694
14 CFR Ch. I (1–1–24 Edition)
§ 31.43
§ 31.43
Fitting factor.
(a) A fitting factor of at least 1.15
must be used in the analysis of each
fitting the strength of which is not
proven by limit and ultimate load tests
in which the actual stress conditions
are simulated in the fitting and sur-
rounding structure. This factor applies
to all parts of the fitting, the means of
attachment, and the bearing on the
members joined.
(b) Each part with an integral fitting
must be treated as a fitting up to the
point where the section properties be-
come typical of the member.
(c) The fitting factor need not be
used if the joint design is made in ac-
cordance with approved practices and
is based on comprehensive test data.
§ 31.45
Fuel cells.
If fuel cells are used, the fuel cells,
their attachments, and related sup-
porting structure must be shown by
tests to be capable of withstanding,
without detrimental distortion or fail-
ure, any inertia loads to which the in-
stallation may be subjected, including
the drop tests prescribed in § 31.27(c). In
the tests, the fuel cells must be loaded
to the weight and pressure equivalent
to the full fuel quantity condition.
[Amdt. 31–3, 41 FR 55474, Dec. 20, 1976]
§ 31.46
Pressurized fuel systems.
For pressurized fuel systems, each
element and its connecting fittings and
lines must be tested to an ultimate
pressure of at least twice the maximum
pressure to which the system will be
subjected in normal operation. No part
of the system may fail or malfunction
during the test. The test configuration
must be representative of the normal
fuel system installation and balloon
configuration.
[Amdt. 31–3, 41 FR 55474, Dec. 20, 1976]
§ 31.47
Burners.
(a) If a burner is used to provide the
lifting means, the system must be de-
signed and installed so as not to create
a fire hazard.
(b) There must be shielding to pro-
tect parts adjacent to the burner
flame, and the occupants, from heat ef-
fects.
(c) There must be controls, instru-
ments, or other equipment essential to
the safe control and operation of the
heater. They must be shown to be able
to perform their intended functions
during normal and emergency oper-
ation.
(d) The burner system (including the
burner unit, controls, fuel lines, fuel
cells, regulators, control valves, and
other related elements) must be sub-
stantiated by an endurance test of at
least 40 hours. Each element of the sys-
tem must be installed and tested to
simulate actual balloon installation
and use.
(1) The test program for the main
blast valve operation of the burner
must include:
(i) Five hours at the maximum fuel
pressure for which approval is sought,
with a burn time for each one minute
cycle of three to ten seconds. The burn
time must be established so that each
burner is subjected to the maximum
thermal shock for temperature affected
elements;
(ii) Seven and one-half hours at an
intermediate fuel pressure, with a burn
time for each one minute cycle of three
to ten seconds. An intermediate fuel
pressure is 40 to 60 percent of the range
between the maximum fuel pressure
referenced in paragraph (d)(1)(i) of this
section and minimum fuel pressure ref-
erenced in paragraph (d)(1)(iii);
(iii) Six hours and fifteen minutes at
the minimum fuel pressure for which
approval is sought, with a burn time
for each one minute cycle of three to
ten seconds;
(iv) Fifteen minutes of operation on
vapor, with a burn time for each one
minute cycle of at least 30 seconds; and
(v) Fifteen hours of normal flight op-
eration.
(2) The test program for the sec-
ondary or backup operation of the
burner must include six hours of oper-
ation with a burn time for each five
minute cycle of one minute at an inter-
mediate fuel pressure.
(e) The test must also include at
least three flameouts and restarts.
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§ 31.61
(f) Each element of the system must
be serviceable at the end of the test.
[Doc. No. 1437, 29 FR 8258, July 1, 1964, as
amended by Amdt. 31–2, 30 FR 3377, Mar. 13,
1965; Amdt. 31–7, 61 FR 18223, Apr. 24, 1996; 61
FR 20877, May 8, 1996]
§ 31.49
Control systems.
(a) Each control must operate easily,
smoothly, and positively enough to
allow proper performance of its func-
tions. Controls must be arranged and
identified to provide for convenience of
operation and to prevent the possi-
bility of confusion and subsequent in-
advertent operation.
(b) Each control system and oper-
ating device must be designed and in-
stalled in a manner that will prevent
jamming, chafing, or interference from
passengers, cargo, or loose objects. Pre-
caution must be taken to prevent for-
eign objects from jamming the con-
trols. The elements of the control sys-
tem must have design features or must
be distinctly and permanently marked
to minimize the possibility of incorrect
assembly that could result in malfunc-
tioning of the control system.
(c) Each balloon using a captive gas
as the lifting means must have an
automatic valve or appendix that is
able to release gas automatically at
the rate of at least three percent of the
total volume per minute when the bal-
loon is at its maximum operating pres-
sure.
(d) Each hot air balloon must have a
means to allow the controlled release
of hot air during flight.
(e) Each hot air balloon must have a
means to indicate the maximum enve-
lope skin temperatures occurring dur-
ing operation. The indicator must be
readily visible to the pilot and marked
to indicate the limiting safe tempera-
ture of the envelope material. If the
markings are on the cover glass of the
instrument, there must be provisions
to maintain the correct alignment of
the glass cover with the face of the
dial.
[Doc. No. 1437, 29 FR 8258, July 1, 1964, as
amended by Amdt. 31–2, 30 FR 3377, Mar. 13,
1965]
§ 31.51
Ballast.
Each captive gas balloon must have a
means for the safe storage and con-
trolled release of ballast. The ballast
must consist of material that, if re-
leased during flight, is not hazardous
to persons on the ground.
§ 31.53
Drag rope.
If a drag rope is used, the end that is
released overboard must be stiffened to
preclude the probability of the rope be-
coming entangled with trees, wires, or
other objects on the ground.
§ 31.55
Deflation means.
There must be a means to allow
emergency deflation of the envelope so
as to allow a safe emergency landing. If
a system other than a manual system
is used, the reliability of the system
used must be substantiated.
[Amdt. 31–2, 30 FR 3377, Mar. 13, 1965]
§ 31.57
Rip cords.
(a) If a rip cord is used for emergency
deflation, it must be designed and in-
stalled to preclude entanglement.
(b) The force required to operate the
rip cord may not be less than 25, or
more than 75, pounds.
(c) The end of the rip cord to be oper-
ated by the pilot must be colored red.
(d) The rip cord must be long enough
to allow an increase of at least 10 per-
cent in the vertical dimension of the
envelope.
§ 31.59
Trapeze, basket, or other
means provided for occupants.
(a) The trapeze, basket, or other
means provided for carrying occupants
may not rotate independently of the
envelope.
(b) Each projecting object on the tra-
peze, basket, or other means provided
for carrying occupants, that could
cause injury to the occupants, must be
padded.
§ 31.61
Static discharge.
Unless shown not to be necessary for
safety, there must be appropriate bond-
ing means in the design of each balloon
using flammable gas as a lifting means
to ensure that the effects of static dis-
charges will not create a hazard.
[Amdt. 31–2, 30 FR 3377, Mar. 13, 1965]
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