Low Altitude Helicopter jump?

Hi – I have zero jumps. I am doing research for a book and need some specific info I haven’t found online yet – or links if possible. I realize from a helicopter it’s not a BASE jump and that it is a skydiving jump:

1. Can you/should you however use BASE gear when doing a low altitude heli jump? Or would there be specific gear for this.
2. What is the lowest possible jump that you could do from a helicopter. (100ft, 200, 300, more?)
3. Could you/would you have a reserve to do another low altitude jump (350ft) immediately after doing the heli jump?
4. Would you be able to jump from a bridge right after someone jumped and catch up to them on a 350 ft. jump and still have time to open a reserve at 80-90ft. (I've seen online this is the lowest recorded) (I realize it’s pushing critical limits for deployment) – or is this beyond the realm of reality? This will be into a river. I expect one character to (likely) die and have no problem giving the other one broken bones.

Thank you for any help!

Extra butter on my popcorn, please.

In reality you would simply land the helicopter. Or maybe rappel out of it.

At low altitudes, with a skydiving rig, the downdraft would not help the opening, combined with very sub terminal body speeds you'd prolly struggle to get a canopy open from that height. Unless you had very high forward speed from the chopper.

Is this a serious question?
Maybe do a (tandem) jump to know the how and what. And talk to some instructors.

This was a base jump from a helicopter, carried out by two stuntmen. Their target, dependent on wind direction, was one of the five bridges surrounding the Olympic Stadium and water recovery teams were discreetly placed upstream. There was a seminar at the UK Skydiving Expo a few years ago about it but I can't seem to find the video of the talk.

https://www.youtube.com/watch?v=IccmIECEqTU

Thank you very much for all the information! I do appreciate it!

billvon

>1. Can you/should you however use BASE gear when doing a low altitude heli jump?

You can. It's not legal but will work. Stunt people do this via FAA waivers.

>2. What is the lowest possible jump that you could do from a helicopter. (100ft, 200, 300,
>more?)

Zero feet.

There's really no "lowest possible." If the airspeed is ~40kts you can go to any altitude - below about 40 feet you will likely survive even with no/partial deployment, and above 40 feet you will likely get enough of a canopy to slow you down to survivable speeds.

If the airspeed is zero knots you are going to have to be significantly higher due to the downwash of the rotors.

Note that if the wind at the surface is 20kts, and you are hovering over one piece of ground, your airspeed is 20kts.

>3. Could you/would you have a reserve to do another low altitude jump (350ft) immediately
>after doing the heli jump?

With specially built gear and a lot of practice you could do something like that. People have done cutaways from the NRGB, which of course is a lot higher (~900 feet.)

>4. Would you be able to jump from a bridge right after someone jumped and catch up to
>them on a 350 ft. jump and still have time to open a reserve at 80-90ft.

No. At 350ft you are ballistic for most of the jump; no "catching up" through clever flying.

In Vietnam my uncle fell or jumped (no parachute) from a helicopter that was “going down”. He landed in a rice paddy, largely unhurt. The helicopter went a bit further, crashed in flames and everyone was presumed dead, so under fire the other helicopters left the seen, my uncle unobserved. He was career airborne, which might have helped him with his “landing”.

> 1. Can you/should you however use BASE gear when doing a low altitude heli jump? Or would there be specific gear for this.
BASE gear would be fine, provided your characters don't care about the legality of it, have their asses covered or do it in a country that doesn't care that much about the rules.

> 2. What is the lowest possible jump that you could do from a helicopter. (100ft, 200, 300, more?)
Plenty of BASE jumps are done from 200-300ft. (Note - if you're having your character jump from 200ft, they'll want to deploy the parachute immediately. 300ft, you can give them a sec or two of freefall )

> 3. Could you/would you have a reserve to do another low altitude jump (350ft) immediately after doing the heli jump?
If you're asking about landing on a 350ft bridge and jumping off it with another parachute, then no, not really. You could use the same parachute, but it would be an unpacked jump (hanging the parachute off the edge and doing a rollover, for example), which probably wouldn't work for #4.

> 4. Would you be able to jump from a bridge right after someone jumped and catch up to them on a 350 ft. jump and still have time to open a reserve at 80-90ft. (I've seen online this is the lowest recorded) (I realize it’s pushing critical limits for deployment) – or is this beyond the realm of reality? This will be into a river. I expect one character to (likely) die and have no problem giving the other one broken bones.
How about tackling them just as they let go and drop? If your character is the calculating type, he or she may then get a hold of them with one arm and wait 2-3 seconds before using their free hand to deploy the parachute, because they realize there's no way they'll be able to hold on to the other person through the opening, but they might just slow down their fall a little bit, and give them a chance of surviving.
We've seen Hollywood do much worse than that...

One caveat: don't try to freefall from a helicopter hovering at 200 feet. That low means tossing the pilot chute immediately and a high risk of entanglement with the jumper in the turbulent airflow immediately below the helicopter.
You could do something clever like have your character hand his pilot guts to a helicopter crew member and yell "Here. Hold this!" Buddy falls out of the helicopter and stretches out the parachute. The helicopter crew holds onto his pilot huge until it is ripped out of their hands (line stretch). A couple seconds later our hero is hanging under a fully-inflated parachute. This is sometimes referred to as "pilot-chute assist."

The chute will probably be built specifically for BASE jumping with the configuration and packing method tailored to the altitude.

After buddy lands on the bridge, he scuffles with the bad guy - who falls off the bridge. Our hero pulls his ripcord. The spring-loaded reserve pilot-chute leaps out. Our hero ties his pilot-chute to the bridge railing and jumps off. The reserve chute deploys similar to the first chute, with the pilot-chute and bag left hanging from the bridge. Reserve parachutes open almost as quickly as BASE canopies because they are packed almost the same way.

For exact details, contact a BASE equipment manufacturer like Apex BASE. They can also provide stuntmen for your film.

PM sent, if you haven't seen it.

I'm not a BASE jumper but have done some research and have a basic understanding of the discipline.
1. For sub-terminal jumps below 1000ft you should use BASE gear.
Here's an overview of gear and skydiving: Skydiving gear is mostly made and packed for terminal velocity openings (~120MPH) where you want to decelerate by a slow and progressive opening, a quick & hard opening can kill you! A main chute takes about 700-1000ft to open and a reserve is designed to open in 350ft, and is used only in an emergency if the main malfunctions. The minimum (legal) altitude to deploy your main is 2000ft and for the reserve it's above 1000ft (or 1500ft if you want to be more conservative). For example, if there is an aircraft emergency during climb up, like an engine failure, and the plane is below 1000ft (or 1500ft) then the skydivers can't jump and must land with the plane. But they may bailout if above that altitude.

BASE gear is mainly made and packed for faster openings at sub-terminal speeds from lower altitudes.

2. 160-180ft is feasible but considered very low. At these altitudes you don't really get any freefall and you don't have margins for error, they are usually done using static line: you have a line attached to the object or aircraft you are jumping from, and that extracts your chute as you fall away, giving you a very fast opening.
Paratroopers use static line with round parachutes, and I believe the training altitude is 1000ft and the actual combat altitude is around 300ft (someone correct me if numbers are off)

3. As mentioned above, a reserve is usually used as backup in an emergency and not for a 2nd jump, but I realize we are talking fiction here. I've heard that some BASE rigs have a reserve, however, the BASE altitudes in most cases are too low to make reserve use feasible. In order to cutaway your main and use a reserve at 350ft you would need to have a Skyhook or other MARD (Main Assisted Deployment System), what this does is use the drag of the cutaway main to pull your reserve out faster, think of it as a static line jump with the extraction line attached to the detached main chute.

4. Here's some more skydiving physics: it takes you around 10 seconds to cover the 1st 1000ft (you're accelerating from 0 to 120MPH) and after that you're travelling at terminal velocity (wind resistance stops you from accelerating further) and covering 1000ft at 5.5 seconds. When you're going at 120MPH you have a lot of drag (air resistance) and can influence your speed by changing the amount of surface area you are presenting to the wind: flatten out your body on your belly and you slow down since you are presenting maximum surface, become a needle by going head down and you speed up. All this is possible because you're moving fast. However, at sub-terminal speeds you don't have much control (not much air resistance) so you are at the mercy of gravity. Compare this to feeling the wind in your hand when you stick it out the window of a fast moving car v.s. a car driving slow in a parking lot where you feel nothing.
So at low jump altitudes air resistance doesn't have much effect and you can approximate the motion by using basic physics for falling objects in a vacuum: they fall at the same rate. Therefore, 2 objects leaving at different times can't catch each other unless the 2nd one has more initial speed than the 1st.
From 350ft (106m) the time to impact is roughly 4.5 seconds, calculated by: t = square root of 2d/g
Where d = distance in meters, g = gravity acceleration: 9.8 m/s^2
So assuming 4 sec working time, a 1 sec canopy deployment time and jumping out 1sec after someone, you have 2 sec to catch them... provided you added more initial trust so you have more speed... You decide if that is feasible.

Thanks for the continued replies guys! I really appreciate the great feedback and detailed information. I know a lot of this is common knowledge for some of you but I appreciate you sharing it with me, it helps tremendously.

ssspyros

... Paratroopers use static line with round parachutes, and I believe the training altitude is 1000ft and the actual combat altitude is around 300ft (someone correct me if numbers are off) ...

As usual, it depends AFAIK minimum jump altitude for static line rounds differs for basic training (1250ft?), tactical training (1000ft) or combat jump. And also depends on the drop speed of the aircraft, for jumps from slow aircraft or helicopters the altitude goes up. I seem to remember that minimum drop altitude for a combat jump from a faster aircraft is around 500ft.
The British have low level rounds, designed to go as low as 250ft.

I jumped a small helicopter with next to nothing airspeed from about 1000-1100 feet with a freepacked StratoFlyer; took a couple of seconds freefall to enjoy the proximity of the treetops and still had a decently long canopy ride. The problem with lower jumps requiring extreme accuracy is lack of canopy time to set up your landing.

ssspyros

Paratroopers use static line with round parachutes, and I believe the training altitude is 1000ft and the actual combat altitude is around 300ft (someone correct me if numbers are off)

It was 800ft for training and down to 400ft for a true combat jump with the older T-10, and is now 1000ft for training and down to 600ft for the new T-11. During the Basic Airborne Course, they typically jump around 1250ft.

This is the US military though, I couldn't really comment on specifics from other countries.

The current UK issue parachute has a minimum drop altitude of 76m (250ft) and a max speed of 140kt.

https://www.airbornesystems.co.uk/airborne-systems-products-services/aerial-delivery-search-and-rescue-products/aerial_delivery_personnel/8m-low-level-parachute-assembly/

is the book on Amazon yet?

On 1/15/2018 at 9:18 PM, fastphil said:

is the book on Amazon yet?

Yes it is, thank you for asking!  https://www.amazon.com/dp/B086Q8J7HR/ref=cm_sw_r_tw_apa_i_-9qIEb7HJAC1X?ref=d6k_applink_bb_dls&dplnkId=c34091ba-ab97-4e63-8cb0-c356fb026987 

On 11/28/2017 at 9:43 PM, Scarface007 said:

 I am doing research for a book ..............

Never let the facts get in the way of a good story 

13 hours ago, Scarface007 said:

Yes it is,

From one of the Amazon.com reviews: "An entertaining read with excellent descriptions of the areas surrounding Angel Falls. I found the differences between customs there as opposed to in the USA to be quite stark..."

7 minutes ago, Erroll said:

From one of the Amazon.com reviews: "An entertaining read with excellent descriptions of the areas surrounding Angel Falls. I found the differences between customs there as opposed to in the USA to be quite stark..."

Great. The author (and OP of this thread) goes to all that effort to get the details of the parachute part at least sort of plausible, then moves Angel Falls from Venezuela to Africa.

Note: we really need a 'sarcasm' font.

so, you read it and the helicopter part was believable? 

2 hours ago, sfzombie13 said:

so, you read it and the helicopter part was believable? 

I'm guessing Joe was referring to the original posts where the author was seeking information to make it believable.

So, to Scarface007, the author and OP, maybe you could post a pdf here of the relevant helicopter/parachute/bridge/(Angel Falls?) scene so we could see how believable that did turn out?