Typically, two “bugs” are acceptable; three or more are questionable. “Bugs” may also be used on a variety of instruments other than the airspeed indicator.
(10) Reference Material. Additional procedures for marking powerplant instruments are contained in AC 20-88A. Where conflicts for rotorcraft exist between AC 20-88A and this document, the more recently dated guidance should be utilized.
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AC 29.1545. § 29.1545 (Amendment 29-17 AIRSPEED INDICATOR. (SEE PARAGRAPH AC 29.1543).
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AC 29.1545A. § 29.1545 (AMENDMENT 29-59) AIRSPEED INDICATOR.
a. Explanation. Amendment 29-59 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 § 29.1545(b)(4) for applicants using an unmarked normal operating range instead of green.
(1) Section 29.1545(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 29.1545(b)(2) was removed and § 29.1545(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 29.1543 of this AC, remains in effect with the following changes and additions.
(1) For compliance with §§ 29.771(a) and 29.1545(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 29.1545(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 Page G - 27.7
been found acceptable by the FAA provided (1) both VNE depictions are not simultaneously displayed and (2) the airspeed indicator automatically depicts the change from VNE (power-on) to the VNE (power-off) upon power failure. Use of a red - white 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 29.1547. § 29.1547 MAGNETIC DIRECTION INDICATOR.
a. Explanation. This regul ation identifies the requirement for a calibration placard for the magnetic direction indicator and where it should be located.
b. Procedures. One means of accomplis hing 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 which permits an accurate result. Normally the engines are in operation; however, if the rotorcraft is equipped with an auxiliary power unit which can supply all required electrical power, this can be used in lieu 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 significant errors are introduced by operation of electrical/electronics 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.
AC 29.1549. § 29.1549 (Amendment 29-26) POWERPLANT INSTRUMENTS.
(SEE PARAGRAPH AC 29.1543).
AC 29.1549A. § 29.1549 (Amendment 29-34) POWERPLANT INSTRUMENTS.
a. Explanation. Amendment 29-34 introduc es the optional ratings of 30-second/ 2-minute OEI. Section 29.1549(e) has been revi sed 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 operati on the crew should not be required to monitor engine instruments to avoid exceedances. Auto matic control of the 30-second OEI limits are required by Section 29.1143(e), therefore the 30-second OEI limits are not required to be marked.
b. Procedures. The method of compli ance is unchanged except the marking of 30-second OEI limits is unnecessary.
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AC 29.1549B. § 29.1549 (AMENDMENT 29-59) POWERPLANT INSTRUMENTS.
a. Explanation. Amendment 29-59 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 § 29.1549(b) for applicants using an unmarked normal operating range instead of green. Section 29.1549(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 29.1549 of this AC, remains in effect with the following changes and additions.
For compliance with §§ 29.771(a) and 29.1549(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 shall 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 29.1551. § 29.1551 OIL QUANTITY INDICATORS.
a. Background. This section states that each oil quantity indicator must be marked with enough increments to indicate oil quantity readily and accurately.
b. Procedures. There are several differ ent ways in which the oil quantity indicator may be presented. Some of the ones mo re 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. (Gener ally 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 an acceptable method of showing compliance with § 29.1551.
AC 29.1553. § 29.1553 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 fo r 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 wh ich 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 § 29.1337).
(2) The lowest reading obtainable in level flight must be determined by computation, measurement, and/or testing.
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(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 § 29.1585(e)).
AC 29.1555. § 29.1555 (Amendment 29-24) CONTROL MARKINGS.
a. Explanation. Section 29.1301(b) requires that all installed equipment be labeled to identify its function and operation. 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 29.1555(a) requires that each cockpit control, other than flight controls whose function is not obvious, must 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, it should be remembered 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 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:
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(i) If the fuel system has no selector controls, usable fuel capacity must be shown on the fuel quantity indicator (reference paragraph AC 29.1553).
(ii) If the system has selector controls, the usable fuel capacity at each selector position must be clearly shown near the selector position.
(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 for intermediate/unsafe, various combinations of colored lights, and combinations of all of the above. Cockpit presentation is further discussed in paragraph AC 29.729. Emergency controls which should be marked in red include those used for firewall/emergency fuel shutoff, landing gear blowdown/emergency release, fire extinguishers, float activation, cargo hook release and fuel dump. T he 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 means of displaying landing gear operating speed are use of a placard or an appropriate mark in the airspeed indicator.
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AC 29.1555A. § 29.1555 (AMENDMENT 29-59) CONTROL MARKINGS.
a. Explanation. Amendment 29-59 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 29.1555(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, § 29.1555(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 § 29.1555(c)(1).
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AC 29.1557. § 29.1557 (Amendment 29-26) MISCELLANEOUS MARKING S AND PLACARDS.
a. Explanation.
(1) This section specifies the markings and placards associated with baggage, cargo, ballast, seats, fuel, oil, and emergency exits.
(2) The data contained in these markings and placards must conform to the approved type design of the rotorcraft.
b. Procedure.
(1) The placard for baggage and cargo compartment limitations should clearly state all limitations which apply to that compartment. The limitations may apply to what is carried, the dimensions, exact location, and maximum weight allowed. The placard should be located in a place where it cannot be obstructed and is clearly visible before or after opening the compartment. For ballast, the placard should state the type of ballast permitted (lead plate, shot bags, etc.), the exact placement, if applicable, and the maximum allowable weight. If there are other limitations which are applicable to these compartments, they should be clearly stated.
(2) Seats in rotorcraft are designed to meet vertical descent loads which have been established to insure a certain level of occupant survivability in the event of a hard Page G - 30
landing or crash. To meet these load requirements, 170 pounds was established as the minimum occupant design weight. If the seat was designed and certified to an occupant weight lower than 170 pounds, the seat must carry a placard in a conspicuous place, which limits the weight of the seat occupant to the certified weight.
(3) The fuel and oil filler opening markings are self-explanatory.
(4) Emergency exit placards must be so distinctive and clear that they are easily identified and understood under extreme and intense circumstances by individuals who have little or no familiarity with aircraft escape procedures.
AC 29.1559. § 29.1559 (Amendment 29-24) LIMITATIONS PLACARD.
a. Explanation.
(1) The content and location requirements on the placard are specified in the standard. The content and information in the placard has changed significantly as a result of associated and complementary changes in the airworthiness rules and the maintenance and operating rules.
(2) By adoption of FAR Part 29 in 1965, the standard (and its predecessor CAR Part 7) required compliance with the operating limitations in the approved Rotorcraft Flight Manual.
(3) With the adoption of an Airworthiness Limitations Section for the maintenance manual as stated in § 29.1529 of Amendment 29-4, the content of the placard was changed significantly to require compliance with the requirements in that section.
(4) Amendment 29-20, issued in 1980, adopted standards requiring “Instructions for Continued Airworthiness” (maintenance manual). This manual may include an Airworthiness Limitations section which is segregated and an approved part of the manual. The maintenance and operating rules, §§ 43.16, 91.163(c), and other operating rules require compliance with the Airworthiness Limitations Section. Other airworthiness standards were adopted for airplanes, engines, and propellers to similarly require Instructions for Continued Airworthiness and an Airworthiness Limitations Section. See paragraph AC 29.1529 for further information. The limitations placard standard was not changed by this amendment.
(5) Amendment 29-24 adopted a significant change for the placard. The placard must be in clear view of the pilot and must provide a convenient cockpit presentation of the approved types of operation for each aircraft. Other operating and maintenance rules referenced in the previous paragraph provided the basis for much of the change in the placard content.
b. Procedures.
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