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According to this YouTube Video I heard the mechanism that moved the canopy, and then I heard a small buzzing sound. The video description says that it is spooling something, but I don't know what exactly.

Also, I am completely blind, so I have nothing to look at and only rely on sounds to know what is happening.

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  • $\begingroup$ Are you refering to this sound? link $\endgroup$
    – blackswan
    Apr 21, 2020 at 11:32
  • $\begingroup$ Yes, right after the canopy closes with a loud hissing sound, a few seconds later you hear a faint buzzing sound rising in pitch, and it happens a second time, but a little lower in pitch, though still rising. $\endgroup$
    – HeavenlyHarmony
    Apr 21, 2020 at 23:38

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The relevant part from the video description that you referred to:

You'll here a buzz, thats the battery, then you'll here it spooling thru N (nancy) stages.

The word "spooling" does not refer to the battery, it refers to the engine. The battery is static and does not spool.

There are several measurements or indications used to convey a turbine engine's state. One of them is N2 (others include N1, Engine Pressure Ration, Exhaust Gas Temperature, Interstage Turbine Temperature and several others).

Back to the video description. In this case I believe the author was referring to the N2 measurement that raises ("spools") and needs to be monitored during engine start.

N1 is the low-pressure compressor speed, and N2 is the engine's high-pressure compressor speed (both usually expressed in percentages rather than actual RPM).

More information about N1 and N2 can be found here: What are N1 and N2?

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