Strange noise midflight

[JerzyGeorge]

Couple of weeks ago while coming to land in a slide slip (left rudder and right aerlon) I did hear even through my noise cancelling headset strange noise something like structural break somewhere from left side . I did think of aerlon break or controls break but could not identified any problem plane behaved as usual with no probnlem . Since then I did performed thorough inspection of struts attachment points inside the wing all the contorols including elevator and vertical rudder fin and could not find anything . Can anyone suggest next step please . It could be something as simple as something moved in my luggage compartment behind me (I had during this flight tie up steel spikes there, but would be easy way out )I know similar incident on the glider when aerlon linkage disengaged mid flight with similar noise and pilot lost control on one aerlon managed however to get the glider to airstip and landed OK

 

 

[rick morawski]

Couple of weeks ago while coming to land in a slide slip (left rudder and right aerlon) I did hear even through my noise cancelling headset strange noise something like structural break somewhere from left side . I did think of aerlon break or controls break but could not identified any problem plane behaved as usual with no probnlem . Since then I did performed thorough inspection of struts attachment points inside the wing all the contorols including elevator and vertical rudder fin and could not find anything . Can anyone suggest next step please . It could be something as simple as something moved in my luggage compartment behind me (I had during this flight tie up steel spikes there, but would be easy way out )I know similar incident on the glider when aerlon linkage disengaged mid flight with similar noise and pilot lost control on one aerlon managed however to get the glider to airstip and landed OK

Maybe the flap lever disengaged(if you had them engaged). If the flap mechanism detent is not fully engaged in the slot it can let the flaps go with quite a bang. Happened to me once on landing round out, nearly soiled my undies. Now I always make sure I feel the release knob come up when setting the flaps.

 

Cheers

 

Rick

 

 

[SDQDI]

Also Jerzy make sure you do a full check of the engine.

 

I have a 914rotax and it only had 60 hours on the clock when I heard a noise that sounded exactly like a bolt or rivet breaking, it turned out to be the front throughbolt. The engine still ran completely fine but I noticed a loose nut on the right hand side of the engine and on the left side the bolt had come out with enough force to dent the cowl.

 

I don't know what engine you have so maybe this is irrelevant but thought it might be worth the post.

 

 

[JerzyGeorge]

Also Jerzy make sure you do a full check of the engine.I have a 914rotax and it only had 60 hours on the clock when I heard a noise that sounded exactly like a bolt or rivet breaking, it turned out to be the front throughbolt. The engine still ran completely fine but I noticed a loose nut on the right hand side of the engine and on the left side the bolt had come out with enough force to dent the cowl.

 

I don't know what engine you have so maybe this is irrelevant but thought it might be worth the post.

Thank you very much for that I will take a hard a long look around engine , but I had it running last weekend after rubber change in the carburettors and did not notice any problem.

 

Also Jerzy make sure you do a full check of the engine.I have a 914rotax and it only had 60 hours on the clock when I heard a noise that sounded exactly like a bolt or rivet breaking, it turned out to be the front throughbolt. The engine still ran completely fine but I noticed a loose nut on the right hand side of the engine and on the left side the bolt had come out with enough force to dent the cowl.

 

I don't know what engine you have so maybe this is irrelevant but thought it might be worth the post.

Maybe the flap lever disengaged(if you had them engaged). If the flap mechanism detent is not fully engaged in the slot it can let the flaps go with quite a bang. Happened to me once on landing round out, nearly soiled my undies. Now I always make sure I feel the release knob come up when setting the flaps.Cheers

Rick

Thanks Rick , I am pretty sure I was landing clean with no flaps , but now thinking about it I will not bet any money on it.

[Jaba-who]

What type of aircraft?

 

Jabs have had issues with the forward edge of control surfaces catching on the trailing edges of whatever structure they are attached to. Had a service bulletin to correct it.

 

Could a similar thing have happened in your case?

 

 

[Litespeed]

Also Jerzy make sure you do a full check of the engine.I have a 914rotax and it only had 60 hours on the clock when I heard a noise that sounded exactly like a bolt or rivet breaking, it turned out to be the front throughbolt. The engine still ran completely fine but I noticed a loose nut on the right hand side of the engine and on the left side the bolt had come out with enough force to dent the cowl.

 

I don't know what engine you have so maybe this is irrelevant but thought it might be worth the post.

Do not tell anybody- they will say you have a Jabiru engine, as we all know Rotax engines are perfect:stirrer:

 

 

[SDQDI]

Do not tell anybody- they will say you have a Jabiru engine, as we all know Rotax engines are perfect:stirrer:

Lol yeah but honestly it was only a thorough preflight that found it as it was still running flawlessly. From what I hear if you do a bolt in a jab you can tell very quickly! It was only the fact I had heard the noise that I looked long enough to find it, at first I was petrified that it was a wing bolt and spent a lot of time looking them over. Then once they all looked right I spent a long time preflighting before I was game to fly it again and was surprised when I found what it was.

 

 

[microman]

I also found a throughbolt missing on my Rotax 912 ULS - it hadn't caused any problem - no leaks etc - but I fairly quickly replaced it!

 

 

[Litespeed]

So that is two 9 series rotax motors throwing a throughbolt.

 

I would be worried, if they have done it once then will likely do it again.

 

Have these problems been reported?

 

Has anyone else had this happen?

 

 

[Garfly]

Jerzy, if your aircraft is a Savannah - or similar metal skinned type - could it be that one of your fuselage panels, or even one whole slab side, just 'oil-canned' momentarily pushed by the direct airflow of the forward slip? That is, did a section of skin just pop in - or out - a bit, making that characteristic 'oil-can' sound.

 

I, myself, was once chasing some scary noises apparently coming from somewhere in, or on, my aircraft until I finally concluded that the strange audio effect was being generated within the headset/intercom system itself. It was a strange sound, like someone rattling a large sheet of thin metal. (Not expected from a rag and tube job.) Actually, the sound was quite misleading; unlike any electronic glitch I'd ever heard. It sounded like an authentic real bad, real-world rattle.

 

I doubt that that's your problem though. You wrote that you heard a single bang which I guess is quite a different case.

 

 

[SDQDI]

So that is two 9 series rotax motors throwing a throughbolt.I would be worried, if they have done it once then will likely do it again.

 

Have these problems been reported?

 

Has anyone else had this happen?

Yes mine was reported. From what I could ascertain from bert flood it seems they had a couple do it but once replaced there was no further problems. Maybe just a couple of bad bolts? My original failure was at 60 odd hours and now am at 200, and from what I understood the other bolts that had failed also failed around that 50 hour mark.

 

 

[Guest Howard Hughes]

My suggestion is ditch the noise cancelling headset, too many scary noises!

 

 

[microman]

So that is two 9 series rotax motors throwing a throughbolt.I would be worried, if they have done it once then will likely do it again.

 

Have these problems been reported?

 

Has anyone else had this happen?

I think you are reading too much into this - in my case I believe the throughbolt had been loosened at some stage in order to accommodate a bracket - and after the bracket was removed it was never tightened. It actually impressed me that the Rotax engine is so robust that the loss of a throughbolt didn't cause a problem.

 

 

[JerzyGeorge]

Also Jerzy make sure you do a full check of the engine.I have a 914rotax and it only had 60 hours on the clock when I heard a noise that sounded exactly like a bolt or rivet breaking, it turned out to be the front throughbolt. The engine still ran completely fine but I noticed a loose nut on the right hand side of the engine and on the left side the bolt had come out with enough force to dent the cowl.

 

I don't know what engine you have so maybe this is irrelevant but thought it might be worth the post.

Excuse me my ignorance but which one is straight through bolt? I suspect the one holding cylinder head to the block

 

 

[JerzyGeorge]

My suggestion is ditch the noise cancelling headset, too many scary noises!

I am sold to my headset cannot fly without it it is Bose A20 and works the treat.

 

 

[fatmal]

Jerzy, if your aircraft is a Savannah - or similar metal skinned type - could it be that one of your fuselage panels, or even one whole slab side, just 'oil-canned' momentarily pushed by the direct airflow of the forward slip? That is, did a section of skin just pop in - or out - a bit, making that characteristic 'oil-can' sound.

This. I had a similar noise in an Allegro while side-slipping (not on purpose - I was new to type and couldn't keep it in balanced flight!). If I side-slipped on purpose, the bubble doors would pop from convex to concave - who needs a skid ball :-)

 

The popping noise I got was from skins on the tail, which, if you pushed on them would also go concave - making a scary noise in the process!

 

Wander about pushing on the skins, and see which ones 'pop'.

 

Mal.

 

 

[JerzyGeorge]

This. I had a similar noise in an Allegro while side-slipping (not on purpose - I was new to type and couldn't keep it in balanced flight!). If I side-slipped on purpose, the bubble doors would pop from convex to concave - who needs a skid ball :-)The popping noise I got was from skins on the tail, which, if you pushed on them would also go concave - making a scary noise in the process!

 

Wander about pushing on the skins, and see which ones 'pop'.

 

Mal.

Thanks a lot guys as usual I find different opinions very handy

 

 

[Litespeed]

I think you are reading too much into this - in my case I believe the throughbolt had been loosened at some stage in order to accommodate a bracket - and after the bracket was removed it was never tightened. It actually impressed me that the Rotax engine is so robust that the loss of a throughbolt didn't cause a problem.

Worrying about a bolt leaving your engine is not over reacting, irrespective how it happened. Unless you are 100% sure it was left loose- you have a potential problem, and it could be a fatal one.

 

Aircraft do not suffer fools.

 

 

[greybeard]

Aircraft do not suffer fools.

unlike forums

 

 

[SDQDI]

Excuse me my ignorance but which one is straight through bolt? I suspect the one holding cylinder head to the block

http://www.recreationalflying.com/threads/rotax-914-head-bolt-failure.118178/

That's a link to the thread I posted at the time, it has a couple of pictures showing the empty hole near the gearbox on the left side and the missing nut on the head on the right hand side.

 

 

[JerzyGeorge]

Thanks a lot for quality information , had a look at the photos and will check those bolts on mine. I was changing spark plugs over the weekend and did not notice anything missing , but will double check.

 

Jerzy

 

 

[facthunter]

Major bolts are not put on any engine just for the sake of it. Every one of them is needed. A sideslip has little effect on an engine, unless you were low on oil or something. I don't know what plane you have. Sideslipping puts a bit of load on the rudder and a bit of twist on the fuselage and of course you are using the ailerons but nothing near a large load. What speed are you sideslipping at.? I always do it fairly slow. Some boxy planes flap a bit in the fuselage panels when going sideways. It is always a good idea to check your controls under load, if you suspect anything may have changed. Get someone who knows what they are doing to hold them back a little and move through the full direction, bothways for any binding or play or "Give" slackness.. Nev

 

 

[eightyknots]

I think the most likely culprit is the oil-canning of the fuselage. This was quite a problem with Zenith CH-701 planes and, the Savannah being derived from this, may also suffer this under a sideslip load.

 

 

[JerzyGeorge]

I am pleased to confirm that everything has been checked twice all nuts and bolts including engine . Have not found any problems, found cabin roof panels where wings skin is jointed a bit flexible there , more on the left side , and this noise was put into this under certain air flow during side slip. Took it for a flight and could not fault it , did a gentle side slip and no noise , but wind was more steady this time and side slip no so agressive.

 

Thank you guys for all useful comments.