Pac 750 stalls on jump run

[TheSultanofScud 0]

I may be showing up late to the game, but I thought my $.02 might be relevant.

I am a PAC pilot who is actively flying at a dropzone. I can tell you that we have routinely been flying large RW groups without issues.

Even as recently as last weekend I recall flying at least one 14-way...I don't know how many floaters were hanging out, but from a good glance during the climb-out I can tell you that it was pretty lonely up front. Even with most of the load crowding the door, it was easy to maintain a constant airspeed and attitude without trim.

The PAC is a nose-heavy airplane by design. Even the design of the fuel system and the location of the forward tanks is used to offset large groups that typically create an aft and adverse CG.

Bottom line: The airplane is designed and engineered to be controllable with a single large RW group. Groups larger than 14 would be challenged to even find room in the aft end of the small cabin to get into an uncontrollable Aft-CG situation

For the purposes of flight planning for the actual climb and jump-run: As long as the jumpers are evenly distributed throughout the cabin, the PAC will be within CG. There are several official weight and balance examples located in the PAC750XL Pilot Operating Handbook (POH) which is serial-number-specific to the individual airplane. These reflect at least three different loading configurations for my specific ship. Examination of these and empirical knowledge of the airplane have left me with little doubt about what the PAC can handle.

As long as proper planning is used in the final seconds of the pattern and the early seconds of the jump-run, these nasty surprises can be averted.

For your information, I prefer to carry no less than 80-82 knots of indicated airspeed as I commence my jump-run, particularly on the large loads. I extend flaps early to achieve the last few hundred feet of climb, lower the nose as I adjust power settings, and give the green light with a slightly nose-low attitude.

During the jump run, I carry very little power. Depending on the size of the individual groups, I slowly reduce power and airspeed as the aircraft gets lighter, to give later groups a smoother exit. I use the built in PA system to alert later groups of the slowing ground speed, and thus, the increased need for time between groups.

With big ways, I generally carry my initial jump-run power setting for quite some time. As soon as I feel bodies leave, I slowly reduce power such that the engine will be at idle by the time the last few jumpers are hitting the door.

In any case, I am in a slight descent with a level or, more often than not, low nose. It is better to lose 2-300 feet and climb out without that prop blast trying to strip you from the plane, n'est pas?

Good planning in the PAC=Constant and/or appropriate airspeed + nose-low attitude + appropriate power setting and changes + and awareness of the group numbers and sizes.

Doesn't seem too different from most jump planes.

Thanks for the thread...It's a worthwhile discussion.

[rehmwa 2]

Quote

For your information, I prefer to carry no less than 80-82 knots of indicated airspeed as I commence my jump-run, particularly on the large loads. I extend flaps early to achieve the last few hundred feet of climb, lower the nose as I adjust power settings, and give the green light with a slightly nose-low attitude.

During the jump run, I carry very little power. Depending on the size of the individual groups, I slowly reduce power and airspeed as the aircraft gets lighter, to give later groups a smoother exit. I use the built in PA system to alert later groups of the slowing ground speed, and thus, the increased need for time between groups.

With big ways, I generally carry my initial jump-run power setting for quite some time. As soon as I feel bodies leave, I slowly reduce power such that the engine will be at idle by the time the last few jumpers are hitting the door.

In any case, I am in a slight descent with a level or, more often than not, low nose.

This is nearly exactly what our pilot does (my rough opinion on how the plane feels on jump run - clearly low nose, medium speed, and yes, he also adjusts as the plane empties) and we've never had an issue with any size group. We were putting 8way chunks + vid off this Sunday and it's flawless and there is not much kick even for those in the plane.

Of course, our pilot is one of the best I've had the fortune to fly with. When we inform him of the group size and climb out, he just smiles confidently and does it perfect.

We need to tell him that more often.....

...
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]

The thing that has been mentioned yet never stated is what are the specific airspeeds and power settings needed for groups climbing out with 5 outside? I see your 80-82 KIAS but what is the power setting you typically see to accomplish that? You extend flaps but how much?

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

[BenediktDE 2]

Quote

Here is a video of two different stalls in a Pac750XL.
http://www.youtube.com/watch?v=4jfAaEWxJ2I

You can use these two videos as training videos! Everytime I am outside I have an eye on the horizon. This way you'll see a stall coming and get a feeling of how had the pilot has to work at the moment.
Try it with the videos - you can see them coming ealier then.

Maybe it would be a good idea to train that "feeling for your plane"?

For every complex problem there is an answer that is clear, simple, and wrong.

[TheSultanofScud 0]

Chris,

I will answer your question and then follow up with what happened to me today. I also saw the new PAC section on diverdriver.com...I will post more information there in the coming days.

The typical one-size-fits all power setting for jump run is 18 PSI on the torque indicator and 1850 RPM on the propeller RPM. You give the door below 20 PSI, and give the green light with 18 or less PSI. With a slight descent this generally yields between 80 and 85 knots depending on appropriate pitch.

Today I stepped on my Lingham. Today, for the first time, I had to execute an aggressive positive control maneuver to recover from an imminent stall on jump-run.

I was flying the typical jump-run at just above 80 knots anticipating several small groups. Typically, when larger groups with multiple floaters manifest, they give me advanced notice of their presence so I can fly a faster jump run...this has become an expectation and an understanding following the Waseka stall that spawned this thread.

My assumption was incorrect. This load was to be a 10 way composed of 9 medium to large men and one light woman.

The jump-run began in level flight seconds after completion of the climb. I was flying just above 80 knots with 20 degrees of flaps (standard) and approximately 17 PSI of torque...which is 1 PSI less than the one-size-fits all power setting used when jumpers take the door. With every load I've flown so far other than the eight and nine ways, this has been almost negligible within a range of 16-19 PSI at the beginning of jump-run. At 17 PSI, 80 Kts, and 20 degrees of flaps, I was in the typical slow descent I would expect.

The biggest jumper on the load was sitting next to me prior to the climb-out and is likely in excess of 6' 4" and 280 pounds. Everything, as far as I remember, was normal at first. According the jumpers, their climb-out was somewhat longer than usual. There were five floaters and five remaining close to the door. .

I didn't notice the excessive CG shift until it was too late. As soon as the last and biggest jumper moved to the rear of the plane, trouble started. Some seconds after the floaters took the door, I ran out of stick travel on the forward end. I had not changed power settings and up until this point, airspeed had remained at approximately 80 knots or so.

The aircraft pitched above the horizon as the jumpers held on, and I rolled left in accordance with the aggressive positive control maneuver I was instructed to use to lower the nose. Single-engine aircraft having engines which were manufactured in the US typically have natural left-turning tendencies (as stated before in this thread)...In the event of an impending stall where the pilot cannot lower the nose conventionally, he or she can take advantage of the airplane's tendencies to dive in turns (like canopies) to lower the nose and prevent the stall. By rolling to the left, the pilot also takes advantage of the left-turning tendencies, which aid in a more rapid and deliberate recovery.

Bear in mind, this maneuver does not work when the aircraft is already stalled. This maneuver only works in the seconds leading up to the stall, when the aircraft is still aerodynamically flying and the pilot still has roll-control authority. If this is used when the aircraft has already stalled, and is therefore falling with the jumpers, using this technique could potentially aggravate the situation...IMHO.

So there it is...I reference my earlier post. Planning, planning, planning. I put it on myself; I should have been more proactive and known about the group size in my airplane without being told. With 13-14 people it's harder to induce this situation; with the smaller cabin, jumpers have no choice but to remain up front as ballast. The 10 to 12 head loads will stick in my mind...the potential is there to inadvertently crowd the door.

As pilots we have to know what groups are getting out and when. We have to understand that jumpers will not be familiar with the CG of specific makes and models aircraft. As much as I desire that jumpers meet me half way (which they always have, otherwise) and alert me when they are putting out large groups, I put this one on myself.

I've always scoffed at the notion of someones stalling the nose-heavy PAC on jump-run. I'm eating some of my own words at dinner tonight. Anyone want a bite?

[davelepka 4]

Quote

Typically, when larger groups with multiple floaters manifest, they give me advanced notice of their presence so I can fly a faster jump run...

Whenever I fly at a boogie with Mike Mullins in his King Air, just after we pull away from the loading area he asks, "How big is the first group?".

I'm not sure if this is related to different jump run speeds, or if it's related to spotting, but he does it. If you are in an aircraft where you have different procedures for different group sizes, this might not be a bad SOP.

It's not that I don't trust skydivers....well, OK, I don't trust skydivers, and anytime their performace will have an effect on my situation, I make sure that there is a crystal clear understanding of what I expect from them, and what they can expect from me. In reality, of course, shit happens, and things don't always go as planned, but at least I know going in that everyone is on the same page.

[skyjumpenfool 2]

No shit, there I was...... again! Hanging on the camera step and being peeled off by a stall. Even though the pilot took full responsibility for the incident, I feel like an idiot because I didn't let him know of the large exit group prior to exit.

As I climbed into the plane, I noticed one of our most experienced jumpers, a guy with tens of thousands of jumps who never misses a step, sitting towards the front of the plane. And, I foolishly assumed he would let the pilot know about the large group leaving the plane. Of course, this would not be the case.

So, once again, we found ourselves in a completely avoidable situation. It's no wonder the "Sultan" doesn't trust skydivers. This was not the fault of the pilot alone no matter how quickly he accepts responsibility. We skydivers need to communicate with our pilots! I for one will personally talk to a PAC pilot about large exit groups no matter how many others may have already done so. Even at the risk of being repetitive. Just like doing pin checks or setting our AAD’s, communicating with pilots is a vital safety issue. Every dirt dive needs to include a discussion about the exit, how to do it safely and how we intend to communicate the plans to the pilot. And, we’re not just talking about PAC’s here.

Bottom line… “Communicate your plans with your pilots!!!”

Birdshit & Fools Productions

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

[JohnDeere 0]

Quote

Bottom line… “Communicate your plans with your pilots!!!”

+1 I'm almost never in the "big group". I mostly free fly but if i know a big group is going first I let the pilot know. We fly a caravan and otter but i dont need to take thing's for granted! Come on people how hard is it to tell the pilot at 11 - 12,000 ft how big the first group is. At my DZ most video/ tm's ask how big the first group is. Get in the habbit of it!

Nothing opens like a Deere!

You ignorant fool! Checks are for workers!

[ufk22 32]

No shit, there I was...... again! Hanging on the camera step and being peeled off by a stall.
-------
Sounds to me like another video-man induced stall.

This is the paradox of skydiving. We do something very dangerous, expose ourselves to a totally unnecesary risk, and then spend our time trying to make it safer.

[skyjumpenfool 2]

Sorry to bump the thread again, but I thought those who were following it would appreciate this photo...

Birdshit & Fools Productions

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