Definition
The paragraph of Title 14 Code of Federal Regulations Part 23 that defines the conditions under which the minimum control speed with the critical engine inoperative (VMC) must be determined for small airplane certification. It specifies the configuration, power setting, center of gravity, weight, and bank angle requirements the manufacturer must use when establishing VMC for a multiengine airplane during type certification.
Plain English
It is the specific rule the FAA uses to tell aircraft makers exactly how to figure out the lowest speed at which a twin-engine airplane can still be controlled with one engine failed. The published VMC on the airspeed indicator (the red radial line) comes from this rule.
Context Anchor
Seen in discussions of VMC in multiengine training, especially when explaining why the published red-line speed is based on specific certification test conditions.
Derivation
In a regulation citation, “section” means a numbered part of a rule. “23” points to Part 23, which covers certification standards for certain airplanes; “149” is the specific rule number; and “(b)” points to paragraph b inside that rule.
Why Pilots Care
VMC is the speed below which loss of an engine can result in an uncontrollable yaw and roll; knowing the regulatory basis helps pilots understand why published VMC values exist and how they were determined.
Intuition Check
Do not read section 23.149(b) as a checklist step or an airplane manual section. Here it is a federal regulation citation, and the “(b)” points to one specific paragraph inside the rule.
Example Sentence 1
The published VMC in the airplane's flight manual was determined under the test conditions laid out in section 23.149(b).
Example Sentence 2
A pilot reviewing engine-out procedures may consult section 23.149(b) to understand the conditions under which the published VMC was established.