SchorschSorry, but this is a very poor argument. I see this being used by SO many Airbus fanboy’s to justify some sort of argument against Boeing.
Although not used for that purpose here, the statement is completely incorrect nonetheless.Simple fact is, American Legacy carriers were affected badly by the post 911 industry shakeup. We ALL know about their financial woes. Even you Schorsch, as I’ve seen you make light of it elsewhere.
They have now got their act together and most are on the road to recovery.Watch for a huge influx of orders, both for A and B as the legacies get into a position to start fleet replacements.
Can you please elaborate on how I could use this argument in further A vs B discussions, because even after hard thinking I couldn’t claim a point for Airbus on this matter.
NWA has one of the oldest fleet in USA, has a considerable Airbus fleet and its fleet age average is dominated by its DC-9. So what?
The decision to use older aircraft instead of newer ones is nothing directly related to 2001 downturn.
SchorschShip741 is right in some issues. It makes only sense to develop new aircraft if efficiency gain is 20% or more or the aircraft opens different markets (like A380). We see that in today’s reluctance to develop a B737/A320 replacement.
Taking a look at North American operators, we also see reluctance to replace aircraft.
A problem encountered with civil aircraft is that after 20 years they are often out of hours, the airframe is due for scrap.
Financially well equipped airlines use new aircraft as mean for depreciation. If they earn money, the aircraft is virtually for free except for financing costs, but they can fully put the expenses on their bill and reduce taxes.
Anyways, airlines often need new aircraft, and then they take what is available from the manufacturers (buying used aircraft has many drawbacks, you can hardly build up a fleet of similar aircraft by that). In this case, the option if you need twin engine long-range medium capacity is:
– A330
– B787
– B767
Boeing doesn’t offer the B767 any more as PAX aircraft. Manufacturers want to seel new aircraft.
This system of buying new instead of using old stuff (which is still quite OK) is somehow part of our Western industrial thinking: buying something new is cool. This way of thinking is found everywhere in the industry (why did everybody get flat screens although the 19″ CRT sell for less than 5 dollars?).
EDIT:
Many airlines operate fairly old airframes. Lufthansa has some average 15 year old A300-600 in stock, BA’s B747s are now topping the 15 year mark. Normally aircraft in mainline carriers are replaced after 15 years.
SchorschI suspected this aswell when the barrel mating issue came up , but now i attribute it to Media pressure . I have worked on so many open media projects like the F-22 , F-35 , 787 , V22 etc and nowhere have i seen more media pressure then commercial aviation specially in the seattle region .
I spent some time in Seattle (exchange student) in 2004/05, the time the business plan of the B787 surfaced. I think it was still called B7E7 back then. Anyways, the feeling in the Seattle region seemed to me twofold: On the one hand, people were positive that Boeing launches a new and most likely succesful commercial airliner, after years of losing market share and the hard lay offs in 2001/02.
On the other hand, the unconventional approach of producing the majority of labour intensive parts (wings, fuselage) outside Seattle and for a considerable part even outside USA, the feeling was that Boeing cheated on the Puget Sound region.
Later (after I left Seattle and the USA) I learned that many engineers and influential (= white collar) people at Boeing had strong feelings against the change of the company since MDD was overtaken (leading to the phrase: “MDD bought Boeing with Boeing’s money.”), like moving the headquarters to Chicago (still illogical to me).
This may lead to a group of people having strong opinion against the management. Additionally, the tough plan puts enormuos pressure on the involved people, and technical people see the “face-less management” as reason for technical problems caused by unrealistic cost targets.
For Airbus, the general attitude towards the company was more positive in the days of the A380, but now, with major cost cutting plans running, the attitude towards their employer has somehow sobered. Additionally, most technical people feel that A380 disaster was caused by bad management rather than faulty engineering (i. e., putting too much workload on the technical people in order to accomplish unrealistic business strategies).
The “media pressure” in time of A380 first flight was intense, too, with magazines speculating about many issues. It turned out that nearly all reports were wrong. But nothing comparable happened on the A380, which was after all late on its first flight (I won’t tell you how much, but I saw original projected first flight dates of the A380).
SchorschI’ll try to find a link but SpI is reporting through anonymous sources of 1 month delay on first flight (now october) due to complexity of integration . EIS is still claimed to be the same .
I am a bit surprised by the leaking information. Some people at Boeing seem not to adhere to company politics. The Seattle Intelligencer seems to have some sources “familar with the matter”. Let’s not forget the photos of the gap between the two barrels somewhere in June or so. Maybe somebody doesn’t like his new aircraft is being produced in many places except Seattle.
http://seattlepi.nwsource.com/business/327093_dreamliner10.html
SchorschI always like to use formulas! 😀
CD = CD0 + f*CA²
(f is a factor, which is in our region of interest constant)
So basically:
CD ~ CA²
or in words
drag is proportional to the square of lift.
CA = W/(rho*v²*S)
S: wing area (constant), rho: air density (independent of weight), v: airspeed, W: weight
W1=500klbs (which is something like the lowest possible flying weight of a B747).
W2 = 850klbs (which is something like maximum weight for any B747-200 at altitude)
rho=.5 kg/m³ (~28000ft)
S = 5500ft²
v: 250KIAS = M0.66 = 200m/s TAS
CA(W1=500klbs) = 0.45
CA(W2=850klbs) = 0.77
When you look at the graph above, you’ll see that Ca of W2 is actually outside the y-axis limit. I actually think it must be close to buffet onset boundary.
If we increase airspeed to 290KIAS, we have for W2:
CA = .57 with M=0.77.
SchorschFLYBYDONNI
It wouldn’t be able to glide 1200 miles, that’s here to North Africa
If an a/c wanted to glide for best range then it will fly at the best lift:drag ratio which is Vimd or velocity for minimum drag, if we remain here the glide angle will remain the same, however if the a/c is heavy then Vimd will be higher by a factor proportional to the square root of the weight increase.
So if we increase speed to a new Vimd the only thing that changes is the time in the air, you should maintain the same glide angle and the same distance covered on the ground, you’ll just meet the ground a bit quicker.
This is for still wind conditions, if we had a headwind then the best result would come by increasing your speed, the opposite for a tailwind.
There are graphs to work out the best speed to fly in certain conditions.The 744 as with any plane will have a glide ratio worked out from the above, it could be something like 1:10, this means for every 1,000ft lost in height it will travel 10,000ft horizontally, again if you do the maths 33,000ft will give a Horizontal distance of 330,000ft which works out about 63 miles in still wind conditions.
Hope this helps too
Dean
I’m totally confused as to how you can have a higher rate of decent but have the same glide angle and travel the same distance. Sorry, Deano, my poor little brain isn’t understanding!
Is there any way reply 9 can be explained in a different way so that stupid and simple people like me can vaguely comprehend it? :confused:
Paul
The weight determines the lift coefficient. Depending on that the optimum speed changes. Actually, a very light aircraft would achieve a less desirable glide ratio than a heavy one, although the lighter one has overally less drag.
The problem with glide ratios is that it puts lift (=weight in unaccelerated flight) in relation to drag.
That is basically what Deano said: To have more lift at best lift coefficent the speed has to be increased. The glide ratio will stay the same, but with the higher speed the vertical speed is higher.
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This is the drag over lift for the B747-200.
SchorschNewforest
Mate the Air Transat glided 21,500ft in 77nm (or 88.5 statute miles) to end up at 13,000ft 8nm from the runway threshold. This is a glide ratio of about 1:21 which is excellent.
Dean
The Transat also converted some speed. Basically the glide ratio of an A330 even exceeds 1:21, but under those conditions with wind-milling engines it wouldn’t achieve more than I think 14 – 18. With all conservatisms the glide ratio can be assumed 1:10 for an airliner, which then includes some margin. The aerodynamic glide ratio is normally much better (B747-200 is about 1:18, up to 1:20), but the drag of the engines and the external turbine, non-optimal trim and the normal difference between wind tunnel data and real life performance reduces glide efficiency.
And I agree Deano, it can not fly on one engine except maybe for some very remote conditions (basically empty).
SchorschFrom the Wall Street Journal:
BY end of September.
Small word, large meaning.
If I were to be pendantic, I would point out that means any time between now and the end of September.
Which is different from saying “Will be at the end of september.” Which is what you seem to want to infer.Anyway… even if its first flight is delayed, no biggy. From the entire project so far, I would guess Boeing have built in some buffer time.
Its got a long way to go before becoming a problem, is my take.
I am the last one who makes a big deal out of it. They should fly before November to evade embarassment. Anything else is within the unpredictable nature of aircraft development.
SchorschInteresting indeed. Can you point us in the direction of where you heard/ read that?
Google: “Boeing Dreamliner First Flight”
or
http://www.spiegel.de/international/business/0,1518,496622,00.html
No Airbus propaganda.
SchorschSome more interisting graphs. Maybe somebody likes to comment how those are connected to E-M theory.
First we see a climb profile using the energy method. dashed lines are lines of constant energy (for example: M1.6 at sea level is (theoretically) similar energy as 60.000ft without speed).
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And hey, I even found this one. Maybe someone likes to comment.
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SchorschIn the days prior to supersonic aircraft, the relationship between lift and drag is pretty predictable. However, as supersonic performance is introduced, the exchange between kinetic and potential energy now have to content with a non-linear energy loss around the transonic regime. Incorporating this, you get an adhoc relation called excess power (not exactly correct by definition but close enough). The amazing thing is now with different aircraft, the supersonic performance is different and temperature relationship versus altitude also becomes important (from energy equation of conservation laws)…hence that dip in the constant energy line. By following that dip and integrating, the optimal path in vertical manuver is NOT a straight climb! This excess power is also relevant in horizontal manuevers in more traditional ways (more power than you need is equal to acceleration you can get) but that “dip” pertains only to vertical manuevers.
As engineer with some basic education and experience in flight performance and aerodynamics it surprises me that this was news at one time. Today you can easily calculate SEPs and sustained Gs, provided you have some drag and thrust data (sounds easy, is hard to obtain actually if quality is supposed to be good).
The transonic “kink” is very visible, especially for early supersonic aircraft*.
Even for the F-16 the kink is visible, but less pronounced as for other aircraft.
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The maximum SEPs for a given altitude are often reached at high Mach numbers (at 30kft the above example has its best SEP (~=sust. G) at M1.5) is more due to increase of engine thrust in maximum power at high Mach numbers. Getting there would basically dry the tanks of a jet.
*: Early supersonic aircraft were characterized by low thrust-to-weight and often quite high transonic drag rises, resulting in a limited band were the sound barrier could be broken. Cruising this aircraft short of their maximum speed (~M.95 to M1) would result in poor excess power. Actually, the F-18 has similar performance limitations.
SchorschInterestingly Boeing has postponed the start of the flight test program to end of September by now.
SchorschSo it’s gonna be better than an F-16.. Is that the big deal? One surely does not need a CodeOne magazine to recognize that.
The sole truly remarkable achievement of the F-35 programme is the VTOL version. The rest makes me completely unimpressed.
Ot’s interesting that LockheedMartin bought General Dynamics with its Propaganda magazin Code One.
Actually, there are some very fine articles on the F-16 in the CodeOne archieve, especially when you are interested in the test pilot’s instruction’s on deep stalls and recovery.
SchorschWhat book are you reading? I might be able to get my hands on some more stuff for you, I am somewhat of a Boyd afficando. I just dont know if I brought it to Sweden with me or not. I’ll try to dig some stuff up. I’ll also try to write a summary of EM thoery when I am not drunk.
That would be very helpful.
I am reading:
Coram, Robert. Boyd: The Fighter Pilot Who Changed the Art of War. New York: Little, Brown, 2002.
SchorschAnd how would the Russians have arrived at these concepts later?:confused:
It was only because of many years’ hard won experience in the Vietnam War that forced the Americans to think seriously about the nature and future of aerial warfare including a-to-a combat.
F-15’s FF was 1971. Hence battle experience from Vietnam was only partly included. Shortcomings really became apparent in the operation rolling thunder, but ~5 years is a bit short to develop a new aircraft from the scratch.
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