Timeline for Does the radial needle of a HSI automatically deflect to the correct position when tuning the NAV radio to a localizer / ILS?
Current License: CC BY-SA 4.0
10 events
| when toggle format | what | by | license | comment | |
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| Nov 27, 2021 at 7:18 | comment | added | JetCityMatt | @Programmer Your autopilot doesn't "find the correct radial" when you tune in a localizer because a localizer transmits only one course (unlike a VOR which has 360). There is no course that needs to be found because there is only one course. | |
| Nov 26, 2021 at 21:20 | comment | added | user22445 | No problem, after I thought about for a few moments I deleted my comment because it did not add much to the essence of the OPs question. | |
| Nov 26, 2021 at 20:58 | comment | added | Jan Hudec | @757toga I understood “HSI” to simply be generic name of the instrument, so I assumed it might include glass ones, including if the instrument is just drawn on the ND. I agree a mechanical one won't be able to connect to FMS at all. | |
| Nov 26, 2021 at 20:21 | comment | added | Jan Hudec | @Programmer, no. The autopilot simply turns left when the needle is on the right, moves to the right, or accelerates to the right, and vice versa. If you are on the right, but facing away, turning left will get you further from the radial until you either make 180° or the autopilot disconnects because the maximum deflection is exceeded (you could capture a side lobe outbound otherwise). I think some autopilots will reverse the sensing when the dialed course is more than 90° off your heading, so they'll capture the outbound radial instead. | |
| Nov 26, 2021 at 19:56 | comment | added | TheEagle | @JanHudec ah, I didn't know that ! So I guess if you engage the autopilot while flying away from the radial you will have to go around the earth once to capture it, right ? | |
| Nov 26, 2021 at 19:38 | comment | added | Jan | Depends on the autopilot, some autopilots require a course to be entered in the FMS before they can capture the localizer. General Aviation autopilot usually don't suffer from such weaknesses. | |
| Nov 26, 2021 at 18:44 | comment | added | Jan Hudec | @Programmer, the autopilot does not really know the radial at all, it just steers until the needle stops moving. | |
| Nov 26, 2021 at 17:23 | comment | added | TheEagle | I'm referring to small GA aircraft with steam panel. I understand that the course cannot be set just based on the freq - but the autopilot (for example the Cessna 400 Nav'O'Matic) does find the correct radial - so why couldn't it set the radial on the HSI too ? | |
| Nov 26, 2021 at 17:20 | vote | accept | TheEagle | ||
| Nov 27, 2021 at 22:57 | |||||
| Nov 26, 2021 at 16:31 | history | answered | Jan Hudec | CC BY-SA 4.0 |