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5 Answers

GPS LPV approaches and STec 20/30

Asked by: 1824 views
Aircraft Systems, Instrument Rating

I am going to fly a cross country in an airplane equipped with an STec 20/30. I am used to GFC 500 and STec 55x. I anticipate flying an instrument approach in IMC at my destination and would prefer to use the AP to reduce my workload. However, I am proficient and current in hand flying approaches.

The manual for the 20/30 states to couple the AP to the navigator and set it in Hi Trk mode which is simple enough. In this configuration, will I be able to deselect the altitude hold so I have pitch control of the airplane for my descent? Or will my pitch get locked as it does with some other autopilots?

5 Answers



  1. Mark Kolber on May 16, 2024

    Yes. With no ability to fly a vertical path, once altitude hold is off in the 30, it’s just a basic single-axis AP (like the 20). The AP flies the lateral and the pilot flies the vertical. (I assume you know the difference between HI and LO TRK.)

    I’m curious about one thing, though. You mentioned pitch being locked like some autopilots. I don’t think I’ve seen an autopilot that cannot fly a vertical path at all locking pitch. What have you seen?

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  2. John D Collins on May 16, 2024

    Mark,

    He may be referring to the Stec 60-2 or 55 series. Once a pitch axis is selected, you can’t turn it off other than by turning off the entire AP. Once a vertical mode is selected, the only choices are VS or ALT or Nav-APR-GS. Off is not an option for the vertical unless you turn off the entire AP. With the Stec 30 and 50, there is an Alt on/off switch usually mounted on the yoke. I have always wanted that in my Stec 60-2 as there are times when I just want lateral control, like in turbulence or mountain waves and don’t want to go through the extra step of turning off the AP and back on in a lateral mode.

    Snu164,

    The Stec 30 does not have the ability to intercept a course, you have to do this part manually and turn on course with the needle centered and then engage the Hi or Lo TRK mode.

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  3. snu164 on May 16, 2024

    Thanks Mark and John.

    John- In addition to what Mark added about the 55x, the KAP-140 engages VS mode by default when you press the AP button. It effectively locks your pitch at whatever it is when you press the button.

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  4. Mark Kolber on May 17, 2024

    John, that’s why my question was about “an autopilot that cannot fly a vertical path at all.” I guess I should not have used the word “path.” Perhaps “vertical climb or descent mode” would have been a better choice of words. If there’s a VS mode, it doesn’t fit my question.

    snu, as you point out, it has VS climb and descent capability. Not only VS capture, but VS adjustment (also, it will capture a glideslope or glidepath)

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  5. Mark Kolber on May 17, 2024

    Duh. “It” meaning the KAP 140.

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