From: svoboda@rtsg.mot.com (David Svoboda)
Subject: Re: trigear type vs bigear type
Organization: Motorola Inc., Cellular Infrastructure Group
Distribution: rec
Date: Wed, 2 Sep 1992 23:25:23 GMT

In article <Btp515.I1B@world.std.com> jlw@world.std.com (James L Walker) writes:
|
|Trikes will land easier "hot" (ie. fast ground speed) than a
|taildragger.  

No, I don't think so.

|When a taildragger rests on the ground the wing's angle
|of attack is high because it's tail is resting on the ground.  When
|the plane is comming in fast, the angle of attack is low so the mains
|touch the ground first and the tail settles in later.  If the tail
|settles in too quickly, the increased angle of attack will generate
|enough lift to get the plane airborne again.  This accounts for the
|"bounce" when you land a taildragger to hard.  

Well, except for the fact that the landing gear is very close to the
CG of the airplane, so it takes quite a hard landing to bounce the
airplane back into the air.

A taildragger will more gracefully handle a "pancaked" landing, in
which the model is flared to a stall while still above the ground, and
the airplane sort of drops nearly horizontally.  This is the most common
sort of botched landing by a beginner.  The likely event in that case 
in a nose-over and a broken prop.

|If you are really good
|you can land a taildragger really fast by putting the mains gently on
|the ground and then using down elevator to throw the tail up.  The
|force of the air over the tail will keep the plane from nosing over
|until you are going slow enough to drop the tail.  

You don't have to be really good to do this.  Simply freeze the elevator
at the position it was when you touched down (don't continue to flare)
and most models will stay on the mains.  The important thing is to
have a small rate of descent when you touch down.  This minimizes the
positive pitching force due to the tail moment.  But that pitching
force is nearly independent of landing speed (except if you fly from
grass, where the drag on the wheels can cause a nose-over if you land
too fast).

|The easy way to
|land a taildragger is to make a "three point" landing where the plane
|is going slow enough that the tailwheel will touch the ground at the
|same time as the mains.  

This is only easy if you are good enough to bring all the elements of
landing together perfectly.  Most beginners (and most sport fliers) can't
do this so well.

|Of course in a trike the plane rests on the
|ground with a nice low angle of attach so you can grease it in very
|fast with very little bounce.

No.  A tricycle model is VERY easy to bounce, esp if the wing, at rest
on the ground, is at any kind of positive AoA.  See, if you bring in a
trike too fast, the flare angle is less than the rest angle, so the nose
gear touches first.  Since the nose gear is so far from the CG, it easily
lifts the nose, which increases the AoA and produces more lift, which lofts 
you back up into the air.  Then the speed lowers a bit, the nose drops (you 
are a bit slower by now, and do not give enough elevator to keep it up), 
the nose- wheel touches, and, here we go again.  And again.  And again.

The operative quantity when landing a tricycle gear model is airspeed.  You
need to bleed off enough airspeed to make certain the main gears touch
first.  You can have a pretty high rate of descent, as long as your nose
is up.

If your taildragger sits tail-down on the ground, you will be amazed
at how much easier your landing get if you lengthen the main gears
a bit.  (This is for all the Flightstar 40 pilots. :-)

|Because of the naturally high angle of attack, a taildragger will
|leave the ground at a naturally slow speed with a short roll-out.
|This is an advantage if you learn to properly handle the rudder to
|keep the plane on track.

But presents a challenge to the beginning flyer to keep the airplane on
the ground long enough to build up a comfortable airspeed.  Properly set
up, a tricycle will stay stuck until you decide to take off.

For all these reasons, trainers are often equipped with tricycle gears,
and taildraggers are usually reserved for slightly more advanced flyers.
On the other hand, there are some fine taildragger trainers out there.

		Dave Svoboda, Palatine, IL