Mel,
Common European (including UK) airworthiness codes demand that compliance
with the strength requirements is demonstrated
at two levels (at least). The first, limit, loads are the maximum which the
aircraft is likely to see in flight. In the normal category this is usually
+4g and -2g. During application of the loads, all the bits must work
properly. After removal of the loads, no permanent deformation is
permitted.
In addition a safety factor of x 1.5 is applied, for all construction
methods, to bring the levels to ultimate loads. This is a normal safety
factor applied where human life is at stake; it takes care of several
things: variation in materials, variation in materials' data, variation in
construction, degradation during service, errors in test, errors in setting
the standard (I suspect). After the ultimate tests, permanent deformation
is permitted but not failure.
For plastic aeroplanes an additional "super factor" is applied on top of the
above safety factor. Normally this is another x 1.5 and it takes care of
the additional materials' variability of which composite assemblies are
constructed, and reductions in the strength of the plastic when it's hot and
wet. If the applicant can demonstrate that he has used conditioned
(hot/wet) data for his analysis then he is permitted to reduce the plastic
superfactor to 1.2 or 1.3. If he has no analysis and has to demonstrate
compliance by test alone (and he cannot usually get the whole aeroplane in a
hot wet chamber), then he must apply loads of eg. +4g x 1.5 x 1.5 = 4g x
2.25 = 9g without failure.
The successful completion of such tests or analyses does not however clear
the aircraft for 9g operations, but only for 4g operations with the required
safety factors.
No idea what the colonials do.
Dave Simpson
-----Original Message-----
From: Mel Ewing <mele@freemail.com>
Date: 24 January 2000 17:04
Subject: Re: Europa Questions Again
>It was/is my understanding that composite aircraft have to under go higher
>load tests in Europe (U.K.). I believe it is 2.25, unlike the 1.5 in the
>U.S. So in order to be certified at 3.8 it has to be stressed to 8.55g,
>which Europa has done. In the U.S. that is good for 5.7g .
>
>Anyone care to confirm or deny?
>
>Mel Ewing
>"That Tri-Gear sure looks nice...."
>
>>Hi all again,
>>
>>Thanks to everyone who responded to my earlier post. There
>>are a lot of friendly people on this list!
>>
>>In my earlier post I asked about the aerobatic rating of the
>>Europa, but nobody had any comments on that. Maybe if I gave
>>more details I would get a response.
>>
>>FAR 23.337 lists three categories of operation for aircraft
>>in the US, based on limit load (G) capability.
>>
>> Normal +3.8G -1.52G
>> Utility +4.4G -1.76G
>> Aerobatic +6.0G -3.0G
>>
>>Now the Europa Aircraft website lists the limit load
>>rating as:
>>
>> Europa XS +3.8G -1.9G
>>
>>This would then place it in the "Normal" category and not
>>even allow steep turns. Am I missing something?
>>
>>A related question is that the "standard" ratio of limit
>>load to ultimate load is 1.5. The Europa data is much
>>more conservative than that but even if you divide the given
>>ultimate load by 1.5, you still won't make the aerobatic
>>category.
>>
>>Thanks
>>
>>Bob Collins
>>
>>
>>Collins wrote:
>>>
>>> Hi all,
>>>
>>> I am researching available airplanes to build and the Europa
>>> looks like a potential winner. The San Francisco bay area
>>> here has very expensive hanger rates and I am attracted to
>>> the idea of a trailerable aircraft. The only seemingly
>>> viable choices are the Europa and the Sonex, which both have
>>> sailplane-like wing mounting.
>>>
>>> Both planes have their pluses and minuses and I would like
>>> to hear opinions on both, as well as comments on any other
>>> competing designs. I do however have a couple of
>>> specific questions about the Europa.
>>>
>>> The review articles about the Europa talk about doing
>>> aerobatics but the G limit loads listed on the Europa
>>> website do not qualify for the aerobatic category. Is/was
>>> there a change in design direction?
>>>
>>> Thanks
>>>
>>> Bob Collins
>>> Sunnyvale CA USA
>>
>
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