Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."
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Sucked into turbine 3
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LittleInch
Petroleum
I think this highlights again how procedures are no substitute for physical barriers.
As said somewhere else, with ear defenders on and no doubt thinking of other things, how easy was it to not realise that this aircraft was acting differently to any other.
A single red flashing beacon alongside all the other flashing lights may not stand out.
Given how small and bright LEDs are why not have a string of them buried in the apron Flashing or bright RED until the engine stops??. They do this on taxiways now to stop runway incursion. Or a small set imbedded in the inlet ring of the engine? Times move on and they are now so small and light they should use what is now available.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
As said somewhere else, with ear defenders on and no doubt thinking of other things, how easy was it to not realise that this aircraft was acting differently to any other.
A single red flashing beacon alongside all the other flashing lights may not stand out.
Given how small and bright LEDs are why not have a string of them buried in the apron Flashing or bright RED until the engine stops??. They do this on taxiways now to stop runway incursion. Or a small set imbedded in the inlet ring of the engine? Times move on and they are now so small and light they should use what is now available.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
Alistair_Heaton
Mechanical
The beacon is normal, it's flashing it hot aircraft is the very basic rule.
Nav lights green and red on wings and white on the tail means it's live.
It's been the rule for a 100 years now.
My personal opinion is it's a human failure. Linked with I will admit flight crew failure but I might be a bit hard on the flight deck.
Nav lights green and red on wings and white on the tail means it's live.
It's been the rule for a 100 years now.
My personal opinion is it's a human failure. Linked with I will admit flight crew failure but I might be a bit hard on the flight deck.
I recall at some airport, there were zones marked off, on the ground, around where the engine intake would be, if the plain were properly parked. These zones were marked with specific colors to discourage people from walking there.
I also have seen cones with a pipe between them at the head of these areas, to also discourage walking there.
Actually thin has been a problem in aviation, as reports of people walking into propellers had been a thing.
I also have seen cones with a pipe between them at the head of these areas, to also discourage walking there.
Actually thin has been a problem in aviation, as reports of people walking into propellers had been a thing.
Alistair_Heaton
Mechanical
It's extremely rare there is more risk of being killed driving to work than committing aviation
Regarding the comment from georgeverghese about a coarse protective screen, the DC-8-61/-62/-63 aircraft that Airborne Express used at the tail end of the last century had exactly that, and it saved a mechanic on the ramp who suffered a broken arm but that was all. That fixed screen saved his life. However, that is the only aircraft model I recall that had them, although I never paid much attention to engine inlets (other than staying as far away as possible) since I was mostly avionics at that point in my career.
Alistair_Heaton
Mechanical
debodine trying to find a picture of that setup.. I don't disbelieve you, the DC8 is a proper old virtually zero bypass coal burner. The air velocity going into the front of its engines was many times more than it is on modern high bypass engines. I expect it had a significantly more safety distance than 2.5 meters.
I wouldn't mind seeing the STC for that mod purely for an interest POV.
I wouldn't mind seeing the STC for that mod purely for an interest POV.
Alistair, I will poke around some as well. As I recall, those engines were only on the DC-8-62 and the DC-8-63, but I cannot recall for sure. I will see if I can get an authoritative source for you. I think if I recall they were not bypass engines. I know the later DC-8-71 series had the high bypass engines, but we never flew the 71 series at Airborne Express while I was there. I appreciate the question and will see what I can do to get an answer.
Alistair, I found a good photo (see the link). This photo is of the JT3D-7 engine used in the DC-8-63 we flew. The same engine except for the dash, the JT3D-3B, was used in the DC-8-62 we flew. Every other photo I found of any dash of the JT3D engine had the same fixe vane front face.
Unfortunately I was never able to find a clear photo of the front face of the JT3D-XX while still installed on the aircraft. All such photos I found from the correct angle could not show the fixed vanes because they were outdoor photos in bright light and the engine is set so far back in the cowl the fixed vane region was too dark to see.
You can see in the photo that the front face vanes are welded in place. This is what saved the Airborne Express ramp person. Good question on your part! Also, it was fun for me to stir up the memories of my days working and flying on those classic DC-8 airplanes.
Unfortunately I was never able to find a clear photo of the front face of the JT3D-XX while still installed on the aircraft. All such photos I found from the correct angle could not show the fixed vanes because they were outdoor photos in bright light and the engine is set so far back in the cowl the fixed vane region was too dark to see.
You can see in the photo that the front face vanes are welded in place. This is what saved the Airborne Express ramp person. Good question on your part! Also, it was fun for me to stir up the memories of my days working and flying on those classic DC-8 airplanes.
Alistair_Heaton
Mechanical
You see I wouldn't say that's a front intake grill. That's a flow director to optimise the intake airflow. The current new engines are getting something similar with variable vane angles on them.
I honestly won't mind being wrong though. And the amount of delta P across that even at idle tick over power I would say we are back into garlic press effect.
I honestly won't mind being wrong though. And the amount of delta P across that even at idle tick over power I would say we are back into garlic press effect.
I am sure your description of the fixed vane function is more accurate than mine. I suspect at the moment he was sucked into the intake, the Airborne Express ramp person only cared that the fixed vanes performed the function of preventing him being the garlic! ![[2thumbsup]](/data/assets/smilies/2thumbsup.gif "[2thumbsup] [2thumbsup]")
Alistair_Heaton
Mechanical
Mate its interesting I had visions of chicken wire grill across the front. Not an aerodynamic set of fins which your picture showed..
As a stick monkey we just spot the difference with the airframe/engines and don't really know about the how's and whys. If its different we call the technicians.
I am very interested now what those vanes actually are, thankyou very much for posting.
Hopefully someone will know and can educate us both.
As a stick monkey we just spot the difference with the airframe/engines and don't really know about the how's and whys. If its different we call the technicians.
I am very interested now what those vanes actually are, thankyou very much for posting.
Hopefully someone will know and can educate us both.
georgeverghese
Chemical
Agreed, those look like variable guide vanes at the air intake of the JT3D-7.
Air flow during idle probably is much lower than at full load, especially on 2 shaft gas turbine. And the guard screen could even be a portable one, wheeled into place in front of the engine. Maybe even enable an electrical interlock with this guard screen so that, when the plane is parked, you cannot start the engine without the guard screen being wheeled in place and wired into some electrical socket on the engine cowl ? Depending on ground staff to keep out of a no go zone at the engine front at all times is simply not acceptable; humans WILL err.
Air flow during idle probably is much lower than at full load, especially on 2 shaft gas turbine. And the guard screen could even be a portable one, wheeled into place in front of the engine. Maybe even enable an electrical interlock with this guard screen so that, when the plane is parked, you cannot start the engine without the guard screen being wheeled in place and wired into some electrical socket on the engine cowl ? Depending on ground staff to keep out of a no go zone at the engine front at all times is simply not acceptable; humans WILL err.
If you're talking about the pieces radiating out from that central element, those appear fixed to the outer wall.
Thus not variable.
Here's another shot that's very big. You can see they can't move:
spsalso
Thus not variable.
Here's another shot that's very big. You can see they can't move:
spsalso
JohnRBaker
Mechanical
I would think that they serve a structural purpose, simply holding the main bearing for the rotating element of the engine. The shape of the 'blades' are there just to conform with the direction that the air was already going to be moving.
John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:
UG/NX Museum:
The secret of life is not finding someone to live with
It's finding someone you can't live without
John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:
UG/NX Museum:
The secret of life is not finding someone to live with
It's finding someone you can't live without
TugboatEng
Marine/Ocean
This same type of inlet guide vane was popular for tugboat propellers for a minute. NautiCan developed them. We called them pre-swirl stators. They have since fallen out of favor. Our one vessel that has them had half removed but I was not part of that decision process and can't explain why.
LittleInch
Petroleum
But difficult from one photo but they look like variable pitch inlet vanes to me.
The blog post looks different to the photo.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
The blog post looks different to the photo.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
Alistair_Heaton
Mechanical
What I am about to write might be complete nonsense no change some might say.
The front compressor stage can be quite touchie with wind direction which is maybe the reason why they have such colossal cowls forward of it on some aircraft.
If the front compressor stalls you get reverse flow that then blows hot gas forwards through the normally relatively cold compressor stages it won't damage things on idle power but will at takeoff power. Which basically cooks them. If it happens in flight you get engine surges and you have to shut the engine down.
Those vanes which are fixed control the angle of attack of the air entering that front compressor disk to prevent compressor stall.
Modern turbo fan engines The front disk which you can see mostly just pushes air down the sides of the engine. The second stage of the compressor core is behind that fan which does do a bit of engine compression but not much. What it does do though is set the airflow up for entry into the next compressor stage. The modern cores are so small compared to the fans. The geared fan on the PW1500G is basically the same diameter as my height 6'. The inlet compressor on the core is basically about the same as my thigh and it also has guide vanes in front of it. You get 24k out of them and I think they are working on getting another increased flat rating approval to 26k. I might add I have never used 24k outside the sim in real life if you need to use unrestricted 24k for departure it carries a pretty hefty penalty from the engine owners. The only time we would likely need it would be somewhere hot and high like Madrid with a full load or 50 degrees in Dubai and max performance takeoff weight. Its not a problem if you really need to use it. Just submit a report with your performance calcs and nothing more will be said.
So in summary I suspect they had issues with the first stage compressor stalling triggering engine surges and that was the fix.
The front compressor stage can be quite touchie with wind direction which is maybe the reason why they have such colossal cowls forward of it on some aircraft.
If the front compressor stalls you get reverse flow that then blows hot gas forwards through the normally relatively cold compressor stages it won't damage things on idle power but will at takeoff power. Which basically cooks them. If it happens in flight you get engine surges and you have to shut the engine down.
Those vanes which are fixed control the angle of attack of the air entering that front compressor disk to prevent compressor stall.
Modern turbo fan engines The front disk which you can see mostly just pushes air down the sides of the engine. The second stage of the compressor core is behind that fan which does do a bit of engine compression but not much. What it does do though is set the airflow up for entry into the next compressor stage. The modern cores are so small compared to the fans. The geared fan on the PW1500G is basically the same diameter as my height 6'. The inlet compressor on the core is basically about the same as my thigh and it also has guide vanes in front of it. You get 24k out of them and I think they are working on getting another increased flat rating approval to 26k. I might add I have never used 24k outside the sim in real life if you need to use unrestricted 24k for departure it carries a pretty hefty penalty from the engine owners. The only time we would likely need it would be somewhere hot and high like Madrid with a full load or 50 degrees in Dubai and max performance takeoff weight. Its not a problem if you really need to use it. Just submit a report with your performance calcs and nothing more will be said.
So in summary I suspect they had issues with the first stage compressor stalling triggering engine surges and that was the fix.
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