SigmaTek backup AI

[FlyDave]

I have a SigmaTek electric backup attitude indicator with inclinometer in my Bravo. Sometimes it flags, sometimes is doesn't, and once it has rolled off to the side.

It was installed new in the plane in June of 2011, so it's less than 3 years in service.

SigmaTek wants $1,162 to o/h the unit and it will take 4-6 weeks.

As far as I'm concerned, for an instrument like this to last less than 3 years doesn't seem right. I don't want to go down the same road in another 2 1/2 years.

Can anyone share their experience with SigmaTek product quality and service? Should I just buy a Castleberry?

 

Thanks,

 

Dave

[Danb]

The dyson efis looks awesome but not certified great features..

[N601RX]

Check with other shops on the price. It seems very high. I got several quotes on a DG last year and found some to be twice as high as others. Berkshire was the cheapest and fastest. They mailed it back in 2 days. Their prices are online.

It's also possible your original gyro set of a shelf for a long time. Setting is bad for them, about like an engine. Some manufactures only have a 6 month shelf life policy.

[OR75]

Have you considered replacing it with the RC Allen 2600-3 ?

 

I don't have one, but I am thinking about it to replace my T/C.

 

On the plus side:

glass feel to it

very light and not deep ( easy on our heavy sagging instrument panels)

FAA approved replacement to a T/C

 

On the minus side:

about $2700 + install

[Mooneymite]

I've never owned a Sigma Tek, but I have a friend who had both the electric AI and DG.  Both failed within four years; due to repair costs, he elected to sell them to a repair shop.  He took a bath.

[FloridaMan]

The dyson efis looks awesome but not certified great features..

 

I have one. I would not trust it. 

[FlyDave]

Check with other shops on the price. It seems very high. I got several quotes on a DG last year and found some to be twice as high as others. Berkshire was the cheapest and fastest. They mailed it back in 2 days. Their prices are online.

It's also possible your original gyro set of a shelf for a long time. Setting is bad for them, about like an engine. Some manufactures only have a 6 month shelf life policy.

Global Tech in Huntington Beach, CA is the cheapest so far @ $950 and ~ 1 week turn around.

Bershire is getting back to me tomorrow with whether he can rebuild this unit. One other company is doing the same.

 

Have you considered replacing it with the RC Allen 2600-3 ?

 

I don't have one, but I am thinking about it to replace my T/C.

 

On the plus side:

glass feel to it

very light and not deep ( easy on our heavy sagging instrument panels)

FAA approved replacement to a T/C

 

On the minus side:

about $2700 + install

This looks like a great unit - but pricey!

This brings up a question about modern avionics: Are solid state devices going to last 4-5 times as long as the mechanical/gyroscopic instruments? Is there really any sense in overhauling a mechanical gyro device today?

 

I've never owned a Sigma Tek, but I have a friend who had both the electric AI and DG.  Both failed within four years; due to repair costs, he elected to sell them to a repair shop.  He took a bath.

This is the kind of report I don't like to hear - but I need to!

 

Thanks all,

 

Dave

[donkaye]

My Castleberry was still going strong after I'm not sure how many years before it was removed for my panel upgrade.  Top Gun has it and would probably give you a good deal on it.

[jetdriven]

Another shop to try is Aircraft Quality Instruments. They are a mom-and-pop shop in Wichita KS. I have a Century 52D66 and 52D44 AI and DG overhauled by them.  ~500$ each exchanged and 300 hours / 2.5 years on them no issues.  www.flyaqi.com.   Phone is best.

 

We also have a Castleberry electric AI.  It replaced the turn and bank. I bought it used from ebay for 800$ and after 30 hours, it stopped working with no flag. I sent it in for IRAN and it was a burned wire on the circuit board, they repaired it and tagged it for 300$. They claimed it was caused by being wired on the master and starting current caused it, so I rewired it from the avionics bus.  For the last 250 hours it has worked fine. Be warned, though, the Castleberry can only be overhauled by them and its 1100$. But from what I have seen, its a better unit than the others and far better than the RC Allen electric gyro.

[FlyDave]

Thanks for the tip Byron!

I looked at their web site and their prices are the best I've seen. I'll call them tomorrow.

 

Dave

[FlyDave]

In calling around about this yesterday, I found that only a few shops will work on this unit.

A couple of them said that SigmaTek hasn't released the service manual on this unit. Without the manual, can a shop legally repair this unit?

[wiguy]

FWIW, I bought a used Castleberry electric gyro about 1.5 years ago from an avionics shop. It has worked fine until it started to tumble uncontrollably a few weeks ago. I grew to like it and explored options. I ended up removing it myself and exchanging with Castleberry for a factory overhauled unit, $1100 as posted.

The new one went in easier than out and is working great. Now that I know the history, if this one fails I may go a different direction.

[FlyDave]

My left alternator died 6 or 7 weeks ago. I had it rebuilt and since then, approximately 10 flight hours, my Sigma Tek has not flagged or tumbled.

It seems to me like I had a bus voltage issue issue before getting the left alternator rebuilt and that was causing the Sigma Tek to fail. I'm not completely convinced that the issue is resolved but prior to the alternator rebuild it definitely flagged at least once in 10 hours of flight. I'll post again if it flags or tumbles.

[Piloto]

Dave 

 

Does your plane has a vacuum pump. I would consider just installing an old fashion vacuum gyro. With the vacuum gyro you get another source of backup power other than electric. On my 1982 M20J I have the original vacuum AI that drives the autopilot. Had it overhauled at 2000hrs for $300 at a local shop and at 2800hrs still working good. Never had an issue with it. Unlike electric gyros, vacuum gyros has no motor, just air rushing against the gyro wheel. Very simple and reliable mechanism.

 

José 

[FlyDave]

Dave 

 

Does your plane has a vacuum pump. I would consider just installing an old fashion vacuum gyro. With the vacuum gyro you get another source of backup power other than electric. On my 1982 M20J I have the original vacuum AI that drives the autopilot. Had it overhauled at 2000hrs for $300 at a local shop and at 2800hrs still working good. Never had an issue with it. Unlike electric gyros, vacuum gyros has no motor, just air rushing against the gyro wheel. Very simple and reliable mechanism.

 

José 

 

Jose,

 

The Bravo has 2 alternators, and engine driven vacuum pump and an electric back up vacuum pump.

The KI 256 attitude indicator is a vacuum driven device so I think I'll keep the electric backup AI. I like redundancy!

 

Dave

[jetdriven]

to be legal, a backup gyro must be electric if the primary AI is vacuum. Two vacuum gyros wont work. You can have two electric gyros but one must have a backup battery.

[Piloto]

A primary AI vacuum gyro does not require a back up, since most IFR certified planes do not have a second AI gyro. If I loose vacuum I rely on the turn coordinator for roll and the altimeter for pitch. I also use the Aera 560 and 530 for instant heading guidance. I found the VSI on the 560 to be instant response unlike the pneumatic VSI. In fact you can rely alone on the 560 instrument page for sole guidance into an approach, just try it. I was shocked how well it works first time I tried. No overshooting at all.

 

José   

[jetdriven]

Which is better and gives more data, a turn coordinator which only displays rate of turn, or a second attitude indicator which displays both pitch and roll? I like the dynon D1 but if you think an Aera turn presentation is good enough clipped to the yoke is good enough, that will get you killed.

[Piloto]

I would rather have a working and reliable turn coordinator than a faulty electric attitude gyro. My turn coordinator is 32 years old and never failed on me. It outlasted Dave's Sigma Tek by 29 years. And still working quietly. On a flat spin a turn coordinator will tell which pedal to press for recovery but an AI would not.   

 

José

[jetdriven]

It outlasted Dave's AI but the MTBF on both is 2000 hours. And one gives you pitch, one you guess, and if you are in a flat spin in IMC there's a few reasons why you should have caught it and you are probably dead already. But if you find yourself in that situation, press on the pedal that's hardest to push.

[Piloto]

It outlasted Dave's AI but the MTBF on both is 2000 hours. And one gives you pitch, one you guess, and if you are in a flat spin in IMC there's a few reasons why you should have caught it and you are probably dead already. But if you find yourself in that situation, press on the pedal that's hardest to push.

 

How would you know when to release the pedal?

An attitude gyro can tumble under severe turbulence or maneuvering. Turn coordinators just don't tumble.

 

Even if you have two attitude gyros how do you know which one has a subtle tumble and show different bank angles, they don't red flag when they tumble. That was my dilema five years ago in IMC in severe turbulence. Luckily this plane had a turn coordinator to resolve the dilema.    

 

Check this:  

 

José

[Piloto]

For those interested in history.

 

On Charles Lindbergh Spirit of St. Louis plane the only gyro it had was a turn rate gyro, no attitude gyro. For pitch control he used a fluid inclinometer similar to those used in boats. You can get one of these at West Marine stores and stick it to the left side panel. With the inclinometer and turn coordinator you have pitch and roll. If it worked for Lindbergh for 33 hours on a plane with no forward visibility (windshield blocked by fuel tank) at all it should work for you. No gyro tumbling for sure, much less expensive than a second attitude gyro, 1000 times more reliable and no MTBF to worry about. Just can't imagine Lindbergh in the middle of the Atlantic at night with no horizon view trying to cope with a tumbling gyro. And you thought that turn coordinators are worthless. 

 

Check with Lindbergh at http://inclinometer.blogspot.com/2013/07/the-spirit-of-st-louis-and-rieker.html

 

José

[jetdriven]

a turn coordinator was more reliable than gyro horizons on the 1920s but attitude gyros are much more reliable since.  You wont find a T/C in any Boeing 727,737,747,757, 767, 777, any flavor of a CRJ, a Beech 1900, or any G1000 aircraft either.

 

You can do a barrel roll with a bubble inclinometer centered, its physically no different that a jug of water.

 

Your rationale is that if you get into a spin in IMC without a T/C you are dead. I think if you get into a spin in IMC you are halfway to dead already. I have done a hundred spins in round-dial airplanes an not once did the AI tumble from that. The FAA agrees with the commuter and transport category airplanes and allows dual horizons in place of a T/C and A/I combo provided they are powered by separate sources and one has a skid ball, per AC91-75. 

 

here is some text:

The rate-of-turn indicator (either a turn coordinator or turn and bank indicator) is used to cross-check the attitude indicator and directional gyro for bank information. Turn coordinators

also include a failure warning flag that provides an indication if the gyro power source is lost.

The rate-of-turn indicator typically has an independent power source to provide redundancy for

the attitude indicator and directional gyro. However, the rate-of-turn indicator only provides information that the aircraft is in a turn and whether the turn is at the standard rate (a standard rate turn is 3 degrees per second, or 2 minutes for a full 360-degree circle). It does not provide information on the bank angle.

....

5. RATIONALE FOR CHANGE.

a.  Substituting a second attitude indicator (with a power source independent from the primary attitude indicator) for the rate-of-turn indicator will provide an increased level of safety. It will replace a gyro that only indicates direction and rate of turn with one instrument that presents turn direction, bank angle, and pitch attitude information. Also, a second attitude indicator will be less confusing during partial panel operations because it presents pitch and bank information in the same manner as the primary attitude indicator. The pilot’s scan and instrument interpretation during partial panel operations becomes easier because pilots will stillbe able to rely on an attitude indicator for pitch and bank reference just as they did during full panel operations. Recognition time that a failure condition exists will be equivalent to current system configurations.

b.

Replacing the rate-of-turn indicator will mean losing an easy reference for standard rate turns. However, in today’s air traffic control system, there is little need for precisely measured standard rate turns or timed turns based on standard rate. Maintaining a given bank angle on the attitude indicator for a given speed will result in a standard rate turn. Pilots using this AC to

substitute an attitude indicator for their rate-of-turn indicator are encouraged to know the bank

angle needed for a standard rate turn.

NOTE: The FAA preamble language for the 1970 amendment to

section

91.33, re-codified to section 91.205, states: “[T]he FAA believes, andall other commenters apparently agree ... the rate-of-turn indicator is no longer as useful as an instrument which gives both horizontal and vertical attitude information.”

[Piloto]

Not Dave's 2013 Sigma Tek AI

[jetdriven]

Dont buy crappy instruments.  Note he still has full redundnacy with another attitude source instead of an emergency turn direction-only instrument.  Note either are more accurate than a jug of water or a Garmin Aera panel page.