sleekjet
Posts: 2006
Joined: Sat Jul 28, 2001 1:35 am

Max Cruising Speeds - Have They Plateaued?

Sun May 30, 2004 2:16 am

Is there some overriding reason why all of our passenger jets have top cruising speed in the 500's? It seems that since it has been this way since the advent of jet engines, there must be a really good reason why they are locked in there.
II Cor. 4:17-18
 
NWB757300
Posts: 135
Joined: Sun Apr 25, 2004 6:47 am

RE: Max Cruising Speeds - Have They Plateaued?

Sun May 30, 2004 2:32 am

It has to do with the structural limits of the aircraft. Most cannot handle more than that due to the forms and design of the aircraft.

All max cruising speeds are based on the ability of the airframe to withstand the forces of that speed.

[Edited 2004-05-29 19:33:40]
Remember when sex was safe and flying was dangerous?
 
citationjet
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RE: Max Cruising Speeds - Have They Plateaued?

Sun May 30, 2004 2:50 am

I don't think it is a structural issue as much as it the increased in drag as you approach Mach 1. To overcome the drag, it takes much larger engines. Look at the size of the engines on the Citation X, which flies Mach 0.92
Boeing Flown: 701,702,703;717;720;721,722;731,732,733,734,735,737,738,739;741,742,743,744,747SP;752,753;762,763;772,773.
 
pelican
Posts: 2429
Joined: Mon Apr 05, 2004 9:51 pm

RE: Max Cruising Speeds - Have They Plateaued?

Sun May 30, 2004 4:09 am

Jets are approaching the sound barrier. The sound barrier is called barrier because a plane needs much force, hence much energy to overcome it. Passenger jets fly as close to the sound barrier as economics allow.

pelican
 
MITaero
Posts: 485
Joined: Mon Jul 28, 2003 8:00 am

RE: Max Cruising Speeds - Have They Plateaued?

Sun May 30, 2004 5:18 am

As stated above, it's not a structural issue or an engine issue. Drag rise is unbearable very close to Mach 1, so too much fuel is needed to go supersonic. As usual, it comes down to economics.
 
Okie
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Joined: Wed Jul 16, 2003 11:30 am

RE: Max Cruising Speeds - Have They Plateaued?

Sun May 30, 2004 5:26 am

Largely an economic plateau.

The non bypass or low bypass turbine engines of the 707, 727, 737-100,200 DC-8,9 880,990's tridents etc etc would cruise about .1mach higher than today's aircraft, but were fuel hogs compared to today's high bypass engine and airframe designs.
So today's high bypass designs traded off about 60 knot's for about 30-40% gain in fuel efficiency. Along with that came different wing designs to operate at the slower speeds with less drag and more lift and more efficiency as well.

Its about $$$

When a propulsion system is developed that can economically propel and aircraft at economical cost and an airframe designed that can do away with the tremendous drag at high mach number then there will be another attempt at higher mach numbers for commercial aircraft.

Okie
 
oly720man
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Joined: Fri May 21, 2004 7:13 am

RE: Max Cruising Speeds - Have They Plateaued?

Sun May 30, 2004 6:07 am

With most commercial aircraft following air corridors they all have to go at much the same speed to maintain separation.

Andy
wheat and dairy can screw up your brain
 
airplay
Posts: 3369
Joined: Sat Oct 25, 2003 1:58 am

RE: Max Cruising Speeds - Have They Plateaued?

Sun May 30, 2004 6:12 am

Its all about the Benjamin's baby....I mean the "Bordens"!
 
QantasA332
Posts: 1473
Joined: Sat Dec 13, 2003 5:47 pm

RE: Max Cruising Speeds - Have They Plateaued?

Sun May 30, 2004 7:32 am

It's the same reason all plans for new high-subsonic/sonic/supersonic have been dropped for now, and the reason everyone has mentioned above - economics. More specifically, it's primarily the very high (wave) drag present as an aircraft approaches M 1.0 that drives the economic considerations. Obviously, high-enough power engines and huge amounts of fuel are necessary to overcome that drag. With aviation the way it is at the moment, most operators aren't clamouring for fuel-thirstier aircraft (to say the least!). Accordingly, cruising speeds haven't plateaued due to the impossibility of going any faster (i.e. it is certainly possible to go faster!), but rather due to the impractibility given the current state of aviation, as I said. As our planet is slowly drained of oil, things could very well worsen if alternatives aren't looked into...

Cheers,
QantasA332

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