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First X-Country Solo – Can an Attitude Indicator give such a false reading?

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Aircraft Systems, Flight Instructor, General Aviation, Student Pilot

Type: C172S - Student Pilot 53hrs, 5hrs solo

Departed 33L at Islip and began a right turn to the East once directed by NY Departure. When I finished my turn, on my climb-out to 5,500 passing 3,000 I was wings level and straight flight with a 700fpm climb - I went for a brief scan of the 6pack and noticed that my attitude indicator was showing a right turn at about 30degree bank. This threw me well off as I looked back out the window and confirmed my plane was in wings level attitude. I quickly glanced over at the suction gauge and saw it reading right on the edge of the green arc, towards 5.5Hg. I gave it 3-4 min and the attitude indicator continued to show a right turn 30degrees in addition to the suction gauge showing its needle at the edge of the green arc.

I decided to return to the field and land as I still had 2hrs of flight for my cross-country to Groton, CT and back home. I was nervous that these may have been early signs of a vacuum pump failure or hiccup (even though no lights illuminated on the Annunciator Panel). The attitude indicator continued to show erroneous bearings until just on short final, it began to readjust and behave normally. My DG was acting normal the whole time.

Some of my instructors mentioned that I "could have continued, we've seen it before on that plane sometimes, but you did the right thing no question about it". 

My Question: I simply want to understand, from a broad audience of the aviation community - is it possible to have an attitude indicator give you such a false reading without the vacuum pump failing? I keep beating myself up about turning back, but on my first cross country, with such an instrument giving that false reading, I was not comfortable to continue.

Thanks,

Mark

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1 Answers



  1. Russ Roslewski on Apr 23, 2018

    “is it possible to have an attitude indicator give you such a false reading without the vacuum pump failing?”

    Of course. The attitude indicator itself can fail. This is not an uncommon event. The bearings get old, it takes longer to spin up and self-correct, etc. Likely the AI should be repaired or replaced if it has done this before.

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