If I used 0.77 to climb up there and then accelerated to 0.79 I would be 400ft above where one of those limits kicked in. Which limit am I not complying with? Who knows
Finally!
I know: you would be maneuver margin limited, but by the high speed band. I actually did exactly what you did to comfort my FO that we had plenty of margin (some are worried, because other captains tells them they alway need 600 feet or more to climb, I try to tell them exactly what we have been discussing now for 109 posts). I selected cost index back to 4 and the FMC showed 376 as max. With 55 it was the 373, that is show in the pictures (actually 372 before the climb). The highest max you get with ECON cost index 0. Had I put in .81 as speed, it would probably have shown max as 350ish. So now: Do you still think I was thrust limited?
Am I cheating? I quote myself from post 54:
Every decision I make in the cockpit is a conscious, considered decision, based on the facts at hand... Not an automated decision based on old wife's tales or "that I always do/need so".
The FMC is just a stupid computer. It has no idea what you are really going to do. Garbage in = garbage out. That's why I object to people saying "I always want +600/800/1000 feet to max altitude. If I have a 10 knots window between the lower and upper amber band I am happy, because it is more than enough to absorb natural wind variations in smooth air (flying at the top of the window and including the amber high speed band, since this is not really a problem to use this range to absorb speed variations too).
I really don't care what the FMC is telling me max altitude is,
that is my point!
So how do I know if I have 10 knot or not? Simple, use the FMC as a tool instead of being tooled by the FMC:
Hit ALT HOLD, put in desired level in the FMC and execute. Put in 200 knots. FMC now tells you e.g. MIN SPEED 242 KNOTS. Put in 300 knots. FMC now tells you e.g. MAX SPEED 256 KNOTS. So in this example I know the range between low and high speed buffet margin (with 40 degs bank) is 14 knots, completely independent from what I will actually select as cruise speed when I get to that level.
If the margin is around 10 knots or more and it is desirable to climb, I climb
If you were to fly an old machine with conventional instruments and no speed tape, would you be comfortable climbing if I told you your stall speed was 200 knots, your MMO was 270 and you would have enough thrust to keep you flying? Probably...
I maintain that at 240kts it would have been less than the 15 degrees required.
The holding speed is calculated that you are actually able to do turns in the holding. So I don't think so. Even in the unlikely event that you are in a turn at the very same time that the wind is changing (which would maybe exceed you thrust available, depending on the strength of the sheer), nothing prevents you from hitting HDG SEL, level the wings and accelerate back to acceptable speed before completing the turn. Remember we agreed already that we have no intentions flying at this speed, because it is ineffective - so when I started the turn I would have had .76-.79, if the speed starts to drop back, and keeps dropping even with MCT, there is still the option of delaying the turn.
This is again what I mean, there are so many things you can do, and so many margins on margins that adding your own ones on top makes no sense, when it is not justified. I quote myself from post 68:
I have no problem adding margins to margins, when it is justified. I happily bring 2 tons extra fuel if there is a reason to do so. But I also fly with min required if there is no reason to bring extra. What I do not agree with is people saying "I don't fly with less than 800 kg extra", "I always want to see +800 feet on the max altitude before I climb" etc. I have only a big WHY? to say to that.
If I have, or expect, turbulence I might want to see a 20+ knots window between the low and upper amber band.
And like latetonite, I select CON when I need to. And I do so
routinely due to the way I operate the aircraft (de facto's objection against
routinely, was what got me involved in this thread, although it is completely in line with the recommendations from Boeing). In fact, I
always select CON with a <15 knots window.
And that was this topic all about.