AC 27-1B, Chg 9 AC 27.1545A. § 27.1545 (AMENDMENT 27-51) AIRSPEED INDICATOR.
a. Explanation. Amendment 27-51 changed the requirements for marking the normal operating range of the airspeed indicator. Most modern glass cockpit designs utilize the “dark, quiet cockpit” concept, which means that yellow or red is presented to indicate abnormal conditions; green ranges are not presented. This approach has required a finding of equivalent safety with § 27.1545(b)(4) for applicants using an unmarked normal operating range instead of green.
(1) Section 27.1545(b)(4) continues to allow the normal operating range to be marked as green, but now permits an option for the normal operating range to be unmarked.
(2) The FAA has found it acceptable to only display the red VNE line when the VNE is in the displayed airspeed range. Section 27.1545(b)(2) was removed and § 27.1545(b)(1)(iii) was added to change the presentation of VNE (power-off). In the past, electro-mechanical gauges simultaneously displayed a red line to represent VNE (power-on) and a red cross-hatched radial line (“barber pole”) to represent VNE (poweroff). Modern glass cockpits are able to present VNE (power-off) and VNE (power-on) independently, which was infeasible with electro-mechanical gauges.
(3) Another change to this airworthiness standard is that the references to arcs and radials were removed to reflect the use of airspeed tapes. The technical requirements have not changed.
b. Procedures. The policy pertaining to these requirements, which is found in section 27.1543 of this AC, remains in effect with the following changes and additions.
(1) For compliance with §§ 27.771(a) and 27.1545(b)(4), electronic displays that lack green ranges must include features that permit the pilot to easily interpret (by way of glancing at the instrument) whether a parameter is in a precautionary range (yellow) or beyond a limit (red). In addition, consistency in markings should be maintained between the primary instrument and the standby instrument to reduce any confusion in the cockpit when failures require using the standby instrument.
(2) Section 27.1545(b)(1)(iii) requires that the airspeed indicator be marked with a red indication to show both VNE (power-on) and VNE (power-off). If VNE (power-off) is less than VNE (power-on) and both markings are simultaneously displayed, then each depiction needs to be clearly distinguishable from the other. Some electronic displays have represented both VNE (power-on) and VNE (power-off) with a red line. This has been found acceptable by the FAA provided (1) both VNE depictions are not simultaneously displayed and (2) the airspeed indicator automatically depicts the Page G - 25.7
AC 27-1B, Chg 9 change from VNE (power-on) to the VNE (power-off) upon power failure. Use of a redwhite barber pole to represent VNE (power-off) would still be acceptable when both VNE limits are simultaneously displayed. The FAA has also found it acceptable to represent the VNE limit as a red range only when the actual limit moves out of view, e.g. airspeed increases substantially above VNE.
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AC 27.1547.
§ 27.1547 (Amendment 27-13) MAGNETIC DIRECTION INDICATOR.
a. Explanation. This section identifies the requirement and location for a calibration placard for the magnetic direction indicator.
b. Procedures. One means of accomplishing the requirements of this regulation is commonly known as swinging the compass. A surveyed compass rose is laid out on an appropriate surface. The compass rose location should be free from the influence of steel structures, underground pipes and cables, reinforced concrete, and other aircraft.
The aircraft should be in an attitude that permits an accurate result. Normally the engines are in operation; however, if the aircraft is equipped with an auxiliary power unit which can supply electrical power for all electrical/electronic equipment or systems, this can be used instead of engine driven generators. Turn the aircraft on successive headings through 360°. It is recommended that the increments be every 30°; however, the increments should not exceed 45°. Prepare a placard to show the correction to be applied at each of the selected headings. When deviations of more than 10° are introduced by operation of any electrical/electronic equipment or systems, the placard should also be marked at each calibration heading showing the correction to be applied when such equipment or systems are turned on or energized. The placard resulting from this calibration should be installed on or near the magnetic direction indicator and identify which electrical loads, or combination of loads, are the cause of the excessive deviations.
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AC 27-1B, Chg 4 3/31/2014 AC 27.1549. § 27.1549 (Amendment 27- 16) POWERPLANT MARKINGS.
See section 27.1543 of this AC.
AC 27.1549A. § 27.1549 (Amendment 27-23) POWERPLANT INSTRUMENTS.
a. Explanation. Amendment 27-23 adds the requirement of marking each OEI limit and operating range. The limits should be clearly differentiated from other limits and ranges marked on the instrument. Refer to AC 20-88A, Instrument Markings.
b. Procedures. The method of compliance is unchanged.
AC 27.1549B. § 27.1549 (Amendment 27-29) POWERPLANT INSTRUMENTS.
a. Explanation. Amendment 27-29 introduces the optional ratings of 30-second/2-minute OEI. Paragraph 27.1549(e) has been revised to show that the limits for the 30-second OEI rating are not required to be marked. Use of the 30- second OEI rating is limited to critical phases of operation after a failure or precautionary shutdown of an engine. During this critical stage of operation the crew should not be required to monitor engine instruments to avoid exceedances. Automatic control of the 30-second OEI limits are required by § 27.1143(e) and therefore the 30-second OEI limits are not required to be marked.
b. Procedures. The method of compliance is unchanged except the marking of 30-second OEI limits are unnecessary.
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AC 27-1B, Chg 9 AC 27.1549C.§ 27.1549 (AMENDMENT 27-51) POWERPLANT INSTRUMENTS.
a. Explanation. Amendment 27-51 changed the requirements for displaying the normal operating range of powerplant instruments. Most modern glass cockpit designs utilize the “dark, quiet cockpit” concept, which means that yellow or red is presented to indicate abnormal conditions; green ranges are not presented. This approach has required a finding of equivalent safety with § 27.1549(b) for applicants using an unmarked normal operating range instead of green. Section 27.1549(b) continues to allow the green operating range to be displayed as green, but now permits an option for the normal operating range to be unmarked.
b. Procedures. The policy pertaining to these requirements, which is found in section 27.1543 of this AC, remains in effect with the following changes and additions.
For compliance with §§ 27.771(a) and 27.1549(b), electronic displays that lack green arcs must include features that permit the pilot to easily interpret (by way of glancing at the instrument) whether a parameter is in a precautionary range (yellow) or beyond a limit (red). In addition, consistency in displaying all required indications should be maintained between the primary instrument and the standby instrument to reduce any confusion in the cockpit when failures require using the standby instrument.
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AC 27.1551. § 27.1551 OIL QUANTITY INDICATORS.
a. Background. This section states that each oil quantity indicator must be marked with enough increments to indicate readily and accurately the quantity of oil.
b. Procedures. There are several different ways in which the oil quantity indicator may be presented. Some of the ones more prevalent in the industry are:
(1) Oil quantity indicator. (Generally used when large amounts of reserve oil are required.)
(2) Oil quantity dip stick. (Most common method of measuring engine oil.)
(3) Oil quantity sight indicator. (Generally used for measuring transmission and gearbox oil quantities.)
c. No matter what method of oil quantity indicator is used, the indicator should be marked so that the oil quantity can be accurately determined. This can range from increments marked in gallons, such as oil quantity indicators for large amounts of oil, to oil quantity indicators marked in quarts with full and add marks, such as engine dip sticks. Sight indicators with full and add marks have been used successfully for gearboxes. Sight indicators normally do not reflect quantities. These are some of the methods currently in use to indicate the oil quantity. In all cases, those methods identified above have proved to be acceptable methods of showing compliance with the § 27.1551.
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AC 27-1B, Chg 4 3/31/2014 AC 27.1553. § 27.1553 FUEL QUANTITY INDICATOR.
a. Explanation. This section describes the markings necessary to identify the portion of unusable fuel that cannot be used in level flight. Unusable fuel may be present in a design due to the relative configuration of the fuel tank to the fuel tank outlet (e.g., sumps, unusual elevations and/or configurations dictated by aircraft contours, etc.). If the unusable fuel supply for any tank is less than or equal to 1 gallon or is less than or equal to 5 percent of the tank capacity, whichever is greater, this section does not apply.
b. Procedures. For each fuel tank which has an unusable fuel capacity exceeding 1 gallon or 5 percent of the tank capacity, whichever is greater, the following should be accomplished.
(1) Calibration computations, measurements, and/or tests should determine the zero (empty) position on the fuel quantity indicator. (reference § 27.1337).
(2) The lowest reading obtainable in level flight must be determined by computation, measurement, and/or testing.
(3) Once the instrument readings defined by paragraphs b(1) and (2) above have been determined, a red arc should be placed between the readings on the fuel quantity indicator.
(4) Appropriate notations should be made in the flight manual to define the intent of the red arc to the flightcrew (reference § 27.1585(e)).
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AC 27.1555. § 27.1555 (Amendment 27-21) CONTROL MARKINGS.
a. Explanation. Section 27.1301(b) requires that all installed equipment be labeled to identify its function and operations; however, this section provides more detailed requirements for control markings. Specific criteria are given for powerplant fuel controls, fuel quantity markings, and landing gear controls. The requirement to color emergency controls red is in this section.
b. Procedures.
(1) Section 27.1555(a) requires each cockpit control, other than flight controls whose function is not obvious, to be appropriately labeled. The primary flight controls are the cyclic, collective, and the directional control (tail rotor) pedals. For the control to be appropriately labeled, the rule requires that there should be an obvious and clear demarcation of the function and operation of the control. When performing the evaluation to determine the adequacy of markings, remember that only those controls which are quite traditional should be judged to be obvious in their operation. An example of this has been the navigation/communication (NAV/COMM) control heads.
The more traditional control units had concentric knobs of decreasing size for the selection of frequency. Because this system was so common for such a period of time, the finding was generally made that the function of this control was obvious and thus did not require a specific marking. However, as more current technology digital electronic controls were used, the frequency selectors were judged not to be obvious in their operation, and their function and operation were required to be labeled.
(2) Review design data and available hardware to ensure the powerplant fuel controls are clearly and permanently marked such that:
(i) Selector valve control clearly shows each position for each tank and each crossfeed configuration.
(ii) Tank selection sequences required for safe operation are clearly and permanently marked on or adjacent to the required selector.
(iii) Each control valve is clearly marked to show the position of the controls for each engine on multiengine rotorcraft.
(3) Review design data and available hardware to ensure that usable fuel capacity is clearly marked as follows:
(i) If the fuel system has no selector controls, usable fuel capacity must be shown on the fuel quantity indicator (reference paragraph AC 27.1553).
(ii) If the system has selector controls, the usable fuel capacity at each selector position must be clearly shown near the selector position.
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A C 27-1B, Chg 4 3/ 31/2014
(4) Markings of essential visual position indicators must be obvious and within view of required crewmembers. Landing gear markings normally include indications for down, intermediate/unsafe, and up. Accepted symbology has included arrows for up/down indications, crosshatching of intermediate/unsafe, various combinations of colored lights, and combinations of all of the above. Cockpit presentation is further discussed in paragraph AC 27.729. Emergency controls which should be marked in red include those used for f irewall/emergency fuel shutoff, landing gear blowdown/emergency release, fire extinguishers, float activation, cargo hook release and fuel dump. The method of operation of emergency controls must be clearly marked. In the case of switches and buttons, the method of operation is often inherently obvious without dedicated labeling.
(5) The two most obvious m eans of displaying landing gear op erating speed are use of a placard or an appropriate mark i n the airspeed indicator.
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AC 27.1555A. § 27.1555 (AMENDMENT 27-51) CONTROL MARKINGS.
a. Explanation. Amendment 27-51 changed the requirements for marking the usable fuel capacity for designs that have no selector controls. The previous requirement for marking the usable fuel capacity near the fuel quantity indicator is not practical for modern glass cockpit designs.
With older, electro-mechanical designs, the actual fuel capacity was not marked on the fuel quantity gage. Traditionally these designs used a placard indicating the usable fuel capacity next to the fuel quantity indicator to assist with flight planning and refueling.
Modern glass cockpit designs provide digital indication of the remaining usable fuel quantity at all times while the total usable fuel capacity is typically included, although not required, within the rotorcraft flight manual.
b. Procedures. All of the policy pertaining to this section remains in effect with the following changes:
Section 27.1555(c)(1) requires that, for fuel systems having no selector controls, the usable fuel capacity of the system be indicated at the fuel quantity indicator unless the system capacity is provided by another system or equipment readily accessible to the pilot. Such information may be provided digitally on a multi-function display (MFD) synoptic page such as the fuel system or aircraft weight and balance page. In addition to the digital representation, § 27.1555(c)(1)(ii) requires that the fuel system capacity be contained in the limitations section of the rotorcraft flight manual. The digital display of the fuel system capacity used in conjunction with the total usable fuel quantity provided in the rotorcraft flight manual limitations section will permit the flight crew to approximate endurance and will assist with refueling. Alternately, for designs that do not provide a digital readout of the usable fuel capacity and include the information in the rotorcraft flight manual, the total usable fuel capacity must be displayed at the fuel quantity indicator in accordance with § 27.1555(c)(1).
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AC 27-1B, Chg 4 3/31/2014 AC 27.1557. § 27.1557 (Amendment 27-11) MISCELLANEOUS MARKINGS AND PLACARDS.
a. Explanation. Placards or equivalent markings that are conspicuous and durable are required to identify design/operational limits or information for certain seats, baggage/cargo compartments, ballast, fuel and oil tanks, and emergency exits. The color red is specified for exit placards.
[AC 27.1557 continued on next page.] Page G - 28.2
(1) Baggage, cargo and ballast markings must state the allowable maximum weight and the distributed (floor) loading, where appropriate. The markings should prevent overloading the compartment and its floor or the ballast installation.
(2) Seats must be permanently marked as prescribed with the design allowable occupant weight if the seat is designed for less than a 170-pound occupant. The placard specified here is not related to a rotorcraft operating weight or loading limitation.
(3) Fuel and oil tank filler openings must be marked as prescribed to provide essential information for proper fluids and to provide limitation data for pressures in refueling/defueling systems if installed.
(4) Emergency exit placards or markings, inside and outside, shall be red (red with white background for visibility or reversed colors). Locating signs and operating signs or placards are required. See paragraph AC 27.783 (§ 27.783) for door marking requirements.
(5) Markings must be conspicuous and durable as prescribed in § 27.1541(b).
b. Procedures.
(1) The type design drawings such as general “markings” drawing should be reviewed for compliance. During an interior/exterior compliance inspection, usually conducted prior to issuing the TIA, compliance with the standard should be confirmed or ensured. If an FAA/AUTHORITY conducted F&R program is prescribed, complete “production” aircraft markings should be installed prior to beginning the program. As a continuation of the FAA/AUTHORITY evaluation, the markings shall be checked during the F&R program. Contrasting colors are essential. Various paint schemes should be checked for compliance.
(2) Allowable maximum weight and floor distributed loading and possibly baggage tiedown and security instructions are generally included in the cargo compartment markings. A placard, stencil, or equivalent that is conspicuous and durable may be placed on the compartment door, wall, etc.
(3) For fuel and oil filler markings, contrasting colors between letters and background are essential. The visibility of the markings should not be affected by changing paint schemes or colors. This may be accomplished by decals having a contrasting background. Stencil markings should be discouraged for fuel and oil markings.
(4) Emergency exit marking performance standards are also contained in paragraph AC 27.807. It is recommended that the exit locating sign (interior) be readable from the farthest seat in the cabin and that the identification of the operating handle or device and the operating instructions be readable from a distance of 30 inches. It is further recommended that external exit instructions or markings have Page G - 29