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SRQfoxtrot
Topic Author
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Rapid Exit Taxiway / 777-8/9 folding wing tips (FWT)

Tue Apr 27, 2021 1:26 am

Would anyone care to comment on the work load issues?
Here are some details from Boeing performed studies to ensure that the FWT will be folded prior to entering the parallel taxiway.  
Transition of FWT to fold begins at 50k ground speed. 
FWT are folded prior to entering the parallel taxiway. 
FWT are folded when the aircraft reaches 14 kt ground speed


Link to PDF of Study.
https://www.icao.int/EURNAT/Other%20Meetings%20Seminars%20and%20Workshops/ICAO%20EUR%20NAT%20NCLB%20Technical%20Assistance%20Programme%20-%20Workshops%20on%20Aerodrome%20Certification%20ICAO%20EURNAT%20AGA%2018001/ICAO%20EURNAT%20NCLB%20TAP%20AGA%2018001%20Workshop%20on%20Aerodrome%20Certification%203/Session%2006.pdf
 
BoeingGuy
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Re: Rapid Exit Taxiway / 777-8/9 folding wing tips (FWT)

Tue Apr 27, 2021 4:00 am

The folding begins automatically at 50 knots during landing rollout. What exactly are you asking?

The FWT system will be very thoroughly tested both from a design standpoint and workload. It will have to comply with the latest most stringent Human Factors regulation. That compliance process is rigorous.

Same is true for all other new systems on the 777-9.
 
BrianDromey
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Re: Rapid Exit Taxiway / 777-8/9 folding wing tips (FWT)

Tue Apr 27, 2021 12:13 pm

I guess the real question if there would be a failure is what routes around the airfield are available. There are presumably taxiways that would become unavailable to the 77X in the event of a failure? No different to the A380 really, but there are many issues with the A380 and its airfield restrictions according to many armchair pilots here...
 
Weatherwatcher1
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Joined: Sun Mar 03, 2019 5:14 pm

Re: Rapid Exit Taxiway / 777-8/9 folding wing tips (FWT)

Tue Apr 27, 2021 1:06 pm

BrianDromey wrote:
I guess the real question if there would be a failure is what routes around the airfield are available. There are presumably taxiways that would become unavailable to the 77X in the event of a failure? No different to the A380 really, but there are many issues with the A380 and its airfield restrictions according to many armchair pilots here...


The failure condition is addressed in the presentation

FWT system does not automatically issue the fold command (autofold failure)
• Flt Crew will receive WINGTIPS POSITION caution message on the EICAS + Master Caution Light + Aural Beeper.
• Flight crew will action the Folding Wing Tip Pilot Control Module lever manually
• WINGTIPS DRIVE caution message on the EICAS + master caution light + aural beeper, if failure continues.
• Flight crew informs ATC and Airport’s non normal FWT operational plan is activated.
 
dtw2hyd
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Re: Rapid Exit Taxiway / 777-8/9 folding wing tips (FWT)

Tue Apr 27, 2021 1:07 pm

BoeingGuy wrote:
The folding begins automatically at 50 knots during landing rollout.

What exactly are you asking?


Is there a well labelled off-switch or manual override of some sort?
Does it read speed from more than one source?
 
Weatherwatcher1
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Re: Rapid Exit Taxiway / 777-8/9 folding wing tips (FWT)

Tue Apr 27, 2021 1:10 pm

dtw2hyd wrote:
BoeingGuy wrote:
The folding begins automatically at 50 knots during landing rollout.

What exactly are you asking?


Is there a well labelled off-switch or manual override of some sort?
Does it read speed from more than one source?


The folding wingtip mechanism is deferrable meaning that the tip can be locked in the extended position and the airplane considered Cat F for taxiway clearances

Air ground system and speed are part of the logic. The air ground system has redundancy built in to it with multiple landing gear proximity sensors used to determine if there are weight on the wheels. Given the criticality of the air ground logic for other systems (such as autospeedbrake and RTO autobrakes) it has multiple redundancies.
Last edited by Weatherwatcher1 on Tue Apr 27, 2021 1:12 pm, edited 1 time in total.
 
aviatorcraig
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Re: Rapid Exit Taxiway / 777-8/9 folding wing tips (FWT)

Tue Apr 27, 2021 1:12 pm

Amazingly, we have managed to raise flaps at the end of the landing rollout for years! Even without automation, maybe these new fangled wing-tip thingies could become... a checklist item !! :o
 
Weatherwatcher1
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Re: Rapid Exit Taxiway / 777-8/9 folding wing tips (FWT)

Tue Apr 27, 2021 1:15 pm

aviatorcraig wrote:
Amazingly, we have managed to raise flaps at the end of the landing rollout for years! Even without automation, maybe these new fangled wing-tip thingies could become... a checklist item !! :o


I’m not sure how many times you’ve done walk arounds and seen problems, but I’ve done plenty after a flight and seen the pilots incorrectly leaving the airplane out of configuration. Strobes on at the gate, speed brakes up, flaps down, etc. if this was a checklist item, I have no doubt we’d have pilots forget and a Big Crunch when a plane pulled into a gate.
 
N757ST
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Re: Rapid Exit Taxiway / 777-8/9 folding wing tips (FWT)

Tue Apr 27, 2021 1:18 pm

Weatherwatcher1 wrote:
aviatorcraig wrote:
Amazingly, we have managed to raise flaps at the end of the landing rollout for years! Even without automation, maybe these new fangled wing-tip thingies could become... a checklist item !! :o


I’m not sure how many times you’ve done walk arounds and seen problems, but I’ve done plenty after a flight and seen the pilots incorrectly leaving the airplane out of configuration. Strobes on at the gate, speed brakes up, flaps down, etc. if this was a checklist item, I have no doubt we’d have pilots forget and a Big Crunch when a plane pulled into a gate.



Oh I don’t know, maybe require a wing walker to alleviate that hole in the Swiss cheese?
 
N757ST
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Re: Rapid Exit Taxiway / 777-8/9 folding wing tips (FWT)

Tue Apr 27, 2021 1:22 pm

Or even an ecam or master warning of some sort after WOW + a time factor, or if flaps are not retracted and wingtips are still not retracted. There seem to be a lot of ways to mitigate that risk. As wingspans increase over time with many frames I’d expect folding wingtips to be industry common, and with modern technology it should be pretty darn easy to manage the risk. Will someone clip another tail, yeah probably and then that will get emphasized again via internet based training, annual recurrent, and email.
 
Weatherwatcher1
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Re: Rapid Exit Taxiway / 777-8/9 folding wing tips (FWT)

Tue Apr 27, 2021 1:32 pm

N757ST wrote:
Weatherwatcher1 wrote:
aviatorcraig wrote:
Amazingly, we have managed to raise flaps at the end of the landing rollout for years! Even without automation, maybe these new fangled wing-tip thingies could become... a checklist item !! :o


I’m not sure how many times you’ve done walk arounds and seen problems, but I’ve done plenty after a flight and seen the pilots incorrectly leaving the airplane out of configuration. Strobes on at the gate, speed brakes up, flaps down, etc. if this was a checklist item, I have no doubt we’d have pilots forget and a Big Crunch when a plane pulled into a gate.



Oh I don’t know, maybe require a wing walker to alleviate that hole in the Swiss cheese?


Automation is better in my opinion. It is far more reliable. Automation in the flight control system is nothing new. EICAS lights up like a Christmas tree if the airplane is forced into air mode while on the ground for example during maintenance. There’s no shortage of issues that light up if the airplane inadvertently goes into ground ode while in the air. I don’t know if it has ever happened due to redundancy
 
Weatherwatcher1
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Re: Rapid Exit Taxiway / 777-8/9 folding wing tips (FWT)

Tue Apr 27, 2021 1:33 pm

N757ST wrote:
Or even an ecam or master warning of some sort after WOW + a time factor, or if flaps are not retracted and wingtips are still not retracted. There seem to be a lot of ways to mitigate that risk. As wingspans increase over time with many frames I’d expect folding wingtips to be industry common, and with modern technology it should be pretty darn easy to manage the risk. Will someone clip another tail, yeah probably and then that will get emphasized again via internet based training, annual recurrent, and email.


What’s wrong with automation here? Air ground logic is used in dozens of places throughout the airplane
 
dtw2hyd
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Re: Rapid Exit Taxiway / 777-8/9 folding wing tips (FWT)

Tue Apr 27, 2021 1:57 pm

Weatherwatcher1 wrote:
aviatorcraig wrote:
Amazingly, we have managed to raise flaps at the end of the landing rollout for years! Even without automation, maybe these new fangled wing-tip thingies could become... a checklist item !! :o


I’m not sure how many times you’ve done walk arounds and seen problems, but I’ve done plenty after a flight and seen the pilots incorrectly leaving the airplane out of configuration. Strobes on at the gate, speed brakes up, flaps down, etc. if this was a checklist item, I have no doubt we’d have pilots forget and a Big Crunch when a plane pulled into a gate.


All the more important design is tight. Humans do make mistakes.

Not looking forward to reading 10,000 a.net posts some ground/flight crew forgot to remove pitot tube cover or didn't notice wasp net, wrong air speed and tips folded.

Yes one can blame the crew or anticipate and have a reasonably decent design.
 
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Polot
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Re: Rapid Exit Taxiway / 777-8/9 folding wing tips (FWT)

Tue Apr 27, 2021 2:02 pm

dtw2hyd wrote:
Weatherwatcher1 wrote:
aviatorcraig wrote:
Amazingly, we have managed to raise flaps at the end of the landing rollout for years! Even without automation, maybe these new fangled wing-tip thingies could become... a checklist item !! :o


I’m not sure how many times you’ve done walk arounds and seen problems, but I’ve done plenty after a flight and seen the pilots incorrectly leaving the airplane out of configuration. Strobes on at the gate, speed brakes up, flaps down, etc. if this was a checklist item, I have no doubt we’d have pilots forget and a Big Crunch when a plane pulled into a gate.


All the more important design is tight. Humans do make mistakes.

Not looking forward to reading 10,000 a.net posts some ground/flight crew forgot to remove pitot tube cover or didn't notice wasp net, wrong air speed and tips folded.

Yes one can blame the crew or anticipate and have a reasonably decent design.

If things are so bad that the plane thinks you are only going 50 knots when you are flying then the wingtips folding are the least of your worries. A speed discrepancy that severe should also be noticed during the take off roll.

I would also expect weight on gear to be a requirement too. The speed check is likely just the final trigger to begin folding, since at 50 knots you are unlikely to reject landing and go around.
 
Weatherwatcher1
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Re: Rapid Exit Taxiway / 777-8/9 folding wing tips (FWT)

Tue Apr 27, 2021 4:34 pm

Polot wrote:
dtw2hyd wrote:
Weatherwatcher1 wrote:

I’m not sure how many times you’ve done walk arounds and seen problems, but I’ve done plenty after a flight and seen the pilots incorrectly leaving the airplane out of configuration. Strobes on at the gate, speed brakes up, flaps down, etc. if this was a checklist item, I have no doubt we’d have pilots forget and a Big Crunch when a plane pulled into a gate.


All the more important design is tight. Humans do make mistakes.

Not looking forward to reading 10,000 a.net posts some ground/flight crew forgot to remove pitot tube cover or didn't notice wasp net, wrong air speed and tips folded.

Yes one can blame the crew or anticipate and have a reasonably decent design.

If things are so bad that the plane thinks you are only going 50 knots when you are flying then the wingtips folding are the least of your worries. A speed discrepancy that severe should also be noticed during the take off roll.

I would also expect weight on gear to be a requirement too. The speed check is likely just the final trigger to begin folding, since at 50 knots you are unlikely to reject landing and go around.


There are many independent pieces of logic that can be used. Airplane on ground, thrust below 50% (or reversers deployed), speed below 50 knots, etc. I don’t see a problem building enough logic to ensure the probability of the tips retracting in flight being less than 1 in a Billion.
 
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DL717
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Re: Rapid Exit Taxiway / 777-8/9 folding wing tips (FWT)

Tue Apr 27, 2021 4:48 pm

A failure to retract poses two problems:

Lack of sufficient Taxiway separation (Safety Issue) - The purpose of the folding tips is to allow the aircraft (ADG-VI) to operate at an ADG-V facility.
Lack of gate availability if there are no ADG-VI gates available (Turn issue) - Or the ability to actually get to the gate in the first place due to taxiway/taxilane clearance issues.

A third issue is runway occupancy time while the wingtips drop into position on the runway. Taxiway clearance at an ADG-V facility is likely insufficient so the drop would need to occur on the runway.
 
Cubsrule
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Re: Rapid Exit Taxiway / 777-8/9 folding wing tips (FWT)

Tue Apr 27, 2021 5:47 pm

DL717 wrote:
A failure to retract poses two problems:

Lack of sufficient Taxiway separation (Safety Issue) - The purpose of the folding tips is to allow the aircraft (ADG-VI) to operate at an ADG-V facility.
Lack of gate availability if there are no ADG-VI gates available (Turn issue) - Or the ability to actually get to the gate in the first place due to taxiway/taxilane clearance issues.

A third issue is runway occupancy time while the wingtips drop into position on the runway. Taxiway clearance at an ADG-V facility is likely insufficient so the drop would need to occur on the runway.


This is all correct, but the other layer to consider is how frequently the aircraft will operate into an ADG-V facility. We could imagine scenarios where the taxiways are mostly or exclusively ADG-VI-sized but there aren't enough ADG-VI gates or where the taxiways are tight but there are plenty of well-spaced gates available. If the former scenario is more often true and the only consequence of not getting the wing tips folded is a sit in the penalty box for an ADG-VI gate, that's annoying but not a safety issue.
 
BoeingGuy
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Re: Rapid Exit Taxiway / 777-8/9 folding wing tips (FWT)

Tue Apr 27, 2021 11:56 pm

Polot wrote:
dtw2hyd wrote:
Weatherwatcher1 wrote:

I’m not sure how many times you’ve done walk arounds and seen problems, but I’ve done plenty after a flight and seen the pilots incorrectly leaving the airplane out of configuration. Strobes on at the gate, speed brakes up, flaps down, etc. if this was a checklist item, I have no doubt we’d have pilots forget and a Big Crunch when a plane pulled into a gate.


All the more important design is tight. Humans do make mistakes.

Not looking forward to reading 10,000 a.net posts some ground/flight crew forgot to remove pitot tube cover or didn't notice wasp net, wrong air speed and tips folded.

Yes one can blame the crew or anticipate and have a reasonably decent design.

If things are so bad that the plane thinks you are only going 50 knots when you are flying then the wingtips folding are the least of your worries. A speed discrepancy that severe should also be noticed during the take off roll.

I would also expect weight on gear to be a requirement too. The speed check is likely just the final trigger to begin folding, since at 50 knots you are unlikely to reject landing and go around.


The 50 knots trigger uses Ground Speed not Air Speed. The Earth Reference System (aka IRS) provides Ground Speed. That system has a very high reliability and isn’t subject to stuff like icing. The 777-9 and 787 have four IRS units, so very high redundancy.

There are several layers of protection to prevent you from taking off with the Wingtips folded. Not only will you get an alert, then another alert if you continue, but the Autothrottle is inhibited if the Wingtips aren’t up. TO/GA won’t engage and you get the Warning Siren. Then you get a voice aural if you try to continue.

There are published procedures for things like them failing to retract after landing. One step is to notify ATC, of course.

The FWT system is being extremely well scrutinized in every aspect. Anything changed from the 777-300ER has to comply with the new CFR 25.1302, which is rigorous to show compliance to.
 
BoeingGuy
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Re: Rapid Exit Taxiway / 777-8/9 folding wing tips (FWT)

Wed Apr 28, 2021 12:16 am

Weatherwatcher1 wrote:
Polot wrote:
dtw2hyd wrote:

All the more important design is tight. Humans do make mistakes.

Not looking forward to reading 10,000 a.net posts some ground/flight crew forgot to remove pitot tube cover or didn't notice wasp net, wrong air speed and tips folded.

Yes one can blame the crew or anticipate and have a reasonably decent design.

If things are so bad that the plane thinks you are only going 50 knots when you are flying then the wingtips folding are the least of your worries. A speed discrepancy that severe should also be noticed during the take off roll.

I would also expect weight on gear to be a requirement too. The speed check is likely just the final trigger to begin folding, since at 50 knots you are unlikely to reject landing and go around.


There are many independent pieces of logic that can be used. Airplane on ground, thrust below 50% (or reversers deployed), speed below 50 knots, etc. I don’t see a problem building enough logic to ensure the probability of the tips retracting in flight being less than 1 in a Billion.


The required probability is far less than 1 in a Billion. It’s 1 in 1,000,000,000 flight hours for something deemed potentially catastrophic. As I understand it, the concern with a wingtip being folded in flight is not so much aerodynamic performance. The airplane can fly without it. The issue is the airstream loading breaking off a wingtip when it’s folded and potentially hitting the empennage.

Besides 50 knots groundspeed, the logic does look at other things too, as you suggest. Looks at multiple parameters that indicate you either landed, or did an RTO from above 85 knots.

In order to meet that 1x10e-9 probability, you can be assured the logic and data sources are robust.
 
BoeingGuy
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Re: Rapid Exit Taxiway / 777-8/9 folding wing tips (FWT)

Wed Apr 28, 2021 12:29 am

BoeingGuy wrote:
Polot wrote:
dtw2hyd wrote:

All the more important design is tight. Humans do make mistakes.

Not looking forward to reading 10,000 a.net posts some ground/flight crew forgot to remove pitot tube cover or didn't notice wasp net, wrong air speed and tips folded.

Yes one can blame the crew or anticipate and have a reasonably decent design.

If things are so bad that the plane thinks you are only going 50 knots when you are flying then the wingtips folding are the least of your worries. A speed discrepancy that severe should also be noticed during the take off roll.

I would also expect weight on gear to be a requirement too. The speed check is likely just the final trigger to begin folding, since at 50 knots you are unlikely to reject landing and go around.



I had an error in a previous post that was too late to edit. I meant:

the Autothrottle is inhibited if the Wingtips aren’t DOWN and locked.
 
atcdan
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Re: Rapid Exit Taxiway / 777-8/9 folding wing tips (

Wed Apr 28, 2021 5:53 am

BrianDromey wrote:
I guess the real question if there would be a failure is what routes around the airfield are available. There are presumably taxiways that would become unavailable to the 77X in the event of a failure? No different to the A380 really, but there are many issues with the A380 and its airfield restrictions according to many armchair pilots here...


Not an armchair pilot but ADG-VI restrictions do play a huge role in airport operations. Just this morning there was a B748F waiting over an hour for their gate at LAX, and they had to hold on side of the airport because there are literally only about 8 taxiways they can use here, and one runway currently they can depart.

We have discussed at work informally just how we will handle the B779 when they start flying, I’m sure it’ll be interesting.
 
kalvado
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Re: Rapid Exit Taxiway / 777-8/9 folding wing tips (FWT)

Wed Apr 28, 2021 12:03 pm

BoeingGuy wrote:
Weatherwatcher1 wrote:
Polot wrote:
If things are so bad that the plane thinks you are only going 50 knots when you are flying then the wingtips folding are the least of your worries. A speed discrepancy that severe should also be noticed during the take off roll.

I would also expect weight on gear to be a requirement too. The speed check is likely just the final trigger to begin folding, since at 50 knots you are unlikely to reject landing and go around.


There are many independent pieces of logic that can be used. Airplane on ground, thrust below 50% (or reversers deployed), speed below 50 knots, etc. I don’t see a problem building enough logic to ensure the probability of the tips retracting in flight being less than 1 in a Billion.


The required probability is far less than 1 in a Billion. It’s 1 in 1,000,000,000 flight hours for something deemed potentially catastrophic. As I understand it, the concern with a wingtip being folded in flight is not so much aerodynamic performance. The airplane can fly without it. The issue is the airstream loading breaking off a wingtip when it’s folded and potentially hitting the empennage.

Besides 50 knots groundspeed, the logic does look at other things too, as you suggest. Looks at multiple parameters that indicate you either landed, or did an RTO from above 85 knots.

In order to meet that 1x10e-9 probability, you can be assured the logic and data sources are robust.

I thought there was something about physical limitations of in-flight fold? I can imagine it was some sort of latch, held by lift of the wingtip; or deadbolt which is pushed against the surface by the lift and unable to slide
 
889091
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Joined: Sat Apr 06, 2019 7:56 pm

Re: Rapid Exit Taxiway / 777-8/9 folding wing tips (FWT)

Wed Apr 28, 2021 12:31 pm

Isn't this the same logic of carrier based fighters with foldable wings, just on a smaller scale? E.g the Super Hornet. Extended in flight and folded on the deck/in the hangar.
 
GalaxyFlyer
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Re: Rapid Exit Taxiway / 777-8/9 folding wing tips (FWT)

Wed Apr 28, 2021 12:44 pm

889091 wrote:
Isn't this the same logic of carrier based fighters with foldable wings, just on a smaller scale? E.g the Super Hornet. Extended in flight and folded on the deck/in the hangar.


In theory, yes. In practice, more automated, proven to higher standards of safety and redundancy
 
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Starlionblue
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Re: Rapid Exit Taxiway / 777-8/9 folding wing tips (FWT)

Wed Apr 28, 2021 3:11 pm

GalaxyFlyer wrote:
889091 wrote:
Isn't this the same logic of carrier based fighters with foldable wings, just on a smaller scale? E.g the Super Hornet. Extended in flight and folded on the deck/in the hangar.


In theory, yes. In practice, more automated, proven to higher standards of safety and redundancy


Quite. Military aircraft accept a higher possible failure rate.

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