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YSAPW
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Why can't planes fly faster?

Fri Aug 25, 2017 7:07 pm

Hello community! Even though a member who has been reading the site for a while, this will be my first post.

Recently we have been reading a lot about 'new planes' and much revolves around them, which is natural; for example 778-X, A350, etc. Therefore a lot is discussed regarding the improvements those new airplanes have/will hace, versus the actual models, say in range, mtow, payload, comfort, air cabin pressure, things like 'one will be able to carry 300 people from Sydney to London, etc'.

Nevertheless, i wonder: why are comercial aeroplanes not faster?

As a GA pilot myself, i have the basic understanding in aerodynamics and fuel economics to understand why a plane loaded with people cannot fly say at Mach3 (nowadays). But, say the boeing 747, with proper wind conditions, can physically fly at speeds (airspeeds) relatively close to the speed of sound. My point being: you don't need a super delta wing with 4 turbojet engines to fly at high speeds; again, i don't mean mach 2.

But then again: within all the improvements in range, capacity, comfort, etc, that airplanes are sustaining: how come they actually don't fly faster (i know that 50 knots faster, sustained, for a longhaul, is a lot), but why don't they fly say, 100 - 200 knots faster? Would you actually need a turbojet instead of a highly efficient turbofan? Would the actual airplane design or actual models, have to be so drastically re-designed for just "a little more speed"? NASA and others are developing for sure, the "aircraft of the future"...but im not referring to the medium-long future; im talking about the now.
 
jarheadk5
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Re: Why can't planes fly faster?

Fri Aug 25, 2017 9:00 pm

Speed costs money. Whether it's operational costs like fuel and maintenance, or design & engineering costs that drive the per-airframe cost up, speed costs money.

I would imagine that the airlines have done the math repeatedly, and determined that the current speed range is acceptable for their business models. There are also ATC considerations, especially in places like the NATS. On some airways, you're only going to go as fast as the slowest airplane on the airway, to maintain ATC spacing.

Corporate aviation has demanded higher speeds, and the business jet manufacturers have responded with aircraft that are capable of high Mach 0.8 - low Mach 0.9 cruise speeds. They also cruise at higher altitudes than many airliners, in order to get out of the slower traffic in the lower FLs and take advantage of that speed capability. Corporate aviation (as a general statement) is willing to spend the money for the capability, because it suits their business model.

At current airliner speeds, 100-200kts faster is supersonic. Concorde (and plenty of military flights) proved that sonic booms over land & populated areas are not tolerated well.
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GalaxyFlyer
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Re: Why can't planes fly faster?

Fri Aug 25, 2017 10:37 pm

But, M.90 at F450 isn't a whole lot faster than an airliner at M.82 at F330. Plus at the higher levels you can be above the tailwinds, but out of the headwinds.
 
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Starlionblue
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Re: Why can't planes fly faster?

Sat Aug 26, 2017 1:43 am

I'll just leave this here...

Image
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lightsaber
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Re: Why can't planes fly faster?

Sat Aug 26, 2017 2:47 am

Starlionblue wrote:
I'll just leave this here...

Image

Yep...

It's why business jets, where is is worth optimizing for speed.

A plane capable of flying 10% faster costs about 30% more...

People wouldn't pay for a few minutes of time. The dreamliner would have cost about the 30% more I'm talking about. Do you wonder why airlines asked for the 787?

High speed flight is paid by a few premium passengers. Considering a business jet saves 45+ minutes over a passenger jet just due to TSA and baggage... Over half the premium passengers fly a business jet now, so there went the people paying for speed...

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SCAT15F
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Re: Why can't planes fly faster?

Sat Aug 26, 2017 5:17 am

I'd be curious to see what the sonic cruiser could do today in terms of fuel efficiency with the strides made in engines since 2000.

.98 mach cruise plus faster climb and descent would definitely make up some time on 14+ hour sectors

The G650 and Citation X are really not any faster than the 747. Their long range cruise is still just mach .85. Sure they can top out at Mach .92 or slightly more. Well, the 747 can do that too and with a hell of a lot more passengers and cabin space. They all still use too much gas at that speed to make it useful for anything but short sectors. The Sonic Cruiser on the other hand is/was an entirely different class of airplane
 
GalaxyFlyer
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Re: Why can't planes fly faster?

Sat Aug 26, 2017 11:56 pm

G650 can do it for 13 hours at about M.88. The Global does M.85 for 12. Yes, the C Ten is only good for about 4.5 hours.

Absolutely no corporate operator worries terribly about fuel burns.

GF
 
gloom
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Re: Why can't planes fly faster?

Sun Aug 27, 2017 8:26 am

Yeah, adding to above.

The holy grail is to go above (or behind, rather) that sound barrier, and achieve speed that can be sustained without using afterburner (since afterburner gives +50% thrust, but also +200% fuel consumption). The military have made it possible, generation 5 fighters usually are so called supercruise. F22 goes Ma 1.5-1.6 on supercruise.

It will take some time on commercial airliners to reach that level, though. My estimation would be 2050+, unless a new breakthrough technology becomes available. There are projects since 90s, or maybe even 80s, and none even started.

Cheers,
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XAM2175
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Re: Why can't planes fly faster?

Sun Aug 27, 2017 2:44 pm

Um, the "holy grail" of super-cruise has already been achieved, by Concorde. Afterburning ("re-heat") was only used for take-off and the trans-sonic part of the flight, between Mach 0.95 and 1.70. At all other times it flew on normal thrust alone.
 
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rjsampson
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Re: Why can't planes fly faster?

Mon Aug 28, 2017 3:12 am

Yet, many years ago, there was an airliner (the 727) that routinely cruised at Mach .83. A few folks on here reached .89 on the 72. That is fast, for an early jetliner. A230s and 73x's do not compare to the 72... even though they were the same size.
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cpd
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Re: Why can't planes fly faster?

Mon Aug 28, 2017 4:07 am

XAM2175 wrote:
Um, the "holy grail" of super-cruise has already been achieved, by Concorde. Afterburning ("re-heat") was only used for take-off and the trans-sonic part of the flight, between Mach 0.95 and 1.70. At all other times it flew on normal thrust alone.


And the B-model wouldn't have even had afterburners at all on its engines. It would have been more powerful and more efficient. Would have climbed faster too.

Depending on the flight, take off could also be done without reheat on the A model.
 
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Starlionblue
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Re: Why can't planes fly faster?

Mon Aug 28, 2017 7:02 am

rjsampson wrote:
Yet, many years ago, there was an airliner (the 727) that routinely cruised at Mach .83. A few folks on here reached .89 on the 72. That is fast, for an early jetliner. A230s and 73x's do not compare to the 72... even though they were the same size.


It did cruise fast, but it was nowhere near as efficient as a 737NG or 320 at the same speed. A lovely wing for speed. Modern supercritical wings have allowed a return to those speeds while retaining efficiency.
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Andre3K
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Re: Why can't planes fly faster?

Mon Aug 28, 2017 2:52 pm

gloom wrote:
Yeah, adding to above.

The holy grail is to go above (or behind, rather) that sound barrier, and achieve speed that can be sustained without using afterburner (since afterburner gives +50% thrust, but also +200% fuel consumption). The military have made it possible, generation 5 fighters usually are so called supercruise. F22 goes Ma 1.5-1.6 on supercruise.

It will take some time on commercial airliners to reach that level, though. My estimation would be 2050+, unless a new breakthrough technology becomes available. There are projects since 90s, or maybe even 80s, and none even started.

Cheers,
Adam


Please come back to this post and read the responses. You have a lot to learn.

Short and sweet, Concorde did it a long time ago.
 
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YSAPW
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Re: Why can't planes fly faster?

Mon Aug 28, 2017 8:46 pm

Well. It is an interesting topic indeed, but as stated above, easily explained in a technical way. Nevertheless, 'going faster' is something we humans keep thinking (dreaming) about, i guess.
 
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Re: Why can't planes fly faster?

Thu Aug 31, 2017 9:43 am

SCAT15F wrote:
I'd be curious to see what the sonic cruiser could do today in terms of fuel efficiency with the strides made in engines since 2000.

.98 mach cruise plus faster climb and descent would definitely make up some time on 14+ hour sectors

The G650 and Citation X are really not any faster than the 747. Their long range cruise is still just mach .85. Sure they can top out at Mach .92 or slightly more. Well, the 747 can do that too and with a hell of a lot more passengers and cabin space. They all still use too much gas at that speed to make it useful for anything but short sectors. The Sonic Cruiser on the other hand is/was an entirely different class of airplane

I think it've been mentioned that 777 could be up to an hour faster than 330s on longer routes consider the cruise speed different? That's like 0.05 mach difference?
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wingscrubber
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Re: Why can't planes fly faster?

Fri Sep 01, 2017 8:37 am

If the question is why airliners don't cruise at higher Mach - it's just drag and fuel. Also, with the advent of long range ETOPs, the designers have to optimise the payload-range diagram for a lower MTOW, pushing them to slower speeds to get the same range you might have achieved by carrying a lot more fuel and two extra engines to lift it.

But, if the question is, why don't aircraft fly supersonic (anymore), it's actually more due to technical risk and military dual-use technology conflict than anything else.

Many often bleat on about the economic failure of 'the' Concorde - after all it only operated for 26 years and carried 300,000 passengers and led to the formation of the world's largest airliner manufacturing company, so 'failure' is quite charitable, no?
I frequently notice that the type who point this out often preceding Concorde with 'the' almost always leading into some jealous Aboulafia-like sneer about the fuel economy etc, but there was a more deep rooted resistance to what it represented than that, directly related to the political climate of the era in which it was developed, market protectionism and military technology parallels, but the fuel economy argument is the gripe that everyone remembers, boom paranoia and the Oklahoma City sonic boom tests notwithstanding. The fuel problems and public perception of the 'boom' is not insurmountable though.

Putting aside the political and technological reservations, which are merely psychological barriers and not impossibilities - there's no reason why we shouldn't build airliners which go supersonic, it's been done and it will be done again.

One thing that will drive us to it, is instead of the apparent fuel cost, the actual per-hour operating cost of aircraft could be the benefit; the power-by-the-hour lease model which underpins business jets considers other overheads such as the crew time and passenger through-put on any given route, fuel is just one of multiple factors that affect profitability. Ultimately airlines are just human logistics companies and if one can deliver the package more quickly and charge a premium for it while incurring less operating time, well that's a competitive edge.

But it's only a competition if there's more than one, Tu-144 was never a true contender and the US failed to field its own SSTs, allowing Concorde to be a white elephant on a plinth, in an ivory tower on top of a mountain - opening it up wide for criticism of its bourgeois opulence, because nothing else has ever come close to it.

Another driver for change will be the continued emergence of the BRIC nations into civil airliner manufacturing - eventually Airbus and Boeing will be knocked off their perch by cheaper Chinese, Brazilian and Russian equivalents in the next 4 decades, once they reach parity the western supersonic aspirations will return because it won't be possible to compete with BRIC manufacturers on price, you would have to compete with them on luxury.

'Boom' is the one to watch I feel, they seem to have grasped the fundamentals and have a big financial backer. Aerion on the other hand, especially judging by their initial engine selections and targeted cruise speeds, are kind of stumbling as far as I can see.
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YSAPW
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Re: Why can't planes fly faster?

Fri Sep 01, 2017 5:16 pm

wingscrubber wrote:
If the question is why airliners don't cruise at higher Mach - it's just drag and fuel. Also, with the advent of long range ETOPs, the designers have to optimise the payload-range diagram for a lower MTOW, pushing them to slower speeds to get the same range you might have achieved by carrying a lot more fuel and two extra engines to lift it.

But, if the question is, why don't aircraft fly supersonic (anymore), it's actually more due to technical risk and military dual-use technology conflict than anything else.

Many often bleat on about the economic failure of 'the' Concorde - after all it only operated for 26 years and carried 300,000 passengers and led to the formation of the world's largest airliner manufacturing company, so 'failure' is quite charitable, no?
I frequently notice that the type who point this out often preceding Concorde with 'the' almost always leading into some jealous Aboulafia-like sneer about the fuel economy etc, but there was a more deep rooted resistance to what it represented than that, directly related to the political climate of the era in which it was developed, market protectionism and military technology parallels, but the fuel economy argument is the gripe that everyone remembers, boom paranoia and the Oklahoma City sonic boom tests notwithstanding. The fuel problems and public perception of the 'boom' is not insurmountable though.

Putting aside the political and technological reservations, which are merely psychological barriers and not impossibilities - there's no reason why we shouldn't build airliners which go supersonic, it's been done and it will be done again.

One thing that will drive us to it, is instead of the apparent fuel cost, the actual per-hour operating cost of aircraft could be the benefit; the power-by-the-hour lease model which underpins business jets considers other overheads such as the crew time and passenger through-put on any given route, fuel is just one of multiple factors that affect profitability. Ultimately airlines are just human logistics companies and if one can deliver the package more quickly and charge a premium for it while incurring less operating time, well that's a competitive edge.

But it's only a competition if there's more than one, Tu-144 was never a true contender and the US failed to field its own SSTs, allowing Concorde to be a white elephant on a plinth, in an ivory tower on top of a mountain - opening it up wide for criticism of its bourgeois opulence, because nothing else has ever come close to it.

Another driver for change will be the continued emergence of the BRIC nations into civil airliner manufacturing - eventually Airbus and Boeing will be knocked off their perch by cheaper Chinese, Brazilian and Russian equivalents in the next 4 decades, once they reach parity the western supersonic aspirations will return because it won't be possible to compete with BRIC manufacturers on price, you would have to compete with them on luxury.

'Boom' is the one to watch I feel, they seem to have grasped the fundamentals and have a big financial backer. Aerion on the other hand, especially judging by their initial engine selections and targeted cruise speeds, are kind of stumbling as far as I can see.



Interesting point of view.

A bit related: i was watching a video where it was mentioned that Concorde had a lot of orders/options coming from carriers like Lufthansa, Eastern, JAL, TWA, PanAm...(those numbers you can even check), but that one of the deciding moments that got most of those orders cancelled, was the crash of the TU-144 at the Paris Airshow in 1973 (which sounds too "cherry on top" kind of reason, but not the reason). I guess it would have been a whole different story, if all those additional Concordes would have been built...
 
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ro1960
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Re: Why can't planes fly faster?

Sun Sep 03, 2017 9:52 pm

It's cost that drives aviation, not speed like said by others. This video summarizes it pretty simply:

https://www.youtube.com/watch?v=n1QEj09Pe6k

The masses want $100 TATL flights, not 3-hour TATL flights with a $10000 price tag.
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exFWAOONW
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Re: Why can't planes fly faster?

Wed Sep 06, 2017 1:53 pm

Remember the Sonic Cruiser? It was a Boeing concept that would fly at higher mach, shortening ocean crossings. No-one bit on it, so the manufacturers went back to offer slower and more fuel-efficient planes.
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VSMUT
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Re: Why can't planes fly faster?

Thu Sep 07, 2017 10:53 am

Starlionblue wrote:
I'll just leave this here...


Don't forget this one:

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