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#1
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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 |
#2
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PW-5 longitudinal pitch oscillation
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 |
#3
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PW-5 longitudinal pitch oscillation
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 ?? |
#4
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PW-5 longitudinal pitch oscillation
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 |
#5
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PW-5 longitudinal pitch oscillation
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 |
#6
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PW-5 longitudinal pitch oscillation
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... |
#7
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PW-5 longitudinal pitch oscillation
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. --- This email has been checked for viruses by AVG. http://www.avg.com |
#8
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PW-5 longitudinal pitch oscillation
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.
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#9
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PW-5 longitudinal pitch oscillation
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.
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#10
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PW-5 longitudinal pitch oscillation
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 |
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