Cirrus descent rate under parachute less with wind?
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
The angle of descent does get less, the stronger the wind ! Smile
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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....
all the deceleration is taken on the feet and ankles
I'll try my best to avoid the experience....
.
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.
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.
Last edited by B2N2; 4th Sep 2021 at 06:33.
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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 Fieldspicking the right field isn’t that easy:
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.
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 Fieldspicking the right field isn’t that easy:
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.
Last edited by Jonzarno; 5th Sep 2021 at 07:58.
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.
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.
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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.
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.
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.
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.
