# NTSB CEN15LA069: Cirrus Design SR20, N407ND, Fort Collins, CO, December 5, 2014 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Limited investigation · Final report - Date: December 5, 2014, 14:28 local (21:28 UTC) - Place: Fort Collins, CO - Coordinates: 40.451946, -105.01139 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=40.4519&lon=-105.0114&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Defining event: [Approach-VFR pattern final: Loss of control in flight](https://openairdocs.org/ntsb-events/240) - Highest injury: Serious injuries - Injuries: 1 serious - Status: Completed, report November 5, 2015 - Report: Approved by Office Director - NTSB office: Central Region - Parties: Cirrus Aircraft, Continental Motors, Flight Standards District Office, Amsafe - NTSB case key (mKey): 90472 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN15LA069 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/90472/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=90472 - Page: https://openairdocs.org/ntsb/CEN15LA069 ## Probable cause The student pilot’s failure to comprehend the significance of the wake turbulence that a preceding helicopter would generate during departure, which resulted in a loss of airplane control during landing. Contributing to the accident was the lack of Federal Aviation Administration wake turbulence separation criteria for a small airplane following a helicopter. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Info processing/decision: understanding/comprehension](https://openairdocs.org/ntsb-findings/02041515): Personnel issues › Action/decision · Student/instructed pilot (probable cause); cases with it: [Cirrus Design SR20, 2 cases](https://openairdocs.org/ntsb-findings/02041515/cases.md?model=2130000), [All aircraft, 70 cases](https://openairdocs.org/ntsb-findings/02041515/cases.md) - [Performance/control parameters](https://openairdocs.org/ntsb-findings/01062000): Aircraft › Aircraft oper/perf/capability · Attain/maintain not possible (probable cause); cases with it: [Cirrus Design SR20, 6 cases](https://openairdocs.org/ntsb-findings/01062000/cases.md?model=2130000), [All aircraft, 1,269 cases](https://openairdocs.org/ntsb-findings/01062000/cases.md) - [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Student/instructed pilot (probable cause); cases with it: [Cirrus Design SR20, 47 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=2130000), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md) - [Turbulence: wake turbulence](https://openairdocs.org/ntsb-findings/03032025): Environmental issues › Conditions/weather/phenomena · Effect on operation (probable cause); cases with it: [Cirrus Design SR20, 1 case](https://openairdocs.org/ntsb-findings/03032025/cases.md?model=2130000), [All aircraft, 47 cases](https://openairdocs.org/ntsb-findings/03032025/cases.md) - [Policy/procedure: adequacy of policy/proc](https://openairdocs.org/ntsb-findings/04021015): Organizational issues › Management · FAA/Regulator (probable cause); cases with it: [Cirrus Design SR20, 1 case](https://openairdocs.org/ntsb-findings/04021015/cases.md?model=2130000), [All aircraft, 106 cases](https://openairdocs.org/ntsb-findings/04021015/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Approach-VFR pattern final: Loss of control in flight](https://openairdocs.org/ntsb-events/240) (defining event); cases with it: [Cirrus Design SR20, 36 cases](https://openairdocs.org/ntsb-events/240/sequence.md?model=2130000), [All aircraft, 5,002 cases](https://openairdocs.org/ntsb-events/240/sequence.md) ## Analysis The student pilot was conducting a solo flight in a Cirrus SR20 airplane at an uncontrolled airport. An airport video showed the student attempting to land on a runway about 30 seconds after the departure of a Sikorsky UH-60 helicopter. The student pilot reported that he was aware of the helicopter and that he attempted to land long. However, just before touchdown, the airplane encountered the wake turbulence of the helicopter and then entered an uncommanded steep left bank. The student attempted to counter the left bank and go around, but he was unable to maintain airplane control. The airplane subsequently impacted left of the runway and cartwheeled. Current Federal Aviation Administration pilot guidance, including the Airman's Information Manual and an advisory circular on aircraft wake turbulence, does not recommend separation criteria for a small airplane following a helicopter. It is likely that the student pilot did not comprehend the significance of the wake turbulence that the helicopter would generate during departure. ## Factual narrative FAA Flight Test Report In February 1996, the Federal Aviation Administration (FAA) Technical Center released a flight test report (DOT/FAA/CT-94/117) on the hazards of rotorcraft wake vortices in forward flight. The flight test utilized a laser Doppler velocimeter (LDV) to measure helicopter wake vortices. Four helicopters, with weights ranging from 7,600 to 70,000 pounds, were utilized as the wake vortex generating aircraft. The maximum duration for vortex life, as measured by the LDV, was 75 seconds for the UH-60. The FAA flight test report made the following conclusions: --Medium weight helicopters, such as the S-76A and UH-1….can leave active, potentially hazardous vortices for up to 90 seconds. Separations for small aircraft behind these rotorcraft should therefore be in the 90-second range. --Larger helicopters, such as the CH-47D and CH-53E ….were observed to have longer hazard times. A 120-second separation should be adequate for operations behind these rotorcraft. --Information on the wake vortex hazard behind these rotorcraft, including delineation by class, should be included in the Airman's Information Manual and the Wake Vortex Advisory Circular. The FAA flight test report is included in the public docket for this investigation. FAA Pilot guidance Current FAA airman information manual (AIM) and advisory circular (AC) 90-23G on aircraft wake turbulence do not recommend an in-trail distance or timing separation for an airplane following a helicopter. The AC contains a general wake turbulence statement: "pilots should avoid helicopter vortices since helicopter forward flight airspeeds are often very low, which generate strong wake turbulence." On December 5, 2014, about 1428 mountain standard time, a Cirrus SR20 airplane, N407ND, impacted terrain during approach at the Fort Collins-Loveland Municipal Airport (FNL), near Fort Collins, Colorado. The solo student pilot was seriously injured and the aircraft was substantially damaged. The aircraft was registered to and operated by Cirrus LLC under the provisions of 14 Code of Federal Regulations Part 91 as an instructional flight. Day visual meteorological conditions prevailed for the local flight, which departed without a flight plan. The student pilot stated that he entered the traffic pattern at FNL for a full stop landing on runway 33. He observed a Sikorsky UH-60 helicopter on downwind and delayed his turn to base until the helicopter was on final, abeam his position. While on final, the student pilot adjusted his aim point to land long, as he was concerned with wake turbulence and wanted to land beyond the helicopter's touchdown point. Just prior to landing, he encountered turbulent air, entered into an uncommanded steep left bank, and attempted to go around. The pilot was unable to maintain control and the airplane subsequently impacted terrain and cartwheeled, which resulted in damage to the fuselage and both wings. An airport surveillance camera at FNL captured the accidentairplane approaching the runway about 30 seconds in trail of the departing UH-60 helicopter. At 1435 the weather observation station at FNL reported the following conditions: wind 110 degrees at 3 knots, visibility 10 miles, clear sky, temperature 14 degrees C, dew point 4 degrees C, altimeter setting 30.22 inches of mercury. AmSafe airbag seatbelt assemblies were mounted in the two front crew seats of the accident aircraft. Neither of the two airbag seatbelts deployed as the airplane cartwheeled. On January 6, 2015, a wreckage review was conducted, which included examination of the crew seats and airbag seatbelt assemblies. The AmSafe inflatable restraint system is self-contained and not connected to aircraft electrical power. Each restraint system includes an inflatable restraint harness (which includes the harness/seatbelt, an airbag inserted in the seatbelt webbing and a Kevlar inflator hose), an inflator assembly (which includes a helium gas canister) and an inflator interface cable. The two front crew seat AmSafe inflatable restraints are controlled by an electronics module assembly (EMA). The EMA's dual crash sensors evaluate the acceleration and impact energy or crash pulse. The EMA's crash sensors only sense a longitudinal G input and require a continuous pulse of a minimum of 6+G's, which must load both sensors at the same time for 40-50 millseconds before the system will send a crash pulse signal to the inflator. A review of data downloaded from the Primary Flight Display (PFD) revealed that longitudinal Gs necessary to trigger the EMA crash sensors did not occur during the accident sequence. Examination of the right front crew seat revealed that the right airbag seatbelt's Kevlar inflator hose assembly was chafed. The inflator hose was chafed in a location about 6 to 7 inches from the hose fitting. The chafed area created a hole approximately 2 inches in length, 0.5 inches in width and completely through the Kevlar and rubber layers of the hose assembly. The chafed area was immediately forward of a storage pocket attached to the back of the right seat. The examination did not determine the source of the chafing. According to the AmSafe's Supplemental Instructions for Continued Airworthiness, a detailed visual inspection should be performed at least annually. The inspection requires a check of exposed hoses and cables for fraying and excessive wear of the hose and cable protective sleeving. Hose wear is acceptable as long as no holes are present. If any exposed hoses or cables show significant signs of fraying or excessive wear, such as holes, the assembly should be replaced. Examination also revealed that the electrical diagnostic check failed. The inflator interface cables had either loose and/or broken wires on the connectors for each of the two crew seats. These cables require inspection and testing annually. ## Aircraft - Registration: [N407ND](https://openairdocs.org/deregistered/N407ND-2015-08-25), registration cancelled 2015-08-25, S/N 1598, built 2005 (OpenAirDocs) - Reported make and model: CIRRUS DESIGN CORP SR20 - Registry model: [Cirrus Design SR20](https://openairdocs.org/model/cirrus-design-sr20) (registry code 2130000) (OpenAirDocs) - Registry engine: [Continental IO-360 series](https://openairdocs.org/engine/continental-io-360-series) (registry code 17025, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 1598 - Year built: 2005 - Airframe hours: 3740 - Engines: CONT MOTOR IO-360 SER 210 horsepower reciprocating - Damage: Substantial damage - Flight: Instructional, Part 91 - Operator: Cirrus LLC - Registered owner: Cirrus LLC - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, November 23, 2014, 7.5 hours before - Departed: FNL, Fort Collins, CO - Destination: FNL, Fort Collins, CO - Flight plan: VFR - Airport: FNL, Fort Collins-Loveland Muni, runway 33, 8,500 × 100 ft, asphalt - Equipment: Auto-pilot, Electronic multifunction display, Electronic primary flight display, Stall warning system ## Flight crew As NTSB recorded them. NTSB leaves out names. - Student pilot; age 47; injuries: serious; student; medical: class 2, without waivers/limitations; seat: left; restraint: 5-point; flight hours: 29 total, 27 in this make and model, 1 as pilot in command, 29 in the last 90 days, 4 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 110° at 3 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 57 °F, dew point 39 °F - Altimeter: 30.21 inHg - Observed at: KFNL ## 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 20141205021179A](https://openairdocs.org/incident/20141205021179A), Dec 5, 2014: Cirrus Design Corp SR20, Loveland, CO, Substantial damage. On December 05, 2014 at approximately 1435 hours mountain standard time (MST), N407ND, Cirrus SR20 aircraft , impacted terrain during approach at fort… ## Docket (9 files) The files NTSB released with the investigation on October 13, 2015, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=90472. 168 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 3.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=2368083&FileExtension=pdf&FileName=1%20-%20NTSB%206120.1%20-%20pilot%20accident%20report%20-%20redacted-Rel.pdf - Party member statements (item 2, PDF, 3 pages, 3.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=2368782&FileExtension=pdf&FileName=2%20-%20Party%20member%20statements%20-%20redacted-Rel.pdf - FAA rotorwash study (item 3, PDF, 95 pages, 7.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=2368861&FileExtension=pdf&FileName=3%20-%20FAA%20rotorwash%20study-Rel.pdf - FAA wake turbulence advisory circular (item 4, PDF, 24 pages, 1.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=2368870&FileExtension=pdf&FileName=4%20-%20FAA%20wake%20turbulence%20advisory%20circular-Rel.pdf - Cockpit displays - specialist's factual report (item 5, PDF, 9 pages, 710 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=2369348&FileExtension=pdf&FileName=5%20-%20Cockpit%20Displays%20-%20Specialist%27s%20Factual%20Report-Rel.pdf - Cockpit displays - attachment 1 (PFD data) (item 6, CSV, 434 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=2369573&FileExtension=csv&FileName=6%20-%20Cockpit%20Displays%20-%20Attachment%201%20(PFD%20data)-Rel.csv - Cockpit displays - attachment 2 (MFD data) (item 7, CSV, 8 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=2369519&FileExtension=csv&FileName=7%20-%20Cockpit%20Displays%20-%20Attachment%202%20(MFD%20data)-Rel.csv - Photo of airplane at accident site (item 8, PDF, 1 page, 1 photo, 150 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=2369162&FileExtension=pdf&FileName=Docket%20Photo-Rel.pdf - Airport surveillance video (item 9, MP4, 151 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=2390107&FileExtension=mp4&FileName=Airport%20video%20of%20wake%20turbulence-Rel.mp4 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.