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Talking about small aircraft here, assuming the pilot is stable and ready to land, they’re flying IFR and the visibility is nonexistent, but that’s alright because he’s currently IFR! But then the vacuum system fails. The pilot loses:

Attitude Indicator

Heading Indicator

Turn Coordinator

With a very poor visibility I can see how this could end up fatal. What is the do’s and don’t here? I can easily see that with every scenario there can be an argument for both “do” and “don’t”. Pilot could go around, but at the same this may not be smart because you don’t know the pitch of the plane, at the same time I see it being okay because you know airspeed.

I can also see a reason to continue on, to try and see if you can visualize the runway and land, seeing you know your altitude, at the same time I can see how that can be disastrous. So what’s the correct way to go about this type of failure in horrible conditions?

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    $\begingroup$ The attitude indicator and turn coordinator you have pictured say either "DC" or "DC Elec" on the face plate, indicating that these specific versions are electrically driven, not vacuum driven. $\endgroup$
    – HiddenWindshield
    Commented Jan 31, 2020 at 17:56
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    $\begingroup$ Loss of electricity in this case, would represent one of the worst scenarios. You could till fly partial panel. You would have to pay close attention to the DG, Altimeter, and VSI. These would have to serve to indicate pitch changes as well as turn and bank. Keep all inputs very minute. Keep all banking very shallow. This would hardly ever be the case since the Attitude Indicator and the Turn Coordinator are usually not on the same power source for the reason of that they both are key to banking information. $\endgroup$
    – Dean F.
    Commented Feb 1, 2020 at 6:46

4 Answers 4

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Your scenario isn't really realistic, the turn coordinator and the AI are almost always on different sources of power to protect against this very event. The TC is almost always electrically driven because it gives an alternate source of information.

A loss of an instrument or even a whole suite of instruments is something instrument rated pilots train for, and should practice once they have their rating. We call it partial panel, where you use your other instruments to make up for the loss. If you lose your vacuum driven instruments you fall back on your electrical and non powered instruments like the altimeter, airspeed gauge, VSI and magnetic compass.

Addressing your question, if I experienced a loss of vacuum on short final when I was established on an instrument approach I would most likely simply continue the approach and land. A loss of vacuum doesn't immediately cause those instruments to keel over and die, they keep working for awhile, getting less accurate as they spin down. Heck, if I'm on a short final I may not even recognize the failure!

If I'm on a longer final and I lose my vacuum powered instruments I would also continue the approach unless there was alternative with better conditions or less hazards nearby. Your vacuum instruments aren't going to fix themselves, so there's no point in flying around waiting for something else to go wrong.

The exact situation you describe in your question would be extremely unusual to say the least, this would most likely be caused by something pretty catastrophic that would mean continuing the approach is impossible. If I had a total powered instrument failure but somehow my ILS and radio stayed up I would continue the approach using the residual momentum of the gyros to keep situational awareness as long as possible, then fall back to my working instruments. I'd also declare an emergency, and ask for ATC to give me surveillance radar data, they can give me a running commentary of which direction I'm turning.

Of course, if it was me I'd activate emergency AI app I have on my tablet GPS or my phone. Both use the phone/tablet sensors to produce a pretty reliable picture.

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GdD’s answer is accurate (up vote). My answer will be more step by step.

  1. The first thing you should do is recognize the issue. That might not be immediately easy depending on your aircraft and it’s electronics suite. If there is no visual and auditory alert, you will have to wait for the gyros to wind down to a certain extent.
  2. Immediately announce to yourself and the rest of the flight crew which instruments are inop. Even solo, you should be talking to yourself out loud. It activates the auditory part of the brains learning and response mechanism. Most of us are a combination of visual, auditory, and kinesthetic.
  3. Cross check your other instruments.
  4. Ignore the inop instruments and utilize your back up instruments.
  5. Stabilize your descent per the IAP.
  6. Declare an emergency. In IMC this is an emergency situation. This should be quick, simple, and to the point. For example, just state, “Mayday! Mayday! Mayday! [callsign] has lost instruments!” Don’t bother going into details at this point. It will just confuse matters. And, you don’t have the time. Plus, not all ATC are pilots. They may not know the significance of partial panel, lost vacuum or lost gyro. Just say “instruments”. ATC might have a lot of questions to ask you about the nature of your emergency. Fly the airplane first. Put your concentration into the approach. Then, talk to ATC. You can sort out the details when you have time. Once the opportunity arises, you can make a proper call like, “[airfield tower or CTAF]. [callsign]. [distance & direction from field]. Inbound on final. I’ve lost primary flight instruments. Landing full stop runway [#]. Declaring an emergency. I need a field advisory.“ The last part is a last minute double check of field conditions, wind, and any other unforeseen issues. Remember, this is under the assumption that you are already on or close to being on final (like on or intercepting the intermediate leg), and have already been making the appropriate radio calls.
  7. Have another crew member cover the inop instruments.
  8. Continue the approach.
  9. If you see the runway, and it’s possible to, LAND.

That last part is a judgement call. The situation will dictate what you do. Some may say only land if you meet all the normal criteria, since a go-around is the default for all descents and approaches. Although this is true, you are in an emergency situation. Land if at all possible. Go missed only if it is not possible to land. For instance, if you are landing a four-seater four-banger on a 10,000 foot runway. And, you are in a position to safely land it on the last quarter of the runway, do so.

Also, Stratus is a great, last ditch, unofficial, non-certified back up. Its AHRS function can be accessed through EFB apps like ForeFlight or through its own proprietary app. Although it can not be used as a source of navigation or instrumentation, it would be better than nothing in a pinch.

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    $\begingroup$ Your second action point is probably one of the most underrated (or maybe even one of the least known) best practises of aviation. Talk to yourself, keep yourself informed. The communicate part of aviate, navigate, communicate also means communicating with yourself. There are huge psychological advantages in announcing your findings and intentions out loud, even if you are by yourself. Silence is not golden in aviation. $\endgroup$
    – Jpe61
    Commented Jan 31, 2020 at 17:59
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    $\begingroup$ Exactly. It activates the auditory part of the brains learning and response mechanism. Most of us are a combination of visual, auditory, and kinesthetic. I added that to my response. $\endgroup$
    – Dean F.
    Commented Jan 31, 2020 at 18:05
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    $\begingroup$ I like this answer best. Key point from the question: "You are stabilized and ready to land" when you go partial panel. This is actually the very best scenario for it to happen! Partial panel sucks. We all practice it, but you want to minimize your exposure. Climbs, turns, speed changes, configuration changes, switching nav equipment, etc. are all things you would prefer to avoid. Just keep the wings level and try to stay on course, watch your VSI and altimeter, and pray you break out... $\endgroup$
    – Michael Hall
    Commented Jan 31, 2020 at 19:53
  • $\begingroup$ Excellent point. Plus, you can ignore your DG and AI if your NavCom (and/or GPS) and Altimeter are working. Your turn coordinator can even be inop (if it is not electrical). Although this increases the complexity and risk exponentially. Although, careful monitoring of your mag Comp can mitigate this. $\endgroup$
    – Dean F.
    Commented Jan 31, 2020 at 20:15
  • $\begingroup$ Partial panel training for me was to have the instructor “fail” the MFD and PFD. This left me with an Electric Attitude Indicator, Altimeter, Airspeed Indicator (some times), Tachometer, Mag Comp, and a Garmin 430W on the Default Nav page (no moving map nor rate-of-turn/turn coordinator). When the instructor would also “fail” my Airspeed Indicator, I would have to rely on the Tach using GPS ground speed as a double check. Training also included all phases of flight as well as upset recovery. Each two hour session would leave me wiped out. $\endgroup$
    – Dean F.
    Commented Jan 31, 2020 at 20:36
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Buy one of the devices that gives you GPS plus AHARS, and make sure that it’s calibrated with ForeFlight and your iPad on EVERY FLIGHT. THen in the bizarre situation that your vacuum AND electric fail simultaneously you can STILL land using just your iPad. Oh... and for sure check this by flying an approach with an instructor and failing ALL instruments to make sure that you can really maintain control in this scenario.

ForeFlight + independent GPS and AHARS is an amazing resource.

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  • $\begingroup$ Yes, Stratus or Sentry. $\endgroup$
    – Dean F.
    Commented Jan 31, 2020 at 20:13
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    $\begingroup$ Yeah, but as per question you'd have to land with partial panel before you can go shopping for pads and stuff. $\endgroup$
    – Jpe61
    Commented Jan 31, 2020 at 22:49
  • $\begingroup$ @Jpe61 I think the idea of the answer is to buy this and have it with you now, before your instruments fail in IMC. :) $\endgroup$
    – reirab
    Commented Feb 2, 2020 at 5:30
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Plus request a "No Gyro" approach from ATC or request vectors to an airport that has that capability if you have fuel to make it there.

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  • $\begingroup$ No-gyro or Radar Approaches are a great tool if you have a loss of instruments. I would hazard against prolonging time in IMC by going to another airport if the one you are at does not have radar capabilities. If you have a working NavCom and/or GPS you should be able to shoot an approach just as well with only those and an altimeter. The more time you spend in IMC going to another airport is more time to lose spatial orientation. Use No-gyro only as a last resort in case you have no navigational ability or equipment at all. $\endgroup$
    – Dean F.
    Commented Feb 1, 2020 at 5:48

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