Dear Nigel.
Thank you for letting us know about your findings. I think you should make
your spreadsheet available to club members. It's vital to observe and be
able to calculate all the variables which affect takeoff and landing
performance - especially on a limiting runway.
Cheers,
Hans.
----- Original Message -----
From: "Nigel Charles" <72016.3721@compuserve.com>
Subject: Runway length
> Message text written by "Paul Atkinson"
> >I am just wondering what you 914 powered flyers consider to be an
adequate
> minimum runway length. The figure I have generally been quoted is 450
> meters
> or 1500ft. I get the impression that this is a generic figure that will do
> for any Europa regardless of powerplant.
> Having read several accounts of 914 powered Europas with VP props leaping
> into the air like homesick angels, I wonder if any of you are happy
> operating from shorter strips, and how much benefit there is from the
extra
> power and VP prop over say a 912 with fixed pitch. For comparison mine is
a
> monowheel classic which will have a Wilksch WAM120 and an MT prop, and I
> will be operating from elevations of 500' or less, most of the time.
> Any comments gratefully received.<
>
> I agree with the comments so far on this subject. Be aware that as there
> are several factors, all of which can affect take-off run and some of
which
> can affect landing run. When some of these are added together in certain
> conditions it is possible to end up with with distances which are double
> the standard numbers. The CAA provide an excellent booklet giving
> recommended factors for this. Although they only give an approximate idea
> it provides a way of predicting whether the length available is
sufficient.
> Remember that the take-off distance available to 50ft (TODA) can be more
> relevent than the take-off run available (TORA) if there are any trees or
> even hedges at the end of the runway.
>
> The factors and their affect on take-off and landing run and distances
> required (TORR/TODR & LRR/LDR) as published by the CAA are as follows:
>
> Factor TORR/TODR Correction LRR/LDR Correction
> Weight 2% per % 1% per %
> Temperature 1% per deg C 0.5% per %
> Pressure Alt 1% per 100ft 5% per 1,000ft
> Headwind 7% per 5kt 7% per 5kt
> Tailwind 20% per 5kt 20% per 5kt
> Up Slope 5% per % 2.5% per %
> Down Slope 2.5% per % 5% per %
> Dry Grass Add 20% to hard rwy figures Not
> published
> Wet Grass Add 30% to hard rwy figures Not
> published
> Soft Ground Add 25% to hard rwy figures Not published
>
>
> To apply these factors the performance for an individual aircraft needs to
> be measured for a known set of conditions (ideally fairly standard
> conditions ie. typical average weight, 15 degC, typical airfield pressure
> alt, zero wind or small head component, level hard runway). When
> subsequently calculating the performance on the day remember to apply the
> corrections in the correct sense. To avoid a lot of work with a calculator
> I have produced a spreadsheet which will apply the corrections. This sheet
> also does the weight and balance calculations having inserted fuel load
(in
> volume), pilot & pax weights and baggage weight. If anyone is interested I
> could look at making it available. Naturally it would be free to Europa
> Club members but a small donation to the club funds would be appreciated
> from non-members.
>
> Finally when it comes to the actual take-off in limiting conditions the
> following two checks during the take-off run will help assess the stop-go
> decision as applied to Europas:
>
> 1. 25kts by 25% TORA
> 2. 35kts by 50% TORA
>
> If these are not acheived the take-off must be aborted. Of course to
> measure this markers need to be placed or the positions otherwise defined
> along the runway.
>
> Whilst most of us rarely operate close to the performance limits regularly
> it is nice to know how much margin you have in hand. For instance if a
> Europa needs 200m take-off run in standard conditions at MAUW, it will
need
> 400m with the following conditions (Temp +30degC, Press Alt 3,000ft, 4kt
> tailwind, 2% up slope, soft grass). If there is a hedge at the end of the
> runway the standard TODR might be 300m so to clear the hedge in the above
> conditions you would need 600m. That is without a safety factor of 33%
> which the CAA recommends so the margins can become reduced quite
> significantly.
>
> Food for thought?
>
>
> Nigel Charles
>
>
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