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Dougal

Bit of a Dumb Question

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I don't really understand what major differences there'd be between the larger 737NGs and the 757 series. There's not a huge size difference, though I don't know about the range. They just seem remarkably similar.Obviously they're not, else they wouldn't both exist. I'd be grateful for putting 'straight' on the matter. I know I could check the boeing site, but not sure my failing brain could manage all the technical data.Thanks

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They are physically similar in size*, but the 757 can fly farther and take off heavier than the 737NG, and has a typical cruise speed just a little faster than the 737 (0.80 Mach vs 0.78 Mach).All this was just comparing Boeing's specs for the two families.* Comparing the 757-200 to the 737-900. The 757-300 is far longer than any NG.

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They are very similar, but the main differences are relevant to how an airline would use them.The 757 has a greater range than all 737s, with only the 737-900ER coming close to it thanks to two additional fuel tanks. The 900ER also had additional doors added to allow it to carry over 200 passengers, which was a legal certification requirement (it can carry up to 215 passengers now), which on the face of it would seem to make it pretty close to the smaller 757 variants. However, the 757 is not really designed for 'sector work' as the 737 is, so the 737 has a lower maximum speed because the highest cruise speed is not considered essential for an aircraft that typically flies multiple short sectors rather than one long flight. This is what confuses people with the Extended Range model 737, yes it has extended range, but mostly so that it can fly a lot of short flights without refuelling rather than one very long one, which is also why it has tougher construction and stronger landing gear, it can land much heavier than a 757 could. That ability enables the 737 to be turned around quicker on the ground by not having to refuel, which is why you see budget airlines using the 737; less time on the ground equals more time in the air making money for airlines on tight budgets (although the 737-900ER certainly could make a long flight, it would not be as timely or economical as the 757 in that regime because of its lower cruise speed).The other main difference in operation is short field take off performance. All current NGs now have the short field take off performance kit (which used to be optional), this means that they can get more weight off a short field than a 757 could, even though a 757 has a higher MTOW. That's important again for regional budget airlines, because they invariably want to operate from cheaper less centralised airports to avoid high landing fees, so they can pass those savings on down through lower ticket prices, and smaller, less expensive airfields usually have shorter runways. That's also why despite the fact that the 737NG is used for simple rugged operations, it has probably the most modern sophisticated avionics you can get, because it needs all the help it can get when operating from places with limited ground-based aids.Al

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The 757 was designed as a direct replacement for the 727.

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Very many thanks for such detailed replies. It clarifies what I didn't understand.

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Well, you asked an excellent question.There is no doubt the 737NG's capabilities killed the 757-200. It could do 70% of the mission at a much lower acquisition and maintenance cost, although the 757 remains a better choice based on pure cost per seat mile and performance.When the 757 and 767 were built it was truly revolutionary to be able to carry 240 to 260 persons over an ocean with less hourly fuel burn than a 727, the same or better short field performance and with additional efficiencies of being able to operate the thing with two pilots. While you think getting rid one of one pilot saves $120,000 a year (back then the equivalent of roughly $250,000 today) consider that to fully staff the airplane domestically requires about 6 crews today. With International work rules and extended range operations staffing could be 8 to 12 crews per aircraft, so the savings in pay, benefits and training add up.The only reason I bring this up is because the ease of operation and commonality with the 767 make the 757 a pretty complex airplane, systems wise, to build and maintain. It is a very reliable platform, but not nearly as cheap as the much simpler 737 to maintain. The battle over the third pilot on the 737 had already been won by Boeing, so there was no need to automate the 737 to the level of a 757.Also, the earlier generation 737-400 to -600, even with the new turbofan engines did not have the wing the NG has and was ~ 20% more expensive to operate than a 757. The A 319/320 forced Boeing to compete and to beat the A320, Boeing built an improved 737 that was not only an AirBus competitor, but also a 757 competitor for far less money.Northwest / Delta Air Lines is parking two dozen or so 757's because of maintenance costs as the airplanes age. It was designed for a 25 year life span and airlines have used it hard and they are coming up on expensive inspections to continue in service.The 737NG by virtue of its popularity has been assembled automotive style on a production line that pops out one (or more) per day with only 5,500 hours of labor. The economies of scale on this mass produced airplane are, I think, unique in the history of aviation.But the 737 is no 757. It does not perform as well off a short field (higher V speeds, brakes not as effective, although the 737-700 holds its own in the hot and high department) The 737 burns more fuel per seat mile and just has stuff crammed everywhere. The 737 cockpit is noisy and cramped with no room for even the co-pilot's bag, the overhead panel and systems a little on the archaic side and IMHO, not quite as safe an airplane as the 757 due to reduced levels of redundancy. The 757 is VERY pilot friendly, very nicely coordinated controls, has an amazingly friendly wing with more lift than you can imagine, and easy to handle on the ground. There is plenty of room behind the pilots seats and plenty of closet space.I recently lost my 767/757 seat for a position on the 737 as our airline reduced capacity and while I'm sure I'll grow to love the 737, it sure aint a 75.

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Also, the earlier generation 737-400 to -600, even with the new turbofan engines did not have the wing the NG has and was ~ 20% more expensive to operate than a 757. The A 319/320 forced Boeing to compete and to beat the A320, Boeing built an improved 737 that was not only an AirBus competitor, but also a 757 competitor for far less money.
The -600 model is a NG and is built off of the -500 model fuselage.
But the 737 is no 757. It does not perform as well off a short field (higher V speeds, brakes not as effective, although the 737-700 holds its own in the hot and high department) The 737 burns more fuel per seat mile and just has stuff crammed everywhere. The 737 cockpit is noisy and cramped with no room for even the co-pilot's bag, the overhead panel and systems a little on the archaic side and IMHO, not quite as safe an airplane as the 757 due to reduced levels of redundancy. The 757 is VERY pilot friendly, very nicely coordinated controls, has an amazingly friendly wing with more lift than you can imagine, and easy to handle on the ground. There is plenty of room behind the pilots seats and plenty of closet space.
You should see the GOL 737-800's with redesigned flaps, spoilers, new calipers and carbon brakes. Can use less then 5,000' of runway in nearly all conditionshttp://www.boeing.com/news/releases/2006/q3/060729a2_pr.htmlhttp://www.boeing.com/news/releases/2006/q3/060729a_nr.html

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