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Military Halo Jump (Tech Question)  
User currently offlinewardialer From United States of America, joined Sep 2001, 1183 posts, RR: 0
Posted (3 years 5 months 2 weeks 3 days 16 hours ago) and read 25556 times:

For example, how long would a free fall take from 30000 feet to ground level? Is there a simple formula for this?
I know ground level is not realistic since you are closure to the gorund, of course, you need to deploy the parachute. But this is just for an example.

Or, lets say from 30000 feet to "Opening Altitude" which would be like around 7000 feet. How long would the free fall take from 30000 feet to 7000 feet?

thx.

16 replies: All unread, jump to last
 
User currently offlinetugger From United States of America, joined Apr 2006, 5797 posts, RR: 10
Reply 1, posted (3 years 5 months 2 weeks 3 days 16 hours ago) and read 25549 times:

Quoting wardialer (Thread starter):
For example, how long would a free fall take from 30000 feet to ground level? Is there a simple formula for this?
I know ground level is not realistic since you are closure to the gorund, of course, you need to deploy the parachute. But this is just for an example.

Or, lets say from 30000 feet to "Opening Altitude" which would be like around 7000 feet. How long would the free fall take from 30000 feet to 7000 feet?

Though it is of course mission specific, I am betting they would more likely open at less than 2,800 AGL. That's a "normal" low safe open altitude for fun jumpers. Basically 2,800' gives you time to pull and if there is a problem with your main chute, to cut away and open your reserve and reorient yourself for a landing.

For a military HALO operation though they quite likely would open lower than that to minimize any chance of being seen by others. They wouldn't be as concerned about the risk of a chute not opening as each is packed professionally and the worry isn't about a problem with a chute opening (which happens rarely anyway). If you open at 7,000' you would give people on the ground about 7 minutes to spot you. Technically they could open as low as 1,000' but that is really low and doesn't leave much time to orient yourself for landing.

So with that said, and using this freefall calculator: http://keisan.casio.com/has10/SpecExec.cgi, the freefall time would be around 75 seconds (30k to 2k)

Tugg



I don’t know that I am unafraid to be myself, but it is hard to be somebody else. -W. Shatner
User currently offlinemffoda From United States of America, joined Apr 2010, 1114 posts, RR: 0
Reply 2, posted (3 years 5 months 2 weeks 3 days 6 hours ago) and read 25441 times:

In MFF Operations (HALO), the typical opening altitude for a training jump is 4000' AGL. (will depend on experience level to some extent)... As far as FF time/speed is concerned, It is approx. 120 mph or 55 mps. That works out to be approx. 5.6 seconds per 1000'. (however, one must reach terminal velocity first.)


harder than woodpecker lips...
User currently offlinetugger From United States of America, joined Apr 2006, 5797 posts, RR: 10
Reply 3, posted (3 years 5 months 2 weeks 3 days 5 hours ago) and read 25430 times:

Quoting mffoda (Reply 2):
In MFF Operations (HALO), the typical opening altitude for a training jump is 4000' AGL. (will depend on experience level to some extent)... As far as FF time/speed is concerned, It is approx. 120 mph or 55 mps. That works out to be approx. 5.6 seconds per 1000'. (however, one must reach terminal velocity first.)

That calculation only works with lower altitudes "thick" air (normal max "fun jump" altitude is 14,000' so no oxygen is needed for the ride), the thinner the air the higher the terminal velocity, hence the shorter the freefall times.
For example in 1960, when Captain Joseph Kittinger jumped from 102,800', he fell for 4 minutes and 36 seconds and reached a maximum speed of 614 mph. That's 276 seconds to fall 89,000' (he popped his chute at 14k').

Tugg



I don’t know that I am unafraid to be myself, but it is hard to be somebody else. -W. Shatner
User currently offlinewardialer From United States of America, joined Sep 2001, 1183 posts, RR: 0
Reply 4, posted (3 years 5 months 2 weeks 3 days 5 hours ago) and read 25423 times:

Tugger - The calculator link does not work. Can you please post another alternate link? Thx.

Or, can this formula be done from a regular standard calculator?

I was going also ask you what speed did you enter to give the 75 second fall result from 30K to 2K?


Also, what is more covert? HALO or HAHO? And I cannot understand why HAHO would be covert as well because the chutes open at a much HIGHER altitude compared to HALO and enemies may spot you if one glides down at a very very slow rate of descent.

[Edited 2011-07-12 10:26:27]

User currently offlinetugger From United States of America, joined Apr 2006, 5797 posts, RR: 10
Reply 5, posted (3 years 5 months 2 weeks 3 days 4 hours ago) and read 25400 times:

Quoting wardialer (Reply 4):
Tugger - The calculator link does not work. Can you please post another alternate link? Thx.

Or, can this formula be done from a regular standard calculator?

I was going also ask you what speed did you enter to give the 75 second fall result from 30K to 2K?

Hmmm, lets try this:
Free fall (time and velocity)

If the link works you'll see that the calculation is fairly easy and if your calculator can handle equations then it can do it. Basically its a straightforward curve. The key difficulty is factoring in the thinner atmosphere which reduces drag and increases freefall speed at the higher altitudes. Ergo the freefall speed decreases as you go lower in the atmosphere and the air gets thicker and drag increases.

I didn't enter in any speed as it is the gravitational constant of 9.8m/s2, the only variable is "how high".

Quoting wardialer (Reply 4):
Also, what is more covert? HALO or HAHO? And I cannot understand why HAHO would be covert as well because the chutes open at a much HIGHER altitude compared to HALO and enemies may spot you if one glides down at a very very slow rate of descent.

They are two different types of operations. If you have airspace access then HALO is fine but if you do not have the ability to get near the airspace of the intended target without being detected then HAHO can be used. A HAHO team can be deployed many, many miles outside an opponents airspace and fly under canopy to the intended target. Basically a HAHO relies on the fact that a person under a canopy is a very small radar target, and for all intents and purposes is undetectable to radar. HAHO usually uses the cover of night to minimize visual detection.

So they are covert because the opponent cannot see them coming.

And you can actually combine HAHO and HALO ops, you go HAHO to enter airspace then "remove" your canopy and do a HALO to drop down quickly and get to the ground.

Tugg

[Edited 2011-07-12 11:16:53]


I don’t know that I am unafraid to be myself, but it is hard to be somebody else. -W. Shatner
User currently offlinemffoda From United States of America, joined Apr 2010, 1114 posts, RR: 0
Reply 6, posted (3 years 5 months 2 weeks 3 days 2 hours ago) and read 25340 times:

Quoting tugger (Reply 3):
Quoting mffoda (Reply 2):
In MFF Operations (HALO), the typical opening altitude for a training jump is 4000' AGL. (will depend on experience level to some extent)... As far as FF time/speed is concerned, It is approx. 120 mph or 55 mps. That works out to be approx. 5.6 seconds per 1000'. (however, one must reach terminal velocity first.)

That calculation only works with lower altitudes "thick" air (normal max "fun jump" altitude is 14,000' so no oxygen is needed for the ride), the thinner the air the higher the terminal velocity, hence the shorter the freefall times.
For example in 1960, when Captain Joseph Kittinger jumped from 102,800', he fell for 4 minutes and 36 seconds and reached a maximum speed of 614 mph. That's 276 seconds to fall 89,000' (he popped his chute at 14k').

Tugg



I am well aware that air is thinner as one increases altitude... But, there is a tremendous difference between 25-30k' f vs. 102k'.

the link below is from the United States parachute association.

http://www.uspa.org/Portals/0/SIM/Freefall_Table.pdf

The table lists the various Exit Altitudes (feet) with an opening altitude of 3,000'.

Example: Exit altitude 14,000', freefall distance 11,000', FF speed 120 mph, FF time 66 seconds. (with given terminal velocity)

Interestingly... 11,000' (11) x (5.6) (from my earlier post) = 61.6 seconds + (however, one must reach terminal velocity first.) = 66 seconds.
 



harder than woodpecker lips...
User currently offlinemffoda From United States of America, joined Apr 2010, 1114 posts, RR: 0
Reply 7, posted (3 years 5 months 2 weeks 3 days 2 hours ago) and read 25332 times:

Quoting wardialer (Reply 4):
what is more covert? HALO or HAHO?



HAHO is more clandestine, because the A/C is further from infiltration point and generally out of sight and sound. With today's generation of parachutes a haho operation from 30k' could provide a offset of between 60-80 kilometers. (depending on wind and equipment load.)

Quoting tugger (Reply 5):
And you can actually combine HAHO and HALO ops, you go HAHO to enter airspace then "remove" your canopy and do a HALO to drop down quickly and get to the ground.



"enter airspace then "remove" your canopy"

You are going to have to explain that one to me?? Are you suggesting cutting your main chute away?  Wow!



harder than woodpecker lips...
User currently offlinetugger From United States of America, joined Apr 2006, 5797 posts, RR: 10
Reply 8, posted (3 years 5 months 2 weeks 3 days 2 hours ago) and read 25321 times:

Quoting mffoda (Reply 6):
I am well aware that air is thinner as one increases altitude... But, there is a tremendous difference between 25-30k' f vs. 102k'.

I understand, and I was certainly not implying anything about your knowledge in my response. Merely pointing out that the 5.6 calc doesn't work for a 30k' drop.

My big glaring mistake is that the calculator I posted and used is most definitely wrong and I did not check the number properly (I trusted the calculator, my bad    ). It did not factor in drag which means its assuming freefall in a vacuum, which is of course very wrong. I'll chalk up my failure to it being late when I first posted and then rushing this morning and not properly vetting my numbers.    Ah well....

This calculator from the same site does take drag into account:
Free fall with air resistance (time and velocity)

And it calculates a time of approximately 144 seconds for a 200lb person falling 28,000 feet. time will of course change for varying weights (a 300lb person takes just 120 seconds) and wind resistance (i.e. drag or "size" of the person falling).

Again my apologies for providing incorrect times.

Tugg



I don’t know that I am unafraid to be myself, but it is hard to be somebody else. -W. Shatner
User currently offlinetugger From United States of America, joined Apr 2006, 5797 posts, RR: 10
Reply 9, posted (3 years 5 months 2 weeks 3 days 1 hour ago) and read 25303 times:

Quoting mffoda (Reply 7):
"enter airspace then "remove" your canopy"

You are going to have to explain that one to me?? Are you suggesting cutting your main chute away? Wow!

Yes, that can be done!

Not hard to have multiple chutes, every skydiver already jumps with two, a main and a reserve. For a military operation, it all depends on the requirements of the mission. It is easy enough to pop your second canopy when you reach the desired altitude.

Normal civilian skydivers have done this before (though it is not something that is normally done), intentionally jumping with multiple mains, popping the first at a high altitude, then cutting the first one away and freefalling again and then popping their "main main" (still keeping the reserve available).

The first canopy can take a long time to drift to the ground and land a looong way from the LZ. For a military ops you wouldn't just let the canopy go as it can lead to you discovery. Instead it is "removed" from use and concealed (how that would be done so there is no risk to the skydiver I have no idea) or destroyed after it is cut away (incendiary device?).

Tugg



I don’t know that I am unafraid to be myself, but it is hard to be somebody else. -W. Shatner
User currently offlinemffoda From United States of America, joined Apr 2010, 1114 posts, RR: 0
Reply 10, posted (3 years 5 months 2 weeks 3 days ago) and read 25282 times:

Quoting tugger (Reply 9):
Yes, that can be done!



The only military unit that routinely did or does cut away's is the USAPT (Golden Knights). They would attach a 3rd canopy (round) to the front of their harness and use it to demonstrate a malfunctioning canopy.

No military unit that I have ever worked with has ever utilized a 3rd canopy in the manner in witch you suggest.

On the other hand, we have done a variation of HAHO... HAMO, where we would freefall to a medium altitude of approx. 12,500' before deploying the main canopy.

btw tugger... do you know what the first 3 letters of my screen name stand for?  



harder than woodpecker lips...
User currently offlinetugger From United States of America, joined Apr 2006, 5797 posts, RR: 10
Reply 11, posted (3 years 5 months 2 weeks 3 days ago) and read 25253 times:

Quoting mffoda (Reply 10):
The only military unit that routinely did or does cut away's is the USAPT (Golden Knights). They would attach a 3rd canopy (round) to the front of their harness and use it to demonstrate a malfunctioning canopy.

No military unit that I have ever worked with has ever utilized a 3rd canopy in the manner in witch you suggest.

On the other hand, we have done a variation of HAHO... HAMO, where we would freefall to a medium altitude of approx. 12,500' before deploying the main canopy.

On the multiple canopy options, I don't doubt you (I would be foolish to do so), all I was saying is it can be done. There would be very few situations where it would be. And if you say you haven't seen it then I can't argue.

Quoting mffoda (Reply 10):
btw tugger... do you know what the first 3 letters of my screen name stand for?

Well after a quick google I did! And I will assume that you are not using ODA improperly. So hats off to you, sir.

After your first post I suspected (hey, this is A.net, I've learned) that you knew what you were talking about and noticed "MFF" matched your name. Quite possibly you have fallen a few thousand miles.

And though I don't have much air under me, happily I am not a Wuffo.

Tugg

[Edited 2011-07-12 15:55:24]


I don’t know that I am unafraid to be myself, but it is hard to be somebody else. -W. Shatner
User currently offlinemffoda From United States of America, joined Apr 2010, 1114 posts, RR: 0
Reply 12, posted (3 years 5 months 2 weeks 2 days 22 hours ago) and read 25225 times:

Quoting tugger (Reply 11):
happily I am not a Wuffo.


No harm done tugg...   



harder than woodpecker lips...
User currently offlinewardialer From United States of America, joined Sep 2001, 1183 posts, RR: 0
Reply 13, posted (3 years 5 months 2 weeks 2 days 17 hours ago) and read 25138 times:

I usually done it this way given the AVERAGE speeds for example:

From 30000feet to 2000 feet would equal 28000 feet difference which turns out to be 5.30 miles. (28000 / 5280).
Then take the 5.30 miles / 150mph (150 is just an average example I use) and that then turns out to be 2.11 minutes.

1 mile = 5280 feet

So just take the jumping starting alt of 30000 feet and the opening chute alt of 2000 feet = 28000 difference = 5.3 miles.
Then take the 5.3 miles divide that by 150 and you get 0.0353 and then X that by 60 = 2.11 minutes on a standard calculator. Of course, it will not be accurate because it depends on weight, density alt, and so forth. Its just a rough estimate on the freefall before opening begins....

[Edited 2011-07-12 22:26:53]

User currently offlinetugger From United States of America, joined Apr 2006, 5797 posts, RR: 10
Reply 14, posted (3 years 5 months 2 weeks 2 days 4 hours ago) and read 24978 times:

Quoting mffoda (Reply 12):
No harm done tugg...

So I have a question. Normally I always set my altimeter on the ground at the LZ. A simple way to know when you wanted to open, i.e. when you were close enough to the ground. With MFF you don't have that. How do you set a firm opening altitude? Atmospheric pressure reports for the area? Laser/ground altimeter? Something else? Just curious. Thanks.

Tugg



I don’t know that I am unafraid to be myself, but it is hard to be somebody else. -W. Shatner
User currently offlinemffoda From United States of America, joined Apr 2010, 1114 posts, RR: 0
Reply 15, posted (3 years 5 months 2 weeks 1 day 4 hours ago) and read 24843 times:

Quoting tugger (Reply 14):


The easiest way is to set the altimeter at the departure airfield, by adding or subtracting the difference from the DZ / IP (map data). You can also get elevation, barometric pressure and wind direction from the A/C and sometimes nearby airfields.

Rgds,



harder than woodpecker lips...
User currently offlinewardialer From United States of America, joined Sep 2001, 1183 posts, RR: 0
Reply 16, posted (3 years 5 months 2 weeks 5 hours ago) and read 24705 times:

http://www.paragear.com/catalog/PICTURES/altimeters/I1170-3.jpg

In the pic above, what type of altitude does this measure? The sea alt or the AGL alt for skydiving operations?

I always see these on HALO jump operations on ones wrist I suppose it is MSL rather than AGL....I dont know for sure....Please, can someone verfiy?

BTW - I got an offer to try out skydiving, but not for the military though....Its more of a recreational jump from a Mi-8 helicopter.....Question is, is a military operations junp more reliable than these recreational ones? I have to get myself prepared for this....


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