Backup Flight Instruments: They Stand up When Standards Stand Down
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PILOT’S GUIDE A Buyer’s Guide: Standalone Instruments Backup Flight Instruments: They Stand Up When Standards Stand Down By Dave Hig D o n ost pilots remember sig- curs: For pilots in IMC, loss of the atic spinning-iron gyros and suc- nificant events in their AI, for whatever cause, too often tion pumps. Mflying lives: their first solo; results in an unhappy outcome. Still, the Federal Aviation their first cross-country flight; The odds-on favorite for such a Administration requires modern check rides; and flights significant problem is the dry-air vacuum digital electronic panels to employ because they don’t fit the desir- pump dominant among aircraft a backup set of instruments able description of “uneventful.” suction systems. — often a compact, but old style, A newly minted instrument The related parallel failure of spinning-mass attitude indicator, pilot’s first trip in actual instrument the directional gyro (DG) adds to plus an airspeed indicator and meteorological conditions (IMC) the pressure of partial-panel fly- altimeter. Typically, the standby usually stays with him. And few ing in IMC. The single-point loss AI is electric and the aircraft events imprint as strongly as the of the DG, in contrast, doesn’t sports a secondary source of first time a primary instrument threaten attitude control to the electrical power. fails while flying inside the egg- degree of a loss of attitude indi- Owners of older aircraft have shell. Flying IMC, pretty much any cation; ditto for the turn direction options for adding attitude-indica- failure of a primary system or pri- and rate information delivered by tion redundancy to their panels, mary instrument makes the flight the electrically driven turn gyro, regardless of whether it’s a stan- “eventful.” whether a turn coordinator or turn dard six-pack panel, all glass or a Instrument pilots learn to use indicator. hybrid of glass and analog. the so-called “standard six-pack” Outside the ultimate IMC failure For the instrument pilot, incor- of instruments dominant in our crisis, that of an engine, no other porating standby instruments can predominantly analog panels component loss stresses pilot- help ensure an instrument failure — three of them gyro indicators ing skills and compounds the risk in IMC remains validly described — to successfully execute instru- equation of instrument flight like as “uneventful.” Several manu- ment flight. the loss of attitude indication in facturers offer standby instrument Most of our success hinges on IMC or, a close second, in night equipment created to relieve at our ability to become competent VMC. least the stress of an instrument by trusting a mechanical attitude failure. indicator (AI) in defiance of and Partial Panel: Some pilots opt to add a sec- ignoring completely the attitude Points for Difficulty ondary suction source to their air- indications of our inner-ear mech- One of the benefits of modern plane, a relatively low-cost option anisms. Loss of this AI, the most glass cockpits spins off, if you offering the dual benefit of keep- primary of our primary instrument will, from the shift to solid-state, ing the DG and the AI functioning. flight tools, greatly challenges our no-moving-parts sensors and Many pilots have added both a odds of success in IMC. electronic displays with miniscule secondary suction source and The track record from both real failure rates. These technologies a secondary, standby electricity life and objective research con- allow the elimination of problem- source to provide maximum sys- - 46 - P ilot ’ S G One of the benefits of modern glass cockpits spins off, if you A Buyer’s Guide: Standalone Instruments uide will, from the shift to solid-state, no-moving-parts sensors and electronic displays with miniscule failure rates. tem redundancy to their cockpits. driven AI a minor change — but power to maintain the integral But only a secondary indicator of it’s a minor piece of work with a battery’s charge. For standby attitude information can give an huge implication for the instrument instruments lacking the ability to instrument pilot the fullest hedge pilot facing the failure of a primary self-power, be sure you either against the possibly catastrophic AI. can shed load to keep the instru- outcome of a primary AI failure. The cockpit also must have an ment running until you’re down or In recognizing the lower prior- inclinometer — the trusty old slip/ that it’s on a standby buss to give ity of turn gyros in the instrument skid ball — to comply with the AC. it power priority. And don’t let a cockpit, the FAA issued Advisory By adding a second, alterna- shortage of mounting space hold Circular 91-75 several years ago tively powered AI — regardless of you back. to make adding redundant atti- whether or not it replaces a turn The industry has advisory tude indication easier than ever. gyro — the pilot essentially keeps circular AC 91-75, in large part, In essence, according to AC a full panel to work with in instru- because of the long-term efforts of 91-75, aircraft weighing no more ment conditions. Sporty’s founder Hal Shevers. He than 12,500 pounds, use a sec- Some important issues require petitioned the FAA for nearly two ond AI in place of a turn gyro, consideration when planning an decades to allow replacement of either an AI powered electrically upgrade to add standby instru- the turn coordinator with a backup or an air-powered unit with an ments to the panel. One of the pri- electric attitude indicator. available standby suction source mary considerations is, whenever In 2003, Shevers’ efforts finally — not as appealing a change as adding an instrument or system bore fruit with the issuance of AC going to an electric secondary AI. that increases electrical need, be 91-75, which in turn makes find- sure your generating system can ing space for a backup AI as easy StanDing By with meet this need. as replacing the turn coordinator Standby inStrumentS Independent power for standby or moving it to another location, In this “Buyer’s Guide,” we instruments provides the greatest allowing for a much safer panel examine equipment designed pri- redundancy, allowing the instru- layout in case of vacuum failure or marily to serve in a backup role ment or box to function for some failure of the primary AI. in today’s general aviation panel. limited time in the event of an Shevers’ efforts also helped In some cases, the products electrical-system failure — this is launch production of an electric described can serve as the pri- time a pilot needs to either find attitude indicator with inclinom- mary, allowing the aircraft owner visual conditions or on the ground eter, which was redesigned with to move older instruments else- as quickly as possible using the improvements and helped drive where in the panel and adding a nearest practical instrument- development of other standby layer of redundancy differently. approach option. products. Because turn gyros typically Even with its own standalone employ electric power, AC 91-75 power source, a self-powering makes swapping in an electrically standby device still needs ship’s Continued on following page… - 47 - STANDALONE INSTRUMENTS And company elements now Continued from page 47 incorporated into L-3 long have offered some of the industry stan- dards in standby instruments: J.E.T. standby AIs; AIM Gyros; and the GH-3000 series for busi- ness-turbine aircraft. Kelly manufaCturing Co. rC allen rCa 2600 CaStleBerry Digital horizon inStrumentS Introduced in April 2009 dur- model 300-14el ing the annual AEA International This is the attitude indicator Convention & Trade Show, this Sporty’s revived in Hal Shevers’ brand-new, digital-display horizon/ quest to convince the FAA that an attitude indicator allows the addi- electric AI was a safer choice than tion of an optional inclinometer, the turn coordinator found in stan- making it a candidate to replace trilogy eSi-1000 dard IFR panels. a turn gyro to serve as an electric L-3’s Trilogy ESI-1000, the first After the issuance of the AC, backup unit to a standard suction- solid-state integrated standby Shevers found no competitively powered AI. system created specifically for priced, high-value options that Designed around an all-solid- Part 23 aircraft, is designed as a would convince pilots to make the state digital sensor system, the backup for glass cockpit avionics. safer choice. RCA 2600 fits in the same stan- So complete in its capabilities, After combing the manufacturing dard 3-inch opening, or in a small- it’s easy to imagine some aircraft community with his specifications er opening for the 2-inch model. owners considering the Trilogy for and committing the marketing The RCA 2600 works on any a compact conversion to a glass power of Sporty’s, Shevers con- voltage from 9 to 32, and it draws primary flight display — defined vinced Castleberry Instruments a fraction of the current required these days as an electronic sys- to update and produce this AI. for conventional spinning-mass tem essentially serving to provide Sporty’s initial commitment was for electric gyros. all the information of the entire 1,000 units, which sold out almost Kelly’s newest RC Allen AI also standard six-pack in an IFR panel. immediately. weighs a fraction of a traditional The name, Trilogy, comes from Castleberry found the enterprise electric gyro, at 16 ounces for the the instrument’s integration of all launch profitable enough to con- 3-inch and 8.5 ounces for the 2- three functions the FAA requires tinue building the 300-14EL as a inch.