PW-5 longitudinal pitch oscillation

Am considering buying a PW-5 as my first single-seater for a variety of reasons, but the one aspect I don't like is that in rough air the tail is easily pitched up in flight from unexpected gusts once I'm off tow. This one's been weighed & balanced recently and its CG is perfectly centered within its designed range.

I'm on the light side for a glider pilot, so in two-seaters I often add extra ballast when my second seat is empty. However, I see these tail-high excursions even with extra ballast in one of the Grob 103s I frequently fly solo in (but not the other Grob 103), so I am wondering whether additional forward ballast would successfully reduce the magnitude or incidence in the PW-5.

Are there any light PW-5 pilots who have resorted to additional ballast or some change to their flight habits to reduce uncommanded tail-up pitching? And if so, how effective has that change been?

Cheers,
Chris

On Tuesday, September 5, 2017 at 7:38:43 PM UTC-4, wrote:
Am considering buying a PW-5 as my first single-seater for a variety of reasons, but the one aspect I don't like is that in rough air the tail is easily pitched up in flight from unexpected gusts once I'm off tow. This one's been weighed & balanced recently and its CG is perfectly centered within its designed range.

I'm on the light side for a glider pilot, so in two-seaters I often add extra ballast when my second seat is empty. However, I see these tail-high excursions even with extra ballast in one of the Grob 103s I frequently fly solo in (but not the other Grob 103), so I am wondering whether additional forward ballast would successfully reduce the magnitude or incidence in the PW-5.

Are there any light PW-5 pilots who have resorted to additional ballast or some change to their flight habits to reduce uncommanded tail-up pitching? And if so, how effective has that change been?

Cheers,
Chris

A properly trimmed glider will pitch down to some degree when it encounters a vertical gust from below. It is seeking it's natural trimmed condition. Moving the CG forward will increase this tendency to some degree.
I don't recall any glider I have flown reacting to a horizontal gust by pitching down.
You may want to try flying with your forearm resing on your leg to avoid unintentional control inputs.
FWIW
UH

On Tuesday, September 5, 2017 at 8:23:23 PM UTC-4, wrote:
I don't recall any glider I have flown reacting to a horizontal gust
by pitching down.

IIRC Genesis does this a tiny bit - initially disconcerting but of
no consequence as it stabilizes promptly (it's a nice flying bird).
JJ ??

On Tuesday, September 5, 2017 at 6:04:49 PM UTC-7, Dave Nadler wrote:
On Tuesday, September 5, 2017 at 8:23:23 PM UTC-4, wrote:
I don't recall any glider I have flown reacting to a horizontal gust
by pitching down.

IIRC Genesis does this a tiny bit - initially disconcerting but of
no consequence as it stabilizes promptly (it's a nice flying bird).
JJ ??

IIRC vertical gusts activate the short period (AOA) mode and pitch the aircraft down while horizontal gusts activate the phugoid (airspeed) mode and pitch up (if the gust is on the nose). These are kind of fundamental aspects aircraft stability. Anything else might lead one to check the c.g. People sometimes confuse the type of gust they are experiencing.

Andy
9B

Tail up or (nose down) is a normal condition that usually occurs when entering a thermal. It can be a bit more pronounced in a short coupled bird, like the Super Albatross, Genesis-2 and I guess the PW-5. Relax, pull back a bit and roll into the light wing..............you just entered a thermal! Aft CG is best for performance.
😀 JJ

On Tuesday, September 5, 2017 at 9:24:25 PM UTC-4, Andy Blackburn wrote:
On Tuesday, September 5, 2017 at 6:04:49 PM UTC-7, Dave Nadler wrote:
On Tuesday, September 5, 2017 at 8:23:23 PM UTC-4, wrote:
I don't recall any glider I have flown reacting to a horizontal gust
by pitching down.

IIRC Genesis does this a tiny bit - initially disconcerting but of
no consequence as it stabilizes promptly (it's a nice flying bird).
JJ ??

IIRC vertical gusts activate the short period (AOA) mode and pitch the
aircraft down while horizontal gusts activate the phugoid (airspeed) mode
and pitch up (if the gust is on the nose). These are kind of fundamental
aspects aircraft stability. Anything else might lead one to check the
c.g. People sometimes confuse the type of gust they are experiencing.

Andy
9B

Absolutely, I was thinking of vertical gust response,
no idea why the OP mentioned horizontal gust response as that is
generally not an issue...

On 9/5/2017 7:24 PM, Andy Blackburn wrote:
On Tuesday, September 5, 2017 at 6:04:49 PM UTC-7, Dave Nadler wrote:
On Tuesday, September 5, 2017 at 8:23:23 PM UTC-4, wrote:
I don't recall any glider I have flown reacting to a horizontal gust
by pitching down.

IIRC Genesis does this a tiny bit - initially disconcerting but of
no consequence as it stabilizes promptly (it's a nice flying bird).
JJ ??

IIRC vertical gusts activate the short period (AOA) mode and pitch the aircraft down while horizontal gusts activate the phugoid (airspeed) mode and pitch up (if the gust is on the nose). These are kind of fundamental aspects aircraft stability. Anything else might lead one to check the c.g. People sometimes confuse the type of gust they are experiencing.

Years ago I owned a V-tailed HP-14 which enthusiastically pointed its tail to
the sky when in the presence of thermals. First time it did so it distinctly
alarmed/disconcerted me; second time it triggered my "I wonder?" brain cell;
soon thereafter I accepted it as normal-to-the-ship, useful thermal-detection
behavior of no otherwise remarkable note beyond "all the requisite/normal
stick movements" required by uncommanded ship excursions.

YMMV,
Bob W.

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I wonder why my V-tailed HP-14 did not behave like that. (I had the CG far aft within the range.) Or why the original poster noticed it in one G103 and not in another G103.

I didn't notice anything unusual on my one PW-5 flight in Invermere years ago - I found it an all around nice handling ship. The relatively light wingloading made for an exciting ride in the strong thermals there but the 1-26's got bounced around even more. A friend of mine who owns her own PW-5 hasn't reported any tail up pitching and she's quite light. In my own ASW-15B I have noticed on entry to the powerful thermals in Invermere that it frequently felt like the tail was being grabbed and shaken - like a terrier would shake a rat. Nothing alarming about it though. In the milder thermals, ridge lift and wave at my home field I've never noticed it.

On Wednesday, September 6, 2017 at 9:46:16 AM UTC-4, Dave Nadler wrote:
On Tuesday, September 5, 2017 at 9:24:25 PM UTC-4, Andy Blackburn wrote:
On Tuesday, September 5, 2017 at 6:04:49 PM UTC-7, Dave Nadler wrote:
On Tuesday, September 5, 2017 at 8:23:23 PM UTC-4, wrote:
I don't recall any glider I have flown reacting to a horizontal gust
by pitching down.

IIRC Genesis does this a tiny bit - initially disconcerting but of
no consequence as it stabilizes promptly (it's a nice flying bird).
JJ ??

IIRC vertical gusts activate the short period (AOA) mode and pitch the
aircraft down while horizontal gusts activate the phugoid (airspeed) mode
and pitch up (if the gust is on the nose). These are kind of fundamental
aspects aircraft stability. Anything else might lead one to check the
c.g. People sometimes confuse the type of gust they are experiencing.

Andy
9B

Absolutely, I was thinking of vertical gust response,
no idea why the OP mentioned horizontal gust response as that is
generally not an issue...

Possibly because the original poster was not clear about what kind of gust he was talking about. Both Andy and I chosed to address both possibilities.
UH