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The article "Boeing’s MCAS on the 737 Max may not have been needed at all" (The Air Current, January 10, 2021) quotes a Boeing e-mail about the 737 MAX that says (emphasis mine),

I can't comment on last time either stalled an NG.

Flaps up engineering data for straight, turning, idle & FAR power show the MAX worse than the NG in two areas ...
Greater pitchup ("harder" than the NG)
Less stickforce per g

The shape of the pitching moment curve as the airplane approaches stall is similar to NG. However the MAX extends to higher alpha, and when it does stall, it breaks more abruptly (pitchup) than NG. This effectively makes the pilots push on column, reducing forces, and resulting in an Elevator Feel Shift than [that? —cjs] is ineffective. Meaning the stick forces are light to none, resulting in unacceptable stall id.

What is "FAR power" in this context?

cjs
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2 Answers2

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From the context of MCAS, they're talking about stalls. So we can infer they're talking about 14 CFR § 25.201(a) (FAR Part 25.201), stall demonstrations on transport category aircraft, which states

(a) Stalls must be shown in straight flight and in 30 degree banked turns with -

(1) Power off; and

(2) The power necessary to maintain level flight at 1.5 VSR1 (where VSR1 corresponds to the reference stall speed at maximum landing weight with flaps in the approach position and the landing gear retracted).

We can conclude the e-mail's "straight and turning" refers to straight flight and 30 degree banked turns, while "idle and FAR power" refers to condition (1) and (2), respectively.

user71659
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  • Ah! That the context is stall behaviour is rather more clear with more of the e-mail body; I've since added that to the question. Thanks. – cjs Aug 25 '22 at 06:48
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It's not a term used in operating the 737, but since since "FAR" is the abbreviation typically (is slightly anachronistically) used for the "Federal Aviation Regulations" (which are now formally Code of Federal Regulations, or CFR part xxx), I'd suspect it refers to a power level specified in the certification regulations. If that suspicion is correct, you could replace "FAR" in the sentence with "specified" and get the author's meaning.

Ralph J
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    I'm guessing that "FAR" in the author's context means "full aircraft rating" or something similar... – Ron Beyer Aug 22 '22 at 14:31
  • Technically "FAR" is the Federal Acquisition Regulations, 48 CFR. The FAA doesn't have the authority to call 14 CFR "FAR." Mostly they don't, but it it does slip in to some official publications... – randomhead Aug 22 '22 at 15:49
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    @randomhead While I won't dispute that your point is correct, I stand by my answer. The OP's post says the text came from a Boeing email, and its tone isn't particularly official... sounds like somebody summarizing results for a manager. Among pilots, "the FAR's" are the Federal Aviation Regulations, even though that isn't technically what they're called. If you ask 100 pilots "what are the FAR's?" then you're likely to get that answer back 99 or 100 times. The acquisition regulations aren't what's used to certify aircraft, so those aren't what would be specifying a power setting. – Ralph J Aug 22 '22 at 22:23
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    @RonBeyer That'd be a reasonable guess, but I've never heard of that term. After all, power comes from engines rather than the aircraft. There are lots of ways that a particular thrust level could be described; in this context I think it's more likely that they're using "FAR power" to mean "the power setting specified in the FAR part XX" (whichever part they're certifying under at that time) than that this is a new way of describing full thrust or whatever thrust level apart from the regulatory requirements. – Ralph J Aug 22 '22 at 22:29
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    @randomhead I am no expert, but I would say that Ralph J is correct in his assessment that the e-mail message is fairly informally written. This seems pretty clear if you follow my my link in the question and read the whole message. The same is true of the the other e-mail messages in that thread that are also quoted there. – cjs Aug 23 '22 at 15:19