Would you fly with unknown noise on startup

C

Code90

Pre-takeoff checklist
Joined
Feb 7, 2014
Messages
142
Location
Mt Pleasant, SC
Display Name
Display name:
Code90
Mostly this is a question about what most others would do. I'm still a low time pilot and seem to learn something new daily with the plane.

Recently loaded the plane for a trip with a friend. All ready to go... Started without any problem, but then had a new whining noise. "Hmm. Never heard that before." Sounded like was just on other side of the firewall. Everything else read perfectly normal with gauges. It would whine as I increased RPM. Would stop if brought back to idle. Co-owner outside plane could not hear it and said engine sounded normal.

Our field has no mechanic. We fly 15 min flight to the mechanic at a large airport. The question is, would you fly the plane without knowing what the noise was? How do you decide?
 
Code90 said:
Mostly this is a question about what most others would do. I'm still a low time pilot and seem to learn something new daily with the plane.

Recently loaded the plane for a trip with a friend. All ready to go... Started without any problem, but then had a new whining noise. "Hmm. Never heard that before." Sounded like was just on other side of the firewall. Everything else read perfectly normal with gauges. It would whine as I increased RPM. Would stop if brought back to idle. Co-owner outside plane could not hear it and said engine sounded normal.

Our field has no mechanic. We fly 15 min flight to the mechanic at a large airport. The question is, would you fly the plane without knowing what the noise was? How do you decide?
Click to expand...
Did you hear this in your head set? or?

I get the impression it is avionics,
 
Code90 said:
Mostly this is a question about what most others would do. I'm still a low time pilot and seem to learn something new daily with the plane.

Recently loaded the plane for a trip with a friend. All ready to go... Started without any problem, but then had a new whining noise. "Hmm. Never heard that before." Sounded like was just on other side of the firewall. Everything else read perfectly normal with gauges. It would whine as I increased RPM. Would stop if brought back to idle. Co-owner outside plane could not hear it and said engine sounded normal.

Our field has no mechanic. We fly 15 min flight to the mechanic at a large airport. The question is, would you fly the plane without knowing what the noise was? How do you decide?
Click to expand...


NOPE....

I would find the origin of the noise before that plane left the ground.... IMHO..
 
Whining noise under the cowl? No. That's not right. Not many things under there to do that. Most of them would be metal on metal. No thanks.

"Standard" alternator whine in the headset, yes. Happens all the time in improper avionics installs or ones with problems.
 
Wanted to hear other options. I have been flying this plane for going on two years. Noise was new.

I ended up flying the plane to the mechanic. I sent my passenger ahead by car. I ran it up and then ran it down the runway to see if it was generating power consistently. No problems there. At higher RPM, the noise was hard, if not impossible, to hear. I took off and flew to the neighboring airport (stayed over open / noncongested areas). On the way there, the "Vac" light came on and the vacuum gage went to zero. The AI crumped (predictably) a few minutes later. Backup vacuum fixed the issues and landed without incident on a severe clear VFR day. The problem was obvious at that point. Mechanic was good enough to replace the vacuum pump and have us on our way in a hour and a half.

I thought long and hard about making the flight. In retrospect, this was probably the most risky thing I have done as a pilot. It worked out in the end, but still... I had talked to other local guys that said, " all the gages looked good, you tested the motor to some extent, you were careful, no problem." Curious as to what the armchair quarterbacks would say here.
 
You weren't IFR so I wouldn't consider the vac failure risky, but you didn't know that at the time. I would not have made the flight. That's what mechanics and ferry permits are for.

That said...glad it worked out!


Sent from my iPhone using Tapatalk
 
Last time I had a bad whine in the audio it was because the charging system had crumped. You bet I'd check it out.

The oddest one was once I took off out of IAD headed for VKX one morning. I kept hearing this "clanging noise". I'd pull my lightspeed's off my ears to try to get a better listen but couldn't hear it. I'd put the headphones back on and the clank was there. On landing we found the exhaust pipe had broken and was banging back and forth. Never let anybody tell you that a ANR headset is going to make it hard to hear engine malfunctions.
 
I learned that lesson long ago. Started up to return home and it sounded "different". Couldn't put my finger on it. Shut down and tried again - same result - nothing really wrong, but just a nagging thought. Figured I'd fly home and let my mechanic look at it. The engine blew the rest of the valve thankfully at 9000 feet. Got a new cylinder and installed egt/cht probes on all cylinders.
 
Code90 said:
Wanted to hear other options. .
Click to expand...

Well geez, ya told us before the rest of us could take a guess! I would've suspected interference maybe, avionics/cable related. Usually the sound will increase as RPM increases, cabin speaker or headset. Glad it worked out.
 
Code90 said:
Mostly this is a question about what most others would do. I'm still a low time pilot and seem to learn something new daily with the plane.

Recently loaded the plane for a trip with a friend. All ready to go... Started without any problem, but then had a new whining noise. "Hmm. Never heard that before." Sounded like was just on other side of the firewall. Everything else read perfectly normal with gauges. It would whine as I increased RPM. Would stop if brought back to idle. Co-owner outside plane could not hear it and said engine sounded normal.

Our field has no mechanic. We fly 15 min flight to the mechanic at a large airport. The question is, would you fly the plane without knowing what the noise was? How do you decide?
Click to expand...

Would I fly without knowing? NO

How did I decide? Survival instinct
 
Code90 said:
Wanted to hear other options. I have been flying this plane for going on two years. Noise was new.

I ended up flying the plane to the mechanic. I sent my passenger ahead by car. I ran it up and then ran it down the runway to see if it was generating power consistently. No problems there. At higher RPM, the noise was hard, if not impossible, to hear. I took off and flew to the neighboring airport (stayed over open / noncongested areas). On the way there, the "Vac" light came on and the vacuum gage went to zero. The AI crumped (predictably) a few minutes later. Backup vacuum fixed the issues and landed without incident on a severe clear VFR day. The problem was obvious at that point. Mechanic was good enough to replace the vacuum pump and have us on our way in a hour and a half.

I thought long and hard about making the flight. In retrospect, this was probably the most risky thing I have done as a pilot. It worked out in the end, but still... I had talked to other local guys that said, " all the gages looked good, you tested the motor to some extent, you were careful, no problem." Curious as to what the armchair quarterbacks would say here.
Click to expand...

After responding to your post, replying and then reading the rest of the thread, I think you handled it responsibly.
 
I would abort the flight before take off and have a closer look at it. Not worth taking a risk even if the root cause turns out to be benign issue.
 
Blueangel said:
I would abort the flight before take off and have a closer look at it. Not worth taking a risk even if the root cause turns out to be benign issue.
Click to expand...

That is obviously The Most Conservative Action, and the right thing to do.

But the psychological imperative to get in the air is a very strong one, and insidiously hard to resist.

DAMHIK!
 
FastEddie, are you familiar w/ the Blue Ridge airport? When I lived the I don't think it was there, or I just didn't know about it.
 
Would I have flown? Probably. You did, right? Some noises are scarier than others but the only catastrophic failures I'm familiar with gave no warning while funny noises have never developed into a threatening problem but led to simple fixes. Armchair opinions aren't worth the bandwidth they consume. The pilot in the seat is the only one that matters.
 
mscard88 said:
FastEddie, are you familiar w/ the Blue Ridge airport? When I lived the I don't think it was there, or I just didn't know about it.
Click to expand...

Blue Ridge Skyport, 57GA, is the old Sugar Creek Dragstrip! The Sugar Creek Raceway - dirt oval - is adjacent.

Interesting due to high trees surrounding it, narrowness and uphill slope on RWY1.

Had my Cirrus, and then my Sky Arrow based there. A few of my Sky Arrow takeoffs and landings are up on YouTube, user fastereddieb.
 
I see. When did it become an aerodrome? I moved from Blue Ridge in 2005.
 
Cool, looked at your video. Man a lot of trees for sure. Looks like they converted it into a nice airport. Public or Private airport?
 
Code90 said:
Wanted to hear other options. I have been flying this plane for going on two years. Noise was new.

I ended up flying the plane to the mechanic. I sent my passenger ahead by car. I ran it up and then ran it down the runway to see if it was generating power consistently. No problems there. At higher RPM, the noise was hard, if not impossible, to hear. I took off and flew to the neighboring airport (stayed over open / noncongested areas). On the way there, the "Vac" light came on and the vacuum gage went to zero. The AI crumped (predictably) a few minutes later. Backup vacuum fixed the issues and landed without incident on a severe clear VFR day. The problem was obvious at that point. Mechanic was good enough to replace the vacuum pump and have us on our way in a hour and a half.

I thought long and hard about making the flight. In retrospect, this was probably the most risky thing I have done as a pilot. It worked out in the end, but still... I had talked to other local guys that said, " all the gages looked good, you tested the motor to some extent, you were careful, no problem." Curious as to what the armchair quarterbacks would say here.
Click to expand...

You had good instincts, you thought something was wrong and there was something wrong. Trust those instincts.
 
Code90 said:
...The question is, would you fly the plane without knowing what the noise was? How do you decide?
Click to expand...
As others have said, your description does not tell us whether this was noise in your headphones, hence most likely alternator whine, or whether the noise was audible with headphones off.

If alternator whine and not super-loud, and I was not planning to fly in IMC I would fly. I would see my risk as primarily going NORDO rather than falling out of the sky. And these days, with GPS equipped tablets in most cockpits NORDO is really not a big deal.

If it was indeed coming from the firewall area I would not fly. But as others have said, there is not much forward of the firewall that could make a whining noise. It could possibly be a gyro bearing dying but I don't know that one could identify that and separate it from some other mechanical whining.

I guess I'd have to have been there to say for sure what I would do.
 
Let's review the evidence.

There was a new "whining" noise, apparently from the engine compartment.

The vacuum pump failed during the flight and was replaced at the destination.

Duh.

Vacuum pumps have little carbon vanes that run in slots in a carbon rotor. The rotor spins at considerable speed and that pump will make a buzzing sound that is normally inaudible over all the other racket an engine and propeller make. When the pump gets worn it gets louder, partly because the vanes are too short and are cocking in their slots and starting to jam, and there are often little ripples worn into the rotor bore than add to the noise and wear and general misery. Soon a vane sticks in a serious way and it breaks itself or the rotor and the plastic drive coupling fails to save the engine's accessory drive gears. No vacuum. And no more whining noise.

For a number of years now both Rapco and Tempest have been selling vacuum pumps with vane wear inspection ports built into them. First inspection at 500 or 600 hours of pump time, and every 100 hours after that, and pump failures become essentially nonexistent. Why people still buy non-inspectable pumps and run them until they break is beyond me. Even if you can't be bothered to track component times, it takes maybe five minutes to check it at annual.

8061.jpg


pump-failure-in.jpg
 
FWIW, many accident link chains start with a "I had a bad feeling about this".

If something doesn't feel right to you, it is time to investigate and find the risk and mitigate it. Or not fly. Or take your chances. Everybody has different priorities. And every flight happens during different circumstances.
 
But it could also be the starter Bendix drive hanging up such that the starter is back-driven to ridiculous rpms by the engine.
 
nrpetersen said:
But it could also be the starter Bendix drive hanging up such that the starter is back-driven to ridiculous rpms by the engine.
Click to expand...

There's a one-way clutch in the starter that prevents the engine from driving it. The starter drive gear will spin fast, but not the starter itself. Still, it will blow up the bendix, probably long before takeoff. Or rip the gears off the flywheel.

And if the starter contactor sticks shut, the starter will keep running after start and get hot enough to burn out or throw the commutator segments. A simple check of the ammeter after start will reveal a hung starter, since the battery is being drained far faster than the alternator can resupply it. The ammeter will be maxed out on the charge side.
 
Dan Thomas said:
There's a one-way clutch in the starter that prevents the engine from driving it. The starter drive gear will spin fast, but not the starter itself. Still, it will blow up the bendix, probably long before takeoff. Or rip the gears off the flywheel.

And if the starter contactor sticks shut, the starter will keep running after start and get hot enough to burn out or throw the commutator segments. A simple check of the ammeter after start will reveal a hung starter, since the battery is being drained far faster than the alternator can resupply it. The ammeter will be maxed out on the charge side.
Click to expand...
But would you really want to fly an airplane with all this going on?
 
flyingron said:
The oddest one was once I took off out of IAD headed for VKX one morning. I kept hearing this "clanging noise". I'd pull my lightspeed's off my ears to try to get a better listen but couldn't hear it. I'd put the headphones back on and the clank was there. On landing we found the exhaust pipe had broken and was banging back and forth. Never let anybody tell you that a ANR headset is going to make it hard to hear engine malfunctions.
Click to expand...

For sure.

We took off and immediately heard a sound coming from the empennage that sound like a rhythmic flapping banging sound. I took my ANR headset off, and -- under the parabolic reflector we call a "canopy" -- I could not hear anything. Just a roar.

Put the ANR back on, and there it was again. WTH?

It turned out to be a little piece of stick-on foam that I had put under the canopy to seal out a cold draft. It was exposed by about 3", and was frantically beating itself against the fuselage.

ANR is terrific.
 
I would not. I would figure out what the noise is. There are times I have flown with problems to a mechanic but only on advice of experience people and after figuring out exactly what the issue was (and that it wasn't going to cause a forced landing between me and the destination). Anomalies always get my attention. Usually they turn out to be minor, but not always.
 
You must log in or register to reply here.
Back
Top