julesmusician
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Runway Length And Boeing/Airbus FMS Warning

Sat Dec 24, 2005 9:01 am

Correct me if I am wrong, but no current airliner has a system that will tell you based on weight, speed and touchdown configuration whether, at the point you touchdown, that you actually have enough room to stop. It would appear that overruns on runways are featuring quite regularly in accident reports, and with the accuracy of GPS it should be fairly straight forward for the computers to know, as the wheels touch down exactly how much and where on the runway you are, and with an immediate calculation warn the pilot that he doesn't have enough space to land. Also if I am right there is actually no system that tells you by computations if you can manage to stop a take off roll at your speed safely, or you will have to lift off, by working out the distance to runway end.

Obviously all pilots calculate the Vref speeds, but when in the middle of a landing that hasn't quite worked out, or a take off that needs stopping, it seems it is still down to judgement a lot as to whether you can stop in time. Isn't it time technology took over?

J
African Civil Aviation Commission president "You don't want to fly out as a passenger and come back as cargo."
 
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zeke
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RE: Runway Length And Boeing/Airbus FMS Warning

Sat Dec 24, 2005 10:53 am

Quoting Julesmusician (Thread starter):
Correct me if I am wrong, but no current airliner has a system that will tell you based on weight, speed and touchdown configuration whether, at the point you touchdown, that you actually have enough room to stop. It would appear that overruns on runways are featuring quite regularly in accident reports, and with the accuracy of GPS it should be fairly straight forward for the computers to know, as the wheels touch down exactly how much and where on the runway you are, and with an immediate calculation warn the pilot that he doesn't have enough space to land.

The 380 has a system a little like this, you input the exit you want to get off the runway at, and will apply brake to meet that.

Quoting Julesmusician (Thread starter):
Also if I am right there is actually no system that tells you by computations if you can manage to stop a take off roll at your speed safely, or you will have to lift off, by working out the distance to runway end.

For takeoff thats is calculated before takeoff, normally in some office somewhere maybe even years before the takeoff. No guessing is done.

Quoting Julesmusician (Thread starter):
Obviously all pilots calculate the Vref speeds, but when in the middle of a landing that hasn't quite worked out, or a take off that needs stopping, it seems it is still down to judgement a lot as to whether you can stop in time. Isn't it time technology took over?

No, too many variables. Weather being the biggest one, visability, wind, runway surface, runway or taxiway works, other aircraft are just some factors.
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mandala499
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RE: Runway Length And Boeing/Airbus FMS Warning

Sat Dec 24, 2005 5:25 pm

Computers work on assumptions put into the variables, not experience...
Until computers use assumptions AND experience, it'll be the pilot's call... And experience isn't "easy programming"  Smile

Mandala499
When losing situational awareness, pray Cumulus Granitus isn't nearby !
 
jush
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RE: Runway Length And Boeing/Airbus FMS Warning

Sat Dec 24, 2005 8:24 pm

And the computer would have to know the EXACT runway conditions.
Wouldn'g have stopped the Atlas Jet in DUS from ovvershooting cause the condtitions changed last minute and i reckon unexpectable.

Regds
jush
There is one problem with airbus. Though their products are engineering marvels they lack passion, completely.
 
julesmusician
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RE: Runway Length And Boeing/Airbus FMS Warning

Sat Dec 24, 2005 8:44 pm

Yep but with something like ACARS data or METARS etc automatically uploaded to the FMS from your destination with braking action and condition of runway, again the automated process could occur. It would take a lot of programming, but it does seem that virtually everything else on the flight deck is automated except for possibly the most critical part of the flight, a late landing or rejected take off.
African Civil Aviation Commission president "You don't want to fly out as a passenger and come back as cargo."
 
Grbld
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RE: Runway Length And Boeing/Airbus FMS Warning

Sun Dec 25, 2005 1:02 am

Quoting Julesmusician (Reply 4):
Yep but with something like ACARS data or METARS etc automatically uploaded to the FMS...

Hi Jules, what the guys above mean is that sometimes THAT info is just not correct. Braking action can go from medium to poor in just 2 minutes. And the thing with measurements is that they're already out of date the second they are measured.

If you know the actual conditions, through datalink or tower reports or whatever, you know if you can make the landing or not. Only if those reports are inaccurate (which can happen in very bad weather), things might be worse than expected. And it's your call as a pilot, through experience and common sense to decide if you want to land or not. The computer cannot see that 1000 ft down the runway, there's a really bad patch of ice and you'll get into trouble.

Brings us to a more interesting matter: Would it do any good if the plane told you you're going off the end? Most likely, not. Just like in your car when the car tells you "Dude, you're gonna crash into that brick wall" and 2 seconds later, you crash into that brick wall  Smile

If you've got the reversers out, then you're committed to the landing, so if using maximum braking, you're still going off the end, then you're going off the end, nothing else you can do about it.

Very good question of yours, though!

Grbld
 
mandala499
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RE: Runway Length And Boeing/Airbus FMS Warning

Sun Dec 25, 2005 1:07 am

I don't think METAR can give sufficient info for runway conditions... Besides, how wet is wet? 0.1mm water level above asphalt? or 1cm of water above... Oh well, it'll be a different set of values, and an extra input...

Then we got airports in other parts of the worlds that don't even have good updates even for the METARs... Oh no... not even METARs, 24-hourly TAFs only! (Yeah see those Batam Airport TAFs giving "9999 SCT020" all day when U see WSSS TAF at "3000 OVC020 TSRA CB")... LOL

I am sure the FMS computations you want looks like a nice feature on paper, but operationally it could be an utter nightmare... I think it's best to assume "when rain use WET runway tables and aquaplaning possible" rather than computers...

Mandala499
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julesmusician
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RE: Runway Length And Boeing/Airbus FMS Warning

Sun Dec 25, 2005 1:49 am

The question is really if I bounce on landing for any reason and touchdown again I am going to be slightly perturbed/disturbed and wouldn't mind an instant check on how far down the road I have gone straight away. In my time I have been to various Greek islands and there was one occasion that the reversers were idle, brakes on and then all of a sudden the brakes went very firm and the reversers went max - as we reached the end of the runway and turned still moving my wing was well over the grass and red stop lights  Smile In low visibility it would be a very useful feature to have a runway landing space left voice or similar - or would it?!
African Civil Aviation Commission president "You don't want to fly out as a passenger and come back as cargo."
 
3201
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RE: Runway Length And Boeing/Airbus FMS Warning

Sun Dec 25, 2005 4:58 am

Quoting Zeke (Reply 1):
The 380 has a system a little like this, you input the exit you want to get off the runway at, and will apply brake to meet that.



Quoting Grbld (Reply 5):
Brings us to a more interesting matter: Would it do any good if the plane told you you're going off the end? Most likely, not. Just like in your car when the car tells you "Dude, you're gonna crash into that brick wall" and 2 seconds later, you crash into that brick wall

Yeah, on the A380 if you program in "end of runway" and you won't make it, it explosively deflates all the tires.

In all seriousness -- takeoff/landing caluclations are indeed very complicated, take all sorts of things into account, but given that many aircraft have the calcs available anyway (either in an installed EFB or some kind of laptop tool) it seems like you could have some kind of gross warning ("you might be in big trouble here, dude" vs. "looks like you have 3000ft to spare") -- but presumably pilots with some experience into that runway with that aircraft would have the same kind of idea on their own, and it's not clear how much better the calculation would be. It would be pretty cool, though, with the artificial vision tools that are in an experimental stage, to have the pilot see green, yellow, and red regions of the runway through a helmet or on a HUD.  Smile Anyone know if that's actually something anyone is working on? All I've ever seen are special-use airspace and special procedures.

Quoting Mandala499 (Reply 6):
I don't think METAR can give sufficient info for runway conditions... Besides, how wet is wet? 0.1mm water level above asphalt? or 1cm of water above... Oh well, it'll be a different set of values, and an extra input...

Presumably you could get decent info from the ground on approach, including possibly the contamination depth. If nothing else, they give reports on braking action, and braking action is available either instead of, or in addition to, contamination depth on some performance computation modules (it's part of the SCAP standard).
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blrBird
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RE: Runway Length And Boeing/Airbus FMS Warning

Sun Dec 25, 2005 10:10 am

Quoting Mandala499 (Reply 2):
And experience isn't "easy programming"



Quoting Jush (Reply 3):
And the computer would have to know the EXACT runway conditions.

Pardon my ignorance(not from aviation background), theoretically/technologically this can be achieved but to do that the system will have to know in real time, data (dry/wet/icy etc...) of current conditions.
Such a system should have of info on things like length of runway, prevailing wind conditions, runway surface characteristics, type of aircraft, landing mass, position of touch down on runway and etc..

You can build a robust system that can inform a pilot within seconds on touchdown about the possible scenarios, still this cannot replace pilots own experience! Can be handy tool.

How much of today's airports(most modern) runways are wired? Is there such a thing like that?

Off topic I have a question..
What is the advantage/disadvantage of having 150 or 200 Ft width runways?
Some new airports under construction are choosing one over the other, is it purely economics?
from star dust....
 
2H4
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RE: Runway Length And Boeing/Airbus FMS Warning

Sun Dec 25, 2005 1:44 pm



On the topic of pilot experience vs computer capabilities....what kind of wx mins apply to UAV's? Are UAV's able to negotiate the kinds of wx and runway conditions that manned aircraft routinely deal with?




2H4


Intentionally Left Blank
 
Grbld
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RE: Runway Length And Boeing/Airbus FMS Warning

Sun Dec 25, 2005 7:25 pm

Quoting BlrBird (Reply 9):
...theoretically/technologically this can be achieved but to do that the system will have to know in real time, data (dry/wet/icy etc...) of current conditions.
Such a system should have of info on things like length of runway, prevailing wind conditions, runway surface characteristics, type of aircraft, landing mass, position of touch down on runway and etc..

Well, it cannot, really. When things start to get hairy, we're mostly talking about slippery or slushy runways that severly impact your braking action (or friction coefficient). These factors are always measured by an airport authorities car driving up the runway and performing tests.

As I said earlier, in heavy snowfall, frost or freezing precipitation, braking action can change dramatically within just a minute. You can go from within the limits to well over the limits.

Secondly, you'd have to have actual conditions on every single patch of runway. Braking action can be one level at the beginning, but different from the middle or the end of the runway.

Brings us back to my original statement: Does it really help you? Does it do any good to have a sign come up that says "you're screwed?"

The thing is that (as is so often the case in aviation) when things start getting really hairy and you could benefit from a warning system, it's then that measurements start getting really inaccurate as well.
It's just like having a nice modern airliner with all kinds of advanced systems that take a lot of work out of your hands and make life easier: It's when things start going really wrong that all these nice features don't work anymore and it's you, the human, that has to bring things to a good ending.

Quoting 2H4 (Reply 10):
what kind of wx mins apply to UAV's?

Not an expert on UAVs at all, but these things are relatively very light and won't have much problems landing on short runways (or maybe even straight patches of desert, grass or lake beds). They're most likely a lot stronger (incurring g-forces) structurally than most airliners. A simple Cessna 150 is structurally much stronger than an airliner and I expect a UAV to be even tougher. So ending a bad crosswind approach with a hard and bumpy landing shouldn't be a problem.

Grbld
 
julesmusician
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RE: Runway Length And Boeing/Airbus FMS Warning

Sun Dec 25, 2005 7:33 pm

http://www.b737.org.uk/hgs_cat3at50ft.jpg

Here is the Head Up Display for the 737 in CAT III mode, that could be used to include runway length left, although I don't believe it does at the moment...
African Civil Aviation Commission president "You don't want to fly out as a passenger and come back as cargo."
 
mandala499
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RE: Runway Length And Boeing/Airbus FMS Warning

Mon Dec 26, 2005 12:14 am

These factors are always measured by an airport authorities car driving up the runway and performing tests.

Sorry if I sound rather blunt... but not in my part of the world! and add that with....

it's then that measurements start getting really inaccurate as well.

And knowing how airports here do their work... I'd say putting that in place here tomorrow would yield more trouble than benefits. Although in US and Europe, the major airports can get this running... though how much extra cost would be incurred, I dunno...

Mandala499
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CosmicCruiser
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RE: Runway Length And Boeing/Airbus FMS Warning

Mon Dec 26, 2005 12:48 am

We have RAAS(Runway Awareness and Advisory System) being installed on our MD-11s. Though it does not tell you if you CAN stop on the remaining runway it does give aural callouts of runway remaining once you pass the runway midpoint and are going over 40 kts. This could certainly get your attention and perhaps cause earlier actions to prevent going off the end.
Another function of RAAS is to warn the crew when approaching a runway either at the end or any intersecting taxiway to prevent an incursion(obviously for low vis taxi).
 
PhilSquares
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RE: Runway Length And Boeing/Airbus FMS Warning

Mon Dec 26, 2005 12:58 am

Just to add my humble opinion in this discussion. If I understand the question correctly, the issue is using the FMS for calculation of landing stopping ability and conversely, takeoff performance and stopping distance.

Quite frankly, the FMC in the current generation of Airbus and Boeing don't have the computing power and lack the memory required to make it happen. The FMS are really extremely slow (when compared to today's PCs) and as a result, they're very low power which also results in less heat and longer life. They just weren't designed for that.

Plus, I wouldn't want to figure out a system to calculate braking coefficient that is actually on the runway versus what it is planned to be.
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Grbld
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RE: Runway Length And Boeing/Airbus FMS Warning

Mon Dec 26, 2005 5:01 am

The "brand new" FMCs on the 737NG and 777 (with the colour TFT screens) probably have less computing power than your cell phone. They have old 20 MHz CPUs. I remember that our 757s were upgraded to a whopping 1 MB (yes, that's one megabyte) of storage memory (standard was just 256K).

Next gen systems such as in the A380 and 787 will probably have MUCH more processing power. Bizjets are usually a generation ahead of the airliners and the new systems in the G550 (formerly known as GV) are pretty impressive.

Quoting Mandala499 (Reply 13):
but not in my part of the world!

Hehe, I bet you get lots of snowstorms over there!

Grbld
 
AAR90
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RE: Runway Length And Boeing/Airbus FMS Warning

Mon Dec 26, 2005 7:21 am

Quoting Julesmusician (Reply 12):
Here is the Head Up Display for the 737 in CAT III mode, that could be used to include runway length left, although I don't believe it does at the moment...

AA 738 HUD display has a runway remaining countdown. You input/verify runway length via FMS and the countdown begins at 50' RA using groundspeed. Nice to have, but nothing extraordinarily useful.
*NO CARRIER* -- A Naval Aviator's worst nightmare!
 
mandala499
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RE: Runway Length And Boeing/Airbus FMS Warning

Tue Dec 27, 2005 11:38 pm

Hehe, I bet you get lots of snowstorms over there!

No, but we have many airports without instruments/equipment to calculate braking coefficients... Then also airports where the rubber deposits are only cleaned after an overrun in rain season (like... err this time of year)... Plus the infamous WAAA/UPG ice skating rink used as a runway (excuse the pun)... that runway can be slippier than a snowed up Norwegian runway in winter... Then... "XXXX tower, any standing water on the runway?" "Don't know, runway wet, cleared to land, let me know if you see standing water on runway on landing roll and... watch out for potholes."

Mandala499
When losing situational awareness, pray Cumulus Granitus isn't nearby !

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