A friend of mine is building a Legacy and has a question....

John, it's my understanding that you need a little toe out on a tail
dragger and a little toe in on the tri-gears.


I agree that taildraggers will need toe out and tricycle kit toe in.

This is since:-

Taildragger with toe out.
You are going along the ground straight and level when some
perturbation causes the aircraft to point left of its track.
The aircraft will tend to roll to the right and the vertical
force on the right hand wheel will increase at the expense
of the left hand wheel (since the aircraft still weights the same).
Since the right hand wheel is toed out the aircraft will
begin to turn to the right thereby moving everything back
towards balance.
In a word there is stability.

Taildragger with toe in.
You are going along the ground straight and level when some
perturbation causes the aircraft to point left of its track.
The aircraft will tend to roll to the right and the vertical
force on the right hand wheel will increase at the expense
of the left hand wheel (since the aircraft still weights the same).
Since the right hand wheel is toed in the aircraft will
turn further to the LEFT thereby reinforcing the
original perturbation.
In a word there is instability.


Tricycle with toe out.
You are going along the ground straight and level when some
perturbation causes the aircraft to point left of its track.
The aircraft will tend to roll to the right and the vertical
force on the right hand wheel will increase at the expense
of the left hand wheel (since the aircraft still weights the same).
Since the right hand wheel is toed out the aircraft will
turn further to the LEFT thereby reinforcing the
original perturbation.
In a word there is instability.


Tricycle with toe in.
By similar argument - stability



I have experienced severe oscillation in the case of a trailer
being towed behind a car where the trailer had a lot of toe in due to
crash damage.

After a bit of thinking I realised what might be causing the issue and
reduced the amplitude or the oscillation at any particular speed
by letting some air out of the tires of the trailer. This
allowed the tyres to operate at a greater slip angle.
I could then proceed at 28mph instead of 20mph a big improvement.

I have never previously found any use for this
knowledge ^h^h^h^h^h^h opinion.
Hope it is right and helps out.