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716 

14 CFR Ch. I (1–1–19 Edition) 

§ 33.69 

T

ABLE

1—C

ONDITIONS

T

HAT

M

UST

B

E

D

EMONSTRATED BY AN

E

NGINE

T

EST

—Continued 

Condition 

Total air temperature 

Supercooled water 

concentrations 

(minimum) 

Median volume drop diameter 

Duration 

3. Glaze ice holding 

conditions.

(Turbojet, turbofan, 

and turboprop only).

Turbojet and Tur-

bofan, only: 10 to 
18 

°

F (

¥

12 to 

¥

°

C).

Alternating cycle: First 

1.7 g/m

3

(1 minute), 

Then 0.3 g/m

3

(6 

minute).

20 to 30 microns ...................

Must show repetitive, 

stabilized operation 
(or 45 minutes 
max). 

Turboprop, only: 2 to 

10 

°

F (

¥

17 to 

¥

12 

°

C).

.

4. Rime ice holding 

conditions.

(Turbojet, turbofan, 

and turboprop only).

Turbojet and Tur-

bofan, only: 

¥

10 to 

°

F (

¥

23 to 

¥

18 

°

C).

0.25 g/m

3

...................

20 to 30 microns ...................

Must show repetitive, 

stabilized operation 
(or 45 minutes 
max). 

Turboprop, only: 2 to 

10 

°

F (

¥

17 to 

¥

12 

°

C).

....................................

................................................

(d) Operate at ground idle speed for a 

minimum of 30 minutes at each of the 
following icing conditions shown in 
Table 2 of this section with the avail-
able air bleed for icing protection at its 
critical condition, without adverse ef-
fect, followed by acceleration to take-
off power or thrust. During the idle op-
eration, the engine may be run up peri-
odically to a moderate power or thrust 
setting in a manner acceptable to the 

Administrator. Analysis may be used 
to show ambient temperatures below 
the tested temperature are less crit-
ical. The applicant must document any 
demonstrated run ups and minimum 
ambient temperature capability in the 
engine operating manual as mandatory 
in icing conditions. The applicant must 
demonstrate, with consideration of ex-
pected airport elevations, the fol-
lowing: 

T

ABLE

2—D

EMONSTRATION

M

ETHODS FOR

S

PECIFIC

I

CING

C

ONDITIONS

 

Condition 

Total air temperature 

Supercooled water 

concentrations 

(minimum) 

Mean effective particle di-

ameter 

Demonstration 

1. Rime ice condition

0 to 15 

°

F (

¥

18 to 

¥

°

C).

Liquid—0.3 g/m

3

........

15–25 microns .......................

By engine test. 

2. Glaze ice condition 

20 to 30 

°

F (

¥

7 to 

¥

°

C).

Liquid—0.3 g/m

3

........

15–25 microns .......................

By engine test. 

3. Snow ice condition 

26 to 32 

°

F (

¥

3 to 0 

°

C).

Ice—0.9 g/m

3

............

100 microns ...........................
(minimum) ..............................

By test, analysis or 

combination of the 
two. 

4. Large drop glaze 

ice condition (Tur-
bojet, turbofan, and 
turboprop only).

15 to 30 

°

F (-9 to -1 

°

C).

Liquid—0.3 g/m

3

........

100 microns (minimum) .........

By test, analysis or 

combination of the 
two. 

(e) Demonstrate by test, analysis, or 

combination of the two, acceptable op-
eration for turbojet, turbofan, and tur-
boprop engines in mixed phase and ice 
crystal icing conditions throughout 
Appendix D of this part, icing envelope 
throughout its flight power range, in-
cluding minimum descent idling 
speeds. 

[Amdt. 33–34, 79 FR 66536, Nov. 4, 2014] 

§ 33.69

Ignitions system. 

Each engine must be equipped with 

an ignition system for starting the en-
gine on the ground and in flight. An 
electric ignition system must have at 
least two igniters and two separate sec-
ondary electric circuits, except that 
only one igniter is required for fuel 
burning augmentation systems. 

[Amdt. 33–6, 39 FR 35466, Oct. 1, 1974] 

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