Aircraft recovery chute?

[Fuppylodders 0]

Hi guys, Im an employed aeronautical engineering apprentice attending college. I was given a project which involves me finding a problem, and then solving it.
Well, after nearly choosing 2 very simple ones, I ended up choosing probably one of my most difficult problems so far... An aircraft with a terminal fault (ie: it is definitely coming down to earth to crash!)

So, I have done research as much as I can, but without being able to talk to someone in the know about it, my head is starting to get into swirls of confusion and 'random information overload'. Don't get me wrong, I'm not stupid (well, sometimes make a fool of myself :P) but going from knowing absolutely nothing about parachutes to managing to do a report on having a suitable one fitted into an aircraft is no easy thing!

What I have learned is that currently, there are already light aircraft with round canopy parachutes fitted as recovery systems and that they do actually work. So, I'm aiming bigger. I was looking at Boeing 747 type of bigger, but that is FAR beyond my learning capabilities as well as information available that allows me to progress at any sort of level with regards to 747 internal structure design.

So, I've scaled it down to a Learjet 85.
With using ram air type canopy (potentially offset-doubled up such as like a slotted fowler flap formation on commercial aircraft, the upper flap regenerating the airflow faster helping the lower flaps airflow to give even more lift).

I know that Nylon is a material that is largely used, having ripstop capability, and that there are various porosities available. I know that there are other materials such as:
Silk
Cotton
Canvas
Rayon
Nylon
Teflon
Terylene
Nomex
F-111
Kevlar
Spectra
Vectran
Zylon
ZPX

I know a little about each, but with regards to which has zero porosity AND ripstop capabilities while being high in strength, low in weight and packing volume is evading me. As well as what materials are used for the suspension lines, what circumstances the above mentioned materials would be used over others... how the canopies are cross braced exactly...
There are more questions but at the moment, these are the more important ones.

Any help you guys could give me would be hugely appreciated as 'internet search and learning' is getting me to a point where I'm slowing down and getting too deep with questions where I can't really find exact answers for without having more questions to clarify things... if you understand what I mean?

Kind regards,
Sam

PS. Another hugely important question: I know there is a formula available which allows one to find out the surface area required to make a round canopy for a given weight, but I can not find a formula to give the area/size of a ram air type canopy. Such frustration at this!

[mrubin 0]

Why would you want to use a ram air canopy instead of a round? I think that a round would be much better suited to something like this.

Have you researched spin recovery parachutes? I know those are sometimes used in aircraft testing. It might not be exactly what you are looking for, but it might be a good place to get started.

"I fly because it releases my mind from the tyranny of petty things." - Antoine de Saint-Exupery

[riggerrob 643]

Oh boy!
You certainly have too many questions for a young man.

First of all, Ballistic Recovery Systems are widely available for small (less than 3,000 pounds gross weight), slow (less than 20 knots). The leading American manufacturer is Ballistic Recovery Systems in the Northern States.
A Russian company makes a similar system for European-built Light Sport Aircraft (less than 1,350 pound seaplanes).
No on has tried a BRS with a ram-air parachute because of the difficulty of steering the parachute. To steer a ram-air parachute that large, you need electric servo motors (winches) pulling the steering lines (tied to the rear corners of the parachute).
Huge ram-air parachutes have been built for something like 30 years, but they are mainly used by drug smugglers (er ... secretive military customers). They normally incorporate GPS and proprietory software to steer them towards their targets.

[riggerrob 643]

A classic example of too much internet research resulting in too shallow a survey, with far more data points than one human can absorb.

A good first step would be to narrow your survey to materials. A narrowed materials search will quickly reveal that nylon is by far the most popular fabric for parachute canopies.
Nylon is the preferred canopy fabric because it has a great strength to weight ratio and stretches a little to absorb opening shock.
We also have 80 years experience sewing parachute nylon together, so the manufacturing technology is "mature."

It is usually some sort of symmetrical ripstop weave. Thickness of canopy fabric varies widely, but is primarily determined by speed of opening shock.
Opening shock is determined by a dozen other variables, but - by far - the most important variable is the speed of the load (in this case a complete airliner) just before you pull the handle to deploy the parachute. Opening shock increases with the SQUARE of the airspeed.

[mark 107]

Fuppylodders

I can not find a formula to give the area/size of a ram air type canopy.

Max gross take-off weight for a Lear 85 is 33,500. You're looking at something like Airborne Systems' GigaFly. The GigaFly is 10,400 ft^2, intended for cargo 15K to 42K.

Airborne Systems doesn't list the pack volume or weight for the GigaFly. My guess, based on experience with skydiving canopies, would be 80-160 ft^3 and 500-1500 pounds. Useful load (payload and fuel) on a Lear 85 is around 4000, which means such a parachute system would reduce the useful load by a substantial amount.

And unfortunately, the GigaFly is rated only to 25,000 feet, which means most of the time a Lear 85 would be operating outside the canopy's limits. It is not an easy thing to design a canopy that opens well enough at both low and high altitudes, and at the speed ranges the aircraft might encounter.

Mark

[RiggerLee 63]

Man, I'm not even sure how to start to respond. How bout this, I'll start here....

747?

Would some one please insert one of those smilely faces rolling on his back laughing. I don't know how to do that.
place it here...

\/

/\

A lear jet? Ok, that's at least theoretically doable. It's a little over 30,000 lb's and things in that size range have actually been done with ram air canopies so it's not completely idiotic. But to get some thing that you can actually land under... We're getting big. And heavy. And did I say big? although it's been done we're talking more in the range of stunt/proof of concept. No one regularly uses things of that size in operation. Speaking as some one with a back ground in aerospace engineering. I'm too lazy to type them but I'm sure I can list at least a thousand things that I'd rather do on a plane if I had that kind of weight and space available. Systems with rounds have been installed in LIGHT planes. And they have actually worked. but honestly they were installed because they were fundamentally flawed designs, generally experimentals that they were trying to certify, which could not pass one or more of the requirements, like stall speed...

And speed. You'd have to get really creative to open one of those things behind an out of control lear jet.

I hate to say this but my advice is to ditch the parachute and spend that weight building a better plane that wont crash.

Lee

Lee
lee@velocitysportswear.com
www.velocitysportswear.com

[Boogers 0]

How much do those shuttle booster rockets weigh, that are lowered by a trio of round parachutes?

[mark 107]

Boogers

How much do those shuttle booster rockets weigh, that are lowered by a trio of round parachutes?

About 200,000 pounds empty.

Mark

[Sincy78 1]

The SRB's weigh about 195,000 lbs each at recovery. Each main parachute weighs 2000 lbs and there are three of them. The kicker is they impact the ocean at about 80 ft/sec. You need an awful lot less velocity than that for land impact survivability. Doesn't really help the person with the project at hand, but is interesting nonetheless.

[GD64 1]

Thought I would throw out my two cents worth, and it's probably worth less than that. Anyway, older diver here, and private pilot that fly's an old Luscombe tail dragger (VFR only). You mentioned some aircraft are parachute equipped ,but I'm not sure of the deployed to "saved" percentages? But I do know that Cirrus Aircraft's number one pilot with a gazillion hours bought the farm (read report but don't remember details).

As far as materials, I can say that I have 4 or so openings at terminal on Lo-Po round reserves and as good as they felt......to quote an old military Sarge "they knocked your dick in the dirt". So the attachment point to aircraft would probably be somewhere around the wing spar/ fuselage area regarding strength as well being close to C & G specs? But it would be helpful if you could have the attachment points as part of a internal protective glove of sorts to spread the opening shock. But still, could the passengers survive the G-force? I suspect the seats and safety harness would be another engineering feat. The recent Indy Car crash that forced the retirement of Dario Franchitti had G-forces that exceeded 200 G's. Although he survived, and was extremely fit, he was messed up. Dan Weldon unfortunately went in to the catch fence a couple of years ago and did not survive. G-forces I believe were around 280 and he was upside down.

The ram air concept is an interesting one. I do know from my experience in a country far far away years ago, that amazing amount of weight could be dropped by round parachutes.....howitzers and ammo sometimes with multiple chutes on same gun or ammo pallet. Don't know how that would work out with ram?

One thing I thought of was deploying multiple chutes in stages. The first could put out a drone chute than deploy around C & G, than follow with tail and or nose area simultaneously but spread out far enough to avoid entanglements.

Another challenge you have is dealing with fire. It happens a lot around aircraft emergencies. Those chutes and there attachment points would have to withstand high heat while aircraft descended under canopy(s) with passengers breathing fire feeding oxygen?

Good luck with your project....it was a lot of fun to think about. I'll watch thread because there are a lot of smart people here.

Thanks

[mjosparky 4]

A ram air would be out of the question for several reasons. But if you look to systems NASA has used in recovery of booster rockets and capusuls you will get an idea of what it would take for a 747.

Sparky

http://en.wikipedia.org/wiki/Space_Shuttle_Solid_Rocket_Booster#Descent_and_recovery

My idea of a fair fight is clubbing baby seals

[theonlyski 8]

Everyone has pointed out the canopy side issues with doing this, but you also have to think about how you'd attach the canopy to the airframe. Trying to haul a Leer under a few canopies is surely going to put some stresses on the airframe that it wasn't designed for.

Believe it or not, airplanes glide even with all the fans shut off. In almost every engine out scenario I have come up with, I'd rather glide than fall at the mercy of a BRS. The ones that I'd rather the BRS are over open water with no land within glide and over dense forest.

I also see absolutely no advantage to a ram air canopy in this situation. Rounds get you to the ground, are very reliable (when equipped with anti-inversion netting) and they won't have too much of an issue being connected via single point. That'll give you the ability to counteract any twisting on the airplane from spinning up and choking off the canopy.

"I may be a dirty pirate hooker...but I'm not about to go stand on the corner." iluvtofly
DPH -7, TDS 578, Muff 5153, SCR 14890
I'm an asshole, and I approve this message

[tsalnukt 1]

What were the other choices?

[Fuppylodders 0]

Hi again, thank you very much for the quick replies!
OK, @mrubin,
Ram air canopy requires less surface area (as far as i know) due to generating a bit of lift compared to the simple round/drag canopy. So there is potential to have a similar sized canopy which could carry a larger load?
I did not know about the spin recovery parachute, an impressive piece of kit!
Although this wouldn't necessarily solve the problem if an aircraft had a catastrophic failure of a control surface or some other situation which would render aerodynamics almost unflyable. But thank you, I can look at this in more depth with regards to my research!

@riggerrob
With regards t using ram air parachute, I don't think the main issue is the steering of it, but the potential damage caused by the forward speed upon impact of the ground... so I have found out
You are right Rob, it is a classic example, but unfortunately I was sort of pushed into choosing this as the subject of my project and so literally had no idea how to proceed and went head first into it
I had found that Nylon was the most common and preferred use, but I have also seen other materials available. I didn't know which of these are the newest and possibly have potential to overtake Nylon as 'the new best thing to use for material'.
I have heard that the ripstop is created by the type of weave it has which hugely prevents rips occurring, however I did not know if this was able to be incorporated into other materials as I know they all have their own fibre properties, but then again, there should be some it can be incorporated into quite easily if it is just the weave itself that gives this effect?

The opening shock increasing is something I've been pondering how to reduce upon something traveling roughly somewhere between 350-500 mph (asking a hell of a lot) but I might have to reduce the plane type to a turbo prop small passenger plane upon further research. I was told that it would make a good project if I ended up having to work my way down the sizes of aircraft until I found one that had potential for it to be realistically possible.

@Mark
You do raise a good point, about designing a parachute that can operate within low/high speeds/altitude. I have been recommended to find a particular type of 'situation' and stick with that, as there are soo many variables in which the aircraft could 'fail' at, that it is almost impossible to design one safety device to cover all possibilities.
It appears you do know your stuff with regards to weights/sizes of chutes and loadings, would you happen to know the formula required to work out the surface area required? Or perhaps where I can find it?
I can honestly say I have tried and tried and I just can't find anything that helps with regards to this that it worries me I might have to leave this part out of the design process, which in all honesty, should be included with something like this.
This most certainly is stretching me, but I am determined to get some sort of results!

*Edit*
Sorry I haven't replied to everyone, I wrote this a while ago and seems I forgot to press the post button while leaving the window open in the background

[Sincy78 1]

Download Steve Lingard's Guide Here
http://www.aerodecelerator.org/DOC_ARCHIVE.htm#Ram-Air_Parachute_Design

[Fuppylodders 0]

Really not worth mentioning... but to humour you:
1) Losing pens; how to make them easily found once lost (situation sort of like where you know you had it 5 minutes ago and can't remember for the life of you where it has gone/been left)

2) Marking out a straight line accurately along something that is typically longer than 1 meter such as the edge of a door, length of plasterboard etc in one go without having to mark individual segments then join the dots.

3) Preventing spillages on the floor/toilet seat when people's 'aim' isn't good/can't be bothered/too drunk to care.

So, as I said, not really worth mentioning

@mjosparky
With regards to ram air recovery, I don't personally think it is as out of the question as you believe it to be. I can't really say why, as I don't know how much is common knowledge, or how much 'they' privileged me with being told... but progression is being looked at, is what I will say.

@Boogers/Mark/Sincy
I had looked at the SRB recovery system early on but pretty much instantly dismissed it due to the size of them/weight they would take up themselves. But yes, still very interesting!

@GD64
I had thought a similar thing, multiple chutes, then multiple chutes in stages (both regarding the 747 initial idea stage), as first off, the 747 is much larger so could 'potentially' accommodate multiple chutes. (I actually read somewhere during my research that it had been proposed as an idea by some company of the possibility of multiple chutes in a 747 that the pilot could actually control, but I believe they probably fell onto the exact issues that seem glaringly obvious, even to me) So, starting with a rear chute similar to the spin recovery to stabilise it, then one to come from near the front to stabilise the aircraft horizontally, then 1 from each wing to slow the descent down even more. Problem with this is I think (assuming there was any potential possibility at all) that it might take too long for the entire system to reach its final descent stage that it probably just wouldn't work in time (but then situational occurrence...) However, trying to fit something similar to this, in a Learjet, then requires me to need information on the internal structure design in order to ascertain where the mounting points could be, how many mounting points would be needed, then working out a system of chutes that could have potential, working out the size drogue chute required (perhaps even a ribbon chute instead maybe?)
I get lost in suddenly needing so much information that half I can't get due to probably needing access to the aircraft's publications and the other half needing some sort of testing that I can't physically carry out.
But then I need to keep pushing myself on this to get some sort of result. Even if it turns out to be a 'it just isn't possible from the information I have gathered', but that information needs to be pretty definite with something to back it up rather than me simply saying 'so yeah, it's just not going to work.'

I don't know... The stuff I'm putting myself through to become an engineer! I know it'll be worth it!

*edit* Thank you Sincy, will do.

(I'm in the UK, and it is now 01:40, time to get some rest... this project hurts my brain

[mjosparky 4]

Quote

The opening shock increasing is something I've been pondering how to reduce upon something traveling roughly somewhere between 350-500 mph (asking a hell of a lot)

This can be accomplished with the use of drogue chutes and reefing systems.

Quote

You do raise a good point, about designing a parachute that can operate within low/high speeds/altitude.

The latest ejection seats are designed to operate from zero/zero up to 600 KEAS. It all depends on how complicated you want to go.

Sparky

This might help with ram airs.

http://www.aerodecelerator.org/PDF/Lingard.pdf

My idea of a fair fight is clubbing baby seals

[RiggerLee 63]

Have you looked at the "recovery systems design guide"? Knacky is one of the authors. I think Sherman might have it on his Jump Shack web site.

Here...

http://www.jumpshack.com/default.asp?CategoryID=DOWNLOAD

It's listed about 3/4 of the way down. I'm not sure if the link works. I started to check but it's a long document, think book. It's very old school. It will give all the information you would ever like to know about how to do heavy loads with rounds. It's got data on designs that would be workable for intermediate canopies, think ribbon style drogue chute designs. but even that would have to be pretty large. If you are going to open a large ram air you're going to want to get the speed down to some thing reasonable. There is a lot of interest in large ram airs for precision cargo. 30,000 lb is very much at the limit of what has been done. The landing can actually be relatively soft, lower decent rate then a equivalent weight round and the ability to fly and steer them is off the shelf technology. What it might be less forgiving of is off nominal deployments. The drogue would have to be big enough to stabilize the situation before I would try to deploy a ram air. As far as structural issues go... Think about the air frame it self. All the loads are already supported by the section at the wing root. It's not inconceivable that you could attach structurally to the plane there. As an example, a twin otter, all the load is carried by this one big frame at the wing root. I know cause I've helped to replace one that was cracked. That's an example of a slightly lighter air craft, 13,000 lb or so that you might be able to develop a workable system for. Between the weights and the speeds it's a way easier problem. And it's used in applications, bush flying in Canada, where an emergency landing might not be an option.

Just for fun here's a 1200 sq. foot ram are landing a rocket of a little over 1000 lbs.

http://www.youtube.com/watch?v=UV7zL07Tof8

That actually wasn't our softest landing. The canopy was still in the process of flaring. It was like a 2 g landing and that was straight onto the air frame No landing gear. That canopy could actually carry twice that weight, about 2,000 lb. For the record that canopy weighs about 64 lb. Ram airs actually get more efficient as they get bigger where as rounds actually lose efficiency. So the idea of doing a larger BRS for a mid range aircraft, Otter, is not beyond the realm of possibility. Rounds would be the simpler and more reliable choice particularly with people on board. But I say again who wants to ha

But who really wants to carry that weight around with them every where they fly? I don't know a pilot that wouldn't rather have 300 lb. of fuel on board then a recovery system.

Lee

Lee
lee@velocitysportswear.com
www.velocitysportswear.com

[NovaTTT 2]

Perhaps you're better off writing a negative report: Why it is impracticle and/or impossible with current technology to utilize a BRS on aircraft that exceed xk#.

It's that or some kick-ass sci-fi!

"Even in a world where perfection is unattainable, there's still a difference between excellence and mediocrity." Gary73

[hobbitman 0]

Young aerospace engineer here myself.

A couple thoughts:

1) Your best bet would probably be rounds given that you would be unable to steer/control a ram air canopy used in this way without some complicated and heavy system.

2) On the note of rounds, probably something like the 3 parachute system they have used in the space program for landing rovers and capsules for a long time would be a decent place to do some research if you havent already

3) This system strikes me as something that would really just be for saving the airframe as the shock of opening in an passenger jet which is flying out of control would likely kill or cripple most or all of the passengers either from the direct shock of deceleration or from being thrown around during the jerk caused by the opening.

4) As someone previously mentioned, the weight of a system like this almost certainly makes it not worth it, if you are going to spend that weight, better to spend it elsewhere.

[RiggerLee 63]

One thing that people keep bringing up is steerage. That's actually the one thing which is not a problem. That's the least challenging issue in all of this. Waymore builds systems every day for remote autonomous steering of ram airs for cargo operations. All those precision air drops with ram airs in the sand box. That's Waymore they have all the contracts. They build the control units for all of that.

As an example they built the autonomous guidance unit for all of our air frames. On a return from 300,000 ft. they averaged 50 meters accuracy on all of their landing. When ever I gave them an open canopy they landed right in font of the crowd. Better then most jumpers.

Lee

Lee
lee@velocitysportswear.com
www.velocitysportswear.com

[dwhenline 0]

I own a Cirrus aircraft which has a recovery parachute which has worked really well. It is rated currently for 3600 pounds and is a round canopy. The canopy is attached to the airframe with four risers, bring the airplane essentially straight down. The survivability is well documented and much better than trying to "glide" the airplane onto an open field or road.
why not just call BRS and ask them some of these questions. I promise you, they all ready have the answers.
don

[RiggerLee 63]

BRS is undoubtedly the leader in this. Mainly because there are not many people in the game. I've talked to them. I've tried to deal with them on some fairly big dollar projects. I got to tell you it was a little weird. I made a really concerted effort to work with them and in the end the conclusion that I came to is that they are not too bright. I was kind of shocked because they really do have a good product. There's no doubt about that. But the people there are... stupid. Don't know how else to describe it. I can tell you this they're not riggers. I've got no clue how this came about. I think, and this is just conjecture, what happened is that a guy came up with an idea. He wasn't a rigger he just had this idea for a recovery system. He wrote a business plan, a good one, and went forwards with it as a business venture. He must have contracted the design work. He must have found some one that could run the production shop. And he could sell it. It's so totally backwards form the skydiving industry that I can't even relate to it but it's been successful. What I can tell you is that the people there know almost nothing about parachutes. And I didn't just talk to a salesman I tried hard to find some one there to answer my questions. They came at this from the airplane end and the business end. And oddly, though their business is all about parachutes no one there knows any thing about them. Even their own. And I am not exaggerating, And I am qualified to judge.

In short don't hold your breath getting any meaningful information out of them.

Lee

Lee
lee@velocitysportswear.com
www.velocitysportswear.com

[riggerrob 643]

Sounds like BRS fired the original inventor.

Incidentally, the concept of saving the entire airframe is not new. Many people proposed the concept back during the 1930s, but we had to wait until hang-gliders proved the concept at light weights and very low airspeeds, before we could "speed up" the technology to save entire 3600 pound airplanes.

Remember that opening shock increases with the square of the velocity ... at the start of deployment.

[riggerrob 643]

" ... 3) This system strikes me as something that would really just be for saving the airframe as the shock of opening in an passenger jet which is flying out of control would likely kill or cripple most or all of the passengers either from the direct shock of deceleration or from being thrown around during the jerk caused by the opening. ..."

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

Au contraire ...

You still need a reefing system (slider or ropes) to reduce opening shock to keep the parachute structurally intact. You need a reefing system to reduce opening shock below the value that will rip risers off the airframe.
Once you add the complexity of a reefing system, it is comparatively easy to increase its effectiveness to soften opening shock to low enough levels that the passengers remain uninjured.

IOW you will never be able to built a light-weight system that wil only save the airframe, because a parachute that strong will need to be so much stronger that it will far exceed the weight of a reefed parachute/