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The personality of the "beast" in your RV-When things change

Pmerems

Pmerems

Well Known Member
Advertiser
After we complete our RV’s and have the inaugural first flight we become very familiar with all the sounds our RV’s make. Even through with the wonderful technology of ANR headsets we can still hear the “personality” of our RV’s. One of the most important sounds is the engine.

One becomes accustom and intimately familiar to the variety of sounds that emanate from the beast in the front of your RV. When the beast’s personality changes you take notice real fast. Occasionally I experience a change and I hope there is someone with a similar experience and an explanation.

I have an RV-7A with an IO-360 with a Hartzell CS prop. I have 280 hours on my bird and am intimately familiar with the engine behavior and sounds. The other day I was flying along at 5.5K at approximately 125 KIAS at 2450 rpm with a 21 kt head wind. It was a site seeing flight around some local mountains. It was a little turbulent most likely do to wind shear it was too early for thermals (6:30). I started noticing a slight change in the tone of the engine. One might call it a frequency change. It grabbed my attention, I checked the engine instruments (EFIS/EMS) all good and I reduced power a bit to see if that would change the tone. It did but I still was a bit uneasy with the initial change. I continued on with my flight and changed directions and increased power. The rest of the flight was uneventful.

I am trying to figure out why the change in tone of the engine. I am wondering if the headwind could have been varying in direction and causing the tone change. Occasionally I have experienced a tone change when performing a run up with varying wind. Could this change in the tone while airborne be caused by the 21 kt headwind changing direction?

Any thoughts or experiences would be helpful.
 
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I think it is quite realistic to be just a wind change. We've seen obvious extremes of the same experience.
 
I've experienced it a few times as well. Little nuances like this keeps me alert and on my game.
 
Complete understand the intimate "relationship" with every sound I hear in my RV. Of coarse the tone changes are directly proportional to the severity of the terrain I am flying over.
 
Sounds and vibrations

I had a Cessna 150 many years back that seemed to have a vibration change. Some days it was smooth as silk??some days not. Some days I thought it was my imagination???..some days I thought it was real. It often resulted in me fidgeting in my seat.

Turned out to be a cracked back plate on the spinner.

As told to me by a friend, "your plane will almost always give you a warning". Sometimes the things we notice are the warnings.

Robert
 
Yes they will talk to you for sure.
turbulence, gusts will all cause sound tone changes.
I never understood folks that want to listen to music while they fly. Need to pay attention to your plane.
 
Change in Tone

As Tony Bengelis often said over lunch, "listen to your airplane, it is talking to you"'

I have had a change in tone and there was always a reason for it, perhaps not seen on instruments or felt in the airframe. One time I heard the change but did not see or feel the reason. Took the cowl off to find a broken exhaust just below the flange weld on #2. Another time it was a broken exhaust bracket where it exits the cowl.
 
Was not meaning to disparage anyone who listens to music. I just do not.

but you sure can feel/hear an RV much more than larger heavier planes, in my experience.
Was flying with my co-pilot one day and just saw a dark flick go over the windshield and a very slight vibration started. thought maybe we had hit a small bird. We landed at the nearest airport and found that a chunk of the fiberglass spinner departed. Shortly thereafter we ordered a Sensenitch prop (which we had already been planning to do) with aluminum spinner and put the wooden prop on the mantle where it works best.
 
Try flying the airplane with your feet on, then off of the floorboards. The sound and vibration change is enough to catch your attention until you recognize the cause.
 
Sounds and Vibrations

Kyle Boatright said:
Try flying the airplane with your feet on, then off of the floorboards. The sound and vibration change is enough to catch your attention until you recognize the cause.
Click to expand...

In my -8, if I take my feet off of the rudder pedals I definitely get a change in sound and vibration!

Skylor
RV-8
 
Pull the cowls and have a very careful look around with good lighting. Check your exhaust for cracks. Check the prop and spinner. Check the engine mount for cracks. Check for anything loose. Your ears are one of the best early warning systems you have.

Nobody knows your ship better than you. It concerned you enough to post this, so trust your instincts and get to the bottom of it.
 
No matter what brand of airplane I've had over the years, the engine sounds have always changed significantly as soon as I get a few miles off shore when heading to the Bahamas. :cool:

Every time...
 
Pmerems said:
After we complete our RV?s and have the inaugural first flight we become very familiar with all the sounds our RV?s make. Even through with the wonderful technology of ANR headsets we can still hear the ?personality? of our RV?s. One of the most important sounds is the engine.

One becomes accustom and intimately familiar to the variety of sounds that emanate from the beast in the front of your RV. When the beast?s personality changes you take notice real fast. Occasionally I experience a change and I hope there is someone with a similar experience and an explanation.

I have an RV-7A with an IO-360 with a Hartzell CS prop. I have 280 hours on my bird and am intimately familiar with the engine behavior and sounds. The other day I was flying along at 5.5K at approximately 125 KIAS at 2450 rpm with a 21 kt head wind. It was a site seeing flight around some local mountains. It was a little turbulent most likely do to wind shear it was too early for thermals (6:30). I started noticing a slight change in the tone of the engine. One might call it a frequency change. It grabbed my attention, I checked the engine instruments (EFIS/EMS) all good and I reduced power a bit to see if that would change the tone. It did but I still was a bit uneasy with the initial change. I continued on with my flight and changed directions and increased power. The rest of the flight was uneventful.

I am trying to figure out why the change in tone of the engine. I am wondering if the headwind could have been varying in direction and causing the tone change. Occasionally I have experienced a tone change when performing a run up with varying wind. Could this change in the tone while airborne be caused by the 21 kt headwind changing direction?

Any thoughts or experiences would be helpful.
Click to expand...

Exhaust hangars that have slipped or shifted in turbulence while the engine was pulled and pushed around can make quite a change in the sounds and vibration. Have a close look at the hangars, clamps, exhaust and clearance to hoses , motor mount, firewall, cowl exit etc.etc.
 
Pmerems said:
I am wondering if the headwind could have been varying in direction and causing the tone change. Occasionally I have experienced a tone change when performing a run up with varying wind. Could this change in the tone while airborne be caused by the 21 kt headwind changing direction?
Click to expand...

Other than a *momentary* change in wind (a gust), the airplane is flying *in the wind*...it doesn't know from which direction the wind is coming, headwind, crosswind, or tailwind.

A short gust or sudden change in direction could cause a *brief* change, I suppose...but not a prolonged one.
 
Arlen..

Arlen said:
No matter what brand of airplane I've had over the years, the engine sounds have always changed significantly as soon as I get a few miles off shore when heading to the Bahamas. :cool:

Every time...
Click to expand...

I think the phenomenon you speak of is called "auto-rough". It happens after dark as well...
 
Do you fly with an active noise reducing headset? I occasionally hear what sounds like a change in the tone of my engine (fixed pitch Piper Warrior) and the first thing I do is adjust my headset position. I have found that shifting the headset position can change the apparent noise (even the pitch of the sound) from the engine significantly.
 
Great suggestions

I will pull the cowl and spinner and inspect per the suggestions in the posts. I will be at Oshkosh (flying commercial) so I won't have time to inspect until I return. I will post whatever I uncover.
 
Similar to F1R's experience - we noticed a change in pitch (as in musical pitch), and when we investigated and pulled the cowl, it turned out to be a loose exhaust hanger. Wishing you swift and minor troubleshooting...!
 
My old Cherokee 140 was notorious for engine/propeller sound changes when encountering wind changes while in flight. It was a natural phenominon for that plane. My RV6 behaves similar, but not to the extent the Cherokee did it.
 
Similar to the exhaust stories of others, I had the oil pan brackets for the Vetterman exhaust break 3 or 4 times in the first 200 flight hrs. It caused a slight but noticeable sound change when one broke. The issue was resolved by fabricating "wider" brackets that encompassed 2 oil pan bolts each. Essentially tripled the width of the bend where the breaks were occurring. At 400hrs total with no further failures.
 
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One plug fouling can give an engine note change. I had an exhaust break in the -4 once and although subtle you sort of know whats happened. Flying into different and distinctive air masses will give a sound change. A constantly talking wife who runs out of things to say also has an effect. Low fuel, over water, at night, bad terrain, above full cloud cover and temporarily uncertain of position ( pre-GPS) all contribute to any hidden phobias.
 
Plugs

Changed the plugs in my old Toyota a while back, the antenna doesn't vibrate anymore. I suspect the old Lycoming behaves in a similar fashion when worn plugs are cleaned/gapped/replaced.
 
Had the exact same thing happen to me a year ago. I was flying from Atlanta to Fredericksburg VA east of and parallel to the Appalachian Mountains. I noted both a sight engine sound change and TAS variations of 5 knots or so. Somewhat disconcerting.
Discussing this with a senior pilot at the airpark he educated me on "mountain wave".

Carl
 
My engine music changed when I got a crack in the exit air ramp on my -8. I pulled the whole thing off, fabricated a new one out of SS, and then no more buzzing or foot vibration with the new stiffer (albeit heavier) material down there.
 
Update

After returning from Oshkosh and a business trip to the east coast I finally had time to pull the cowl to take a look. I inspected everything that people had suggested in the thread. No exhaust cracks, no exhaust flange cracks, no exhaust hanger failures, no engine mount cracks, no spinner backplate cracks. Everything appears in order.

So while I had the cowl off I changed the oil and replaced a flaky #1 CHT probe.

I will inspect again before I reinstall the cowl.

Hopefully it was the wind that caused the tonal change I heard. If not its a Gremlin....:rolleyes:
 
Wind

I've noticed changes in the tones when the wind shifts. Also, I've noticed chgs when I shift my head. Get those shifts down & chgs in tone become more meaningful.
 
After reading NM Doug's note. Next time I went to the hanger I reached under the plane and grabbed the exhaust pipes. sure enough one was loose. took off the cowl to check and found the bolt had fallen out.
I had just done a BFR and the instructor had talked like a magpie the whole time, but I had thought that I noticed a different noise, underneath all of his noise.
And I had even specifically looked at the exhaust hangers before that flight.
Note to self, again. always listen to your plane.
 
chazking said:
I've noticed changes in the tones when the wind shifts. Also, I've noticed chgs when I shift my head. Get those shifts down & chgs in tone become more meaningful.
Click to expand...

I've noticed that too...

I wonder if there is some directionality to our noise-cancelling headsets?
 
Update and root cause

I flew the RV the other weekend and was able to get the tonal change some of the time but wasn't able to determine the cause. Thought it had to do with possibly running lean of peak because it seemed to occur when I was LOP and descending slowly.

But good news.:)

This past Saturday I flew again and really tried to focus on finding out what was going on. I climbed to altitude and set up my power setting the same as I had before and pushed the nose over. Not an aggressive decent maybe 200 ft/min. And nothing changed. It was a bit hot and I noticed the passenger vent was partially open. I have Van's stock plastic vents. I opened the vent and I noticed a tonal change. I leveled off and decided to open and close the vents a little to see what happens. I was able to reproduce the tonal change instantly.

I also noticed that depending on my airspeed (level flight or descending) the passenger vent would not stay in one position, it would open or close on its own depending on the airspeed.

So what I believe was happening was that if the vents are open a certain amount and the passenger vent opening automatically adjusts to the airspeed , a tonal change will occur.

So there is nothing wrong with my engine, prop, airframe, just a airspeed operated vent.

I have been considering upgrading my vents for many years, now I think it is time.

I hope someone learns from my experience.

Thanks for the help.
 
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