Originally Posted by
Oktas8
Ahem.
FAR 23.149 - MTOW is correct. For part 23 aircraft. Probably what n90bar and others are quoting.
Originally Posted by Part 23
§ 23.149 Minimum control speed.
(b) VMC for takeoff must not exceed 1.2 VS1, where VS1 is determined at the maximum takeoff weight. VMC must be determined with the most unfavorable weight and center of gravity position and with the airplane airborne and the ground effect negligible, for the takeoff configuration(s) with—
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Originally Posted by Part 25
§ 25.149 Minimum control speed
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(c) VMC may not exceed 1.13 VSR with—
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(4) The maximum sea level takeoff weight (or any lesser weight necessary to show VMC);
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Actually, Part 23 is better worded, because it avoids the nonsense wording about MTOW. The most unfavourable weight for VMC is the lightest weight, unless your weight /cg envelope is ridiculously skewed, such that the most aft cg is much further aft than the light weight case, and even in such a case you'd struggle to convinvce the regulators that anything except lightest weight and furthest aft in combination be tested.
Interesting that those data are for the E170. I note its for T/O-1 thrust, which I assume is a flex/derate setting. I seem to recall hearing that Embraer was using a variable rating system on the engines, such that they were adjusting the engine power for the conditions required, and then scheduling VMCs for THAT thrust.
So, technically, they are not scheduling VMC with weight. They're scheduling thrust with weight (probably to achieve a fixed or near-fixed level of performance, which means a roughly constant T/W) and then using the lower thrusts which naturally occur at lower weights to schedule VMC accordingly. That would explain why the values vary slightly up and down for the same OAT - it's not a perfect balance, sometimes the thrust reduction is big enough to outweigh the light weight effect, sometimes not.
Is there a corresponding table for the full rated thrust case, or is it a single value?
oops, sorry, I didnt look closely at the numbers, just the model, and assumed it was the same data. it's not.
scratches head