NTSB report into home builds [Archive]

A and C

25th May 2012, 07:21

The biggest problem with home builds is the variable quality of the work, most aircraft that I am called to inspect are very well built and maintained to a high standard, however there are a few that are not.

This brings to mind the import from the USA were the strobe lighting harness had been routed through the fuel tank in a flexible hose that was leaking.

It is no wonder that the FAA are looking to improve standards, the LAA are working on this as well, I happen to think that the LAA has just about got the balance correct my only slight issue is that they don't maintain a common modification data base that allows owners to use already approved modifications without going through the whole modification process.

maxred

25th May 2012, 07:33

I found the survey results interesting and probably confirming the perception, which was not really based on any qualitative input.

I am off to Oshkosh shortly, the home of the experimental type, and each year I witness guys doing and making things that as Silvaire highlighted is the bedrock of possibly where we are now.

Some of the recommends are worry some, particularly the points of engine performance and fuel systems, because the very nature of EXPERIMENTAL, is precisely that.

The land of the free, may just be becoming a little less so.

Genghis the Engineer

25th May 2012, 07:34

From EAA yesterday:

"Both EAA and the NTSB know that we must improve the accident record of amateur-built aircraft," said EAA President Rod Hightower on Tuesday evening, in a video response to the safety board's report released earlier that day. However, he said, some of the NTSB's recommendations to the FAA, which could result in more regulations, are "worrisome." For example, the NTSB wants new regulations for testing engine performance and for documenting flight tests in amateur-built aircraft. "At EAA, we do not believe that more regulation is the answer ... Education, versus new regulation, is a better solution," Hightower said.

The four recommendations the NTSB aimed at EAA would expand on programs that are already in place, Hightower said. EAA's Homebuilt Aircraft Council will continue to study the recommendations for what effect they may have on the design, building and certification of amateur-built aircraft. "Any action must ensure that the freedom to participate in the amateur-built aircraft community does not create additional burdens or hurdles," EAA said in its news release.

I agree that Peter would lose his bet - the UK and US are chalk and cheese where homebuilts are concerns.

In the UK we have a (relatively) light touch system for approval (not certification) of kit and plans built aircraft, with a choice of BMAA, LAA or CAA for approval depending upon what it is.

The accident rate in Britain for amateur built aeroplanes used to be higher than for certified aeroplanes, but the margin was much smaller than the US, kept closing and has bcome statistically insignificant between all of the various fixed wing classes of light and microlight aeroplanes in the UK over the last decade or so.

Hence we now can fly PtF aeroplanes over built up areas, and the next and obvious stage will be to revisit the long abandoned aspiration for IMC and night in UK registered PtF aeroplanes in UK airspace.

The fact is, the US is finally realising that the British were right, although somehow I doubt that they'll ever express it in those terms.

The reason for more and more interesting experimentation in the USA, in my opinion, has nothing to do with their degregulated category - it down to a fair better culture of experimentation, and in practical engineering, a better educated population compared to a British culture which educates engineers, but is obsessed with (a) being an employee subject to other people's bright ideas, and (b) not taking risks of failure.

The good designers in the US, the people producing the really interesting experimental designs, would still thrive in the British environment.

In my opinion :}

G

this is my username

25th May 2012, 08:24

Can't really agree with you on that one, Genghis. You only have to look at the microlight / gyroplane manufacturers in Europe vs the UK to see the impact of regulation on innovation.

In (most of) Europe if a manufacturer wants to build a new aircraft in the microlight category they build it and fly it. They can then experiment and change the design as they see fit to get the characteristics they want. Once that is done they go through the paperwork process (if any) to get the aircraft approved. As a result development cycles are (relatively) rapid and (relatively) low cost.

In the UK you need a design approval and a production approval (£££ and time). The design has to be approved (£££ and time) and hoops jumped through before it can be flown. Once you have flown it any changes have to be redesigned and re-approved (you can't just wheel it back in to the hangar, tinker, then wheel it back out again and see if that worked).

The result? The cost and timescales for innovating in the UK are so high relative to (most of) the rest of Europe and the US that few bother - they just find something else to do (or move).

The upside is that, as you described, the accident rates on UK permit aircraft are a good deal lower than on the US Experimental fleet.

Genghis the Engineer

25th May 2012, 09:07

In the UK you need a design approval and a production approval (£££ and time). The design has to be approved (£££ and time) and hoops jumped through before it can be flown. Once you have flown it any changes have to be redesigned and re-approved (you can't just wheel it back in to the hangar, tinker, then wheel it back out again and see if that worked).

I know the system, I'm a CAA design signatory,a BMAA Senior Inspector, and a BMAA and LAA Test Pilot. The people who use these excuses not to innovate are generally those without the skills to generate good products anyhow.

The costs to be paid through BMAA or LAA are pretty trivial, no DOA/POA is required, and ultimately it comes down to the time and effort required of the designer to get it right.

At the certified end it is usually different in that the sheer costs of getting kit certified in Europe are far higher than in the USA with its very elegant DER system, but this thread was about homebuilts. But even then, I recently looked to two changes to my vintage / UK-reg / CofA aeroplane.

(1) Fitting an uncertified oil cooler; this took my effort, purchase of the parts, and once I'd sumbitted a report to CAA, a charge of £61.
(2) Switching from AVGAS to 91UL; this I managed to do on a paperwork exercise and has cost nothing.

Ultimately what I needed here was to be competent, not any deregulation.

Designing an aeroplane is much harder, and requires different skills, to flying one. But, many people do not recognise that, and whilst they accept that they need formal training and assessment to fly, somehow don't believe that this should apply to designing and building.

G

cockney steve

25th May 2012, 09:35

Ah, yes, G....but how much would an ordinary punter without your skillset, pay for the benefit of your expertise.

I'd guess that you aren't a one-man charity ,nor are you on national minimum wage. ;)

this is my username

25th May 2012, 09:55

Good job you found yourself a job as an engineer Genghis and not as a diplomat!

On behalf of those of us who work in sport aviation in the UK rather than playing at it I'm glad to hear that you think we are just too dumb and lazy to innovate rather than being held back by the dead hand of regulation!

Genghis the Engineer

25th May 2012, 10:01

No I don't usually do engineering for free, and I don't teach flying for nothing either (unless it's within one of my syndicates, when I do both for nothing). Equally I'm not a diplomat - after all, what's the benefit in telling people with no formal training that they'll be fine designing an aeroplane without getting any formal training or oversight. You'd call me utterly irresponsible for saying you should teach yourself to fly. And what's the difference between paying an engineer (who put years and a lot of money into his education and training) to help with an aircraft design, and paying an instructor (who did the same) to teach you how to fly it?

But LAA and BMAA do have lists of members who'll help other members with their projects. And many of us (I have helped with both) will do that sort of thing for a lot less than the day job and sometimes for free, particularly if there's a chance to get some flying in an interesting aeroplane out of it.

Both also run occasional courses on how to do certification engineering. And then there are things like OU modules available for people who need skills like stress analysis or aerodynamics: or even a full engineering degree. The educational routes are there for those who choose to take them.

G

N.B. I worked full time in sport aviation in the UK for nearly 9 years. I just happen to do something different as my main day job now - but that does include GA teaching and safety research. I have put my money where my mouth is regularly for a lot of years. But no, I've never been a diplomat.

Pilot DAR

25th May 2012, 11:18

but how much would an ordinary punter without your skillset, pay for the benefit of your expertise

My guess would be a heck of a lot less than the cost to them to gain that skill set, that fast, with their own self study, when the job needs to stay on schedule! Probably money per hour, the punter would think nothing of paying their dentist even more than the aircraft expert!

maxred

25th May 2012, 12:04

The root of course in all of this is that from experimentation, leads innovation. Without the guy at the outset, that pushed the edge, then we possibly would not be where we are now. Of course this must be acquired within a framework of safety/risk, however, here is the dilemma. It was that the USA led the way in this, and the EUropeans regulated, to the extent that full on regulation, by it's nature, stifles risk, and risk taking, the penalty is punishment. Over regulation.

The EAA has recognised this, and encourages education, with controlled regulation. This must be the way. The fear is that this may be the thin edge of the wedge as far as the US is concerned, and that would be a shame. I also think the statistics may be flawed, accident rate US/the rest. The culture encouraged the innovator, and from this would obviously come a greater number of incidents.

Pilot DAR

25th May 2012, 14:45

My opinion, and having not read the referenced NTSB report is that amateur built aircraft possibly have a greater accident rate because of a combination of factors. With many exceptions, amateur built aircraft are the labour of love for a low time/new pilot, and that person's life goes into the aircraft building for extended periods, to the exclusion of piloting skill development/maintenance. Then the low time pilot gets in the newly built aircraft, and starts to work out the bugs. That is a higher risk [than the recently experienced pilot flying the club C-172/PA- 28] no matter how you look at it.

Yes, we must encourage the experimenters and enthusiasts, and allow them freedom to do their thing. We can only hope that they avail themselves of the wealth of knowledge and experience out there. For the most part, it's been done before, someone has already learned how.

peterh337

25th May 2012, 17:43

There is some amazing stuff going on under the US Experimental regime, which I can't see being allowed here in Europe.

Take for example the Epic Dynasty - a pressurised turboprop with amazing performance.

Or the Lancair pressurised turboprop.

Many people have looked at whether they can bring such stuff over here but they usually find it impossible.

peterh337

25th May 2012, 19:47

patowalker

25th May 2012, 20:06

I have read an awful lot of AAIB reports over the years where some "homebuilt" had broken up in flight.

Talk about rapid depreciation: in one sentence "an awful lot" drops to "some". :)

Genghis the Engineer

25th May 2012, 21:05

Am I the only one who looked at it and thought that it was right for there to be a higher accident rate with home-build "Experimental" compared with certified?
Yes it is, but not a factor of 4 surely?

However, it's undeniable that we do not have a Vans or a Sonex in the UK. Nor do we have an Evektor or an Ikarus.
A quick check on G-INFO shows 398 Vans, 5 Sonex, 3 Evektors and 146 Ikarus.

Or if you mean that we don’t have equivalent British companies, you presumably don’t count any of the following British designs as revelant?:

SLA 100 (http://www.ravenmad.co.uk/slaexecutive.htm) – which is roughly equivalent to the Ikarus products.

Europa (http://www.europa-aircraft.com/).

Reality Escapade (http://www.realityaircraft.com/), or it’s smaller sister the single seat Escapade Kid (http://www.reality-aircraft.co.uk/technical-stuff).

Aviation Enterprises Magnum (http://www.aviationenterprises.co.uk/Magnum%20Data%20Sheet.doc), which is substantially tested and certified and has been looking for production backing for years, but that's a problem with business backing, not aeronautics.

CTSW (http://www.pmaviation.co.uk/ctsw.html) (admittedly developed from a German design, but developed, tested and certified in the UK, by an all-British team).

Thruster T600 (http://www.thruster.co.uk/spec/)

All the Mike Whittaker designs (http://www.mwclub.org/), numerous of which are still being built and supported.

And if we get onto Flexwings of-course, there are huge numbers of high tech British aircraft in production including the QuikR (http://www.pmaviation.co.uk/quikr.html), GT450 (http://www.pmaviation.co.uk/gt450.html), PulsR (http://www.gsaviation.co.uk/images/pulsr2.jpg) (which admittedly isn’t certified yet, but personally I’m drooling over since I saw the prototype fly into Cranfield a couple of months ago), AV8R (http://www.ravenmad.co.uk/av8r.htm), EclipseR (http://www.ravenmad.co.uk/eclipse912r.htm), Dragonfly (http://www.flylight.co.uk/flexwing/dragonfly.htm)

So, apart from all of those British, in-production, innovative, light and microlight aeroplanes (okay, the Magnum’s not in production, and the CT started out foreign), you’re probably right – nobody in the UK manages to innovate in light aircraft design.

Well apart from the Lynden Mk.2, Europa MotorGlider, Mole Mite, Skylark, Trail and Wright flyer replica shown on LAA’s website as ongoing, and a handful of things doubtless going through the BMAA (although they don’t publish a list).

Or at the Gyroplane end, nobody except for Rotorsport (http://www.rotorsport.org/) and Merlin (http://www.gyrocopters.co.uk/).

No, you’re probably right, no real development of British light aeroplanes, and no real innovators here, plus impossible to certify new types here. Or you don’t know what you’re talking about – one or the other.

G

Genghis the Engineer

25th May 2012, 21:15

I have been criticised for saying this but I have read an awful lot of AAIB reports over the years where some "homebuilt" had broken up in flight.

On certified types, one heard of that only in very rare cases e.g. flight into a TS, loss of control resulting in Vne+ etc, or odd ones like that Robin which hit a bale and the wing came off on a later flight.

Could you give references for those in-flight breakups, because I can only think of two in about 15 years - G-STYX in 2005 (which actually was a factory built microlight, albeit one that suffered a breakup due to poor maintenance practices) and G-BVNA in 1999, and if there are a lot more, I'm very embarrassed not to know about them.

G

maxred

25th May 2012, 22:00

Silvaire I am going to have to investigate that number. Seems very high to me. Will revert.

abgd

26th May 2012, 03:34

Is it fair to equate homebuilts with ptf? Many permit aircraft started out life as well respected CofA types whereas many homebuilts don't have the design pedigree that these aircraft have.

I have always thought that American innovation was driven by the lack of 16th century farmhouses that need to be renovated. And having Edison as a national hero... I can't think of a British inventor who is venerated in quite the same way.

flyingfemme

26th May 2012, 08:10

Experimental in the US means so much more than "amateur built" and covers plenty of stuff that would not/cannot happen in the UK. Home builds are just one facet of the experimental scene.....maybe they are slightly less safe than certified aircraft but innovation requires risk. The people that build them know that and accept the risk.

Test flying new aircraft in the US is done on the experimental........I have seen Cessna's jet developments being flown around Wichita with the magic word on the side. No way are those "amateur built".

The Farnborough F1 was developed as an experimental because the team could not do what was needed (fly the thing) with the CAA. Some of that "experimental" flying happened outside the USA.......

Warbirds are generally experimental as well....and there are tighter certifications than that for display aircraft. Americans can, and do, fly stuff that is banned for civilians here. Jealous? You bet!

What is the collateral damage on experimental crashes? If only pilots and engineers are involved then they should be allowed to make the choice.

maxred

26th May 2012, 09:31

Thanks Silvaire. I stand corrected on the number. I did not realise there had been so many incidents in the early years of that type. As the article observed operating the type outwith the design envelope, coupled with irrecoverable pilot induced control input was the probable cause of the majority of these accidents. I do not think it is entirely like for like on the experimental/amateur home built market, but point taken.

Genghis the Engineer

26th May 2012, 09:33

Experimental in the US means so much more than "amateur built" and covers plenty of stuff that would not/cannot happen in the UK.

I can't think of anything that can't happen in the UK, it just might be more difficult or epensive.

Home builds are just one facet of the experimental scene.....maybe they are slightly less safe than certified aircraft but innovation requires risk. The people that build them know that and accept the risk.

"Slightly" = 4 times?

Test flying new aircraft in the US is done on the experimental........I have seen Cessna's jet developments being flown around Wichita with the magic word on the side. No way are those "amateur built".

And test flying in the UK is done under B-conditions, (or exceptionally under LAA's slightly odd and archaic "exemption from A-conditions"). Many of those aren't amateur built either.

The Farnborough F1 was developed as an experimental because the team could not do what was needed (fly the thing) with the CAA. Some of that "experimental" flying happened outside the USA.......

No, the F1 was developed to be a certified aeroplane, and many of the team were used to working under B-conditions. It was tested in the US as an experimental because the project got bought out by an American company. Quite a lot of British Engineers lost their jobs because of that.

Warbirds are generally experimental as well....
Or in the UK, "Ex-military Permit to Fly"

and there are tighter certifications than that for display aircraft.

As there are in the UK, several CAPs exist to cover this.

Americans can, and do, fly stuff that is banned for civilians here.

Yes, private warbird ownership is much easier in the USA, and the DER and research-experimental system are much cheaper than the UK system for CofA aeroplanes, but there's very little you can't do in both countries.

Jealous? You bet!

I go to a US test flying conference about once per year, and they are incredibly competent and professional, plus often have better resources than we do.

But actually, the good people do just the same we would in Britain. The things I'm most jealous of in the USA are cheap fuel and 24 hour airports.

What is the collateral damage on experimental crashes? If only pilots and engineers are involved then they should be allowed to make the choice.

That of course is the issue. There is to some extent a difference in mentality between a huge largely empty country, and a relatively small and crowded island.

G

englishal

26th May 2012, 13:31

Test flying new aircraft in the US is done on the experimental........I have seen Cessna's jet developments being flown around Wichita with the magic word on the side. No way are those "amateur built"
Indeed, the B787 that flew from London to Hong Kong the wrong war around was EXPERIMENTAL.

Rod1

26th May 2012, 18:25

When the LAA petitioned to get the over flight restriction removed it produced a report of all the accidents involving LAA permit aircraft and UK CofA aircraft over 30 odd years. The report showed that the chances of your permit machine killing you was 2.5% less than the chances of the C of A machine killing you. The CAA redid the work and came to the same conclusion. You could argue that 2.5% is statistically insignificant, but the over flight restriction was lifted on the bases that there was no difference in the risk LAA permit / CofA.
The report was on the LAA web site for some time. If you want a copy I am sure the LAA would provide it. In my personal opinion, both systems work well most of the time but a man in a rush under commercial pressure can make a mistake and so can a misinformed novice.

Rod1

patowalker

26th May 2012, 21:10

It will be interesting to see how long the LAA takes to approve the kit-build for a design that already has an EASA Permit to Fly. Apart from the build documentation, what else could be required that was not already available?

Genghis the Engineer

26th May 2012, 22:03

Pboyall, I don't dispute your figures, but surely you're making a different point. (And aside from that, being rather churlish about the substantial talent that went into aeroplanes like the CTSW and the Escapade, which are very very far from any overseas design,after all everything was probably inspired by something - the Cub inspired the Kitfox, inspired the Avid, inspired the Skyraider, led to the SkyRaider II, led to the Easy Raider, led to the Escapade, led to the Escapade Kid.....) Where do you start?

I showed that clever enough people are managing to get new-design aeroplanes flying in the UK, and that there are enough sales to create viable businesses.

You've showed that certain companies, in certain other countries, are producing far more marketable products. These are series aircraft, all largely the same, and clearly most are damned good ones.

So, why is Britain not producing saleable aeroplanes any more? Why are the aircraft coming from the UK underwhelming even our home buying public so much, let alone anywhere else?

This is a serious problem, and I don't have an answer to offer. To me, this is much more the problem than that in the UK we can only freely experiment under 115kg.

Incidentally, I've certified both flexwing and 3-axis microlight aeroplanes, and whilst the technology is different, in my opinion there really is little or no difference between the legal issues. They are basically treated the same. In "group A", there is a significant difference between kits and manufactured aeroplanes legally.

G

Genghis the Engineer

27th May 2012, 16:01

I thought you had something there, so ran a few quick sums.

Kitfox 7 firewall-back kit: US$20k + taxes, so would be around £15k with UK VAT
Reality Escapade firewall back kit: GB£20k inc.VAT

So there is a difference in pricing.

However, I'm not convinced it's amortization of certification costs. The real costs there are of building a prototype or prototypes and testing them; the costs of reporting that to a competent authority, but a competent company, is generally below £10k in the UK.

Britain can't build stuff cheaply, it's why we buy everything from rubber ducks to laptops from the middle East. Where we do things profitably it's ultra-high value added such as jet fighters or Lotus cars, or where extreme cleverness gets the production costs right down - I believe that P&M assembles a new flexwing in under 60 man-hours.

Which may be the problem. The Europa must have been very high man-hours to produce, and as a fairly knowledgeable observer it always seemed to me that this is what killed CFM: the man hours to build a Shadow were silly.

For years Britten-Norman built Islanders in Bucharest, P&M now build the CT in the Ukraine just doing the very high value-added stuff in Britain (design and test basically).

My gut feeling is that whilst the high certification standards in Britain keep the idiots out of the game, the two problems we have are a lack of educational opportunities to become good little aeroplane designers, and very high production costs.

ICP, who build the MXP740 Savannah in Italy do so on the side of a computerised sheet metal fabrication facility that is mainly a sub-contractor for people like Boeing and Airbus. I wonder if we need that approach here - good production engineers creating opportunities on the side of existing high volume / automated production facilities that must exist in the UK somewhere.

G

patowalker

27th May 2012, 19:23

ICP, who build the MXP740 Savannah in Italy do so on the side of a computerised sheet metal fabrication facility that is mainly a sub-contractor for people like Boeing and Airbus.

Not a good example, as Aeroandina holds ICP responsible for The enormous economic damage that derived from the plagiarism of our MXP-740 Savannah airplane by the previous Dealer, ...

Aeroandina :: Technology in Constant Evolution :: History (http://www.aeroandina.com/eng/historia.htm)

The MXP-740 looks a lot like the Zenair CH701, but the relationship between Aeroandina and Chris Heintz must be a good one, because their Patriot LSA was going to be distributed by AMD and Can Zac Aviation, part of the Heintz group. This did not materialse and the aircraft was renamed Tayrona.

This might seem irrelevant, but the discussion was about design and manufacture.

Genghis the Engineer

27th May 2012, 19:59

The MXP740 was a blatant rip-off of the CH701, and anybody subsequently complaining about their rip-off being ripped off, is perhaps being a little disingenuous.

On the other hand, the UK version of the aeroplane, which I was privileged to do a chunk of the test flying of, did finally fix a lot of longitudinal stability problems that were in both the Chris Heintz original, and the Italian Rip-Off version (which also had serious stalling issues that we fixed after a great deal of fix-fly-fix effort).

Yes, the thread started about design, and my point there was essentially about manufacture.

Incidentally that website you posted also said:-

“ CANARD” SINGLE PLACE:- In 1980 AGROCOPTEROS entered the field of “composites” by building the “Gold-Wing”, fibreglass canard single place light airplane for tourism, very safe and with very low operating costs. 12 units were produced.

Who builds a single seater for tourism? (Also the Goldwing that I once owned half of, scared the bejeezus out of me at-least once per flight !) And I wonder, since they don't say, if their R&D (Rip-Off and Duplicate) was off the American original Goldwing, or the Scottish licence-built heavier and bigger engined version?

G

patowalker

27th May 2012, 20:38

Why was CH quite recently dealing with a manufacturer who ripped him off years ago?

Patriot (http://www.can-zacaviation.com/patriot.htm)

Aeroandina only claims to have built the Goldwing. If they were ripping off the original design, they would have called it something else, I think.

If you had lived as long as I have in Colombia you would understand what they mean by 'tourism'. A better description would have been 'leisure' or 'sport'.

gasax

28th May 2012, 07:37

CH is dealing with companies which have production capability. None of these designs is incredibly profitable - all need to have economies built into them somehow or other.

I was surprised to read about the CH / ICP tie up as CH has in the past been very critical of ICP's 'rip-off of the 701.

But - and it's a very big but - since Chip Erwin and the Czech sport debacle CH have lost their European manufacturing base. That was a fairly big market for them and the cost of importing the kits from the US made them surprising(?) expensive - largely due to the Euro/dollar rate.

So CH needed someone in Europe with decent CAD/CAM facilities - welcome back ICP. Having visited the Czech factory before the Czech sport issues I could see that there were still quite a number of economies which could be made during the build process - and Chip had people working on that. And this is with aircraft designs which are quite simple and easy to homebuild.

Perhaps that is part of the problem - I remember as a student visiting Scottish Aviation where a chap proudly told us there were 100 odd pasrts to the door he was building - and we left baffled as to why (and how and how expensive that must be...). The UK aircraft industry still has that skilled artisan who can do it all and the remanant of the 'cost plus' MOD approach of simply putting too many and too complex components into things. Look at a CH design - there is nothing you can take out and it could all be built with simple tools. But to build it at competitive costs it does need to be production engineered.

The best comparison I can think of is my old Auster had a handwheel, springs and levers to move the seat - my mates Pa22 a couple of bent 4130 strips with a pin. So his cost a 1/10 on mine and had similar weight savings...

Clever design is all very well - but to be commercially successful it has to have production capability. Genghis hit the nail on the head with the Shadow - terrific design - but building it.....?

patowalker

28th May 2012, 09:51

I was surprised to read about the CH / ICP tie up as CH has in the past been very critical of ICP's 'rip-off of the 701.

You misread my post. The tie-up is/was between Aeroandina in Colombia and CH.

I visited Chip's Stare-Mesto factory when the temperature was minus 14C, and it was even colder at the little airfield where they tested rtf aircraft. Incidentally, I met Milan Bristela, his chief engineer at AeroExpo on Saturday. The SportCruiser and Bristell owe a lot to CH.

barit1

10th Jun 2012, 18:47

Speaking of mods -

I recall over 40 years ago seeing a report of a low-wing homebuilt (strut-braced a la Stits Playboy) in which the builder/pilot decided he needed more wing area, so he built a new pair a couple feet longer. This of course moved the spanwise center of lift outboard and increased the compression load on the strut; on a subsequent flight it folded.

Now just yesterday it appears a similar event occurred near Dayton OH (I say appears because one commenter said the builder had installed new wings of greater span). In this case it appeared to be a cantilever wing design, but the effect of extending the wing is the same.

There seems to be little appreciation among some builders of the implications of a "custom" mod to an otherwise successful design.

Genghis the Engineer

10th Jun 2012, 19:59