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Old 28th Sep 2013, 22:16   #1 (permalink)
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When was the artificial horizon first required for IMC?

Does anyone have an easy way to peruse old FAA / CAA regs?

I'd like to know when, exactly, the artificial horizon or attitude indicator first became a required instrument for cloud flying in the United States. Surely well after WW2, no?

Did it become required for, say, airline transport or commercial flying in clouds before it was required for private flying in clouds?

Did it become required for cloud flying in gliders at the same time as it became required for cloud flying in airplanes?

(I know cloud flying in gliders is rare, but still the question must have an answer.)

But for starters I mainly just want to point down when this instrument was first required by the CAA or FAA for cloud flying in airplanes. If you have old copies of the FAR's / CAA reg that would shed light on this I'd love to hear.

Maybe we can pin it down by a process of elimination-- what is the earliest published material anyone has seen that lists this instrument as a required instrument for civilian blind flying in the US? What is this latest published material anyone has seen that does not list this instrument as a required instrument?

For that manner, when did the concept of flight by "Instrument Flight Rules" under formal control from the ground, versus VFR, first arise?


Last edited by flyer101flyer; 29th Sep 2013 at 05:58.
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Old 29th Sep 2013, 19:49   #2 (permalink)
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I did some research with google and have found the following--

In relation to the requirement for attitude indicators for cloud flying in powered light aircraft, the answer appears to be "1956".

See: (quoting)



This amendment includes a substantive change which requires an artificial-horizon and a directional gyro as additional instruments for IFR flight operations. This additional equipment is made mandatory because flight tests on small aircraft have shown that safe instrument flight without such equipment is extremely difficult under rough air conditions.

Interested persons have been afforded an opportunity to participate 1/ in the making of this amendment, and due consideration has been given to all relevant matter presented.

In consideration of the foregoing, the Civil Aeronautics Board hereby amends Part 43 of the Civil Air Regulations (14 CFR Part 43, as amended) effective August 1, 1956:

By amending 43.30 by adding a new note after the introductory paragraph and by adding new subparagraphs (8) and (9) to paragraph (c) to read as follows:

43.30 Instruments and equipment for NC powered aircraft or powered aircraft with standard airworthiness certificates.
NOTE: Instrument and equipment installations are required to comply with the applicable airworthiness parts of the Civil Air Regulations.

Instrument flight rules.

Gyroscopic bank and pitch indicator (artificial-horizon).

Gyroscopic direction indicator (directional gyro or equivalent).

(end quote)


section 43
amendment 43-1

However, attitude indicators were already required for all "air carrier" operations. For example amendment 04b-6, dated 1947, rescinds a requirement for a "nonupsetting type gyroscopic bank and pitch indicator", noting that "Service experience with instruments of this type has not been sufficiently extensive to warrant a requirement that this type be installed to the exclusion of other types which, while not completely upsetting, have shown satisfactory service characteristics over a long period of time. It appears, therefore, that safety would be served equally well if instruments which are currently used in airplanes certificated under other airworthiness parts of the Ci vil Air Regulations are allowed to be used for the present."

(source-- link as above, section o4, amendment 04-b6)

Steve S
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Old 30th Sep 2013, 16:02   #3 (permalink)
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Steve IFR has nothing to do with "formal control from the ground".

IFR, Instrument Flight Rules are related to flight without visible reference to the ground.

Air Traffic Control should not be confused with Instrument Flight.
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Old 1st Oct 2013, 23:27   #4 (permalink)
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Thanks for the comprehensive note.


"One early explicit mention is the May1938 CAR 4.532 (b), meant as a certification requirement for ACP (air carrier planes),
"a gyroscopic instrument showing bank and pitch". "

Also, regarding gliders, it now appears to me that there is even today NO explicit requirement for any particular list of instruments to be carried in gliders for flight in IMC or during IFR operations.

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Old 2nd Oct 2013, 01:33   #5 (permalink)
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attitude indicator requirements

Re "formal control from the ground": I guess what I meant was when did we first start having the concept of "controlled airspace", which pilots could not legally enter under IMC conditions without communicating with air traffic control.

Really though the main thrust of my question is when did an attitude indicator become required in various situations involving legal flight into IMC, in the United States. As noted above the best answer known so far appears to be

* "still not required" for gliders

* "in 1956" for powered light aircraft not engaged in air carrier operations,

* "by Nov 1 1937 if not sooner" for "Air Carrier Passenger" aircraft involved in "instrument day flying" -- see section 04.532 of the 11/1/37 CAR regs-- this is the earliest edition I've yet found of the regs and the same may have existed sooner.

( http://ntl1.specialcollection.net/sc...%5CCAR0437.PDF )

* by 04/07/50 there appears to have been still no blanket requirement for all aircraft involved in air carrier operations, including day and night visual operations, to have an attitude indicator or gyroscopic bank and pitch indicator. I have no idea whether this is still true today-- the modern regs are too complex to wade through...

(see parts 4a.457 through 4a.550 in
http://ntl1.specialcollection.net/sc...H%5CCAR450.PDF )

However, well before this time it appears that the "Transport Category" had been established, with more restrictive requirements, including at some point during or before 1947, a requirement for a gyroscopic bank and pitch indicator, without regard to whether operations were visual or instrument. Despite the specific reference to "Air Carrier", it appears that the text below from amendment 04-b6 from 8-19-47 actually applies to this "Transport Category". (Yes, it seems that the regs were already confusing by this time!)

(Begin quote: )

"CAR Amendment 04-b6. Air Carrier bank and pitch indicator. Part 04b of the Civil Air Regulations currently requires under 04b.51 (a) (5) that all airplanes subject to certification under this part be equipped with a nonupsetting type gyroscopic bank and pitch indicator. Service experience with instruments of this type has not been sufficiently extensive to warrant a requirement that this type be installed to the exclusion of other types which, while not completely upsetting, have shown satisfactory service characteristics over a long period of time. It appears, therefore, that safety would be served equally well if instruments which are currently used in airplanes certificated under other airworthiness parts of the Civil Air Regulations are allowed to be used for the present.

Interested persons have been afforded an opportunity to participate in the making of this amendment, and full consideration has been given to all relevant matters presented. Since this is an amendment relieving restriction, good cause exists for making it effective without delay.

Pursuant to the Civil Aeronautics Act of 1938, as amended, particularly 205 (a), 601, and 603 thereof, the Civil Aeronautics Board hereby amends 04b.51 (a) (5) of the Civil Air Regulations (14 CFR, 04b.51 (a) (5) as amended), as follows:

Effective August 19, 1947, 04b.51 (a) (5) is amended by deleting therefrom the words "(non-upsetting type)".

(End quote)

(Source: http://ntl1.specialcollection.net/sc...H%5CCAR4B6.PDF )

As best as I can guess, this referred to aircraft covered by part 04b of the CAR's, which presumably were the "Airplane Airworthiness Transport Category" regulations, and apparently already existed in 1947. Clearly this is a category more restrictive than the "Air Carrier" operations described by parts 4a.457 through 4a.550 of the 04/07/50 regulations described above.

At present the earliest edition I've found of the complete regs of part 04b, the "Airplane Airworthiness Transport Category" regulations, is 12/31/53-- see below.

By 12/31/53 the regulations for "Airplane Airworthiness Transport Category" specified a gyroscopic pitch and bank indicator, without regard to the type of operations to be conducted (see 4b.603 in http://ntl1.specialcollection.net/sc...CH%5CCAR4b.PDF )

But as noted above it appears that similar regulations were in effect at least as early as 1947; I just haven't seen a copy of part 04b from before 1953.

Steve S

Last edited by flyer101flyer; 2nd Oct 2013 at 14:31.
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Old 2nd Oct 2013, 02:58   #6 (permalink)
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A few other random notes-- Doolittle, Lindbergh

A few random notes re blind flying, Doolittle, and Lindbergh:

* Jimmy Doolittle's contributions to blind flying are well known. A quote from wikipedia:

"In 1929, he became the first pilot to take off, fly and land an airplane using instruments alone, without a view outside the cockpit. Having returned to Mitchel Field that September, he assisted in the development of fog flying equipment. He helped develop, and was then the first to test, the now universally used artificial horizon and directional gyroscope. He attracted wide newspaper attention with this feat of "blind" flying and later received the Harmon Trophy for conducting the experiments. These accomplishments made all-weather airline operations practical."

Photo of the instrument panel of the aircraft used in these tests:


What are all the instruments? Note the artificial horizon. Where is the directional gyro? Presumably the instrument above the panel is a second wet compass? Note the off-course deviation indicator for the "Pioneer compass" in the bottom center of the panel-- this was not a gyro instrument-- more about the "Pioneer compass" below, re Lindbergh. The dial in the upper right of the panel, right of the wet compass, may be for setting the desired course on the Pioneer compass? The octagonal display on the far lower left, below the panel, was the vibrating reed localizer.

This article suggests that contrary to most accounts, there actually was no directional gyro installed during the famous flight where Doolittle was under the hood from takeoff to landing: (see figure 3 and the text immediately above.)

Milestone-Proposal:First Blind Flight: A Joint IEEE-AIAA Milestone Proposal - GHN: IEEE Global History Network


* Lindbergh engaged in extensive blind flying in his famous trans-Atlantic flight 1927. Blind flying was not unknown at this time, but was not fully developed either. Here is a photo of his panel:

Spirit of St Louis Photos

another view 001011 ? Complete View of Instrument Panel | Orbital Air, Inc.

and another view:

Instrument panel for Spirit of St. Louis | Flickr - Photo Sharing!

Clearer view, on a "restoration", (should be "replica"?) : Spirit of St. Louis instrument panel photo - Bill Chilcoat photos at pbase.com

The turn rate indicator is the only gyro instrument on the panel.

Note that there is not one slip/ skid instrument but two. A ball and a bubble. They give the same information, just to different scales. Note also the pitch trim level. This would only be useful for trimming the aircraft in un-accelerated flight.

The instrument labelled "Pioneer Compass", directly above the needle-and-ball, is the off-course deviation indicator from Lindbergh's Pioneer earth-inductor compass. This is a non-gyroscopic instrument that gives superior performance to a conventional wet compass. The left-right indication is the deviation from the set course. I'm not sure where the dial for setting the course is.

Read more about the Pioneer Compass here:

Atlantic Fever: Lindbergh, His Competitors, and the Race to Cross the Atlantic - Joe Jackson - Google Books

and more here:

Plane Talking - HyperScale's Aircraft Scale Model Discussion Forum: earth inductor compass explanation for those interested

There was also a wet compass that was installed over Lindbergh's head, and read through a small mirror on the upper left part of the control panel. Read more about it here:

Charles Lindbergh Discussion Center: Spirit of St Louis Compass


Here's some amusing reading re blind flying around 1930:

Happy Birthday, Blind Flight! [Vintage PopSci] | Popular Science

Here's an interesting thing to skim through-- a 1938 bibliography on air navigation instruments. Includes references to many kinds of compasses. Start by taking a look at section 4 in the Table of contents (page 4 in the PDF).


Ok that's enough for now! Steve S
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Old 3rd Oct 2013, 05:50   #7 (permalink)
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I find the standard layout interesting. (Yes, I'm really that dull!) The RAF standard panel was the first serious attempt to improve the standards of IF and all RAF aircraft in WW2 had the same layout - the advantage being that the selective radial scan led to more effective and accurate flying with the scan centered on the central AI and that pilots could transition from type to type with few problems. American aircraft through WW2 had the instruments seemingly placed at random.

The standard T pattern arrived in the mid 1950s, probably because it was a more logical pattern which made the scan easier. The peason for having the Alt, DI and VSI on the bottom in the original panel was that the early AI's used to topple easily and the scan without it was effective using the DI as the central reference with the Alt and VSI either side. The Sperry Mk1a used to topple at about 50 degrees of pitch and 85 degrees of roll and no fast erect function. Once toppled, they took up to 15 miuntes to re-errect, so after any manoevreing, limited panel flying skills were a definite advantage. AIs with better limits meant the panel could be improved to the T.
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Old 3rd Oct 2013, 17:17   #8 (permalink)
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panels and compasses

Dan-- Re the reference to the bottom row containing the altimeter, the heading indicator, and the vertical speed indicator, are you perhaps mistaken? The arrangement appears to be--

Original RAF standard panel:
top row : airspeed indicator, attitude indicator, vertical speed indicator
bottom row: altimeter, heading indicator, turn and slip indicator

(As you noted this does appear to group the most important instruments together on the bottom row for easy use in case the AI tumbles )

Modern "T" panel:
top row: airspeed indicator, attitude indicator, altimeter
bottom row: turn coordinator or turn and slip indicator, heading indicator, vertical speed indicator

Image of modern "t" panel: http://upload.wikimedia.org/wikipedi...nstruments.JPG

Images of the original "RAF standard panel":

WWII British Aircraft cockpits........

(note-- *source and cockpit photos taken from “Cockpit- an illustrated History of World War II aircraft interiors”." )

All except the Fairey Swordfish (second from top) show the "RAF standard panel"

The quote near the bottom of the post is interesting-- "All the instruments on the blind flying panel are vacuum powered from a vacuum pump fitted on one of the engines, making the instruments independent of the electrical supply"

The mounting of the compass of the Fairey Swordfish (second from top) at the top of the panel, to be read by a mirror, is interesting too.

Note that this type of compass which is read over-the-top, i.e. forward or nose-wise of the pivot, is more intuitive to use than a front-reading compass-- "W" lies to the right of "S" as it does in the real world, etc, and the heading numbers increase as you look clockwise or left-to-right around the dial, as they should.

A vertical-card DG or DI is more intuitive to read than the front-reading type, for the same reason. Likewise a vertical-card compass vs a more conventional compass.

To gain the same intuitive benefit for emergency cloud-flying in a plane with rather rudimentary instrumentation, another alternative to a vertical-card compass is an over-the-top-reading compass such as this one. Ritchie XP-98W X-Port Tactician Surface Mount Compass

But, awkward to mount, needs to go on top of the panel, or if that's too high, maybe on a little shelf somewhere-- you probably don't want to be looking down at the floor in this type of situation...


Last edited by flyer101flyer; 3rd Oct 2013 at 19:23.
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Old 9th Oct 2013, 14:19   #9 (permalink)
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Yes Flyer, you are correct. I was writing from memory and using one of these panels for the last time in 1993.
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Old 10th Oct 2013, 05:29   #10 (permalink)
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No sweat, thanks for chiming in...

Continuing to "drift" off topic...

Lately I've been noticing how nice it is to have a real, physical directional gyro in plain view for somewhat-challenging-or-marginal VFR ops such as nighttime or whatever...

Sure, get your track established with the aid of the GPS or whatever, but once everthing is hunky-dory, set the DG to a good round number and just follow it for a while... beats looking at an electronic screen any day...

Especially at night, to save your night vision it's nice to dial down the red illumination lights to where you can just make out the marks on the DG and other steam-gauge instruments and not have some electronic screen glaring you in the face...


Last edited by flyer101flyer; 10th Oct 2013 at 05:34.
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Old 15th Oct 2013, 16:29   #11 (permalink)
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a question to B733, Europe Airpost, 2May09


I am not a pilot but interested in aviation. I have a question about B733, Europe Airpost, 2May09, approach to Antalya. You wrote, that the bank angle during the upset was 102° (and so it is also written in BEA report). Do I understand right, that woukd mean that the passengers were placed not only rectangular to the surface of the earth but even beginning to lie head-first (upsight down)?

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