Performance and Flap ranges

[the_gle...@msn.com]

So far as I can gather Schempp-Hirth have not published a polar curve for the Arcus. Do any others have such a thing? I would love to have input from folk who have had good soaring time in the Arcus.

 

Having an Arcus M with empty weight 555 kg, when flying with two normal size pilots and a bit of fuel on board my take-off mass will probably be about 750 kg. When I expressed concern to Tilo Holighaus about the high wing loading of about 48 kg/m2 he said he always flies the Arcus at max wing loading, and it would be fine. I have to say my experience so far suggests that it handles beautifully at this wing loading. Handling and performance would probably be improved by putting water in the tail to compensate for the weight of the back seat pilot (Biggo Berger suggested initially trying 2kg less than indicated by the manual) but I have not yet tried that - partly because it has been rather cold when I have taken it out.

 

I was recently sent a new version of the still provisional flight manual for the Arcus M, in which the speed ranges for different flap settings have changed slightly from the previous version. In this version, at max wing loading it says plus 1 for 54 to 65 knots, 0 for 65 to 81, and minus 1 for 81 to 97. It suggests that you may choose any of L, plus 2 or plus 1 for thermalling.

 

I am expecting that my UK conditions cruise speed will be 80 knots in flap 0 (the polar in the LX9000 gives 78 knots at Mc 1.0, 83 knots at Mc 1.4, and best glide at 66 knots).

 

How do these figures sound? Best glide as high as 66 knots? What speed and flap setting would give min sink? I went for plus 1 and 55 knots when I had some time in gentle hill lift.

[Philip Walker]

Mark

I haven't been able to get a polar curve from Biggo despite asking every six months for the last two years!

We usually fly the Arcus T without water which equates to 43/44 kg per m2, our empty weight is 60kg less than yours.

It was flown at a comparable wing loading to the M by Andy Davis and Barry in the open class nationals and although it handled very well the conditions caused them to dump the water during the flight. We do use tail water mixed with antifreeze to move the CoG backwards which helps climbing. We have tried L for thermalling but are not convinced, seems very draggy? 

Running the turbo on a clear still day last November and altering flap settings seemed to confirm the drag implications, best climb was at +2 52/55 kts which agrees with the flight manual.

Best glide usually 55/60kts at our wing loading?

Would be useful to have a polar curve though if anyone does have one?

Philip

[Jose Luis Chanes]

Dear Mark,

SH will not release the polar and they have their reasons for this so I was told that the closest to its actual performance is the Ventus 2cxt at 18 meters configuration.

Regards

Jose Luis

s/n 49 CC-AIG