The HSI of the Bonanza and the heading indicator of the C172

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Simicro
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The HSI of the Bonanza and the heading indicator of the C172

Post by Simicro »

Hi all,

I was lucky enough to have been able to acquire the C172 and the Bo at the same time.

On the default P3Dv4 airport (KVPS) runway 19:

1) By default, the heading indicator of the C172 is not set. So I pass the mouse over the magnetic compass and read "195" thanks to the tooltip feature, then set the heading indicator accordingly.

2) By default, the HSI of the Bo reads "195" right away after loading ?!?! No need to set it. Why is that please?
P3Dv4.5 - V35B - C172 - Cherokee
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Blitzer
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Re: The HSI of the Bonanza and the heading indicator of the

Post by Blitzer »

That is the correct behaviour for the Bonanza, basically the HSI automatically corrects itself- I forget the technical details, but I did read it here somewhere in the forums. :wink:

Paul

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Simicro
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Re: The HSI of the Bonanza and the heading indicator of the

Post by Simicro »

Oh! Nice to see you in this thread Blitzer :)

Understood.

Thanks.
P3Dv4.5 - V35B - C172 - Cherokee
i5 4670K @4.3 Ghz - 32 Gb DDR3 - GTX 1080 8 Gb - 2K @165 Hz G-Sync - Win 7 x64
Microsoft Force Feedback 2 modded with CH Fighterstick - VKB Sim T-Rudder Mk.IV Pedals

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AKar
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Re: The HSI of the Bonanza and the heading indicator of the

Post by AKar »

Simicro wrote:2) By default, the HSI of the Bo reads "195" right away after loading ?!?! No need to set it. Why is that please?
The HSI can be slaved to the magnetic heading when the slaved/free gyro selector is set appropriately. It would require electrical power to align correctly, as the heading card is driven by a stepper motor. Therefore it would not indicate correctly on a non-powered airplane that has been moved since it was powered down.

-Esa

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Simicro
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Re: The HSI of the Bonanza and the heading indicator of the

Post by Simicro »

Hello ESA,

Many thanks. Interesting.

I did not see a "slaved/free gyro selector" on the Bo?
P3Dv4.5 - V35B - C172 - Cherokee
i5 4670K @4.3 Ghz - 32 Gb DDR3 - GTX 1080 8 Gb - 2K @165 Hz G-Sync - Win 7 x64
Microsoft Force Feedback 2 modded with CH Fighterstick - VKB Sim T-Rudder Mk.IV Pedals

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Oliver Branaschky
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Re: The HSI of the Bonanza and the heading indicator of the

Post by Oliver Branaschky »

Simicro wrote: I did not see a "slaved/free gyro selector" on the Bo?
P. 93 of the manual, item #16.


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Simicro
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Re: The HSI of the Bonanza and the heading indicator of the

Post by Simicro »

Thanks Oliver, I'll read that.
P3Dv4.5 - V35B - C172 - Cherokee
i5 4670K @4.3 Ghz - 32 Gb DDR3 - GTX 1080 8 Gb - 2K @165 Hz G-Sync - Win 7 x64
Microsoft Force Feedback 2 modded with CH Fighterstick - VKB Sim T-Rudder Mk.IV Pedals

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Nick - A2A
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Re: The HSI of the Bonanza and the heading indicator of the

Post by Nick - A2A »

Simicro,

Yes, the slaved or free mode of the KI-525A HSI is controlled via the separate KA 51B slaving meter (mounted below the altitude selector in the Bonanza). For normal operation, keep the switch in the 'slave' position and the unit will adjust itself for gyro drift using a separate magnetic sensor.

Thanks,
Nick

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Simicro
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Re: The HSI of the Bonanza and the heading indicator of the

Post by Simicro »

Clear, thank you Nick.
P3Dv4.5 - V35B - C172 - Cherokee
i5 4670K @4.3 Ghz - 32 Gb DDR3 - GTX 1080 8 Gb - 2K @165 Hz G-Sync - Win 7 x64
Microsoft Force Feedback 2 modded with CH Fighterstick - VKB Sim T-Rudder Mk.IV Pedals

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ClipperLuna
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Re: The HSI of the Bonanza and the heading indicator of the

Post by ClipperLuna »

I was curious about these myself so I did some poking around. I found this: http://www.flight-mechanic.com/gyroscop ... g-compass/

If you can make sense of it, please let me know :mrgreen:

Now if we could just figure out how the Simulated Elevator Force thingamajig works :wink:

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AKar
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Re: The HSI of the Bonanza and the heading indicator of the

Post by AKar »

ClipperLuna wrote:I was curious about these myself so I did some poking around. I found this: http://www.flight-mechanic.com/gyroscop ... g-compass/

If you can make sense of it, please let me know :mrgreen:
That's a little bit curiously written little article, anyways, flux gates are basic sensors used particularly in small and medium-sized airplanes, among the others. It works by detecting the collapsing and recovering of the Earth's magnetic flux that is "gated" through the core by saturating and un-saturating it repeatedly. Essentially, when the core material is not saturated by the excitation current, it provides a local preferred path for the Earth's magnetic field, concentrating a higher flux value than in free space. When the core material is saturated, it will not provide that preferred path anymore, so the Earth's field passes around it somewhat like it would without the material being in place, thus collapsing the component of the Earth's field through the core. The changes of this component as it collapses and recovers are detected as voltage spikes induced into the sense coil, whereas the much larger changes caused by the excitation current are not as they are routed through the sense coil twice, but in opposite directions, cancelling out.

What's more complex is the electromechanical artwork used to make these pictorial navigation instruments work. These things are very complicated and very often use some rather clever tricks to achieve some desired functions which would be easy to take for granted as some simple needle or flag movements. They are quite fascinating, actually. :)

-Esa

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scottb613
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The HSI of the Bonanza and the heading indicator of the C172

Post by scottb613 »

Hi Folks,

Great write up Esa - how it worked was beyond the scope of my knowledge - thanks...

I’ve got the slaved Century - NSD-1000 - it has a separate power switch (the HSI itself is vacuum powered) on my panel and will maintain the compass setting input at the beginning of the flight - but it has to be set before each flight as it doesn’t automatically slew to the correct compass setting... I don’t know if the BK version behaves differently...

Regards,
Scott


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