Pt. 25, App. D

14 CFR Ch. I (1-1-19 Edition)

spaschal on DSK3GDR082PROD with CFR

Part II - Airframe Ice Accretions for Showing
Compliance With Subpart B.
(a) Ice accretions - General. The most critical ice accretion in terms of airplane performance and handling qualities for each
flight phase must be used to show compliance with the applicable airplane performance and handling requirements in icing conditions of subpart B of this part. Applicants
must demonstrate that the full range of atmospheric icing conditions specified in part I
of this appendix have been considered, including the mean effective drop diameter,
liquid water content, and temperature appropriate to the flight conditions (for example,
configuration, speed, angle-of-attack, and altitude). The ice accretions for each flight
phase are defined as follows:
(1) Takeoff ice is the most critical ice accretion on unprotected surfaces and any ice accretion on the protected surfaces appropriate
to normal ice protection system operation,
occurring between the end of the takeoff distance and 400 feet above the takeoff surface,
assuming accretion starts at the end of the
takeoff distance in the takeoff maximum
icing conditions defined in part I of this Appendix.
(2) Final takeoff ice is the most critical ice
accretion on unprotected surfaces, and any
ice accretion on the protected surfaces appropriate to normal ice protection system
operation, between 400 feet and either 1,500
feet above the takeoff surface, or the height
at which the transition from the takeoff to
the en route configuration is completed and
VFTO is reached, whichever is higher. Ice accretion is assumed to start at the end of the
takeoff distance in the takeoff maximum
icing conditions of part I, paragraph (c) of
this Appendix.
(3) En route ice is the critical ice accretion
on the unprotected surfaces, and any ice accretion on the protected surfaces appropriate
to normal ice protection system operation,
during the en route phase.
(4) Holding ice is the critical ice accretion
on the unprotected surfaces, and any ice accretion on the protected surfaces appropriate
to normal ice protection system operation,
during the holding flight phase.
(5) Approach ice is the critical ice accretion
on the unprotected surfaces, and any ice accretion on the protected surfaces appropriate
to normal ice protection system operation
following exit from the holding flight phase
and transition to the most critical approach
configuration.
(6) Landing ice is the critical ice accretion
on the unprotected surfaces, and any ice accretion on the protected surfaces appropriate
to normal ice protection system operation
following exit from the approach flight phase
and transition to the final landing configuration.

(b) In order to reduce the number of ice accretions to be considered when demonstrating compliance with the requirements of Section 25.21(g), any of the ice accretions
defined in paragraph (a) of this section may
be used for any other flight phase if it is
shown to be more critical than the specific
ice accretion defined for that flight phase.
Configuration differences and their effects
on ice accretions must be taken into account.
(c) The ice accretion that has the most adverse effect on handling qualities may be
used for airplane performance tests provided
any difference in performance is conservatively taken into account.
(d) For both unprotected and protected
parts, the ice accretion for the takeoff phase
may be determined by calculation, assuming
the takeoff maximum icing conditions defined in appendix C, and assuming that:
(1) Airfoils, control surfaces and, if applicable, propellers are free from frost, snow, or
ice at the start of the takeoff;
(2) The ice accretion starts at the end of
the takeoff distance.
(3) The critical ratio of thrust/power-toweight;
(4) Failure of the critical engine occurs at
VEF; and
(5) Crew activation of the ice protection
system is in accordance with a normal operating procedure provided in the Airplane
Flight Manual, except that after beginning
the takeoff roll, it must be assumed that the
crew takes no action to activate the ice protection system until the airplane is at least
400 feet above the takeoff surface.
(e) The ice accretion before the ice protection system has been activated and is performing its intended function is the critical
ice accretion formed on the unprotected and
normally protected surfaces before activation and effective operation of the ice protection system in continuous maximum atmospheric icing conditions. This ice accretion only applies in showing compliance to
SectionSection 25.143(j) and 25.207(h), and 25.207(i).
[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as
amended by Amdt. 25-121, 72 FR 44669, Aug. 8,
2007; 72 FR 50467, Aug. 31, 2007; Amdt. 25-129,
74 FR 38340, Aug. 3, 2009; Amdt. 25-140, 79 FR
65528, Nov. 4, 2014]

APPENDIX D TO PART 25
Criteria for determining minimum flight crew.
The following are considered by the Agency
in determining the minimum flight crew
under Section 25.1523:
(a) Basic workload functions. The following
basic workload functions are considered:
(1) Flight path control.
(2) Collision avoidance.
(3) Navigation.
(4) Communications.

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