Rex aircraft losses a prop mid-flight

[cooperplace]

For sure, but if you or I were in that situation we'd obviously be very busy up front, and our priority would be to get all on board back down safely rather than worrying about whose tomato crop we were going to flatten with the bits that fall off. That's probably of secondary importance, even if we'd all like to know exactly where it fell.PS Sorry, I missed a couple of posts

like the flight attendant in the 1964 Essendon DC6B incident, where a prop fell off: she went up to the flight deck and said the crew were "as busy as one-armed paper hangers".

 

 

[Downunder]

REX flight's detached propeller found in bushland south-west of Sydney

 

REX flight's detached propeller found in bushland

 

 

[Admin]

Do you get to claim ownership if it came through your roof into your living room or would you be charged with theft...a mans home is his property

 

 

[BLA82]

Do you get to claim ownership if it came through your roof into your living room or would you be charged with theft...a mans home is his property

Possesion is 9/10 of the law so grab a great lawyer and im sure you could own it lol

 

 

[Admin]

I mean technically they disposed of it by throwing it away

 

 

[Marty_d]

If it went through your roof I reckon the legal settlement would more than make up for the value of the prop even if you had to give it back...

 

 

[David2ayo]

Do you get to claim ownership if it came through your roof into your living room or would you be charged with theft...a mans home is his property

It depends on who you are and how much you pay your lawyer. If you had made the mistake of talking to a 1% biker in the last 10 years, you would be charged with theft, malicious damage to the propellor, dealing with the proceeds of crime, contamination of the evidence (if it had sconed somebody or the family cat) and hindering the investigation of an aviation investigation. If, on the other hand, you were a political party donor, or, worse, a politician, you would be offered compensation, a free house while yours is repaired, counselling, free flights for life and the propellor would be mounted on a suitable frame in your loungeroom and be signed by the pilot, first officer, hostie, Rex general manager and the police officer who responded to the call.

 

 

[BLA82]

David you forgot the autograph from the ATSB investigating officer

 

 

[Admin]

And the street party at the local councils cost

 

 

[old man emu]

Sorry to get back to being all techno an' that, but doesn't a prop feathering mechanism work by applying oil pressure to the blade movement assembly, causing the blade angle to change? Further, isn't the default, no oil pressure position of the blades the "fully feathered" position?

 

If I'm correct, that would explain the blades being in the fully feathered position when found. However, I does not explain the lack of oil contamination on the engine nacelle after landing. Unless there was some cleaning up for the cameras.

 

OME

 

 

[spacesailor]

Or it had all leaked away, before detachment!.

 

spacesailor

 

 

[dutchroll]

Further, isn't the default, no oil pressure position of the blades the "fully feathered" position?OME

Not necessarily. It depends if the propeller has a single acting pitch control mechanism (PCM) or a double acting PCM and whether the blades are counter-weighted or not.

The natural tendency of a propeller blade is to want to drive towards fine pitch due to centrifugal twisting moment. Aerodynamic twisting moment is a lesser force and drives it towards coarse pitch when driven by the engine, but fine pitch (due to drag) when windmilling. Counterweights, when fitted, produce a twisting moment towards coarse pitch.

 

The Hamilton Standard 54H60 propeller used on the older models of C130 for example did not have counterweights. Feathering required oil pressure ported to the increase pitch side. The safety mechanism for propellers of this design is called a "pitch lock" mechanism. This prevents the pitch fining off with loss of oil pressure. Also those propellers, like many large props, do not use engine oil. They use their own oil supply and have electrical auxiliary feathering pumps which can be manually actuated if the propeller fails to feather.

 

The Saab normally has Dowty propellers I think, and Dowty tend to use counterweighted designs as far as I know (the newer C130J Hercules has Dowty propellers and they are counterweighted). So in the case of the Saab the default position without oil pressure might well be feather, but that's not necessarily the case for all aircraft.

 

 

[Marty_d]

Reporting on the ABC today suggested that, following vibration, the pilot had actually shut down the engine and feathered the prop before it fell off. Or is that not relevant to your point OME?

 

 

[old man emu]

Reporting on the ABC today suggested that, following vibration, the pilot had actually shut down the engine and feathered the prop before it fell off. Or is that not relevant to your point OME?

Of absolute relevance. It answers the question behind my question. Thanks.

 

 

[David2ayo]

ABC News online has story and good pics of prop - with the Dowty label on it! Lots of studs with no nuts - a bit interesting.

 

 

[planedriver]

As things get older, this can sometimes happen, sadly!

 

 

[dutchroll]

Looks like there's one nut still on the stud holding the prop flange on? Bit hard to tell from the photo whether the threads on the others have been stripped or not. That's a puzzling photo actually.

 

 

 

[Sloper]

Goodaye all

 

Looking at the pic and the nuts missing makes me think they where not fixed propley and spun off causing the prop to wobble on the shaft, cause it to crack and off she goes.

 

Loss of nuts in any instance is bad.

 

regards Bruce

 

 

[Bats]

Dutchroll, here is another, I note that there appear to be a couple of washers on the opposite side to the apparent nut. I wonder if the photo isn't a bit of a red herring, with the ATSB being part way through removing the flange when the journos stuck their oar in? The flange was certainly missing when the prop was photographed before being loaded onto the truck.

 

 

[cooperplace]

Not necessarily. It depends if the propeller has a single acting pitch control mechanism (PCM) or a double acting PCM and whether the blades are counter-weighted or not.The natural tendency of a propeller blade is to want to drive towards fine pitch due to centrifugal twisting moment. Aerodynamic twisting moment is a lesser force and drives it towards coarse pitch when driven by the engine, but fine pitch (due to drag) when windmilling. Counterweights, when fitted, produce a twisting moment towards coarse pitch.

 

The Hamilton Standard 54H60 propeller used on the older models of C130 for example did not have counterweights. Feathering required oil pressure ported to the increase pitch side. The safety mechanism for propellers of this design is called a "pitch lock" mechanism. This prevents the pitch fining off with loss of oil pressure. Also those propellers, like many large props, do not use engine oil. They use their own oil supply and have electrical auxiliary feathering pumps which can be manually actuated if the propeller fails to feather.

 

The Saab normally has Dowty propellers I think, and Dowty tend to use counterweighted designs as far as I know (the newer C130J Hercules has Dowty propellers and they are counterweighted). So in the case of the Saab the default position without oil pressure might well be feather, but that's not necessarily the case for all aircraft.

Dutch,

thanks again for an informative and very useful posting; I always enjoy reading your posts, your knowledge is appreciated.

 

 

[rankamateur]

Feathering required oil pressure ported to the increase pitch side. The safety mechanism for propellers of this design is called a "pitch lock" mechanism. This prevents the pitch fining off with loss of oil pressure.

I noticed a bank of brushes on the disabled engine, and now a bank of slip rings on the underside of the spinner backing plate. Having a Airmaster constant speed prop, I just accepted that it was electrically controlled pitch.

 

 

[dutchroll]

Dutchroll, here is another, I note that there appear to be a couple of washers on the opposite side to the apparent nut. I wonder if the photo isn't a bit of a red herring, with the ATSB being part way through removing the flange when the journos stuck their oar in? The flange was certainly missing when the prop was photographed before being loaded onto the truck.[ATTACH=full]49502[/ATTACH]

Yeah I wondered that too, but I'm puzzled as to why they would start disassembling the prime piece of evidence before moving it into a hangar and doing it properly. It's not going to make the investigation proceed any quicker and all it would do is risk dropping bits of evidence into muddy grass.

And why are there at least two washers left on? Surely you'd do nut, washer, nut, washer, etc, bagging them as you go. Also why would you allow journos in for photographs while you were in the middle of removing this vital evidence?

 

I'm confused......

 

I noticed a bank of brushes on the disabled engine, and now a bank of slip rings on the underside of the spinner backing plate. Having a Airmaster constant speed prop, I just accepted that it was electrically controlled pitch.

Don't forget propellers on larger aircraft are electrically de-iced. The blades at least, and often the spinner too.

 

 

[David2ayo]

Yeah I wondered that too, but I'm puzzled as to why they would start disassembling the prime piece of evidence before moving it into a hangar and doing it properly. It's not going to make the investigation proceed any quicker and all it would do is risk dropping bits of evidence into muddy grass.And why are there at least two washers left on? Surely you'd do nut, washer, nut, washer, etc, bagging them as you go. Also why would you allow journos in for photographs while you were in the middle of removing this vital evidence?

 

I'm confused......

 

Don't forget propellers on larger aircraft are electrically de-iced. The blades at least, and often the spinner too.

Suspect the reason the flange was removed is that it is the most important piece of evidence, and they (whoever "they" are) didn't want it hanging under a helicopter. Why it was photographed at various stages, who knows, it really doesn't matter. Interesting to compare ABC and Seven news - suspect ABC were a bit later arriving. Note the prop landed with drive flange down, and was turned over before liftoff. Assume they were taking video / pics while this was happening, would be very embarrassing if it all fell to bits as it was moved!

 

David

 

 

[spacesailor]

What is the hole (missing bolt!) in the pic

 

spacesailor

 

 

[Ron5335]

I saw on one of the other sites the flight path the SAAB went on after notifying the tower of the prop loss.

 

The thing that stands out is that they put him on a right hand circuit for rwy 16, and that had 2 x 90 degree turns where the aircraft

 

had to turn into the dead engine.

 

I thought that was a no no.