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Originally Posted by hans brinker
(Post 11380015)
I mean, if the tail goes from a lot of negative lift, to just a little negative lift, so less negative lift from the tail, does that not mean "more" lift (hopefully what he meant....)? Obviously, you are correct in your reply about what aerodynamically happens, maybe just a language difference.
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Originally Posted by blind pew
(Post 11380027)
Just taught many moons ago to be precise especially when instructing…now that Bernoulli has been discredited and triplex systems are unnecessary glad I don’t work anymore.
When you apply his equations to problems in the right context they work perfectly. Bernoulli equations calculate the pressure drop when some part of a fluid flows faster, this is true the pressure does drop, but trying to apply this to explain why an aerofoil produces lift is flawed because the theory of why an aerofoil produces life was flawed in the first place as the principal of equal transit times has been shown to be false. |
Originally Posted by michaelbinary
(Post 11380044)
Bernoulli has not been discredited at all.
When you apply his equations to problems in the right context they work perfectly. Bernoulli equations calculate the pressure drop when some part of a fluid flows faster, this is true the pressure does drop, but trying to apply this to explain why an aerofoil produces lift is flawed because the theory of why an aerofoil produces life was flawed in the first place as the |
Originally Posted by blind pew
(Post 11380027)
Just taught many moons ago to be precise especially when instructing…now that Bernoulli has been discredited and triplex systems are unnecessary glad I don’t work anymore.
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In the real world, the air molecules are not moving over or under a wing. They are simply sitting still, or wandering around gently, having a great day - until suddenly some metallic object whips past them: "WTF was that?", they say. The ones above got squished up together, the ones underneath not so much.
So the air molecules are not 'trying to equalise their speed over the wing' they are sitting still while the wing is doing the moving past them and pushing them up or down. Most wind tunnels, of course, move the air molecules while keeping the wing static, and I wonder if this is where the confusion arose? |
What about when parked on the ramp...
Originally Posted by Uplinker
(Post 11380212)
In the real world, the air molecules are not moving over or under a wing. They are simply sitting still, or wandering around gently, having a great day - until suddenly some metallic object whips past them: "WTF was that?", they say. The ones above got squished up together, the ones underneath not so much.
So the air molecules are not 'trying to equalise their speed over the wing' they are sitting still while the wing is doing the moving past them and pushing them up or down. Most wind tunnels, of course, move the air molecules while keeping the wing static, and I wonder if this is where the confusion arose? |
As with most thing, it's all relative ...
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"According to first analysis of the flight data recorders both propellers of the aircraft went into the feather position."
AvHerald 02/06/2023 |
Originally Posted by Uplinker
(Post 11380212)
In the real world, the air molecules are not moving over or under a wing. They are simply sitting still, or wandering around gently, having a great day - until suddenly some metallic object whips past them: "WTF was that?", they say. The ones above got squished up together, the ones underneath not so much.
So the air molecules are not 'trying to equalise their speed over the wing' they are sitting still while the wing is doing the moving past them and pushing them up or down. Most wind tunnels, of course, move the air molecules while keeping the wing static, and I wonder if this is where the confusion arose? Youbtakenthebframe of the air, in which the wing is moving. But it is totally equivalent to see it dromen the frame of the wing, in which the air is moving. Both will come to the same result. |
Originally Posted by gearlever
(Post 11380967)
"According to first analysis of the flight data recorders both propellers of the aircraft went into the feather position."
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Were they immediately identifying Dead engines ? So they would be flying very close to V (mca) after noticing either of the engine failed , Would Feathering Both engines be a safe way to keep the plane gliding until they identify failed engine .
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I would suggest fire-walling the engines would be a somewhat better reaction whilst you identify any failed engine. Gliding from low altitude is rather time limited.
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A possibility is that they may have been too high to change runway and decided to put the engines into 100% over-ride (fine pitch) using the condition levers to create drag and maybe move them back to the Auto position when they got on the new profile but mistakenly brought them to feather.
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Originally Posted by gearlever
(Post 11380967)
"According to first analysis of the flight data recorders both propellers of the aircraft went into the feather position."
AvHerald 02/06/2023 Spurious auto-feather on TransAsia Airways ATR 72-600 And that is, indeed, what happened, according to the formal investigation conducted by the Aviation Safety Council of Taiwan (ASC). However, the instigating factor likely came as a surprise to most aviation safety specialists due to its rarity: The ASC found that the accident was prompted by a spurious activation of the propeller autofeather system. Moreover, the council’s final report indicated that even before the accident occurred the morning of Feb. 4, 2015, there was evidence that the system could fail. It had happened twice (without further mishap) due to intermittent signal discontinuities related to aging of the system, and the engine manufacturer had issued service instructions to address the problem. The ASC found that the airline, TransAsia Airways, had not adequately informed its flight crews of the problem and had not issued clear instructions that a takeoff must be rejected if there are any signs that the autofeather system is not working properly. |
A spurious (uncommanded) auto-feather of both engines simultaneously would be really bad luck ...
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Originally Posted by DaveReidUK
(Post 11381097)
A spurious (uncommanded) auto-feather of both engines simultaneously would be really bad luck ...
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Is there any recorded aviation accident when both props would auto feather at the same time without crew input (regardless of type) ?
Now how they achieved that will be an interesting read… |
Originally Posted by blind pew
(Post 11380027)
Just taught many moons ago to be precise especially when instructing…now that Bernoulli has been discredited and triplex systems are unnecessary glad I don’t work anymore.
Originally Posted by michaelbinary
(Post 11380044)
Bernoulli has not been discredited at all.
When you apply his equations to problems in the right context they work perfectly. Bernoulli equations calculate the pressure drop when some part of a fluid flows faster, this is true the pressure does drop, but trying to apply this to explain why an aerofoil produces lift is flawed because the theory of why an aerofoil produces life was flawed in the first place as the principal of equal transit times has been shown to be false. |
Originally Posted by atakacs
(Post 11381123)
Is there any recorded aviation accident when both props would auto feather at the same time without crew input (regardless of type) ?
… |
Originally Posted by ATC Watcher
(Post 11381400)
Might have been in the early pistons aircraft types when it was introduced, but all the events I remember were I always at or right after take off , Having that on base leg with reduced power ? and as you said, on both engines at the same time ? Weird.
Disclaimer: I'm in no point saying that's what happened there but that is a possible scenario on another type of aircraft. |
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