and to prevent contamination from sources outside the chamber enclosing the drive connection. The design of the engine must allow for the examination, adjustment, or removal of each accessory required for engine operation.
*** Guidance. The INTENT of this section is that design and construction of engine accessory drives and their mount pads permit proper engine operation when loaded; prevent contamination and excessive loss of oil; and permit inspection, adjustment, and removal of accessories.
Incorporations: None.
References: None.
If engine accessory drives are designed to protect the engine from potential unsafe conditions, such as those due to accessory seizure overtorque, by designed failure of a drive shaft shear section; then, it should be shown that the shear section will not fail under all normal operating load conditions, or otherwise result in damage or hazard to the engine or its subsequent aircraft installation.
27. Section 33.27, Turbine, Compressor, Fan and Turbosupercharger Rotors.
Section 33.27 Turbine, compressor, fan and turbosupercharger rotors.
(a) Turbine, compressor, fan, and turbosupercharger sufficient strength to withstand the test conditions specified in paragraph (c) of this section.
(b) The design and functioning of engine control devices, systems, and instruments must give reasonable assurance that those engine operating limitations that affect turbine, compressor, and turbosupercharger rotor structural integrity will not be exceeded in service.
(c) The most critically stressed rotor component (except blades) of each turbine, compressor, and fan, including integral drum rotors and centrifugal compressors in an engine or turbosupercharger, as determined by analysis or other acceptable means, must be tested for a period of 5 minutes--
(1) At its maximum operating temperature, except as provided in paragraph (c)(2) (iv) of this section; and
(2) At the highest speed of the following, as applicable:
(i) 120 percent of its maximum permissible r.p.m. if tested on a rig and equipped with blades or blade weights.
Chap 3 Par 26 45
(ii) 115 percent of its maximum permissible r.p.m. if tested on an engine.
(iii) 115 percent of its maximum permissible r.p.m.
if tested on a turbosupercharger driven by a hot gas supply from a special burner rig.
(iv) 120 percent of the r.p.m. at which, while cold spinning, it is subject to operating stresses that are equivalent to those induced at the maximum operating temperature and maximum permissible r.p.m.
105 percent of the highest speed that would result from failure of the most critical component or system in a representative installation of the engine.
(vi) The highest speed that would result from the failure of any component or system in a representative installation of the engine, in combination with any failure of a component or system that would not normally be detected during a routine preflight check or during normal flight operation.
Following the test, each rotor must be within approved dimensional limits for an overspeed condition and may not be cracked.
*** Guidance. The INTENT of this section is to assure engine rotor structural integrity, by design and functioning of engine control and instrumentation systems, to inhibit exceedances of operating limitations; and, to demonstrate that each engine rotor has sufficient strength to withstand a maximum overspeed condition without cracking.
Incorporations: None.
References: None.
If the engine bill-of-material includes instrumentation (including sensors), then such must be designed and must function so as to assure safe operation, (structural integrity of the inservice engine). Note that the rule requires the most critically stressed rotor component (including discs, spacers, cooling lates) of each turbine, compressor, and tan to be tested at a naximum overspeed condition for 5 minutes. Determination of the maximum overspeed condition needs to consider the 6 cases defined in the rule -- including shaft failures which decouple a turbine rotor from its load. Rotor shafts are not considered prime reliable in that it is assumed that shaft failures will occur, both as a single failure and in combination with another undetected or dormant failure.
b. A rotor burst test, in lieu of the presently required 5- minute overspeed test, could be found as an acceptable equivalent means of compliance. In the case of output shaft (low) turbines, Chap 3 46 Par 27
the rotor burst test would be performed, in conjunction with an abrupt load decouple test, to demonstrate the existence of adequate margin between the peak speed and the burst speed. The actual burst speed must be corrected to account for the effects of Spect non actual material propertise, very poet fication timum material properties. Acceptance criteria must show at least a 5.0 percent speed margin between the abrupt decouple peak speed and correlates fe lovin taegity ovided sna hits qui reference, including significant differences:
Chap 3 Par 27 47
TABLE 27-1. ROTOR INTEGRITY REGULATIONS/GUIDANCE
REGULATION & CORRESPONDING SIGNIFICANT GUIDANCE
EFFECTIVITY DATE GUIDANCE & DIFFERENCES
ISSUE DATE FAR 33-13, 08/18/89 AC 33-3, • POST-TEST ACCEPTANCE FAR 33-12, 10/03/88 09/09/68 CRITERIA OF THE FAR TAKES FAR 33-11, 04/24/86 PRECEDENCE OVER THAT OF FAR 33-10, 03/26/84 THE AC.
FAR 33-9, 10/14/80 FAR 33-8, 05/02/77 FAR 33-7, 02/01/77 FAR 33-6, 10/31/74 FAR 33-5, 03/01/74 AC 33-3, • FAR DOES NOT FAR 33-4, 04/23/71 IDENTIFY POST-TEST ACCEPTANCE CRITERIA.
FAR 33-3, 04/03/67 AC 20-26, • POST-TEST ACCEPTANCE FAR 33-2, 07/06/66 CH.2 CRITERIA OF THE AC 07/08/65 REVISED BY CH.2.
(PARAGRAPH 4C).
FAR 33 & AC 20-26 • SUPERSEDES FAA 33-1, 02/01/65 CH. 1, 09/18/64; MEMORANDUM OF 02/09/59.
AC 20-26, • OVERSPEED TEST 07/22/64 CONDITION ANALYSIS BASED ON FAILURE (S) .
CAR 13-6, 04/22/64 FAA POLICY • ESTABLISHES CAR 13-5, 02/12/63 MEMORANDUM, REQUIREMENTS FOR CAR 13-4, 05/03/62 02/09/59 SUBSTANTIATION OF TURBINE CAR 13-3, 10/01/59 & COMPRESSOR ROTOR INTEGRITY. NOTE THAT THE
OVERSPEED TEST CONDITION
TO BE RUN IS BASED ON
ANALYSIS OF CONTROL
SYSTEM FAILURE(S) AND ON
A FACTOR OF TAKEOFF R.P.M., WHICHEVER YIELDS THE GREATEST STRESS.
• MUST DEMONSTRATE
OVERSTRESS MARGIN, BUT
DOES NOT OFFER ACCEPTANCE CRITERIA.
CAR 13-2, 05/17/58 NONE N/A CAR 13-1, 08/12/57 CAR 13, 06/15/56 Chap 3 48 Par 27
28. Section 33.29, Instrument Connection.
Section 33.29 Instrument connection.
(a) Unless it is constructed to prevent its connection to an incorrect instrument, each connection provided for powerplant instruments required by aircraft of the engine in compliance with any engine limitation airworthiness regulations or necessary to insure operation no identity we must be marked to identify it with its corresponding instrument.
(b) A connection must be provided on each turbojet engine for an indicator system to indicate rotor system unbalance.
*** Guidance. The INTENT of this section is to prevent misconnections of engine-required instrumentation, and to provide a drawing location for rotor unbalance sensing.
Incorporations: None.
References: None.
An acceptable method of complying with FAR Section 33.29 (b) is to Haterically, turbojet has ben interpreted to sure inelude ton Chap 3 Par 28 49 (and 50)
SECTION 3. SUBPART C--DESIGN AND CONSTRUCTION; RECIPROCATING
AIRCRAFT ENGINES
29. Section 33.33, Vibration.
Section 33.33 Vibration.
The engine must be designed and constructed to function throughout its normal operating range of crankshaft rotational speeds and engine powers without inducing excessive stress in any of the engine parts because of vibration and without imparting excessive vibration forces to the aircraft structure.
*** Guidance. The INTENT of this section is self-evident.
Incorporations: None.
References: None.
30. Section 33.35, Fuel and Induction System.
Section 33.35 Fuel and induction system.
(a) The fuel system of the engine must be designed and constructed to supply an appropriate mixture of fuel to the cylinders throughout the complete operating range of the engine under all flight and atmospheric conditions.
The intake passages of the engine through which air or fuel in combination with air passes for combustion purposes must be designed and constructed to minimize the danger of ice accretion in those passages. The engine must be designed and constructed to permit the use of a means for ice prevention.
(c) The type and degree of fuel filtering necessary for protection of the engine fuel system against foreign particles in the fuel must be specified. The applicant must show that foreign particles passing through the prescribed filtering means will not critically impair engine fuel system functioning.
(d) Each passage in the induction system that conducts a mixture of fuel and air must be self-draining, to prevent a liquid lock in the cylinders, in all attitudes that the applicant establishes as those the engine can have when the aircraft in which it is installed is in the static ground attitude.
must show for each fluid injection (other than fuel) fluid is adequately controlled.
Chap 3 Par 29 51
Guidance. The INTENT of this section is self-evident.
Incorporations: None.
References: None.
31. Section 33.37, Ignition System.
Section 33.37 Ignition system.
Each spark ignition engine must have a dual ignition system with at least two spark plugs for each cylinder and two separate electric circuits with separate sources of electrical energy, or have an ignition system of equivalent in-flight reliability.
*** Guidance. The INTENT of this section is self-evident.
Incorporations: None.
References: None.
The engine installation instructions should define the characteristics and interface requirements of all aircraft sources of electrical power required by the engine ignition system.
32. Section 33.39, Lubrication System.
Section 33.39 Lubrication system.
The lubrication system of the engine must be designed and constructed so that it will function properly in all flight attitudes and atmospheric conditions in which the airplane is expected to operate. In wet sump engines, this requirement must be met when only one-half of the maximum lubricant supply is in the engine. The lubrication system of the engine must be cutted to allow instaling a meane of cooling the lubricant.
(c) The crankcase must be vented to the atmosphere to preclude leakage of oil from excessive pressure in the crankcase.
*** Guidance. The INTENT of this section is self-evident.
Incorporations: None.
References: None.
Chap 3 52 Par 30
SECTION 4. SUBPART D--BLOCK TESTS; RECIPROCATING AIRCRAFT ENGINES
33. Section 33.42, General.
Section 33.42 General.
Before each endurance test required by this subpart, the adjustment setting and functioning characteristic of each component having an adjustment setting and a functioning characteristic that can be established independent of installation on the engine must be established and recorded.
*** Guidance. The INTENT of this section is self-evident.
Incorporations: None.
References: None.
34. Section 33.43, Vibration Test.
Section 33.43 Vibration test.
(a) Each engine must undergo a vibration survey to establish the torsional and bending vibration characteristics of the crankshaft and the propeller shaft or other output shaft, over the range of crankshaft speed and engine power, under steady state and transient conditions, from idling speed to either 110 percent of the desired maximum continuous speed rating or 103 percent of the maximum desired takeoff speed rating, whichever is higher. The survey must be conducted using, for airplane engines, the same configuration of the propeller type which is used for the endurance test, and using, for other engines, the same configuration of the loading device type which is used for the endurance test.
(b) The torsional and bending vibration stresses of the crankshaft and the propeller shaft or other output shaft may not exceed the endurance limit stress of the material from which the shaft is made. If the maximum stress in the shaft cannot be shown to be below the endurance limit by measurement, the vibration frequency and amplitude must be measured. The peak amplitude must be shown to produce a stress below the endurance limit; i1 not, the engine must be run at the condition producing the reversal tude en sustained that fatigue failures, for other shafts, until it is shown that fatigue will not occur within the endurance limit stress of the material.
Chap 3 Par 33 53
(c) Each accessory drive and mounting attachment must be loaded, with the loads imposed by each accessory used only for an aircraft service being the limit load specified by the applicant for the drive or attachment point.
(d) The vibration survey described in paragraph (a) of this section must be repeated with that cylinder not firing which has the most adverse vibration effect, in order to establish the conditions under which the engine can be operated safely in that abnormal state. However, for this vibration survey, the engine speed range need only extend from idle to the maximum desired takeoff speed, and compliance with paragraph (b) of this section need not be shown.
*** Guidance. The INTENT of this section is to demonstrate that the engine is free of potentially harmful vibration under all normal operating conditions.
Incorporations: None.
References: None.
When the engine is used to drive a propeller, the engine vibration including the propeller governor and spinner. A satisfactory finding from the engine vibration survey will serve to permit certification of the engine, as far as its vibration is concerned.
35. Section 33.45, Calibration Tests.
Section 33.45 Calibration tests.
(a) Each engine must be subjected to the calibration tests necessary to establish its power characteristics and the conditions for the endurance test specified in Section
33.49. The results of the power characteristics calibration tests form the basis for establishing the characteristics of the engine over its entire operating cange or crankshait rotational speeds, maniiold pressures, tuel/air mixture settings, and altitudes. Power ratings are based upon standard atmospheric conditions with only those accessories installed which are essential for engine functioning.
A power check at sea level conditions must be accomplished on the endurance test engine after the endurance test. Any change in power characteristics which occurs during the endurance test must be determined.
Measurements taken during the final portion of the Chap 3 54 Par 34
endurance test may be used in showing compliance with the requirements of this paragraph.
*** Guidance. The INTENT of this section is self-evident.
Incorporations: None.
References: None.
36. Section 33.47, Detonation Test.
Section 33.47 Detonation test.
Each engine must be tested to establish that the engine can function without detonation throughout its range of intended conditions of operation.
*** Guidance. The INTENT of this section is self-evident.
Incorporations: AC 33.47-1, Detonation Testing in Reciprocating Aircraft Engines," dated June 27, 1988.
References: None.
37. Section 33.49 Endurance Test.
Section 33.49 Endurance test.
(a) General.
endurance test that includes a total of 150 hours of operation (except as provided in paragraph (e) (1) (iii) of this section) and, depending upon the type and contemplated use of the engine, consists of one of the series of runs specified in paragraphs (b) through (ẹ) of this section, as applicable. The runs must be made in the order found appropriate by the Administrator for the particular engine being tested. During the endurance test the engine power and the crankshaft rotational speed must be kept within † 3 percent of the rated values. During the runs at rated takeoff power and for at least 35 hours at rated maximum continuous power, one cylinder, must be operated at not less than the limiting temperature, the other cylinders must be operated at a temperature not lower than 50 degrees F. below the limiting temperature, and the oil inlet temperature must be maintained within + 10 degrees F. of the limiting temperature. An engine that is equipped with a propeller shaft must be fitted for the endurance test with a propeller that thrust-loads the Chap 3 Par 35 55
engine to the maximum thrust which the engine is designed to resist at each applicable operating condition specified in this section. Each accessory drive and mounting attachment must be loaded. During operation at rated takeoff power and rated maximum continuous power, the load imposed by each accessory used only for an aircraft service must be the limit load specified by the applicant for the engine drive or attachment point.
(b) Unsupercharged engines and engines incorporating gear-driven single speed supercharger. For engines not incorporating a supercharger and for engines incorporating a gear-driven single-speed supercharger the applicant must conduct the following runs:
(1) A 30-hour run consisting of alternate periods of 5 minutes at rated takeoff power with takeoff speed, and 5 minutes of maximum best economy cruising power or maximum recommended cruising power.
(2) A 20-hour run consisting of alternate periods of 1-1/Z hours at rated maximum continuous power with maximum continuous speed, and 1/2 hour at 75 percent rated maximum continuous power and 91 percent maximum continuous
(3) A 20-hour run consisting of alternate periods of 1-1/2 hours at rated maximum continuous power with maximum continuous speed, and 1/2 hour at 70 percent rated maximum continuous power and 89 percent maximum continuous 1]20-hraredm cimisting of alterate periods of 1-1/2 hours at rated maximum continuous power with maximum continuous speed, and 1/2 hour at 65 percent rated maximum continuous power and 87 percent maximum continuous speed.
(5) A 20-hour run consisting of alternate periods of 1-1/2 hours at rated maximum continuous power with maximum continuous speed, and 1/L hour at 60 percent rated maximum continuous power and 84.5 percent maximum continuous speed.
(6) A 20-hour run consisting of alternate periods of 1-1/2 hours at rated maximum continuous power with maximum continuous speed, and 1/2 hour at 50 percent rated maximum continuous power and 79.5 percent maximum continuous speed.
(7) A 20-hour run consisting of alternate periods of 2-1/2 hours at rated maximum continuous power with maximum continuous speed, and 2-1/2 hours at maximum best economy cruising power or at maximum recommended cruising power.
(c) Engines incorporating a gear-driven two speed supercharger. For engines incorporating a gear-driven two-speed supercharger the applicant must conduct the following runs:
(1) A 30-hour run consisting of alternate periods in the lower gear ratio of 5 minutes at rated takeoff power with takeoff speed, and 5 minutes at maximum best economy cruising power or at maximum recommended cruising power.
If a takeoff power rating is desired in the higher gear Chap 3 56 Par 37
ratio, 15 hours of the 30-hour run must be made in the higher gear ratio in alternate periods of five minutes at the observed horsepower obtainable with the takeoff critical altitude manifold pressure and takeoff speed, and minutes at 70 percent high ratio rated maximum continuous power and 89 percent high ratio maximum continuous speed.
(2) A 15-hour run consisting of alternate periods in the lower gear ratio of 1 hour of rated maximum continuous power with maximum continuous speed, and 1/2 hour at 75 percent rated maximum continuous power and 91 percent maximum continuous speed.
(3) A 15-hour run consisting of alternate periods in the lower gear ratio of 1 hour at rated maximum continuous power with maximum continuous speed, and 1/2 hour at 70 percent rated maximum continuous power and 89 percent maximum continuous speed.
(4) A 30-hour run in the higher gear ratio at rated maximum continuous power with maximum continuous speed.
A 5-hour run consisting of alternate periods of 5 minutes in each of the supercharger gar ratios. The first 5 minutes of the test must be made at maximum continuous speed in the higher gear ratio and the observed horsepower obtainable with 90 percent of maximum continuous manifold pressure in the higher gear ratio under sea level conditions. The condition for operation for the aiternate 5 minutes in the lower gear ratio must be that obtained by shifting to the lower gear ratio at constant speed.
(6) A 10-hour run consisting of alternate periods in the lower gear ratio of 1 hour at rated maximum continuous power with maximum continuous speed, and 1 hour at 65 percent rated maximum continuous power and 87 percent maximum continuous speed.
(7) A 10-hour run consisting of alternate periods in the lower gear ratio of 1 hour at rated maximum continuous power with maximum continuous speed, and 1 hour at 60 percent rated maximum continuous power and 84.5 percent maximum continuous speed.
(8) A 10-hour run consisting of alternate periods in the lower gear ratio of 1 hour at rated maximum continuous power with maximum continuous speed, and 1 hour at 50 percent rated maximum continuous power and 79.5 percent maximum continuous speed.
(9) A 20-hour run consisting of alternate periods in the lower gear ratio of 2 hours at rated maximum continuous power with maximum continuous speed, and 2 hours at maximum best economy cruising power and speed or at maximum recommended cruising power and speed.
(10) A 5-hour run in the lower gear ratio at maximum best economy cruising power and speed or at maximum recommended cruising power and speed.
Chap 3 Par 37 57