Just how many decimal point digits do you want to compute the TAS to?
Seriously, there is no such thing as a perfect day (except in hindsight of
course). I don't believe the precision and reproducibility of non-military
methods would approach 1%.
Cheers,
Ira
On 7/23/01 2:48 PM, "Alan Stewart" <alan.stewart@blueyonder.co.uk> wrote:
>
> Meanwhile, back on Earth...
>
> I think most ordinary mortals with 'attitude' will fly at speeds similar to
> the ones I've quoted.
>
> ..and of course, it's not for me to stand in judgement over the performances
> which other claim.
>
> One thought though. TAS based on GPS readings is easily over-estimated.
> Leaving aside the density/altitude calculations which are frequently aired,
> the most common reason is failure to accurately compensate for wind.
>
> It is essential to either:
>
> 1/ Fly on a day with zero wind.
> 2/ Fly DIRECTLY into and away from the wind vector. (pretty difficult to
> achieve).
> 3/ Use a recognised formula to produce TAS from trigonometry.
>
> I suspect that most GPS/TAS calculations which are not performed with
> rigourous attention to detail will be over-estimated by a few knots. Arent
> simple 'two-way averages' and 'rectangular tracks' are likely to be wrong
> unless the weather is calm ?
>
> I have an Excel spreadsheet (4Kb) which relies on averaged GPS speeds from
> three, accurately flown tracks. The resulting TAS should be fairly close to
> the true airspeed provided:
>
> 1/ The aircraft is at constant altitude throughout the test.
> 2/ The track and GPS speed are fairly constant. (requires a day without
> gusts and thermals)
> 3/ The engine RPM is constant.
> 4/ The wind direction and speed are constant throughout the test period.
>
> I found that I needed to fly for about 5 minutes per sector, in order for
> the GPS reading to average out. I also found it quite hard to hold a track
> to within +- 1 degree.
>
> If anyone would like to examine and add constructive criticism of the
> method, I'll gladly refine it. I'd like to derive a method that is as fair
> and as accurate as possible.
>
> What is the most simple and ACCURATE way to determine TAS ?
>
> Alan
>
>
>
>
> -----Original Message-----
> From: owner-europa@post.aviators.net
> Subject: Re: Realalistic airspeeds
>
>
> Au contraire, the performance of Kim's aircraft is indeed relevant for the
> rest of us even if it is only as a benchmark.
>
> Although Kim's build philosophy may include a religious attention to detail
> he makes no claims to being a deity, and no god-like powers would be needed
> to duplicate his accomplishments. It's all a matter of attitude. N111EU
> was built light, and incorporates drag reducing modifications beyond the
> factory's speed kit, but any mortal builder could duplicate what Kim has
> done. His aircraft may be relatively Spartan (emphasis on relatively,
> because it is certainly not austere) compared to, for example, Dennis
> Vories' XS (whose interior could be compared to a Lexus) but that's
> essential to keeping it light. Since the proverbial free lunch still does
> not exist, each of us must choose to build light and go fast, or build plush
> and sacrifice speed. Just because most builders seem to prefer to have a
> little more of the plush stuff that adds weight and decreases speed is no
> reason to exclude N111EU as a valid example of the Europa's performance.
>
>
> Best regards,
>
> Rob Housman
> A070
>
> ----- Original Message -----
> From: "LTS" <lts@avnet.co.uk>
> <europa@avnet.co.uk>
> Subject: Re: Realalistic airspeeds
>
>
>> I don't think looking at the performance of Kim Prout's aircraft is
>> particularly helpful, unless you're a god. Nobody else seems to have come
>> near to the performance acheieved by Kim!!!!! I think this guy wants to
> know
>> what he can expect to acheive if he buys or builds a regular 914 Europa
> Tri
>> gear. There are several out there and we have sold props for at least two
>> 914 trikes and one 914 mono. I am sure someone can give him typical
> actuals.
>>
>> Jerry
>
>
>
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