Cirrus descent rate under parachute less with wind?
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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
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
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
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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.
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.
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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.
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
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
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
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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...
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...
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.
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.
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
Last edited by pilotmike; 6th Apr 2020 at 15:55.
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.
"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.
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
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
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.
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?
ATP???? Flight instructor??????? SERIOUSLY????????? OMG!
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.
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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.
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.
the additive of x&y components of a vector draws a parallelogram not a triangle
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.