Section 33.78

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

(2) Require the engine to be shutdown.
(d) For an engine that incorporates a
protection device, compliance with this
section need not be demonstrated with
respect to ice formed forward of the
protection device if it is shown that - 
(1) Such ice is of a size that will not
pass through the protective device;
(2) The protective device will withstand the impact of the ice; and
(3) The ice stopped by the protective
device will not obstruct the flow of induction air into the engine with a resultant sustained reduction in power or
thrust greater than those values defined by paragraph (c) of this section.
(e) Compliance with the requirements of this section must be dem-

onstrated by engine ice ingestion test
under the following ingestion conditions or by validated analysis showing
equivalence of other means for demonstrating soft body damage tolerance.
(1) The minimum ice quantity and dimensions will be established by the engine size as defined in Table 1 of this
section.
(2) The ingested ice dimensions are
determined by linear interpolation between table values, and are based on
the actual engine-s inlet hilite area.
(3) The ingestion velocity will simulate ice from the inlet being sucked
into the engine.
(4) Engine operation will be at the
maximum cruise power or thrust unless lower power is more critical.

TABLE 1 - MINIMUM ICE SLAB DIMENSIONS BASED ON ENGINE INLET SIZE
Engine Inlet Hilite area
(sq. inch)

Thickness
(inch)

0 .......................................................................................................................
80 .....................................................................................................................
300 ...................................................................................................................
700 ...................................................................................................................
2800 .................................................................................................................
5000 .................................................................................................................
7000 .................................................................................................................
7900 .................................................................................................................
9500 .................................................................................................................
11300 ...............................................................................................................
13300 ...............................................................................................................
16500 ...............................................................................................................
20000 ...............................................................................................................

[Doc. No. 16919, 49 FR 6852, Feb. 23, 1984, as
amended by Amdt. 33-19, 63 FR 14798, Mar. 26,
1998; 63 FR 53278, Oct. 5, 1998; Amdt. 33-20, 65
FR 55856, Sept. 14, 2000; Amdt. 33-34, 79 FR
65537, Nov. 4, 2014]

spaschal on DSK3GDR082PROD with CFR

Section 33.78

Rain and hail ingestion.

(a) All engines. (1) The ingestion of
large hailstones (0.8 to 0.9 specific gravity) at the maximum true air speed, up
to 15,000 feet (4,500 meters), associated
with a representative aircraft operating in rough air, with the engine at
maximum continuous power, may not
cause unacceptable mechanical damage
or unacceptable power or thrust loss
after the ingestion, or require the engine to be shut down. One-half the
number of hailstones shall be aimed
randomly over the inlet face area and
the other half aimed at the critical
inlet face area. The hailstones shall be
ingested in a rapid sequence to simu-

Width
(inch)

0.25
0.25
0.25
0.25
0.35
0.43
0.50
0.50
0.50
0.50
0.50
0.5
0.5

Length
(inch)
0
6
12
12
12
12
12
12
12
12
12
12
12

late a hailstone encounter and the
number and size of the hailstones shall
be determined as follows:
(i) One 1-inch (25 millimeters) diameter hailstone for engines with inlet
areas of not more than 100 square
inches (0.0645 square meters).
(ii) One 1-inch (25 millimeters) diameter and one 2-inch (50 millimeters)
diameter hailstone for each 150 square
inches (0.0968 square meters) of inlet
area, or fraction thereof, for engines
with inlet areas of more than 100
square inches (0.0645 square meters).
(2) In addition to complying with
paragraph (a)(1) of this section and except as provided in paragraph (b) of
this section, it must be shown that
each engine is capable of acceptable operation throughout its specified operating envelope when subjected to sudden encounters with the certification
standard concentrations of rain and

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