Now I would guess that most of you have seen the recent gender reveal video of the Pawnee making a pass and pulling up when the wing folded and a fatal crash was the end result. As the Pawnee revealed the gender with a load of colored water half of the crown cheered and half of the crowd was screaming, OH S***.
Next time you annual your Pawnee make sure all the strut assembly is in order. OBTP

On Tuesday, September 5, 2023 at 6:02:02 PM UTC-4, youngbl...@gmail..com wrote:
> Now I would guess that most of you have seen the recent gender reveal video of the Pawnee making a pass and pulling up when the wing folded and a fatal crash was the end result. As the Pawnee revealed the gender with a load of colored water half of the crown cheered and half of the crowd was screaming, OH S***.
> Next time you annual your Pawnee make sure all the strut assembly is in order. OBTP

Yep. I had a failure at the end of the strut. Fortunately it docked on the wing fitting and the airplane was marginally controllable. Pure luck that I'm alive.
Clearly there was an over stress here but I would not rule out strut failure leading to folding the wing.
UH

On Wednesday, September 6, 2023 at 8:18:35 AM UTC-4, Hank Nixon wrote:
> On Tuesday, September 5, 2023 at 6:02:02 PM UTC-4, youngbl...@gmail.com wrote:
> > Now I would guess that most of you have seen the recent gender reveal video of the Pawnee making a pass and pulling up when the wing folded and a fatal crash was the end result. As the Pawnee revealed the gender with a load of colored water half of the crown cheered and half of the crowd was screaming, OH S***.
> > Next time you annual your Pawnee make sure all the strut assembly is in order. OBTP
> Yep. I had a failure at the end of the strut. Fortunately it docked on the wing fitting and the airplane was marginally controllable. Pure luck that I'm alive.
> Clearly there was an over stress here but I would not rule out strut failure leading to folding the wing.
> UH

Don't know if this bird was ever a tow plane or if it was still being used in ag flying but either way the Pawnee gets lot of abuse, ESPECIALLY the tow plane Pawnee. The stress from poor student flying, boxing the wake poorly, slack rope recovery and just the daily wear and tear from towing has to take a toll on the airframe in general. There is much that cannot be seen and inspected in a walk around, one must depend on the A&P who does the required inspections and not everyone of them is conscientious and meticulous.

Walt Connelly
Former Tow Plane Pilot

https://www.youtube.com/watch?v=wp19ch40t0c&t=6s

Juan Browne presents a good tutorial here.

Nick
T

On Wednesday, September 6, 2023 at 6:00:29 AM UTC-7, waltco...@aol.com wrote:
> On Wednesday, September 6, 2023 at 8:18:35 AM UTC-4, Hank Nixon wrote:
> > On Tuesday, September 5, 2023 at 6:02:02 PM UTC-4, youngbl...@gmail.com wrote:
> > > Now I would guess that most of you have seen the recent gender reveal video of the Pawnee making a pass and pulling up when the wing folded and a fatal crash was the end result. As the Pawnee revealed the gender with a load of colored water half of the crown cheered and half of the crowd was screaming, OH S***.
> > > Next time you annual your Pawnee make sure all the strut assembly is in order. OBTP
> > Yep. I had a failure at the end of the strut. Fortunately it docked on the wing fitting and the airplane was marginally controllable. Pure luck that I'm alive.
> > Clearly there was an over stress here but I would not rule out strut failure leading to folding the wing.
> > UH
> Don't know if this bird was ever a tow plane or if it was still being used in ag flying but either way the Pawnee gets lot of abuse, ESPECIALLY the tow plane Pawnee. The stress from poor student flying, boxing the wake poorly, slack rope recovery and just the daily wear and tear from towing has to take a toll on the airframe in general. There is much that cannot be seen and inspected in a walk around, one must depend on the A&P who does the required inspections and not everyone of them is conscientious and meticulous.
>
> Walt Connelly
> Former Tow Plane Pilot
A Pawnee used for towing is operating well below it's maximum weight. Shouldn't that make life relatively easy for it?

On Wednesday, September 6, 2023 at 6:21:31 AM UTC-7, Nicholas Kennedy wrote:
> https://www.youtube.com/watch?v=wp19ch40t0c&t=6s
>
> Juan Browne presents a good tutorial here.
>
> Nick
> T
This video has important lessons and brings important questions:
According to the video and other articles on the subject, maneuvering/rough air speed is calculated at max gross weight and is reduced with weight. I checked my ASG 29 manual and nowhere is it mentioned that the VA speed is at max gross weight and should be reduced below that. Modern gliders which can carry ballast are flown at about 30% below max gross when empty, so based on the information I read maneuvering speed is reduced by about 15% which brings the ASG29 VA speed from 113 knots down to 96 knots! If this is true I’ve been exceeding VA in rough air more often than I was aware of.
Another lesson relevant to gliders is NOT to pull G when releasing load, which is exactly what we do when releasing ballast during low pass, although the G force is probably only 2-3G and the dump rate is relatively low, so probably not a significant factor.
The biggest question is what is the correct VA for our gliders and does it indeed change with weight, and if so, how come this is not mentioned in the manual and I don’t recall ever hearing about this before.

Ramy

On Wednesday, September 6, 2023 at 3:45:03 PM UTC-4, Ramy wrote:
> On Wednesday, September 6, 2023 at 6:21:31 AM UTC-7, Nicholas Kennedy wrote:
> > https://www.youtube.com/watch?v=wp19ch40t0c&t=6s
> >
> > Juan Browne presents a good tutorial here.
> >
> > Nick
> > T
> This video has important lessons and brings important questions:
> According to the video and other articles on the subject, maneuvering/rough air speed is calculated at max gross weight and is reduced with weight. I checked my ASG 29 manual and nowhere is it mentioned that the VA speed is at max gross weight and should be reduced below that. Modern gliders which can carry ballast are flown at about 30% below max gross when empty, so based on the information I read maneuvering speed is reduced by about 15% which brings the ASG29 VA speed from 113 knots down to 96 knots! If this is true I’ve been exceeding VA in rough air more often than I was aware of.
> Another lesson relevant to gliders is NOT to pull G when releasing load, which is exactly what we do when releasing ballast during low pass, although the G force is probably only 2-3G and the dump rate is relatively low, so probably not a significant factor.
> The biggest question is what is the correct VA for our gliders and does it indeed change with weight, and if so, how come this is not mentioned in the manual and I don’t recall ever hearing about this before.
>
> Ramy
One of the things that comes to mind in this accident is the fact that the CG was well forward prior to the dump being opened. Once the dump was opened the cg went from forward to more rear and the increased angle of attack increased the g load. If you look at that video it was a pretty hard pull that the pilot did with an increased angle of attack.
On the other hand it was in Mexico, how was this Pawnee maintained??? Eric asked the question about the Pawnee being used for tow was somewhat subjected to a life of less stress or abuse. Well, not exactly, Walt made a great statement about the abuse a Pawnee takes during tow, these beautiful birds take a beating from the teaching and extreme application during towing.
I have done things in a Pawnee that would make most of you shake your heads and say, NUTS! OBTP

On Wednesday, September 6, 2023 at 4:48:50 PM UTC-4, youngbl...@gmail.com wrote:
> On Wednesday, September 6, 2023 at 3:45:03 PM UTC-4, Ramy wrote:
> > On Wednesday, September 6, 2023 at 6:21:31 AM UTC-7, Nicholas Kennedy wrote:
> > > https://www.youtube.com/watch?v=wp19ch40t0c&t=6s
> > >
> > > Juan Browne presents a good tutorial here.
> > >
> > > Nick
> > > T
> > This video has important lessons and brings important questions:
> > According to the video and other articles on the subject, maneuvering/rough air speed is calculated at max gross weight and is reduced with weight.. I checked my ASG 29 manual and nowhere is it mentioned that the VA speed is at max gross weight and should be reduced below that. Modern gliders which can carry ballast are flown at about 30% below max gross when empty, so based on the information I read maneuvering speed is reduced by about 15% which brings the ASG29 VA speed from 113 knots down to 96 knots! If this is true I’ve been exceeding VA in rough air more often than I was aware of.
> > Another lesson relevant to gliders is NOT to pull G when releasing load, which is exactly what we do when releasing ballast during low pass, although the G force is probably only 2-3G and the dump rate is relatively low, so probably not a significant factor.
> > The biggest question is what is the correct VA for our gliders and does it indeed change with weight, and if so, how come this is not mentioned in the manual and I don’t recall ever hearing about this before.
> >
> > Ramy
> One of the things that comes to mind in this accident is the fact that the CG was well forward prior to the dump being opened. Once the dump was opened the cg went from forward to more rear and the increased angle of attack increased the g load. If you look at that video it was a pretty hard pull that the pilot did with an increased angle of attack.
> On the other hand it was in Mexico, how was this Pawnee maintained??? Eric asked the question about the Pawnee being used for tow was somewhat subjected to a life of less stress or abuse. Well, not exactly, Walt made a great statement about the abuse a Pawnee takes during tow, these beautiful birds take a beating from the teaching and extreme application during towing.
> I have done things in a Pawnee that would make most of you shake your heads and say, NUTS! OBTP

Juan. Browne does a great job as usual. I am still surprised that the wing would depart so suddenly under such circumstances but it appears that the pull up was substantial. There is another case of the wings folding on an ag plane south of the border under similar circumstances. OBTP makes a good point about being in Mexico, I'm betting their investigation will not be as comprehensive as it would be by the NTSB and FAA.

Walt Connelly

On Thursday, September 7, 2023 at 9:39:11 AM UTC-4, waltco...@aol.com wrote:
> On Wednesday, September 6, 2023 at 4:48:50 PM UTC-4, youngbl...@gmail.com wrote:
> > On Wednesday, September 6, 2023 at 3:45:03 PM UTC-4, Ramy wrote:
> > > On Wednesday, September 6, 2023 at 6:21:31 AM UTC-7, Nicholas Kennedy wrote:
> > > > https://www.youtube.com/watch?v=wp19ch40t0c&t=6s
> > > >
> > > > Juan Browne presents a good tutorial here.
> > > >
> > > > Nick
> > > > T
> > > This video has important lessons and brings important questions:
> > > According to the video and other articles on the subject, maneuvering/rough air speed is calculated at max gross weight and is reduced with weight. I checked my ASG 29 manual and nowhere is it mentioned that the VA speed is at max gross weight and should be reduced below that. Modern gliders which can carry ballast are flown at about 30% below max gross when empty, so based on the information I read maneuvering speed is reduced by about 15% which brings the ASG29 VA speed from 113 knots down to 96 knots! If this is true I’ve been exceeding VA in rough air more often than I was aware of.
> > > Another lesson relevant to gliders is NOT to pull G when releasing load, which is exactly what we do when releasing ballast during low pass, although the G force is probably only 2-3G and the dump rate is relatively low, so probably not a significant factor.
> > > The biggest question is what is the correct VA for our gliders and does it indeed change with weight, and if so, how come this is not mentioned in the manual and I don’t recall ever hearing about this before.
> > >
> > > Ramy
> > One of the things that comes to mind in this accident is the fact that the CG was well forward prior to the dump being opened. Once the dump was opened the cg went from forward to more rear and the increased angle of attack increased the g load. If you look at that video it was a pretty hard pull that the pilot did with an increased angle of attack.
> > On the other hand it was in Mexico, how was this Pawnee maintained??? Eric asked the question about the Pawnee being used for tow was somewhat subjected to a life of less stress or abuse. Well, not exactly, Walt made a great statement about the abuse a Pawnee takes during tow, these beautiful birds take a beating from the teaching and extreme application during towing.
> > I have done things in a Pawnee that would make most of you shake your heads and say, NUTS! OBTP
> Juan. Browne does a great job as usual. I am still surprised that the wing would depart so suddenly under such circumstances but it appears that the pull up was substantial. There is another case of the wings folding on an ag plane south of the border under similar circumstances. OBTP makes a good point about being in Mexico, I'm betting their investigation will not be as comprehensive as it would be by the NTSB and FAA.
>
> Walt Connelly
For years the NTSB budget has not allowed them to perform at the same level as they did in decades past. Had this happened in the US I doubt they'd even have showed up.

On Wednesday, September 6, 2023 at 3:45:03 PM UTC-4, Ramy wrote:
> On Wednesday, September 6, 2023 at 6:21:31 AM UTC-7, Nicholas Kennedy wrote:
> > https://www.youtube.com/watch?v=wp19ch40t0c&t=6s
> >
> > Juan Browne presents a good tutorial here.
> >
> > Nick
> > T
> This video has important lessons and brings important questions:
> According to the video and other articles on the subject, maneuvering/rough air speed is calculated at max gross weight and is reduced with weight. I checked my ASG 29 manual and nowhere is it mentioned that the VA speed is at max gross weight and should be reduced below that. Modern gliders which can carry ballast are flown at about 30% below max gross when empty, so based on the information I read maneuvering speed is reduced by about 15% which brings the ASG29 VA speed from 113 knots down to 96 knots! If this is true I’ve been exceeding VA in rough air more often than I was aware of.
> Another lesson relevant to gliders is NOT to pull G when releasing load, which is exactly what we do when releasing ballast during low pass, although the G force is probably only 2-3G and the dump rate is relatively low, so probably not a significant factor.
> The biggest question is what is the correct VA for our gliders and does it indeed change with weight, and if so, how come this is not mentioned in the manual and I don’t recall ever hearing about this before.
>
> Ramy

I think Juan got a few things wrong. I don't believe VA should logically decrease with weight (even though some aircraft manuals may say so). What the structure cares about is the absolute load on the structure not the G-load. For example if the weight (of the non-lifting parts) of the aircraft is 2000 lbs and there is a 6 G load, the structure must support 12000 lbf (6 x 2000). If the aircraft weighed 1000 lbs you would need to pull 12 Gs to get the same 12000 lbf (12 x 1000). At VA, at the critical-angle-of-attack the wings will generate a force X and the structure is designed to carry that load. The structure doesn't care if it you generate the load by adding mass or by increasing the G-load as long as its below X.

Also he points to the wing attachment fittings as the probable failure but if you look at the video, at the first point you can detect a failure, the root of the wing seems to be connected to the fuselage correctly but you can see a fold going from the front spare attachment fitting to the trailing edge of the wing. To me it looks like the rear spar failed between the fuselage attachment fitting and the rear spar/strut attachment fitting.

tim

I wasn't sold on Juan's logic either.

I found this video and I think it makes more sense. It starts off down the path of Va reducing with aircraft weight, but when you run the math (which the presenter does point out later in the video) the loads on the wings are the same in the 2 cases. The loads on the other parts of the fuse see higher loads. Since the Pawnee appears to fail at the wing and not with the seat, engine mounts, floorboard, etc. I think we're more likely to find that the reduction in weight due to the water dump is not a significant contributing factor, but flying an old aircraft well above Va and the pulling up, broke one or more components that may have been weakened due to age, etc..

https://www.aopa.org/news-and-media/all-news/2020/may/flight-training-magazine/ol-maneuvering-speed

On Thursday, September 7, 2023 at 9:19:06 AM UTC-8, Mark Zivley wrote:
> I wasn't sold on Juan's logic either.
>
> I found this video and I think it makes more sense. It starts off down the path of Va reducing with aircraft weight, but when you run the math (which the presenter does point out later in the video) the loads on the wings are the same in the 2 cases. The loads on the other parts of the fuse see higher loads. Since the Pawnee appears to fail at the wing and not with the seat, engine mounts, floorboard, etc. I think we're more likely to find that the reduction in weight due to the water dump is not a significant contributing factor, but flying an old aircraft well above Va and the pulling up, broke one or more components that may have been weakened due to age, etc.
>
> https://www.aopa.org/news-and-media/all-news/2020/may/flight-training-magazine/ol-maneuvering-speed
Va does decrease with weight. Can any of you Smart Keyboard warriors tell me why?

Charlie

There are few questions:
1- Does Va Decrease with speed?
2- if so, why on earth is it provided for max gross instead of minimum (or reference) weight, to err on the safe side?
3- why isn’t it mentioned in the manuals, at least not my glider manual?
4- why isn’t it common knowledge like VNE decrease with altitude? You would think it should be almost equally important to know, yet the fact that we debating it confirms it is not a common knowledge.

Ramy

On Thursday, September 7, 2023 at 10:22:41 AM UTC-7, Charles Longley wrote:
> On Thursday, September 7, 2023 at 9:19:06 AM UTC-8, Mark Zivley wrote:
> > I wasn't sold on Juan's logic either.
> >
> > I found this video and I think it makes more sense. It starts off down the path of Va reducing with aircraft weight, but when you run the math (which the presenter does point out later in the video) the loads on the wings are the same in the 2 cases. The loads on the other parts of the fuse see higher loads. Since the Pawnee appears to fail at the wing and not with the seat, engine mounts, floorboard, etc. I think we're more likely to find that the reduction in weight due to the water dump is not a significant contributing factor, but flying an old aircraft well above Va and the pulling up, broke one or more components that may have been weakened due to age, etc.
> >
> > https://www.aopa.org/news-and-media/all-news/2020/may/flight-training-magazine/ol-maneuvering-speed
> Va does decrease with weight. Can any of you Smart Keyboard warriors tell me why?
>
> Charlie

From the video that I linked above, here is a short explanation

Say the wing to fuse junction is designed to sustain 10,000 lbs at 4 Gs (rounded up from 3.8) for a 2,500 lb aircraft at max gross of 2,500.

If the plane now weighs 2,000 lbs then the wing can still pull 10,000 lbs, which is now equal to 5 G.

It's not the wing/fuse joint that is the issue, it's things like the motor mount which are designed to support the engine or pilot at 4 G... If that motor mount sees 5G then the failure occurs at the motor mount. Same thing for the bracket that supports the seat. It's good at 4G (at maximum seat load), but at 5G, it's now over stressed.

If the aircraft weight decreased to 1,000 lbs, the wing could support 10G and not fail, but then the motor mount is way over stressed, same for the seat bracket.

So, if the capability to create higher G's is possible with a lower weight, the way to protect against over stressing (with an abrupt aft stick input) is to reduce airspeed.

> Va does decrease with weight. Can any of you Smart Keyboard warriors tell me why?
>
> Charlie

On Thursday, September 7, 2023 at 3:08:12 PM UTC-4, Mark Zivley wrote:
> From the video that I linked above, here is a short explanation
>
> Say the wing to fuse junction is designed to sustain 10,000 lbs at 4 Gs (rounded up from 3.8) for a 2,500 lb aircraft at max gross of 2,500.
>
> If the plane now weighs 2,000 lbs then the wing can still pull 10,000 lbs, which is now equal to 5 G.
>
> It's not the wing/fuse joint that is the issue, it's things like the motor mount which are designed to support the engine or pilot at 4 G... If that motor mount sees 5G then the failure occurs at the motor mount. Same thing for the bracket that supports the seat. It's good at 4G (at maximum seat load), but at 5G, it's now over stressed.
>
> If the aircraft weight decreased to 1,000 lbs, the wing could support 10G and not fail, but then the motor mount is way over stressed, same for the seat bracket.
>
> So, if the capability to create higher G's is possible with a lower weight, the way to protect against over stressing (with an abrupt aft stick input) is to reduce airspeed.
> > Va does decrease with weight. Can any of you Smart Keyboard warriors tell me why?
> >
> > Charlie

Another video
https://twitter.com/aviationbrk/status/1698255432630796349
It looks to me like the left wing was twisting leading edge up just before the catastrophic failure. This is consistent with a failure of the front strut either at the outboard fitting, or buckling due failure of the jury strut.
G loads are high when it looks like you can see deflections.
Anybody still using original struts, even if they test "good" is being foolish in my opinion. Our struts looked fine with no corrosion and we had a failure.
FWIW
UH

On Thursday, September 7, 2023 at 3:31:09 PM UTC-4, Hank Nixon wrote:
> On Thursday, September 7, 2023 at 3:08:12 PM UTC-4, Mark Zivley wrote:
> > From the video that I linked above, here is a short explanation
> >
> > Say the wing to fuse junction is designed to sustain 10,000 lbs at 4 Gs (rounded up from 3.8) for a 2,500 lb aircraft at max gross of 2,500.
> >
> > If the plane now weighs 2,000 lbs then the wing can still pull 10,000 lbs, which is now equal to 5 G.
> >
> > It's not the wing/fuse joint that is the issue, it's things like the motor mount which are designed to support the engine or pilot at 4 G... If that motor mount sees 5G then the failure occurs at the motor mount. Same thing for the bracket that supports the seat. It's good at 4G (at maximum seat load), but at 5G, it's now over stressed.
> >
> > If the aircraft weight decreased to 1,000 lbs, the wing could support 10G and not fail, but then the motor mount is way over stressed, same for the seat bracket.
> >
> > So, if the capability to create higher G's is possible with a lower weight, the way to protect against over stressing (with an abrupt aft stick input) is to reduce airspeed.
> > > Va does decrease with weight. Can any of you Smart Keyboard warriors tell me why?
> > >
> > > Charlie
> Another video
> https://twitter.com/aviationbrk/status/1698255432630796349
> It looks to me like the left wing was twisting leading edge up just before the catastrophic failure. This is consistent with a failure of the front strut either at the outboard fitting, or buckling due failure of the jury strut.
> G loads are high when it looks like you can see deflections.
> Anybody still using original struts, even if they test "good" is being foolish in my opinion. Our struts looked fine with no corrosion and we had a failure.
> FWIW
> UH
There is no doubt that the left wing strut failed, I think that the failure was at the single attach point at the fuselage. As far as the original struts I have had original struts on all my Pawnee's, never had any doubt about their possibility of failure. I go well beyond the requirements for testing, I loop, roll, hammerhead and spin my Pawnee, OBTP