HSI Slaving Needle?

[RobertGerace]

Please look at the attached picture, and tell me what the needle in the upper-right-hand-corner is telling me.

I've been told that if it is directly on the mark of the 7:00 position that the HSI is slaving to the remote compass. However, what if it is not? What if it is pointing up and down...or 9-3 o'clock?

I had some trouble with it not slaving two flights ago, but last night it seemed perfect. (I never had any flags). Anyway, it got me to thinking...what exactly is that little needle telling me?

 

[Maverick]

Please look at the attached picture, and tell me what the needle in the upper-right-hand-corner is telling me.

I've been told that if it is directly on the mark of the 7:00 position that the HSI is slaving to the remote compass. However, what if it is not? What if it is pointing up and down...or 9-3 o'clock?

I had some trouble with it not slaving two flights ago, but last night it seemed perfect. (I never had any flags). Anyway, it got me to thinking...what exactly is that little needle telling me?

I'm not familiar with the HSI you have but if that needle is like the one on the slaving switch for my King HSI the it should tell you whether the HSI is in agreement with the flux detector. On mine, if the needle is centered then it's sync'd and if it's not cenntered then it indicates a deviation between the HSI and the flux detector.

Jeannie

 

[MauleSkinner]

Slaving indicators generally wave back and forth a little, indicating minor fluctuations between what the flux detector is sensing and what the heading indicator is showing. This is normal, and the system makes the corrections necessary to stay within tolerances.

If the slaving indicator is pegged all the way to one side or the other, you have a slaving problem. This indicates that the heading indicator is nowhere near what the flux detector is sensing, and the system is unable to correct the situation.

I had that happen on a Hawker not too long ago...the flux detector had leaked out all of its dampening oil, and "died"...lights lit up, the autopilot and flight director clicked off, and there I was...hand flying the airplane until we thought to go to DG mode, which eliminated the internal crosscheck, and allowed us to re-engage all that good stuff that makes us so lazy

Fly safe!

David

 

[Maverick]

Slaving indicators generally wave back and forth a little, indicating minor fluctuations between what the flux detector is sensing and what the heading indicator is showing. This is normal, and the system makes the corrections necessary to stay within tolerances.

If the slaving indicator is pegged all the way to one side or the other, you have a slaving problem. This indicates that the heading indicator is nowhere near what the flux detector is sensing, and the system is unable to correct the situation.

I had that happen on a Hawker not too long ago...the flux detector had leaked out all of its dampening oil, and "died"...lights lit up, the autopilot and flight director clicked off, and there I was...hand flying the airplane until we thought to go to DG mode, which eliminated the internal crosscheck, and allowed us to re-engage all that good stuff that makes us so lazy

Fly safe!

David

I had a similar situation while flying into the Chicago area. In my case it was the remote gyro that failed and it happened while I was IMC at 2400 feet over Lake Michigan and being vectored to the ILS 16 approach into Palwaukee. Without the gyro my autopilot was useless so I ended up using my handheld GPS is HSI mode for heading information while I flew the approach. The first thing I did was inform ATC that I lost my gyro and the very next thing I heard was ATC giving me a new heading. I couldn't help wondering if he paid any atention to what I just told him. After I was established on the approach he asked me if I needed any special handling. Ceiling was 600 overcast with moderate turbulence, this was one of those brief moments that punctuate the hours of boredom.

My airplane is pretty well equipped and all those gadgets sure are nice as long as they work properly when you need them.

Jeannie

 

[Bill]

After I was established on the approach he asked me if I needed any special handling.

Like maybe an ASR/No gyro approach?

 

[Maverick]

Like maybe an ASR/No gyro approach?

Yes, that's what I would have expected and maybe he wanted me to specifically ask for that but I was a little busy at that precise moment. It was several minutes later when I was established that he asked the question. My approach was a little erratic so maybe that's what prompted him to ask. But when he did ask I was in good shape.

They were kinda busy, like that never happens in Chicago, so maybe he didn't pay attention to what I said. The President was also in Chicago that day and there were TFRs all over Chicago Land.

It was a day I'll certainly remember.

 

[MauleSkinner]

I Without the gyro my autopilot was useless so I ended up using my handheld GPS is HSI mode for heading information while I flew the approach.

If the indicator was basically "stuck" on a heading, you can still use the autopilot...simply put the heading bug at the 12 o'clock position, and engage heading mode. For turns to a different heading, just move the bug in the direction you want to turn, let the autopilot make its rate-based or attitude-based turn, and when you get to the proper heading, move the bug back to the 12 o'clock position to stop the turn. This would coordinate nicely with your handheld GPS in HSI mode.

Or, if you're flying one of those REALLY gee-whiz airplanes with GPSS, that bypasses the HSI entirely.

Fly safe!

David

 

[Maverick]

If the indicator was basically "stuck" on a heading, you can still use the autopilot...simply put the heading bug at the 12 o'clock position, and engage heading mode. For turns to a different heading, just move the bug in the direction you want to turn, let the autopilot make its rate-based or attitude-based turn, and when you get to the proper heading, move the bug back to the 12 o'clock position to stop the turn. This would coordinate nicely with your handheld GPS in HSI mode.

Or, if you're flying one of those REALLY gee-whiz airplanes with GPSS, that bypasses the HSI entirely.

Fly safe!

David

The trouble was that the gyro wasn't stuck, it sort of had a mind of it's own and just kept drifting. Therefore the only safe thing to do was to get it out of the picture altogether. All the more reason to not to allow ones self to become to dependent on those gadgets. There are times when there is no substitute going back to basics.

 

[MauleSkinner]

The trouble was that the gyro wasn't stuck, it sort of had a mind of it's own and just kept drifting. Therefore the only safe thing to do was to get it out of the picture altogether. All the more reason to not to allow ones self to become to dependent on those gadgets. There are times when there is no substitute going back to basics.

Well, that can be dealt with too in a lot of airplanes, but you're getting into an area where it's easier and safer just to take it out of the picture altogether, like you say.

By the way...there's NO SUCH THING as a "bad hair day"...ANY day with hair is a good day!

Fly safe!

David

 

[Maverick]

Well, that can be dealt with too in a lot of airplanes, but you're getting into an area where it's easier and safer just to take it out of the picture altogether, like you say.

By the way...there's NO SUCH THING as a "bad hair day"...ANY day with hair is a good day!

Fly safe!

David

The HSI was only good for flying in circles when the gryo went crazy, that was my reasoning for ignoring it. I have dual glide slope so I had a backup for the nav info and other than some lag the handheld GPS was a decent backup for heading info. It's just that a failure of that nature could not have happened at worse time. Single pilot IFR in IMC is just not a good time for a failure like that.

I recently saw a sign in a local auto shop that said "Bald men never have bad hair days"

But I see your point. Maybe it's time for me to change that tag line. I put it there originally because the picture in my avatar was taken on a really windy day and we had to take several to get one where my face wasn't covered. It really was a bad hair day.

Jeannie