I've been in a helicopter hovering over Heathrow airport where you can see the lights from the line of planes coming in to land every 45 seconds that looks like it goes off to infinity. Whatever technique they use there seems to work.
Taking a quick look at Heathrow approach, looks like runway is clear of the first plane landing when the following plane is 1-2 miles out and around 500ft.
https://www.heathrow.com/company/local-community/noise/opera...
It sounds to me like far too many critical safety decisions are being made with an eye on money rather than safety. There were reports warning that Fukushima wasn't safe in case of a tsunami, but the company in charge of the plant decided to ignore that. Deep Water was caused by cost cuts. The Boeing 737 Max was made for financial reasons, fixing a fundamental hardware problem in software.
Safety engineers clearly need a bigger say in these things.
Everything is a money/greed problem if you look at it through the lens of motivated reasoning.
The usage of infrastructure is mutually beneficial. The airport, the various businesses operating at it, the customers, everyone benefits per flight. Likewise you want to make that infrastructure get used as much as possible.
There must be something the americans do wrong, somewhere, and optimisation cannot be an excuse for mediocrity. Do it fast and safe or do it slow and safe: the passengers can wait, or build their own planes and airports if they think they can do better.
There’s 16M flights per year, so saving 5 minutes each is 80M minutes, which corresponds to 160 years.
A plane crash will kill about 160 people; so if one happens every twenty years, then we’ll have saved lives if the average age is over 50 (within 20 years of natural death) and lost lives otherwise.
Personally, seems a bad gamble.
I don't have an opinion one way or the other on the "optimization", just pointing out the missing step in the math
Do you take that deal? Why or why not?
I couldn’t find any crashes listed on Wikipedia in the past 20 years that could be attributed to two planes being directed occupy a runway at the same time.
>> It sounds to me like far too many critical safety decisions are being made with an eye on money rather than safety.
Major Airports are often locked in to the Physical foot print either due to Geography or other factors. Sure you can just "move the airpoirt" but then you have the NIMBY problem where everyone wants an airport close by, but never near by....
And if you want to simplistically run it all down to "money" well at that point everything in a money problem, so for like NYC they could turn spend billions or Trillions to turn midtown into a big airport but that seem rather unrealistic.
This narrative that came out of COVID of "if it saves just one life" is a bit ridiculous imo, and not at all practical
I don't know the analysis for the multiple clearance on runways on the US (honestly, it's the first time I hear about it). What I know is that the US has many complex risk analysis that my country (3rd largest aviation area on the world, after the US and EU) doesn't have enough data to replicate. That leads to plenty of policies that we can't actually understand the reasoning.
You're ignoring the core truth of the comment you're replying to: Scarcity exists. There is no way to have it all; there are only compromises. Simply walking is dangerous because you could fall. We could all go back to being infants* crawling on the floor if we wanted to be safer. But we won't. Making more compromises in the name of safety has to be justified. Planes will never be perfectly safe. That is okay.
Also, I would disagree that engineering time is more valuable than human life. Engineering time should be spent on safeguarding human life. Otherwise, what are we even doing?
[1] https://en.m.wikipedia.org/wiki/Signaling_of_the_New_York_Ci...
You imagine that the something else is something you don't care about or think doesn't matter - like executive compensation. Well, you're like everyone else - we all think we should be running the country.
[1]https://www.cnbc.com/2019/02/13/colgan-air-crash-10-years-ag... [2]https://en.wikipedia.org/wiki/List_of_accidents_and_incident...
At least it would have forced the controller to verify that SW is clear of the runway before clearing fedex.
As it was, it cleared both and then did something else until the situation was over.
Not sure what is has to do with the initial problem that spawned the transparent mea culpa though, which is due to a sort of reckless optimism and an inability to look abroad for better ideas. I think they call it "American Exceptionalism" or some such there ? Even your answer seems to be that you fucked up but at least you're not as bad as ... the French ? What ? :D
If you bothered to comprehend what I wrote I'm pretty much advocating the opposite of American exceptionalism. The accident rate is pretty close across the first world. Why would the close call rate be substantially different?
Thank god aviation policy isn't dictated by people like you who have an ideological bone to pick.
Seems like this would be a good trigger to switch temporarily to a more pessimistic strategy. (Caveat: I don't know anything about aviation.)
Multiple landing planes are allowed on the same runway surface at the same time in the daytime as in Oshkosh arrivals, but also a Category I (light single) can be cleared to land if the Category I or II aircraft to follow will be 3000 feet from the threshold, a Cat II (light twin) behind a I or II with 4500 feet of separation.
In Europe, I have heard, you can't operate CAT III ILS (or even maybe CAT II) when your ground radar is inop.
It seems that in Austin they don't even have a ground radar. How the hell is CAT III a thing there?
My understanding was that the word "cleared" was to be avoided when you aren't actually cleared to land/take off, and the correct wording was now "continue approach runway 08".
There has been a decent amount of study of the cognitive interpretation of exact wordings, resulting in a standardised phrasing that avoids misinterpretation. It's a good thing. Using the word "cleared" could easily cause a lazy/tired/overloaded pilot over a noisy channel to think they are cleared to land.
Also the word "takeoff" is protected, I believe it can only be said within giving and reading back a takeoff clearance. Everywhere else it has to be "departure".
* ONE vehicle of any kind!
You can't use the runway because there's a bloody great Volvo in the middle of it, because I put the bloody great Volvo there, because I'm picking up bits of the last guy's wheel spat that fell off, because I don't want to have to write a long long tale about how your prop got chipped.
True story.
Given how advanced ILS is nowadays you could probably automate all of this - if the plane taking off isn't committed to takeoff (traveling at V2) by the time the landing aircraft reaches decision altitude, an automatic go-around is issued. Basically treat the runway as a "control zone" like trains do, and if the plane on the runway hasn't "cleared the zone" (by whatever definition) then the landing aircraft can't enter the zone.
Certainly that's something that could be conveyed as part of the ILS data at least. Maybe it's undesirable to automate it in the sense of the automation causing more problems (more aborts = more chances for something to go wrong, although the assertion is that by V2 you're committed and by decision altitude you can still abort safely, so this all fits inside the "theory of movements") but you can at least let the landing plane know at decision altitude that there's an aircraft still on the runway. Sort of a "green = runway clear, yellow = committed traffic, yellow bars = moving but uncommitted traffic, red = runway occupied/clearance not granted" type indicator perhaps.
Or maybe if the tower can't visually/instrument confirm execution of movements, the pilot on takeoff has to verbally confirm commit before the landing clearance can be granted. Then it just becomes something specific to zero-visibility operations.
It really seems like there should be some change in how movements are handled/clearances are issued. Maybe we don't need to go to full "one clearance at a time" all the time, but it certainly seems like there should be some tighter rules if the tower can't independently confirm movements are being executed, and perhaps convey that information to the pilot as well (although again, I know that pilots are already information-overloaded, but "is there someone on my runway" is seemingly pretty important and straightforward info).
But, if an arriving aircraft is still on the runway, a controller can clear a departing aircraft for takeoff if there will be adequate separation when the departing aircraft starts takeoff roll (i.e., the arriving aircraft will be clear of the runway at that point).
[1] 7110.65 3-9-5 Anticipating Separation
In ICAO phraseology, "cleared to land runway 08" is allowed. Further:
> If the runway is obstructed when the aircraft reports ‘final’, but it is expected to be available in good time for the aircraft to make a safe landing, the controller will delay landing clearance by issuing an instruction to ‘continue approach’.
* https://www.skybrary.aero/sites/default/files/bookshelf/115....
When the approaching plane is cleared then there is no allowance for anyone and anything to be on the runway.
So if there is a departing plane waiting on the runway or someone crossing then the approaching plane is given "cleared approach runway 08" but never "cleared to land". Which also means that if you are piloting the landing plane then at your decision height you have to go around.
Also when someone is cleared to land no-one can be given a permission to enter the runway.
There is one clearance that kinda-sorta allows which is "BEHIND landing Boeing 737, line up and wait BEHIND". It intentionally has "BEHIND" before and after the call to be extra clear that the waiting pilot has to confirm that the plane has passed their nose and they can enter the runway while the landing plane is on rollout. But that plane can not be given a takeoff clearance before the plane on the rollout has exited the runway.
We were told that the americans do it differently and I've always found it dangerous.