757 series or A320 series

[PowerRanger]

Well, an A320 can weigh up to 170K and has between 44,000 and 54,000 lbs of thrust.

A 757-200 maxes out at 255,000 lbs and has between 73,200 and 87,000 lbs of thrust.

Each airplane has a bunch of engine and weight variations...

A 75-200 with the big motors has a thrust to wt. ratio of 2.93

An Airbus 320 with the big motors has a thrust to wt. ratio of 3.14

Hmmm


Of course thrust to wt. is only part of the equation. Some variations may have lighter airframe wts with higher thurst engines. Airframe aerodynamics is the other, as I have flown smaller jets with lower T to W ratios of similar sized small jets, and the lower powered bird with the better airframe design won out in several areas.

ymmv...

Well that's interesting to read. Everything that I have read was that the P&W and RR engines on the 757 were about 36-45,000 lbs. of thrust.

Definately not arguing with you,just never heard the thrust was so high on the 757 engines!

 

[ultrarunner]

Yes, 36,000 lbs to 43,000 lbs of thrust PER MOTOR. On the -200 there are two pratt variants and two rolls variants.

The two pratts are 36.6 and 40.1
The two Rolls are 40.2 and 43.5

Those thrust ratings are PER MOTOR. And, as you know, the 75 has two motors.

You should be up to speed now in checking my calculations.

 

[PowerRanger]

Yes, 36,000 lbs to 43,000 lbs of thrust PER MOTOR. On the -200 there are two pratt variants and two rolls variants.

The two pratts are 36.6 and 40.1
The two Rolls are 40.2 and 43.5

Those thrust ratings are PER MOTOR. And, as you know, the 75 has two motors.

You should be up to speed now in checking my calculations.

Gotcha!

 

[ultrarunner]

Engine manufactures also developed two engines for the Airbus A320:

The CFM56 and the IAE V2500.

The thrust ratings on those engines varied between 22,000 lbs and 27,000 lbs of thrust per engine.

The airlines demand and incredible amount of flexibility...and for the money they spend on airframes and engines, they can dictate quite a bit.

For example, an airline may need to operate a lighter airframe out of certain airports to avoid costly fees that are associated with higher weight airframes. By utilizing a lighter weight airframe with a higher thrust engine, may enable the airline to fly X number of bodies X miles which that airport market may demand, without exposing the airline to the added fees of operating a heavier airframe.

That's just one example of many.

Hope this helps you a bit.

 

[Benhuntn]

One big factor is the wing sweep. The 757 is 25 degrees and the A320 is 35 degrees. The A320 will cruise faster, the 757 will cruise more economically. It also improves the climb perfromance with the less swept wing.

 

[MrSuupaFly]

The B757 has a higher MMo than the A320.

 

[Whine Lover]

Thrust-To-Weight...A Primer:

I am a Large Fat Man. I have Mass. Once set in motion, the "Thrust" Level becomes quite impressive.

In fact, my second Ex-Wife once required Dental Work due to an unauthorized re-entry procedure, utilizing a "skip" method from the "Taint" Area.

Now, only utilizing 4.5 inches of Instrument, I was able to "Pile Drive" ( If you will ) several incisors from said recipients forward Dental Appendages.

Mass and Inertia. "The Fat Man's Friend."

But, I digress...


YKW

 

[elag777]

Interesting web site to check out the IAE product


http://www.v2500.com/engine/index.shtm

 

[FL420]

This hasd been covered in a previous thread so forgive me if I just borrow from my previous post(s.) I only have firsthand experience with the A320 and the B757 so can only compare the two.

In general, my ideal single-aisle airliner would be the B757 Rolls-Royce engines, wing and brakes mated to the A321 fuselage and flightdeck, systems design philosophy, fly-by-wire with sidesticks and engine FADEC's.

Specifically:
Flat floor w/o seat tracks that try to twist your ankle and rip the heels off your shoes. You can also spread a blanket on the carpeted floor and sleep behind the seats on those long augmented out and back turns. Score one for the Bus.

Dark overhead panel philosophy with mostly flat pushbutton switches to minimize damage to your head if you forget to duck. Great human factors engineering with flow lines for systems. Score one for the Bus.

Much better design on cup holders, pilot sunshades and side window shades on the A320. Score one for the Bus.

Sidesticks allow you to put the aircraft where you want it to go with just minute movement of the wrist. You do need to properly adjust your armrest. Score one for the Bus.

The tray. What can I say? It holds a lunch, a laptop and all the paperwork we still have to do flying internationally. You can cross your legs and spin around in your seat. Score a big one for the Bus.

The Intel 8086(or 8088) processor on the earlier A320's was way too slow. It was very easy to out-type the processor and just when you went to line-select a scratchpad entry, the waypoints would re-shuffle and your entry would end up on the wrong line. Also, the processor would only read the MCP every half-second making it imperative to verify the MCP entry on the FMA before moving on to other tasks. Even though both FMS's were made by Honeywell, the B757 FMS was less capable but more intuitive than the A320 FMS. FMS's have been greatly improved in later versions of both aircraft. Score one for the Boeing.

I personally preferred the conventional hydraulic steel brakes on the B757 to the brake-by-wire carbon brakes on the A320. I liked the feel and perceived effectiveness of the steel brakes better. Cockpit readouts of brake temperatures and brake fans for quick turns on the A320 were nice. Score a draw on brakes.

The IAE V2500 engines on the A320 configured for all-coach class(29 rows, 174 seats) weren't always up to the task for the passenger loads and stage lengths we flew. Had to make many bleeds/packs off takeoffs. Never had to do that in the B757 with either the RR or P&W engines. You can never have too much power. Score one for the Boeing.

The A320 was only certified to FL390 while the B757 was certified to FL420. That extra 3,000 feet was pretty useful when trying to stay out of the tops of Wx. Never any worries about the strength or lifting ability of the wing on the B757. Score one for the Boeing.

The fuselage diameter on the A320 family is 7.6 inches greater than on all the single-aisle Boeings. This allows each coach seat and the aisle to have an average of an inch extra width. There is more headroom and more room for overhead bins also. Score one for the Bus.

The A320 had vacuum lavs which were very noisy(hard to sleep in the back row on crew rest) and somewhat cantankerous but saved the weight of 5 gallons of blue water per lav. The B757 lavs hold 9 gallons of liquid each of which 5 gal. is fresh blue juice. Much quieter, heavier and often stinkier and always the possibility of a flush motor overheating. Vacuum lavs more suitable on a long-range aircraft ala B767 and B777. Score a draw on lavs.

The AFCS in the A320 family has very effective low speed/high AOA and high speed/low AOA protections regardless of whether or not an autopilot or A/THR(autothrust) is engaged. If you get too slow or too fast in the coffin corner of the flight envelope, the AFCS will add power up to TOGA and pitch down or reduce power to idle and pitch up to keep you in the envelope. Many pilots of aircraft w/o this feature have stalled or oversped in this flight regime. Score one for the Bus.

The A320 family FMS automatically calculates Vapp which is the Airbus equivalent of Boeing's Vref with headwind component speed adjustments. A major improvement is that it incorporates windshear protection by adjusting Vapp using a feature called GS Mini(minimum groundspeed.) The A/THR adds power to keep a minimum groundspeed in a strong headwind so as to not leave the aircraft in a low energy state with reduced power if the headwind suddenly goes away or shears to a tailwind as might happen when encountering a microburst close to the ground. Score one for the bus.

Finally, the aircraft climb performance is optimized and the pilot technique is simplified during windshear recovery and GPWS terrain avoidance escape maneuvers. In the Boeing you must pitch up to and nibble at the stickshaker while going to TOGA and retracting speedbrakes. In the Airbus you pull the stick back and hold it while the AFCS optimizes the AOA for best climb performance. Score one for the Bus.

Aesthetically, I don't think a better-looking airliner than the B757 was ever built, with the possible exception of the Lockheed L-1049 Super Connie. Score one for the Boeing.

 

[zonker]

Wow, great post 420. Very interesting read.