[Code of Federal Regulations]
[Title 14, Volume 1]
[Revised as of January 1, 2003]
From the U.S. Government Printing Office via GPO Access
[CITE: 14CFR33.71]

[Page 746-748]
 
                     TITLE 14--AERONAUTICS AND SPACE
 
CHAPTER I--FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION
 
PART 33--AIRWORTHINESS STANDARDS: AIRCRAFT ENGINES--Table of Contents
 
      Subpart E--Design and Construction; Turbine Aircraft Engines
 
Sec. 33.71  Lubrication system.

    (a) General. Each lubrication system must function properly in the 
flight attitudes and atmospheric conditions in which an aircraft is 
expected to operate.
    (b) Oil strainer or filter. There must be an oil strainer or filter 
through which all of the engine oil flows. In addition:

[[Page 747]]

    (1) Each strainer or filter required by this paragraph that has a 
bypass must be constructed and installed so that oil will flow at the 
normal rate through the rest of the system with the strainer or filter 
element completely blocked.
    (2) The type and degree of filtering necessary for protection of the 
engine oil system against foreign particles in the oil must be 
specified. The applicant must demonstrate that foreign particles passing 
through the specified filtering means do not impair engine oil system 
functioning.
    (3) Each strainer or filter required by this paragraph must have the 
capacity (with respect to operating limitations established for the 
engine) to ensure that engine oil system functioning is not impaired 
with the oil contaminated to a degree (with respect to particle size and 
density) that is greater than that established for the engine in 
paragraph (b)(2) of this section.
    (4) For each strainer or filter required by this paragraph, except 
the strainer or filter at the oil tank outlet, there must be means to 
indicate contamination before it reaches the capacity established in 
accordance with paragraph (b)(3) of this section.
    (5) Any filter bypass must be designed and constructed so that the 
release of collected contaminants is minimized by appropriate location 
of the bypass to ensure that the collected contaminants are not in the 
bypass flow path.
    (6) Each strainer or filter required by this paragraph that has no 
bypass, except the strainer or filter at an oil tank outlet or for a 
scavenge pump, must have provisions for connection with a warning means 
to warn the pilot of the occurence of contamination of the screen before 
it reaches the capacity established in accordance with paragraph (b)(3) 
of this section.
    (7) Each strainer or filter required by this paragraph must be 
accessible for draining and cleaning.
    (c) Oil tanks. (1) Each oil tank must have an expansion space of not 
less than 10 percent of the tank capacity.
    (2) It must be impossible to inadvertently fill the oil tank 
expansion space.
    (3) Each recessed oil tank filler connection that can retain any 
appreciable quantity of oil must have provision for fitting a drain.
    (4) Each oil tank cap must provide an oil-tight seal.
    (5) Each oil tank filler must be marked with the word ``oil.''
    (6) Each oil tank must be vented from the top part of the expansion 
space, with the vent so arranged that condensed water vapor that might 
freeze and obstruct the line cannot accumulate at any point.
    (7) There must be means to prevent entrance into the oil tank or 
into any oil tank outlet, of any object that might obstruct the flow of 
oil through the system.
    (8) There must be a shutoff valve at the outlet of each oil tank, 
unless the external portion of the oil system (including oil tank 
supports) is fireproof.
    (9) Each unpressurized oil tank may not leak when subjected to a 
maximum operating temperature and an internal pressure of 5 p.s.i., and 
each pressurized oil tank may not leak when subjected to maximum 
operating temperature and an internal pressure that is not less than 5 
p.s.i. plus the maximum operating pressure of the tank.
    (10) Leaked or spilled oil may not accumulate between the tank and 
the remainder of the engine.
    (11) Each oil tank must have an oil quantity indicator or provisions 
for one.
    (12) If the propeller feathering system depends on engine oil--
    (i) There must be means to trap an amount of oil in the tank if the 
supply becomes depleted due to failure of any part of the lubricating 
system other than the tank itself;
    (ii) The amount of trapped oil must be enough to accomplish the 
feathering opeation and must be available only to the feathering pump; 
and
    (iii) Provision must be made to prevent sludge or other foreign 
matter from affecting the safe operation of the propeller feathering 
system.
    (d) Oil drains. A drain (or drains) must be provided to allow safe 
drainage of the oil system. Each drain must--
    (1) Be accessible; and
    (2) Have manual or automatic means for positive locking in the 
closed position.

[[Page 748]]

    (e) Oil radiators. Each oil radiator must withstand, without 
failure, any vibration, inertia, and oil pressure load to which it is 
subjected during the block tests.

[Amdt. 33-6, 39 FR 35466, Oct. 1, 1974, as amended by Amdt. 33-10, 49 FR 
6852, Feb. 23, 1984]