Aviation safety investigations & reports

MD Helicopters MD 520N, VH-MPI

Investigation number:
Status: Completed
Investigation completed


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The aircraft coordinated estimate RIGMI at 0338 UTC. The aircraft passed seven minutes late, nil details were passed on from the New Zealand control centre.

At about 0630 Eastern Standard Time on 21 June 2004, a MD Helicopters MD520N helicopter, registered VH-MPI, took off from Gladstone, Queensland, to transport a marine pilot to the deck of a bulk carrier ship that was preparing to enter Gladstone harbour. During the landing on the ship, the right landing gear struts fractured. The helicopter collapsed onto its right side and the main rotor blades struck the ship's deck. The helicopter was substantially damaged and the pilot and passenger exited the helicopter uninjured.

The pilot satisfied Civil Aviation Safety Authority (CASA) recency requirements and was familiar with both the helicopter and the mission to be flown. He reported that he had conducted over 100 deck landings and was familiar with landing on ships of the type involved in the occurrence.

The pilot reported that weather conditions were fine with a clear sky, temperature about 17 degrees Celsius, wind from the south-west at about 25 knots, and a slight sea state.

The ship had a number of large hatches aligned longitudinally along the deck. The pilot was using one of those hatches as a landing area. The hatch was of a suitable size to accommodate the helicopter and there were no obstructions in the vicinity of the landing area. The pilot reported that the ship was underway and steaming at about 10 knots. The ship sustained minor damage to the hatch from main rotor blade impact.

The helicopter was fitted with a fixed utility float installation system on the landing gear. The floats had been fitted to the helicopter in July 2001 in accordance with the instructions contained in a CAR 35 engineering approval. The helicopter manufacturer was not able to provide engineering advice on the effect that the float installation would have had on the helicopter.

The primary damage to the helicopter was confined to the landing gear; in particular, the right front and right rear struts, and the main rotor assembly. A metallurgical examination of the landing gear components identified an existing fatigue crack, emanating from the drag brace attachment lower hole in the strut, as an initiation site for the failure of the right rear strut. The fatigue crack was due to the fitment of a non-standard drag brace bushing to the rear landing gear strut. The drag brace bushing also was not fitted using protective coating material and would not have been provided with corrosion protection from the marine environment. The right front strut failed in gross overload. A copy of the technical analysis investigation report, BE200400015, is at Appendix A.

Examination of the helicopter's maintenance documentation revealed the following:

  • The helicopter had a valid maintenance release for the flight.
  • The landing gear fairing fillets were removed and the landing gear was visually checked for cracks and damage during 100-hourly/annual inspections. The last 100-hourly inspection prior to the occurrence was conducted on 3 June 2004.
  • Every 300 hours a landing gear inspection was carried out in accordance with the helicopter's maintenance manual. Those inspections required that the helicopter be jacked and the landing gear checked. Any elongated, enlarged or worn holes in the strut were to be repaired. The last 300-hourly inspection prior to the occurrence was conducted on 3 June 2004.
  • There were no CASA or US Federal Aviation Administration Airworthiness Directives applicable to the 520N helicopter that would have required an inspection of the affected area to check for defects such as cracking of the strut.
  • All required landing gear periodic and special inspections were carried out.
  • Other than routine inspections, no maintenance action had been conducted in the region of the failure.
  • No record could be found to indicate when the non-standard drag brace bushing had been fitted to the rear landing gear strut.
Download Technical Analysis Report
[Download  PDF: 2.72MB]

Significant Factors

  1. The drag brace bushing did not comply with the helicopter manufacturer's specifications.
  2. The drag brace bushing hole had a rough-surface finish.
  3. The drag brace bushing was not fitted using protective coating material.
  4. Fatigue cracking initiated in the bore of the drag brace bushing hole.
  5. The right rear strut fractured during the landing.

Technical Analysis

MD Helicopters, Model MD520N, VH-MPI, 21 June 2004

Examination brief

The right front and rear landing gear strut assemblies from the helicopter (without fairings) were submitted to the ATSB's Canberra Technical Analysis Laboratory for examination and analysis of the failures. The parts were identified as follows:

Front strut: 91 - 369H 6001-42 D
Rev. 6 1-24-91
S/O. A0201132
Rear strut: PNo: 369H 6001-32

The front strut carried the identification as ink stencilled print on the elbow section of the assembly. The rear strut did not carry any permanent markings and was identified solely by reference to the attached tag.

General details
Date: 21 June 2004   Investigation status: Completed  
Time: 0645 hours EST    
Location   (show map): 30 km E Gladstone, Aero.    
State: Queensland   Occurrence type: Landing gear/indication  
Release date: 06 June 2005   Occurrence category: Accident  
Report status: Final   Highest injury level: None  

Aircraft details

Aircraft details
Aircraft manufacturer McDonnell Douglas Corp.  
Aircraft model 520  
Aircraft registration VH-MPI  
Serial number LN026  
Type of operation Aerial Work  
Damage to aircraft Substantial  
Departure point Gladstone, QLD  
Departure time 0630 hours EST  
Destination MV Energy Angel underway  
Crew details
Role Class of licence Hours on type Hours total
Pilot-in-Command Commercial 50.0 3300
Last update 13 May 2014