why do the fly more slowlly?
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I have sat waiting many times for a rental car at Heathrow watching them land. Its always appeared to me that the A320 is moving much faster on final than the 737. The A320 also hits the same spot in the runway everytime while the 737 will touchdown in a wide range of area.
Funny though, the 737 doesn't call the pilot a retard after he flies halfway down the runway.
Funny though, the 737 doesn't call the pilot a retard after he flies halfway down the runway.
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Flew for one company where the instruction from the top was...'fly fast, fuel is cheap.'
So we did, M.865 (highest speed you could program in the FMS), and sailed past Airboos equipment like they were dragging a boat anchor.
So we did, M.865 (highest speed you could program in the FMS), and sailed past Airboos equipment like they were dragging a boat anchor.
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RadarContact,
By saying the A320 hits the same spot, I meant from my observations it hits just past the paint stripes while the 737 hits there and up to halfway down the runway. Sorry for the confusion.
By saying the A320 hits the same spot, I meant from my observations it hits just past the paint stripes while the 737 hits there and up to halfway down the runway. Sorry for the confusion.
the lunatic fringe
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The A320 flys quicker than the Boeing 737.
In the cruise the A320 flys at around Mach .74 to M.76. The 737 at about M.72 to M.74.
The A340 flys slower than the Boeing 747.
The 747 bashes along at M.84 to M.86 and even faster if needed. The A340, from observation, as it is the only one in the list I have not flown, at around M.82.
As to why, Thats what they were designed to do... As to why they were designed to do those speeds. No idea.
L337
In the cruise the A320 flys at around Mach .74 to M.76. The 737 at about M.72 to M.74.
The A340 flys slower than the Boeing 747.
The 747 bashes along at M.84 to M.86 and even faster if needed. The A340, from observation, as it is the only one in the list I have not flown, at around M.82.
As to why, Thats what they were designed to do... As to why they were designed to do those speeds. No idea.
L337
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Why design speeds are different?
Not a simple question to answer - I'll do my best to keep it understandable.
As ever, it all comes down to the bottom-line - MONEY
Think of the process as being like Cost Index - but you can change the plane design, rather than just the flight speed
The faster you want a plane to fly, the more wing sweep you need which starts to hit L/D, increase structural weight, needs bigger engines although engine SFC is reduced (can also impact noise).
All of these increase fuel burn per seat. Increased weight also puts up other costs like landing and navigation fees among others
On the other hand, reduced flight time can reduce time based costs like flight & cabin crew as well as maintenance costs. Further, more speed can increase aircraft utilisation permitting finance charges to be amortised over more flights per year.
I also believe there used to be an advantage in the old travel agents booking system that gave priority to the shortest flight times (faster aircraft) - unsure if this was/is true.
Clearly, there is a balance to be struck, and this is often influenced by the conditions at the time (fuel price, labour prices).
A couple of extreme examples
Concorde was an all out speedbird with little regard for fuel costs. If you like, this was largely an Airbus aircraft (similar partners apart from the Germans) and that was twice as fast as any Boeing aircraft. However, speed was not everything and the economics of the 747 eventually ran out the winner in terms of aircraft sales.
Boeing's Sonic Cruiser also pushed the cost of time vs cost of fuel issue but failed to converge to an acceptable solution.
Hope this helps
Not a simple question to answer - I'll do my best to keep it understandable.
As ever, it all comes down to the bottom-line - MONEY
Think of the process as being like Cost Index - but you can change the plane design, rather than just the flight speed
The faster you want a plane to fly, the more wing sweep you need which starts to hit L/D, increase structural weight, needs bigger engines although engine SFC is reduced (can also impact noise).
All of these increase fuel burn per seat. Increased weight also puts up other costs like landing and navigation fees among others
On the other hand, reduced flight time can reduce time based costs like flight & cabin crew as well as maintenance costs. Further, more speed can increase aircraft utilisation permitting finance charges to be amortised over more flights per year.
I also believe there used to be an advantage in the old travel agents booking system that gave priority to the shortest flight times (faster aircraft) - unsure if this was/is true.
Clearly, there is a balance to be struck, and this is often influenced by the conditions at the time (fuel price, labour prices).
A couple of extreme examples
Concorde was an all out speedbird with little regard for fuel costs. If you like, this was largely an Airbus aircraft (similar partners apart from the Germans) and that was twice as fast as any Boeing aircraft. However, speed was not everything and the economics of the 747 eventually ran out the winner in terms of aircraft sales.
Boeing's Sonic Cruiser also pushed the cost of time vs cost of fuel issue but failed to converge to an acceptable solution.
Hope this helps
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Ferrydude
Are all your postings as informative as this?
The guy at the top asked a question and I answered it.
I for one would be very interested in whatever thoughts you are capable of on the issue.
All manufacturers select their cruise speed based on the criteria I discussed + maybe some more market driven reasons.
Of course, this does not mean that they will all reach the same conclusion. Whose right? The market at any given time decides.
Are all your postings as informative as this?
The guy at the top asked a question and I answered it.
I for one would be very interested in whatever thoughts you are capable of on the issue.
All manufacturers select their cruise speed based on the criteria I discussed + maybe some more market driven reasons.
Of course, this does not mean that they will all reach the same conclusion. Whose right? The market at any given time decides.
Paxing All Over The World
From asking many dumb questions over the years ... I have been told that Airbus designed for two things:
1) Clean wings that are highly efficient to make the cruise lighter on fuel.
2) Donkeys that will do the job but not be too thirsty.
If you are a manufacturer that is moving into a crowded market (Boeing, Lockheed Mc Donnell-Douglas) then you have to have something that will attract the attention of the punters. Whilst in Europe they may have had a more favourable audience(!) the only factor they could go with was price.
Lately, with Airbus now mature in themselves and consolidation amongst the others, we see Embraer and Canadair doing exactly the same thing. Jet Blue has just ditched Airbus for Embraer.
When you can go faster for less fuel - then it will be done but if less fuel means cheaper-but-a-teeny-bit slower, then that is what you will see.
On short hauls, not much to notice. On long haul, for example, VS allow an extra 30 mins on the schedule for their A340s on JNB-LHR than their 744s. It's just less than that but the rounding up of time is neater for the timetable!
I sit to be corrected.
1) Clean wings that are highly efficient to make the cruise lighter on fuel.
2) Donkeys that will do the job but not be too thirsty.
If you are a manufacturer that is moving into a crowded market (Boeing, Lockheed Mc Donnell-Douglas) then you have to have something that will attract the attention of the punters. Whilst in Europe they may have had a more favourable audience(!) the only factor they could go with was price.
Lately, with Airbus now mature in themselves and consolidation amongst the others, we see Embraer and Canadair doing exactly the same thing. Jet Blue has just ditched Airbus for Embraer.
When you can go faster for less fuel - then it will be done but if less fuel means cheaper-but-a-teeny-bit slower, then that is what you will see.
On short hauls, not much to notice. On long haul, for example, VS allow an extra 30 mins on the schedule for their A340s on JNB-LHR than their 744s. It's just less than that but the rounding up of time is neater for the timetable!
I sit to be corrected.
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" why do the airbuses usually have lower speed limit than boeings?"
See my previous answers!
This question is only true at the long-range end of the product line. At short & medium, it depends which aircraft you compare - A320 vs 737 or 757vs A321 or A332 vs 767 or 767 vs A300/A310.
I am certain that both Airbus & Boeing could design aircraft at whatever speed they so chose - they have just arrived at different conclusions concerning the value of speed.
As I said previously, it is in the balance that the airframers make.
Airbus could have selected a higher wing sweeo for the A330/A340 sweep to achieve a cruise Mach similar the 777 (777 has 1.6 degrees more sweep than the A330/A340).
In balance mentioned earlier, Boeing pushed the speed a bit and Airbus opted for fuel economy.
That said, the A330/A340 are not slow and the 777 is not a fuel guzzler, just that the fine balance between the two issues is different.
The high speed of a 747 may come from the fact that the basic aerodynamics were designed in the 1960's - i.e. fuel was cheap. Although they have been subsequently improved, the basic speed is a function of the wing sweep and aerodynamic sections.
So Ferrydud, your opinions are deafening me!
This question is only true at the long-range end of the product line. At short & medium, it depends which aircraft you compare - A320 vs 737 or 757vs A321 or A332 vs 767 or 767 vs A300/A310.
I am certain that both Airbus & Boeing could design aircraft at whatever speed they so chose - they have just arrived at different conclusions concerning the value of speed.
As I said previously, it is in the balance that the airframers make.
Airbus could have selected a higher wing sweeo for the A330/A340 sweep to achieve a cruise Mach similar the 777 (777 has 1.6 degrees more sweep than the A330/A340).
In balance mentioned earlier, Boeing pushed the speed a bit and Airbus opted for fuel economy.
That said, the A330/A340 are not slow and the 777 is not a fuel guzzler, just that the fine balance between the two issues is different.
The high speed of a 747 may come from the fact that the basic aerodynamics were designed in the 1960's - i.e. fuel was cheap. Although they have been subsequently improved, the basic speed is a function of the wing sweep and aerodynamic sections.
So Ferrydud, your opinions are deafening me!
Last edited by Noise Unit; 8th Aug 2003 at 00:18.
L337,
to my recollection the 737 - 200 flies at about .72-.73, the 737-3/4/500 flies at .74-.75, and the -737-6/7/800 flies at .78-.79 - ish.
It depends on your fixed costs against fuel prices, if the cost index is high as it was in the late 90s, the -800 will cruise happily at .795. In my current Company, the -700 cruises at .78 with a much lower cost index because of higher fuel prices, but it does it at FL 400 and FL 410.
to my recollection the 737 - 200 flies at about .72-.73, the 737-3/4/500 flies at .74-.75, and the -737-6/7/800 flies at .78-.79 - ish.
It depends on your fixed costs against fuel prices, if the cost index is high as it was in the late 90s, the -800 will cruise happily at .795. In my current Company, the -700 cruises at .78 with a much lower cost index because of higher fuel prices, but it does it at FL 400 and FL 410.