Pac 750 stalls on jump run

[NWFlyer 2]

As front float on both of the aforementioned stalls this weekend at the boogie, I can say pretty unequivocally that's not the attitude I like to see a plane in. In the first case, pilot inexperience was said to be a contributing factor (though certainly *not* the only factor), and that stall was significantly more dramatic and sudden than the second. In the second the pilot (who, as you know is one of the most experienced jump pilots on this aircraft) recognized, corrected, and finally did what he needed to do to right the plane (which involved "shaking" us off to the left side of the aircraft).

Quote

As previously stated, folks need to stay forward, the pilot needs to be informed of the larger group in the door, and the large group in the door needs to be efficient on climb out & exit.

We reviewed the video on the second jump and counted from video climb-out to exit and realized that we were taking too long in the door, which certainly didn't help the situation. The timing was such that we were probably on "set" at the exact point that the pilot "shook" us off. A few seconds faster on the climb-out/set-up and the problem could have been avoided.

"There is only one basic human right, the right to do as you damn well please. And with it comes the only basic human duty, the duty to take the consequences." -P.J. O'Rourke

[davelepka 4]

Quote

As previously stated, folks need to stay forward, the pilot needs to be informed of the larger group in the door, and the large group in the door needs to be efficient on climb out & exit.

--------------------------------------------------------------------------------


We reviewed the video on the second jump and counted from video climb-out to exit and realized that we were taking too long in the door, which certainly didn't help the situation. The timing was such that we were probably on "set" at the exact point that the pilot "shook" us off. A few seconds faster on the climb-out/set-up and the problem could have been avoided.

This is not the correct way to look at it. You should never put yourself in a situatiuon where you have to get set and off the aircraft in a certain amount of time to avoid a stall. If that was the case, than the pilot did not properly configure the AC for that jumprun, or the climbout you had planned exceeded the capabilities of the AC.

The airspeed on jumprun should be such that with all floaters outside the AC the pilot can maintain control of the AC for an 'unlimited' amount of time. If the load outside of the AC causes the airspeed, and therefore control, of the AC to degrade, then the airspeed of the jumprun needs to be raised, or the number of floaters needs to be lowered.

Time used in a climbout should be monitored for the sake of spotting alone, be it for the group climbing out or the rest of the load. Any situation where the length of the climbout will effect the pilots ability to maintain control of the AC should be avoided at all costs.

[headoverheels 291]

Quote

This is not the correct way to look at it. You should never put yourself in a situation where you have to get set and off the aircraft in a certain amount of time to avoid a stall. If that was the case, than the pilot did not properly configure the AC for that jump run, or the climb out you had planned exceeded the capabilities of the AC.

That is certainly true. However, the point NWFlyer makes regarding quick lineup/exit resulting in fewer stalls, given imperfect piloting, should also be used, to further reduce such incidents. The particular pilot and aircraft should be taken into account when planning the line up. Many jump pilots have definite ideas on how many floaters is acceptable to them, so that should be understood ahead of time.

[popsjumper 2]

Quote

...your call Pops - I don't recall any specific requirements in the SIM for PAC loading for a D license. But everyone should have their opinion.

CG concepts are learned at pre-A license. Maybe I just expect too much from D-licensed TIs and think that one would think of these things, and more advanced things, before loading up on a new aircraft.

My reality and yours are quite different.
I think we're all Bozos on this bus.
Falcon5232, SCS8170, SCSA353, POPS9398, DS239

[labrys 0]

Quote

CG concepts are learned at pre-A license. Maybe I just expect too much from D-licensed TIs and think that one would think of these things, and more advanced things, before loading up on a new aircraft.

Don't fuck up the discussion by introducing common sense, pops.....sheesh....

Owned by Remi #?

[skyjumpenfool 2]

Quote

CG concepts are learned at pre-A license. Maybe I just expect too much from D-licensed TIs and think that one would think of these things, and more advanced things, before loading up on a new aircraft.

Isn't the reason for this thread to get the word out and to educate? Indeed, as stated above, this is a relatively new jump ship to most of us. Hopefully everyone, students and experienced alike are learning something about this aircraft. I know I am.

It’s my understanding, that this particular version of the PAC was designed (or maybe more accurately, modified) specifically for skydiving. Is there an official set of guidelines concerning exits, exit timing, floaters, CG, etc??? Does the Manufacturer have any information available??

Pilots… tell us what you know!!

Birdshit & Fools Productions

"Son, only two things fall from the sky."

[piisfish 135]

Quote

Isn't the reason for this thread to get the word out and to educate? ...Hopefully everyone, students and experienced alike are learning something about this aircraft. ...It’s my understanding, that this particular version of the PAC was designed ..specifically for skydiving.

designed for skydiving ? YES
but not for large groups (I didnt say groups of large people ). My opinion is that it has been designed skydiving as it is done locally : mostly tandem factories.

I can't remember how the internal weight is distributed at www.paraclub.ch, but in the early days of flying the plane they stalled it. Shortly after they put limits of jumpers out, how many in front etc etc.

scissors beat paper, paper beat rock, rock beat wingsuit - KarlM

[rehmwa 2]

Quote

designed for skydiving ? YES

Designed for skydiving? absolutely no

Designed for the skydiving flight pattern and aircraft use? yes

not designed for large groups? I'd say I'm not thrilled with that low wing on 2 way sit or HD dives either. We have a quite different launch for HD flowers with this plane than with otters. You don't want to conk yer head.

(it's designed for the flight plan by apparently non-jumper aero engineers - high climb rate, short takeoff, quick turnaround, rapid up and down - good for the flight pattern, not so much for exits and air for the jumpers, that's the tradeoffs)

still a pretty nice plane, but for jumpers? Low wing that comes right to the front of the door.... the lower running board is nice to get foot room, but it does make a 4-way team have to adjust presentation and timing..... a low horizontal stabilizer????......etc etc etc. I see the design reasons for these things based on flight operation criteria are pretty clear, but they are specifically "not" jumper friendly. The Twin Otter is still the standard.

That said, for our DZ, the PAC is the perfect plane for the size of the business, and I'm glad we have one. I just wish we had the Otter on the weekends when it's busier - for purely selfish reasons. However, it's really nice to be able get a load off when it's not crowded too - for purely selfish reasons.

...
Driving is a one dimensional activity - a monkey can do it - being proud of your driving abilities is like being proud of being able to put on pants

[rehmwa 2]

Quote

A few seconds faster on the climb-out/set-up and the problem could have been avoided.

I absolutely LOVE this.

On our second 12 way attempt, I told the group we'll have a faster climbout, and be ready.

1 - the biggest guy on the load got out in the worst/slowest possible way (rotating out the door instead of stepping out sideways into his slot). There wasn't really enough room for him to do that. (correct exit to a tight floater slot = left side to the door, step out directly sideways. Do NOT rotate out the door counterclockwise, thus smacking your rig and hackey against the floater in front of you first, and then against the guy behind you as you try to insert yourself into your slot from the outside.....)

2 - we were long as a result

3 - one of my divers was late and complained that he wasn't ready for the count

- you really just can't win no matter what

...
Driving is a one dimensional activity - a monkey can do it - being proud of your driving abilities is like being proud of being able to put on pants

[davelepka 4]

Quote

On our second 12 way attempt, I told the group we'll have a faster climbout, and be ready.

1 - the biggest guy on the load got out in the worst/slowest possible way (rotating out the door instead of stepping out sideways into his slot). There wasn't really enough room for him to do that. (correct exit to a tight floater slot = left side to the door, step out directly sideways. Do NOT rotate out the door counterclockwise, thus smacking your rig and hackey against the floater in front of you first, and then against the guy behind you as you try to insert yourself into your slot from the outside.....)

2 - we were long as a result

3 - one of my divers was late and complained that he wasn't ready for the count

- you really just can't win no matter what

This comes back to what I said about the speed of your climbout not being relative to the aircraft stalling. The aircraft config on jumprun needs to be such that the pilot can maintain control for as long as the jumpers need to be out there.

Even the best laid plans (as above) can go wrong, and if the AC airspeed is degrading the whole time, you are on your way to a stall. Not a road I want to be on.

Just to touch on another point made, even if the pilot has the correct config for the exit/climbout you're doing, that doesn't mean you should take your time.

Extra time spent outside the plane is additional time you're at risk for a premature deployment and a hang up on that low tail. It's unofrtunate for the tail, but it's directly downwind of every jumper who climbs out of the door, and more people spending more time outside is just stacking the deck against the tail. Let's also remember that these people are moving around, trying to position themselves, and maybe not thinking about their pins and what they might be coming into contact with.

[rehmwa 2]

Quote

Just to touch on another point made, even if the pilot has the correct config for the exit/climbout you're doing, that doesn't mean you should take your time.

ABSOLTIVELY - and my point is, you can coach 'em, and coach 'em, and coach 'em, but when it comes to climbout, those old habits are hard to break, and someone will always do it sloppy unless you really have a well trained team. And not just big ways, I've been on 3way Freefly where one person is a bit nervous and they'll completely block the door and stick the 3rd person inside. Little stuff adds up.

summary - at boogies especially, you gotta plan for this and have some margin built in

...
Driving is a one dimensional activity - a monkey can do it - being proud of your driving abilities is like being proud of being able to put on pants

[diverdriver 5]

Quote

(there were 3 pretty big guys on the 2nd attempt and no problem that time with the higher airspeed)
____

I was on the 2nd, not there for the first, last inside.
The only problem on the 2nd attempt was that the pilot was compensating so much that that getting to the door was like climbing a stepladder (when the chunk left, the tail of the plane came up about 2 1/2 feet and stayed there.
Not that I'd rather be inside during a stall.......

You might ask if this pilot is trimming nose down on jumprun. I recommend in the planes I know (182, 206, Twin Otter) not to trim during jumprun but rather just use some muscle and push forward. This allows for a smoother unload during exit and doesn't cause divers to get pinned to the floor as the nose down trim takes over and the pilot must use lots of muscle to pull until re-trimming.

Chris Schindler
www.diverdriver.com
ATP/D-19012
FB #4125

[diverdriver 5]

Quote

The airspeed on jumprun should be such that with all floaters outside the AC the pilot can maintain control of the AC for an 'unlimited' amount of time. If the load outside of the AC causes the airspeed, and therefore control, of the AC to degrade, then the airspeed of the jumprun needs to be raised, or the number of floaters needs to be lowered.

Time used in a climbout should be monitored for the sake of spotting alone, be it for the group climbing out or the rest of the load. Any situation where the length of the climbout will effect the pilots ability to maintain control of the AC should be avoided at all costs.

Agree 100%. The setup should be sustainable indefinitely.

Chris Schindler
www.diverdriver.com
ATP/D-19012
FB #4125

[Feeblemind 1]

Here is a video of two different stalls in a Pac750XL.

http://www.youtube.com/watch?v=4jfAaEWxJ2I

I do not know what the chunk off the plane was as I am grounded due to injury, maybe someone that was on the load can provide that information.

Fire Safety Tip: Don't fry bacon while naked

[NWFlyer 2]

Quote

Here is a video of two different stalls in a Pac750XL.

http://www.youtube.com/watch?v=4jfAaEWxJ2I

I do not know what the chunk off the plane was as I am grounded due to injury, maybe someone that was on the load can provide that information.

Thanks for posting those, Phil. They are the two stalls on Thursday that I mentioned up-thread. While we were waiting for the last aircraft (Otter) for the bigway to show up, we practiced in smaller groups. These jumps were practice for the 6 in the base + the 6 zippers. Single plane practice, no formation.

Including video, we had five outside. The chunk being launched was a four-way base chunk with two outside and two inside, plus front float (me) and rear float, both of whom were zippers. I believe that the other six folks were not lined up at the door and instead stayed towards the front of the plane, but there might have been one more diver in the back.

On the first jump there was a tail strike by one of the jumpers who was in the inside group. Fortunately the jumper sustained only minor injuries - bruises on his left side (thigh and upper arm), and he chose to deploy immediately after clearing the tail to allow himself time to assess the situation for both his gear and his body. He was able to land safely under his main. There was what was described as superficial damage to the plane.

"There is only one basic human right, the right to do as you damn well please. And with it comes the only basic human duty, the duty to take the consequences." -P.J. O'Rourke

[diverdriver 5]

Quote

Here is a video of two different stalls in a Pac750XL.

http://www.youtube.com/watch?v=4jfAaEWxJ2I

I do not know what the chunk off the plane was as I am grounded due to injury, maybe someone that was on the load can provide that information.

One thing you need to really consider doing is getting rid of the position directly in front of the camera man. They are leaning WAY off the body of the aicraft causing more "bad air" for the horizontal stablizer. If they can be on the outside of the plane and have their body in close I think that should be moved around somehow when organizing. The second stall video seems to be a more pronounced stall in that it also rolled more left during the break. In the video I see people leaning out further than on the first video. I would say that people should only climb out and keep close to the frame until launch. That's my opinion after a short run through watching.

Chris Schindler
www.diverdriver.com
ATP/D-19012
FB #4125

[happythoughts 0]

Quote

Quote

The airspeed on jumprun should be such that with all floaters outside the AC the pilot can maintain control of the AC for an 'unlimited' amount of time. If the load outside of the AC causes the airspeed, and therefore control, of the AC to degrade, then the airspeed of the jumprun needs to be raised, or the number of floaters needs to be lowered.

Time used in a climbout should be monitored for the sake of spotting alone, be it for the group climbing out or the rest of the load. Any situation where the length of the climbout will effect the pilots ability to maintain control of the AC should be avoided at all costs.

Agree 100%. The setup should be sustainable indefinitely.

When doing formations, the climb out time is longer than usual
because of giving everyone a few extra moments.
(Yes, I realize that you know this. Just mentioning it for the
consideration of others.)
As front-front, I have spent some time out there.
Anyway, the expectation that the climbout/exit will be quick is
not necessarily valid.

Also, we put everybody and his brother outside, even the beef.
The back of the plane is loaded. Most of the time it is 6-7 floaters, two rows of 3 divers, and a pair behind them.
The rest around the corner.

If a pilot expects that to happen, I hope that he can handle
that task.

I have been on Otters that stalled. That issue was resolved
by a conversation with the lead pilot.

Unloading an entire PAC is a pain because everyone is bent
over and the line extends back to that hump behind the pilot.
(As a non-pilot) I think they need to come up with a good
consensus on how to handle the problem of a lot of floaters.
Otters do it well. No excuses, it's the job.

[wildfan75 1]

Quote

I just wish we had the Otter on the weekends when it's busier

Especially on NPSL weekends!!!! 12-13 hours for a meet is waaaaaay too long!

[skyjumpenfool 2]

Quote

Especially on NPSL weekends!!!! 12-13 hours for a meet is waaaaaay too long!

Fire up a Cessna!

see you on Friday!.....

Birdshit & Fools Productions

"Son, only two things fall from the sky."

[wildfan75 1]

Quote

Quote

Especially on NPSL weekends!!!! 12-13 hours for a meet is waaaaaay too long!

Fire up a Cessna!

see you on Friday!.....

Gang Green would love to do the meet out of the Cessna. It would level the playing field a little bit for us Cessna brats.

[davelepka 4]

Quote

Here is a video of two different stalls in a Pac750XL

Two different stalls, yes, but the two exits were the exact same thing, the only difference being the second one was about 20 seconds from the start of the climbout to the stall, with the first being 27 seconds to the stall.

Both seemed to be fairly long climbouts, but after seeing the results of the first, why would you duplicate the exact same scenario for the second?

I think I read that a jumper was injured exiting during the first stall, and you were lucky that was the extent of the injuries. If either one of those had progressed into a spin, anyone left inside the plane would be at risk for injury as they would be unsecured 'cargo', and subject to being tossed around the cabin.

Even one revolution would be enough to throw everyone into a wall with a good deal of force.

I don't think it's a tough concept to understand that if you stall an aircraft with a certain exit/climbout, that you not repeat the same manuver verbatim later that day.

[NWFlyer 2]

Quote

I don't think it's a tough concept to understand that if you stall an aircraft with a certain exit/climbout, that you not repeat the same manuver verbatim later that day.

Good feedback; the decision was made to do the same jump again because the belief was that the primary contributing factor to the first stall was pilot inexperience; the second jump was done with a different pilot (and different PAC, since the PAC involved in the first jump was temporarily grounded for inspection) who has significantly more experience both in the PAC and with jumpers launching chunks out of the PAC. Obviously, lesson learned by everyone involved that there was more at play than pilot skill & experience.

"There is only one basic human right, the right to do as you damn well please. And with it comes the only basic human duty, the duty to take the consequences." -P.J. O'Rourke

[diablopilot 2]

Quote

The second stall video seems to be a more pronounced stall in that it also rolled more left during the break.

There was no second stall. The pilot of the A/C kicked left rudder, and a few degrees of bank to exit the chunk to prevent an impending stall.

----------------------------------------------
You're not as good as you think you are. Seriously.

[diverdriver 5]

Quote

Quote

The second stall video seems to be a more pronounced stall in that it also rolled more left during the break.

There was no second stall. The pilot of the A/C kicked left rudder, and a few degrees of bank to exit the chunk to prevent an impending stall.

Ah, it certainly looked like it pitched up just as much. So, has anyone discussed what I brought up about the one jumper leaning out and blocking more flow?

Chris Schindler
www.diverdriver.com
ATP/D-19012
FB #4125

[NWFlyer 2]

Quote

So, has anyone discussed what I brought up about the one jumper leaning out and blocking more flow?

I recall one of the things discussed by the organizer during the dirt dive was to have the outside folks lean out to make room for the two on the inside who were launching with the chunk - allowing them to get shoulders out and allow for a clean exit. Quite honestly, I don't think the impact on the airflow was considered at all.

"There is only one basic human right, the right to do as you damn well please. And with it comes the only basic human duty, the duty to take the consequences." -P.J. O'Rourke