A Fokker 27 loses it's propeller at take-off in Paris (CDG)
The new pictures show prop blade long slashes in both sides of the fuse
The mechanism that had the blade go through the fuse sideways will be an object of study by the investigators.
Very fortunate that the fuse held together and that the flight controls remained operational.
Retracted[Seems to be a puncture in the lower fuse]. Nice that it missed the other engine.
The folks in a DC-6 were not as lucky:
ASN Aircraft accident Douglas YC-112A-DO (DC-6) N901MA Los Angeles-Van Nuys Airport, CA (VNY)
Once one blade lets go the rest of the assembly will generally be off shortly; retracted[so the long scar could be from various bits that departed in the plane of rotation].
The mechanism that had the blade go through the fuse sideways will be an object of study by the investigators.
Very fortunate that the fuse held together and that the flight controls remained operational.
Retracted[Seems to be a puncture in the lower fuse]. Nice that it missed the other engine.
The folks in a DC-6 were not as lucky:
ASN Aircraft accident Douglas YC-112A-DO (DC-6) N901MA Los Angeles-Van Nuys Airport, CA (VNY)
Once one blade lets go the rest of the assembly will generally be off shortly; retracted[so the long scar could be from various bits that departed in the plane of rotation].
Last edited by RatherBeFlying; 29th Oct 2013 at 22:30.
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I would think that if a single blade separates the imbalance of the propeller would take the whole engine off its mounting, as it did in the DC-6 accident.
To me it looks like an internal failure of the gear box. The rotating parts cut through the sidewalls of the gearbox casing and separate the front of the casing from the rest. Has happened before.
To me it looks like an internal failure of the gear box. The rotating parts cut through the sidewalls of the gearbox casing and separate the front of the casing from the rest. Has happened before.
Exit Hole?
So good to be reading of a major failure, (indeed, "accident") where the crew has apparently done a fine job, saved themselves and (maybe) the aircraft, and got the remainder of it down in one piece. 
From the ASN Accident Description:
Propeller blades sliced through the fuselage of the airplane, exiting on the other side.
The accompanying photo shows a damage line about 1.5 m long, which may include an entry slot, above and forward of the engine. It'll be interesting to see that in better detail.
43 years dim the memory. Is the prop on this Dart a 4-blade, left-hand tractor?
N707ZS says that, in jcjeant's Le Parisien photo of the recovered parts ("Dépannage" being a bit of an understatement), (s)he can see three blades of the four. So at least one is missing. If one, then how much of it entered the fuselage, passed through one of those big freight containers, and then exited the fuselage on the starb'd side?
Looking forward to seeing the exit hole...
From the ASN Accident Description:
Propeller blades sliced through the fuselage of the airplane, exiting on the other side.
The accompanying photo shows a damage line about 1.5 m long, which may include an entry slot, above and forward of the engine. It'll be interesting to see that in better detail.
43 years dim the memory. Is the prop on this Dart a 4-blade, left-hand tractor?
N707ZS says that, in jcjeant's Le Parisien photo of the recovered parts ("Dépannage" being a bit of an understatement), (s)he can see three blades of the four. So at least one is missing. If one, then how much of it entered the fuselage, passed through one of those big freight containers, and then exited the fuselage on the starb'd side?
Looking forward to seeing the exit hole...
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Further pictures here:
Accident: Miniliner F27 at Paris on Oct 25th 2013, left propeller separated in flight
Accident: Miniliner F27 at Paris on Oct 25th 2013, left propeller separated in flight
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Fokker 27, Charles de Gaulle Airport, France, 25 Octobre 2013
BEA investigation in association with ANSV, AAIB and Dutch Safety Board.
BEA investigation in association with ANSV, AAIB and Dutch Safety Board.
The cargo aeroplane, with two pilots on board, had taken off at 01h10 (local time) from Roissy Charles de Gaulle Airport bound for Dole, France. A few minutes later, the aeroplane suffered uncontained damage to the left engine. During the accident, a left propeller blade went through the fuselage. At 01h20, the crew made an emergency landing back at Roissy Charles de Gaulle Airport.
Further pictures here:
Accident: Miniliner F27 at Paris on Oct 25th 2013, left propeller separated in flight
Accident: Miniliner F27 at Paris on Oct 25th 2013, left propeller separated in flight
That blade sliced all through the fuselage and exited on the other side with much the same energy it entered it.
Next time sitting in line with the props on a Turboprop will be a slightly uneasy feeling...
Even though probability of it passing through the cabin horizontally as in this case aren't exteremly high (~10% for an angle of horizontal +/- 18°) in the already rare case of a blade separation.
You gotta love Murphy...
Thanks Dave!
Judging from the photos in the link provided by pirx, this may have been a closely-run thing, structurally. And, thinking again of the DC6, presumably the flight-control runs, and the pneumatics for the brakes and steering, lie in the bottom of the forward fuselage?
Quote from HN39:
I would think that if a single blade separates the imbalance of the propeller would take the whole engine off its mounting, as it did in the DC-6 accident.
To me it looks like an internal failure of the gear box. The rotating parts cut through the sidewalls of the gearbox casing and separate the front of the casing from the rest. Has happened before.
Which begs the question of why one blade, or part(s) of one blade, seem to have separated from the rest of the airscrew immediately, as suggested by the sideways movement.
According to Jane's, the maximum crankshaft speed of the P&W R-2800 radial piston-engine fitted on the DC6 is 2800 rpm, and the reduction gearing rotates the airscrew at 45% of that speed. That compares with 15000 rpm and about 10% of shaft speed on the turboprop Dart, whose reduction gearbox may be very different from that on the big radial engine.
Is it possible that the gross imbalance caused by the loss of most or all of one blade might cause the Dart gearbox to detach from the engine? Might even be a design feature...
Judging from the photos in the link provided by pirx, this may have been a closely-run thing, structurally. And, thinking again of the DC6, presumably the flight-control runs, and the pneumatics for the brakes and steering, lie in the bottom of the forward fuselage?
Quote from HN39:
I would think that if a single blade separates the imbalance of the propeller would take the whole engine off its mounting, as it did in the DC-6 accident.
To me it looks like an internal failure of the gear box. The rotating parts cut through the sidewalls of the gearbox casing and separate the front of the casing from the rest. Has happened before.
Which begs the question of why one blade, or part(s) of one blade, seem to have separated from the rest of the airscrew immediately, as suggested by the sideways movement.
According to Jane's, the maximum crankshaft speed of the P&W R-2800 radial piston-engine fitted on the DC6 is 2800 rpm, and the reduction gearing rotates the airscrew at 45% of that speed. That compares with 15000 rpm and about 10% of shaft speed on the turboprop Dart, whose reduction gearbox may be very different from that on the big radial engine.
Is it possible that the gross imbalance caused by the loss of most or all of one blade might cause the Dart gearbox to detach from the engine? Might even be a design feature...
Even though probability of it passing through the cabin horizontally as in this case aren't exteremly high (~10% for an angle of horizontal +/- 18°) in the already rare case of a blade separation.
I'm not sure what the comparative drag numbers would be compared to a feathered prop on a dead engine.
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Have seen similar picture for C-130's. Except with engine damage on the other side as well.
The cable runs and pneumatic lines on the F-27 all run along the cabin roof. The control cables are routed below the cockpit floor, thence up through the pneumatic panel behind the Captain's seat.
Takeoff RPM on the Dart 532 is 15,000 RPM, but climb and cruise is 14,200. I can't remember the reduction gearing - 8 to 1 or something like that - so the prop would be turning at what, 1200 RPM in cruise?
Takeoff RPM on the Dart 532 is 15,000 RPM, but climb and cruise is 14,200. I can't remember the reduction gearing - 8 to 1 or something like that - so the prop would be turning at what, 1200 RPM in cruise?
The slit is right beside the Propellor Danger sign on both sides.
Yep, they sure got the warning decal in the right place. 
Here's what the damage looked like...
Here's a drawing of the innards. It looks like most or all of the reduction gear has departed along with most of the reduction gear casing.
Here's what the damage looked like...
Here's a drawing of the innards. It looks like most or all of the reduction gear has departed along with most of the reduction gear casing.
Last edited by pigboat; 30th Oct 2013 at 02:08.
pigboat,
Thanks for the nice graphic of the reduction gearbox, starter motor, etc., on the front end of the engine, and the info on routing of control runs and pneumatics. The photo of the exit hole (in the link supplied by pirx) suggests that the blade came very close to taking them out. Shocking. Lomapaseo's description of the likely behaviour of a detached blade was interesting.
Errr, a reduction of only 8:1 @14200 rpm (cruise) would give a prop speed of 1775 rpm? Not sure what the engine rpm is in the climb (14700?). Jane's shows that there seem to be two ratios for the various models of Dart: both around 10:1 (guess it depends partly on the prop diameter). The one that seems likely for the Dash 532 is written as 9.3%, i.e., 1000:93.
Thanks for the nice graphic of the reduction gearbox, starter motor, etc., on the front end of the engine, and the info on routing of control runs and pneumatics. The photo of the exit hole (in the link supplied by pirx) suggests that the blade came very close to taking them out. Shocking. Lomapaseo's description of the likely behaviour of a detached blade was interesting.
Errr, a reduction of only 8:1 @14200 rpm (cruise) would give a prop speed of 1775 rpm?
Not sure what the engine rpm is in the climb (14700?). Jane's shows that there seem to be two ratios for the various models of Dart: both around 10:1 (guess it depends partly on the prop diameter). The one that seems likely for the Dash 532 is written as 9.3%, i.e., 1000:93.
Last edited by Chris Scott; 30th Oct 2013 at 10:38.
The one that seems likely for the Dash 532 is written as 9.3%, i.e., 1000:93.
Per the TC, reduction gear ratios are:
0.086:1 Dart 511/514
0.093:1 Dart 528/529/532/533/534/535/536/550/552
0.0775:1 Dart 542/543
Best shot of the exit side in pirx link above.
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I had almost 3,000 hrs on the F27 + F227 and always felt totally sure that they would get me home safely as long as they were well looked after....Which isn't always easy as they are both very simple and very difficult to maintain at the same time....Our Engineers always said that the F27's were better built, but the pneumatics were difficult compared to looking after hydraulics, and were always the most frequent problem with our machines....
Phrase ' built like a brick sh*thouse ' could have been invented for the F27, and we gave up our last machines just a few of years ago in favour of ATR's only for the economics of running and, in particular for us, maintaining the Darts, not the airframe.... Perhaps a similar issue here with engine maintenence ??
I wonder how many 45 years old ATR's will be on active service when the time comes....I'd guess not many ! And I'm certainly not going to volunteer to test for the outcome of an incident like this on an ATR....
As for this incident, absolute respect and total applause to the crew who must have had a brown trouser moment few of us are ever likely to experience and to have got the machine and themselves safely back down when their minds ( and imagination ! ) must have been somewhere, anywhere, else when they heard the noise of the fuselage ripping and could only hope the flight controls were not damaged....And, for you non-freightdogs, at 01.10 when your levels of alertness and concentration are not at their best no matter for how long you've been regular night flying....
Chapeau, gentlemen !!
Phrase ' built like a brick sh*thouse ' could have been invented for the F27, and we gave up our last machines just a few of years ago in favour of ATR's only for the economics of running and, in particular for us, maintaining the Darts, not the airframe.... Perhaps a similar issue here with engine maintenence ??
I wonder how many 45 years old ATR's will be on active service when the time comes....I'd guess not many ! And I'm certainly not going to volunteer to test for the outcome of an incident like this on an ATR....
As for this incident, absolute respect and total applause to the crew who must have had a brown trouser moment few of us are ever likely to experience and to have got the machine and themselves safely back down when their minds ( and imagination ! ) must have been somewhere, anywhere, else when they heard the noise of the fuselage ripping and could only hope the flight controls were not damaged....And, for you non-freightdogs, at 01.10 when your levels of alertness and concentration are not at their best no matter for how long you've been regular night flying....
Chapeau, gentlemen !!
Hussar 54,
...And, for you non-freightdogs, at 01.10 when your levels of alertness and concentration are not at their best no matter for how long you've been regular night flying....
Hear, hear...
...And, for you non-freightdogs, at 01.10 when your levels of alertness and concentration are not at their best no matter for how long you've been regular night flying....
Hear, hear...
DOVE
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Is there anybody who knows how much is the centrifugal force a propeller blade, the size and mass of that of an F27, which is turning ... let’s say at 2000 RPM is subject to?
- Kilograms?
- hundreds of kilograms?
- Tons?
And what do you think it will happen if one of them is eradicated and thrown away?
- Kilograms?
- hundreds of kilograms?
- Tons?
And what do you think it will happen if one of them is eradicated and thrown away?
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Centripetal Force is m.v squared / r. There are probably better equations
that are in terms of rpm (I think Omega squared / r springs to mind.)
But at a rough guess I suspect it must be in the order of 100 tonnes, hence the thickness of the metal at the blade root, to withstand this constant force.
It will all depend upon the actual radius of the CG of the Blade, and its weight, as well as the actual rpm.
Edit... Just found a calculator, if you use 0.7 m radius, 2000rpm and 30Kg
it works out at 104 Tonnes...
CalcTool: Centrifugal force calculator
that are in terms of rpm (I think Omega squared / r springs to mind.)
But at a rough guess I suspect it must be in the order of 100 tonnes, hence the thickness of the metal at the blade root, to withstand this constant force.
It will all depend upon the actual radius of the CG of the Blade, and its weight, as well as the actual rpm.
Edit... Just found a calculator, if you use 0.7 m radius, 2000rpm and 30Kg
it works out at 104 Tonnes...
CalcTool: Centrifugal force calculator
Last edited by phiggsbroadband; 30th Oct 2013 at 16:25.