I to saw Phil's post about Dr. Drela's message. Because of my respect for
Dr. Drela's academic achievements (Masters in Aeronautical Engineering and
Professor at MIT) and his real world experience I immediately tried his
suggestion on my XP4 DLG. I reduced the differential from 55% to 0 and
increased the rudder to aileron coupling from 60% to 90% (yes I realize Mark
Drela flies without rudder coupling but my left thumb isn't as good as his).
The improvement was immediate. The plane track better and I was able to fly
in much tighter turns without falling off. I did feel that the nose wasn't
coming into the turn quite enough so I went to 100% rudder coupling with
ailerons and again a noticible improvement. But it still wasn't quite as
coordinated a turn as I wanted. So I added back 20% differential and for my
real world test it was perfect.
So after what I felt was a successful test with noticible improvement on my
DLG I decided to try reducing differential on my 128" Escape Lt. The
improvement from reducing differential and increasing rudder on my Escape
were just as obvious. End results were I went from 65% differential to 35%
and from 30% rudder coupling to 70%. As with the hand launch the
improvement was immediate.
So for me I would have to say Dr. Drela is right about the use of aileron
differential. Because though I don't fly with rudder and ailerons
uncoupled, as Mark Drela does, reducing differential with increasing rudder
coupling (to compensate for the weak left thumb) defiantly made an
improvement in the handling of my XP4 DLG and my 128" Escape Lt.
Just what I think
Maurice
----- Original Message -----
From: "Robert Samuels" <[EMAIL PROTECTED]>
To: <soaring@airage.com>
Sent: Sunday, June 12, 2005 2:56 PM
Subject: [RCSE] Still using aileron differential?
I recently followed a link provided by Phil Barnes to a message posted by
Dr. Drela. The message was that Dr. Drela did not use aileron (flaperon)
differential in DLG planes. The rational was that the differential caused
some unwanted pitch changes. My questions concern the application of Dr.
Drela's theory to the larger planes.
I wonder whether you all (experts):
1) still use aileron differential in 2 and 3 meter planes and
2) still couple the ailerons to the flaps (so they act as flaperons)
Robert Samuels............St. Louis
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