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From:295vv@aol.com (295 v v @aol.com)
I have a Century Flight Systems NSD-1000 HSI (12 volt electric) in my Lancair
IV. The first unit I bought failed, if I remember correctly, 5 times in 65
hours. After some very heated conversations, they replaced this unit, and the
replacement has now failed after 135 hours. It, of course is now considered
to be out of warranty, and the cost to replace the bearings is $450 plus
about $50 freight.
I am not a happy camper. I have continuously complained that this unit, a 12
volt unit, is producing too much internal heat, with no way to disperse the
heat from the closed, unvented can it is in. You can actually burn your
fingers when you touch the bezel or the can exterior.
This is the first failure of bearings, the other failures having been
attributed to masking tape on the armature, several failures of the speed
controller, fuse failure, etc. It is not surprising that the heat cooked the
lubricant out of the bearings this time.
I am putting a thermocouple on the unit to verify exact temperature for future
use.
I attempted to cool this unit by having a large fan blowing on it all the
time--I liken this to trying to pee on a bonfire--too little, too late.
Interestingly, Century now says they put a capacitor inline to the speed
sensor to lower internal temperature, and this mod will be in my repaired
unit. The problem, as I see it, is that the unit was designed for 28 volts
initially, and when they modified it for the 12 volt market, they had to up
the amps to drive the gyro at the same speeds.
Since amps are higher, they put more heat in the can. I hope the capacitor
lowers internal temperature a lot.
Well, I have to tell you, I have really had it. I would like to hear from
other NSD-1000 owners about any experience--good or bad--so that I can prepare
my future plans--which obviously do not include spending $500 bucks every
hundred or so hours. 6 failures in 200 hours on two units is too much.
One of my options is to formally petition the FAA for a review of the
performance of this product. For this, I want to know of other people that
have had problems with this HSI.
One of the failures put me into a 70 degree roll at 250 kts over the Saint
Louis airspace when it decoupled erratically and continued to drive the
autopilot for a few seconds. We have had heated exchanges over this product,
as you might expect.
My personal opinion is that the case of the unit should be vented with louvers
or a blast tube, and that cooling air needs to be directed into the interior
of the unit. When I bring this subject up, it is like talking to a stone
wall. Obviously, recertification would have to be done if the design was
changed.
The president of Century Flight Systems, Bill Eubanks, wrote me the following:
"Century Flight Syestems does not have an extended warranty policy at this
time...a warranty is a tool to take care of infant mortality of parts or
workmanship in a product if needed. I feel that it is serving its purpose in
your case." (5th failure, new replacement, 11-6-97).
The term, ''infant mortality", becomes rather special after 6 failures. I
notice that "infant mortality" because of design was not mentioned.
Personally, I expect an $8000 piece of equipment to have a MTBF of more than
34 hours, am I wrong to expect this?
CC: Bill@centuryflight.com
David Jones
Pecatonica, Illinois
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