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The purpose of telling pilots thrust was to save money and fuel. It’s a “least viable” optimization. >“The goal is to lower the power used on takeoff,” he sai

by basch 4y ago

The purpose of telling pilots thrust was to save money and fuel. It’s a “least viable” optimization. >“The goal is to lower the power used on takeoff,” he said. “That reduces engine wear and saves money” on fuel and maintenance. >Flights to Hawaii are typically full, with lots of baggage and a full load of fuel for the trip across the ocean. The planes are heavy. > That morning, a software bug in an update to the DynamicSource tool caused it to provide seriously undervalued weights for the airplanes. >Peyton added that even though the update to the DynamicSource software had been tested over an extended period, the bug was missed because it only presented when many aircraft at the same time were using the system. > Both planes headed down the runway with less power and at lower speed than they should have. And with the jets judged lighter than they actually were, the pilots rotated too early. >The data “confirms that the airplane was safely airborne with runway remaining and at an altitude by the end of the runway that was well within regulatory safety margins. Both aircraft got airborne well within safety limits despite the lower thrust. It’s also probably lucky that two Hawai’i bound flights both didn’t notice the discrepancy, or two bumps wouldn’t have bee as suspicious. Interesting that someone cited divorce and sleep examples as emotional pleas, reassuring us they are only human. Like all complex failures at least 5 things had to happen. Software update that morning, some kind of hard to simulate resource issue in processing, overweight flights, pilot not pricing plane data appeared light, pilot turning early despite low speed, two in a row.

pxmpxm 4y ago
>Interesting that someone cited divorce and sleep examples as emotional pleas, reassuring us they are only human. Huh? FAA spends a huge amount of time and energy focusing on human factors, tasks saturation rates and crew resource management. Nothing to do with with argumentum ad passiones, just prudent risk mitigation.
- hooverd 4y ago
  I thought a lot of safety thinking was built around acknowledging that humans don't do everything perfectly all the time.
  - ddulaney 4y ago
    It does, and one class of mitigation is to improve automation, which airlines (and their regulators) do all the time. But another class of mitigations is to make the human less error-prone in the first place. This is especially important in preventing failures that were caused by improper management of the automation. Hence the emphasis on rest periods, training, and other mitigations on the human side. In the "swiss cheese" model, a disaster needs to slip through both the human's defenses and the automation's defenses to actually happen. It makes sense to improve both of those layers of defense against disaster, while acknowledging that humans will never be perfect. But at least they can be awake and knowledgable.
- NovemberWhiskey 4y ago
  Right. Literally every pilot in the US has been taught the IMSAFE mnemonic to assess fitness to fly, even before their first solo in a single-engine piston: Illness, Medication, Stress, Alcohol, Fatigue and Emotion.
- basch 4y ago
  I just don’t see how it fit the article. Unless they are surmising the pilots poorly sanityized the data going into the computer because they were having an off day.
  - mynameisvlad 4y ago
    I mean, yes. That is literally exactly what they’re saying. The full quote: > …if there’s a glitch, naturally some pilot somewhere is going to miss it. “Not everyone gets eight hours sleep the night before. Someone is going through a divorce. Someone is not so sharp that morning,” he said. “The sanity check isn’t perfect every day of the week.”
deleted 4y ago
[deleted]
mnw21cam 4y ago
> The purpose of telling pilots thrust was to save money and fuel. No, it's more that using lower thrust during take off saves on engine wear and noise levels around the airport. It doesn't really have that big an impact on fuel use, at least that's not the primary purpose. The article concentrates far too much on the thrust setting. The important bit is the speed where the plane should be rotated to take off, which is known as V_r. That depends on the weight of the plane. On the takeoff roll, the pilots watch the airspeed indicators and pull back to lift off when that speed has been reached. If they have been told a V_r that is lower than it should be, then pulling back will rotate the aircraft without it taking off, and that's when you have this danger of the tail hitting the ground. When that happens, the plane must be inspected, because a tail strike has the potential to weaken the pressurised container that is the fuselage, and this could lead to an explosive burst and depressurisation when flying at high altitude. See https://en.wikipedia.org/wiki/China_Airlines_Flight_611 https://en.wikipedia.org/wiki/China_Airlines_Flight_611 for why this is a Bad Thing.
- basch 4y ago
  > saves on engine wear Which is saving on money
  - seabird 4y ago
    I'm cracking up at the thought of an airline telling their pilots "fuck it, run em however hard you think you need to." There's a difference between dumping toxic waste into a river to save money and keeping a plane engine in safe operating conditions to save money.
- phkahler 4y ago
  It seems like a slower rotation might be useful, to wait until you feel it leave the ground before aiming higher. I'm sure there are reasons for the procedure as is.
  - jcrawfordor 4y ago
    Trying to "force the airplane off the ground" by rotating prior to Vr has a few safety downsides. One of them is that it makes tailstrikes more likely, as you'll have to carefully moderate the angle before lift occurs. Another is that it removes loading from the wheels more quickly, which extends the "awkward zone" in which the airplane is still rolling on the ground but has so little weight on the wheels that it will skid very easily. This can lead to aircraft being blown sideways off the runway since you can't yet roll into the wind. A somewhat less direct concern but a related one is ground effect lift. the aircraft can remain a short distance off the ground (roughly a wingspan of altitude) at lower speeds than it can actually "fly," due to ground effect. Smaller aircraft might routinely spend some time in ground effect gaining additional speed before they begin climbing, but airliners have so much thrust they usually rotate pretty directly to their climb speed. This makes it more of an issue though that if rotation occurs too far before Vy climb speed the ground effect period will be prolonged and increase the amount of time the aircraft spends at risk, flying but slow with poor control authority and too close to the ground to have much of a recovery opportunity. The ground is a pretty safe place to be, the sky is a pretty safe place to be, but that first couple thousand feet between the ground and the sky is rather hazardous and jetliners get out of it as quickly as possible.
wlonkly 4y ago
Based on my experiences reading aviation accident and safety reports, air transport pilots have a _lot_ of divorces.
- wkat4242 4y ago
  This could also mean divorces played a role in accidents of course. But it could also just be statistically true. Being in a position of power, surrounded by beautiful coworkers, lots of overnight hotel stays.. Without further investigation a conclusion can't be drawn though.

by basch 4y ago

pxmpxm 4y ago

>Interesting that someone cited divorce and sleep examples as emotional pleas, reassuring us they are only human. Huh? FAA spends a huge amount of time and energy focusing on human factors, tasks saturation rates and crew resource management. Nothing to do with with argumentum ad passiones, just prudent risk mitigation.

hooverd 4y ago
I thought a lot of safety thinking was built around acknowledging that humans don't do everything perfectly all the time.
- ddulaney 4y ago
  It does, and one class of mitigation is to improve automation, which airlines (and their regulators) do all the time. But another class of mitigations is to make the human less error-prone in the first place. This is especially important in preventing failures that were caused by improper management of the automation. Hence the emphasis on rest periods, training, and other mitigations on the human side. In the "swiss cheese" model, a disaster needs to slip through both the human's defenses and the automation's defenses to actually happen. It makes sense to improve both of those layers of defense against disaster, while acknowledging that humans will never be perfect. But at least they can be awake and knowledgable.
NovemberWhiskey 4y ago
Right. Literally every pilot in the US has been taught the IMSAFE mnemonic to assess fitness to fly, even before their first solo in a single-engine piston: Illness, Medication, Stress, Alcohol, Fatigue and Emotion.
basch 4y ago
I just don’t see how it fit the article. Unless they are surmising the pilots poorly sanityized the data going into the computer because they were having an off day.
- mynameisvlad 4y ago
  I mean, yes. That is literally exactly what they’re saying. The full quote: > …if there’s a glitch, naturally some pilot somewhere is going to miss it. “Not everyone gets eight hours sleep the night before. Someone is going through a divorce. Someone is not so sharp that morning,” he said. “The sanity check isn’t perfect every day of the week.”

deleted 4y ago

[deleted]

mnw21cam 4y ago

> The purpose of telling pilots thrust was to save money and fuel. No, it's more that using lower thrust during take off saves on engine wear and noise levels around the airport. It doesn't really have that big an impact on fuel use, at least that's not the primary purpose. The article concentrates far too much on the thrust setting. The important bit is the speed where the plane should be rotated to take off, which is known as V_r. That depends on the weight of the plane. On the takeoff roll, the pilots watch the airspeed indicators and pull back to lift off when that speed has been reached. If they have been told a V_r that is lower than it should be, then pulling back will rotate the aircraft without it taking off, and that's when you have this danger of the tail hitting the ground. When that happens, the plane must be inspected, because a tail strike has the potential to weaken the pressurised container that is the fuselage, and this could lead to an explosive burst and depressurisation when flying at high altitude. See https://en.wikipedia.org/wiki/China_Airlines_Flight_611 https://en.wikipedia.org/wiki/China_Airlines_Flight_611 for why this is a Bad Thing.

basch 4y ago
> saves on engine wear Which is saving on money
- seabird 4y ago
  I'm cracking up at the thought of an airline telling their pilots "fuck it, run em however hard you think you need to." There's a difference between dumping toxic waste into a river to save money and keeping a plane engine in safe operating conditions to save money.
phkahler 4y ago
It seems like a slower rotation might be useful, to wait until you feel it leave the ground before aiming higher. I'm sure there are reasons for the procedure as is.
- jcrawfordor 4y ago
  Trying to "force the airplane off the ground" by rotating prior to Vr has a few safety downsides. One of them is that it makes tailstrikes more likely, as you'll have to carefully moderate the angle before lift occurs. Another is that it removes loading from the wheels more quickly, which extends the "awkward zone" in which the airplane is still rolling on the ground but has so little weight on the wheels that it will skid very easily. This can lead to aircraft being blown sideways off the runway since you can't yet roll into the wind. A somewhat less direct concern but a related one is ground effect lift. the aircraft can remain a short distance off the ground (roughly a wingspan of altitude) at lower speeds than it can actually "fly," due to ground effect. Smaller aircraft might routinely spend some time in ground effect gaining additional speed before they begin climbing, but airliners have so much thrust they usually rotate pretty directly to their climb speed. This makes it more of an issue though that if rotation occurs too far before Vy climb speed the ground effect period will be prolonged and increase the amount of time the aircraft spends at risk, flying but slow with poor control authority and too close to the ground to have much of a recovery opportunity. The ground is a pretty safe place to be, the sky is a pretty safe place to be, but that first couple thousand feet between the ground and the sky is rather hazardous and jetliners get out of it as quickly as possible.

wlonkly 4y ago

Based on my experiences reading aviation accident and safety reports, air transport pilots have a _lot_ of divorces.

wkat4242 4y ago
This could also mean divorces played a role in accidents of course. But it could also just be statistically true. Being in a position of power, surrounded by beautiful coworkers, lots of overnight hotel stays.. Without further investigation a conclusion can't be drawn though.