Jump plane CG

I was watching skydiving operations for the first time this week. The first
three jumpers climbed into the 182 and it rocked back on the tail tiedown
ring. The next two got in and it came down on the nose gear, barely. There
appeared to be an attachment to the tie down ring to turn it into a tail
skid. Or maybe to keep prematurely opening chute's from snagging?

As the plane taxied out, it was rocking back and forth on the mains and it
appeared that the only thing keeping the nose gear in solid contact with the
ground was the thrust and the drag of the wheels in the grass. Takeoff
appeared normal although climb was pretty anemic.

Is this kind of loading and far aft CG typical?
--
Roger Long

Roger Long wrote:
I was watching skydiving operations for the first time this week. The first
three jumpers climbed into the 182 and it rocked back on the tail tiedown
ring. The next two got in and it came down on the nose gear, barely. There
appeared to be an attachment to the tie down ring to turn it into a tail
skid. Or maybe to keep prematurely opening chute's from snagging?

As the plane taxied out, it was rocking back and forth on the mains and it
appeared that the only thing keeping the nose gear in solid contact with the
ground was the thrust and the drag of the wheels in the grass. Takeoff
appeared normal although climb was pretty anemic.

Is this kind of loading and far aft CG typical?

I have jumped a few times from a 182. We've never had the tail
actually touch the ground on loading but the aircraft does tend to
wallow a little when people are moving around inside on the ground.
Aircraft are designed such that about 10% of the weight is on the nose
wheel and the rest on the mains. You want at least this for steering
and preventing overbalance but too much weight makes for large tail
forces (and associated drag) to achieve roatation.

The tail skid attachment is exactly that, a bumper for the tie down
for those over anxious jump pilots.

Inside the aircraft the jumpers will position themselves as far
forward as possible. A 182 can hold a pilot and 4 jumpers (the wide
body varient with extended wingtips - 182N or super skylane?? - can
hold 5 jumpers). With skydving gear weighing in at ~25lbs per jumper
and one extra pax the jump pilot needs to be fairly careful with the
fuel load. Generally jumpships carry enough fuel for 2 to 3 cycles
plus reserve. Cycle time for a 182 to 10k is about 15 minutes up and
about 3.5 minutes back down (shock cooling is a real issue here).

Typical seating arrangement (seats removed) is as follows for take off:
Jumper #1 beside the pilot kneeling facing forward
Jumper #2 (jumpmaster) kneeling behind Jumper #1 facing forward
Jumper #4 sitting behind the pilot, back and rig against the back of
the seat
Jumper #3 behind Jumper#4 kneeling between his legs facing forward.

On takeoff everyone leans as far forward as possible to get the
heavest parts of the body, the torso with rig, towards the front.
Jumper #1 needs to watch the right hand control column and
throttle,mixture etc. Jump pilot needs to watch Jumper #1 to make sure
that he doesn't try to use any of the above as a hand hold.

At about 1,000' the jumpers reposition for the climb. Jumper #1 now
sits facing forward with his back and rig to Jumper #2 who faces the
rear. Jumper #4 remains in position while jumper #3 now sits in
betweens his knees facing to the rear. Everyone kneels facing forward
on the jumprun. There are major trim changes involved as the jumpers
shift position and as they depart the aircraft. Now at altitude and
slow on the jumprun a stall is the worst possible senario. This is all
part of the skill of paradrop operations.

I agree with everything gerrcoin wrote and would add my experiences...
- all interior except the pilot's seat is removed from the aircraft (I
do mean EVERYTHING!).
- the right control yoke is removed
- an inclined plywood backrest is installed for the jumper by the door
to lean facing backwards against. This allows the jumpmaster to kneel
and bend forward over this jumper, effectively placing two people where
the right seat was, or three people above and slightly forward of the
main gear.
- this leaves room for three more jumpers (on a cold day) in the rear.
Four jumpers and the pilot are a normal load.

In article ,
gerrcoin wrote:


Typical seating arrangement (seats removed) is as follows for take off:
Jumper #1 beside the pilot kneeling facing forward
Jumper #2 (jumpmaster) kneeling behind Jumper #1 facing forward
Jumper #4 sitting behind the pilot, back and rig against the back of
the seat
Jumper #3 behind Jumper#4 kneeling between his legs facing forward.

On takeoff everyone leans as far forward as possible to get the
heavest parts of the body, the torso with rig, towards the front.
Jumper #1 needs to watch the right hand control column and
throttle,mixture etc. Jump pilot needs to watch Jumper #1 to make sure
that he doesn't try to use any of the above as a hand hold.

At about 1,000' the jumpers reposition for the climb. Jumper #1 now
sits facing forward with his back and rig to Jumper #2 who faces the
rear. Jumper #4 remains in position while jumper #3 now sits in
betweens his knees facing to the rear. Everyone kneels facing forward
on the jumprun. There are major trim changes involved as the jumpers
shift position and as they depart the aircraft. Now at altitude and
slow on the jumprun a stall is the worst possible senario. This is all
part of the skill of paradrop operations.


Hmm, I've only flown about 1100 loads of jumpers in a 182 but I've got
to say that loading plan leaves a lot to be desired. Those folks on
their knees will not stay put in the event of a crash...the seatbelt
will slip right over the legs. I always had everyone facing aft, which
puts the mass forward, with the seatbelt routed through the parachute
harness.

The last thing I want is skydivers "moving to improve the CG". Once
seated they stay put until jump run where they can get up and turn
around. The less movement they do the lower risk of an open container
in the airplane.

--
Dale L. Falk

There is nothing - absolutely nothing - half so much worth doing
as simply messing around with airplanes.

http://home.gci.net/~sncdfalk/flying.html

"Dale" wrote

.. I always had everyone facing aft, which
puts the mass forward, with the seatbelt routed through the parachute
harness.

Dale L. Falk

Not to be a smart ass, but I don't get it. Do you mount seatbelts to the
floor, or switch the seats around, or what?
--
Jim in NC


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In article ,
"Morgans" wrote:


Not to be a smart ass, but I don't get it. Do you mount seatbelts to the
floor, or switch the seats around, or what?

Better your ass smart than nothing at all! G

Part of the paperwork for using an airplane for jumping specifies
seatbelt installation. In the 182 or 206 all but the pilots seat are
removed and the seatbelts are installed in pretty much the normal
location as when the seats are installed with the exception that belts
will be added since you're normally carrying one extra person. In the
182 a pilot and four jumpers, in the 206 a pilot and 6 jumpers. In my
182 a seatbelt was installed at the rear bulkhead for the "extra"
passenger.

For many years seatbelts were pretty much ignored in jump planes. The
airplanes I first jumped from had the belts installed, but they were
tucked under the carpet out of the way. Then in the late 80's or early
90's a Twin Otter crashed in Perris, CA killing many jumpers in what
should have been a survivable crash. Parachuting is mostly
self-goverened, we realized that unless we wanted the FAA taking control
we needed to do better controlling ourselves and the use of seatbelts
became common almost overnight.

As soon as I started flying jumpers I started telling them to strap
in...the last thing I want is a skydiver crushing me against the panel
if things don't go right.

--
Dale L. Falk

There is nothing - absolutely nothing - half so much worth doing
as simply messing around with airplanes.

http://home.gci.net/~sncdfalk/flying.html

"Dale" wrote

Part of the paperwork for using an airplane for jumping specifies
seatbelt installation. In the 182 or 206 all but the pilots seat are
removed and the seatbelts are installed in pretty much the normal
location as when the seats are installed with the exception that belts
will be added since you're normally carrying one extra person.

Thanks.

And I always say, Better a smart ass, cause nobody likes a dumb ass! g

Know why they don't send donkeys to school? A: No one likes a smart ass.

But then there is; The worst a** I ever had was terrific!

O.K., that's it! g
--
Jim in NC


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Dale wrote:
Hmm, I've only flown about 1100 loads of jumpers in a 182 but I've
got
to say that loading plan leaves a lot to be desired. Those folks on
their knees will not stay put in the event of a crash...the seatbelt
will slip right over the legs. I always had everyone facing aft, which
puts the mass forward, with the seatbelt routed through the parachute
harness.

The last thing I want is skydivers "moving to improve the CG". Once
seated they stay put until jump run where they can get up and turn
around. The less movement they do the lower risk of an open container
in the airplane.


You are indeed correct. I jump in the UK and Ireland and here the
seatbelts are not required, or indeed fitted in most cases. But the
aircraft being used this side of the pond is not all that up-to-date
either. It is a concern for the jumpers and pilots alike and for any
emergency above 1,000' the load will usually choose to exit rather
than ride the aircraft down.

In article ,
"Roger Long" wrote:

I was watching skydiving operations for the first time this week. The first
three jumpers climbed into the 182 and it rocked back on the tail tiedown
ring. The next two got in and it came down on the nose gear, barely. There
appeared to be an attachment to the tie down ring to turn it into a tail
skid. Or maybe to keep prematurely opening chute's from snagging?

As the plane taxied out, it was rocking back and forth on the mains and it
appeared that the only thing keeping the nose gear in solid contact with the
ground was the thrust and the drag of the wheels in the grass. Takeoff
appeared normal although climb was pretty anemic.

Is this kind of loading and far aft CG typical?

I've flown 182s and 206s a lot hauling jumpers. With reasonable loading
it's actually pretty hard to get a CG aft of the limit.

Was there a pilot in the seat when the airplane rocked back onto the
tailstand? It's normal when loading for the airplane to rock back some
since you load from the rear to the front. Most of the single Cessna
line will set tail-low if you have the rear seats filled.

--
Dale L. Falk

There is nothing - absolutely nothing - half so much worth doing
as simply messing around with airplanes.

http://home.gci.net/~sncdfalk/flying.html

I have done most of my jumpsout of a 182 and the reason for getting the weight
as far forward is to assist the pilot in case of an engine failure. Any
operator that allows jumpers to sit in the described position and not forward
is an operator who is either ignorant or just does not care. Either case the
safety of the "passengers" is not being cared for.

"Sometimes you get the brightest light from a burning bridge" D.Henley