Re: Tail wheels


Peter Harris <peterjfharris@...>
 

Fellers,

In my opinion the source of most ground handling problems is a case of PIO
and requires close attention to the far end of the runway. It is all too
easy if there is a bump or distraction, to shift attention to the foreground
and then PIO will happen.

I think it is important to decide if you are going to steer with the tail
wheel , or steer with the brakes. (The rudder will be relatively
ineffective) Any confusion about that is another recipe for PIO.

If it is decided to steer with the tail wheel then a grippy pneumatic tyre
is my choice. It will slip and the tail spring will flex enough to
accommodate any excessive input early in the roll and it becomes more
effective as the ground roll continues.

If it is decided to use brakes for steering be aware that the tail will
easily lift and this will mean a loss of control aft of the CG.

During acceleration inertia force acts aft of CG and the aircraft is stable
and easily steered but during deceleration the inertia is acting forward and
will pull the aircraft off line unless the tailwheel is securely gripping
the tarmac. The use of brakes at this time will add to the forward
destabilizing torque and with a loss of tailwheel contact that is when
trouble can begin. But using full aft elevator during the ground roll helps
to keep weight aft of CG and to load the tail wheel for stability.

The smartest part of our brain is the brain stem which is automatically
programmed to ride a bike or steer a Quickie and we can learn to use all
kinds of equipment in this way and never be able to really explain how it is
done. Each Qdragger driver is familiar with his own set up and will swear by
it. But IMO it is best to think about the physics and try to keep your bird
as simple as possible and don't forget the role of the pilot in PIO.

Peter



_____

From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of
Allan Farr
Sent: Thursday, 30 November 2006 6:50 AM
To: Q-LIST@...
Subject: Re: [Q-LIST] Tail wheels



Thanks Mike. Less sensitivity to cracks, debris, etc, is presumably partly
because of the rounded profile of the pneumatic tyre as opposed to the
squared off profile of the solid tyre.
Regards
Allan Farr
Q2 Rev (maybe flying next yr)

----- Original Message -----
From: Mike Perry
To: Q-LIST@yahoogroups. <mailto:Q-LIST%40yahoogroups.com> com
Sent: Wednesday, 29 November 2006 14:53
Subject: Re: [Q-LIST] Tail wheels

Allan:

I think what happened is that Jim Hamm, Bob Farnum and Jim Patillo were
looking for a way to install a tailwheel which was steerable over a narrow
range and otherwise full swivel. The available model happened to be
pneumatic.

The pneumatic tire might be more grippy but it is also less sensitive to
cracks, grooves and debris on the runway.

This is my understanding from listening to Jim P and Bob over the last
several years, I hope it's not too inaccurate.

Mike Perry
Not flying and currently not building :-(

At 03:46 PM 11/28/2006 +1300, you wrote:

If it's true that "Part of what the JB 6-pack does is desensitize the
tailwheel to avoid over-controlling", it seems to me that changing the
standard solid tail wheel for a more grippy pneumatic one would go against
that argument (by increasing the sensitivity).
Allan Farr
Q2

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