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  • TeeVee
    replied
    http://www.boeing.com/commercial/airports/757.htm
    http://www.rcoco.com/sdoc/

    Leave a comment:


  • Juulke
    replied
    Originally posted by TeeVee View Post
    Gabe, you're such a kill-joy! I'm sure you are correct though...informative as always.

    So, today, i was onboard AA# 599 (LGA-MIA), it was absolutely a gorgeous day in mia, perfect for flying and landing. For some unknown reason, we missed the approach and flew around for a second try. Interestingly, as loud as the 757's engines are, the increase in power at go around was barely perceptible, it was as if the pilot barely advanced the throttles. heck, gear up was more noticeable.

    since i'm not a techie and dont understand boeing's technical manuals on their website, is it just that the 757 has a really good power to weight ratio, better than most other aircraft?
    can you post a link of the manuals? or send me a link?

    Leave a comment:


  • W7PSK
    replied
    Originally posted by Gabriel View Post
    Well, this answers one of the questions I was about to ask: How does the airplane "knows" if you want a smooth go-around or if you want to escape from a windshear or a CFIT.
    The Throttle is what I know, It reacts to various flap, gear, Altitude Settings depending on Mode you are in. There are set procedures in the FCOM for Wind shear.

    The airplane also has a lot of sensors and black boxes that work together to give the pilot and the aircraft vital information on Location, speeds, altitudes. Most are double and triple backed up to give a required 10 to the minus 9th error margin.

    Leave a comment:


  • W7PSK
    replied
    Originally posted by AJ View Post
    Just a major adjustment, 2000 FPS is 120,000 feet per minute!

    MCM is correct, first press gives you 2000 feet per minute.

    Cheers.
    Mistyped, meant 2000FPM

    Leave a comment:


  • Moose135
    replied
    Originally posted by AJ View Post
    Just a major adjustment, 2000 FPS is 120,000 feet per minute!
    Well, it is something of a rocket ship...

    Leave a comment:


  • TeeVee
    replied
    i do appreciate the answers folks. thank you for taking the time. i now understand if i am correct, that a missed approach does not necessarily need full TOGA thrust or max thrust.

    so is the "mystique" of the 757's takeoff/climb ability busted? or does it have some calculable advantage over other aircraft?

    Leave a comment:


  • Gabriel
    replied
    AJ, I'm sure that the 2000fps vs 2000fpm was a mistyping and not the intent of the "minor adjustment", which seems to have been adding the first press vs second press cases that were missing in MCM's explanation.

    Leave a comment:


  • AJ
    replied
    Originally posted by W7PSK View Post
    Just a minor adjustment.

    The first press of G/A will give you a 2000 FPS climb

    the second will give you full rated power.
    Just a major adjustment, 2000 FPS is 120,000 feet per minute!

    MCM is correct, first press gives you 2000 feet per minute.

    Cheers.

    Leave a comment:


  • Gabriel
    replied
    The first press of G/A will give you a 2000 FPS climb, the second will give you full rated power.
    Well, this answers one of the questions I was about to ask: How does the airplane "knows" if you want a smooth go-around or if you want to escape from a windshear or a CFIT.

    The other question is, since the go-around can happen with the airplane at any weight (from almost empty to almost MTOW), and it's not nearly a steady meneuver (at lest in the first several seconds, where you might be pulling up and retracting flaps while loosing speed and the engines are just starting to spool-up), how does the airplane "knows" how much to advance the throttles for the 2000fpm climb?

    Leave a comment:


  • W7PSK
    replied
    Originally posted by MCM View Post
    When you select GA on the autothrottle it does not drive to max (or takeoff) thrust, it simply gives you the required thrust to achieve a 2000fpm rate of climb.

    This thrust is usually less than required for takeoff, and is far less than max thrust. For this reason, even a low level go around on a 757/767 will seem to have a relatively low thrust level compared to takeoff... although it will be a definate increase.

    As Gabriel has said, if the G/A was done from high altitude they may have done it with a lower thrust advance as well.
    Just a minor adjustment.

    The first press of G/A will give you a 2000 FPS climb

    the second will give you full rated power.

    Leave a comment:


  • MCM
    replied
    When you select GA on the autothrottle it does not drive to max (or takeoff) thrust, it simply gives you the required thrust to achieve a 2000fpm rate of climb.

    This thrust is usually less than required for takeoff, and is far less than max thrust. For this reason, even a low level go around on a 757/767 will seem to have a relatively low thrust level compared to takeoff... although it will be a definate increase.

    As Gabriel has said, if the G/A was done from high altitude they may have done it with a lower thrust advance as well.

    Leave a comment:


  • Gabriel
    replied
    Well, IF the engines' noise was much lower than during take-off, then the engines were simply not at take-off thrust. So we might use this missing aproach to judge the pilot's technique but not to judge the "powerfulness" of the 757.

    Leave a comment:


  • TeeVee
    replied
    you're welcome!!

    barely perceptible from an audio perspective. at takeoff and climb, the 757 is normally quite loud, not to mention that special resonance. during the missed approach you could hear the engines spool up a bit but just barely.

    i was in an aisle seat so it was difficult to judge our altitude with any accuracy, but based on the buildings we were passing, i would guess no lower than 100 feet.

    all in all, it was a very smooth, uneventful "missed approach."

    Leave a comment:


  • Gabriel
    replied
    Originally posted by TeeVee View Post
    Gabe, you're such a kill-joy! I'm sure you are correct though...informative as always.
    Thanks, I guess

    Interestingly, as loud as the 757's engines are, the increase in power at go around was barely perceptible, it was as if the pilot barely advanced the throttles.
    How do you judge the "increase in power". I mean, what parameters, sensations, etc. do you use to say it was barely perceptible.

    While I wait for your answer, I'll tell you three things that cross my mind:

    1) Thrust to weight is pretty good in all twinjets, due to the requirement to achieve a certain take-off/climb performance with just half of the normal thrust (that is, with one engine failed).

    2) From a "sensations" point of view, there are things that are difficult to tell.
    a) One is "increase of power" vs "rate of increase of power". Smoothly advancing the throttles to max along several seconds will eventually lead to the same thrust than slamming the throttles against the forward stops. The later however will be felt much more violent (because it is!)
    b) Another one is deck angle vs acceleration. Both are felt like being pushed against your seat-back. Interestingly, when the thrust exceeds by a given amount what is needed to fly straight and level that push force you feel is the same regardless of whether the excess thrust is used to climb at constant speed (deck angle) or to speed-up at constant altitude (acceleration), or a combination of both. Next time you fly do the following experiment. Hold a yarn or a lace hanging from your hand. When the airplane accelerates down the runway the yarn will hang at an angle about the floor (not perpendicular) due to that push force. During the rotation, lift off and climb that angle remains the same.
    During the final approach (which happens at constant speed and an almost level deck angle) your feeling against the seat-back is neutral. Once established in the go-around that feeling should be about that of a take-off, unless...

    3) Was it a low go-around or a high one? While "the book" calls for TOGA thrust NOW & nose way up (designed to minimize altitude loss after the decision), the pilot might do a smoother maneuver if altitude is not of concern.

    Leave a comment:


  • TeeVee
    replied
    Gabe, you're such a kill-joy! I'm sure you are correct though...informative as always.

    So, today, i was onboard AA# 599 (LGA-MIA), it was absolutely a gorgeous day in mia, perfect for flying and landing. For some unknown reason, we missed the approach and flew around for a second try. Interestingly, as loud as the 757's engines are, the increase in power at go around was barely perceptible, it was as if the pilot barely advanced the throttles. heck, gear up was more noticeable.

    since i'm not a techie and dont understand boeing's technical manuals on their website, is it just that the 757 has a really good power to weight ratio, better than most other aircraft?

    Leave a comment:

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