Master Switch Abnormally Loud

[RonM]

Friends and Mooney Colleagues:  When I turn the Master Switch on, the sound is abnormally loud. Like as if someone was operating a loud vacuum cleaner or a loud electric motor. (Just trying to describe the sound.) Definitely abnormal sound as I've owned the airplane 28 years. The loud noise did not go away after engine started, so I shut the airplane down, pending the mechanic taking a look. The Standby Vac was off as well as my TKS pump. All switches normal (off) as they should be. Does anyone have a guess what this issue might be? Any comments appreciated.

[LANCECASPER]

6 minutes ago, RonM said:

Friends and Mooney Colleagues:  When I turn the Master Switch on, the sound is abnormally loud. Like as if someone was operating a loud vacuum cleaner or a loud electric motor. (Just trying to describe the sound.) Definitely abnormal sound as I've owned the airplane 28 years. The loud noise did not go away after engine started, so I shut the airplane down, pending the mechanic taking a look. The Standby Vac was off as well as my TKS pump. All switches normal (off) as they should be. Does anyone have a guess what this issue might be? Any comments appreciated.

Does a gyro come on with your Master and is it going bad?

[RonM]

Hi. I just checked. The gyro mechanical  attitude indicator did not come on when I turned the Master Switch on. The gyro instrument remained crooked, dead - did not move at all. Then I turned on the standby vac and then that gyro instrument did move and straighten out, and settled in to a one notch nose low but level attitude. Thank U for your response!

[RonM]

I never knew my gyro to be going bad, but I guess now it is?

[PTK]

Do you have avionics cooling blowers behind the panel that go on with master? If so that motor maybe going bad. 
Look under the panel for orange or black scat tubing maybe 3/4 or 1” diameter and follow it. One end should be going to the radios and the other to a cooling blower box. Something similar to this:

 

[carusoam]

Expect bearing issues are a culprit when gyros get loud... or a fan, like Peter mentioned above... some Long Bodies have a fan for the windshield defrost...

Bearings wear for thousands of hours before they show signs of slowing down... sometimes they are imperceptible... depending how well you know your gyros... and gyros in general...

A back-up instrument may have to light itself on fire to be noticed by a pilot like me...

Slower to erect, faster to wind down, change in sound...

Healthy gyros are turning thousands of rpms... unhealthy bearings won’t be able to keep up... so the gyro slowly fades at its skills...

Gyros that have worn bearings can be easily OH’d... gyros that broke their bearings can experience a few other force related challenges... if the spinning parts go from 1krpm to zero in a short amount of time...

 

Now for the good news...

Are you an Aspen guy, or a Garmin guy, or possibly a Dynon guy?

So many Gyros getting pulled out for Aspen or G5 upgrades, you can probably find a duplicate gyro to the one you have....

PP thoughts only, not an instrument guy...

Best regards,

-a-

[RonM]

Thanks for your thoughtful reply. The bad gyro is a back-up bendix king overhauled attitude indicator. My primary attitude indicator is my Aspen unit. I guess I will replace the bad attitude indicator with a new overhauled attitude indicator?  Will that cure the problem?

[RonM]

Thanks for the thoughtful reply regarding the avionics cooling unit. Much appreciated. I will investigate that possiblity.

[carusoam]

Ron,

What AI is it (model number)?  Is it connect to a KAP/KFC autopilot...?

Often, some legacy instruments are left in place for a reason...

Kind of odd to have an electric mechanical AI.. most often the old AIs are vac powered...

Was this instrument always just a back-up AI?

Getting a gyro OH’d can be expensive...

There are a few electronic devices that would make a better back-up AI...

There are life-saver devices that are designed to be back-up devices...

... and Dynon D10s that are becoming popular ...

 

So... if you fly in IMC... plan for a more modern BU device, just because you can...

Does your ship still have a TC as well? (Just wondering)

How about a second Aspen?

 

PP thoughts only, not a mechanic...

Best regards,

-a-

[RonM]

Hmmmm. I may be reporting inaccurately on my own airplane. I bought the Mooney MSE new in 1991. (1997 Missile Conversion.)  I had the original Bendix King six-pack instruments that came with the airplane. Some years ago I got the Aspen PFD and MFD. (So two Aspen units.) Only one electronic attitude indicator though. (My Aspen MFD does not have an AI.) They moved my Bendix King mechanical AI over. Then the Bendix King mechanical AI failed some years ago and I got a replacement overhauled Bendix King mechanical AI. I know today when I turned on the Master Switch the mechanical Bendix King AI was dead, but turning the Standby Vac on caused the mechanical Bendix King AI to "boot up" although the nose was a full notch below the horizon. I agree I need a good back up AI for instrument flying. I am willing to replace for a new back-up AI - any type or brand you recommend. I guess you recommend the Dynon electronic AI as a back-up. I will probably get that or a similar unit from another manufacturer. I have the Bendix King KAP 150 Auto pilot and dual Garmin 430w GPS units. In addition to the Aspen PFD and MFD + some original mechanical turn coordinator, airspeed indicator, Altimeter, VSI and the back up mechanical AI. Also I have the Garmin ADS-B transponder, I think the 330X if I am not mistaken.  I do not know the AI model # off-hand,  although it is the very typical one you would see with the light blue back-ground.

Edited February 15, 2020 by RonM

[LANCECASPER]

Is your autopilot getting attituda from your vacuum KI256 (King) your Aspen have an EA(Electronic Attitude)-100 box behind the panel ?

[RonM]

I would guess, bet, and hope that the autopilot gets it's info. from the Aspen AI - and not the mechanical AI.  A good question I can't confirm, but I would imagine. I will find that information out, obviously. 

[PT20J]

OK, lets' sort this out.

First, the problem is electrical because it happens when you turn on the master switch and not the standby vacuum pump or engine.

Second, it's not the BK attitude indicator because that is a vacuum instrument, not electrical. As an aside, it is most likely a KG 258 and likely still drives your KAP 150.

 Blowers and motors turn slower than gyros and sound more like vacuum cleaners. Electric gyros spin really fast and when the bearings go out they sound more like a whine and/or a grinding sound.

If the sound is coming from the instrument panel area it might be the turn coordinator which is electric. Or it might be a bad avionics blower as already suggested. My bet would be that the defroster blower is running. There is a little microswitch behind the console that connects to the control cable with a wire "whisker" that can become detached. It's easy to check, just pull the defroster circuit breaker.

Skip

 

[gacoon]

11 hours ago, RonM said:

Friends and Mooney Colleagues:  When I turn the Master Switch on, the sound is abnormally loud. Like as if someone was operating a loud vacuum cleaner or a loud electric motor. (Just trying to describe the sound.) Definitely abnormal sound as I've owned the airplane 28 years. The loud noise did not go away after engine started, so I shut the airplane down, pending the mechanic taking a look. The Standby Vac was off as well as my TKS pump. All switches normal (off) as they should be. Does anyone have a guess what this issue might be? Any comments appreciated.

Pull the turn coordinator circuit breaker and see if the noise starts to away.

[Vno]

As the past couple of people have said, start by pulling a few circuit breakers. One at a time. Or conversely pull the Radio Blower, Defrost Blower, Turn Coord, and Auto Pilot C/Bs and then add each one back in individually to see what is making the extra noise. Those C/Bs are the common ones that start with power on.

Brian

[RonM]

LanceCasper:  I believe the autopilot works off of the Aspen, not the mechanical Bendix King AI. Yes, I have two Aspen units (PFD & MFD) but only 1 has an electronic attitude inidicator - by my choice. I did not go for the electronic attitude indicator for my Aspen MFD - so it is called the Aspen MFD 500, not the MFD 1000. Thanks again for your thoughtful comments.

[RonM]

PT20J:  Thank you for the comprehensive trouble-shooting instructions. I will absolutely check all that out.  Thoughtful commentary and much appreciated.

[RonM]

Gacoon and Vno:  Thank you for that advice.  I will definitely do the trouble-shooting by pulling the various circuit breakers.  I have owned my Mooney 28 years, but I am still learning about my own airplane.

[PT20J]

5 minutes ago, RonM said:

LanceCasper:  I believe the autopilot works off of the Aspen, not the mechanical Bendix King AI. Yes, I have two Aspen units (PFD & MFD) but only 1 has an electronic attitude inidicator - by my choice. I did not go for the electronic attitude indicator for my Aspen MFD - so it is called the Aspen MFD 500, not the MFD 1000. Thanks again for your thoughtful comments.

I would find out because it determines what failures affect the autopilot. The Aspen requires an EA100 to interface to the KAP 150 which adds around $3000 to installed cost. Your installation  paperwork should tell you. If the KG 258 doesn’t drive the KAP 150, it doesn’t make much sense to keep the standby vacuum pump as a backup for a backup.

Skip

[RonM]

P20J: I think I’m 99% sure that the Aspen is coupled to the KAP 150 auto pilot. The GPSS (GPS Steering) on the Aspen works with the auto-pilot. I would never get the Aspen and not have it work with the auto-pilot, and my avionics installer does things right. I kept the mechanical AI as a back-up, as I had room on my panel. I got the Aspen I would say like 10+ years ago, pretty much when it first came out. You’re right I should know 100% and I will definitely verify.  Thank you so much for your comments.

[LANCECASPER]

33 minutes ago, RonM said:

P20J: I think I’m 99% sure that the Aspen is coupled to the KAP 150 auto pilot. The GPSS (GPS Steering) on the Aspen works with the auto-pilot. I would never get the Aspen and not have it work with the auto-pilot, and my avionics installer does things right. I kept the mechanical AI as a back-up, as I had room on my panel. I got the Aspen I would say like 10+ years ago, pretty much when it first came out. You’re right I should know 100% and I will definitely verify.  Thank you so much for your comments.

For sure your Aspen is coupled to the autopilot, but the question is: From where does the autopilot receive it's attitude information?

The least expensive way to do it was to use the KG (King Gyro)258 Attitude indicator that was already in your panel. So if your installation was around $10,000 back then that's probably what they used.

The more expensive way to do it was to add a box to the installation called an EA(Electronic Attitude)-100. It emulates a King Gyro and sends attitude data to your autopilot. If you have this, your installation was probably around $13000 and your King Gyro might be there just as a back-up. 

 

I'm still betting that your noise is either coming from a electric turn coordinator or a bad avionics fan motor bearing.

[RonM]

LanceCasper:  Thank you for educating me to that. I will find out. I can't remember the exact cost all those years ago.  I don't know now where the autopilot gets the attitude info. If I pull the circuit breaker on the mechanical attitude indicator, and do the auto-test on the KAP 150 auto pilot, and the KAP 150 passes the self test,  will that demonstrate that the KAP 150 auto pilot gets the attitude info from the Aspen? (Just as a quick way to make the determination without consulting mechanic or aircraft logbook.)

[RonM]

I checked my logbook for the Aspen installation. I did not see any mention of an EA 100 adapter. I live in Manhattan and my airplane is at Caldwell N.J. Airport . I won’t be able to go to the airplane until Tuesday. I now worry my KAP 150 gets the attitude info from the mechanical gyro which seems inferior to me. 

[RonM]

LanceCasper (or anyone else who cares to comment):  If I replace my Bendix King mechanical AI with a Dynon D10 AI, can my KAP 150 get the attitide info. from the new Dynon D10 AI?  If my Auto Pilot is getting the attitude info from the mechanical AI (and not the Aspen) everything has been working nicely for me - so maybe it is okay. The Dynon D 10 looks really nice and would be a great back up AI to my Aspen AI. What do you think?

[LANCECASPER]

49 minutes ago, RonM said:

LanceCasper (or anyone else who cares to comment):  If I replace my Bendix King mechanical AI with a Dynon D10 AI, can my KAP 150 get the attitide info. from the new Dynon D10 AI?  If my Auto Pilot is getting the attitude info from the mechanical AI (and not the Aspen) everything has been working nicely for me - so maybe it is okay. The Dynon D 10 looks really nice and would be a great back up AI to my Aspen AI. What do you think?

No it can't