Anyone at Oshkosh this year? We’re on the WACO stand…!
Peter wrote:
Most people who buy a UL, a kit or a homebuilt built by someone else have no more clue about the design margins than those who buy a certified type. Nobody expects to buy a death trap.
non-certified means non-certified, there is no way to escape that. Lots of people fool themselves by thinking that “my” aircraft is so fast/advanced/cool and so on, the designer certainly is a genius etc etc and therefore it must be as safe, or safer, than the traditional off the shelves spam can. Certification means exactly what mh say (among other things). The design, the materials, the build methods, the subcontractors, the factory – just about everything – has been gone through by several independent engineers and checked against standards and best practice. There are, in theory at least, no un-turned stones in a certified aircraft. Therefore, in theory, a certified aircraft must be safer than a non-certified aircraft.
In practice though, this is not what the statistics show. Un-certified aircraft have no more accidents due to structural failures than certified aircraft. You can single out examples from both “worlds”, examples that are so few they are statistically insignificant. Why is that? The reason is of course that certification of light GA airplanes is like shooting sparrows with a cannon, when a simple pea shooter would do just fine. Certification is not the only way to weed out design mistakes. That pea shooter can be builders that build experimental aircraft from kit or plans. They discuss every single detail. As the saying goes; you can build a plane in 2 years, but if you are an engineer, multiply it by 3 An experimental aircraft is essentially 100% open for anybody to scrutinize all they want, and anybody does, and do small improvements here and there, needed or not. The potential fatal design errors are simple extremely unlikely to happen, because they surface ASAP, often in very unpleasant “debates” on the internet. The wing spar on the RVs and the Cx-4 and -5. Anodized wing spars (or RVs). The crank shaft of the Aerovee engine, The usage of SS fasteners on the Sonex airplanes. Usage of 6061 instead of 2025 on several aircraft, and billions of smaller details.
With factory built microlight things are different. The design is not “open”, and trust has to be put on the manufacturer, blind faith if you want. But engineers are engineers. They have an urge to make thing as good as possible and discuss things openly among themselves, also across companies (which often terrorize the more “commercially” adapted persons opting for secrecy). Anyway, with MTOW of 450 kg, BRS (enforced by the government or voluntarily), some minimal scrutiny of the design by some “authority”, there really are not much left that can kill.
Another aspect is that a person has a life. He is entitled to manage the risk any way he chooses. That is a major aspect of living a life. Making an aircraft for commercial transport is something entirely different than making an aircraft for personal recreation. IMO the attack from the French authority on “cost shared flight”, is not so out of line as many here seems to think.
And this is why you need proper independent certification that finds severe mistakes
Yes, but only on certified aircraft
You are kidding, surely? Most people who buy a UL, a kit or a homebuilt built by someone else have no more clue about the design margins than those who buy a certified type. Nobody expects to buy a death trap.
mh wrote:
And this is why you need proper independent certification that finds severe mistakes
Yes, but only on certified aircraft. Besides, for å light aircraft an industri standard should be møre than enough along with testing.
LeSving wrote:
I believe this to be the one where the seat fell out? (and the pilot with it). This was a prototype as far as I can remember, done under high G testing.
No, it was neither. It came apart during a level off in around 1000 ft out of a shallow dive from 1700 ft at around 200 to 240 km/h IAS. The owner had requested to use emergency parachutes instead of the BRS, but that was denied by the “authorities”. So the BRS could only save one of the persons on board. The BFU found out, that the wings had undergone static load tests, but the load carrying structure within the fuselage had not been tested. They FEMed the structure as a box beam, but installed a C-shaped beam as primary load-carrying structure. There were no calculations in the built configuration. There were no calculations with a correlation of stick forces. That teh BRS worked was just a coincident, there wasn’t much left and the BRS would have only worked for the engine. The ASI markings did not fit the requirements of the certification standards, the yellow arc began at 250 km/h instead of the correct 160 km/h. The low figure was a result of the minimum requirements for the load carrying ability of the structure. Furthermore, the requirements which the “certification” of the Dynamic was based on is much lower than the corresponding CS23/FAR23 and CS22. Especially the conditioning of FRP-structures differ or is not prescribed in the microlight requirements. It wasn’t absolutely certain that this accident was based on the slack certification work, mainly because there were only hints to the actual loads at the time of structural failure, but it was without doubt contributing.
And this is why you need proper independent certification that finds severe mistakes. Even the most capable engineers do make mistakes and some of them can be lethal in an airplane – they have in the past and they will continue to do so. In the wake of this and two similar accidents, the requirements for microlights in Germany have been altered.
Here is the report (in German)
The EAA is homebuilt, warbirds, vintage, aerobatics, LSA, ultralight and from 2015 also the “IMC Club” created to promote instrument flying, training, proficiency and safety. The only thing lacking is “contemporary” certified GA although that was not exactly lacking on the “sales” stands. What exactly is vintage anyway? 30 years, 50, 70 ?? IMO vintage is a restaurd and usable older aircraft that is not (factory) produced anymore, but I don’t really know what the “correct” definition is.
A friend sent me this collection of photos from Oshkosh 2016 this morning. I think they capture the breadth of the event over all kinds of aviation pretty nicely.
I was intrigued by the Staggerwing with the the VT (Indian) registration, until I noticed the little N-number under the tail. Must be something in the plane’s past. The photo of three Howard DGAs in a row also got my attention, as this would probably be the ultimate going places plane for me, if I wanted to pay the fuel bill for 450 HP. I wouldn’t mind the Swearingen SX300 either, and it’s a lot more efficient.
Who mounted the DA-42 on a steel post??
A bit more professionally edited summary of AirVenture 2016
mh wrote:
I don’t know why some pilots assume mass limits were just for paper. If the designer wants to have a higher MTOM, he should just certify it.
There are Australian regulations, US regulations, Canadian regulations, EASA regulations (microlight, LSA, VLA …), South African regulations, Brasil, Argentina. Particularly for an “LSA type” of aircraft all these regulations are different, yet rather similar. The 230 or 430 or whatever the previews names are, is certified according to the Australian regulations. Then it was certified as US LSA. The US LSA only has MTOW, max level speed (at sea level) and max stall speed. It also must have fixed pitch prop. From the Australian certifications, the only thing that needs to be done is to use a prop that restricts max level speed, and decrease the MTOW so the stall speed is OK and/or the max allowed weight is reached. It would make no sense for a manufacture to make structural changes it doesn’t have to make.
In theory you are of course correct (in an extremely nitpicking “by the book” kind of sense) . However, the point is, the 230 was not designed according to US LSA regulations, it just happens to fit right in there.
Rwy20 wrote:
I’ve never thought of a turbine when I hear a Rotax, I more think of lawn mowers
Why would you say that? A big lawn mover with a B&S engine sounds like a Lycoming (more or less). A 912 is a high rev, perfectly balanced 4 cylinder boxer that fires more often than than a 6 cylinder Lycoming. If anything, the sound feels like a Porche 911 at high revs. Anyway, this is getting very pseudo
mh wrote:
BTW: One of those accidents was in a WT-9
mh wrote:
VariEZ/Speed Canard are fast because they are small and light (a Lanceair 320 is over 60 KTS faster than the Speed Canard with the same engine),
The VariEze was designed as a racer with a VW conversion. It was designed with very low wing loading, and I believe did set records. Several years later it was re-designed and “commercialized” (plans were available) with a O-200. With a O-200 it cruses at 145 knots. The original Lancair 200 cruises at 165 knots. The Lancair has retracts though. The difference isn’t larger than can be explained by retracts alone.
LeSving wrote:
It’s an LSA, but can also be built as an experimental I believe, With a 120 HP Jabiru it cruises faster, longer and take more “cargo” than a C-172.
LeSving wrote:
It just that you cannot compare a 55 year old antique object with a new composite, glass cockpit airplane.
Well,
a) sure you can
b) If you don’t want to compare, then don’t do it :-)
LeSving wrote:
This is not true. This is a two seat version of the 430. It’s identical, except the rear seats are removed, and interior is redecorated.
The factory speaks only of the same fuselage(!).
I don’t know why some pilots assume mass limits were just for paper. If the designer wants to have a higher MTOM, he should just certify it. There is much more involved than just a static load test of a wing to up the MTOM. It’s a dangerous idea to assume otherwise and there have been several accidents based on just this belief in “structural magic”. (BTW: One of those accidents was in a WT-9).
europaxs wrote:
I can’t believe that, since many canard designs (P180 Avanti, the Rutans, Speed Canard, the Beech Starship) are all but slow.
@europaxs, the VariEZ/Speed Canard are fast because they are small and light (a Lanceair 320 is over 60 KTS faster than the Speed Canard with the same engine), the Avanti is a three surface aircraft and no sole canard (massive impact of canard loading) with a very high loaded main wing, the Starship isn’t that fast for the installed power, the B200 is just a couple of knots slower with more than 500 kW less power and
roughly the same payload.
