Aviation safety investigations & reports

Propeller blade collar failure involving de Havilland DHC-8, VH-ZZA, near Darwin, Northern Territory, on 3 December 2019

Investigation number:
Status: Completed
Investigation completed
Phase: Final report: Dissemination Read more information on this investigation phase

Final Report

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What happened

On 3 December 2019, a de Havilland Canada DHC-8-202 (Dash 8) aircraft registered VH-ZZA departed Darwin Airport, Northern Territory to conduct aerial work. During the early stages of the climb, the flight crew heard a loud bang. There were no issues with systems or controllability, so the flight was continued without further incident. Subsequent inspections of the aircraft revealed the number 2 blade collar on the right propeller was missing. There was also damage on the number 1 blade and the ice shield on the fuselage. Removal of the ice shield revealed that the fuselage had been penetrated in two places.

What the ATSB found

The ATSB identified that the propeller blade collars on the number 2 and number 3 blades were last repaired in the field, having been found loose. Following this occurrence, both blades were examined. There was evidence of inadequate cleaning/preparation on the number 2 blade shank, and the collar on the number 3 blade was loose due to adhesive remaining from a prior repair.

Based on those observations, it was likely that issues with surface preparation during field repairs resulted in a lack of adhesion between the number 2 blade and its collar, allowing it to separate in flight. The blade collar then struck the number 1 blade, accelerating the fragments of the collar forcefully into the aircraft's fuselage.

What has been done as a result

As a result of this occurrence, the operator released an engineering notice requiring the entire blade assembly to be replaced in the event of a loose or cracked blade collar. If a serviceable blade assembly was not available, collars were to be replaced in consultation with the relevant Technical Services Engineer, and in strict accordance with the component maintenance manual.

Safety message

Due to constraints on equipment, time, and experience, field repairs can be a source of added risk to an aircraft. To minimise risk, maintenance manuals should be closely followed when conducting field repairs, and operators should consider alternatives such as replacement over repair whenever practical.

This occurrence also illustrates that in‑flight damage may not always be apparent to flight crew and the risks posed by incorrect attribution. Serious consideration should be given to terminating the flight following any unexplained abnormal indication.

Download final report
[Download  PDF: 347KB]

The investigation

General details
Date: 03 December 2019   Investigation status: Completed  
Time: 1200 CST   Investigation level: Short - click for an explanation of investigation levels  
Location   (show map): near Darwin Airport   Investigation phase: Final report: Dissemination  
State: Northern Territory   Occurrence type: Propeller/rotor malfunction  
Release date: 03 September 2020   Occurrence category: Incident  
Report status: Final   Highest injury level: None  

Aircraft details

Aircraft details
Aircraft manufacturer de Havilland Aircraft Pty Ltd  
Aircraft model DHC-8-202  
Aircraft registration VH-ZZA  
Serial number 419  
Operator Cobham Aviation Services Australia  
Type of operation Aerial Work  
Sector Turboprop  
Damage to aircraft Minor  
Departure point Darwin, Northern Territory  
Destination Darwin, Northern Territory  
Last update 30 November 2020