29.1505—Never-exceed speed.
(iii)
0.9 times the maximum speed substantiated for advancing blade tip mach number effects under critical altitude conditions.
(1)
No more than two of these variables (or no more than two instruments integrating more than one of these variables) are used at one time; and
(2)
The ranges of these variables (or of the indications on instruments integrating more than one of these variables) are large enough to allow an operationally practical and safe variation of VNE.
(c)
For helicopters, a stabilized power-off V
NE denoted as V
NE (power-off) may be established at a speed less than V
NE established pursuant to paragraph (a) of this section, if the following conditions are met:
(1)
V
NE (power-off) is not less than a speed midway between the power-on V
NE and the speed used in meeting the requirements of—
(ii)
§ 29.65(a) for Category B helicopters, except multi-engine helicopters meeting the requirements of § 29.67(b); and
(iii)
A constant airspeed for a portion of the altitude range for which certification is requested, and a constant amount less than power-on V
NE for the remainder of the altitude range.