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From:295vv [at] 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 [at] centuryflight.com



David Jones

Pecatonica, Illinois