AAIB Bulletin March 2010

[212man]

Air Accidents Investigation: March 2010

[61 Lafite]

The Rotorway failed (probably) due to poor casting of an aluminium camshaft drive gear in the engine.

As if Rotorway owners didn't already have enough to worry about! But well done for getting it down and walking away!

Lafite

[wallism]

As you say, nicely done by the pilot. I am surprised that the CAA didn't mandate replacement or inspection of those very dodgy looking cam gears though. 250 hours could represent 10 years flying for some of these a/c.

[kevin_mayes]

Hmm, see I made it into print (Bell-47 G-BFYI) Fame at last, albeit in a very expensive way as the tail rotor blades had only flown 25 hours since new, and the replacement hub and strip down cost 10K, still one learns and lives to fight another day... And I now have two zero timed blades again!
Kev.

[widgeon]

That spitfire one sounds bad too , imagine spending 2 years building and then wiping out on first flight.

[parasite drag]

So 61 Lafite, do you have experience of what Rotorway owners "have to worry about" or was that just a jibe ?

[61 Lafite]

So 61 Lafite, do you have experience of what Rotorway owners "have to worry about" or was that just a jibe ?

I'm surprised that it took 10 hours for that backlash!

But what the hell, I'll bite as it's more fun than ignoring it.

Worrying is a normal reaction to a level of risk. As risks go up, normal people worry more.

Risk is not an imminent failure or an inherent fault or by any definition an absolute measure of unsafety. It's simply a quantifiable potential future outcome on a given set of circumstances. For the avoidance of doubt, I have no doubt that Rotorways are safe and fun to fly. However, they present a higher risk.

In a Rotorway (which I haven't flown) there is low rotor inertia, like an R22 (which I have flown). With a human in the loop and less time to react to an engine failure, the risk of a bad outcome is higher if the engine fails. We all train for it, and (as here) skill and experience together can give a good outcome. Unfortunately there have been incidents where the outcome was not good and investigation showed probable cause was due to pilots allowing RPM to go too low. This risk in a Rotorway is probably comparable to an R22, but higher than an R44, Jetranger etc.

In a Rotorway, there is a potential for the aircraft to be built by one or more individuals who have not built a Rotorway before and are not necessarily LAMEs. Most other helicopters are factory built with embedded quality control by trained staff who build lots of them. The risk of a build-error in a Rotorway is higher. They *may* all be built perfectly, but the risk remains higher that an individual one isn't.

In a Rotorway, the aircraft is built to a cost, as are all aircraft. However, at a low cost, the ability to over-engineer for safety is lower than the ability to do so in a more expensive aircraft. Rotorway undoubtedly put huge efforts into making the aircraft as safe as possible, but they do not have the budget to create solutions which are as over-engineered as in larger aircraft. Thus the risk of a failure must be higher. It's arguable that higher complexity in bigger aircraft means there's more risk there, but I don't subscribe to that view. In my view, even though I'm sure every component is completely adequate for its purpose, and most aircraft will reach TBO with no problems, the risk of a failure in a Rotorway is higher.

Finally, it's a numbers risk: there are less Rotorways in the air flying less hours than many other types. As shown in this failure, !!!! happens, but the more hours flown in that type by all pilots across all the type's aircraft before you step into it, the lower the risk of the !!!! happening to you because it probably happened to someone else first and been fixed. The failed drive cog is a very good example of this risk.

Any normal person considering themselves exposed to a higher risk situation (but not an *unsafe* aircraft) will worry more. Well, I would, anyway. Doesn't mean you don't fly, you just make sure you understand the risks and worry about mitigating them (good checks and training, probably).

Does that answer your question?

Lafite?

[swsw]

Not sure you're 100% correct on some of your assumptions here.

Yes, the Rotorway has a low inertia like the R22 but due to a different blade design your have much more time in the Rotorway to drop the lever in case of an engine failure, perhaps double or treble the dwell time.

In the UK at least, all Rotorways have extensive checks for the issue or re-issue of a permit to fly annually, plus all servicing has to be signed off by a CAA certified engineer...so quality is fairly uniform in the UK.

I agree with the greater service time of R22's etc issues are much more likely to be ironed out...and that makes the Robinson incredibly reliable...the Rotorway is certainly not at the same level. Plus the limitations of a Rotorway are tighter.

Pays your money and takes your choice I guess.

[Thomas coupling]

SWSW: tumbleweed........Look at the date of the last post sunshine...............