# NTSB CEN13LA225: Atkins ACRO-SPORT I, N5897, Midland, LA, April 12, 2013

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Limited investigation · Final report
- Date: April 12, 2013, 15:00 local (20:00 UTC)
- Place: Midland, LA
- Coordinates: 30.150278, -92.483886 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=30.1503&lon=-92.4839&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Defining event: [Maneuvering-aerobatics: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333)
- Highest injury: Minor injuries
- Injuries: 1 minor
- Status: Completed, report December 15, 2014
- Report: Approved by Office Director
- NTSB office: Central Region
- Parties: Federal Aviation Administration
- NTSB case key (mKey): 86639
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN13LA225
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/86639/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=86639
- Page: https://openairdocs.org/ntsb/CEN13LA225

## Probable cause

The failure of the left elevator torque tube due to poor quality welds by the manufacturer, which resulted in the loss of pitch control.

## Findings

NTSB's coded findings; those marked are part of the probable cause.

- [Flight control system: elevator control system](https://openairdocs.org/ntsb-findings/01022730): Aircraft › Aircraft systems · Failure (probable cause); cases with it: [Atkins ACRO-SPORT, 1 case](https://openairdocs.org/ntsb-findings/01022730/cases.md?model=0564609), [All aircraft, 74 cases](https://openairdocs.org/ntsb-findings/01022730/cases.md)
- [Manufacture/production: equipment manufacture](https://openairdocs.org/ntsb-findings/04013010): Organizational issues › Development · Manufacturer (probable cause); cases with it: [Atkins ACRO-SPORT, 1 case](https://openairdocs.org/ntsb-findings/04013010/cases.md?model=0564609), [All aircraft, 36 cases](https://openairdocs.org/ntsb-findings/04013010/cases.md)

## Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event best describes what happened.

- [Maneuvering-aerobatics: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333) (defining event); cases with it: [Atkins ACRO-SPORT, 1 case](https://openairdocs.org/ntsb-events/333/sequence.md?model=0564609), [All aircraft, 410 cases](https://openairdocs.org/ntsb-events/333/sequence.md)

## Analysis

The pilot reported that, while practicing aerobatics, he pulled the control stick aft and that something in the elevator control system then "broke," and the airplane's nose subsequently started to drop. The pilot established that he still had aileron and rudder control; however, he was not able to control the airplane's pitch. The pilot chose to parachute from the airplane and subsequently landed in a field. The airplane crashed into a field south of the pilot's location and was substantially damaged during the impact. An examination of the flight control system revealed several points of separation along the elevator control tube and elevator torque tube assembly. The weld area between the left side elevator torque tube and the left elevator horn was fractured, and the fracture surfaces showed large areas of preexisting weld anomalies, including lack of fusion and incomplete penetration. Similar weld anomalies were present between the right elevator components. The examinations determined that incorrect weld filler metal was used. The loads that caused the separation of the left elevator torque tube were likely high but within the design specifications, and the separation likely resulted from the loads being applied to the poor quality welds, which appeared to have occurred during original manufacture.

## Factual narrative

On April 12, 2013, about 1500 central daylight time, an Atkins Acro-Sport 1 airplane, N5897, was substantially damaged when it impacted terrain 1 mile south of the Le Gros Memorial Airport (3R2), Crowley, Louisiana. The pilot had minor injuries. The airplane was registered to and operated by a private individual under the provisions of 14 Code of Federal Regulations Part 91 without a flight plan. Visual meteorological conditions prevailed for the personal flight. The local flight originated from 3R2 approximately 1435.According to the pilot, he was practicing aerobatic maneuvers in an aerobatic box near 3R2. The airplane was at 3,000 feet mean sea level when the pilot "pulled aft control stick to start the vertical upline for the shark's tooth aerobatic maneuver." The pilot stated that something in the elevator control system broke and the nose started to fall. The pilot established that he still had aileron and rudder control; however, he was not able to control the pitch of the airplane. The pilot elected to egress from the airplane, during which he injured his ankle. The pilot parachuted without further incident to a muddy rice field. The airplane crashed into a grass field south of the pilot's location and was substantially damaged during the impact. A postaccident examination of the flight control system revealed several points of separation along the elevator control tube and elevator torque tube assembly. An examination of the remaining systems revealed no anomalies. The separated portions of the elevator control tube and elevator torque tube with horns were sent to the Materials Laboratory in Washington, D.C., for further examination. The control tube was fractured through the threaded shank of the rod end fitting. The torque tube components were separated at three locations. The control tube fitting fracture and two of the three fractures in the torque tube exhibited features and deformation patterns consistent with overstress and no evidence of preexisting cracking or corrosion were noted on these fractures. The remaining fracture in the torque tube was completely contained within the weld bead between the left side tube and the left elevator horn. Magnified examinations of these fracture surfaces, showed large areas of pre-existing weld anomalies including lack of fusion and incomplete joint penetration. Lack of fusion and incomplete joint penetration accounted for large portions of the tube separation area. The remaining separation was consistent with overstress separation except in areas displaying post fracture mechanical damage. Further examination of the microstructures of the tube and horn were both fine pearlite, typical of normalized alloy steel. The weld fusion zone had a microstructure of predominately ferrite with a small amount of pearlite consistent with a very low carbon steel. The metallographic section also highlighted the lack of fusion and incomplete joint penetration. A metallographic section cut through a randomlocation on the right side elevator horn to torque tube weld also showed incomplete penetration and lack of fusion. Similar to the left side, the microstructure of the tube and horn were fine pearlite consistent with normalized alloy steels while the weld fusion zone was ferrite plus pearlite consistent with low carbon steel.

## Aircraft

- Registration: [N5897](https://openairdocs.org/deregistered/N5897-2013-05-23), registration cancelled 2013-05-23, S/N 356 (OpenAirDocs)
- Reported make and model: ATKINS ACRO-SPORT I
- Registry model: [Atkins ACRO-SPORT](https://openairdocs.org/model/atkins-acro-sport) (registry code 0564609) (OpenAirDocs)
- Registry engine: [Lycoming 0-320 series](https://openairdocs.org/engine/lycoming-0-320-series) (registry code 41508, reciprocating) (OpenAirDocs)
- Category: Airplane, amateur-built
- Serial number: 356
- Year built: 1974
- Airframe hours: 3325
- Engines: Lycoming IO-320-B2B 160 hp reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Airworthiness certificate: Special, Experimental light sport (Special)
- Last inspection: Condition, November 6, 2012
- Departed: 3R2, Crowley, LA
- Destination: 3R2, Crowley, LA

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 52; injuries: minor; flight instructor, commercial; airplane ratings: single-engine land; instrument ratings: helicopter, airplane; medical: class 2, with waivers/limitations; last flight review December 22, 2012; seat: single; restraint: 3-point; flight hours: 6,836 total, 70 in this make and model, 6,708 as pilot in command, 54 in the last 90 days, 20 in the last 30 days, 4 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 10° at 6 knots
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 72 °F, dew point 46 °F
- Altimeter: 29.95 inHg
- Observed at: 3R7, 11 nm away

## 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 20130412006029A](https://openairdocs.org/incident/20130412006029A), Apr 12, 2013: Atkins ACRO-SPORT, Morse, LA, Destroyed. Pilot was initiating a vertical climb to 3000 feet to perform an aerobatic maneuver and lost elevator authority. Pilot attempted to use the throttle to control…

## Other investigations on N5897 (1)

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.

- [NTSB FTW88DPA04](https://openairdocs.org/ntsb/FTW88DPA04), Jul 22, 1988: Atkins ACRO-SPORT (N5897), Fort Worth, TX, substantial damage

## Docket (1 files)

The files NTSB released with the investigation on November 10, 2014, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=86639. 4.2 MB in all.

- Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 4.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40418754&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.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.

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