Cirrus descent rate under parachute less with wind?

[suninmyeyes]

In the youtube video below Paul Bertorelli states at 4.07 that a Cirrus with parachute deployed descends at a rate of 1700 fpm but will have a lower rate of descent if there is a wind.

https://youtu.be/zT58pzY41wA

Can someone explain that? To me the aircraft has no form of control with the parachute deployed as the indicated airspeed will be zero in a constant wind however strong and there is no way of harnessing the wind strength to form lift.

[Groundloop]

The aircraft and parachute will not move at the same speed as the wind because of drag. Therefore there will a small residual airflow over the wings which may generate a LITTLE lift.

[suninmyeyes]

The aircraft and parachute will not move at the same speed as the wind because of drag. Therefore there will a small residual airflow over the wings which may generate a LITTLE lift.

If they move at different speeds the distance between them would have to increase😀 So any small transient changes in speed between them due to drag or pendulum effect would have to cancel out.

[Maoraigh1]

Drag is the reason the plane and parachute will very quickly stabilise at the wind speed.
Only severe windshear would have the plane and parachute at different speeds while still attached to one another, a situation which might occur near the ground.
However it would be possible for them to gain height in strong updrafts.

[The Ancient Geek]

In still air the parachute will be directly above the aircraft and both will go straight down.
In a wind the parachute will above and ahead of the aircraft and both will decend at an angle. There are 2 vectors, horizontal and vertical, the aircraft will take longer to reach the ground, simple trigonometry.

[megan]

Having jumped round canopies in high winds I can tell you that your position hanging in the harness does not change relative to the canopy ie you still hang directly below the canopy apex, nor does the rate of descent change with wind, why Paul states what he does I have no idea. One advantage landing with wind is that the horizontal impetus throws you into a landing roll, rather than coming straight down and landing like a bag of spuds. There are wind limits of course, have memories of a barb wire fence arresting horizontal passage across across a very wet and muddy wheat field. Good training for a to be fixed wing naval aviator.

[PaulisHome]

In still air the parachute will be directly above the aircraft and both will go straight down.
In a wind the parachute will above and ahead of the aircraft and both will decend at an angle. There are 2 vectors, horizontal and vertical, the aircraft will take longer to reach the ground, simple trigonometry.

It may be simple trigonometry, but you've done it wrong.

If the wind is constant all the way down, it will make no difference to the descent rate (and probably very little even if the wind does vary). The aircraft will take the same time to reach the ground compared with there being no wind.

If there is wind, then the overall velocity of the aircraft (the sum of the descent and wind vectors) will be higher than with no wind - but only as measured by an observer stationary relative to the ground. For an observer say in a balloon, drifting with the wind, there will be no difference.

The claim in the original video is incorrect.

Paul

[VariablePitchP]

In still air the parachute will be directly above the aircraft and both will go straight down.
In a wind the parachute will above and ahead of the aircraft and both will decend at an angle. There are 2 vectors, horizontal and vertical, the aircraft will take longer to reach the ground, simple trigonometry.

Nope, you’re getting ground and wind speed confused. They are totally, totally, totally unrelated. You could be in a 50,000kts wind, if the air is stable then you’d be hanging quite happily, quite vertically, everything pointing to the centre of the Earth. It just so happens to be spinning below at a great speed.

[atakacs]

Irrespective of the debate above I find 1700 fpm as rather uncomfortable when hitting solid ground...
​​

[340drvr]

Having jumped round canopies in high winds I can tell you that your position hanging in the harness does not change relative to the canopy ie you still hang directly below the canopy apex, nor does the rate of descent change with wind, why Paul states what he does I have no idea. One advantage landing with wind is that the horizontal impetus throws you into a landing roll, rather than coming straight down and landing like a bag of spuds. There are wind limits of course, have memories of a barb wire fence arresting horizontal passage across across a very wet and muddy wheat field. Good training for a to be fixed wing naval aviator.
This is the only explanation. The video statement is wrong, and misleading.

[Dave Gittins]

Hmmm as my normal descent on finals would be about 400 ft/min then 1,700 ft/ min sounds a lot.

I make it (1700 / 60) x (60 / 88) = 19.3 mph. suppose its a good bit slower than without the parachute but it still seems a tad quick to me. That's why I've never had the urge to leap out of a serviceable aeroplane.

[Pilot DAR]

I find 1700 fpm as rather uncomfortable when hitting solid ground...

Me too!

That's why I've never had the urge to leap out of a serviceable aeroplane.

Me either! Though I flew jumpers for years. The happy difference for the sport parachutist, as opposed to the Cirrus passenger, is that the sport parachutist has the ability to flare the parachute for a softer landing, and regularly impressed me with well timed flares, and feather soft touchdowns. If I understand correctly, the returning Russian space vehicles use last moment rockets to arrest the descent rate - okay, I guess it works, but the civil aviation standards would never allow certifying such a system! The Cirrus does not know when it's about to hit.

A descent rate of 1700 fpm exceeds some helicopter autorotation rates I have flow, and they're a little alarming. When I changed the prop from two to three blade on my flying boat, the power off, full fine propeller pitch glide went from 800 fpm, to 1300 fpm. This was an alarming rate in this plane, and I really think that a flare to a safe landing from even 1300 fpm would be challenging. (I found that selecting full coarse propeller greatly improved the glide).

a 19 mph stop is painful. Cirrus gets credit for energy absorbent seats, which I'm sure really help, but it's still a hard stop. In times past, when car seatbelt use was being encouraged, there was a road safety car simulator, which subjected the occupant to a 5 mph crash force, even that was a jerk.

I can't imagine a Cirrus parachute descent rate low enough, combined with all other factors, to make me comfortable with the system. But that's my personal opinion, I respect that others feel differently, and that is entirely their privilege too...

[Pugilistic Animus]

Sometimes that Cirrus pushes pilots to do stupid things because of the chute...they should read this thread. It's a nice plane but it's still a limited SE

[draglift]

If I had an engine failure in a Cirrus and could not reach an airfield I would rather glide down and land in a suitable field. Is that what is recommended or do they suggest pulling the parachute handle?

I remember seeing at an airshow a light sport aircraft with a ballistic parachute. It was designed to come down right wing low under the 'chute so the right wing would hit first and concertina thus absorbing energy before it would straighten up and land on the gear. Very clever.

[megan]

1,700 ft/ min sounds a lotJust for comparison sake the maximum rate of descent permitted in my jumping days was 1,260 ft/min (21 ft/sec) with a 170 pound individual. The main we used was a 28 ft diameter (same as used in the F-86 at the time, same container as well, descent rate 19.8 ft/sec with 235 pound load) with a 24 ft diameter chest mounted reserve. Big guys would use a 35 ft diameter main and 28 ft reserve.

[pilotmike]

In still air the parachute will be directly above the aircraft and both will go straight down.
In a wind the parachute will above and ahead of the aircraft and both will decend at an angle. There are 2 vectors, horizontal and vertical, the aircraft will take longer to reach the ground, simple trigonometry.
This is completely wrong. The load on the parachute falls at the same rate regardless of any wind. It is a pity that (wrong) opinions are dressed up as statements of fact - when they are not. Dressing it up with irrelevant maths, vectors, trigonometry etc doesn't make it right.

[cats_five]

In still air the parachute will be directly above the aircraft and both will go straight down.
In a wind the parachute will above and ahead of the aircraft and both will decend at an angle. There are 2 vectors, horizontal and vertical, the aircraft will take longer to reach the ground, simple trigonometry.

No it won't. The vertical component is the same. However the wind ADDS a horizonal component.

[Pilot DAR]

Okay, I don't know which answer is right, with a wind, the cirrus has more time before arriving to earth, or not. It's a worthwhile discussion and thinking point while we're not flying, but it's not worth rudeness, nor emotion, so reign it in! Everyone is entitled to their opinion, politely expressed, someone's opinion is probably correct. It won't hurt anyone for a trigonometry review, which is why I have not deleted a couple of posts, nor locked the thread. The principles here are worth discussion, but they're not worth an argument.

So, someone(s) who knows a lot more about trigonometry than I, please feel welcomed to post some math with lines at angles, and the rest of us will learn something we will hopefully never use!

You moderator, Pilot DAR....

[cats_five]

Okay, I don't know which answer is right, with a wind, the cirrus has more time before arriving to earth, or not. It's a worthwhile discussion and thinking point while we're not flying, but it's not worth rudeness, nor emotion, so reign it in! Everyone is entitled to their opinion, politely expressed, someone's opinion is probably correct. It won't hurt anyone for a trigonometry review, which is why I have not deleted a couple of posts, nor locked the thread. The principles here are worth discussion, but they're not worth an argument.

So, someone(s) who knows a lot more about trigonometry than I, please feel welcomed to post some math with lines at angles, and the rest of us will learn something we will hopefully never use!

You moderator, Pilot DAR....

In my view it will only take longer if there is some sort of uplift. And, of course, it could encounter sink. As any glider pilot knows, both of these are possible on an absolutely still day.

[oggers]

Okay then. As already posted by some, any wind velocity will not reduce the descent rate as incorrectly stated in the video. Descent rate will not change. However impact velocity will increase. Notwithstanding aforementioned vertical wind currents obviously. Here is the relevent equation and trig:
https://cimg3.ibsrv.net/gimg/pprune.org-vbulletin/619x695/brs_triangle_6faf89d94ebc12c13d324a038ef53a1a67a9252b.png

...so in a sense the video has it the wrong way around because wind drift is going to make the impact worse. QED

[n5296s]

I really think that a flare to a safe landing from even 1300 fpm would be challenging
The Pitts I used to fly regularly comes down at about 2000 fpm power off, which is how I was taught to land it. Yes, it is. You have about a 0.25 second window to flare if you don't want either to hit the ground very hard, or flare too high, stall, and hit the ground very hard. The poor instructor, who has to give the student time to make mistakes, has maybe 0.1S to decide whether to intervene. My instructor, who had been a U2 pilot and knows a thing or two about planes which are difficult to land, says that of all the things in instructing, the one he hates the most is teaching people to land the Pitts. (The Extra 300, by contrast, is a complete pussycat, and not much harder to land than a Citabria).

One advantage of having done it is that it makes uatos seem pretty tame!

[Fl1ingfrog]

oggers, where does the increase in force come from? Surely your triangle of forces shows a decrease in the vertical impact and therefore must increase the horizontal force impact: i.e. the dry stone wall. Following the landing the drag from the surface will also form a part which will then absorb the energy further before eventually impacting with the wall, when all energy is then dissipated and comes to rest.

[cats_five]

In still air the parachute will be directly above the aircraft and both will go straight down.
In a wind the parachute will above and ahead of the aircraft and both will decend at an angle. There are 2 vectors, horizontal and vertical, the aircraft will take longer to reach the ground, simple trigonometry.

It will only take longer if the vertical vector decreases, which it doesn't

[oggers]

oggers, where does the increase in force come from? Surely your triangle of forces shows a decrease in the vertical impact and therefore must increase the horizontal force impact: i.e. the dry stone wall. Following the landing the drag from the surface will also form a part which will then absorb the energy further before eventually impacting with the wall, when all energy is then dissipated and comes to rest.

Hi, it is a triangle of velocities not forces. The video states that the vertical speed would be reduced by drifiting in the wind - which it won't. That is what the diagram addresses, not impact forces per se. The important thing is that the vertical speed is not reduced by drifiting with the wind. It follows that the vertical acceleration experienced on hitting the ground is not reduced either.

----------
For anyone tempted to believe the proposition that the vertical speed of the aircraft/canopy can be reduced by drifting with the wind, simply ask yourself at what wind speed you think the whole contraption will begin to climb back up to altitude.

[Fl1ingfrog]

... because wind drift is going to make the impact worse. QED

Megan I made my point because of your statement above. The speed over the ground is not really the issue,, but the force on arrival applied to terra firma is of utmost importance is you wish to survive in one piece. Megan has pointed out the forward speed assists with the landing.

To my knowledge the pilot has no control once the aircraft chute is deployed. This has always struck me as a problem. When gliding you do have control if not a lot of choices as to where you will land but you will have more than the aircraft chute offers.

[The Ancient Geek]

The chute is for use when the aircraft is uncontrollable, probably due to structural issues.
Some have been deployed when the pilot has managed to get into IMC, this should not have happened to begin with but the chute is a better option than losing control or flying into a hill.

[India Four Two]

The landing gear and the seats in the Cirrus are designed to dissipate some of the energy in a parachute landing

[Jim59]

"For anyone tempted to believe the proposition that the vertical speed of the aircraft/canopy can be reduced by drifting with the wind, simply ask yourself at what wind speed you think the whole contraption will begin to climb back up to altitude."

Your comment assumes a flat earth.

[RatherBeFlying]

Horizontal velocity allows friction with the ground to dissipate kinetic energy at a gentler rate than happens with a completely vertical impact. Much depends on ground, vegetation and obstacle (rock, potholes, agricultural equipment, stone walls...) characteristics.

In the best case wheels contact an even firm surface with a vertical component that the airframe can tolerate.

[Maoraigh1]

"Horizontal velocity allows friction with the ground to dissipate kinetic energy at a gentler rate than happens with a completely vertical impact"
Friction with ground will dissipate kinetic energy parallel to the ground.
Kinetic energy perpendicular to the ground will be dissipated by deformation of the object and the ground. The latter will be over a very short time interval.

[Russell Gulch]

Pull the 'chute. Now the pilot has breathed a very heavy sigh of relief, so reducing weight. He has also shat his pants, so further reducing the all-up weight of the aircraft.

That's why they glide a longer distance. You may note I mentioned a male pilot. Now when a female pilot flies a Cirrus, there is no need for a parachute....the engine daren't fail.

[suninmyeyes]

[QUOTE=RatherBeFlying;10738439]Horizontal velocity allows friction with the ground to dissipate kinetic energy at a gentler rate than happens with a completely vertical impact.QUOTE]

Ok I agree that if a Cirrus is coming down under a parachute with a 20 knot wind it would reduce the impact force on the occupants if it could go along the ground in the same direction as the wind for a bit after impact rather than coming to an immediate stop.

However if it is coming down with no wind at the same vertical rate surely the force experienced on touchdown by the occupants in a vertical descent would be less because you have no additional sideways kinetic energy to dissipate?

[PDR1]

"Horizontal velocity allows friction with the ground to dissipate kinetic energy at a gentler rate than happens with a completely vertical impact"
Friction with ground will dissipate kinetic energy parallel to the ground.
Kinetic energy perpendicular to the ground will be dissipated by deformation of the object and the ground. The latter will be over a very short time interval.

Energy is a scalar, not a vector - it has no direction. I believe you are confusing it with momentum.

PDR

[Runaway Gun]

Many of these comments scare me. Are you sure you all passed High School science?

[cats_five]

Pull the 'chute. Now the pilot has breathed a very heavy sigh of relief, so reducing weight. He has also shat his pants, so further reducing the all-up weight of the aircraft.

Snip

Did he throw the pants out the window?

[PDR1]

Many of these comments scare me. Are you sure you all passed High School science?

This thread is far from unique in that respect. This repeated inability to understand the difference between velocity, momentum and energy is disappointing.

PDR

[RatherBeFlying]

"Horizontal velocity allows friction with the ground to dissipate kinetic energy at a gentler rate than happens with a completely vertical impact"
Friction with ground will dissipate kinetic energy parallel to the ground.
Kinetic energy perpendicular to the ground will be dissipated by deformation of the object and the ground. The latter will be over a very short time interval.
You may be surprised by how short a landing can be without damage. I once landed a glider on a sandy loam fallow field and was astonished by the sudden stop. Over some two fuselage lengths the gear dug a steadily deepening trench until the glider was sitting on the gear doors.

Admittedly, it cost me under $5 to replace a couple gear door hinges.

[Maoraigh1]

Apologies for imprecise words. What I'm try to say is that the impact force from descent into the ground will not be reduced by movement parallel to the ground as far as the descending aircraft is concerned.
​​​​​​Movement parallel to the ground will spread the force over a longer piece of ground. A shallower trench than the hole would be if no parachute.

[PaulisHome]

[QUOTE=RatherBeFlying;10738439]Horizontal velocity allows friction with the ground to dissipate kinetic energy at a gentler rate than happens with a completely vertical impact.QUOTE]

Ok I agree that if a Cirrus is coming down under a parachute with a 20 knot wind it would reduce the impact force on the occupants if it could go along the ground in the same direction as the wind for a bit after impact rather than coming to an immediate stop.

However if it is coming down with no wind at the same vertical rate surely the force experienced on touchdown by the occupants in a vertical descent would be less because you have no additional sideways kinetic energy to dissipate?

Your first statement is wrong, the second correct.

If there's a wind, we can take the view that there are two impact forces - a vertical one (same as if there was no wind) and a horizontal one where the plane needs to decelerate from the wind speed to rest relative to the ground.

So you don't reduce the impact force - you increase it. As you say in your second statement.

Paul

[Fl1ingfrog]

"So you don't reduce the impact force - you increase it. As you say in your second statement."

This is of course is true but how the impact is absorbed is important.

I attended a short course at Martin Baker many years ago. From memory they were giving a total ejection force of up to 15 G. Not many pilots survived ejection without serious injury to the spine during the early years of development. They had eventually discovered that it is not only the total G that is encountered (to a limit) but the rate it is sustained was crucial. They eventually incorporated a clockwork mechanism within the seat that, through series of stages, delayed the total G over approximately 2-3 seconds maybe less (I'm working from memory). This was from pulling the handle through to the chute being deployed. This very short period was sufficient to avoid serious injury.

[TheOddOne]

I've a lot of respect for Paul Bertorelli's reporting. I like his style and the way he appears to dig into the statistics to present a reasoned argument. In this case, he's asking if the BRS makes the Cirrus safer than a non-BRS equipped piston single.
I've enjoyed reading the various posts as above. It reminds me of the old chestnut about losing airspeed making a turn when the wind is blowing.
It would be a pity if the reason for his article on the subject was lost in a side-debate.

TOO

[PDR1]

"So you don't reduce the impact force - you increase it. As you say in your second statement."

This is of course is true but how the impact is absorbed is important.


This is true, but lateral velocity doesn't change how the vertical force of impact is experienced. The only thing that affects that is the vertical elasticity of the collision - how rapidly the vertical velocity is reduced. Being dragged sideways won't change that. Really chaps - this isn't rocket surgery, it's less than A-level physics or maths. It really is depressing how limited the grasp of basic mechanics can be...

The parachute analogy misunderstands what's going on. The reason why a parachutist is less likely to be injured when there's a wind is simply that it more or less forces a rolling impact. In flat calm conditions there is a strong tendency to try to absorb the impact with just bent knees because rolling feels unnatural without extensive training.

PDR

[EvaDestruction]

I did not watch the video, and I'm surprised it's 1700FPM. That's more than a helicopter in autorotation pretty much.

But I can imagine that if the plane is properly suspended, any wind blowing might cause the airframe to fly, generating some measure of lift for less weight on the canopy?

I've flown a few Cirrus, but keep thinking about taking it to the ground, land on a road as you do in your Cessna. :cool:

[Vessbot]

But I can imagine that if the plane is properly suspended, any wind blowing might cause the airframe to fly, generating some measure of lift for less weight on the canopy?


That same wind would also be blowing on the canopy the same way, causing it to ultimately move with the wind and have the same lateral airspeed (could be zero, could be some some nonzero speed depending on the canopy design) as if there is no wind.

[PDR1]

As far as I've seen the attachment points of ballistic parachutes are slightly behind the CG - presumably so that on deployment they tend to stabilise the aeroplane in a sensible attitude whilst decelerating. It also means that they will tend to suspend the aeroplane in a slightly nose-down attitude. Therefore if there WAS any wing-lift acting while suspended it will tend to be negative rather than positive.

But that's irrelevant because the steady-state airspeed of an object suspended from this kind or parachute is zero. They are not parafoils and nor do they have the rear vents seen in some round parachutes to give the parachutist a small degree of directional control. So they will behave like balloons - the airspeed will be zero other than the odd gust.

This thread is just verifying Einstein's conjecture on infinity.

PDR

[megan]

In flat calm conditions there is a strong tendency to try to absorb the impact with just bent knees because rolling feels unnatural without extensive trainingJumping a round canopy any attempt to absorb the landing forces by bent knees will result in one outcome for a novice - broken leg/s, it took an experienced person to be able to do a "stand up" as they were called. Judging the time of impact with the ground rush was the issue. The landing roll that was taught was not unnatural and didn't take extensive training, being shown once and a couple of practices was generally sufficient, we did ours jumping off a brick BBQ.

[oggers]

How crude. We were taught the PLF by RAF PTIs in the gym using a platform specially fabricated to be the same height as a brick BBQ.

[draglift]

On a round canopy were you taught to pull on the shroud lines just before touchdown to reduce the rate of descent and impact?

It is a pity you cannot flare the Cirrus when landing under a parachute. Now if the Cirrus had a winch you could start so you could quickly wind up six feet of lines just before touchdown...

[pilotmike]

I did not watch the video, and I'm surprised it's 1700FPM. That's more than a helicopter in autorotation pretty much.

But I can imagine that if the plane is properly suspended, any wind blowing might cause the airframe to fly, generating some measure of lift for less weight on the canopy?

I've flown a few Cirrus, but keep thinking about taking it to the ground, land on a road as you do in your Cessna. :cool:
Oh dear, oh dear!

How on Earth can ANYTHING which is drifting with the wind have any lift generated from any wind 'blowing' over any airframe, when there is NO wind blowing over any airframe? Which bit of drifting with the wind is unclear? Have you ever given a moment's thought to how a hot air ballon gets its lift? It cannot be from any wind - AS THERE IS NO RELATIVE WIND WHEN YOU'RE DRIFTING WITH IT.

Hot air balloons stay up by HOT AIR - and that's all that's keeping this unbelievable thread going.

Can't somebody shoot this thing and put the thread out of its misery, and spare a few people from their embarrassment?

[edit} PS. A bit harsh? Possibly, if the comments had come from a non-aviator, but as they apparently came from someone claiming to be an 'ATP' / Flight Instructor... seriously? Are refunds available? PLEASE read up on basic aerodynamics before trying to do any more teaching. Save their hard-earned, save your blushes.

Oh, and another thing... how can you NOT be "thinking about taking it to the ground" every time you land, claiming as you do that you actually fly these aircraft? How else do you land them? Do you pull the 'chute every time and rely on gravity (and of course a good strong wind!!!!) to do the rest? How many have you written off by not "taking [them] to the ground"? Is this a dream on MS flight sim? It appears its all just a load of hot air.

As for:land on a road as you do in your Cessna
Are you for real? Please don't stray too far from MS Flight Sim! Even the roads now appear to be too dangerous with you around. WTF? Am I the unwitting innocent victim of a bad joke or something? Somebody help us all!

[Jim59]

Since I cannot fly I'll bite...

"How on Earth can ANYTHING which is drifting with the wind have any lift generated from any wind 'blowing' over any airframe, when there is NO wind blowing over any airframe? Which bit of drifting with the wind is unclear? Have you ever given a moment's thought to how a hot air balloon gets its lift? It cannot be from any wind - AS THERE IS NO RELATIVE WIND WHEN YOU'RE DRIFTING WITH IT."[

If it is drifting with the wind at a constant height then the above statement seems to be valid. However we are talking about a descending object. If there is wind present then as the object gets closer to the ground it will pass through a wind gradient where the wind decreases in strength. Due to inertia the descending object will not instantly reduce its ground speed to match the velocity of the now weaker wind - hence there will be an airflow over both 'chute and plane (not necessarily the same airflow since the vertical separation means they are in different parts of the wind gradient).

Now this may seem trivial or frivolous but if one looks up dynamic soaring (or the Coandă effect) it is a real world phenomena exploited by the albatross in particular. The bird has an adaptation to lock its wings in the same position without exerting any energy and by manoeuvring within the wind gradient can gain energy to stay aloft and progress into wind without flapping its wings. This effect was identified as far back as 1883. Dynamic soaring is also exploited by radio controlled glider modellers. In winds near the surface of 50-60 mph the current world record speed achieved by using the wind gradient to gain energy is 545 mph (USA) and 368 mph (UK) with G forces up to 100! ([url=http://www.rcspeeds.com/pilotslist?t=ll]- RCSPeeds.com)

Wind gradients of course mean that approaching to land into wind will cause a loss of energy as we descend on final. Quite a few glider pilots who have tried to do a downwind beat-ups at the end of a task followed by a pull-up and 180 degree turn to land have either come to grief – or pretty close – because pulling up into a wind gradient whilst going downwind loses a lot of energy and can result in a spin off the turn.

But I think all this is beyond the scope of a Cirrus dangling from a parachute.

[EvaDestruction]

Just guessing, but likely the aerodynamic efficiency of the wing would be greater than that of the canopy, possibly causing it to generate more lift in less wind?

[PDR1]

The effect would be transient, and very brief because the drag of the canopy is large compared with the momentum of the load. You can observe this by just looking at parachutists (or air-deployed loads) which, within a second or two of being released at high-ish airspeeds are descending with the load hanging vertically beneath the parachute. If there was any significat lag between the wind-speed change and the load's velocity then it would be hanging at an angle from the canopy. But it doesn't .

Also even if it WAS true please reference back to my post above where I point out why the aeroplane would most likely be descending in an attitude in which any lift developed would ne negative rather than positive (with or without a conveyor belt).

PDR

[megan]

Whatever the wind gradient you wont notice it in practice on a round canopy decent, the wing of a Cirrus will provide lift during the decent beneath parachute and slow the rate of decent, but it best be called drag rather than lift.

[pilotmike]

Just guessing, but likely the aerodynamic efficiency of the wing would be greater than that of the canopy, possibly causing it to generate more lift in less wind?
WHAT LIFT??

In zero wind??
Dangling at a random angle relative to the horizon? (NOT an AoA because THERE's NO WIND, NO RELATIVE AIRFLOW, REMEMBER!)
What is so difficult to grasp about "There is NO airflow over the airframe. There is NO lift"?

Please, for all our sakes, just give up about the wind - please?
:ugh::ugh::ugh::ugh::ugh: :{:{:{

ATP???? Flight instructor??????? SERIOUSLY????????? OMG!:eek:

[PDR1]

"Will this wind be so mighty as to lay low the mountains of the earth?"

PDR

[Fl1ingfrog]

pilotmike your letting your angst overwhelm you. Of course there is an angle of attack and a relative airflow when descending under a parachute. If not you will not be descending.but simply going with whatever 3D flow that is the wind itself.

[Vessbot]

You’re belaboring the point. Yes air is coming from below, and since the plane hangs in a nose-down attitude, then the AOA is some number below 90 and is making some force pulling forward. And maybe that’s even enough to give a measurable forward speed to the plane-canopy combo. (Like has been mentioned, some round canopies even have vents in the back that make them glide forward; but someone said that this canopy design is not one of those.)

Nevertheless, whatever forward/sideward behavior the aircraft has or doesn’t have, the point is that when descending through a uniform airmass, after any initial period of stabilization, there can be no forward/aft/lateral force form the airmass that’s any different with the airmass moving vs. not; and therefore no force that could alter the descent rate.

Separately, while I echo Pilot DAR’s call for civility and calmness in discussing even obvious points, I’m starting to sympathize (and to feel myself the same way) with those getting exasperated at posts making the same point, for the umpteenth time, without addressing what’s already been pointed out wrt. the inability for a uniform airmass to impart a force to an aircraft within it as if it’s anchored to the ground somehow.

[Pugilistic Animus]

Just to add... the additive of x&y components of a vector draws a parallelogram not a triangle.

[oggers]

...strange then that the basis of the whizz wheel is a triangle.

[megan]

the additive of x&y components of a vector draws a parallelogram not a triangleMmmmm

Parallelogram - In Euclidean geometry, a parallelogram is a simple quadrilateral with two pairs of parallel sides. The opposite or facing sides of a parallelogram are of equal length and the opposite angles of a parallelogram are of equal measure

Triangle - A triangle is a polygon with three edges and three vertices. It is one of the basic shapes in geometry. A triangle with vertices A, B, and C is denoted. In Euclidean geometry any three points, when non-collinear, determine a unique triangle and simultaneously, a unique plane.

[mikehallam]

Well to he 'helpful', [and once the chute and payload jointly settle to a steady fall after the initial deployment] :-

The angle of descent does get less, the stronger the wind ! Smile

[James Austin]

Irrespective of the debate above I find 1700 fpm as rather uncomfortable when hitting solid ground...
​​

Sounds lot less uncomfortable than the alternative.....

I note several comments drawing comparison to parachute landing descent rates. Fair enough - but there all the deceleration is taken on the feet and ankles (hopefully with a decent roll, though I know next to nothing about para-jumping). Landing at 1700fpm into a well-padded seat (complete with airbags) doesn't sound all that terrible.

Nevertheless, I'll try my best to avoid the experience.... :p

[megan]

all the deceleration is taken on the feet and anklesJumping a round canopy only the very experienced were able to do as you describe, those without that ability no, or very little, stress was taken through the legs or ankles because of the inability to precisely judge the moment of touch down due to ground rush, the landing roll distributes the landing shock sequentially along five points of body contact with the ground, the balls of the feet, the side of the calf, the side of the thigh, the side of the hip, or buttocks, the side of the back.I'll try my best to avoid the experience....It's the best fun to be had with your pants on.
.

[B2N2]

Alright now that my brain is bleeding let me suggest the following;

You’re flying something like the Space Shuttle and you have a approach speed of 340kts.
Your rate of descent for a 3 degree (ILS) approach would be 1700 fpm.
You’re sitting there with a big grin on your face and you forget to flare.
You’re going to hit the ground at 1700 fpm no doubt about it.
That’s a hard landing inspection.
Now you’re in a Cirrus under the chute during the end of days and you’ve got a 340 knot wind.
You’re going to hit the ground with a vertical speed of 1700 fpm.
Now with a more realistic wind, 30 kts all the way to the ground, VS 1700fpm.
Just a steeper angle of impact all the way to vertical when the wind is zero.

As far as total impact energy of a combination of forward and vertical speed which is a glancing impact:



Like the age old joke: it’s not the fall that kills you it’s the sudden stop aka deceleration rate. (http://hyperphysics.phy-astr.gsu.edu/hbase/duck.html)

[Jonzarno]

A few thoughts on the 1700 fpm descent rate vs landing in a field after an engine failure:

It is important to consider the momentum that needs to be dissipated in bringing the aircraft to a stop which is proportional to the square of velocity.

1700 fpm is equivalent to 17 kts

The stall speed of my SR22 with full flaps is 59 kts.

That is about twelve times the amount of energy that needs to be dissipated.

The option of trying to dissipate that energy gradually by landing in a field and rolling out can look attractive. Whilst it is perfectly possible to land a Cirrus on a grass strip (I have done so many times) the landing gear and the low prop clearance mean that it is not designed for an off airport landing.

The aircraft is designed to land safely under the chute and incorporates seats with a honeycomb base designed to absorb an impact of 27G, flexible landing gear and later marks also have seatbelt air bags. That said: the aircraft will be damaged although several have been repaired and have flown again.

Quite apart from the energy dissipation calculation, gliding to land in a suitable field is not as easy as it sounds. Whilst we all did power off forced landing approaches in our training and flight tests, picking the right field isn’t that easy:

Field Crops - NoGo Fields (http://www.fieldselection.co.uk/nogo.html)picking the right field isn’t that easy: (http://www.fieldselection.co.uk/nogo.html)

Landing on a road isn’t always a great idea either:

https://www.bbc.co.uk/news/uk-wales-36629540

And by the time you realise that you have one of these problems, you are probably too low to use the chute safely.

I am lucky enough to fly an aircraft equipped with BRS. If it ever comes to it, unless I have a nailed on glide approach to a runway, I plan to use it.

[B2N2]

I’ve got tons of time in light GA SE aircraft and if I had the choice I’d never fly one without a parachute again even though I’m really not a fan of Cirrus.
A future airplane purchase would largely be predicated on the cost of fitting a BRS.
You can argue till the cows come home, parachutes (and GPS) have made general aviation safer for the masses even though it’s not a fix for stupid.

[palomar92000]

If I had an engine failure in a Cirrus and could not reach an airfield I would rather glide down and land in a suitable field. Is that what is recommended or do they suggest pulling the parachute handle?


Cirrus wants you to pull the parachute handle. Too many Cirrus pilots have killed themselves trying to glide into fields when the parachute would have saved them. These airplanes are not much of a glider and with 80kt approach speeds there is a fair bit of energy to go barrelling into a field. And that's assuming there is a field to land in and you're not over mountains, over a heavily populated city, over water... not everyone lives in the mid west.

[B2N2]

I think we need to collectively step away from the notion that an off airport landing is the best option.
Lets be honest, for the first 100 years of aviation it was the only option unless you were sitting on a ejection seat or carried a…..wait for it….parachute.

[sablatnic]

I will not say that Paul Bertorelli is right, but he isn't fully wrong either - at a wind velocity around 8,000 m/sek, a Cirrus under a parachute will actually increase its altitude.

[scifi]

'Groundspeed' is exactly that. It is the speed that the ground is moving.

[Maoraigh1]

" - at a wind velocity around 8,000 m/sek"
??? 8,000m/s is 8km/s which is 8X3600 km/h = 28,800 km/hour.
(I maybe showing my ignorance of the "sek' unit.)