Jawed
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757 High-powered? Why?

Fri Dec 14, 2007 7:51 pm

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?
 
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yowza
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RE: 757 High-powered? Why?

Fri Dec 14, 2007 7:59 pm

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

YOWza
 
futurecaptain
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RE: 757 High-powered? Why?

Fri Dec 14, 2007 8:01 pm



Quoting Jawed (Thread starter):
Amount of thrust per weight of the plane?

Yes, thrust to weight ratio is generally the way to determine how powered a plane is.

Quoting Jawed (Thread starter):
why did the 757 designers decide to build it that way?

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.
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ikramerica
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RE: 757 High-powered? Why?

Fri Dec 14, 2007 8:09 pm



Quoting YOWza (Reply 1):
Additionally the 757 leaves a more pronounced wake behind it than similar sized planes.

Part of this comes from the narrow wingspan vs. the thrust amount. One way the A380 decreases it's wake profile is that it has 50 feet wider wings than the 744/A346/77W.
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Viscount724
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RE: 757 High-powered? Why?

Fri Dec 14, 2007 8:12 pm



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.
 
zTagged
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RE: 757 High-powered? Why?

Fri Dec 14, 2007 8:14 pm

I always thought it was because it shared everything but fuselage width with the 767..  rotfl 
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1337Delta764
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RE: 757 High-powered? Why?

Fri Dec 14, 2007 8:19 pm

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
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RE: 757 High-powered? Why?

Fri Dec 14, 2007 8:24 pm



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.
 
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RE: 757 High-powered? Why?

Fri Dec 14, 2007 8:25 pm

Given enough THRUST, lift is irrelevant Big grin Big grin Big grin Big grin

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seabosdca
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RE: 757 High-powered? Why?

Fri Dec 14, 2007 8:39 pm

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):

717-200HGW: 0.347
757-200: 0.341
737-700: 0.340
A310-300: 0.326
A300B4-605R: 0.325
MD-90-50: 0.325
A319: 0.324
A321: 0.320
A318: 0.320
757-300: 0.319
A320: 0.318
767-200ER: 0.314
737-800: 0.313
777-200LR: 0.301
767-300ER: 0.301
777-300ER: 0.297
737-900ER: 0.290
777-200ER: 0.285
767-400ER: 0.282
A330-200 and A330-300E: 0.280
MD-87: 0.268
MD-83: 0.263

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.
 
ikramerica
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RE: 757 High-powered? Why?

Fri Dec 14, 2007 8:57 pm



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.  Smile
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RE: 757 High-powered? Why?

Fri Dec 14, 2007 9:08 pm



Quoting Seabosdca (Reply 9):

717-200HGW: 0.347

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).
 
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RE: 757 High-powered? Why?

Fri Dec 14, 2007 9:26 pm

They say round here that the 757 is the closest thing to a fighter jet that Boeing Commercial ever made.
 
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RE: 757 High-powered? Why?

Fri Dec 14, 2007 9:38 pm

Seabosdca any chance you could put up the thrust to weight ratio for the A340-300?  Smile
 
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RE: 757 High-powered? Why?

Fri Dec 14, 2007 9:47 pm



Quoting Ulfinator (Reply 12):
They say round here that the 757 is the closest thing to a fighter jet that Boeing Commercial ever made.

 bigthumbsup   checkmark 

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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EXAAUADL
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RE: 757 High-powered? Why?

Fri Dec 14, 2007 9:59 pm

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.
 
PanAm747
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RE: 757 High-powered? Why?

Fri Dec 14, 2007 10:03 pm

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.

 checkmark 

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.  bigthumbsup 
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DfwRevolution
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RE: 757 High-powered? Why?

Fri Dec 14, 2007 10:11 pm



Quoting PanAm747 (Reply 16):
The angle of the 757 wing relative to the fuselage in an overhead view (the chord?) is less than other jets

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.
 
gigneil
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RE: 757 High-powered? Why?

Fri Dec 14, 2007 10:14 pm



Quoting PanAm747 (Reply 16):
Cross-certification is possible on the 757 (step down into the cockpit) and the 767 (step up into the cockpit.

They are, in fact, the same type rating.

NS
 
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RE: 757 High-powered? Why?

Fri Dec 14, 2007 10:27 pm



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.
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RE: 757 High-powered? Why?

Fri Dec 14, 2007 10:29 pm



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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seabosdca
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RE: 757 High-powered? Why?

Fri Dec 14, 2007 10:35 pm



Quoting Popski777 (Reply 13):
Seabosdca any chance you could put up the thrust to weight ratio for the A340-300?

The ratios for trijets and quads will always be lower because airplane thrust requirements are calculated based on a one engine out scenario. With that in mind, and drifting offtopic:

Trijets

L-1011-500 0.302
MD-11ER 0.295
DC-10-30 0.267
727-200 Adv 0.248 (proving that it was the big lift that gave the 72S its remarkable field performance)

Quads

A340-600HGW 0.286
747-400ER 0.278
747-8 0.274
747-100 0.273
A340-500HGW 0.267
A380-800 0.260
Il-96-300 0.256
A340-300E 0.223
 
brucek
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RE: 757 High-powered? Why?

Fri Dec 14, 2007 10:38 pm



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  Smile

Bruce.
 
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RE: 757 High-powered? Why?

Fri Dec 14, 2007 10:39 pm



Quoting YOWza (Reply 1):
This is my understanding... I love 757s my favorite one being the combi operated by RA

I believe this was the only B752 combi ever made.

Bruce.
 
N1120A
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RE: 757 High-powered? Why?

Fri Dec 14, 2007 10:43 pm



Quoting Jawed (Thread starter):
Wouldn't that be considered a waste of resources?

Given that the 757 is still, 25 year later, one of the most efficient aircraft in the sky, I don't think it was.

Quoting 1337Delta764 (Reply 6):
The 737-400 was offered as an indirect 727 replacement, but was really more of a competitor against the MD-80.

The MD80 and 734 were both nearly direct 727 replacements. The A320 and 738 took it a step further.

Quoting Srbmod (Reply 11):
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.

It is almost like the jump off the runway.

Quoting PanAm747 (Reply 16):
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.

Actually, the 757's cruise speed isn't particularly slow. Mach .80-.82 is similar to that of the 767
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Viscount724
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RE: 757 High-powered? Why?

Fri Dec 14, 2007 10:45 pm



Quoting N1120A (Reply 24):
Quoting Jawed (Thread starter):
Wouldn't that be considered a waste of resources?

Given that the 757 is still, 25 year later, one of the most efficient aircraft in the sky, I don't think it was.

However it's heavier that it has to be for a large number of the routes it operates.
 
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seabosdca
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RE: 757 High-powered? Why?

Fri Dec 14, 2007 10:52 pm



Quoting N1120A (Reply 24):
The MD80 and 734 were both nearly direct 727 replacements. The A320 and 738 took it a step further.

...a necessary step. The vastly better fuel efficiency benefited everyone. The better range finally allowed US carriers, in particular, to use one fleet type for both transcon and shorter-range missions.

Especially in the era of low oil prices, there was really no compelling reason to replace a 72S with a 734 or M80. The A320 and 738 are a different story.

Quoting Viscount724 (Reply 25):
However it's heavier that it has to be for a large number of the routes it operates.

...which makes it all the more remarkable that no one has been able to develop a competitive replacement for it. The A321 and 737-900ER are more economical, but by a smaller margin than you'd think -- and every major 757 operator has at least a few missions requiring performance the lighter aircraft can't achieve.
 
Tristarsteve
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RE: 757 High-powered? Why?

Fri Dec 14, 2007 11:11 pm

One thing I think you are all missing is which engines were available in 1980?
There wasn't much of a choice.
there was the CFM56-2 which was too low powered at 21000 lbs thrust.
and the Trijet engines RB211-524, JT9D and CF6 which were about 50000lbs.
There was nothing in between. So RR and PW both offered a 50000 lb engine with a smaller fan
which ended up being about 38000lbs thrust.
The B727 had 3 JT8s at 17000 or total 51000lbs and the B757 ended up two at 38000 with total 76000lbs.
For a twin this was as low as you could go. So the B757 became an overpowered twin.
 
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1337Delta764
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RE: 757 High-powered? Why?

Sat Dec 15, 2007 12:17 am



Quoting N1120A (Reply 24):
The MD80 and 734 were both nearly direct 727 replacements.

I wouldn't really call either aircraft true 727 replacements. With the exception of the MD-83, they offered less range than the 727-200. Most U.S. airlines who ordered the MD-80 in the 1980s and early 1990s continued to operate the 727 until the early 2000s.

Does anyone know of an airline who replaced their 727s with either the MD-80 or the 737-400? I know Delta initially envisioned the MD-90 as their 727 replacement, but due to the MD-90's reliability issues and lack of range, the remaining orders were cancelled in favor of the 737-800. The A320 primarily dominated the 727 replacement market in the early-to-mid-1990s, until the 737-800 came out as a viable competitor.
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Tango-Bravo
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RE: 757 High-powered? Why?

Sat Dec 15, 2007 1:27 am



Quoting Ulfinator (Reply 12):
They say round here that the 757 is the closest thing to a fighter jet that Boeing Commercial ever made.

In the early days of 757 service with Northwest (mid-late 1980s), my most vivid MSP memories of the type is what seemed like their near vertical climbouts that commenced immediately after takeoff. Not unlike a pair of F-16 fighter jets of the "Happy Hooligans" unit of the Air Force Reserve (or North Dakota Air National Guard) I observed one day doing touch and gos at FAR.
 
deltal1011man
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RE: 757 High-powered? Why?

Sat Dec 15, 2007 3:52 am



Quoting 1337Delta764 (Reply 28):

Does anyone know of an airline who replaced their 727s with either the MD-80 or the 737-400? I know Delta initially envisioned the MD-90 as their 727 replacement, but due to the MD-90's reliability issues and lack of range, the remaining orders were cancelled in favor of the 737-800. The A320 primarily dominated the 727 replacement market in the early-to-mid-1990s, until the 737-800 came out as a viable competitor

it was more range the MD-90s are pretty reliable...........plus Boeing was on hands and knees to get DL to order the 738 and drop the 90s
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MCOflyer
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RE: 757 High-powered? Why?

Sat Dec 15, 2007 4:05 am



Quoting Ulfinator (Reply 12):
They say round here that the 757 is the closest thing to a fighter jet that Boeing Commercial ever made.

Amen to that. I love this plane for the pocket rocket take offs as I call them.

I remember taking off from MCO with bound for PHL with less pax (I recall the pilot calling this a light load)and the take off felt like being released from a sling shot. When we lifted off, I could see Terminal A. I asked the pilots why we did this type of takeoff and their reply was that ATC had issued long taxi times and had a break for us as we were a 752. That explains the fighter pilot maneuvers for avoiding nearby a/c when we took off.

Hunter
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dl757md
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RE: 757 High-powered? Why?

Sat Dec 15, 2007 4:20 am



Quoting DeltaL1011man (Reply 30):
it was more range the MD-90s are pretty reliable

Range was an issue, but so was reliability ie. mtc. Some of the mtc issues have never been ironed out and the 90 still to this day has by far the worst TDR of all fleet types at DL.

Quoting DeltaL1011man (Reply 30):
plus Boeing was on hands and knees to get DL to order the 738 and drop the 90s

I'll go with that.

DL757Md
757 Most beautiful airliner in the sky!
 
AirEMS
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RE: 757 High-powered? Why?

Sat Dec 15, 2007 5:29 am

All I can say is long live the 757! It is my favorite aircraft sooooo many memories I love it! It sad that they don't make it anymore!!

-Carl
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TWA757
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RE: 757 High-powered? Why?

Sat Dec 15, 2007 5:57 am



Quoting Aerobalance (Reply 19):
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.

That's an awesome story! Wow. Love the 757.
 
NWAROOSTER
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RE: 757 High-powered? Why?

Sat Dec 15, 2007 6:40 am



Quoting Ulfinator (Reply 12):
They say round here that the 757 is the closest thing to a fighter jet that Boeing Commercial ever made.

Apparently you have not flown in a 727-100 or DC-9-10. They can be pocket rockets.  old 
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dl757md
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RE: 757 High-powered? Why?

Sat Dec 15, 2007 7:37 am



Quoting Nwarooster (Reply 35):
Apparently you have not flown in a 727-100 or DC-9-10. They can be pocket rockets.

While I'm quite sure they are great performers, I doubt they can come very close to matching a 757. I'll share one of my more memorable experiences with the aircraft. I was working line mtc. in SLC and we had a 57 IFSD going into RNO on a flight from ATL. I was sent to RNO to remove the oil filter and ship it to ATL for analysis. My ride from SLC was the 57 that was ferrying to RNO to make up the return flight to ATL. Imagine, a 57 with just me, my tools, two pilots, and about 14K lbs of gas. No pax, FAs, or bags. I've always loved flying jumpseat and do whenever I can. This time was no exception. Well the captain wasn't game for a max power TO and instead programmed the FMS with our weights and let it handle the throttles. I intently watched N1, the airspeed and vertical speed during TO and the initial climb. I also timed our TO roll. Don't forget, SLC is at 4220' above sea level. This was a summer morning with the temp already 83 deg F at 7AM. During TO our N1 was steady at only 82%, yet we broke ground in an amazingly short 14 seconds and proceeded to climb at 6000 ft/min! 12 minutes later we were at FL370. I was floored! I can only imagine what kind of ride we would have had, had he used max TO power.  bigthumbsup 

DL757Md
757 Most beautiful airliner in the sky!
 
Seafleet
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RE: 757 High-powered? Why?

Sat Dec 15, 2007 7:46 am

I remember my first flight on a 757 as the most stuning take off ever, the captain came on the pa and told crew we where doing a rolling take off so basically sit your arse down fast.
Wow the power it is the only civilian flight where I felt truly pressed back into my seat.
I subsequently talked to a 757 training captain who told me the temptation was always to put the throttles through the gate to find out what it really could do but they where not allowed so occasionally he had to find a training scenario to give it a go.
I was invited onto one such flight and all I can say is that it was the nearest I am ever going to get to a military take off Smile
At age 61 I now indurstand obsolecence but I will mourne the passing of the 757.
Roger
 
mbj2000
Posts: 295
Joined: Thu Dec 15, 2005 5:15 am

RE: 757 High-powered? Why?

Sat Dec 15, 2007 2:35 pm



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.

I remember flying in the mid-90s from ORD to LAX in a UA 757 with about 10-20 people on board. It was the first and last time I got really dizzy during take-off, I literally felt how the blood rushed to my feet leaving my head empty...  Smile
Like most of life's problems, this one can be solved with bending -- Bender Unit 22
 
airbazar
Posts: 6936
Joined: Wed Sep 10, 2003 11:12 pm

RE: 757 High-powered? Why?

Sat Dec 15, 2007 2:51 pm



Quoting Seabosdca (Reply 26):
...which makes it all the more remarkable that no one has been able to develop a competitive replacement for it.

I think the correct wording should be "no one has wanted to build a replacement". If there was a market for it either Boeing and/or Airbus would have built a "true" replacement. As I pointed out not too long ago, there are very few passenger 757 operators left and a lot of them have been replacing them with A320/737 aircraft. Over the last 20 years the airline industry has fragmented tremendously and consequently the 757 is now too much of an aircraft for most of the routes it was initially used on. With oil approaching $100/bbl and increased competition airlines can't afford to be flying airplanes at 70% capacity.
 
Western727
Posts: 1428
Joined: Wed Jan 03, 2007 12:38 pm

RE: 757 High-powered? Why?

Sat Dec 15, 2007 2:55 pm



Quoting TristarSteve (Reply 27):

Very interesting point and one that does make sense. Another circumstance I once heard/read about was that EA, being a launch customer with a hub at DCA, pressured Boeing to beef-up the thrust to weight ratio enough for it to be able to take off from DCA w/o weight restrictions and ample range to reach points the 757 is able to reach.

Still, if what I mentioned is true, that brings up a curious point: didn't DCA have the range cap back then, anyway? That would've rendered moot EA's supposed push for superior engine power...
Jack @ AUS
 
AA 777
Posts: 706
Joined: Thu May 30, 2002 9:34 am

RE: 757 High-powered? Why?

Sat Dec 15, 2007 3:00 pm

I'll add to the stories.....

I was spotting at JFK one morning when an AA 757 was ferrying to an unknown destination. The pilot asked the tower for an unrestricted climb to 5 or 6 thousand - I forget. Since it was a quiet Sunday morning he was able to get it and I've never seen an airliner climb like that. He took off 31L and by the time he got to the spotting location at Howard Beach he was leveled off. It was one of those moments you just with you had filmed. Long live the 75!
CRJ-700 FO
 
Rj111
Posts: 3007
Joined: Wed Sep 08, 2004 9:02 am

RE: 757 High-powered? Why?

Sat Dec 15, 2007 3:15 pm

It's one of the largest short haul jets about. Short haul flights spends proportionally more time climbing that cruising. And as climbing is an incredibly fuel hungry part of a flight, it's important to that the 757 is geared up for an efficient takeoff.

Also, in the RB211's case (which is the main culprit for the 757s high thrust to weight ratio), this engine had already been developed for the L1011 and RR opportunistically used it for the 757. Being 'off the shelf' it was not optimized for the 757 and it's high power was detrimental to its fuel efficiency. However, because the engine is never really pushed to it's limits, it has an excellent on-wing time and this saves money. Contrast that to the PW2000 which despite being more efficient, had poor reliability at first.

Quoting N1120A (Reply 24):


Quoting Jawed (Thread starter):
Wouldn't that be considered a waste of resources?

Given that the 757 is still, 25 year later, one of the most efficient aircraft in the sky, I don't think it was.

It's still a competent aircraft and has certainly stood the test of time. But saying it's one of the most efficient in the sky, is somewhat flattering i feel.
 
bobprobert95
Posts: 29
Joined: Tue Feb 27, 2001 12:44 pm

RE: 757 High-powered? Why?

Sat Dec 15, 2007 5:31 pm

It's really fun to fly the 757 out of SXM. You really can feel the power there!
 
MCOflyer
Posts: 7071
Joined: Tue Jun 13, 2006 5:51 am

RE: 757 High-powered? Why?

Sat Dec 15, 2007 5:55 pm

I'll ad a story myself. To begin, I was connecting through CLT and when I boarded the cabin was full to the brim. Well, I thought this is a 757 so it is going to be a fun ride. The captain came on and did his brief to the pax and in the end said we will arrive in MCO ahead of time and be prepared for a quick departure.The Captain must have had the throttles pegged as we took off fairly quickly. We arrived in MCO 1h15min later. I asked the Captain why he had done such a takeoff, and his remark was that not everyday do you get to show off an a/c capability to the paying customers/clients. I thanked him for that takeoff felt better than the average roller coaster.

Hunter
Never be afraid to stand up for who you are.
 
jenkingeorge
Posts: 34
Joined: Wed Apr 11, 2007 1:10 am

RE: 757 High-powered? Why?

Sat Dec 15, 2007 5:55 pm

I reject your reality and substitute my own!
 
fsnuffer
Posts: 175
Joined: Wed Jun 20, 2007 5:38 am

RE: 757 High-powered? Why?

Sat Dec 15, 2007 6:26 pm

From what I understand, one of the design requirments was the 757 needed to able to land and take off from LGA and DCA
 
juanchopancho
Posts: 37
Joined: Wed Dec 01, 2004 4:09 am

RE: 757 High-powered? Why?

Sat Dec 15, 2007 6:33 pm

Whoever said the 757 cruise speed is lower than the 767 is wrong. They're exactly the same.

Normal cruise speed for the 757/767 is MACH .80
 
c680
Posts: 428
Joined: Sat Apr 23, 2005 6:03 am

RE: 757 High-powered? Why?

Sat Dec 15, 2007 9:04 pm

Some interesting numbers on some smaller jet aircraft:
Trust/weight (MTOW) ratios

F-15C/D 0.734  Smile
Cessna Citation Sovereign 0.380
Cessna Citation X 0.375
Gulfstream 450 0.375
Gulfstream 500 0.361
ERJ-135 0.355
E-170(STD) 0.348
CRJ-200 ER 0.342
B757-200 0.341
LearJet 45 0.341
CRJ-700 ER 0.337
Falcon 900EX 0.311
My happy place is FL470 - what's yours?
 
Arrow
Posts: 2325
Joined: Wed Jun 19, 2002 7:44 am

RE: 757 High-powered? Why?

Sun Dec 16, 2007 6:56 am



Quoting C680 (Reply 48):
Some interesting numbers on some smaller jet aircraft:
Trust/weight (MTOW) ratios

That should spark some interesting comments, especially when that "dog" of a CRJ200 appears to have a slightly better ratio than the 757. And I'm sure I've seen a couple of pilot comments about the CRJ700 being a real rocket. Kinda makes you realize just how equally important wing shape and flaps/slats are if you want a rocket-like take-off.
Never let the facts get in the way of a good story.

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