# NTSB CEN21LA216: Aerospatiale AS350 B2 Ecureuil, N841BP, Yukon, OK, May 12, 2021 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: May 12, 2021, 15:30 local (20:30 UTC) - Place: Yukon, OK · On airport grounds - Coordinates: 35.491833, -97.821178 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=35.4918&lon=-97.8212&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering: Loss of control in flight](https://openairdocs.org/ntsb-events/240) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Central Region - Parties: BEA, Airbus Helicopters, Safran Helicopter Engines, FAA FSDO, CBP - NTSB case key (mKey): 103077 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN21LA216 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/103077/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=103077 - Page: https://openairdocs.org/ntsb/CEN21LA216 ## Probable cause The pilot receiving instruction’s untimely and unidentified inadvertent activation of the hydraulic cut-off switch, which turned off the hydraulic system while the helicopter was at slow airspeed followed by a rapid power increase, which resulted in a loss of control. Contributing was the pilot’s failure to relinquish control of the helicopter to the flight instructor when directed. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Pilot (probable cause); cases with it: [Aerospatiale AS350 B2 ECUREUIL, 2 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=8680813), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md) - [Performance/control parameters: yaw control](https://openairdocs.org/ntsb-findings/01062024): Aircraft › Aircraft oper/perf/capability · Attain/maintain not possible (probable cause); cases with it: [Aerospatiale AS350 B2 ECUREUIL, 1 case](https://openairdocs.org/ntsb-findings/01062024/cases.md?model=8680813), [All aircraft, 149 cases](https://openairdocs.org/ntsb-findings/01062024/cases.md) - [Hydraulic power system](https://openairdocs.org/ntsb-findings/01022900): Aircraft › Aircraft systems · Unintentional use/operation (probable cause); cases with it: [Aerospatiale AS350 B2 ECUREUIL, 1 case](https://openairdocs.org/ntsb-findings/01022900/cases.md?model=8680813), [All aircraft, 22 cases](https://openairdocs.org/ntsb-findings/01022900/cases.md) - [Info processing/decision: understanding/comprehension](https://openairdocs.org/ntsb-findings/02041515): Personnel issues › Action/decision · Pilot (probable cause); cases with it: [Aerospatiale AS350 B2 ECUREUIL, 1 case](https://openairdocs.org/ntsb-findings/02041515/cases.md?model=8680813), [All aircraft, 70 cases](https://openairdocs.org/ntsb-findings/02041515/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering: Loss of control in flight](https://openairdocs.org/ntsb-events/240) (defining event); cases with it: [Aerospatiale AS350 B2 ECUREUIL, 2 cases](https://openairdocs.org/ntsb-events/240/sequence.md?model=8680813), [All aircraft, 5,002 cases](https://openairdocs.org/ntsb-events/240/sequence.md) ## Analysis The pilot receiving instruction (pilot) and the flight instructor were conducting a training flight in the helicopter. They performed several simulated emergencies, each of which required the helicopter’s hydraulic system to be turned off and then turned back on at the conclusion of the procedure. The hydraulic system was turned off and on using the hydraulic cut-off switch, an unguarded push-button switch mounted on the end of the pilot’s collective stick. After completing the emergency procedures, the pilot performed four quick stop maneuvers. The flight instructor reported that on the last quick stop, the helicopter slowed normally but then started a left yaw about 25 ft above ground level. The pilot noted the left yaw and attempted to correct it, but his pedal inputs did not stop the yaw. As the pilot tightened his grip on the collective, the hydraulic system turned off, likely due to the pilot inadvertently pressing the hydraulic cut-off switch, and the left yaw rapidly increased to a left spin. According to the flight instructor, the control loads “instantly became excessive,” and he noticed the hydraulic light on the caution warning panel was illuminated. The pilot intentionally pressed the hydraulic cut-off switch a total of three times, but hydraulic pressure was never restored. The flight instructor told the pilot that he was taking control of the helicopter. However, the pilot did not relinquish control. The flight instructor attempted to regain control of the helicopter but was unable to overcome the high control loads. The helicopter continued to spin, impacted the ground, rolled over, and came to rest on its right side. A postimpact fire consumed most of the helicopter. Although examination of the helicopter was limited due to fire damage, no preimpact abnormalities were identified with helicopter’s airframe and engine. The US Customs and Border Protection Air and Marine Operations Division reported that the agency’s selection process for the Air Interdiction Agent Program failed to properly identify that the pilot was not qualified for the program. Because the pilot did not have the qualifications and experience required for the Air Interdiction Agent Program, he did not have the prerequisite skill necessary to critically assess the situation given by the flight instructor. This resulted in the pilot applying improper corrective actions and failing to relinquish control of the helicopter to the flight instructor when directed, which contributed the accident. ## Factual narrative On May 12, 2021, about 1530 central daylight time, an Aerospatiale (Airbus) AS350 B2 helicopter, N841BP, was destroyed when it was involved in an accident near Yukon, Oklahoma. The pilot receiving instruction and the flight instructor were not injured. The helicopter was operated as a 14 CFR Part 91 public aircraft instructional flight. According to the flight crew, the pilot receiving instruction (pilot) was enrolled in the US Customs and Border Protection Initial Pilot Certification course for the AS350 B2. The flight departed the Will Rogers International Airport (KOKC) and proceeded to the Clarence Page Municipal Airport (KRCE) to conduct training maneuvers. After arrival at KRCE, the flight crew conducted several approaches to the airport including confined area and pinnacle approaches. They then conducted several simulated emergencies, each of which required the helicopter’s hydraulic system to be turned off and then turned back on at the conclusion of the procedure. The hydraulic system was turned off and on using the hydraulic cut-off switch, an unguarded push-button switch mounted on the end of the pilot’s collective stick. After the simulated emergencies, the flight crew proceeded to conduct a series of “quick stops.” After the third quick stop, the pilot heard a radio call indicating an airplane was on final approach to land on the runway they were using, and the flight instructor indicated that they would clear the runway. The pilot added that he completed a final quick stop and immediately entered a climbing left turn. The pilot stated that in the turn, he noticed the helicopter yawing left, and his pedal inputs were unable to correct the yaw. When the pilot adjusted his grip on the collective, he felt the hydraulic cut-off button with his thumb as he prepared to reduce collective. As he tightened his grip on the collective, “the hydraulics came offline aggravating the left yaw into a hard left spin.” The controls were stiff, and the flight instructor told him to turn the hydraulics back on. The pilot “intentionally pressed the [hydraulic cut-off] button but felt no effect.” He pressed the button a second time, but the hydraulic light on the caution warning panel remained illuminated, so he pressed the button a third time. The flight instructor reported that on the last quick stop, the helicopter slowed normally but then started a left yaw about 25 ft above ground level. After the helicopter yawed about 30° left of centerline, he pushed forward on the cyclic to gain airspeed. The flight instructor stated that “as the aircraft was recovering, the control loads instantly became excessive,” and he noticed the hydraulic light on the caution warning panel was illuminated. He told the pilot to turn on the hydraulics; however, the hydraulic pressure was never restored. The flight instructor told the pilot that he was taking control of the helicopter. However, the pilot did not relinquish control. The flight instructor attempted to regaincontrol of the helicopter but was unable to overcome the high control loads. The helicopter continued to spin, impacted the ground in a nose-down attitude, rolled over, and came to rest on its right side. Both occupants were able to exit the helicopter before a postimpact fire consumed most of the helicopter. Examination of the helicopter was limited by the postimpact fire; however, no preimpact abnormalities were identified with helicopter’s airframe and engine. The US Customs and Border Protection Air and Marine Operations Division reported that the agency’s selection process for the Air Interdiction Agent Program failed to properly identify that the pilot was not qualified for the program. ## Aircraft - Registration: [N841BP](https://openairdocs.org/deregistered/N841BP-2022-06-04), registration cancelled 2022-06-04, S/N 2036, built 1987 (OpenAirDocs) - Reported make and model: AEROSPATIALE AS350 B2 ECUREUIL - Registry model: [Aerospatiale AS350 B2 ECUREUIL](https://openairdocs.org/model/aerospatiale-as350-b2-ecureuil) (registry code 8680813) (OpenAirDocs) - Registry engine: [Turbomeca ARRIEL-1D1](https://openairdocs.org/engine/turbomeca-arriel-1d1) (registry code 60053, turbo-shaft) (OpenAirDocs) - Category: Helicopter - Serial number: 2036 - Year built: 1987 - Airframe hours: 15261.6 - Engines: Turbomeca Arriel 1D1 turbo shaft - Damage: Destroyed - Fire: On-Ground - Flight: Instructional, Public use - Operator: Customs Border and Protection - Registered owner: US Dept of Homeland Security - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, May 7, 2021 - Departed: KOKC, Oklahoma City, OK - Destination: Same as departure - Airport: KRCE, Clarence Page Municipal - Equipment: ADS-B, Angle of attack indicator ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 45; injuries: none; commercial; airplane ratings: single-engine land; instrument ratings: helicopter; medical: class 2, with waivers/limitations; last flight review June 29, 2020; seat: right; flight hours: 1,200 total, 620 in this make and model, 474 as pilot in command, 12 in the last 90 days, 12 in the last 30 days - Flight instructor; age 40; injuries: none; commercial; instrument ratings: helicopter; medical: class 2, with waivers/limitations; last flight review December 17, 2020; seat: left; restraint: 4-point; flight hours: 6,000 total, 1,000 in this make and model, 5,500 as pilot in command, 68 in the last 90 days, 23 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 20° at 9 knots - Visibility: 10 statute miles - Lowest ceiling: 6,000 ft overcast - Temperature: 64 °F, dew point 50 °F - Altimeter: 30.29 inHg - Observed at: KRCE ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 20210512008989A](https://openairdocs.org/incident/20210512008989A), May 12, 2021: Aerospatiale AS350 B2 ECUREUIL, Yukon, OK, Destroyed. At approximately 1450 the aircraft departed for will rogers airport (kokc) for a series of training maneuvers at/near e. Page municipal airport (krce). Arrived… ## Docket (11 files) The files NTSB released with the investigation on January 4, 2023, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=103077. 12.6 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 4.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13135104&FileExtension=pdf&FileName=NTSB%206120_Redacted-Rel.pdf - Flight instructor statement (item 2, PDF, 3 pages, 1.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13135876&FileExtension=pdf&FileName=CFI%20Statment%20Redacted-Rel.pdf - Pilot statement (item 3, PDF, 3 pages, 822 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13135601&FileExtension=pdf&FileName=Pilot%20statement%20%20Redacted-Rel.pdf - Photos (item 4, PDF, 3 pages, 4.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12789574&FileExtension=pdf&FileName=Photo%201-Rel.pdf - Statement of party representatives to NTSB investigation (item 5, PDF, 8 pages, 258 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12789183&FileExtension=pdf&FileName=AMO%20Signed%20NTSB%20Party%20Form_Redacted-Rel.pdf - Accredited representative (item 6, PDF, 1 page, 634 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12789410&FileExtension=pdf&FileName=Parties_Redacted-Rel.pdf - Exam summary (field) (item 7, PDF, 1 page, 201 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13018408&FileExtension=pdf&FileName=Examination%20Summary%20--Rel.pdf - Release of aircraft wreckage, NTSB form 6120.15 (item 8, PDF, 1 page, 277 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12789193&FileExtension=pdf&FileName=Wreckage%20release_Redacted-Rel.pdf - Excerpt from flight manual (item 9, PDF, 1 page, 52 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=13128856&FileExtension=pdf&FileName=Page%20AS350%20B2%20Flight%20Manual-Rel.pdf - E-mail, customs and border protection (item 10, PDF, 2 pages, 164 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14898995&FileExtension=pdf&FileName=RE_%20NTSB%20CEN21LA216%20Report%20Review_Redacted-Rel.pdf - Customs and border protection additions to the factual report (item 11, PDF, 2 pages, 77 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=14898959&FileExtension=pdf&FileName=CEN21LA216%20Yukon%20Oklahoma%20Factual%20Narrative%20Word%20Document,%20CBP%20Changes-Rel.pdf From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.