Partial panel

attitude indicator

I had my first experience flying partial panel in IMC on Monday, coming home from Boston. It wasn’t the classic partial panel — a vacuum failure — but a failure of the attitude indicator instrument itself, followed by the airspeed indicator while I was on an ILS approach. The AI had been sluggish for a while, but I had told myself that it was still usable as long as I allowed for a few seconds’ lag. In IMC and moderate turbulence (with a bit of light icing to distract me), however, it was totally useless, and I ended up relying on the turn coordinator to keep the wings more-or-less level, with the heading indicator as a backup.

I’ve heard that partial panel in a slick plane with retractable gear can be a nightmare, but the Cherokee is so slow, draggy, and spiral-resistant that it wasn’t more than an irritant. I’m not sure that simulated partial panel under the hood does anything to prepare you for it, though, because the hardest part is recognizing that you have a problem in the first place (I’m also not convinced that flying under a hood does much to prepare you for flying in actual IMC, but that’s another posting.)

Losing the ASI wasn’t a big deal, since I was already on the glideslope and had a 10,000 ft runway ahead of me, so I just kept a generous power setting on the tachometer and burned off the extra speed in a long flare.

The plane is grounded until the pitot system is cleaned out and tested, the AI is fully overhauled, and new wiring is installed for the intermittent landing light.

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About David Megginson

Scholar, tech guy, Canuck, open-source/data/information zealot, urban pedestrian, language geek, tea drinker, pater familias, red tory, amateur musician, private pilot.
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3 Responses to Partial panel

  1. Viennatech says:

    Good to hear you got it down in proper order David! Have to love those long runways back at your old stomping grounds. I spent about 1 hour yesterday under the hood in CAVU skies. It seems that the nicer it is outside, the more apt the instructor will be to ask you to don the jepp goggles! No failures on my flight, but that was probably a good thing as my performance was rusty. Good luck on your demo tonight. TTYS

  2. flight delay says:

    Isn’t it nice how much easier partial panel is when you actually have a heading indicator too? That goes a long way to keeping control of the airplane when you lose the main focus of your scan (the AI). Nice work.

  3. Sam Weigel says:

    I lost an electric AI in almost the exact same way you did, in an Arrow, in IMC…and then lost the turn coordinator several minutes later. At the time I thought electrical emergency, but didn’t lose anything else and it turned out to be a crazy coincidence. Losing the AI and TC together was enough…holding the wings level by reference to heading indicator alone wasn’t very fun. Fortunately only had to do it for about 10 minutes until I was over lower terrain & could get a descent below cloud bases.

    Good job with the partial panel. It’s something most people don’t practice enough once they get the IR.

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