ATTN: A&Ps or avionics guys. HSI

[N6399A]

What's the scoop with HSIs. How often should they be bench checked and what are the costs involved. I know the cost will vary depending on whether repairs are needed, but in general what do HSI bench checks run? A friend bought a plane with one that hasn't been touched in like 8 years. Thanks in advance guys.

 

[Steve]

From an NTSB report...

According to the Cessna 210 Service Manual, "The service life of shock-mounted instruments is directly related to adequate shock-mounting of the panel. If removal of the shock-mounted panel is necessary, check mounts for deterioration and replace as necessary."

 

[wsuffa]

Depends on the HSI.

My HSI system has a remote gyro and remote compass. Maintenance is "as required". The only trouble I've had in 8 years came after a crooked shop somewhere stole my remote gyro and replace it with a junker (that acted up on a climb out of 4 Corners...)

 

[JHW]

just had my kcs55A gyro unit overhauled for $2800

it made it 12 years which must be a record

 

[gismo]

just had my kcs55A gyro unit overhauled for $2800

it made it 12 years which must be a record

Maybe, but mine's 11 years old and running fine (knock on wood).

 

[gismo]

What's the scoop with HSIs. How often should they be bench checked and what are the costs involved. I know the cost will vary depending on whether repairs are needed, but in general what do HSI bench checks run? A friend bought a plane with one that hasn't been touched in like 8 years. Thanks in advance guys.

Sheri, it depends on the make/model of HSI as well as the way it's been treated, especially the gyro. There are several that I'm aware of commonly found in GA planes. Collins made one called a PN-101 which AFaIK is one of the most reliable although I've heard that it's expensive to repair. Century made two, the NSD-360 (air powered) and the NSD-1000 (electric). Both have internal gyros which Century touts as an advantage (lower install cost) but the rest of the world sees only the downsides which include the fact that the gyro is too small, and very difficult to get at, plus it's more difficult to isolate from aircraft vibration than a remote gyro. Honeywell/Bendix/King has the KCS-55(A) which has a remote Gyro (KG-102). I believe that the latest versions (anything made since around 1990) are more robust than earlier units and I've heard that used units on the market often have gyros that may not last very long.

 

[N6399A]

Thanks guys, I'm not sure why but I was under the impression that HSIs were something that had to be service at specific intervals. I almost bought a NSD-360, but my A&P and avionics guy had a fit. Guess they just want me to get the King/Bendix. Hope I live long enough to be able to afford it.

As far as my friend's HSI goes, if it's not broken don't fix it. Got it.

 

[SCCutler]

I have flown behind NSD-360s for years, and been quite happy with their performance.

 

[wsuffa]

Thanks guys, I'm not sure why but I was under the impression that HSIs were something that had to be service at specific intervals. I almost bought a NSD-360, but my A&P and avionics guy had a fit. Guess they just want me to get the King/Bendix. Hope I live long enough to be able to afford it.

As far as my friend's HSI goes, if it's not broken don't fix it. Got it.

The King unit is all electric. I, personally, like the idea of having the HSI on a power source other than vacuum. YMMV

 

[SCCutler]

The King unit is all electric. I, personally, like the idea of having the HSI on a power source other than vacuum. YMMV

Agreed, without reservation. Electric HSI is at least as valuable as a backup AI (IMHO).

 

[sba55]

A friend of mine has one of the Sandel all electronic HSIs.

I'd love to get one. It shows holds (from the GPS), DME, the MAP (and other fixes), speed, etc. It can also show 2 RMI pointers in addition to the primary NAV. Flying an approach is a lot less work that way since you don't look over to the GPS nearly as much.

Of course, it also costs something like $7500 I want one!

-Felix