Three new questions

[AndreiC]

Today I spent some time with my plane and ended up with three new questions:

 

1) My boost pump makes an awful racket when on. At idle I can hear it running even over the din of the engine, with noise cancelling headset on. It has a loud whining sound. Is it on its way out, and should be looked at, or is this normal? It makes fuel pressure as it should.

 

2) I suspect more and more that my manifold pressure shows about 1.5” less than it should. Today, on the ground, long after the engine was stopped, it showed 28” MP. The altimeter setting was 30.35”, and I am at a field at 830 feet elevation. I think the MP should have been showing 29.5”. Am I right? Also, I was flying today at 24/2400, and my fuel flow for 100 ROP was 11.5 gph. That seems high to me.

 

3) I keep having a problem with the bluetooth connection between my Bose A20 headset and my iPhone 13. Every couple of minutes or so, the connection drops (shows in iPhone as disconnected) and a couple of seconds later reconnects. It does an annoying chime sound when doing so. Has anyone else experienced this? Is there a fix?

 

Thanks,

Andrei.

 

 

Sent from my iPhone using Tapatalk

[MikeOH]

1) The boost pump in my F is loud, but not "whining" and I cannot hear it once the engine starts.  Maybe a bearing going out?

2) MP does seem off.  11.5 seems high, as well. But, I fly LOP so am used to seeing much lower (8.5 to 9.0 gph).  What do the power tables say for 25"/2400 in terms of ROP fuel flow?

3) Sorry, can't help.  I use a $75 El Cheapo non-ANR, non-Bluetooth, headset I bought 20 years ago

[ZuluZulu]

3) Before you chase too many leads, I would try forgetting (deleting) the Bluetooth device from within your iPhone settings, then re-pair it like you would any new device.  See if the issues continue, and if so, I might reach out to Bose at that point.

[PT20J]

I just had my M20J boost pump overhauled by Aeromotors ($450). It’s much quieter now though it wasn’t leaking and made pressure before. But, after 30 years, I figured it was time.

Sounds like a new manifold pressure gauge is in order.

First thing I would try is replacing the batteries in the headset. If that doesn’t fix it I would reset the software by telling the phone to forget the Bose. Then turn the phone off (not just locked; power it down) and restart it and the pair it with the Bose again.

[hammdo]

1) This might help:

-Don

[AndreiC]

Can MP gauges be sent out for repair/overhaul? Any recommended shops?

[AndreiC]

1 hour ago, MikeOH said:

2) MP does seem off.  11.5 seems high, as well. But, I fly LOP so am used to seeing much lower (8.5 to 9.0 gph).  What do the power tables say for 25"/2400 in terms of ROP fuel flow?

The POH does not answer this question. That's because 25.5"/2400 is 80% power, and the manual says that over 75% you should run full rich (hence a 14.9 gph fuel flow). Not sure where else to look.

[47U]

10 hours ago, AndreiC said:

2) I suspect more and more that my manifold pressure shows about 1.5” less than it should.

Inspect the lines and fittings between the engine and the gauge.  A 40+ year old hose could easily be sucking air and reducing the vacuum reading at the gauge.

[AndreiC]

7 minutes ago, 47U said:

Inspect the lines and fittings between the engine and the gauge.  A 40+ year old hose could easily be sucking air and reducing the vacuum reading at the gauge.

But then why would the gauge show wrong with the engine off?

[Jsno]

Sounds like time for your pump to be overhauled.  Also you manifold pressure gauge needs repaired.  Consolidated instruments in Teterboro repaired mine.  They found some corrosion in it. Or you can spend more and install an electronic engine monitor with MP.

[47U]

1 hour ago, AndreiC said:

But then why would the gauge show wrong with the engine off?

Valid point, but gauges don’t always fail in a linear fashion.  Look at the plot on your last altimeter certification.  The error rate likely wanders around and the error could be on the high (or low) side at various altitudes.  

After shutdown, if you tap (gently) on the glass, does the needle move?

[PT20J]

Manifold pressure gauges do become inaccurate and, in my experience, they always read low.

I used to fly float Beavers for a Part-135 operator. Every year some pilot would remark that a particular airplane was sure a lot faster than the others. We all used 28"/1900 rpm for cruise. I asked if it seemed to burn more fuel and invariably the pilot would admit that it did. At the end of the day, I would check the manifold pressure gauge on the "fast" airplane and find it reading about 1.5 inches low. After the service department replaced the gauge, the pilot would complain that something happened because now the airplane wasn't fast anymore.

Skip

[AndreiC]

7 hours ago, 47U said:

Valid point, but gauges don’t always fail in a linear fashion.  Look at the plot on your last altimeter certification.  The error rate likely wanders around and the error could be on the high (or low) side at various altitudes.  

After shutdown, if you tap (gently) on the glass, does the needle move?

But the error rate is quite small on the altimeter. We're talking 20-30 feet. Here we are talking 1500 feet of disparity (1.5"). Tapping the gauge does nothing.

[47U]

2 hours ago, AndreiC said:

Tapping the gauge does nothing.

Thank you for that reply.  I was trying to illustrate a possible error presentation in aneroid instruments, obviously I did a poor job.

I would refer you to Skip’s reply above.  

[Utah20Gflyer]

My fuel pump is loud enough I can hear it with the engine idling, but a slight  increase in rpm’s and I can’t hear it .  

[cferr59]

My Dukes pump is pretty loud. It started leaking and I had it overhauled at Aeromotors. It is equally loud afterwards. Can you post a recording of the sound? 

[Shadrach]

I can hear/feel my boost pump at idle with Bose A20s. It’s just barely perceptible but it is there. It’s always been loud, but it’s a lot quieter since overhaul.

not much to do about the MP gauge other then send it out or replace it .

I have always found the Bluetooth interface on the Bose to be unreliable. I struggle to pair my iPhone to my A20s? It so bad that I have given upon several occasions.

[N201MKTurbo]

I have a Weldon pump, it is louder than the Dukes pump it replaced.

Take your MP gauge to an instrument shop, they will hook it to their mercury column and they can tell if it is accurate in short order. They can fix it so it is dead on.