facility in Arlington, Texas. Unfortunately, the accident resulted in a loss of two crew members. This is a devastating day for Bell Helicopter. We are deeply saddened by the loss of our teammates and have reached out to their families to offer our support. Bell Helicopter representatives are onsite to assess the situation and provide any assistance to local, state, and federal authorities. At this time we ask for your understanding as we work through all of the details. We will continue to provide updates as more information becomes available.

B525 FTV1 Accident Site (Credit: BDO)

B525 FTV1 Accident Site (Credit: BDO)

TV news footage shows most of the wreckage in one location, where a post crash fire occurred.  Initial reports suggested the helicopter may have hit a power line but these appear to have been discounted.

However, the rear part of the tail boom and at least one main rotor blade appears to have fallen some distance away (some press reports suggest around 500m).

B525 FTV1 Tail Boom(Credit: NBC)

Rear Part of B525 FTV1 Tail Boom (Credit: NBC)

B525 FTV1 Tail Boom Debris (Credit: BDO)

B525 FTV1 Tail Boom Debris (Credit: BDO)

B525 FTV1 Main Rotor Blade Debris (Credit: NBC)

B525 FTV1 Main Rotor Blade Debris (Credit: NBC)

It has been reported that:

Flightradar24 records show the helicopter departing Arlington at 10:39 LT (15:39 UTC). It proceeded to the south were it flew pattern at altitudes between 2000 and 3000 feet. Last data point is at 1975 feet, at a speed of 199 kts*at 11:47 hours.

*Groundspeed.  Unconfirmed reports suggest a 20 kts headwind.

One of the test pilots has been identified as former US Marine Jason Grogan.

UPDATE 14 July 2016: The other has been identified asanother ex-USMC test pilot, Erik Boyce.

UPDATE 19 July 2016: It is reported by Jim McKenna on Aviation Today that:

The NTSB team is led by Investigator-in-Charge [IIC] John Lovell and includes [Chihoon] ‘Chich’ Shin, who worked for the U.S. Navy as a helicopter transmissions systems engineer before joining the safety board in 2012, and Van McKinney, a helicopter specialist for the board. Their work is being supported by investigators from the FAA, Bell and General Electric (which makes the 525’s two CT7-2F1 engines).

Investigators are assessing the data in the telemetry from the 525 for information about the accident flight and previous flight tests of the aircraft. The NTSB retrieved a flight test recorder from the wreckage and sent to its Washington recorder lab for readout. The safety board described the recorder as being in good condition. But the NTSB has declined to say whether it has retrieved any data from that recorder.
Investigators also have interviewed the chase pilots…
UPDATE 22 July 2016: Bell 525 flight tests remain suspended but parent company Textron‘s CEO Scott Donnelly says Textron “remains committed to the Bell 525 programme and we’ll work to ensure the aircraft will be a safe, reliable and high-performance helicopter”.
UPDATE 25 July 2016: In a further report Jim McKenna of Aviation Today quotes the NTSB IIC as saying the aircraft was on a test of One Engine Inoperative (OEI) handling approaching Vne (Velocity Never Exceed), when Main Rotor Speed dropped “significantly”, main rotor blades “move out of plane” and apparently striking both nose and tail boom.
UPDATE 4 August 2016: The NTSB issue a very brief preliminary report:
On July 6, 2016, about 1148 central daylight time, an experimental Bell 525 helicopter, N525TA, broke up inflight and impacted terrain near Italy, Texas. The two pilots onboard were fatally injured and the helicopter was destroyed. The flight originated from Arlington, Texas, as a developmental flight test and was conducted under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed at the time of the accident.
AINonline report a TV new helicopter pilot who flew over the accident site shortly after the accident saying he saw:
…dozens of pieces of main rotor blade scattered quite some distance from the main crash site. We saw one entire main rotor blade that had been mangled, but you could see the attaching hardware, and in other places we found two- and three-foot sections of main rotor blades. That [rotor blade] debris field was over a quarter mile [behind] the impact site[on both ides of the flightpath].
UPDATE 1 November 2016: Bell  has started final assembly of the first four production 525s.  Larry Thimmesch, vice-president of 525 sales and business development says “There is a tremendous amount of activity on the programme to get ready for [a resumption of test flying]“, though did not suggest when that might be.  Thimmesch also refrained from speculating on any revisions to the certification date, “having previously hinted that this may push into 2018″.
UPDATE 26 January 2017: It is reported that a flight test resumption is close.  CEO Scott Donnelly said:
We have a team working very hard to try to get that aircraft back into the flight-test program here in the early part of this year.  I think we’re getting close.
Last December, Bell applied for an extension to the 525 type certificate program because the initial application expired at the end of 2016. “That extension just took us through the end of 2018,” he said, “so somewhere in that timeframe is our objective to certify the aircraft, and we’ll come out with more information on that when we have that full flight test plan.”
Bell decided not to build another test aircraft after the accident, so four will be used to finish the flight test program.

Aircraft 003 is Bell’s third development 525, and in early February this helicopter was on its way to undergo pylon pull and control system stiffness or proof testing. The latter tests are done to calibrate aircraft systems to flight test instrumentation, he explained, “so when we see instrumentation through our telemetry lab we know exactly what’s happening on the aircraft.” The pull testing involves connecting devices to the blade attach fittings on the main rotor hub, and these also validate actuation against test instruments. Similar tests are underway on the tailrotor system.

Alongside physical testing of the 525s in preparation for return to flight, Bell engineers have been running ongoing tests in the Relentless Advanced Systems Integration Lab (RASIL) at the Bell XworX facility in Arlington, Texas.

Bell holds “around 80” letters of intent for the 525…

UPDATE 9 March 2017: 525 Probe Points to Vibration, Frequency Response in Fatal Crash

Three people briefed on the investigation by the National Transportation Safety Board have told R&WI data analysis of a recovered flight-test recorder, telemetry from the accident aircraft and simulations conducted by Bell for the safety board indicate the onset of the vibration and the subsequent response by the No. 1 Relentless prototype.

The three individuals said that Bell had not seen the vibration frequency resonance condition on any previous 525 flight.

Analysis of the aircraft’s cockpit voice recorder was not possible because the device was not powered during the July 6, 2016, test flight. One official said FAA guidance permits a CVR to be unpowered during a test flight.

In regard to its 525 investigation, the NTSB told R&WI Feb. 22 that “we hope to complete it this summer.”

UPDATE 5 June 2017: Bell looks to resume 525 flights as crash anniversary nears

Speaking on a pre-Paris air show media call, Bell chief executive Mitch Snyder said:

“We are preparing for flight and expect to be in the air in the near term,” he says, although declines to offer a specific timeline. Ground runs are also yet to take place, he admits.

Snyder says its “current plan” is to obtain US Federal Aviation Administration in late 2018, leading to first delivery early the following year.

UPDATE 7 July 2017: Flight testing resumes 366 days after the accident: Bell 525 Relentless resumes flight test program

Other Background on the B525 Program

FTV1s first flight took place at Amarillo, Texas on 1 July 2015.

At the time of the accident three prototypes had flown.

We have previously discussed the Fly by wire (FBW) system on the B525.

Prior Main Rotor Flying Test Bed Accident

This is not the first accident to hit the 525 programme.  On 7 August 2012 Bell 214ST N409SB, modified as a flying test bed for the B525 five bladed main rotor, was lost in Ellis County, Texas.  Both crew members survived.

B214ST Flying Test Bed N409SB Wreckage 7 Aug 2012 (Credit: CBSDFW)

In that case the US National Transportation Safety Board (NTSB) determined that the probable cause was:

Maintenance personnel’s failure to properly torque the retaining nut and install the cotter pin that secured the helicopter’s [original 2 bladed B214ST] tail rotor counterweight bellcrank.

Contributing to the accident was the lack of detailed maintenance records that documented previous maintenance actions.

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