From “Any leaks, ideas, or otherwise: What is Airbus’ new clean-sheet aircraft?, post #155 :
viewtopic.php?f=3&t=1429207&p=21613937#p21613937

TObound wrote:

keesje wrote:

TObound wrote:

An A330 sized MOM wouldn't fit into a narrowbody gate. That will be an issue.

Span around 44 m, Code D gates, like 757 and 767.

Yes. But it needs to fit a Code C gate to really sell. How many airlines around the the world do you think would be happy paying higher fees to use a Code D gate for short haul? And how do you think airports would deal with a sudden shift in traffic from Code C to Code D gates (in many places often reserved for international service)?

While I’m afraid that TObound is right, it reminds me of the nose and the glasses:

“It is demonstrable," said he, "that things cannot be otherwise than as they are; for as all things have been created for some end, they must necessarily be created for the best end. Observe, for instance, the nose is formed for spectacles, therefore we wear spectacles. The legs are visibly designed for stockings, accordingly we wear stockings. Stones were made to be hewn and to construct castles, therefore My Lord has a magnificent castle; for the greatest baron in the province ought to be the best lodged. Swine were intended to be eaten, therefore we eat pork all the year round: and they, who assert that everything is right, do not express themselves correctly; they should say that everything is best.”
Voltaire, “Candide”

Embraer’s E190-E2 has a MTOW of 56,4 t. It’s Al-Li wing spans 33,7m
Embraer’s E195-E2 has a MTOW of 61,5 t. It’s Al-Li wing spans 35,1m.

Thoughts?

yep, please define topic in direct statements

if you ask to drop class C gates - it is possible, but planes for class C still will have advantages.

and still many ways to improve airliners , include for fit them in class C.
MS-21 wing close to CS300 in span and area. wingtips can help in some ways.
still ways to change airfil and area inflight.

for more radical solutions, avanti-style triplane can have less span.

Voltaire is known for irony and sarcasm.
"Observe that the nose is formed for spectacles." That is of course rubbish. The spectacles are formed according to the nose, not the other way round.
Should planes be designed according to gates or gates according to planes?
When were gate sizes defined? What was the engine power at that time, how much is engine power now? I have more questions in mind, but let's see what ideas other people have.

You're debating philosophy when this is a question of finance. Replacing existing infrastructure is expensive. Airlines won't pay for it. Simple as that.

In newer airports, there maybe more D gates which airlines can use. Tough sell for airlines that operate from older airports.

TObound wrote:

You're debating philosophy when this is a question of finance. Replacing existing infrastructure is expensive. Airlines won't pay for it. Simple as that.

In newer airports, there maybe more D gates which airlines can use. Tough sell for airlines that operate from older airports.

To remain philosophical:
What was first, the egg or the chicken?

That apart, as I said in the OP, I'm afraid you are right.

Sokes wrote:

TObound wrote:

You're debating philosophy when this is a question of finance. Replacing existing infrastructure is expensive. Airlines won't pay for it. Simple as that.

In newer airports, there maybe more D gates which airlines can use. Tough sell for airlines that operate from older airports.

To remain philosophical:
What was first, the egg or the chicken?

More a history question than anything. Jetbridges weren't a thing until the late 1950s. Around the time that ICAO was really starting to get rolling on standardization. I think once airports started installing jetbridges, ICAO probably started codifying aircraft gate sizes along those lines. This is how I would guess the process happened.

At this point though, history is all but irrelevant. The existing gates and terminals are a massive sunk cost. Re-arranging them would not be trivial. We are not talking making a gate or two compatible for A380 service. We are talking about the bulk of gates at most airports.

TObound wrote:

Sokes wrote:

TObound wrote:

You're debating philosophy when this is a question of finance. Replacing existing infrastructure is expensive. Airlines won't pay for it. Simple as that.

In newer airports, there maybe more D gates which airlines can use. Tough sell for airlines that operate from older airports.

To remain philosophical:
What was first, the egg or the chicken?

More a history question than anything. Jetbridges weren't a thing until the late 1950s. Around the time that ICAO was really starting to get rolling on standardization. I think once airports started installing jetbridges, ICAO probably started codifying aircraft gate sizes along those lines. This is how I would guess the process happened.

At this point though, history is all but irrelevant. The existing gates and terminals are a massive sunk cost. Re-arranging them would not be trivial. We are not talking making a gate or two compatible for A380 service. We are talking about the bulk of gates at most airports.

Which basically means, unless the D sized replacement is a LOT better economically than what can be built as a code C (folding wings etc) it simply isn't happening. I'm not sure any combination of tube-wing-2turbofans will make that difference, it will really need to be a step change, and even then the question of, 'can't you make a 34.99m version of that?' will rightly be asked.

How strictly are these guidelines followed? The 757 is often parked at gates that can’t fit an a310 or 767.

My question is, isn’t the gate sized up to a specific planes wing span rather than a code?

Kno wrote:

How strictly are these guidelines followed? The 757 is often parked at gates that can’t fit an a310 or 767.

My question is, isn’t the gate sized up to a specific planes wing span rather than a code?

I think I read once that an airline short of place who had an own terminal redesigned the gates to fit their fleet and not some norm.

flipdewaf wrote:

In the spirit of a somewhat philosophical thread, any rule written by man can surely be unwritten by man.

Fred

Cool! Now we have a discussion. I was laughing when I read your post.

It's actually not really a philosophical topic. I find it ridiculous that planes are designed according to gates and not the other way round.
I started with Voltaire because I thought the nose and the glasses make for a nice joke.

What was first, the chicken or the egg?
It means: 35m gate > 35 m plane > 35 m gate > 35 m plane > 35 m gate > 35 m plane ....
A lot of airports were built the last years. Anybody knows which is the popular gate size in Istanbul or new Chinese airports? Is it 36m?
So when is the right time to reconsider gate sizes: 20 years ago, 10 years ago, now, in 10 years, in 30 years, in 100 years?

I add two more planes to the discussion:

ATR 72-600: .......................... wingspan: 27,1 m, OEW 13,5 t, MTOW: 23,0 t, passengers: 70 @ 30', speed: 510 km/ h
De Havilland Canada Dash 8: wingspan: 28,4 m, OEW 17,8 t, MTOW 30,5 t, passengers: 82 @ 30', speed: 556-667 km/ h

So if we think outside the 35 m (and 52 m) box, we may as well think about speed.

I believe a long as there are only 36 m and 52 m gates, there will be no new 6-abreast narrow-bodies from Airbus or Boeing any time soon.

Sokes wrote:

To remain philosophical:
What was first, the egg or the chicken?

Dinos

I would have thought that at a time when the average airline fleets are getting bigger due to market growth and concentration, and considering that the overall air travel market is getting bigger, there would have been an incentive for a having a greater number of aircraft models, each model having a specialized role. It seems that the incentive for fairly specialized sub-fleets is smaller than the possible economies of scale coming from operating identical aircraft across the board and more importantly, than the incentive for the OEMs to maximize the output of existing models while avoiding investments in new models. As a result, the gate size hasn't really been so far a serious constrain for the NB, since there hasn't been any clean sheet design that would have been constrained by this limit. Nevertheless, it appears that the gate constrains will be dealt with by means of folding wingtips on the expected clean sheet designs.

This being said, with the progress of automation, sensors and AI, I'm wondering if the way forward couldn't be reduced gates and taxi clearances rather than adding the weight and the complexity of folding wingtips. Any stupid car will soon look much smarter than the most advanced airliners when it comes to taxiing and parking.

tomcat wrote:

...
It seems that the incentive for fairly specialized sub-fleets is smaller than the possible economies of scale coming from operating identical aircraft across the board and more importantly, than the incentive for the OEMs to maximize the output of existing models while avoiding investments in new models. As a result, the gate size hasn't really been so far a serious constrain for the NB, since there hasn't been any clean sheet design that would have been constrained by this limit. Nevertheless, it appears that the gate constrains will be dealt with by means of folding wingtips on the expected clean sheet designs.

This being said, with the progress of automation, sensors and AI, I'm wondering if the way forward couldn't be reduced gates and taxi clearances rather than adding the weight and the complexity of folding wingtips. Any stupid car will soon look much smarter than the most advanced airliners when it comes to taxiing and parking.

I also tend to believe that folding wingtips is not the way forward. Wind turbine manufacturer Enercon tried blades which were divided in two for better transport.
E.g. E141: 16,2 m inner blade section, 50,5 m outer blade section. The turbines with divided blades were discontinued after a short time. However to install a huge wind turbine at a remote place may have more logistic problems beside the blades. Maybe other components were too expensive?
However later designs of theirs were full blade again. I'm not aware any other wind turbine manufacturer tried divided blades. So I believe divided blades are rather not cost effective.

"the incentives for OEMs..."
The supply chain can't keep up anyway. However it will not be forever a seller's market. I hope once offer and demand balances the OEMs will ask what are the appropriate designs for the available technology.
Why they didn't do it 20 years ago? I assume
a) it was more important to focus on wide-bodies / twins with good range at reasonable capacity
b) airport infrastructure was unsuitable for a 45 m wing narrow-body. Which brings us back to the chicken and egg problem.

Why are turboprops so economical? Because they push a lot of air with medium speed as opposed to less air at high speed.
There seems to be a majority opinion on a.net that the B737 MAX is limited by the space under the wings. While it is true for high MTOW versions, is it true for the vast majority of narrow-bodies? Let's assume Boeing's software will be fine once they provide redundancy.

CFM 56-5B series (A 320 family): Bypass ratio 5,5-6,0 / Overall pressure ratio 32,6 - 35,4 : 1
CFM 56-7 series (B737NG family): Bypass ratio 5,1-5,5 / Overall pressure ratio 32,7 : 1
IAE V2500 (A321) : Bypass ratio 4,5:1 / Overall pressure ratio 35:1

Leap 1A (for A320 Neo family): Bypass ratio 11:1 / Overall pressure ratio: 40:1
Leap 1B (for B737 Max family): Bypass ratio 9:1 / " : 40:1

PW1100G (for A320 family): Bypass ratio: 12,5:1 / Overall pressure ratio: ?

Why can the A320 Neo not profit (or profit more) from it’s bigger engine diameter at common MTOWs?

From "A350 Neo - ULR Redundant" :
viewtopic.php?f=5&t=1430475

Revelation wrote:

Second, I would not pencil in BLADE improvements for A350neo.

As https://en.wikipedia.org/wiki/Breakthro ... _in_Europe says:

Its wing sweep is around 20° for a Mach 0.75 cruise instead of 30° for Mach 0.82-0.84, laminar flow is expected along 50% of chord length instead of just aft of the leading edge, halving the wing friction drag, reducing the overall aircraft drag by 8% and saving up to 5% in fuel on an 800nm (1,480km) sector.[1]
...
The aerodynamic benefits could be sustained at Mach 0.78 up from M0.75 and next-generation single-aisles could use from the late 2020s.

The A350's wing has a 31.9° sweep angle for a Mach 0.85 cruise speed ( ref: https://en.wikipedia.org/wiki/Airbus_A350_XWB ).

The BLADE results are very good, but really only meaningful for a single aisle where cruise speed is not commercially significant.

Also BLADE only works when one holds extremely high manufacturing tolerances, which adds a lot of cost to build and maintain so you'd only use it when it paid for itself.

A350neo would need an all-new wing with redesign of the wingbox for different sweep angle and accept a slower cruise speed to benefit from BLADE.

Anybody knows more about speeds and laminar flow?

Sokes wrote:

I also tend to believe that folding wingtips is not the way forward. Wind turbine manufacturer Enercon tried blades which were divided in two for better transport.
E.g. E141: 16,2 m inner blade section, 50,5 m outer blade section. The turbines with divided blades were discontinued after a short time. However to install a huge wind turbine at a remote place may have more logistic problems beside the blades. Maybe other components were too expensive?
However later designs of theirs were full blade again. I'm not aware any other wind turbine manufacturer tried divided blades. So I believe divided blades are rather not cost effective.

Returning to single piece blades was enabled by self propelled low boy designs that can now operate in environmental conditions that would disallow a tractor pulled one ( improved traction ).

And I'd guess that improved (G->C)FRP production techniques made continuous blades more attractive.
Having to accomodate a flange in the heavy (inner) part of the blade is a PITA.

What is most interesting to me is that the economical costs of reconfiguring the world's airports far outweighs the costs (both economical and safety) of folding wingtips. Imagine, being told early on that you should introduce an extra mechanism, an extra component that can fail, something that adds more weight than would a conventional design, all because of a seemingly trivial gate requirement.

All of those requirements, plus the added hurdle of certifying the design, and yet its still more cost effective than reconfiguring gates. Of course the safety issue is minimal, the 777x folding wing tips are akin to wingtips, merely increasing aspect ratio and not critical to normal operation - still plenty of lift generated.

It's really a neat case study for students to study in how requirements come about and influence the design of aircraft. Imagine, if you will, 2 thousand years from now they are studying the design of the 777x and have no background knowledge of the folding wing tips and why they were there. It would surely be puzzling to those scholars.

I believe going forward that airports will have to begin considering that we are moving towards higher efficiency (higher aspect ratio) wings and that gates should be sized appropriately during remodel. Anyone involved in the upgrades underway at DFW (just to pick an airport where I know a new terminal is in the works)? Any idea on gate allocations? Was pretty sure there was a powerpoint floating around about this very topic.

In the first half of 2019 Airbus had a revenue of 31 billion Euro, 4 billion of which was attack/ defence. Subtract helicopters and I guess Airbus turnover from commercial planes is around 50 billion Euro/ year. I'm not so sure that to re-configure gates is more expensive than to fly around with sub-optimal plane designs for eternity. If it is, aviation fuel is too cheap.

De Havilland Canada Dash 8: wingspan: 28,4 m, OEW 17,8 t, MTOW 30,5 t, passengers: 82 @ 30', speed: 556-667 km/ h
With the square rule a quarter longer wing than a Dash 8 would allow for 56% more MTOW.
So with Dash 8 speeds 35 m wingspan is good enough for a MTOW of around 48t.

I assume for economical and ecological and comfort reasons something like 750 km/ h instead of today’s narrow-bodies’ 830 km/ h (Mach 0.78) might be appropriate for short to medium ranges. I’m just assuming things here. In absence of better knowledge I take the new Embraer to estimate suitable wing lengths.
Embraer’s E190-E2 has a MTOW of 56,4 t. It’s Al-Li wing spans 33,7m
Embraer’s E195-E2 has a MTOW of 61,5 t. It’s Al-Li wing spans 35,1m.
I conclude for a carbon wing 35 m wingspan is good for 60 t MTOW at Mach 0.78 (450 kn; 833 km/h).

A220-100: OEW = 35,2t, MTOW = 63t
A220-300: OEW = 37,1t, MTOW = 69,9t
A320: OEW = 42,6t, MTOW = 78t
A321: OEW = 48,5t, MTOW = 93,5t
A321 Neo: OEW = 50,1t, MTOW = 97t
A321 NEO XLR: OEW = ?, MTOW = 101t

100t / 60t = 1,67
1,3 x 1,3 = 1,69
35m x 1,3 = 45,5 m
If 35m wingspan is good for 60t, 45 m wingspan is good for 100t.

I conclude the following gate sizes are necessary:
30m:
-for 2+2 seating turboprops, regional jets (CRJs)

35m:
-for 2+2 (Embraer) or 2+3 seating (A220)

40m:
-for short to medium range A319 Neo/ A320 Neo/ B737-7/ B737-8: MTOW 75t with a wing designed for 750 km/h. Obviously the range of the smaller planes may actually be quite good.
-for medium to long range A320 Neo/ B737-8: MTOW 85t with a wing designed for 830 km/h.

45m:
-For A321 Neo
Two subtypes: MTOW 90t, cruise speed 750 km/ h and MTOW 105t, cruise speed 830 km/ h


Flexible gate use:
3x35m = 105m = 2x52m. I believe that’s the wrong approach. I suggest:
120m=
=3x40m=
=45m + 30m + 45m=
=35m + 40m + 45m=
=35m + 55m + 30m

I may as well add flexible gate use for wide-bodies and 45m span narrow-bodies:
185m =
=65m + 55m + 65m=
=55m + 75m + 55m=
=65m + 45m + 75m=
=60m + 65m + 60m (for 2 x B787 and 1 x A350)

Obviously one has to add for space between planes or planes and buildings.
Keep in mind I’m not an expert. I don’t know how much heavier a 40m or 45m wing is. My estimates may therefore be incorrect. Same applies to speed. I was just guessing 750 km/ h and 830 km/ h. It may well be that 730 and 800 km/ h are better. I also assumed an A321 wingbox can support a 45m wing.

Airport real estate is incredibly precious/expensive.

Are we debating the need for folding wingtips? A billion dollar terminal will serve multi billion in aircraft, so I see more floors in terminals to maximize the passenger count per year for given amount of land. As more efficient aircraft need longer wings for underside laminar flow, so the only way I know to make that happen is remove a constraint via folding wingtips.

Lightsaber