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Motivation

I am working on best practices for a plane with a very slow constant speed prop. In my experience, it operationally takes 20 seconds or more to go from idle to full throttle (pushing the throttle faster than that causes the engine to overspeed as the prop can't catch up). This is a substantial time to be sitting on the departure end of the runway, and contributes to traffic congestion on busy days.

One time saver is to taxi onto the runway immediately after landing traffic passes overhead. The engine can be spooled up while the preceding plane is landing and taxiing off.

Likewise for departing aircraft as soon as they've begun their takeoff roll.

Question

For standard Part 91 operations at non-towered airports, what FARs are applicable to taxiing onto the runway while other planes are still using it for takeoff, landing flare, or taxiing clear? I know ATC can ask a pilot to "line up and wait", but I'm unaware if there are different FARs in effect when ATC is involved.

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    $\begingroup$ I have never heard of a prop that takes 20 seconds to reach full RPM. What aircraft, and what engine/prop do you have? $\endgroup$
    – Mike Sowsun
    Commented May 19, 2023 at 12:19
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    $\begingroup$ @MikeSowsun it's not the A/C or engine, it's the MT-7-A electric constant speed prop. It takes 90 seconds to fully feather, and, yes, I have timed that. It does not take 20 seconds to reach full RPM, it takes 20 seconds to pitch sufficiently so as not to exceed redline. I've fixed the question to make that point clearer. $\endgroup$
    – Kenn Sebesta
    Commented May 19, 2023 at 12:53

1 Answer 1

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There are no regulations explicitly against lining up and waiting at untowered airports. However, you are turning your back to final approach for the runway you are on for the indeterminate amount of time it takes for the airplane before you to clear the runway, and if there is a problem it is possible 91.13(b) would be applied.

Regarding your issue of long spool-up times, it sounds like your low pitch stop needs adjusting. Refer to "Adjusting the static RPM" in the propeller manual. The low pitch stop should already be in the takeoff position, and it should not be possible to overspeed on the ground.

From the manual:

Check max. static RPM with full throttle and blades in take off position on ground. The static RPM must be 50 - 100 RPM below max. permissible RPM (see flight manual).

If your static RPM is over the maximum permissible RPM, then your propeller is adjusted incorrectly according to the manual and your aircraft is not airworthy.

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    $\begingroup$ I wish I had an extra credit upvote available for the maintenance troubleshooting suggestion! $\endgroup$
    – Michael Hall
    Commented May 19, 2023 at 16:24
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    $\begingroup$ @MichaelHall, I as well! $\endgroup$
    – Kenn Sebesta
    Commented May 19, 2023 at 17:12
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    $\begingroup$ Although with further consideration, I'm not so sure the prop is set up incorrectly. I suspect because this is a motorglider and an in-air wind-milling starts can be required, it might make sense to have a very, very flat pitch available. $\endgroup$
    – Kenn Sebesta
    Commented May 19, 2023 at 17:20
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    $\begingroup$ @KennSebesta I would think the propeller should have no trouble windmilling in a normal takeoff pitch, and a finer pitch risks the same overspeed condition in flight. But anyway it's something to talk to a mechanic about. $\endgroup$
    – Chris
    Commented May 19, 2023 at 18:14
  • $\begingroup$ I realized I never followed up on the maintenance aspect of @Chris's answer. Indeed, when talking with MT Props and the airplane manufacturer, both confirmed that the prop should not be able to exceed redline while in static RPM. This has since been resolved. $\endgroup$
    – Kenn Sebesta
    Commented Sep 17 at 1:33

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