Sender: <marv@lancaironline.net> (Marvin Kaye)
To: lml
Date: Sat, 11 Jan 2003 19:02:17 -0500
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Reply-To: <IIP@hawaii.rr.com>
From: "IIP" <IIP@hawaii.rr.com>
Subject: Wing loading
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I think the closest I got to the response I was looking for was from
Scott Kreuger, who discussed the ride characteristics of different wing
load airplanes. This is the essence of the "mystery": Why does the
static breaking limit of a wing have anything at all to do with flight
characteristics? (see Scott's formula at the bottom of his post). Still
waiting for a more in-depth answer to this...

In response to Skip Slater, we are not totally aerodynamically
challenged. The mere fact of writing "4,000 lbs." as a GW does nothing
to the characteristics of the airplane. The day before we got our
certificate, it was the same airplane. Skip points out an obvious fact:
As you increase actual GW, flight characteristics change. Doesn't matter
what the "POH" says the "Max. GW" is. A POH is not going to give you any
info above that weight because certified airplane manufacturers can't
risk people flying in those areas who don't understand the deteriorating
flight characteristics (and structural issues), and are likely to fly
their Cessna/Piper/Beech without due regard. Skip may have missed my
post where I explained that a primary reason for setting our GW at 4,000
was to avoid having to get a waiver from a FSDO for rare flights we
might make. We fully understand that those flights have to be made under
controlled conditions. The GW on your certificate is not a statement
that you intend to operate the airplane there with impunity. I suspect
95% of our flights will be made under 3,000 lbs.. BTW, there is no "Max.
GW" from Lancair. You set your own, and we consulted with Lancair, our
DAR, and others. Lancair has had many years of experience with the
airframe, but is not going to go out on a limb and generally encourage
people to increase GW. If you ask them how the "published" GW was
arrived at, you will find that it was kind of a subjective process, and
done years ago. I'm sure it was also a balanced judgment between utility
and safety. They will also tell you the airframe has been subjected to
all sorts of stresses beyond this published GW (and implicit wing
loading), with no problems. It has also been landed "repeatedly for
years" at weights around 4,000 lbs. and never had a gear or airframe
problem. Clearly, one has to be especially careful flying at advanced
GW. In my definition, "advanced" GW begins with the empty airplane and
goes up from there. As you increase GW, you'd better know what you're
doing.

It may also be of interest that Lancair does not really provide a "POH",
which people often refer to. What they provide is a nice binder. You
have to write the POH yourself. They give you some guidelines. I fear
that many builders do not go any further and never have a true POH. For
our part, we are writing a comprehensive POH for the turbine (Lancair is
also doing some flight testing to fill in their performance charts). We
are using the Piper Meridian POH as a model, and ours is going to be
more thorough than a certified airplane POH. We plan to do extensive
flight testing, both with a professional test pilot and ourselves. It
will certainly have more GW data points than you get from Piper (or any
of the others). IMHO, if you are going to build an experimental
airplane, this is the kind of rigor you need to plan on AFTER the
airplane is built.

Brian Barbata