What's your most interesting story of mystery bumps, thumps or bangs?

[Desert Rat]

Theres another thread going right now where the poster is trying to diagnose a mystery thud sound that he's experiencing.

I didn't want hijack his thread, or minimize his issue, but it occurred to me that it might be fun and maybe even educational for folks to throw out an anecdote or two of their own experiences with mystery sounds and what they turned out be.

This is on my mind because yesterday I was flying a new 172 and at level off, I could hear a rattle even through my ANRs that sounded like somebody had left an empty soda can on top of a washing machine. Just a light thin metallic rattling sound. Powered back to 2500 rpm and it disappeared, powered up to 2700, it's back. Played around with power off steep descents, nope, definitely only happens at 2700 rpm, regardless of airspeed. Took my headset off and couldn't for the life of me identify where it was coming from other than maybe somewhere in the vicinity of the pilot seat or maybe behind the panel. Started touching wemacs, seat levers, overhead console, glare shield, radio rack, pretty much everything I could think of.

Finally determined that it was coming from the parking brake linkage

 

[mburch]

If the rubber seal at the wing root fairing comes loose in the right spot, the resulting rapid banging on the fuselage skin will momentarily make you think the engine just swallowed a valve!

 

[Weefle]

I have straps attached to the RV 10 doors to aid in pulling them down when seated in the front seats. Passenger closed the door and didn’t pull their strap in. Once we reached about 70kts the slapping sound startled me for a few seconds until I realized what it was. Made a circuit, landed pulled the strap in and continued on our way. I was worried my paint would take a beating but it didn’t.

I now close the passenger door from the outside before I get in.

K

 

[rmartingt]

Early on in Phase I (4th or 5th flight?) I started loading a little aft ballast to do the stability checks and all that. I decided to go ahead and install my smoke tank (just bolting it in) even though I had yet to do the hoses from the firewall to exhaust since that would give me a little bit of aft ballast.

So I got the tank installed and strapped down a small sandbag in the back, and went up.

Passing 2500ft I heard a BOOM! and a thump in my seat. I think I used a couple of "colorful metaphors" and immediately leveled off and pulled power to hold my current speed.

Ok, airplane is still flying, nothing looks funny on the engine instruments. Look out at the wings and as much as I can see of the tail. Everything looks fine.

Let's do a controllability check... Ok, no control issues. Controls feel good and nothing seems funny with the airplane.

Did I drag a brake and heat up/blow a tire? Can't see from here, brakes still feel good so I don't think I'm dumping fluid. If I did, nothing's going to help that now and I'm a little heavy with gas. Well, I might as well get some altitude and burn off some weight. So I keep climbing.

A little later... BOOM. Definitely feels like something in the cockpit but I can't figure out what.

Then again, boom. Waaaaiiit a minute... What's that rule about "think back to the last thing you changed"?

It's gotta be the smoke tank, cause a sandbag can't do that. But why is it doing that? Dad's doesn't do that, and I have the same tank he does. It must not be venting. Let me see if I can get the cap off... and no, can't get a good grip on the cap to remove it. Well, darn.

I go ahead and finish my planned testing, except I head back home instead of stopping at another airfield like I'd planned. Got some more booms on descent but I was expecting them.

After I got out, I was able to remove the cap. Turned out the vents on the cap had been plug-welded and my vented cap wasn't. I don't know if I'd gotten a non-vented one by mistake or I'd ordered the wrong kind expecting a different kind of installation, but either way, I re-opened the vent holes and have had no more booms.

Still haven't finished the smoke hoses to the injectors and need to get the wiring sorted out--for some reason I'm not getting power to the pump. It's on the to-do list for my imminent condition inspection...



Edit: I haven't experienced the wing root seal flapping on my airplane, but Dad has on his RV-6 and checking to make sure it's tucked in all the way became part of my preflight for his airplane.

 

[Brantel]

This one is legendary at least in my mind!

Brantel's Mystery Bang

 

[Freemasm]

Retractable overhead scoop vent on a Mooney. It is hinged and actuated via a Bowden cable. If said cable breaks, the door will swing back and hit the top fuse. It is sudden and very loud. Scared the crap out of me. Zero clues as to what had happened until after I landed.

 

[Brantel]

Early on in Phase I (4th or 5th flight?) I started loading a little aft ballast to do the stability checks and all that. I decided to go ahead and install my smoke tank (just bolting it in) even though I had yet to do the hoses from the firewall to exhaust since that would give me a little bit of aft ballast.

So I got the tank installed and strapped down a small sandbag in the back, and went up.

Passing 2500ft I heard a BOOM! and a thump in my seat. I think I used a couple of "colorful metaphors" and immediately leveled off and pulled power to hold my current speed.

Ok, airplane is still flying, nothing looks funny on the engine instruments. Look out at the wings and as much as I can see of the tail. Everything looks fine.

Let's do a controllability check... Ok, no control issues. Controls feel good and nothing seems funny with the airplane.

Did I drag a brake and heat up/blow a tire? Can't see from here, brakes still feel good so I don't think I'm dumping fluid. If I did, nothing's going to help that now and I'm a little heavy with gas. Well, I might as well get some altitude and burn off some weight. So I keep climbing.

A little later... BOOM. Definitely feels like something in the cockpit but I can't figure out what.

Then again, boom. Waaaaiiit a minute... What's that rule about "think back to the last thing you changed"?

It's gotta be the smoke tank, cause a sandbag can't do that. But why is it doing that? Dad's doesn't do that, and I have the same tank he does. It must not be venting. Let me see if I can get the cap off... and no, can't get a good grip on the cap to remove it. Well, darn.

I go ahead and finish my planned testing, except I head back home instead of stopping at another airfield like I'd planned. Got some more booms on descent but I was expecting them.

After I got out, I was able to remove the cap. Turned out the vents on the cap had been plug-welded and my vented cap wasn't. I don't know if I'd gotten a non-vented one by mistake or I'd ordered the wrong kind expecting a different kind of installation, but either way, I re-opened the vent holes and have had no more booms.

Still haven't finished the smoke hoses to the injectors and need to get the wiring sorted out--for some reason I'm not getting power to the pump. It's on the to-do list for my imminent condition inspection...

Almost the same as my story. The first time mine did this, I was leaving Oshkosh and was convinced I had collided with another aircraft.

 

[Ben Ellis]

Soon after getting my PPL, I was cruising in a 172 with the autopilot maintaining track and pitch. I started getting cold so I tried to open the heat but had a really hard time pulling the cable open. It finally opened and my hand slipped off the cable handle from all the pulling pressure, unbeknownst to me hitting the flaps lever, setting full flaps. I had noise cancellation headset on so I didn’t hear the flap motor working, but I did notice that my airspeed was quickly decreasing. I quickly discovered the flaps lever down and put the selector back to flaps up. As the flaps were working their way up, I heard a loud sound behind me and then the autopilot disengaged and the plane pitched down dramatically. My initial thought was that I lost a flap from being over speed, but thankfully I didn’t bend anything. I assume the sound was the autopilot pitch servo disengaging after reaching its limit. Very scary moment. Now I’m very careful anytime my hand gets anywhere near the flaps lever.

 

[Sam Buchanan]

This was definitely a thump!

 

[Roadjunkie1]

Early in my flying career, having learned mild aerobatics including loops in the Super Cub 90, I decided I needed to do some in the J-3. Got some altitude and dove near the 122 mph redline, smoothly pulled up as I smoothly applied full power. Things were looking great. As I came over the top with still good airspeed, started coming down the back side and heard a very loud BANG! Well, that was a little bit of a surprise that made me get a firm grip on the seat cushion! Finished the loop still uncertain where that had come from and actually looked back to see if the tail was still on! I believe there would have been other hints if that had parted company with the airplane!! Huh. Landed at a nearby airport and looked her over. Nothing. Had to think about what had caused that.

Flying back to home base, I figured it out: coming down the back side of a loop, if one is not practiced at looking at Ma Earth from that angle and not wanting to over rev the engine or overspeed the descent, smoothly reducing power might not be what one would do. I had gotten to the beginning of the back side and jerked the throttle closed from full throttle and had a nice little after-fire. Ha! My next loops showed much more control over the movement of the throttle! SMOOOOOOTH.......

 

[bjdecker]

Almost exactly as @mburch 's story.

My first RV-7, prior to paint, at some point during the initial Phase 1 --- "There I was..." flying over West Texas, middle of nowhere - near BFE, and I saw a structure on the ground that was worthy of closer inspection. I closed the throttle a bit, rolled into a split S and on the pull out I felt/heard the unmistakable sound of the outboard wing skin(s) ripping off :O

After remembering to breathe and regaining my composure, I felt the passenger side of the fuselage thrumping away -- the wing root rubber seal "blew out" and came off, whacking the daylights out of the fuselage. It's an attention getter, to be sure.

 

[Paul 5r4]

mburch mentioned in the second post about the wing root rubber... Happened to me! I had made a pass down the runway and when I pulled up
the last foot or so came out and was banging horribly against the fuse and top of the wing!!! My first thought was the right wheel pant had come loose and was banging. Dismissed that thought quickly because I just knew it would have separated completely and fallen. I had decided it had to be the wing root rubber seal.
One of the greatest benefits of building your own plane is you know ever detail intimately! My passenger that day was quite startled for sure.

 

[HFS]

Things That Go "Pop" In The Night ...

Mine happened about 10:30 one evening at 10,500 ft over the Pacific Ocean halfway between Catalina Island and Ventura. I was hauling my family & friends, in our B-58 Baron, back from a fun filled day in Disneyland, everybody but me asleep (and me almost, but not quite - Otto doing his job), when all of a sudden a (very) loud "BANG" from somewhere up front caused me very much reason for concern. I scanned all the instruments - nothing (apparently) amiss - but it sure woke me up. My wife became drowsily, partially awake ... About 5 minutes later, another one - "BANG". Now everybody is awake and holding one to each other for dear life and hoping (praying?) that we would make landfall before the next one - nobody likes the thought of landing in the water (especially at night!), right?

Well, we made Ventura with no more excitement, and proceeded to our destination, a private airport (92CA) in the Central San Joaquin Valley. Landed safely (big sigh of relief), deplaned the passengers and began to unload the baggage - still no clue as to what had just happened, until ...

I opened the nose baggage compartment and what to my wonderous eyes should appear, but one highly inflated mylar Mickey Mouse balloon & and two very tired (read flat) ones laying on the baggage compartment floor ...

That's my story and I'm stickin' to it ...

HFS

 

[rockyfatcat]

My ‘daily driver’ is a 1965 Alon Aircoupe. As an A&P. I discovered a in flight control cable failure on a Piper Cherokee. I decided as a precaution that I would replace my Alon’s 60 year old elevator cables at then next annual.

The manual for this aircraft has these cables tensioned to 160-200 foot pounds! My test of these cables prior to removal had them at 60 pounds.

Apparently the joke in industry is that the tension on the elevator cables keep the tail feathers attached.

Since replacement, when flying this aircraft, I can occasionally hear some rather large popping noises in flight. (It’ll really get you attention!)

Since the I have done 2 airframe inspections, and can only assume that after sitting for ten + years under-tensioned. Apparently things are just readjusting to the additional tension.

 

[planenutz]

If the rubber seal at the wing root fairing comes loose in the right spot, the resulting rapid banging on the fuselage skin will momentarily make you think the engine just swallowed a valve!

Now this one caught my attention for two reasons - first that it was posted at all; and secondly because it got more than a couple of "likes", suggesting others have experienced the problem as well (and followed up by two other stories from Brian and Paul).

I had this happen last year and while I'm not the worlds most experienced RV pilot, it was a first for me in almost 700 hours of flying RV-6's. I'd not heard of anyone else having had this problem before, either. It sure got our attention to the point where we made a PAN call to the local tower and arrived at the airport to a serenade of fire trucks. Thankfully it was a very easy fix and the fire crews appreciated the scones and muffins we bought them for their trouble.

Can I have a count of the number of people who have experienced this? Maybe instead of answering and highjacking the thread, just hit the "Like" button and we can count those instead. Up to you. But I'd be keen to know how prevelent this issue is and maybe we save somebody from wrecking their beautiful aircraft by making a wrong decision in flight.

 

[rv8ch]

I'd be keen to know how prevelent this issue is and maybe we save somebody from wrecking their beautiful aircraft by making a wrong decision in flight.

No idea how often this happens, but when it happened to me I knew exactly what it was thanks to reading here on VAF about someone else having this happen. I have some very stylish speed tape holding these in place now.

 

[Dugaru]

Things That Go "Pop" In The Night ...

Mine happened about 10:30 one evening at 10,500 ft over the Pacific Ocean halfway between Catalina Island and Ventura. I was hauling my family & friends, in our B-58 Baron, back from a fun filled day in Disneyland, everybody but me asleep (and me almost, but not quite - Otto doing his job), when all of a sudden a (very) loud "BANG" from somewhere up front caused me very much reason for concern. I scanned all the instruments - nothing (apparently) amiss - but it sure woke me up. My wife became drowsily, partially awake ... About 5 minutes later, another one - "BANG". Now everybody is awake and holding one to each other for dear life and hoping (praying?) that we would make landfall before the next one - nobody likes the thought of landing in the water (especially at night!), right?

Well, we made Ventura with no more excitement, and proceeded to our destination, a private airport (92CA) in the Central San Joaquin Valley. Landed safely (big sigh of relief), deplaned the passengers and began to unload the baggage - still no clue as to what had just happened, until ...

I opened the nose baggage compartment and what to my wonderous eyes should appear, but one highly inflated mylar Mickey Mouse balloon & and two very tired (read flat) ones laying on the baggage compartment floor ...

That's my story and I'm stickin' to it ...

HFS

Same basic idea: potato chip bag exploded in flight. Shockingly loud!

 

[RV7A Flyer]

Not my story, but one told to me by a friend who was into aerobatics. Before doing any maneuvers, he was taught to roll the plane inverted then back to check for loose items. He did so, and heard a loud BANG. Aborted and landed, and on inspection, they found a wrench in the aft section of the fuselage.

 

[Ralph Inkster]

I was flying my newly acquired RV6 home, landing for gas half way there. Climbing out from that airport I got a loud bang followed by a deafening screeching sound in the cockpit. A quick turn around to land & investigate the sound (& check my pants). I found the top windshield fiberglass fairing let loose & was vibrating in the airstream. Landed again, applied a generous amount of duct tape (necessary equipment to have when flying a new acquisition home). Had a great flight rest of the way home.

I won’t tell you about the other RV6 I bought & it’s flight home. It was another eventful flight…

 

[rbenua]

For the wing root fairing rubber piece, we had that happen on our RV-9 as well - first once or twice, just after takeoff. Made a precautionary landing, got out and found the problem, pushed it back in and reseated it. But it kept happening more frequently on the same side over the course of a few months and got really bad during my trip from CA to OSH last summer.

We ordered a new rubber channel and I replaced it soon afterward, and that was the first time I took a close look at both sides and noticed that they were cut to different lengths. The "good" side was shorter, and didn't overlap with the region where the wing root fairing overlaps the fuselage skin.


On the "bad" side, the wing root fairing is not present but you can see from the markings where the gasket had been banging on the skin that it extended all the way to the end of the metal fairing, including the overlap with the fuselage where it juts out to meet the bottom wing skin.



On the "good" side, with the fairing attached, you can see that the rubber is cut shorter, to match the end of the gap between the wing and the fuselage and not extend all the way to the end of the metal fairing piece.


I installed a new gasket and cut it to match the other wing and we've had no trouble since.