Re: The Aviators Goes Gliding (at last)

[Martin Gregorie[_5_]]

On Fri, 07 Jun 2013 09:04:55 -0700, Charlie Papa wrote:

> He was surprised at the challenge the aero tow posed, but learned the
> attitude/speed control, then gentle turns, to steeper ones, and he
> positively shone at Dutch Rolls.
>
Curiosity: what do you mean by "Dutch Rolls"?

I understand a Dutch Roll as meaning the coupled wing rocking and yawing
instability shown by an aircraft with a vertical tail volume that's a
little too small for stable flight, i.e. the fin moment is too short and/
or the fin area is too small.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Ralph Jones[_3_]]

On Sat, 8 Jun 2013 19:59:19 +0000 (UTC), Martin Gregorie
> wrote:

>On Fri, 07 Jun 2013 09:04:55 -0700, Charlie Papa wrote:
>
>> He was surprised at the challenge the aero tow posed, but learned the
>> attitude/speed control, then gentle turns, to steeper ones, and he
>> positively shone at Dutch Rolls.
>>
>Curiosity: what do you mean by "Dutch Rolls"?
>
>I understand a Dutch Roll as meaning the coupled wing rocking and yawing
>instability shown by an aircraft with a vertical tail volume that's a
>little too small for stable flight, i.e. the fin moment is too short and/
>or the fin area is too small.

In the context of glider training, it's a shameful misnomer for an
exercise in which you roll alternately left and right while keeping
the nose on a point -- thereby learning to cope with the strong
adverse yaw of long wings.

[Bill D]

On Saturday, June 8, 2013 4:37:52 PM UTC-6, Ralph Jones wrote:
> On Sat, 8 Jun 2013 19:59:19 +0000 (UTC), Martin Gregorie
>
> > wrote:
>
>
>
> >On Fri, 07 Jun 2013 09:04:55 -0700, Charlie Papa wrote:
>
> >
>
> >> He was surprised at the challenge the aero tow posed, but learned the
>
> >> attitude/speed control, then gentle turns, to steeper ones, and he
>
> >> positively shone at Dutch Rolls.
>
> >>
>
> >Curiosity: what do you mean by "Dutch Rolls"?
>
> >
>
> >I understand a Dutch Roll as meaning the coupled wing rocking and yawing
>
> >instability shown by an aircraft with a vertical tail volume that's a
>
> >little too small for stable flight, i.e. the fin moment is too short and/
>
> >or the fin area is too small.
>
>
>
> In the context of glider training, it's a shameful misnomer for an
>
> exercise in which you roll alternately left and right while keeping
>
> the nose on a point -- thereby learning to cope with the strong
>
> adverse yaw of long wings.

http://en.wikipedia.org/wiki/Dutch_roll

[Martin Gregorie[_5_]]

On Sat, 08 Jun 2013 16:03:44 -0700, Bill D wrote:

> On Saturday, June 8, 2013 4:37:52 PM UTC-6, Ralph Jones wrote:
>> On Sat, 8 Jun 2013 19:59:19 +0000 (UTC), Martin Gregorie
>>
>> > wrote:
>>
>>
>>
>> >On Fri, 07 Jun 2013 09:04:55 -0700, Charlie Papa wrote:
>>
>>
>> >
>> >> He was surprised at the challenge the aero tow posed, but learned
>> >> the
>>
>> >> attitude/speed control, then gentle turns, to steeper ones, and he
>>
>> >> positively shone at Dutch Rolls.
>>
>>
>> >>
>> >Curiosity: what do you mean by "Dutch Rolls"?
>>
>>
>> >
>> >I understand a Dutch Roll as meaning the coupled wing rocking and
>> >yawing
>>
>> >instability shown by an aircraft with a vertical tail volume that's a
>>
>> >little too small for stable flight, i.e. the fin moment is too short
>> >and/
>>
>> >or the fin area is too small.
>>
>>
>>
>> In the context of glider training, it's a shameful misnomer for an
>>
>> exercise in which you roll alternately left and right while keeping
>>
>> the nose on a point -- thereby learning to cope with the strong
>>
>> adverse yaw of long wings.
>
Thanks. I understand "Rolling on a heading". As you say - a standard ab-
initio glider handling exercise.

> http://en.wikipedia.org/wiki/Dutch_roll
>
The majority of that article covers what I understand by the term.

FWIW its desirable for a competition free flight towline glider to be
just on the right side of borderline Dutch Roll stability because that
maximises its ability to self-centre in lift. The traditional way to set
up a new design is to get it trimmed to a nice glide before you start
cutting pieces off the fin. Once it shows the beginning of a dutch roll
you stick the last piece back on. Then you go home, measure the remaining
fin and make it a nice new one of exactly that size and with a similar
aspect ratio.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |