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Standby Attitude Indicator ILS

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Standby Attitude Indicator ILS

Old 10th Jun 2021, 19:40
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Standby Attitude Indicator ILS

Hello Gents, are standby attitude indicators on transport category jet aircraft in FAA land required to have an ILS presentation on the actual instrument itself?
The ability to navigate an ILS with nothing but standby instruments? Aircraft in question is B737 Classic.
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Old 10th Jun 2021, 20:40
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I am not aware of any requirement to have any sort of standby ILS indicator. Acceptable redundancy is typically provided by independent left and right side instruments, radios, and associated source selection capability. I don't recall that any of the part 25 aircraft I worked on had a standby display of ILS Loc and GS deviation.
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Old 10th Jun 2021, 21:19
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All the bizz jets I’ve operated have selectable ILS indications on their IESI.
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Old 11th Jun 2021, 06:04
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If memory serves, the classics I flew had ILS F/Ds that were selectable on the standby att inds. Supposed it may have been down to customer options.
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Old 11th Jun 2021, 10:31
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Ours had the LLZ and GP needles (not FD's). Ex-Sabena ships, all mechanical. Both steam-gauge and EIS configured.

Last edited by FlightDetent; 11th Jun 2021 at 12:22.
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Old 11th Jun 2021, 10:58
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Back when the 737 classic was introduced there were no electronic primary or standby instruments. The standby instruments in those days were typically a mechanical attitude indicator and a separate IAS/Altitude indicator. The same was true when the MD-11 was introduced. At that time Honeywell and DAC believed there was so much system redundancy that no standby instruments were required. In all the Honewell advanced flight decks a PFD and Engine display remain after failure of any 4 of the 6 display units. Standby instruments were fitted because that was easier than arguing with FAA that they were not required.

Modern electronic standby instruments have much more capability but there is a difference between capability and a requirement to have that capability.
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Old 11th Jun 2021, 14:18
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LLZ and GP needles…

However you call them, they had similar functions, did they not? Terminology.
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Old 11th Jun 2021, 14:32
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Different names because of different features.

FYI the standard ILS minima w/FDs are 550 m, but 720 with the ILS raw indicators.
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Old 11th Jun 2021, 15:23
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Please enlighten me….

“Flight director,” I always thought, was a term primarily associated with the function served. There have been many different types. Mechanical, later LED types. But as far as I could see, they served the same function. If one went below the glide slope, the “whatever you want to call it” went up, “directing” one to “fly” up. Same for going high on the glide, or left or right from the localizer. Some had a switch that could operate BC. Seldom used. One could turn them on or off. One could forget and leave them on. I have never seen one do much more than that.

So, what other grand features did these other marvelous technological wonders have or, as you write, what other “vastly different features” did I miss?

Did they make coffee?

as for how low minima they would permit, nothing changed their function as a “flight director.”

and to confirm we are talking standby attitude indicators. Oops, there’s another one of those ‘function’ words that include lots of different types.
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Old 11th Jun 2021, 18:02
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The OP asked about standby instruments equipped (or not) with ILS indication. I flew one, shared it.

Someone says they had an FD setup, which is not the same on the instrument level. Since we're talking about standby attitude indicators and their add-ons, it seems relevant. You surely know the difference better than I could explain.

To get a standby instrument equipped with predictive steering commands would be a nice engineering trick, yet there must be a reason no one ever installed any such thing.
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Old 11th Jun 2021, 18:09
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Originally Posted by 70 Mustang View Post
However you call them, they had similar functions, did they not? Terminology.
A "director" is a indication of the required correction and to be followed by whoever is in control.

A "deviation indicator" is an indication of the deviation in a certain point and time and has nothing to do with the correction required. Depending on situation the required correction could be big or small.

They have far from similar functions.

From memory (some can confirm or correct): on B737 classic non efis the standby attitude indicator had standard ILS deviation indicators (NAV 1). The B737 classis EFIS has standard ILS deviation indicators on the standby (NAV 1) if the captain EFIS is not connected to standby power. The B737 classic EFIS with captain EFIS on standby power has standby attitude indicators with the ILS deviation indicators (NAV 1) as an option.

Some people actually like this as the standby deviation indicators had a tendency to "come alive" slightly earlier than on the EFIS which sometimes helped to anticipate the turn on the localiser in raw data flying.
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Old 11th Jun 2021, 18:32
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The standby instruments shown in this image look similar to the ones used by Douglas. Does the pictured standby attitude indicator display GS and LOC dev? I see no scales, pointers, or flags.

http://www.b737.org.uk/images/centrepanel.jpg
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Old 11th Jun 2021, 19:44
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In my old paper FCOM of the classic it shows the standby horizon with an approach mode selector (customer option) which was a three position switch with OFF, ILS, B/CRS as available options. In ILS mode it would show the GS and LOC pointer in front of the horizon ball and aircraft symbol. Not a FD, just a normal ILS cross pointer. And a LOC and G/S flag in case either of those did not work or receive. It worked solely off the No. 1 ILS receiver.
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Old 11th Jun 2021, 22:59
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70 Mustang

Glideslope and localizer, aka "raw data." They show only your angular deviations from the horizontal and vertical perfect positions. If you're right of course see a "fly left" needle, it's up to you to turn left just the right amount, then level the wings, then turn right at just the right time and just the right amount, so you re-intercept the course without blowing through it. If you see "fly left" and simply turn left until it's centered, you're virtually guaranteed to blow left through the course at a severe angle. Shown as a pair of needles over the DG on old simple planes (think 1970's 172), or (on a HSI) the middle split out part of the course needle (for the localizer, same as the VOR course function) and diamond or triangle on one (or both) side(s) moving up and down (for the glideslope.) On standby ADI's that have it, pair of needles over the standby ADI. Probably never over a main ADI.

Flight Director. Tells you to fly left/right, or up/down, but with none of the planning and finesse required by the raw data. The computer does your thinking for you. If you're right of course and see a "fly left," you can follow it stupid as a monkey, and it will show a fly-left to guide you into the initial left bank, then show centered when you should level your wings, and show a fly-right to guide you into a bank to the right to make a perfect intercept. Shown as either a pair of needles, or an upside down V shape for you to slot a triangle into, over the main ADI. Probably never in the history of aviation shown over a standby ADI.
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Old 12th Jun 2021, 09:28
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Originally Posted by EXDAC View Post
The standby instruments shown in this image look similar to the ones used by Douglas. Does the pictured standby attitude indicator display GS and LOC dev? I see no scales, pointers, or flags.

http://www.b737.org.uk/images/centrepanel.jpg
As mentioned before, in this case, in flight with loss of both engine driven generators (so automatic revertion to standby power), the captain would retain his EFIS indications so there is no need for a NAV 1 indication. It is an option.
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Old 12th Jun 2021, 12:58
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Keep in mind the original purpose of the standby ADI was specifically to be the "Umpire." In other words,if one of the two normal ADI's failed or gave suspected erroneous attitude information, an instant time critical comparison was readily available between the standby ADI and the two normal ADI's. In turn, this hopefully would confirm which of the normal ADI's was suspect. Two against one.
Later, adding ILS information to the Standby ADI was icing on the cake. As BraceBrace has mentioned in his post, the earlier first inbound movement of the Localiser on the Standby compared to the old fashioned HSI display and associated FD on the main ADI's was a useful hint that you were closing in on the Localiser.

With loss of all generators in some of the 737 Classics, and thus loss of power to both normal ADI's, that left the pilot with (among other instruments) only the standby ADI which worked off the aircraft battery. That had 30 minutes if you were lucky. Instrument flying using only the Standby ADI really sorted the men from the boys. A skill now universally lost forever for some pilots.
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