Lift Coefficient Meter?

Has anyone built, or ever come across, a lift coefficient meter as outlined in Reichmann's 'Streckensegelflug' (Cross-country Soaring)? It works by attaching a dedicated pitot to a dedicated static via a restrictor and a (similar to a Cosim vario) tapered glass tube and ball. The ball seems to have a far better understanding of mathematics than I do (see Reichmann for details) and rises and falls according to the lift coefficient.

It is hard to believe anything so simple could be so useful - but does it actually work in practice?

I guess that it would only work accurately in the horizontal postion as gravity must be playing a part in the position of the ball - if so is there another kind of flow meter that would work - and in all attitudes?

Thanks,

John Galloway

You could try a vario that requires a flask to work (these meters work by measuring flow). Connect the pitot to one port, the static to the other. Start out with a small restrictor, I suppose, to avoid damaging the meter.

I'm not sure I understand what your getting at Eric, But if you hook Pitot to one side of a vario and Static to the other side, you are going to slam the needle against the stop, so hard that it will probably bend the needle. JJ

Years ago in our gliding club PIK ry, couple of mambers constructed a Cl meter, which was propably similar, what you are looking. It was based on a U tube filled with liquid, and the level difference of liquid was measured electronically.

It worked quite nicely, as far as I heard.

Aki Suokas

The March 1975 issue of SOARING had an article about a Lift Coefficient Meter designed by Daniel J. Altstatt. The short story is that the L/C meter allows you to fly at minimum sink while thermalling regardless of the speed and load factor by indicating the appropriate angle of attack.

Many of the airplane's (powered or unpowered) critical performance numbers are really angle of attack numbers:

The stall occurs at a particular angle of attack.

The smallest power-off descent rate occurs at a particular angle of attack.

The best power-off glide ratio occurs at a particular angle of attack.

The best rate of climb occurs at a particular angle of attack.:

Dan Altstatt is still shown in the SSA soaring directory can likely be reached to discuss the instrument. I can provide a copy of the article for folks who are interested. Its a clever device because it shows the solution graphically without regard to numbers and would be used to optimize thermalling flight.

Whether it provides enough of an increment of improvement over seat of the pants flying with conventional instrumentation is beyond me.

Pete Brown