Otter Tail-Passenger?

[JohnRich 4]

I couldn't come up with a good self-explanatory title for this one...

Most Otter's I've jumped have the tail section behind the passenger compartment closed-off, either with a secured door, or a web harness.

Some Otters, however, have this doorway open. And then it seems to be popular for a jumper to go back into that tail section to get away from the crowd.

So my question is this: does having a couple of hundred pounds that far back on the plane adversely affect the center of balance to a point where it could be a flight safety issue?

I've read quite a few NTSB accident reports (non-skydiving) where just a few inches aft on the center of gravity can make a world of difference in a stall...

[Ron 7]

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So my question is this: does having a couple of hundred pounds that far back on the plane adversely affect the center of balance to a point where it could be a flight safety issue?

Short answer....Yes.

Without a Pilots Operating Handbook. I can't give you a solid answer, but I am a Pilot, and did Weight and balance on large planes (DC-10's..ect) for a number of years.

"Arm times Weight equals Moment."

The farther away (Arm) from the Center of Gravity (COG or CG) the less weight it takes to effect the CG.

It might work fine most of the time, but when the bad stuff happens an aft loaded CG makes things much worse. An AFT CG makes an engine out in a climb a BAD thing.

Also the Average weight per the FAA for WB on LARGE aircraft to be 170 pounds. Now I am a kinda small guy and I weigh 163 pounds without gear..Add gear and I am 175-180 pounds. Also the FAA considers large AC over 12,500 pounds Max Takeoff Gross Weight...Anyone wanna guess what a TO weighs?

Using 170 is a bad idea. 200 is more realistic when you factor in Tandems and student gear.

PM Chris and ask him about this since he knows tons more than me about an Otter.

More info Here http://av-info.faa.gov/data/traininghandbook/faa-s-8083-1.pdf

"No free man shall ever be debarred the use of arms." -- Thomas Jefferson, Thomas Jefferson Papers, 334

[phoenixlpr 0]

I was jumpiing with a LET-410. There was a red line and a text in somewhere int mid of the plane. It said: not more than X people between this line and the tail......

[Jeth 0]

FWIW, my DZ uses that area often, whenver the load is full. They said the weight limit is 500 lbs for that area. They put 2 ppl back there. I have been in the hole a few times. Its great for roominess, but I don't like that I can't see anything in the plane or out the windows. Heres what they say about it:

"I don’t want to get too technical with weight and balances but we must take this into consideration. A Twin Otter has a useful load of 5,205 lbs. This means that it can carry 5,205 lbs pounds safety when properly loaded. When we fuel the otter we put about 1000 lbs of fuel. Now 5,205 lbs minus 1000 pounds of fuel equals 4,205. Now we take 4,205 and divide it by 24 (23 plus pilot) it equals 175 lbs. Which is about right when you consider Dawn who weights 90 pounds after getting out of the shower and Little Paul who isn’t little at all. So we know that 23 people can fit in the plane now how can we load this so it is the safest?

Most all lift produced by the otter comes from the wings (duh) so we can load the most weight under the wings. If we load the otter with two rows of ten this allows us to put most of the weight under the wings. If you load too much in the aft or rear of the aircraft in an emergency, the aircraft could lose control due to the aft CG (center of gravity). The same exists if you load the aircraft too much forward. This really doesn’t happen too much because we board the plane from the rear.

The ‘hole’ is designed to carry 500 lbs of weight although we don’t want to test this theory, this is what the placards and POH tells us. It is best that if it isn’t a full load that nobody sits in the ‘hole’. This keeps the weight forward which helps in an emergency. SDC will no longer allow three across the back. This put to much weight aft of the CG. The plane will not move until we load properly. "

"At 13,000 feet nothing else matters."
PFRX!!!!!
Team Funnel #174, Sunshine kisspass #109
My Jump Site

[AndyMan 7]

Skydive Chicago runs both of their -27 Otters with two people in the hole. They even installed seatbelts back there.

I'm not sure why they can do it but everyone else can not. It may have to do with their 3000 foot paved runway.

_Am

__

You put the fun in "funnel" - craichead.

[pilotdave 0]

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Most all lift produced by the otter comes from the wings (duh) so we can load the most weight under the wings.

Hahaha. That's really funny. (I hope they meant it to be funny...)

Dave

[tombuch 0]

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Now we take 4,205 and divide it by 24 (23 plus pilot) it equals 175 lbs. Which is about right when you consider Dawn who weights 90 pounds after getting out of the shower and Little Paul who isn’t little at all. So we know that 23 people can fit in the plane now how can we load this so it is the safest?

I'd reconsider the average of 175 pounds. Most rigs are in the 25 pound range, so your average human weight limit is reduced to 150. My hunch is that we weigh more (on average) than that. Has your DZ, or any DZ, done a real average of all passengers with gear? I'd be interested in what we really weigh.
.

Tom Buchanan
Instructor Emeritus
Comm Pilot MSEL,G
Author: JUMP! Skydiving Made Fun and Easy

[billvon 2,400]

>Has your DZ, or any DZ, done a real average of all passengers with
>gear? I'd be interested in what we really weigh.

We did. Our average was 205lbs, which includes tandems, AFF, experienced etc. We had quite a few SEALs working there for a while, which tended to up the average a bit.

[tombuch 0]

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We did. Our average was 205lbs, which includes tandems, AFF, experienced etc. We had quite a few SEALs working there for a while, which tended to up the average a bit.

I thought I remembered a higher number from Perris. If we allow for the SEAL's, and use an easy number like 200 pounds as an average, the 4,205 available load for this specific Otter becomes only 21 passengers. That's quite a difference. Alternatively, the 23 passengers exceed the allowable load by 575 pounds.

Weight and balance is important with Otters, and equally so with small Cessna's. Far too many accidents in the skydiving world begin with an overloaded airplane, then add an out of balance configuration. Some operators try to avoid this issue by reducing fuel loads, but son-of-a-gun, many of our accidents are the result of fuel exhaustion. Perhaps the safer solution would be to develop an accurate weight and balance for each load, and reduce the number of passengers if necessary.

It's also important to understand that the useful load for an airplane is specific to that airplane. Each aircraft has a different empty weight based on things like equipment, and a different gross weight based on things like flight surfaces and engines. So, the 4,025 pounds of useful load (plus 1,000 pounds of fuel) listed as the limit for this Otter may not be the same number used for Otters at other DZ's.

I'll get a bit more technical and mention that take off distance is based on gross weight, runway surface, density altitude (that includes temperature), and aircraft configuration. The maximum weight for a given day/runway may well be less than the allowable gross calculated in a weight and balance.

Jumpers should probably take this opportunity to talk with the DZO and ask to see an accurate weight and balance for each airplane in the fleet, and ask to see take off performance for that weight configuration on your runway on a hot day. My hunch, based on accident data, and general experience, is that our airplanes are often overloaded, and that this is a bigger problem with Cessna's than large turbines.
.

Tom Buchanan
Instructor Emeritus
Comm Pilot MSEL,G
Author: JUMP! Skydiving Made Fun and Easy

[diverdriver 5]

The FAA has been all over the SDC Otters and they are ok with the back being opened up. You have to get the paperwork to do it but taking out the divider is not that tough. Just gotta drill the right rivets. Also, on some otters fitted for regular passenger use that "back area" is where the toilet is. So, it IS ok for people to be back there at times.

We did a tabular CG for the otters and show it to the FAA each time they inspect. We run 800 pounds total if we are going to have a heavy load. I was able to fly 4 loads with 800 pounds. Seemed to work great as I needed to pee every 8 loads. But I digress.

Andyman, the SDC runway is 4,500 feet long. Departing from the intersection taxiway is about 3,500.

Now, consider that not all Otters are certified the same. The old -100 and -200 series have a Max Gross Takeoff weight of 11,579. Many operators run with benches in their planes. If you take the benches out you have more room and can sit tobogan style. I feel much better on the floor that way with wrestling matt flooring than benches. (personal preference). I know many operators feel that having benches help them load faster. It is more obvious where your seat is going to be (and importantly where your seatbelt is going to be) than sitting on the floor and using the belts on the side wall. There's benefits and drawbacks to both methods.

I would say that if the back is open for sitting don't let anyone go back there unless you have at least 15 people on board. There's just no need to be back there otherwise. The Feds have even remarked that back in the hole is probably the safest place to be in a crash when set up for jump ops. Just remember you are sitting directly on top of the batteries when sitting in the hole.

Also, don't let people sit back there if you have a bigway going out and they are NOT part of the bigway. That is unecessary weight on a large CG shift during exit. It's best to have your people who are going to be in the door on the exit sitting in the hole. As the floaters go out they come up and into position. So, you have a smooth transition of weight going aft and forward during climb out. It can help the pilot.

Hope that helps.

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

[riggerrob 558]

If you try sitting in the hole (aft of the door where the toilet used to be) of our King Air, you will subjected to all kinds of verbal abuse and the airplane will not taxi until you get your lazy butt forward of the (aft edge of the) door frame.


I don't want to fly in any Twin Otter with anyone sitting aft of the cargo door.

Hundreds of DZs have proven - over millions of flying hours - that airplanes will fly over-loaded, but they fall out of the sky when out-of-balance.

[Hooknswoop 19]

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Now we take 4,205 and divide it by 24 (23 plus pilot) it equals 175 lbs. Which is about right when you consider Dawn who weights 90 pounds after getting out of the shower and Little Paul who isn’t little at all. So we know that 23 people can fit in the plane now how can we load this so it is the safest?

175 pounds? No way.

Derek

[billvon 2,400]

>175 pounds? No way.

They may be using something like the airline standard, which is 170 lbs per person not including luggage. Of course airline passengers don't all have 30 lb rigs on.

[phoenixlpr 0]

Hm. 170 lbs in US ? :)

[billvon 2,400]

>170 lbs in US ? :)

Well, at least it was a long time ago, the last time I checked. Reality is probably closer to 200 lbs nowadays. Of course, changing it would cut into airline profits, so there is a powerful incentive not to change it.

[Ron 7]

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>170 lbs in US ? :)

Well, at least it was a long time ago, the last time I checked. Reality is probably closer to 200 lbs nowadays. Of course, changing it would cut into airline profits, so there is a powerful incentive not to change it.

I can think of one Airline that has changed it.

"No free man shall ever be debarred the use of arms." -- Thomas Jefferson, Thomas Jefferson Papers, 334

[phoenixlpr 0]

Or they might take a new practice to measure the passengers too and start charge them for overweight :).

[phoenixlpr 0]

Our manifest program takes it into account. It calculates a report about the current load, but the accuracy is questionable.

[Hooknswoop 19]

http://www.findarticles.com/p/articles/mi_m0UBT/is_40_18/ai_n6283703

http://stoenworks.com/A%20Weighty%20Issue.html

http://www.ainonline.com/Publications/RAA/RAA_04/raa_arcweighsp8.html

There may be resistance, but the fact is average passenger weight is above 170 pounds and above 175 with parachutes, etc on. I'm guessing that means Twin Otters that just fueled and take on 23 pax are overweight?

Derek

[gerrcoin 0]

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>170 lbs in US ? :)

Well, at least it was a long time ago, the last time I checked. Reality is probably closer to 200 lbs nowadays. Of course, changing it would cut into airline profits, so there is a powerful incentive not to change it.

Have you noticed what's happening to baggage allowances lately, especially on the no-frills carriers.

[JohnRich 4]

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Our manifest program takes it into account. It calculates a report about the current load, but the accuracy is questionable.

All you have to do is weigh every regular jumper once, in his gear, and put that number in the manifest database. Then when a load is ready to go, the program could total the weight for the known jumpers, and use an average for the unknowns, giving a total weight for the load. Then if the total exceeds the allowable maximum, have an alert pop-up so the pilot can make a decision. Excellent idea.

Now, the hard part will be getting the women on the scale...

[AggieDave 6]

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Now, the hard part will be getting the women on the scale...

Its easier then you think.

"Get on the scale or you don't jump."

Then of course go out of your way to make sure that only the manifester that is incharge of entering the data can see the readout and its kept quiet for folks who self esteem would be hurt.

--"When I die, may I be surrounded by scattered chrome and burning gasoline."

[el_chester 4]

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Skydive Chicago runs both of their -27 Otters with two people in the hole. They even installed seatbelts back there.

I'm not sure why they can do it but everyone else can not. It may have to do with their 3000 foot paved runway.

_Am

The runway one of those otters operates on during the winter does not measure that much, lies at 4700ft ASL, and is not paved.

And there's sometimes up to 3 people in the hole...

I don't like what I am writing! I had wondered about this too. Thanks for bringing it up!

--
Be careful giving advice. Wise men don't need it, and fools won't heed it.

[Jeth 0]

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Also, don't let people sit back there if you have a bigway going out and they are NOT part of the bigway. That is unecessary weight on a large CG shift during exit. It's best to have your people who are going to be in the door on the exit sitting in the hole. As the floaters go out they come up and into position. So, you have a smooth transition of weight going aft and forward during climb out. It can help the pilot.

Hope that helps.

Chris,
Thanks for that very informative explanation of SDC's planes. I am usually the 2nd group out when I'm in the hole. The group by the door goes, then I go after them.

When I read that explanation of the 175lb average I had doubts about that, too. But I also have doubts about the 30lb rig figure. For the record, my 190 rig weighs 23 lbs. But I am guessing that my instructors 105 rig weighs less. And most people at the DZ have smaller rigs than mine, so I don't know if 30lbs is accurate for a general average. Then of course the tandem rigs are freakin huge and weigh a ton. Also, some of those TM's are big guys, so I have no doubt that they are weighing in at more than 175lbs each. I was on a load once with all tandems, plus me and my instructor. The plane was packed, with a tandem in the co-pilot seat, and me/instructor in the hole. I have a feeling that load was overweight.

But I guess we have great pilots cuz the plane has always been held steady every load I've been on. )

"At 13,000 feet nothing else matters."
PFRX!!!!!
Team Funnel #174, Sunshine kisspass #109
My Jump Site

[billvon 2,400]

>Now, the hard part will be getting the women on the scale...

Oh, have them wear their weights and gear; that's more accurate anyway. That way no one will know what they really weigh.