Definition
A specific paragraph within Title 14 of the Code of Federal Regulations, Part 23, that establishes one of the conditions used when determining the minimum control speed (VMC) for a multi-engine airplane during certification. It limits the bank angle the manufacturer may use during VMC flight testing to no more than 5 degrees toward the operating engine.
Plain English
It is the federal rule that says, when testing a twin to find its minimum control speed, the airplane is allowed to be banked no more than 5 degrees toward the working engine. That bank limit is part of how the published VMC number is produced.
Context Anchor
Seen in discussions of how VMC is determined for multiengine airplanes, especially when the Airplane Flying Handbook explains the certification conditions behind the published VMC value.
Derivation
The number is a citation: Part 23 of the Federal Aviation Regulations covers small airplane certification, section 149 sets the rules for VMC, and paragraph (b)(5) is the specific item dealing with the 5-degree bank limit. Knowing the citation makes it easier to find the exact wording in the regulations.
Why Pilots Care
The published VMC in the airplane's manual was determined under this rule, including the 5-degree bank toward the live engine. If a pilot loses an engine and does not establish that small bank toward the operating engine, the airplane will actually lose directional control at a speed higher than the published VMC.
Intuition Check
Do not read “section” here as a physical part of the airplane. Here it means a numbered paragraph in a federal rule.
Example Sentence 1
The instructor explained that the VMC printed in the POH was established under section 23.149(b)(5), which assumes a 5-degree bank toward the operating engine.
Example Sentence 2
During training the instructor pointed to section 23.149(b)(5) to show where the FAA lists the exact test conditions for minimum control speed.