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I am designing a new GA aircraft that will enter service in 2028. I am looking for the FARS specifying the required minimum stall speed but different sources seem to say different things. On Cornell's Law school website, the Vstall is specified in 23.49. I found the same info on another site.

However, when I check eCFR, 23.49 doesn't exist. In fact, the regulations seem to end at 23.262. Were these other regulations amended or deleted? Which source should I use?

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    $\begingroup$ Part 23 has been completely rewritten; see this meta question for some related information $\endgroup$ – Pondlife Nov 13 '17 at 20:09
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On August 30, 2017, a completely new body of regulations for small aircraft has been put in place which does not distinguish between normal or utility airplanes but low speed (below 250 KTAS) and high speed designs (> 250 KTAS). It also distinguishes between four levels depending on the number of seats (0-1, 2-6, 7-9 and 10-19 passengers). The spirit of the new regulation is to no longer prescribe design-specific rules but more abstract goals in order to limit risk, leaving the details to the aircraft builder.

Also, the number of rules has been drastically cut, and their numbering starts where the old numbering ended. Therefore, 23.49 has become 23.2110 and no longer gives a specific stall speed. All it does is to direct the applicant to determine a stall speed and details what conditions must be covered.

I expect that you have not formally started the certification process of your design, because that date determines which regulations apply. You are now free to select the stall speed of your design as long as you can demonstrate that the aircraft can be operated safely without exceptional pilot skill or strength.

But you can always count on Eurocrats when a body of regulations which has grown like cancer is to be preserved and extended. In their version (CS-23), the maximum stall speed of 113 km/h or 61 knots is still alive and well. However, Amendment 5 has now copied the new body of regulations as well and replaces the old certification standard in the name of global harmonization.

The old regulations reflect the experience which has been collected over decades. Many rules can be traced back to a specific accident and it helps to read through them and to consider why this specific rule has been implemented. Your new design might employ a clever way to avoid that particular condition at all, and then the new liberty of the new regulations will be helpful. But it would be foolish to throw all that experience overboard - a lower stall speed makes any airplane easier to fly. When things happen less quickly and less kinetic energy is involved, more accidents can be avoided and the damage in those that still occur will be lower.

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Vs is dependent on the aircraft and is indicated on the air speed indicator of the aircraft you are flying. You will also find it in the flight envelope diagram.

FARs on the other hand are US regulations. They are organized into parts which do have versions, as you have already guessed.

Part 23 defines airworthiness standards to get an airplane type certified.

For single engine types, the stall speed is specified as less than 61 knots.

To complicate matters, even current aircraft may be certified to an older standard.

So if you want to know the Vs you have to tell us the plane type.

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  • $\begingroup$ Thanks for the response! The craft is a general aviation aircraft with an EIS of 2028. The Vs part is primarily just an example. I'm just confused on what regulations I should use to restrict the design. $\endgroup$ – Josh Fang Nov 13 '17 at 20:25

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