On Saturday, April 21, 2012 at 12:26:44 PM UTC+12, Bob Gibbons wrote:


Every Ventus cT manual that I have looked at says the max weight with
the engine in is 430 kg regardless of the span. With the engine out,
500kg at 16.6. and 17.6m respectively

Cheers
Colin

Colin, you are correct in quoting the handbook. Several of us actually
discussed this apparent contradiction with Klaus Holighaus on a visit
a number of years ago.

He agreed that it so long as the non-lifting limit is followed, it
makes no difference whether the engine is in or out.

The engine represents a fuselage (non-lifting) load on the airframe,
the cause of this non-lifting load should not be a factor in the
overall gross weight, so long as the non-lifting limit is observed.

Bob

Sorry, but I'm still confused.

To my mind, a non-lifting limit is a hard limit, defined by the mechanical limit of the four wing-root pins. If you remove the engine (and fuel tank and engine battery) then this limit should not change; you've taken weight off the pins so can add more pilot weight etc. (ignoring balance considerations for the moment).

What the flight namual seems to be implying (and thanks, Colin, for the discussions) is that there are some wing bending issues. The (non-turbo) Ventus was designed for a MAUW of 500kg and the wing will cope fine with a max non-lifting weight of 255kg (for example - it varies depending on the model). What the manual seems to be implying is that SH then wanted to put a turbo in but came up against the (true) load limit of the wing pins, as well as some bending moment limitations on the wing, but the market need for a turbo version was great so they put a 430kg limitation on the MAUW.

I know that there are cT/bT pilots out there who ignore the 430kg limit and ballast up to 500kg with no issues. I'm asking the Collective Wisdom of y'all whether:
a) my reasoning above is correct;
b) whether to take the numbers in the flight manual with a grain of salt, bearing in mind the discussions with Herr Holigaus; and
c) whether it's worth asking SH to revise the flight manual to clear up the confusion; or
d) to obey the flight manual at all times and loads.

Answers on a postcard...

DH
TX