727
Federal Aviation Administration, DOT
§ 33.83
(2) Continuation of the rain ingestion
during subsequent rapid deceleration
to minimum idle, then
(3) Continuation of the rain ingestion
during three minutes at minimum idle
power to be certified for flight oper-
ation, then
(4) Continuation of the rain ingestion
during subsequent rapid acceleration
to takeoff power.
(c)
Engines for supersonic airplanes. In
addition to complying with paragraphs
(a)(1) and (a)(2) of this section, a sepa-
rate test for supersonic airplane en-
gines only, shall be conducted with
three hailstones ingested at supersonic
cruise velocity. These hailstones shall
be aimed at the engine’s critical face
area, and their ingestion must not
cause unacceptable mechanical damage
or unacceptable power or thrust loss
after the ingestion or require the en-
gine to be shut down. The size of these
hailstones shall be determined from
the linear variation in diameter from 1-
inch (25 millimeters) at 35,000 feet
(10,500 meters) to
1
⁄
4
-inch (6 millime-
ters) at 60,000 feet (18,000 meters) using
the diameter corresponding to the low-
est expected supersonic cruise altitude.
Alternatively, three larger hailstones
may be ingested at subsonic velocities
such that the kinetic energy of these
larger hailstones is equivalent to the
applicable supersonic ingestion condi-
tions.
(d) For an engine that incorporates
or requires the use of a protection de-
vice, demonstration of the rain and
hail ingestion capabilities of the en-
gine, as required in paragraphs (a), (b),
and (c) of this section, may be waived
wholly or in part by the Administrator
if the applicant shows that:
(1) The subject rain and hail con-
stituents are of a size that will not
pass through the protection device;
(2) The protection device will with-
stand the impact of the subject rain
and hail constituents; and
(3) The subject of rain and hail con-
stituents, stopped by the protection de-
vice, will not obstruct the flow of in-
duction air into the engine, resulting
in damage, power or thrust loss, or
other adverse engine anomalies in ex-
cess of what would be accepted in para-
graphs (a), (b), and (c) of this section.
[Doc. No. 28652, 63 FR 14799, Mar. 26, 1998]
§ 33.79
Fuel burning thrust augmentor.
Each fuel burning thrust augmentor,
including the nozzle, must—
(a) Provide cutoff of the fuel burning
thrust augmentor;
(b) Permit on-off cycling;
(c) Be controllable within the in-
tended range of operation;
(d) Upon a failure or malfunction of
augmentor combustion, not cause the
engine to lose thrust other than that
provided by the augmentor; and
(e) Have controls that function com-
patibly with the other engine controls
and automatically shut off augmentor
fuel flow if the engine rotor speed drops
below the minimum rotational speed at
which the augmentor is intended to
function.
[Amdt. 33–6, 39 FR 35468, Oct. 1, 1974]
Subpart F—Block Tests; Turbine
Aircraft Engines
§ 33.81
Applicability.
This subpart prescribes the block
tests and inspections for turbine en-
gines.
[Doc. No. 3025, 29 FR 7453, June 10, 1964, as
amended by Amdt. 33–6, 39 FR 35468, Oct. 1,
1974]
§ 33.82
General.
Before each endurance test required
by this subpart, the adjustment setting
and functioning characteristic of each
component having an adjustment set-
ting and a functioning characteristic
that can be established independent of
installation on the engine must be es-
tablished and recorded.
[Amdt. 36–6, 39 FR 35468, Oct. 1, 1974]
§ 33.83
Vibration test.
(a) Each engine must undergo vibra-
tion surveys to establish that the vi-
bration characteristics of those compo-
nents that may be subject to mechani-
cally or aerodynamically induced vi-
bratory excitations are acceptable
throughout the declared flight enve-
lope. The engine surveys shall be based
upon an appropriate combination of ex-
perience, analysis, and component test
and shall address, as a minimum,
blades, vanes, rotor discs, spacers, and
rotor shafts.
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14 CFR Ch. I (1–1–24 Edition)
§ 33.84
(b) The surveys shall cover the
ranges of power or thrust, and both the
physical and corrected rotational
speeds for each rotor system, cor-
responding to operations throughout
the range of ambient conditions in the
declared flight envelope, from the min-
imum rotational speed up to 103 per-
cent of the maximum physical and cor-
rected rotational speed permitted for
rating periods of two minutes or
longer, and up to 100 percent of all
other permitted physical and corrected
rotational speeds, including those that
are overspeeds. If there is any indica-
tion of a stress peak arising at the
highest of those required physical or
corrected rotational speeds, the sur-
veys shall be extended sufficiently to
reveal the maximum stress values
present, except that the extension need
not cover more than a further 2 per-
centage points increase beyond those
speeds.
(c) Evaluations shall be made of the
following:
(1) The effects on vibration charac-
teristics of operating with scheduled
changes (including tolerances) to vari-
able vane angles, compressor bleeds,
accessory loading, the most adverse
inlet air flow distortion pattern de-
clared by the manufacturer, and the
most adverse conditions in the exhaust
duct(s); and
(2) The aerodynamic and
aeromechanical factors which might
induce or influence flutter in those sys-
tems susceptible to that form of vibra-
tion.
(d) Except as provided by paragraph
(e) of this section, the vibration
stresses associated with the vibration
characteristics determined under this
section, when combined with the ap-
propriate steady stresses, must be less
than the endurance limits of the mate-
rials concerned, after making due al-
lowances for operating conditions for
the permitted variations in properties
of the materials. The suitability of
these stress margins must be justified
for each part evaluated. If it is deter-
mined that certain operating condi-
tions, or ranges, need to be limited, op-
erating and installation limitations
shall be established.
(e) The effects on vibration charac-
teristics of excitation forces caused by
fault conditions (such as, but not lim-
ited to, out-of balance, local blockage
or enlargement of stator vane passages,
fuel nozzle blockage, incorrectly sched-
ule compressor variables, etc.) shall be
evaluated by test or analysis, or by ref-
erence to previous experience and shall
be shown not to create a hazardous
condition.
(f) Compliance with this section shall
be substantiated for each specific in-
stallation configuration that can affect
the vibration characteristics of the en-
gine. If these vibration effects cannot
be fully investigated during engine cer-
tification, the methods by which they
can be evaluated and methods by which
compliance can be shown shall be sub-
stantiated and defined in the installa-
tion instructions required by § 33.5.
[Doc. No. 28107, 61 FR 28433, June 4, 1996, as
amended by Amdt. 33–33, 77 FR 39624, July 5,
2012; 77 FR 58301, Sept. 20, 2012]
§ 33.84
Engine overtorque test.
(a) If approval of a maximum engine
overtorque is sought for an engine in-
corporating a free power turbine, com-
pliance with this section must be dem-
onstrated by testing.
(1) The test may be run as part of the
endurance test requirement of § 33.87.
Alternatively, tests may be performed
on a complete engine or equivalent
testing on individual groups of compo-
nents.
(2) Upon conclusion of tests con-
ducted to show compliance with this
section, each engine part or individual
groups of components must meet the
requirements of § 33.93(a)(1) and (a)(2).
(b) The test conditions must be as
follows:
(1) A total of 15 minutes run at the
maximum engine overtorque to be ap-
proved. This may be done in separate
runs, each being of at least 2
1
⁄
2
minutes
duration.
(2) A power turbine rotational speed
equal to the highest speed at which the
maximum overtorque can occur in
service. The test speed may not be
more than the limit speed of take-off
or OEI ratings longer than 2 minutes.
(3) For engines incorporating a reduc-
tion gearbox, a gearbox oil tempera-
ture equal to the maximum tempera-
ture when the maximum engine over-
torque could occur in service; and for
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