PD Reserve versus PD Optimum Landing Kinetic Energy

[shadeland 5]

I've heard this a few times: PD Optimums, despite being a size bigger, have roughly the same descent/forward speed as a a PDR one size smaller, negating most of the benefit of having a larger reserve for unconscious/no input landings.

Flight configuration would be brakes stowed, unconscious landing. People get low bulk reserves partly because the assumption is the landing speed (ground impact speed) would presumably be lower with the lower wing loading.

Example: A Optimum 160 would land about as hard as a PDR 143 (the next size down).

I've heard that from a few riggers, but I haven't seen any data to support that. I've got two rides on an Optimum 143, but of course I don't have anything to compare it to (or quantitative data).

Does anyone have any data to support or refute this? Is this one of the factesque things that gets widely reported and thus taken as fact?

Can someone from PD chime in?

"It's been widely report John, and that makes it fact-esque" -Stephen Colbert.

(Reposting this because initially I used the term "forward speed" to describe the kinetic energy effect on a human instead of "forward/descent" and the first two comments concentrated on that. I re-worded it to be more clear).

[sundevil777 93]

Not helpful to repost. Kinetic energy is still not all that is important. Better to just keep it in one thread and adjust the discussion.

People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

[20_kN 0]

shadeland

I've heard this a few times: PD Optimums, despite being a size bigger, have roughly the same descent/forward speed as a a PDR one size smaller, negating most of the benefit of having a larger reserve for unconscious/no input landings.

hmmm I havent flown either but PD's website would suggest the opposite is true: the PD Reserve needs to be bigger than the Optimum to maintain the same decent speed.

If you look at their recommended wingloading chart, assuming a novice with an exit weight of 200 lbs for example, PD recommends a 193 Optimum or a 235 PD Reserve for that weight.

The rest of the wingloads on their chart show the same thing: a larger PD Reserve is needed for a given exit weight relative to the Optimum series.

Best thing to do might be to call PD and ask.


http://www.performancedesigns.com/products/optimum/

http://www.performancedesigns.com/products/pdreserve/

[gowlerk 1,903]

Optimum reserves are not ZP. They are made of a special fabric that only PD seems to have access to. I'm not sure why, I don't think they own the mill. The fabric is softer and folds easier than the material PDRs are made of. That is why it packs smaller. No canopies are made of F-111 material. F-111 was the name of a product that has not been produced for decades. We just use the term like we use Kleenex to describe tissues.

PD probably rates the maximum weights for their reserves by how much you can load them and still get a decent flare. The faster a canopy is going the more energy will be available for the flare. That makes me speculate that Optimums go faster. But that is just speculation. Note that they have higher recommended weights for more experienced pilots.

I do not expect PD or any other manufacturer to answer questions like this. All the information you will get is what is already on the spec sheet that they publish. They are tested to meet whatever TSO standard they are rated at. There is no reason for them to share beyond that. The best way to find out the speeds involved would be to find out what the TSO standard is. Then you would at least know the minimum they had to meet.

A little research and I found where to get the relevant standards. A document called SAE AS 8015b. It's available to download at the link below. But it costs $78.00 and I don't want it bad enough to pay. Maybe you do?

http://standards.sae.org/as8015b/


New info. This PIA document seems to cover it.

http://www.pia.com/piapubs/TSDocuments/TS-135v1.4.pdf



Knock yourself out trying to understand it if you are not an engineer.

[mark 102]

gowlerk

A little research and I found where to get the relevant standards. A document called SAE AS 8015b. It's available to download at the link below. But it costs $78.00 and I don't want it bad enough to pay. Maybe you do?
. . .
New info. This PIA document seems to cover it.
http://www.pia.com/piapubs/TSDocuments/TS-135v1.4.pdf

PD Optimums are certificated to the standards of TSO-C23d/AS 8015B. These documents are included in the appendices to the 2005 Parachute Rigger Handbook, I think still available online as a free download.

TS-135 has the standards for TSO-C23f.

-Mark

[gowlerk 1,903]

I have a hard copy of that. If I'm reading it correctly the average speed total velocity fully loaded is not to exceed 36 ft/sec with the brakes stowed. (24.5 mph) The descent speed is not to exceed 24 ft/sec. (16.4 mph)

I can see no spec for speed in full flight. Probably because there is none.

[shadeland 5]

gowlerk

I have a hard copy of that. If I'm reading it correctly the average speed total velocity fully loaded is not to exceed 36 ft/sec with the brakes stowed. (24.5 mph) The descent speed is not to exceed 24 ft/sec. (16.4 mph)

I can see no spec for speed in full flight. Probably because there is none.

Full flight I wouldn't care as much about. Hopefully if if the toggles are popped it's because I'm conscious, and then I'm not as worried about landing a reserve.

It's my impact speed unconscious. Is that speed going to be similar between an optimum 160 and PDR 143, or a Optimum 143 and a PDR 126, etc. Or will more fabric mean a lower speed/lower kinetic energy.

If it's the same, I'll just buy a PDR.

[gowlerk 1,903]

There has been a lot of talk about unconscious landings lately. My feeling is that in this situation you are in a world of trouble anyway. Ram air canopies are not forgiving of uncontrolled landings. You would be far better off under a round parachute than a ram air. But that is not practical in the skydiving world.

One size larger or smaller is not going to make a big difference. If you want to feel safer in this rare circumstance you really should have at least a 250 sq ft canopy. And even then you are in trouble. In reality skydivers have given up trying to deal with this possibility in order to have small canopies with almost main like flaring power in the top of their containers.

[JerryBaumchen 1,046]

Hi Mark,

Quote

PD Optimums are certificated to the standards of TSO-C23d/AS 8015B.

I have posted about this before on this site.

At the 2005 Symposium, a friend and I were sitting in a restaurant with one of the 'major players' of PD. During the course of that discussion, he informed me that PD had gotten/obtained an exemption to the 'total velocity' req'ment of the TSO standard because their Optimum canopies exceeded the standard.

By how much, I have no idea.

I do not have anything in writing regarding this conversation. I was not told to keep this information to myself.

Jerry Baumchen

PS) I just did a quick review of all of the TSO standards & 'total velocity' first comes up in C23d, AS8015, Rev. B. It states ' . . . the total velocity shall not exceed 36 ft/s (11.0 m/s), in an unaltered post deployment configuration . . . ' Note that this is airspeed and not ground speed. If the dummy or you are going downwind, you will possibly be exceeding these limits.

[shadeland 5]

gowlerk

There has been a lot of talk about unconscious landings lately. My feeling is that in this situation you are in a world of trouble anyway. Ram air canopies are not forgiving of uncontrolled landings. You would be far better off under a round parachute than a ram air. But that is not practical in the skydiving world.

One size larger or smaller is not going to make a big difference. If you want to feel safer in this rare circumstance you really should have at least a 250 sq ft canopy. And even then you are in trouble. In reality skydivers have given up trying to deal with this possibility in order to have small canopies with almost main like flaring power in the top of their containers.

Are we sure about that?

There are AAD fires for unconscious jumpers that land wingloadings in the range we're talking about, and are survivable. Even major injury free (limp bodies can sometimes pull that off). It's not ideal, and of course you're at the mercy of where you land, if its downwind, etc, and you go from a dusting to far more serious injuries quickly...

But what is the delta? Worth buying an LPV or na?

We're lacking a lot of data here. In the absence, we've made some assumptions. In some cases, those assumptions are discussed as if proven facts.

[SethInMI 145]

Jerry,

***
4.3.9.1 RATE OF DESCENT TESTS (METHOD 2):
The rate of descent corrected to standard day sea level altitude conditions shall not exceed 5
ft/sec (1.5m/sec) at touchdown with appropriate control manipulations and the average rate of
descent shall not exceed 24 ft/sec (7.3 m/s) in the unaltered post deployment configuration over
a minimum interval of 100 ft (30.5m). These tests may be combined with other tests in this
section
NOTE: If the total velocity exceeds 36 ft/sec at maximum certified weight, the container or
harness (if integral to the container) must be marked in an area readily visible to the user: “For
experienced parachutists only. The owners manual contains experience requirements.”


Not sure if PD is using this exception, since the exception requires a note on the container, not the reserve itself. But the exception is saying the reserve glide ratio with brakes stowed is greater than 1.12, mark the container and set the max weight for descent rate alone.

Do sport containers contain such text by default (I can't check mine right now)?

It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

[shadeland 5]

JerryBaumchen

Hi Mark,

Quote

PD Optimums are certificated to the standards of TSO-C23d/AS 8015B.

I have posted about this before on this site.

At the 2005 Symposium, a friend and I were sitting in a restaurant with one of the 'major players' of PD. During the course of that discussion, he informed me that PD had gotten/obtained an exemption to the 'total velocity' req'ment of the TSO standard because their Optimum canopies exceeded the standard.

I was looking at the maximums for various reserves. The PD Optimum 126, for example, would put me personally at about 1.5 WL. The stated never exceed maximum is 254 lbs, which would be about a 2.0 loading. My guess is that at a 2.0 loading that would exceed the TSO standard for landing speed (but that's just a guess).

Compared to the Icarus Nano 126, the maximum weight is 167, which is about 1.3 WL. That is probably under the TSO limit (again, just a guess).

[shadeland 5]

sundevil777

Not helpful to repost. Kinetic energy is still not all that is important. Better to just keep it in one thread and adjust the discussion.

I would say kinetic energy is the only important factor. Those are the forces on the body at impact with the ground. Specifically, I'm referring to unconscious, no input landings (with brakes stowed). There's a lot of factors involved in those forces, how much and how they're spread out (hitting the ground versus hitting the sider of a building, for example) but it starts with the forward speed (horizontal and vertical component) of the reserve in question.

[gowlerk 1,903]

Quote

Are we sure about that?

There are AAD fires for unconscious jumpers that land wingloadings in the range we're talking about, and are survivable.

In an unconscious landing situation I'm not sure about anything. There would be a huge element of luck involved. What does survivable mean? Probably the difference between hitting a soft open field and a wall or a tree. I'm all in favour of larger reserves for anyone and everyone. I just don't think this is a major reason why.

[JerryBaumchen 1,046]

Hi Seth,

Quote

Not sure if PD is using this exception

Without getting up off of my keester and looking ( did that once already today ), I believe that your quote is from C23f. My quote is from C23d, no longer in effect for new certifications.

Also, I 'think' that TSO C23f has some wording, put in the actual TSO by the FAA, ( not the referenced standard ) that does not allow this 'alternate method of testing.'

It is important to know that the referenced standards ( NAS 804, AS8015B, etc ) are written by sources outside of the FAA. These 'standards' are then submitted to the FAA for inclusion in the actual TSO. However, the FAA is not bound by what is in the standard. The FAA 'owns' the TSO and they can change things as they want.

Jerry Baumchen

[SethInMI 145]

shadeland

We're lacking a lot of data here. In the absence, we've made some assumptions. In some cases, those assumptions are discussed as if proven facts.

Agreed. A few things it would be good to know:
1. What are the descent rates for reserves with stowed brakes at various wingloadings?
2. What happens to a body that impacts the ground at the range of speeds from the answers to question 1? Obviously this depends a lot on the ground, but a lot of DZs are composed of and surrounded by fields and forests, so that is what I would guess is the likely landing surface.
3. Given that a jumper is already incapacitated, likely with severe head trauma, what does that do to their chances of surviving ground impact? If you have a fractured skull already, what will slamming your head into the ground do to it?

I am pretty sure some answers to the 1st question are around online, but I can't find them. I thought a German group had done some tests? Obviously some data for it could be crowd-sourced easily by people checking their digtal altis for descent rate before unstowing brakes.

For the 2nd question, maybe look at pedestrian vs truck impact studies?

For the 3rd, no idea.

If you had these answers, you could choose a reserve size that gave you whatever % chance of survival you wanted. 1%, 10%, 70%? pick a size!

Seth

It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

[mark 102]

SethInMI

Jerry,

***
4.3.9.1 RATE OF DESCENT TESTS (METHOD 2):
The rate of descent corrected to standard day sea level altitude conditions shall not exceed 5
ft/sec (1.5m/sec) at touchdown with appropriate control manipulations and the average rate of
descent shall not exceed 24 ft/sec (7.3 m/s) in the unaltered post deployment configuration over
a minimum interval of 100 ft (30.5m). These tests may be combined with other tests in this
section
NOTE: If the total velocity exceeds 36 ft/sec at maximum certified weight, the container or
harness (if integral to the container) must be marked in an area readily visible to the user: “For
experienced parachutists only. The owners manual contains experience requirements.”

Not sure if PD is using this exception, since the exception requires a note on the container, not the reserve itself. But the exception is saying the reserve glide ratio with brakes stowed is greater than 1.12, mark the container and set the max weight for descent rate alone.

Do sport containers contain such text by default (I can't check mine right now)?

Jerry was in ahead of me. (Thanks!) Your quote is indeed from TS-135v1.4, the standard for TSO-C23f. However, the FAA did not agree to Method 2. See page 5 of the attached cover letter.

-Mark

TSO-C23f.pdf

[sundevil777 93]

shadeland

***Not helpful to repost. Kinetic energy is still not all that is important. Better to just keep it in one thread and adjust the discussion.

I would say kinetic energy is the only important factor. Those are the forces on the body at impact with the ground. Specifically, I'm referring to unconscious, no input landings (with brakes stowed). There's a lot of factors involved in those forces, how much and how they're spread out (hitting the ground versus hitting the sider of a building, for example) but it starts with the forward speed (horizontal and vertical component) of the reserve in question.

Kinetic energy is NOT the only important factor. Hitting at a shallow angle is of course very different than straight down. Both scenarios could be at the same speed, so same kinetic energy.

People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

[shadeland 5]

sundevil777

******Not helpful to repost. Kinetic energy is still not all that is important. Better to just keep it in one thread and adjust the discussion.

I would say kinetic energy is the only important factor. Those are the forces on the body at impact with the ground. Specifically, I'm referring to unconscious, no input landings (with brakes stowed). There's a lot of factors involved in those forces, how much and how they're spread out (hitting the ground versus hitting the sider of a building, for example) but it starts with the forward speed (horizontal and vertical component) of the reserve in question.

Kinetic energy is NOT the only important factor. Hitting at a shallow angle is of course very different than straight down. Both scenarios could be at the same speed, so same kinetic energy.

Fair point, but in this case kentic energy is the primary factor we have influence while unconscious: the size of our reserve. Glancing blows (level impact) or direct blows (side of building) will influence outcome as well, but that’s more luck of the draw.

[gowlerk 1,903]

I guess I just think about this issue differently. I think of my wing as my glider. Like it is an aircraft. Because it is. I consider myself a pilot under it. Like any other aviator I accept a certain amount of risk when I leave the surface of the Earth and play in the sky. If I get into a situation where my aircraft is going to land uncontrolled I do not have a great expectation that I will survive. If somehow I do survive I fully expect to be badly injured. What other aircraft could save me in such a situation?

I don't think that the manufacturer of my wing is responsible for making my wing so slow and boring as to prevent that. And I'm not willing to carry a large enough reserve wing to prevent it.

A pilot emergency or bail out rig is also covered by the same rules. Most of them are rounds and most pilots have never flown a ram air parachute. If you want the largest chance of surviving an uncontrolled landing get a round reserve. But it is far more common, by a large factor, for skydivers to be in control of their reserves. Life is full of design compromises. You have to choose your own sometimes. I choose to play the odds that work for me.

[shadeland 5]

gowlerk

I guess I just think about this issue differently. I think of my wing as my glider. Like it is an aircraft. Because it is. I consider myself a pilot under it. Like any other aviator I accept a certain amount of risk when I leave the surface of the Earth and play in the sky. If I get into a situation where my aircraft is going to land uncontrolled I do not have a great expectation that I will survive. If somehow I do survive I fully expect to be badly injured. What other aircraft could save me in such a situation?

I don't think that the manufacturer of my wing is responsible for making my wing so slow and boring as to prevent that. And I'm not willing to carry a large enough reserve wing to prevent it.

A pilot emergency or bail out rig is also covered by the same rules. Most of them are rounds and most pilots have never flown a ram air parachute. If you want the largest chance of surviving an uncontrolled landing get a round reserve. But it is far more common, by a large factor, for skydivers to be in control of their reserves. Life is full of design compromises. You have to choose your own sometimes. I choose to play the odds that work for me.

I don't disagree with anything you said there. I follow the same outlook for the most part.

No gear can prevent a bad outcome in all situations, however we can improve our chances with the choice of gear (AAD versus no AAD, helmet versus no helmet, snag-resistant camera mounts, etc.) The fundamental question I'm asking is are we bettering our chances with LPV reserves versus standard.

I've heard more than once that the Optimum flies as fast (horiztonal+vertical) as a PDR one size smaller, negating the benefit of having more fabric over your head (the assumption that more fabric over your head leads to a slower speed, resulting in lower kinetic energy when impacting the big-blue rock or structures upon it).

I'm asking

A) Is it true (while I've heard it said, I've seen zero data to support it)
B) More generally, can we better our outcomes in an unconscious scenario with a size larger reserve

My assumption on B has been that yes, more fabric the better. If that's not the case, then there's no need for an LPV reserve (or at least, no need for an Optimum). I'm confident I can safely land a reserve several sizes larger than my current one when conscious.

Again, I fully accept that unconscious scenarios are not ideal, and could lead to bad outcomes. But they do happen, they are survivable (with a little luck), otherwise AADs wouldn't help much.

To what degree can we help our chances, however, by a size larger reserve? Is the delta between a size so small that it doesn't much matter? Or are we doubling our chances? I suspect the truth is somewhere in the middle, but we really don't have much to go on.

[JerryBaumchen 1,046]

Hi shade,

Quote

kentic energy is the primary factor we have influence while unconscious: the size of our reserve.

I would argue that the amount of kinetic energy is not directly related to the size of the canopy.

From the discussion on this thread, we know that not all reserve canopies of the same size & wing loading fly at the same speed; ergo, faster with same mass ( loading ) -> greater kinetic energy.

Jerry Baumchen

[Hunterbeav 0]

I AGREE WITH HOWARD JOHNSON AGREEING WITH GABBY JOHNSON!!

[keithbar 1]

Does anyone make a zp top skin the rest low bulk reserve.? Seems to be a good compromise

i have on occasion been accused of pulling low . My response. Naw I wasn't low I'm just such a big guy I look closer than I really am .

[gowlerk 1,903]

keithbar

Does anyone make a zp top skin the rest low bulk reserve.? Seems to be a good compromise

No. And if someone did and you bought one your rigger would probably send you away. Precision made a Raven with a zp topskin for a little while. It was called the dash MZ. Very had to pack it neatly and very hard to make it small. There is not really any advantage either. Reserves don't get used enough for the material to become porous.