Caution : Older type 2-blade Bolly prop hubs.

[facthunter]

There has to be a gap as purchase on the blade is what you are after. Anyone with experience would know the torque is critical. Go by the book. Nylock nuts make it a bit more difficult but it needs locking. Nev

 

 

[facthunter]

I think it has done a fairly good life. Make everything last forever and it will be too heavy if you do it everywhere.Nev

 

 

[Guest Maj Millard]

I have no desire to damage the Bolly name....this is an older model and they have probabily improved on their later current model which looks much beefier. On a safety note though there are still a lot of these out there in service and if one can crack then so can another. If we only find one more cracked out there like this one, we will have saved somebody's bacon by making this post. As always my intention is safety related only.

 

 

[Head in the clouds]

I always torque per manufacturers instructions....don't about other people in the past. Pilot owner could have also re torqued during past 100hrs. Internal crack is much older.

Yes, please don't think my earlier post was suggesting anything otherwise Maj. Your reputation for good and accurate work spreads far and wide. My comments related to whatever may have happened elsewhere in the past.

 

 

[facthunter]

All props are highly stressed items subject to unusual loads. Centrifugal, Gyroscopic bending, drive harmonics and some people even push their plane around by them. Wood is probably the safest type but has it's limitations. Everything needs inspection. A "nick" in a metal one can make it crack very quickly no matter how big it is. You inspect them every flight if you care and dress the mark out if it's significant. Get someone who knows how if you don't. Nev

 

 

[Cosmick]

Bolly now are different from Bolly then. My dealings and everyone else i'm aware of are extremely happy with after sales service, very approachable. One thing that came to light some years back was that torque settings for some props were given in inch pounds i.e. an ivo was 96 inch lbs (8 ft lbs) but in some cases were tightened to 96 ft lbs which eventually lead to a departing blade.

 

 

[facthunter]

On the prop shown, I would think it would break the fitting or bolt. That size bolt won't take 96 ft/lbs but it would certainly take more than 8 ft/lbs. Many people have almost no feel for torquing .You see it on motorcycles all the time, (and wheel nuts on cars etc) even the bloody sump drain plug. Use a calibrated tension wrench, and for the lighter settings use the proper size, and clean the threads and apply lubricant IF SPECIFIED..

 

These days it is hard to trust other people unless you know they are thorough and know their business so the answer may be to educate your self a bit more, so you can ask the right questions at least.. Don't go for the cheapest. How would that be the correct gauge of suitability?

 

I like Maj's work and Ultralight's coverage of the Savannha ? rebuild was good stuff for consideration on this site. There are others too, but more of this should be in. the magazine as not a high % of the total members are here. Pay for good articles and information if that's needed. Nev

 

 

[jetjr]

Maj, i know your intention is safety, no doubt

 

But if you find out from maker that model hub had 500 hr life or they had seen the issue before with over torquing or recalled them all. Perhaps this was early one off prototype.

 

That would surely change the picture and could affect the reaction to the problem

 

Also could be one in a long line of issues and that too would be good to know

 

 

[jetjr]

Spoke to Bolly today, didnt know anything about the problem.

 

Seems its likely to be an old hub, made from lower grade materials. Previously much of the products made overseas

 

Its possible "phonebook" corrosion and splitting

 

New hubs are different design and material and anodized

 

Call and talk to them, might not be as helpful knowing its been posted online without even contcting them

 

 

[Guest Maj Millard]

Spoke to Bolly today, didnt know anything about the problem.Seems its likely to be an old hub, made from lower grade materials. Previously much of the products made overseas

Its possible "phonebook" corrosion and splitting

 

New hubs are different design and material and anodized

 

Call and talk to them, might not be as helpful knowing its been posted online without even contcting them

As required by the ops manual I have filed a defect report with the Tech manager. I'm sure he will contact Bolly if he requires. I'm sure he'll also issue a Service notice if he feels there could be more out there in service with any problems, as this one was.

He is in a better position to respond more correctly to this problem if there is one, than I am individually.

 

I have been in the aviation maintenance business for over 45 years and have never heard of Phonebook corrosion. Do they mean intergranular ?......

 

If Bolly feels that the earlier hubs were built of inferior aluminium and that they could crack or corrode, than I feel it would certainly be in their interest to issue their own Service notice advising users of same, or even issue a recall on these hubs if they feel is necessary.

 

 

[jetjr]

Report to tech manager as you should. He will assess it and tke whatever action needed.

 

Re corrosion i dont know, possibly, they only had my description.

 

These were made before the current owners were involved. Not sure how much responsibility they have to take for someone elses work especially so long ago.

 

Comes back to cost and support. If manufacturers are expected to take 10+ years responsibility on goods sold the prices will be much more and we are headed down certification path

 

My point is trial and punishment by forum is highly damging and often done without all the required info

 

 

[Guest Maj Millard]

Report to tech manager as you should. He will assess it and tke whatever action needed.Re corrosion i dont know, possibly, they only had my description.

These were made before the current owners were involved. Not sure how much responsibility they have to take for someone elses work especially so long ago.

 

Comes back to cost and support. If manufacturers are expected to take 10+ years responsibility on goods sold the prices will be much more and we are headed down certification path

 

My point is trial and punishment by forum is highly damging and often done without all the required info

Jetjr......The cracks speak for themselves as you can see from the photos. Bolly still readily sells new blades to be fitted to these older hubs, and they still carry the Bolly name, as was the case with this one. As previously stated the ball is in Bollys' court to take care of their own brand image. They inherited these older products and knew there were many still in service when they purchased the company. In a court of law they would have a big task proving no responsibility for this product. I don't recall them ever saying they no longer supported the product.

 

 

[Guest Maj Millard]

Further, the boys at Bolly should probability be very greatfull that these old beedy experienced engineer eyes actually detected the cracks and the dangerous defect. The next stage could well have been a very spectacular and dangerous failure of that part which would have caused them way more drama than the current defect report may.

 

My concern is how many are still out there with a similar fault, it's Bollys job to answer that question, not mine.

 

 

[farri]

Damned if you do, Damned if you don`t!!!

 

Frank.

 

 

[facthunter]

And everybody keep carefully inspecting ALL prop blades. Nev

 

 

[Guest Maj Millard]

Damned if you do, Damned if you don`t!!!Frank.

Frank, there was a time in the past when I didn't, and people got hurt........I don't operate that way anymore...

 

 

[jetjr]

Everyone should be inspecting hubs, props are pretty important

 

Your idea that something non certified, old and apparantly with no service records is somehow going to be legally supported isnt right

 

You cant shame or force companies to provide support

 

No wonder fewer are prepared to invest life savings into aviation manufacture if users have this attitude

 

 

[Head in the clouds]

No wonder fewer are prepared to invest life savings into aviation manufacture if users have this attitude

I quite agree. I just bought a brand new three blader from Bolly with oversize hub to swing 74". It doesn't come with any form of warranty or guarantees other than statutory ones plus whatever Craig and Peter would reasonably provide. Nonetheless I'm quite confident that if a defect was found they would make good. However had I allowed it to become old, corroded and clearly poorly maintained, would it be reasonable of me to expect them to keep on making good forever? Of course not.

 

I mean - the hub that is the subject of this thread has no maintenance records, no-one knows remotely how old it is, who last torqued it, or to what values, let alone who did so for the last ten or fifteen years. Do people seriously think the new owners should be held responsible for this? These are Experimental aircraft parts and consequently they are way cheaper than Certificated aircraft parts. Try buying a certificated 74" CF adjustable pitch three blader for $1800, it'd be more like $10K I would surmise.

 

And then it would be time-lifed and hours-lifed so you'd have to chuck it away at probably half the hours for which the one in this thread provided sterling service. Careful what you wish for and all that ...

 

When props and engines and other critical components get old in Experimental aircraft it doesn't mean we should just keep using them just because there aren't particular requirements to retire them. It's up to us to make good and subjective decisions about the condition of our components, and when it's time, replace them ... we shouldn't be waiting for them to fail to give us a clue about their condition - or expecting the factory to make good after we've had years of good use out of them.

 

 

[facthunter]

Like many aircraft items, props get variable usage. People push the plane by them and they get bumped into Rocks hit them and they are subject to high loads and vibration. When a blade removes itself, the imbalance is so high often the engine leaves the aircraft or damages the mounts allowing the prop to contact the fuselage in Pushers which can cause separation of the tail. If you can't develop an inspection process for your prop, I would wonder how you manage other aspects of your flying. It's BASIC stuff. Even CERTIFIED props can fail. In a metal prop it only takes a nick by a stone in the leading edge, which can be the start of a crack if not suitably dressed out. Nev

 

 

[Guest Maj Millard]

This prop was being inspected regularly, and it has been removed from service. It was fitted with two new blades 200 hours ago, and re torqued per Bollys figures 100hrs ago. There were no cracks evident then.

 

 

[facthunter]

My comments are general Maj. You have done the correct thing and newer versions are probably better. I want to see people making stuff for aviation and not frightened off for fear of litigation. The OWNER /operator is responsible for the condition of the aircraft. Inspections should not be cursory or just a casual walk around to make it look as if you are doing something.. It's an aeroplane and they don't forgive much, when things go wrong. Nev

 

 

[jetjr]

So is the owner happy he saved the $500 by not buying a whole assembly?

 

Id be surprised if Bolly didnt recommend it.

 

As HITC says just because a component can be reused doesnt mean it should. Similar for self maintainers.

 

 

[facthunter]

If a recommendation is replace at X hours and some get 2X that doesn't disprove the first figure which is based on safety considerations and repair is often more expensive in the long run than replacement. You have to consider and assess the value of the whole investment when spending money on any major repair. OR when considering purchase of a plane that may require a lot of work, even if you get it really cheap. Nev

 

 

[Riley]

If a recommendation is replace at X hours and some get 2X that doesn't disprove the first figure which is based on safety considerations and repair is often more expensive in the long run than replacement. You have to consider and assess the value of the whole investment when spending money on any major repair. OR when considering purchase of a plane that may require a lot of work, even if you get it really cheap. Nev

"or when considering purchase of a plane that may require a lot of work, even if you get it really cheap" How true Nev, how very true!!!

 

 

[Guest Maj Millard]

All....I am happy to report tonight that Bolly has offered to fully replace the damaged hub with a new unit for the owner. It appears that the cracked hub in question was likely manufactured by the previous proprietors of Bolly Props, and that the material may have been sub-standard possibly originating from a foreign country.

 

For the current owners of Bolly Props to stand by their company name and replace a product not directly produced by them, is to me very admirable, and I must take my hat off to Peter and his team for the kind offer of replacement.

 

Also my thanks to the RAA Tech and Safety teams ( Darren Barnfield, Katie Jenkins) for assisting with this matter, and supporting my defect report, and my customer.

 

Ross Millard. L2.