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Exit rules for PAC 750?

 

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Premier wmw999  (D 6296)

Aug 24, 2010, 7:34 AM
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Exit rules for PAC 750? Can't Post

So there's been a tail strike on a PAC 750; it's not the first time. Some airplanes are more sensitive to CG than others, and some sort of mistake-proofing is a good thing.

Rules that the usual organizers know are good. But we all have seen the lines around the cabins of CASA's and Skyvans saying "no more than X jumpers behind this line." Yes, they are ignored sometimes, but the percentage of CASA and Skyvan loads that stall or have tail strikes appears to be smaller.

So -- is it raw poundage, wind resistance, or percent of the total poundage on the airplane that's the key factor? And what's a good way to ensure that the boundary isn't broken, even by people who aren't regular jumpers in the airplane? Because with the numbers getting bigger (I don't think the incidents in the last year or two will fit on one hand Unsure), sometime it's likely to get negatively exciting.

Wendy P.


Fast  (D 28237)

Aug 24, 2010, 9:45 AM
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Re: [wmw999] Exit rules for PAC 750? [In reply to] Can't Post

What we have figured out is that it mostly is about how the people on the outside of the plane are hanging on. If you have 4 people out and they are all at full arm extension it disrupts most of the airflow over the horizontal stabalizer. That leads to the stall. Our bigger way organizers have taken that into account when they are setting up the door lineup and it has made a difference.

The biggest problem we have found with too much weight in the tail is that the plane really jumps when that large group goes and it makes it pretty hard on late divers.


MakeItHappen

Aug 24, 2010, 9:55 AM
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Re: [wmw999] Exit rules for PAC 750? [In reply to] Can't Post

In reply to:
So there's been a tail strike on a PAC 750; it's not the first time.

When and where was there a previous PAC tail strike?

.


Premier SkymonkeyONE  (D 12501)

Aug 24, 2010, 10:09 AM
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Re: [MakeItHappen] Exit rules for PAC 750? [In reply to] Can't Post

I can remember several, but can't cite the dates. For example, I know of at least two wingsuit tail strikes. To be honest, one was on a Cresco, but that's the same airframe. On that one, at least, the guy was high enough that it ripped his tail wing in half.

PAC's are fine DZ airplanes; you simply cannot, under any circumstances jump up on exit; particularly in a wingsuit.

The rest of the discussion seems to be more about stalls.

We have had a really good track record with the one we own at Raeford FWIW.


theonlyski  (D License)

Aug 24, 2010, 10:31 AM
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Re: [MakeItHappen] Exit rules for PAC 750? [In reply to] Can't Post

In reply to:
In reply to:
So there's been a tail strike on a PAC 750; it's not the first time.

When and where was there a previous PAC tail strike?

.

I want to say there was a girl that broke her arm several months back


Premier wmw999  (D 6296)

Aug 24, 2010, 10:31 AM
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Re: [MakeItHappen] Exit rules for PAC 750? [In reply to] Can't Post

I know of at least one at Skydance during last year's American boogie. And I seem to recall some discussion around that time -- or it might have been stalls.

Neither is good news.

Wendy P.


timbre  (C 38095)

Aug 24, 2010, 10:49 AM
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Re: [MakeItHappen] Exit rules for PAC 750? [In reply to] Can't Post

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In reply to:
So there's been a tail strike on a PAC 750; it's not the first time.

When and where was there a previous PAC tail strike?

.

You're kidding, right? In my two years in the sport I've know of several. For example:

The American Boogie, 2009. Two stalls on successive jumpruns (same group, doing large scale formation exits), tailstrike on the second. I actually talked to the jumper who'd hit the tail (can't remember his name), he was OK but pretty shaken up.

The PAC may be a great airplane for DZOs, but it really isn't a great airplane for jumpers. Sure, you make the best of what you can get, but lets not all lie and pretend like there's no issue there.


davelepka  (D 21448)

Aug 24, 2010, 11:22 AM
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Re: [wmw999] Exit rules for PAC 750? [In reply to] Can't Post

 
One of the problems with the PAC is the low tail, and not just becasue of the risk of a tail strike, but also because the low tail can have it's airflow blanketed by the floaters (as already mentioned). One solution is for the floaters to stay tight to the fuselage.

The other problem, and this one contributes to the first problem is the jumper to door size ratio. With a door simialr in size to an Otter/Caravan, but holding fewer jumpers than an Otter/Caravan, you simply cannot have as many floaters or divers in the door as those other planes. With the doro set up in an PAC, it's possible to get most of the load either floating or in the rear of the aircraft, and when you add in the disturbed airflow to the left elevator, that's just too much weight to keep the nose down.

If you look at other planes with similar jumper to door ratios. you're left with the Skyvan and Casa. Both of those planes have the space to allow for a majority of the load to either be on or right next to the ramp, but as we have seen many times, the big tailgates will stall when this happens. This is why you see the big red lines in the cabins that state "No more than X jumpers beyond this line". Those operators take the weight and balance serisouly, and realize that their airplanes are different that some other planes where size of the door or cabin is what creates the limitation of jumpers in the door or door area.

I would go so far as to suggest that if you could keep the weight and balance under control, you could have floaters in any position outside a PAC, and the elevator would retain enough control authority to keep the nose down. Any aircraft, even without disturbed airflow over the elevator will stall if there is too much of an aft CG condition. Keep the weight (meaniing the jumpers) under control, and the airplane will remain upright.

Another huge part of this is communication with the pilot. Jumprun speed is a comprimise of saftey and comfort. Safety in that you want to maintain a fair margin above the stall speed, and comfort in that the floaters shouldn't have to fight to hang on, and the divers shouldn't get blasted as they celar the door.

If the pilot is aware that a larger group is going to be leavnig the plane, they can err on the side of safety and add a knots to the jumprun speed. By opening up the margin above stall speed, it gives the pilot more time between recognizing that the airspeed is beggining to fall off, and the actual stall. During this time he can try to lower the nose via the elevator, or add power to increase airspeed (and thus control effectiveness). If the pilot is not aware of a large group, then that extra margin does not exist, and eh may recognize the condition too late to do anything about it. Once the nose has begun to rise, it's adds drag and reduces airpeed and control effectivness, and as good as utrbine engines are, they do nto produce the 'instant' power needed in these types of situations. They take time to spool up after the throttle is advanced before they actaully produce thrust, time the pilot may not have.

It's really a simple proposition. If you want to be a big boy (or girl) and do big ways out of a PAC, you need to take responsibility for your actions. Inform the pilot of your plans, so he can take whatever precautions he sees fit. Learn to dive so you don't feel pressure to crowd the door for a quick exit, and you can stay forward in the cabin until the base has left (or is at least on 'set' in the count).

Let's face it, there are PACs flying jumpers all day, every day somewhere in the world, and they are not falling out of the sky. It's in these very specific instances that the stalls are occuring and two or three should be more then enough for people to catch on to the protocol.

I hate to say it, but I think part of this is an offshoot of the 'modern' jumper. They don't pack, they don't hang out at the bonfire, dont' know shit about much of anything. They know how to show up with their fancy jumpsuits and $9000 rigs, and make a few jumps, but they have no concpet about weight and balance, airflow over elevators or the mechanics of a jumprun. Yet they still feel like they should be on the big ways with all the cool kids, even though they can't organize themselves out of a cardboard box.


headoverheels  (D License)

Aug 24, 2010, 2:35 PM
Post #9 of 46 (2451 views)
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Re: [davelepka] Exit rules for PAC 750? [In reply to] Can't Post

In reply to:
It's really a simple proposition. If you want to be a big boy (or girl) and do big ways out of a PAC, you need to take responsibility for your actions. Inform the pilot of your plans, so he can take whatever precautions he sees fit.

On the back to back stalls on formation loads at the American Boogie, the pilot was certainly informed. I haven't made that many jumps out of their PAC, but I never heard any rules at all, other than leaving 2 or 3 people up front until the chunk leaves.


jakee  (C License)

Aug 24, 2010, 2:37 PM
Post #10 of 46 (2449 views)
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Re: [timbre] Exit rules for PAC 750? [In reply to] Can't Post

In reply to:
The American Boogie, 2009. Two stalls on successive jumpruns (same group, doing large scale formation exits), tailstrike on the second.

You gotta be kidding me?

What was the debrief like after the first one - "Well, that was scary, not sure what went worng, let's go try it again"?


Premier NWFlyer  (D 29960)

Aug 24, 2010, 2:46 PM
Post #11 of 46 (2443 views)
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Re: [jakee] Exit rules for PAC 750? [In reply to] Can't Post

In reply to:
In reply to:
The American Boogie, 2009. Two stalls on successive jumpruns (same group, doing large scale formation exits), tailstrike on the second.

You gotta be kidding me?

What was the debrief like after the first one - "Well, that was scary, not sure what went worng, let's go try it again"?

Yes, we just sat around with our thumbs up our asses after our friend hit the tail. Tongue

Two different pilots.

Two different PACs (as PAC #1 was being checked out after a tail strike).

Details here on the analysis that was done between jumps. It may not have (in retrospect) been perfect analysis, but rest assured it wasn't ignored.

(I was on the jump and provided my own details on what happened in posts 51 and 65 edit to add and 72 and 75)
http://www.dropzone.com/...ost=3604015;#3604015


(This post was edited by NWFlyer on Aug 24, 2010, 2:55 PM)


diablopilot  (D License)

Aug 24, 2010, 4:18 PM
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Re: [davelepka] Exit rules for PAC 750? [In reply to] Can't Post

Quote:
I hate to say it, but I think part of this is an offshoot of the 'modern' jumper. They don't pack, they don't hang out at the bonfire, dont' know shit about much of anything. They know how to show up with their fancy jumpsuits and $9000 rigs, and make a few jumps, but they have no concpet about weight and balance, airflow over elevators or the mechanics of a jumprun. Yet they still feel like they should be on the big ways with all the cool kids, even though they can't organize themselves out of a cardboard box.

What he said.


Premier billvon  (D 16479)
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Aug 24, 2010, 4:46 PM
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Re: [davelepka] Exit rules for PAC 750? [In reply to] Can't Post

>I hate to say it, but I think part of this is an offshoot of the 'modern'
>jumper. They don't pack, they don't hang out at the bonfire, dont' know shit
>about much of anything.

This was the complaint about "new" jumpers back when I started in 1991. Nothing has really changed.

>They know how to show up with their fancy jumpsuits and $9000 rigs, and
>make a few jumps, but they have no concpet about weight and balance,
>airflow over elevators or the mechanics of a jumprun.

Back then it was "they know how to show up with their brand new neon Racers and booty jumpsuits and make a few jumps, but they have no clue about accuracy jumping, round canopies, radial engines or how to spot without a good pilot. Heck, most have never even jumped a D-18 or landed a round."

>Yet they still feel like they should be on the big ways with all the cool kids,
>even though they can't organize themselves out of a cardboard box.

I don't think the cool kids are generally the ones trying to get on bigways any more.

But in any case, most jumpers aren't great organizers - which is why there's a market for organizers at DZ's and boogies throughout the country.


MakeItHappen

Aug 24, 2010, 6:03 PM
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Re: [timbre] Exit rules for PAC 750? [In reply to] Can't Post

In reply to:
In reply to:
In reply to:
So there's been a tail strike on a PAC 750; it's not the first time.

When and where was there a previous PAC tail strike?

.

You're kidding, right? In my two years in the sport I've know of several. For example:

The American Boogie, 2009. Two stalls on successive jumpruns (same group, doing large scale formation exits), tailstrike on the second. I actually talked to the jumper who'd hit the tail (can't remember his name), he was OK but pretty shaken up.

Tail strikes after a stall are a different issue than tail strikes on a normal jumprun.

Wendy's original post implicitly implied that tail strikes on a normal jump run were commonplace or have at least happened in the past.

Maybe, I've been snoozing on this issue, (I think not) but to my knowledge, there has not been a tail strike on a PAC under normal jumprun configurations.

BTW, as far as tail strikes out at Skydance go, I was a floater on an otter that stalled out there, way back in 1998 or 97. The last diver out hit the tail and caused $40K of damage to the otter. I have pics of it someplace here. REF had the audacity to ask each jumper on the load to say in writing that the stall was their fault. Only the NGs sent back that request.
I was also on the plane Trey flew (can't remember the name of it). It stalled on jumprun. As front floater, I let go.

IMHO, if a plane is stalling on jumprun, get off or out of it. Let the pilot deal with the change in cg. You paid your money and took your chances.

.


Deisel  (D 31661)

Aug 24, 2010, 6:21 PM
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Re: [MakeItHappen] Exit rules for PAC 750? [In reply to] Can't Post

I don't have hard data but I do know of tail strikes related to nose up jump runs and jumpers jumping up on exit. Those had nothing to do with stalls.

Also, we rolled ours over once by putting too many fat dudes outside the plane Frown

But for what it's worth, the PAC is an awesome platform and has just about everything you can ask for in a plane.


AndyMan  (D 25698)

Aug 24, 2010, 6:53 PM
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Re: [Deisel] Exit rules for PAC 750? [In reply to] Can't Post

In reply to:
But for what it's worth, the PAC is an awesome platform and has just about everything you can ask for in a plane.

I ask for stable flight under normal jump conditions. I am starting to think the PAC should only be used for student operations and very small RW, as it is not capable of stable flight with larger groups.

Hopefully I'm wrong and the solution is pilot education. But, I expect pilot education to fix the problem after the first, second, or third event. I can count 10 stalls on jump-run in only a few years, and those are only the ones that get talked about online. This means that pilot education is failing us.

I suspect the industry will decide that this plane is simply inappropriate for anything larger than a 4-way. I wish they'd hurry up and figure this out before someone gets seriously hurt.

_Am


davelepka  (D 21448)

Aug 24, 2010, 8:21 PM
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Re: [AndyMan] Exit rules for PAC 750? [In reply to] Can't Post

Quote:
I suspect the industry will decide that this plane is simply inappropriate for anything larger than a 4-way. I wish they'd hurry up and figure this out before someone gets seriously hurt.

I don't think that's the thing to figure out, What they need to figure out is that the plane is not appropriate for RW bigger than a 4 way if you intend to chunk it out the door. If you're willing to have your base exit with divers, who remain forward in the cabin until the base is leaving, then you should have no problems.

I jumped out of a Twin Bonanza for years that had room for two jumpers on the package shelf aft of the door. However, weight and balance prevented the jumpers from sitting aft of the door for take-off. The simple solution was for those two jumpers to sit in the lap (more or less) of the first row of jujmpers forward of the door for the take off and initial climb. At 800 to 1000ft, the jumpers would move rearward to the package shelf and take their seats.

Another, more modern, story, Jumping Spaceland's roving Skyvan two weeks ago. The load organizer puts together a 9-way magic carpet formation, and being an ace freeflyer agrees to fly the outside video slot. The problem is the rule in that Van is 9 jumpers max behind the red line. The simple solution was for the LO/video guy to remain forward in the cabin, and rush the door once once the formation had left. Sure he gave up the killer exit shot, and had to play a serisou game of catch-up once he got off the ramp, but 9 jumpers is the rule, and it's not optional.

It's a simple matter of jumpers realizing the very real effect that have on an aircraft's weight and balance, and acting accordingly.


Premier wmw999  (D 6296)

Aug 25, 2010, 5:41 AM
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Re: [davelepka] Exit rules for PAC 750? [In reply to] Can't Post

Quote:
It's a simple matter of jumpers realizing the very real effect that have on an aircraft's weight and balance, and acting accordingly
And guidelines written on the airplane are the best way -- that way you see them right there, and they're more likely to be followed.

Because an experienced jumper from another DZ might be the most experienced person on a load, and not know "the rules." Yeah, maybe that means that they shouldn't be considered the senior jumper, but it happens.

That's where mistake-proofing helps.

BTW -- I did not intend to imply that tail strikes were happening on commonplace jump runs. I could have been more specific in my wording, but I guess I wasn't.

Wendy P.


peek  (D 8884)

Aug 25, 2010, 7:00 AM
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Re: [wmw999] Exit rules for PAC 750? [In reply to] Can't Post

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And guidelines written on the airplane are the best way -- that way you see them right there, and they're more likely to be followed.

And it is amazing how many jump planes lack this simple safety feature.

One of the most important reasons to have one is so that if a jumper is doing something goofy, the others on the load who know better can point to the sign. Case closed (hopefully).

Does your aircraft have spotting lights? Red and green? Red and yellow? All three? What do these mean? Do they mean the same at the next DZ or in the next aircraft? What is the default exit order? When does this change?

(Personally I like Mike Mullins' King Air method even better than a sign. Tell them what to do over a loud PA, and have a mirror to verify what they are doing.)


Premier wmw999  (D 6296)

Aug 25, 2010, 7:05 AM
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Re: [peek] Exit rules for PAC 750? [In reply to] Can't Post

With Otters being the dominant large aircraft, and being incredibly tolerant, a whole lot of people are used to the thought that if you can cram them out there, a good pilot can handle it. Not that it's right, but it's reality.

Wendy P.


Feeblemind  (D 28621)

Aug 25, 2010, 8:53 AM
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Re: [diablopilot] Exit rules for PAC 750? [In reply to] Can't Post

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Quote:
I hate to say it, but I think part of this is an offshoot of the 'modern' jumper. They don't pack, they don't hang out at the bonfire, dont' know shit about much of anything. They know how to show up with their fancy jumpsuits and $9000 rigs, and make a few jumps, but they have no concpet about weight and balance, airflow over elevators or the mechanics of a jumprun. Yet they still feel like they should be on the big ways with all the cool kids, even though they can't organize themselves out of a cardboard box.

What he said.

Just a few things:

1) I have chucked an 8-way out of the Pac (good dirt dive, pilot advised prior to take off, quick climb out and fast count)
2) I have been outside the aircraft in the center and had the pilot help us leave as we hung out to long.
3) I have been on the camera step and seen the nose attitude of the plane changing (nose beginning to climb) I let go (hell I had wings lol)
4) I can't put the next gently so..... To make any comment, suggestion, assumption, etc that Ray does not train his pilots and watch over them like a hawk is absolute lunacy!!


Premier NWFlyer  (D 29960)

Aug 25, 2010, 9:41 AM
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Re: [Feeblemind] Exit rules for PAC 750? [In reply to] Can't Post

Quote:
4) I can't put the next gently so..... To make any comment, suggestion, assumption, etc that Ray does not train his pilots and watch over them like a hawk is absolute lunacy!!

I don't think I posted it in the other thread, but good evidence of that is the pilot who stalled the aircraft at the boogie last year ... that was his first (I think) and definitely his last flight of the boogie (not a regular SkyDance pilot). Ray took quick action on that one.


(This post was edited by NWFlyer on Aug 25, 2010, 9:42 AM)


Feeblemind  (D 28621)

Aug 25, 2010, 10:13 AM
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Re: [NWFlyer] Exit rules for PAC 750? [In reply to] Can't Post

In reply to:
Quote:
4) I can't put the next gently so..... To make any comment, suggestion, assumption, etc that Ray does not train his pilots and watch over them like a hawk is absolute lunacy!!

I don't think I posted it in the other thread, but good evidence of that is the pilot who stalled the aircraft at the boogie last year ... that was his first (I think) and definitely his last flight of the boogie (not a regular SkyDance pilot). Ray took quick action on that one.

Yes it was, and to the other mentioned stall, it was not a stall at all. The nose began to climb and the pilot performed the stall prevention maneuver which assisted all the folks camping outside the plane with a safe departure. I actually have it on video so I know it happened!


riggerrob  (D 14840)

Aug 25, 2010, 10:15 AM
Post #24 of 46 (1985 views)
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Re: [wmw999] Exit rules for PAC 750? [In reply to] Can't Post

In reply to:
With Otters being the dominant large aircraft, and being incredibly tolerant, a whole lot of people are used to the thought that if you can cram them out there, a good pilot can handle it. Not that it's right, but it's reality.

Wendy P.

.......................................................................

TwOtters may be tolerant, but I have seen a couple of them stalled because too many skydivers jammed the door on jump run.

I have also seen a pair of Skyvans damaged on the ground, because too many skydivers dirt-dived too close to the ramp.
Sadly, the second incident did not have to to happen, but I kept my mouth shut because I knew that no Perris skygod would listen to me. Instead I watched Melanie Conatser break into tears a the sight of her damaged Skyvan!

The bottom line is that ANY jump plane can be damaged on the ground or stalled in the air if too many people jam the door.


Premier wmw999  (D 6296)

Aug 27, 2010, 6:31 AM
Post #25 of 46 (1851 views)
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Re: [wmw999] Exit rules for PAC 750? [In reply to] Can't Post

So maybe a good first rule of thumb to at least try out (since hopefully we're not going to start a designed experiment to test the edges of the envelope Crazy):

1. No more than 1/3 the weight/number of jumpers outside the door (whichever is LESS)
2. Jumpers have to hug the fuselage

#1 might be mistake-proofed by making the step smaller, so that fewer people can reasonably fit outside.

#2 might be mistake-proofed by moving the bar above the door to where most people have to reach for it, so they naturally hold themselves tight.

Another option for #2 would be to get rid of the wonderful step that makes it so easy to hang a lot of jumpers out; that moves the air disruption to about 10" higher, which might improve the aerodynamics.

Regardless, while PACs seem to be a great plane for a DZ, they appear to have somewhat narrower operational limits than some other planes. If we operate within those limits, folks can continue to have fun in them. A couple of rules that can be written easily in the back of the airplane are more likely to be followed than "common knowledge," because common knowledge ain't always common.

Thoughts?

Wendy P.


(This post was edited by wmw999 on Aug 27, 2010, 6:39 AM)


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