757

[TeeVee]

is it my imagination or does the 757 have ridiculous takeoff and climb capabilities?

[Moose135]

No, it's not just your imagination. It's something of a rocket ship.

[WILCO737]

is it my imagination or does the 757 have ridiculous takeoff and climb capabilities?

Yeah, ridiculously good The 757 is one of the best climb performer... Except the MD11 of course

wilco737

[TeeVee]

thanks. that's what i thought.

i knew there was a reason i liked the plane so much.

[mzk49o1]

[Simpleboy]

Any Airshow the RNZAF turns up to with one of their 757's is worth going to, you'll never see a commercial airliner be treated the way they treat theirs.

[TeeVee]

outstanding video...a bit hard to tell the real angle from behind but outstanding nonetheless.

[Gabriel]

Not only the angle, but the time it sustained it.

Any airplane (even an A340) can do an incredible climb trading speed for altitude, until it runs out of speed of course.

A better idea of the thrust-to-weight ratio can be obtained from how the plane climbs after a very slow flyby, when there is no speed to trade (just power). But still the planes at airshows are typically unrealistically light, achieving steady climb rates that you'll never see in commercial operations.

[TeeVee]

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?

[Gabriel]

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.

[TeeVee]

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."

[Gabriel]

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.

[MCM]

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.

[W7PSK]

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.

[Gabriel]

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?