On 18 May 2004 07:15:20 -0700, (Paul Lee)
wrote:

:Richard Riley wrote in message . ..
:.............
: The difference between a 75 mph touchdown and a 90+ mph touchdown is
: significant. It's a 44% + increase in your momentum.
:
:Its a 44% increase in KE, not momentum (20%).

OK, let's be precise. On landing you intend to have 44% (plus) more
kinetic energy than other airplanes with exactly the same weight, wing
and engine. That's going to result in a 44% (plus) longer stopping
distance (as the brakes get hot, they also become less effective, so
it's not a 1:1 ratio). But that's once you're able to actually put it
on the runway. The high L/D that the canards enjoy means they tend to
float a lot down the runway, so when you're landing fast it's very
hard to touch down close to the numbers. Your retract gear will help
that, somewhat, by making the aircraft dirtier in the pattern, and
easier to slow down, than something with fixed and faired gear with
wheel pants. In any event, you will be landing much faster and longer
than other aircraft with identical performance.

:But so what? Both
:momentum and KE are relative only to other objects that shouldn't be
n the runway anyway.

And, as everyone knows, nothing ever goes wrong. There is never
anything on the runway that shouldn't be there. You never have to
land on a shorter runway than you intend, and you never land at higher
than expected density altitude.

:Turboprops, jets, have higher touchdown speeds.

Turboprops and jets have longer runway requirements, greater crash
protection requirements, more frequent inspections, and higher pilot
requirements. Most require 2 pilots. Having the landing requirements
of a jet, and the maintenance requirements and speed of a piston prop,
is not a good compromise.

:
:... I know the
: Matco W50L's are good, but do you want to get rid of that much of the
: margin?
:
:You mean brake wear? Typically canard flyers let it roll down the runway
:to save brakes.

No, I mean brake fade. The W50L disk is good for about 190k ft/lbs
each. The total energy that can be absorbed by a brake disk is
dependent on it's material and mass. Your airplane at full gross
weight and 95 mph has 340k ft/lbs of energy. So you are down under
10% for your safety margin. Don't land at Denver in the summer.

:The lighter vari-ez would have less problem
:with stopping distance - is that the canard that you fly?

It's a derivative of the Vari-Eze (proper spelling, we must be
precise, after all) but it's a little faster. I'll make you a deal.
When you get your plane done, I'll race you for pink slips, or a
bottle of 30 year old single malt. I'll even spot you extra 100 lbs.
in payload.

:
: Low speed handling is significantly improved by trailing edge fences,
: you may want to look into them.
: http://www.lsecorp.com/KlausInfo/Flowfence.htm
:
:They also have a problem with low speed roll control which is eliminated
:with the higher speed touchdown/takeoff - which also eliminates prop torque
:issues on takeoff.

At 200 hp, you won't have any issue with prop torque. And I've never
had a significant problem with low speed control, provided CG is
within the envelope. Just a touch of adverse yaw, below 110 kts.
Lower winglets (even small ones) help that significantly by damming
off the high pressure at the outboard end. Filleting the wing TE back
to the winglet TE with a pen-nib fairing (you can see it on the
Delaminator, at SnF or Osh), the standard vortalons, and Klaus' TE
fences all help lower the minimum airspeed.
:
:Even in a conventional planes with no flaps, you land more
:stable at higher landing speeds - a little more runway.

If you are landing on 8000 feet, or even 5000, it's not a problem.
Try putting in on 2500 over some trees at the end of the runway, it's
a problem.

:
:BTW Cozy Mark IV is about 200 lbs lighter than SQ2000.

Now that's strange, isn't it. Empty weight on a Cozy Mk 4 is
generally around 1100-1200 with a 2050 lb gross. On the Speed Queen,
you're looking at close to the same empty - 1100-1250. That makes
sense, its the same wing, the same engine, the same size fuselage, the
same materials. You save a little weight with vacuum bagging (not as
much as you'd think, but some) and loose a little with the retract
gear.

(And you gain a little in drag reduction with the retract gear, but
again, not as much as you might think. Fairing the legs and putting a
good set of wheel pants on the gear will eliminate 90% of the drag of
the gear. Retracting them gets rid of that last 10% - in exchange for
the weight and complexity of a retract system, increased insurance
rates and pilot requirements, a less forgiving failure mode and more
maintenance. There are a number of airplanes that fly slower with a
retractable gear than with a well faired gear.)

So, with the same empty weight, cabin dimensions, wing and engine, if
you have the same fuel load, baggage and passenger weight, the two
airplanes will take off, climb, cruise and land pretty much the same.

But the max gross weight is different - 2250 listed by Stan for the
Speed Queen. That's 10% more than the Cozy. Is it because the Speed
Queen is so much stronger than the Cozy? That seems unlikely,
composite aircraft - especially fiberglass aircraft - are generally
engineered to minimum stiffness requirements, rather than failure
loads. As a result, they usually end up much stronger than they need
to be. Their gross weights are dictated by performance, rather than
ultimate load.

So, basically, Stan is willing to accept less takeoff, climb, cruise
and landing performance at full gross weight than Nat, in exchange for
a higher useful load.

But there seems to be something wrong there, too. The KLS web site
doesn't seem to exist any more, but the old numbers I have in my files
show a sea level max gross climb rate of 2200 FPM. Since the Cozy,
with it's lighter max weight, only claims 1200 FPM at 2050 gross, the
Speed Queen number seems optimistic to me. The same is true on the
top end - SQ claims 258 MPH Vmax, Cozy 4 claims 220 mph and
demonstrates (CAFE test) 209.8 mph at 1668 lb, 29.2", 2691 rpm, 12.9
gph.

Can it be that the SQ fuselage shape is so superior to the Cozy that
it's flying 25% faster and climbing almost twice as fast? It seems
unlikely.

But all the power performance numbers aside, it's simply should not be
necessary to land at 90+ mph. Airplanes with exactly the same flying
surfaces and weight touch down at 75-80. When I say exactly, I mean
exactly - to the fraction of an inch in planform, with the same
templates, with the same modified Eppler airfoil on the mains, and the
same Roncz 1145 MS on the canard. (BTW, the MS stands for Mike and
Sally Mellville, no matter what you've been told)

Landing that fast increases risk, limits the airports you can land at,
and increases wear. If there is an accident of any kind, it's
significantly worse. The same accident that's survivable at 75 MPH
and 1 degree impact angle is not remotely survivable at 90 mph and 1
degree. That's the biggest reason to fly the left hand part of the
envelope, as well as the right.