[shuttle]

Kitplanes Mag - Safety Is No Accident - Non-tradional Engines?

Have just read the July 2010 'Safety Is No Accident' article in Kitplanes Magazine
( http://www.kitplanes.com/issues/27_7/exploring/Safety_Is_No_Accident_Vans_RV_9272-1.phtml )

Without placing blame on the engines, the article states that 87% of RV's involved in accidents in the US over the 10 year analysis period had traditional (Lycoming/clone) engines and thus 13% had non-traditional engines (excluding the RV-12).

We have very few non-traditional engines in the UK RV fleet. It got me wondering whether that 13% non-traditional engine figure was representative across the entire US RV fleet?

The quoted 36% of RV-9A accidents involving a/c with non-traditional engines seemed very high to me.
Is that remotely representative of the US RV-9A fleet?

 

[RVadmirer]

Kitplanes Story

Does anyone understand the unusual graph in Figure 6? I don't think it's mentioned in the article and the huge jump at 100 hours seems to deserve discussion......
Good story and another great issue of the Mag. Now if I could just understand the series on vacuum bagging!

 

[flytoboat]

Does anyone understand the unusual graph in Figure 6? I don't think it's mentioned in the article and the huge jump at 100 hours seems to deserve discussion......
Good story and another great issue of the Mag. Now if I could just understand the series on vacuum bagging!

The chart is confusing. The chart shows the first 100 hours af an airplane's life in 10 hour increments. The next 900 hours are broken down into 100 hour increments. That throws the scale way off. If the left half of the chart was combined into one column (the first 100 hours), the yellow (RV) bar would have a value of about 28 and be consistant with the rest of the graph.
Hope this helps...

 

[Ironflight]

Don has it right - the first 100 hours are just "expanded' to show what happens there - a higher percentage in the first ten, then fairly even. And if you total it all up, the overall graph shows a decrease in accidents with airframe hours. Not sure why it dips at 400 and spikes at 500....but I'm well off the right side of the chart already, so I don't have to worry. Besides, I fly an -8 (primarily), so I am double safe...right?

Paul

 

[KPmarc]

It could have benefited from a more explanatory caption, that's for sure. Or maybe to be split up into two charts.

 

[RVadmirer]

Thank you guys!

Thanks Don, I saw the change in timeline and didn't take it into account. Don't look at stats much anymore.....

Paul, enjoyed your article too, looking for more.

Marc - great issue, as usual. Seems to be improving all the time.
Dave

 

[nucleus]

36 !@#$%&*! %!

Without placing blame on the engines, the article states that 87% of RV's involved in accidents in the US over the 10 year analysis period had traditional (Lycoming/clone) engines and thus 13% had non-traditional engines (excluding the RV-12).

Alternative engines installations are very rare in RVs, much rarer than 13%. This shows how more dangerous the alternative engines are.

The quoted 36% of RV-9A accidents involving a/c with non-traditional engines seemed very high to me.
Is that remotely representative of the US RV-9A fleet?

I believe that could be true, there seems to more 9's with Subies installed than other models. Non-traditional engines are way more likely to have a off airport landing. Since the 9A is such a docile baby to fly generally, it makes sense that the "unsafe effect" alternative engines would magnified. In other words, since RV-9A's are so safe, the increased risk of power loss appears magnified compared to the other RV models.

I think the moral is this: Don't be fooled by pretty anodizing and lots of happy customer anecdotes on their website. Dangerous stuff. In my opinion, if you are going to do it, you would probably be better off developing your own install.

 

[DCat22]

Without placing blame on the engines, the article states that 87% of RV's involved in accidents in the US over the 10 year analysis period had traditional (Lycoming/clone) engines and thus 13% had non-traditional engines (excluding the RV-12).

Anyone happen to know the rough % of Lycoming vs. Alternative for all RV's flying?

 

[rv6ejguy]

Good Stats are Hard to Find and Harder to Quantify

I'm pretty close to many of the auto engined forums and know a good portion of the alt powered RV guys flying. These consist mainly of Subaru, Chevy V6 and Wankels. My best estimate is that less than 3% of RVs are alt powered. The accident rate does not look so good in this light however we don't know if those 13% of accidents were caused by the engine, supporting systems or dumb pilot tricks. The stats only say that 13% of the accidents involved alt engined RVs- probably a strong enough case logically to conclude that far more accidents happen in these than Lyco powered ones simply because they don't have a Lyco up front.

Interestingly, something similar was discussed a couple years back here on VAF comparing Lyco/ Conti and Subaru core reliability. Although people sifted the NTSB data differently, surprisingly the CORE reliability of Subaru engines was better than the Lycoming/ Continental however the total FF system reliability was FAR worse. In other words, the engine was good but problems with the supporting systems such as fuel, electrical and gearbox usually caused the power loss. No matter, you still ended up coming down in an unplanned way.

Making some perhaps not so accurate assumptions about annual flight time and unreported power loss and safe landings and depending on what was "counted" as an actual "failure" (I threw out bad maintenance and fuel exhaustion in both cases), it looked like alt engined aircraft were between 4 and 8 times more likely to be involved in a power loss accident or forced landing event than their Lyconental counterparts (all airframe types).

Makes a pretty strong case not to install an alt engine doesn't it?

The use of often non-standard and relatively unproven fuel system layouts and components was a rather common thread, ditto for ignition/ electrical systems and issues with gearboxes which were never properly designed or validated. These were the 3 most common problem areas leading to power loss. Inadequate engine cooling was also common but rarely caused actual power loss- just plenty of frustration.

In the last 2 years especially, groups like Subenews and Flysoob have helped spread the word about what does and does not work and the importance of proper system design. Subenews in particular has helped owners solve common problems more quickly and show owners where to look for potential gotchas. It is an important resource. Standardized systems are proven to be less risky. Properly engineered gearboxes are now available and these have excellent reliability with many thousands of flight hours behind them worldwide. We are still finding new warts and worries on some installations but slowly learning through sharing info on how to solve them.

Of note outside the RV world, some kit manufacturers now such as Titan Aircraft and others mainly specify and recommend automotive V type engines from Suzuki, Honda and GM for their fighter replicas. These have proven to have decent reliability when fitted the latest gearboxes, standardized fuel and ignition/ electrical, cooling systems and component layout. When owners deviate from the recommended layout, their reliability is usually far worse. A very small, seemingly insignificant change can cause an engine out as was the case not long ago for a Titan T51 V6 which had to belly into a tomato field. Talented pilots/ tech people like Bill at Titan have helped pave the way for safer installations for their customers through lots of flight time and a number of component failures.

For now, in RVs, the Lycoming remains the best choice for most people IMO.

 

[SteinAir]

Good post Ross. Data for these types of things is very difficult to pin down as far as "staticstics" go. Sometimes (many times in fact) nobody really knows the exact root cause of some accidents, so we forever are guessing. If you know statistics at all, then you know they can be manipulated (even with facts) to show different thigns. For example, one could currently and accurately state that 100% of flying RV-10's with alternative engines on them have had a 'crash' or 'significant incident'. But, that really doesn't tell the entire story as we all know. Add to that the incidents that go un-reported with both standard and alternative planes and it really makes it difficult to make number absolute.

Anyway, I'm obviously not adding anything significant other than to say numbers are what they are and reality is what it is. Hopefully this doesn't digress into yet another alternative engine thread - I don't think we need any more of those!

Cheers,
Stein

 

[rv6ejguy]

Good post Ross. Data for these types of things is very difficult to pin down as far as "staticstics" go. Sometimes (many times in fact) nobody really knows the exact root cause of some accidents, so we forever are guessing. If you know statistics at all, then you know they can be manipulated (even with facts) to show different thigns. For example, one could currently and accurately state that 100% of flying RV-10's with alternative engines on them have had a 'crash' or 'significant incident'. But, that really doesn't tell the entire story as we all know. Add to that the incidents that go un-reported with both standard and alternative planes and it really makes it difficult to make number absolute.

Anyway, I'm obviously not adding anything significant other than to say numbers are what they are and reality is what it is. Hopefully this doesn't digress into yet another alternative engine thread - I don't think we need any more of those!

Cheers,
Stein

Yes Stein, there is a rather famous book, "How to Lie with Statistics" that has been around a long time. Data from stats can be manipulated to suit most any hypothesis or cause. If we try to look strictly at the data and don't have any preconceived ideas, it is clear that alt engines present higher risk. You simply cannot come to any other conclusion.

If we are to turn this fact around, we must learn and apply lessons brought out in the investigations of failures and share these with other users.

With regards to your observation on alt engined RV-10s, it is a true fact. A bunch more Sube and GM powered -10s will fly in the next year or two and unfortunately, I expect some of these to have issues. Let's hope they are not serious like the others before.

My recommendation for people contemplating alt engines is generally not to do it unless they have a good technical background in mechanics/ design and/or get their kicks from this type of stuff. They must also be willing to accept the proven higher risk. I do see quite a lot of complacency in many traditional engined pilots on the other side of the coin. They often think nothing will ever happen with a Lycoming up front. If you delve into the NTSB data base, clearly this is far from true. Keeping your engine out skills sharp is a great idea no matter what engine you fly with as is good decision making before the flight even begins.