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In the US, is it legal to cover up some of the required gyro instruments during flight under IFR in actual IMC?

The purpose being for "partial panel" practice.

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  • $\begingroup$ What makes you think it's illegal @quietflyer? $\endgroup$ – GdD Nov 1 '18 at 11:36
  • $\begingroup$ So the answer is yes, it is legal to cover up some of the gyro instruments during flight under IFR in actual IMC? $\endgroup$ – quiet flyer Nov 1 '18 at 11:40
  • $\begingroup$ @GdD intuitively, there may be restrictions on this; as your own answer notes, it's a spectacularly bad idea. It's a reasonable question. $\endgroup$ – 0xdd Nov 1 '18 at 17:42
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To my knowledge there's nothing illegal about practicing partial panel in real IMC, however it's a spectacularly bad idea to do so. A failure of vacuum instruments in IMC is an emergency because you can easily lose orientation and dig a big hole in the ground. A safety pilot won't be able to help unless they have a separate set of instruments to rely on, and even then upset recovery in IMC is inherently less safe.

If you want to practice partial panel pleeeeease do so in VMC, with a safety pilot.

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    $\begingroup$ Well, obvious bad ideas are illegal by the catch all “careless and reckless” rule. $\endgroup$ – Jan Hudec Nov 1 '18 at 19:43
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    $\begingroup$ @JanHudec - just a small, but important point, FAR 91.13 is "careless OR reckless" not both. Operating with required equipment functionally inoperative likely, in my opinion, would be "reckless" (a different regulatory dimension). $\endgroup$ – 757toga Nov 1 '18 at 22:13
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    $\begingroup$ I have to admit I'm projecting a cockpit where pilot and copilot have two different gyro displays. In this particular case, you need only cover one side. $\endgroup$ – Joshua Nov 1 '18 at 22:42
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    $\begingroup$ Well, the regulation uses the phrasing "careless or reckless", so clearly careless operation is prohibited, and reckless operation is prohibited, and operation which is both careless and reckless is prohibited. Although that would be a pretty hilarious loophole: "What I'm doing is both careless AND reckless, so it's permitted!" (The entire paragraph says: Aircraft operations for the purpose of air navigation. No person may operate an aircraft in a careless or reckless manner so as to endanger the life or property of another.) $\endgroup$ – Terran Swett Nov 2 '18 at 3:09
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    $\begingroup$ @RyanTheLeach - Ok, I accept that. Also, non-compliance of 91.13 will either specifically cite "careless" OR "reckless," depending on the activity giving rise to the violation. Meaning that a specific non-compliant act (for example by a pilot) could not be both "careless" AND "reckless" (it's one or the other). A close reading of court cases involving 91.13 would show you that. Essentially, 91.13 is a rule that classifies a non-compliant act as being "deliberate/willful" (reckless e.g. low flying) or NOT "deliberate/willful" (careless e.g. landing gear up) $\endgroup$ – 757toga Nov 3 '18 at 15:21
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14 CFR 91.205(a) states (emphasis added):

(a) General. Except as provided in paragraphs (c)(3) and (e) of this section, no person may operate a powered civil aircraft with a standard category U.S. airworthiness certificate in any operation described in paragraphs (b) through (f) of this section unless that aircraft contains the instruments and equipment specified in those paragraphs (or FAA-approved equivalents) for that type of operation, and those instruments and items of equipment are in operable condition.

So the question is: if an instrument is covered, then is it "in operable condition"?

My interpretation would be no: if an instrument is covered, then you can't see what it says, so it's not in operable condition. That would mean that, if that instrument is required for flight, then flying with it covered is illegal.

That said, someone might disagree and say that the instrument is in operable condition, because you can simply remove the cover in order to see what it says. I would disagree with that, because a covered instrument clearly does not provide the safety benefits that an uncovered instrument does.

I did a search in the FAA's "Letter of Interpretation" database, and there didn't seem to be any letters about whether or not a covered-up instrument is "in operable condition". So it seems like this question hasn't been legally decided yet.

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    $\begingroup$ I think it would be very much prudent to not fly partial panel in IMC. The line of thought on inoperability of instruments however, when taking it to the extreme, surely means that if an instrument becomes inoperable if you hold something in front of it, unfolding a sectional chart in IMC is a no-go, too... (and you could probably make that point, but it would not be very practical). $\endgroup$ – Cpt Reynolds Nov 1 '18 at 12:57
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    $\begingroup$ Obviously one concern is that an instrument is covered, no one is monitoring it for potential failure-- but this is more an issue of prudence than legality-- thanks for the well-considered answer $\endgroup$ – quiet flyer Nov 1 '18 at 14:43
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    $\begingroup$ @CptReynolds Yeah, that's an interesting point. There's undoubtedly a continuum of "operable" to "inoperable". If an instrument is hidden behind an object for just a brief moment, but you can (and you're intending to) see it again almost immediately, then that's clearly "operable". If an instrument is hidden by a cover that's glued on, so that it would take you several minutes of effort in order to see it, then that's clearly "inoperable". So "operability" must depend on how much effort is required in order to view the instrument. $\endgroup$ – Terran Swett Nov 1 '18 at 15:11
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    $\begingroup$ Regarding "operable condition": if an MFD is operating normally & the instructor turns its brightness to full dim, essentially blanking the display, is it no longer in an "operable condition"? What if he turns it off? Is there no difference between "operable condition" and "operating"? Is a landing light only "operable" when it is turned on & illuminated? $\endgroup$ – Ralph J Nov 1 '18 at 16:51
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    $\begingroup$ Let us continue this discussion in chat. $\endgroup$ – Terran Swett Nov 1 '18 at 16:52
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I'm certain that there will be some disagreement with my answer, but the regulation (FAR 91.205 shown in pertinent part below) is pretty clear to me that you can't legally operate in the manner described by your question.

Specifically if you purposely render a required piece of equipment, such as the attitude indicator, "inoperable" (meaning it no longer functions in the manner for which it was certified ), you will not be in compliance with FAR 91.205.

Imagine flying IMC with the aircraft's artificial horizon and directional gyro [required by FAR 91.205 (d) (8) and (9)] covered up and you are being vectored for final approach with ATC using minimum separation standards between other IFR aircraft (B737 for example) and you have difficulty taking a turn as expected or holding altitude as required. Putting other IFR aircraft at risk while required instruments in your aircraft are rendered "inoperable" on purpose, I believe is contrary to the FARs and certainly good judgement.

§91.205 Powered civil aircraft with standard category U.S. airworthiness certificates: Instrument and equipment requirements.

(a) General. Except as provided in paragraphs (c)(3) and (e) of this section, no person may operate a powered civil aircraft with a standard category U.S. airworthiness certificate in any operation described in paragraphs (b) through (f) of this section unless that aircraft contains the instruments and equipment specified in those paragraphs (or FAA-approved equivalents) for that type of operation, and those instruments and items of equipment are in operable condition.


(d) Instrument flight rules. For IFR flight, the following instruments and equipment are required:

(1) Instruments and equipment specified in paragraph (b) of this section, and, for night flight, instruments and equipment specified in paragraph (c) of this section.

(2) Two-way radio communication and navigation equipment suitable for the route to be flown.

(3) Gyroscopic rate-of-turn indicator, except on the following aircraft:

(i) Airplanes with a third attitude instrument system usable through flight attitudes of 360 degrees of pitch and roll and installed in accordance with the instrument requirements prescribed in §121.305(j) of this chapter; and

(ii) Rotorcraft with a third attitude instrument system usable through flight attitudes of ±80 degrees of pitch and ±120 degrees of roll and installed in accordance with §29.1303(g) of this chapter.

(4) Slip-skid indicator.

(5) Sensitive altimeter adjustable for barometric pressure.

(6) A clock displaying hours, minutes, and seconds with a sweep-second pointer or digital presentation.

(7) Generator or alternator of adequate capacity.

(8) Gyroscopic pitch and bank indicator (artificial horizon).

(9) Gyroscopic direction indicator (directional gyro or equivalent).

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  • $\begingroup$ Your answer seems to address IFR flight (the flight plan) rather than flying in IMC (the conditions). So is partial panel work on a clear day with a safety pilot while on an IFR flightplan prohibited by the sections you cited? Or is that allowed, and there is a distinction between what's allowed for IFR but not IMC? $\endgroup$ – Ralph J Nov 1 '18 at 16:15
  • $\begingroup$ @RalphJ - If you are operating under an "IFR clearance" (operating under Instrument Flight Rules) issued by ATC, 91.205 applies and the required equipment may not be inoperable,per the rule irrespective of the actual weather conditions. $\endgroup$ – 757toga Nov 1 '18 at 16:22
  • $\begingroup$ Is that the generally understood standard among flight instructors & examiners, that partial panel work can only be accomplished during VFR flight? If so, the OP (asking about IFR + IMC) gets the clear "no" before even getting to the 2nd half of the question. But if not (and it is accepted practice to do partial panel work, prudently, on an IFR flightplan in VMC), then one might conclude that the Post-It note does not render an instrument inoperable in the eyes of the FAA. $\endgroup$ – Ralph J Nov 1 '18 at 16:31
  • $\begingroup$ So, would it make a difference as to the legality and/or acceptability of the situation, if the pilot were really, really proficient at partial-panel flying? $\endgroup$ – quiet flyer Nov 1 '18 at 17:11
  • $\begingroup$ Interesting point that the relevant equipment need be "operable" even in VMC, as long as operating under IFR-- $\endgroup$ – quiet flyer Nov 1 '18 at 17:13

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