[Peetwo]

Like chalk & cheese - 

Today the HVH led ATCB released the final report into the REX SAAB 340 in flight loss of a propeller: https://www.atsb.gov.au/publications/inv...-2017-032/

Media coverage, via the Oz:

Why plane lost propeller in air
ROBYN IRONSIDE
An aeroplane’s propeller which fell off during a flight above Sydney last year was “an extremely rare event”, the ATSB says.

---

The final report on the mid-flight loss of a propeller by a Regional Express (Rex) aircraft over Sydney last year has found fatigue cracking in the propeller shaft went unnoticed because maintenance engineers were not told to look for it.

The March 17 flight from Albury to Sydney had 19 people on board, when it experienced vibrations from the right engine.

As the pilots went through the checklist the vibrations worsened, so the decision was made to shut down the engine.

A short time later the propeller came off about 19km southwest of Sydney Airport, landing in dense forest and luckily missing any houses or vehicles.

The Rex crew alerted Air Traffic Control and the Saab 340 landed safely in Sydney without injury to any passengers or crew.

Inspections subsequently found the propeller shaft had fractured due to a crack in a crucial mounting bracket.

The Australian Transport Safety Bureau report delivered today, found the engine manufacturer’s maintenance documents did not include specific inspection procedures to detect fatigue cracking of the propeller shaft.

In addition, the ATSB investigation found Rex’s inspection worksheets did not provide for the recording of inspection findings.

“Consequently, this may not have provided for the best opportunity to ensure potential defects were identified, recorded and monitored,” the report said.

Since the incident, engine maker General Electric has changed maintenance manuals to include more ongoing detailed inspections of the propeller shaft.

The United States’ Federal Aviation Administration also issued an airworthiness directive, requiring repetitive visual inspection of the main propeller shaft for affected engines.

Rex also undertook a variety of measures in response to the incident including a review of maintenance practices for propeller removal and installation, which identified several areas of improvement.

The report noted that the Civil Aviation Safety Authority had audited Rex twice since the incident, looking specifically at the airlines’ propeller maintenance practices.

ATSB chief commissioner Greg Hood described the propeller loss as an “extremely rare event” and commended the Rex crew for their response to the emergency.

“The captain and the first officer demonstrated a high level of professionalism in their airmanship, communication, co-ordination and application of the safety checklist procedures in their response,” Mr Hood said.

He said the safety actions undertaken by General Electric and Rex, would reduce the risk of such a thing ever happening again.

Reading the ATCB report - see https://www.atsb.gov.au/publications/inv...-2017-032/ - I cannot ignore the bizarre difference in process/methodology, dichotomy and disassociation in the final report findings of the REX propeller serious incident (above link) and the YMEN DFO accident final report, especially under the 'findings' and 'contributory factors' sections of the reports...  

Spot the difference in methodology?

Findings

From the evidence available, the following findings are made with respect to the propeller separation event involving a 340B aircraft, registered VH-NRX (NRX), which occurred about 10 NM south-west of Sydney, New South Wales (NSW) on 17 March 2017. These findings should not be read as apportioning blame or liability to any particular organisation or individual.

Safety issues, or system problems, are highlighted in bold to emphasise their importance. A safety issue is an event or condition that increases safety risk and (a) can reasonably be regarded as having the potential to adversely affect the safety of future operations, and (b) is a characteristic of an organisation or a system, rather than a characteristic of a specific individual, or characteristic of an operating environment at a specific point in time.

Contributing factors

• The propeller shaft failed as a result of a fatigue crack that had initiated at the dowel pin hole and propagated through the shaft until it could no longer transmit the required loads.
  
• The engine manufacturer did not have specific inspection procedures in the maintenance documents of the propeller shaft to detect a fatigue crack originating from the dowel pin hole. [Safety Issue]
  

[size=undefined]
Other safety factors[/size]

• The form used by Regional Express during a propeller removal and installation, HM-26 Revision 5, included the task to inspect the propeller gearbox, but did not provide for recording of inspection findings as defined within documented procedures. Consequently, this did not provide for the best opportunity to ensure potential defects were identified, recorded and monitored.
  

[size=undefined]
Other findings[/size]

• The flight crew used checklist management and crew resource management effectively. These factors combined to contribute to a positive outcome for the aircraft.
  
• The ATSB and the engine manufacturer, General Electric, were unable to determine conclusively the reason for the fatigue crack initiation and propagation.
  

  
 &..

Findings

From the evidence available, the following findings are made with respect to the collision with terrain involving Beechcraft B200 King Air, registered VH-ZCR that occurred at Essendon Airport, Victoria on 21 February 2017. These findings should not be read as apportioning blame or liability to any particular organisation or individual.

Contributing factors

• The aircraft's rudder trim was likely in the full nose-left position at the commencement of the take-off.
  
• The aircraft's full nose-left rudder trim setting was not detected by the pilot prior to take-off.
  
• Following a longer than expected ground roll, the pilot took-off with full left rudder trim selected. This configuration adversely affected the aircraft's climb performance and controllability, resulting in a collision with terrain.
  

[size=undefined]
Other factors that increased risk[/size]

• The flight check system approval process did not identify that the incorrect checklist was nominated in the operator’s procedures manual and it did not ensure the required checks, related to the use of the cockpit voice recorder, were incorporated.
  
• The aircraft's cockpit voice recorder did not record the accident flight, resulting in a valuable source of safety related information not being available.
  
• The aircraft's maximum take-off weight was likely exceeded by about 240 kilograms.
  
• Two of the four buildings within the Bulla Road Precinct Retail Outlet Centre exceeded the obstacle limitation surface (OLS) for Essendon Airport, however, the OLS for the departure runway was not infringed and VH-ZCR did not collide with those buildings.
  

[size=undefined]
Other findings[/size]

• The presence of the building struck by the aircraft was unlikely to have increased the severity of the outcome of this accident.
  
• Both of the aircraft’s engines were likely to have been producing high power at impact.
  

The HVH REX in flight loss of prop final report aside, Ventus has kindly forwarded to me some interesting links in regards to USA regulation of airports, aviation safety and the appropriate urban development around airports... : http://www.dot.ca.gov/hq/planning/aerona...ndbook.pdf

...3.2.3 Safety

Compared to noise, safety is in many respects a more difficult concern to address in compatibility policies. A major reason for this difficulty is that safety policies address uncertain events that may occur with occasional aircraft operations, whereas noise policies deal with known, more or less predictable events that do occur with every aircraft operation. Because aircraft accidents happen infrequently and the time, place, and consequences of their occurrence cannot be predicted, the concept of risk is central to the assessment of safety compatibility. From the standpoint of land use planning, two variables determine the degree of risk posed by potential aircraft accidents:

 Accident Frequency: Where and when aircraft accidents occur in the vicinity of an airport; and
 Accident Consequences: Land uses and land use characteristics that affect the severity of an accident when one occurs...

....To assist ALUCs in delineation of safety zones for a given airport, this Handbook provides sets of generic zones intended to serve as a starting place for the exercise. A total of seven examples of different safety zone configurations are delineated in a series of diagrams shown in the figures on the following pages. Figure 3A includes safety zone examples for five different types of general aviation runways. Figure 3B presents examples for runways at a large air carrier and military airports. The diagrams divide the airport vicinity into as many as six safety zones in addition to the immediate runway environs (defined by the FAR Part 77 primary surface):

 Zone 1: Runway protection zone and within runway object free area adjacent to the runway;
 Zone 2: Inner approach/departure zone;
 Zone 3: Inner turning zone;
 Zone 4: Outer approach/departure zone;
 Zone 5: Sideline zone; and
 Zone 6: Traffic pattern zone (not applicable to large air carrier airports).

The intent of the set of zones depicted for each example is that risk levels be relatively uniform across each zone, but distinct from the other zones. For the most part, the shapes and sizes of the zones were established based upon mathematical analyses of the accident location data presented in this and Appendix E. Not clearly stated in past editions, though, was that another factor also played a part in the zone delineation and is important to acknowledge here: flight parameters. More specifically, as an aircraft approaches for landing or climbs out after takeoff, how is it being operated? Where is it normally flying relative to the runway, and at what altitude? Is it flying straight and level or turning and climbing or descending? What actions pose the greatest stress on the aircraft and greatest potential for loss of control or fewest options for recovery if the unexpected occurs? Where are conflicts between aircraft in flight most likely to happen and potentially create risks for the land uses below?... 

   
&.. http://onlinepubs.trb.org/onlinepubs/acr...ntData.pdf 

Introduction

Establishing appropriate land use and development controls in areas near the ends of airport runways or under the arrival and departure flight paths requires an understanding of the risk of being killed or injured in an aircraft accident that occupants of those areas would be exposed to as a result of the aircraft operations at the airport. In addition, there is some risk of property damage resulting from an aircraft accident, although this is generally considered a less serious concern than the potential for fatalities or serious injuries. The risk to those on the ground from an aircraft accident is referred to as third-party risk.

The analysis of third-party risk requires detailed data on the location and other relevant characteristics of aircraft accidents occurring in the vicinity of airports. Since the risk will vary with the types of aircraft using the airport, as well as the composition of the traffic and the number of annual operations using each runway, the accident data used for the risk analysis needs to be detailed enough to identify all the relevant factors. In particular, account should be taken of the occurrence of factors in a given accident that are likely to vary with the specific conditions at a given airport. For example, accidents due to aircraft icing are not likely to occur at an airport in a tropical climate, while accidents due to a collision with high terrain are not likely to occur at an airport located on a relatively flat plain. Therefore, the reliability of any analysis of third-party risk is critically dependent on the quality and comprehensiveness of the accident data used to perform the analysis...

MTF...P2