Jawed From United States of America, joined Sep 2006, 482 posts, RR: 0 Posted (5 years 12 months 2 days 17 hours ago) and read 14195 times:
I often see people on the forums implying that the 757 is especially high-powered for its size. Is this really true? What is this sentiment based on? Amount of thrust per weight of the plane?
And if it is true, why did the 757 designers decide to build it that way? Wouldn't that be considered a waste of resources? After all, why should a plane be more high-powered than other similar planes, if there is no specific reason for it?
YOWza From Canada, joined Jul 2005, 4830 posts, RR: 16 Reply 1, posted (5 years 12 months 2 days 17 hours ago) and read 14179 times:
I believe the power was given to the 757 to provide optimal performance in so called "hot and high" locations. This power can be attributed to the power to weight ratio but I'm sure the skinny body and other aerodynamics are a factor.
Additionally the 757 leaves a more pronounced wake behind it than similar sized planes. I could be wrong but I believe that the FAA mandated separation for 757s is higher than similar sized planes.
When you factor in the additional seating capacity of the 757 over say the 727 or 737 the additional power and cost of that power are justified.
This is my understanding... I love 757s my favorite one being the combi operated by RA
Someone else is going to have to help me out here, but I believe the 757 has so much power because it was supposed to be a 727 replacement. The 757 needed to get off the same runways as the 727 efficiently so the plane has a bit more power. I'll try to look it up if noone else corrects me.
Viscount724 From Switzerland, joined Oct 2006, 23169 posts, RR: 23 Reply 4, posted (5 years 12 months 2 days 17 hours ago) and read 14098 times:
Quoting Futurecaptain (Reply 2): Someone else is going to have to help me out here, but I believe the 757 has so much power because it was supposed to be a 727 replacement. The 757 needed to get off the same runways as the 727 efficiently so the plane has a bit more power.
That's also my undertandikng that the 757 was mainly intended as a 727 replacement. The 727 was originally designed for use on runways as short as 5000 ft, thus the 727s complex triple-slotted flaps.
1337Delta764 From United States of America, joined Oct 2005, 6235 posts, RR: 2 Reply 6, posted (5 years 12 months 2 days 17 hours ago) and read 14048 times:
While the 757 was designed to be a 727 replacement, it instead replaced 707s and DC-8s on many domestic routes with U.S.-based airlines. Boeing did propose a 757-100 to directly replace the 727-200, but the 757-200 turned out to be too heavy to warrant a shrink. Boeing did not really offer a true 727 replacement until the 737-800 became available. The 737-400 was offered as an indirect 727 replacement, but was really more of a competitor against the MD-80. The A320 was really the first aircraft that was sufficient as a 727 replacement. Delta initially chose the MD-90 as their 727 replacement, however, with its lack of range and maintenance issues, Delta instead opted for the 737-800.
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Viscount724 From Switzerland, joined Oct 2006, 23169 posts, RR: 23 Reply 7, posted (5 years 12 months 2 days 17 hours ago) and read 13994 times:
Quoting ZTagged (Reply 5): I always thought it was because it shared everything but fuselage width with the 767..
It doesn't share its wings and engines with the 767 either. However, as I recall, the cockpit is basically identical and both the 757 and 767 were designed so they could be flown interchangeably by the same pilots.
Seabosdca From United States of America, joined Sep 2007, 4709 posts, RR: 4 Reply 9, posted (5 years 12 months 2 days 17 hours ago) and read 13909 times:
Yes, the 757 is high-powered. I'm bored and curious, so I'll make a chart. These are the thrust-to-weight ratios for various twin airliners, at the highest MTOW with the highest-thrust engine option (which is not the most common configurations in many cases, but I have to limit myself or I'll be here all day):
Many other factors besides thrust-weight ratio go into takeoff performance (especially wing design) but the numbers are still interesting. The 757, in addition to having all that thrust, has a large (and well-designed) wing for a plane its size.
I don't know the history of why the 757 was developed to have such outstanding field and climb performance. Someone else will have to answer that.
Most gorgeous aircraft: Tu-204-300, 757-200, A330-200, 777-200LR, 787-8
Ikramerica From United States of America, joined May 2005, 21313 posts, RR: 60 Reply 10, posted (5 years 12 months 2 days 16 hours ago) and read 13787 times:
Quoting Viscount724 (Reply 4): That's also my undertandikng that the 757 was mainly intended as a 727 replacement. The 727 was originally designed for use on runways as short as 5000 ft, thus the 727s complex triple-slotted flaps.
The 757 was created as a successor to the 727, and yes, to do some of it's roles. But it was a replacement for the 707/DC8s that were getting long in the tooth in airline fleets, for all the 3000nm and less routes those planes flew that didn't warrant the "luxury" of a widebody. EWR-transcons, MIA-west, etc. And there were plenty of those routes. The 757 also allowed airlines to economically expand into more of those kind of transcon and near transcon routes, as it was much cheaper to operate than other planes of that time that could do the same missions.
You didn't see lots of carriers replacing 727s with 757s, at least not at first. They flew side by side in many fleets for years (10-15) without carriers retiring 727s. The 757 took over the longer range roles while the 727 the medium range (DFW, ORD, STL hubs), and both were suitable for short runways or hot environments. And most carriers started finally replacing 727s with A320s and 738s.
This phenomenon was largely because the 727-200Advanced, which was the mainstay 727 in the 80s, was not old enough to need replacing at the time of the 757 EIS. When the 757 came out, the 722Adv first flown in 1972, were under 10 years old, and were designed to fly 20-25 years. With 900 of them delivered, that was a long time to wait for the 757 to become the 727 'replacement.' Many carriers, when they heard the 757 was going to replace the 727 on offer from Boeing, stocked up on 727s instead of jumping on the 757 bandwagon. Some it's best delivery years were right before it was phased out of production! Part of this had to do with ETOPS and the 727 being a tri-holer, meaning it could do what the 757 could not in many regions of the world. Also, the 727 was serviceable from the ground, still and important factor around the world in the late 70s and 80s, while the 757 was designed to fit into "first world" major airports where widebodies were serviced.
By the time the majority of 727 Advanced in service needed replacing (10-20 years after 757 EIS) the 757 itself was older technology compared to the A320 and 737NG, heavier with overpowered engines for many tasks. Now, some carriers with large 757 fleets continued to buy them to replace their oldest 727s in the late 80s/early 90s to avoid making the decision on the next fleet type, but they were only stalling, and the A320-200 and 738 were clearly targeted at the majority of 727 missions of that time: 2000 nm "longer" regional flights, and they were closer to the same size as the 727-200 than the larger 757-200. It's no coincidence that the 738 and 722 are certified for the same number of pax: 189...
And that is the story of how the 757-200, designed as the successor to the 727-200, found it's own niche in the world instead.
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I remember the first time I flew on a 717. Having been used to the DC-9s that FL had at the time, that rocket-like takeoff was a surprise.
I recently flew on a 757 for the first time in years and the takeoff really was like being shot out of a cannon. Full pax load too. I really didn't remember my two previous 757 flights being that way. Of course it may have had something to do with the departure patterns out of those airports (BOS and DCA).
FlyASAGuy2005 From United States of America, joined Sep 2007, 6872 posts, RR: 11 Reply 14, posted (5 years 12 months 2 days 16 hours ago) and read 13548 times:
Quoting Ulfinator (Reply 12): They say round here that the 757 is the closest thing to a fighter jet that Boeing Commercial ever made.
Nothing like riding in her on a half empty, 1 hour flight from a short field and you just rocket outta there. I must say though, the Mad Dog is pretty impressive also. I just REALY want to see Boeing make a viable single aisle 757 replacement.
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PanAm747 From United States of America, joined Feb 2004, 4242 posts, RR: 9 Reply 16, posted (5 years 12 months 2 days 15 hours ago) and read 13455 times:
Interestingly enough, no one has pointed out that the cruise speed of the 757 is somewhat lower than other large capacity planes, specifically the 767.
The angle of the 757 wing relative to the fuselage in an overhead view (the chord?) is less than other jets - in fact, I believe the 747's is the MOST swept back short of the Concorde. The less of a sweep-back, the lower the take-off speed, and vice versa. However, once airborne, the more the angle, the faster the cruising speed.
As I was told by a pilot, the 757 IS overpowered with certain engines. When coupled with THAT much power and a low take-off speed, you get a plane that is rarely if ever weight restricted on most of its routes. Certainly out of PHX and LAS in summer (with the exception of Hawai'i routes) a 757 gives the passenger the LEAST chance of being bumped due to weight restrictions.
Quote: It doesn't share its wings and engines with the 767 either. However, as I recall, the cockpit is basically identical and both the 757 and 767 were designed so they could be flown interchangeably by the same pilots.
Cross-certification is possible on the 757 (step down into the cockpit) and the 767 (step up into the cockpit.
Quote: The 727 was originally designed for use on runways as short as 5000 ft, thus the 727s complex triple-slotted flaps.
Eastern and United were the launch customers for the 727, but they had VASTLY different needs for the plane. Eastern wanted an aircraft capable of taking off fully loaded with 100+ passengers from LGA's shortest runway and fly non-stop to Miami. United needed an airplane capable of taking off fully loaded from DEN Stapleton's shortest runway in the "hot and high" conditions.
Boeing developed the concept of "lift devices" - being able to increase the wing area by as much as 25% to lower the take-off speed, but retracting them after lift-off to enable a high speed cruise. This helped make the 727 enormously successful, and the same technology was fitted to the 757.
Coupled with an amazing increase in engine technology (MUCH more thrust!!), you have an over-powered sled rocket.
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Aerobalance From United States of America, joined Sep 2000, 4664 posts, RR: 50 Reply 19, posted (5 years 12 months 2 days 15 hours ago) and read 13349 times:
Quoting EXAAUADL (Reply 15): In 1995 on a cold Saturday evening in October a flew a AA 757 from BOS-DFW with like 25 passengers on board...we were off in like 20 seconds.
About 7 years ago I was on a DL 757 from LAX-LAS at 6:30am on a Saturday in December. There were 7 passengers on board. The pilot went for it since we were airborne in no time flat, pitch angle was not moderate, but extreme - it felt like a SNA departure, as we lifted off. From my window-seat on the starboard side I could see the theme building, the top of theme building as we were streaking upwards at a great climb rate. The plane ended up leveling off at the mandated 2500 ft. restriction BEFORE we got to the end of the runway. Damn, that was awesome. I confronted the crew as I left the plane in LAS and they confirmed what they did with a smile. As I pilot I told them I appreciated what they did - that was a serious departure.
PanAm747 From United States of America, joined Feb 2004, 4242 posts, RR: 9 Reply 20, posted (5 years 12 months 2 days 15 hours ago) and read 13338 times:
Quote: Chord is the linear distance from the leading edge to the trailing edge of a wing. The angle of the wing to the fuselage is called sweep. The 757's wing is swept at 25 degrees.
Thank you!! I knew it had something to do with it, but I couldn't remember off-hand the words.
As I recall, isn't the 747's sweept 37½ degrees?
And further, I seem to remember that when the 727 was first introduced, it scared some military controllers because it flew at then-unheard of speeds for passenger planes. While not 37½ degrees sweep, it's more than a 757's, yes?
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Brucek From United States of America, joined Nov 2004, 255 posts, RR: 0 Reply 22, posted (5 years 12 months 2 days 15 hours ago) and read 13287 times:
Quoting Ikramerica (Reply 10): And that is the story of how the 757-200, designed as the successor to the 727-200, found it's own niche in the world instead
This is one of the best explnantions I've seen for the niche market that the B757 has developed for itself.
I flew a UA B752 from LAX to DEN recently, and continue to be amazed at the thrust. A fully loaded aircraft, when given a burst of thrust to unstick it from a stationary position oushed us all into the back of our seats