Can only CFIs teach flying?

On Monday, October 7, 2019 at 5:07:25 AM UTC+13, Dan Marotta wrote:
I can roll up into a 90 degree bank and, if I don't apply up or down
elevator, the plane won't turn.Â* The nose will simply knife downward..Â*
So, am I clinging to something?Â* Think vectors and the vertical and
horizontal components of lift.

If you are flying straight and level and then roll into a 90 degree bank while keeping the same elevator position then you will enjoy turning with 1G of centripetal acceleration. Until the nose falls through. And then you'll enjoy a 1G pullout (more as the speed builds).

The only way you can *not* turn in that 90 degree bank is if you actually moved the stick forward to the position that would give you a zero-G pushover in level flight.

On Tuesday, October 8, 2019 at 3:28:04 AM UTC-4, Bruce Hoult wrote:
On Monday, October 7, 2019 at 5:07:25 AM UTC+13, Dan Marotta wrote:
I can roll up into a 90 degree bank and, if I don't apply up or down
elevator, the plane won't turn.Â* The nose will simply knife downward.Â*
So, am I clinging to something?Â* Think vectors and the vertical and
horizontal components of lift.

If you are flying straight and level and then roll into a 90 degree bank while keeping the same elevator position then you will enjoy turning with 1G of centripetal acceleration. Until the nose falls through. And then you'll enjoy a 1G pullout (more as the speed builds).

The only way you can *not* turn in that 90 degree bank is if you actually moved the stick forward to the position that would give you a zero-G pushover in level flight.

You haven't tried explaining this to a student, have you? :-)

Here's what really happens if you bank to 90 degrees while holding the elevator control in one place: the nose drops starts dropping the moment you begin to bank, the aircraft begins to accelerate and the g forces increase. There is -no- period of time that "you will enjoy turning at 1G of centripetal acceleration."

Langewiesche (Stick and Rudder) has it right. Think of the elevator control as your angle of attack control. Chapter one, "How a wing is flown". What a great place to start the explanation of the art of flying.

best,
Evan Ludeman

At 11:44 08 October 2019, Tango Eight wrote:
On Tuesday, October 8, 2019 at 3:28:04 AM UTC-4, Bruce Hoult wrote:
On Monday, October 7, 2019 at 5:07:25 AM UTC+13, Dan Marotta wrote:
I can roll up into a 90 degree bank and, if I don't apply up or
down=20
elevator, the plane won't turn.=C2=A0 The nose will simply knife
downwa=
rd.=C2=A0=20
So, am I clinging to something?=C2=A0 Think vectors and the vertical
an=
d=20
horizontal components of lift.
=20
If you are flying straight and level and then roll into a 90 degree
bank
=
while keeping the same elevator position then you will enjoy turning with
1=
G of centripetal acceleration. Until the nose falls through. And then
you'l=
l enjoy a 1G pullout (more as the speed builds).
=20
The only way you can *not* turn in that 90 degree bank is if you
actually=
moved the stick forward to the position that would give you a zero-G
pusho=
ver in level flight.

You haven't tried explaining this to a student, have you? :-)

Here's what really happens if you bank to 90 degrees while holding the
elev=
ator control in one place: the nose drops starts dropping the moment you
b=
egin to bank, the aircraft begins to accelerate and the g forces
increase.
=
There is -no- period of time that "you will enjoy turning at 1G of
centrip=
etal acceleration." =20
=20
Langewiesche (Stick and Rudder) has it right. Think of the elevator
contro=
l as your angle of attack control. Chapter one, "How a wing is flown".
Wh=
at a great place to start the explanation of the art of flying.

best,
Evan Ludeman


Funnily enough.... the assumption is made that the tail is acting with a
'downward' force, counterbalancing the mass ahead of the lift... with
neutral stability, the elevator actually exerts no force in pitch. And it
is also possible that the tail generates lift to support a rearward C of G
!!!
Banking to 90 deg and holding that angle changes the whole dynamic of the
weight and lift distribution, the fin and rudder now come out to play....
!!!

On Tue, 08 Oct 2019 17:37:00 +0000, James Lambert wrote:

Funnily enough.... the assumption is made that the tail is acting with a
'downward' force, counterbalancing the mass ahead of the lift... with
neutral stability, the elevator actually exerts no force in pitch. And
it is also possible that the tail generates lift to support a rearward C
of G !!!

Indeed, but every glider I know the W&B for has the CG in front of the CL
at all flying speeds (CL approaches 30% MAC at the stall, but as airspeed
rises it moves further back.

I'm far from certain that I'd want to fly anything with the CL at or
behind the CG. Here's why:

I know quite a lot about trimming small aircraft with rear CG positions -
virtually all competition free flight models are set up this way because
having both wing and tail providing lift adds efficiency, especially if
the tail is flying at its minimum drag AOA. Which is the case for a well-
designed model. Numbers: the F1A gliders (F1A is the international class
for towline gliders - typically 2.2-2.7m span, min weight 420g) all flew
best with the CG at 55% of MAC, a main wing AOA of about 8 degrees and
the flat bottomed lifting tail at about 3.5 dergees AOA. The stability
was good - it has to be to handle rough thermals and the turbulence you
get below 50-100ft on a windy day. But I would not want to fly an
aircraft with that trim set-up because the trim sensitivity was extreme -
my tail had a 90 mm chord and I used a 10BA bolt as the trim adjuster
(thats 1.7mm diameter, with a 0.35mm pitch). I could easily see the
effect of half a turn on the trim (both still air duration and dynamic
recovery from upsets) and so used to fine tune them in terms of 1/4 turn
adjustments. That gives a 0.09mm movement at the TE of a 90mm chord
tailplane, so a very small angular change indeed. 1-2 turns took it from
stalling to an under-elevated over fast glide.

On the other hand, similarly sized models with the CG in front of the CL,
so flying with down force on the tail, are easy to trim by adding or
removing pieces of 0.8mm or 1.6mm balsa under the TE of the tailplane.

Bottom line: I would not want to hand-fly anything with that amount of
pitch sensitivity so am happy to leave anything with its CG behind the CL
in the hands of other, better and braver pilots than myself.


--
Martin | martin at
Gregorie | gregorie dot org

On Tue, 08 Oct 2019 19:41:20 +0000, Martin Gregorie wrote:

I'm far from certain that I'd want to fly anything with the CL at or
behind the CG. Here's why:

Errrrm: this should, of course, read:

I'm far from certain that I'd want to fly anything with the CG at or
behind the CL. Here's why:


--
Martin | martin at
Gregorie | gregorie dot org