Parachute cords

Of course I know what would happen if a paratrooper pulled the cord too late…but what would happen if they pulled it too early? I’m not speculating, because I don’t know the purpose of counting before pulling in the first place.

It’d just take 'em longer to get to the ground. The only reason to wait is to have fun freefalling.

Military 'chutes are usually on static lines attached to the plane that open the 'chute as soon as you’re out the door. No counting involved.

I’m not sure, but I seem to recall something I read (likely military fiction) where it was also explained that with some high altitude drops it was dangerous to open the chute early. they have oxegen tanks, but if the chute’s open too early they can be up there longer than the tank lasts.

This of course would not be a “count to 10 and pull the cord” type jump, but rather “keep an eye on the altimiter on your wrist and pull the cord when you reach x thousand feet.”


SWAG alert: I think the reason for waiting came from the WWII-era practice of using airplanes originally designed as transports (mainly the US C-47 / DC-3 and the German Ju-52). They had the exit doors on the side, in front of the tail surfaces, and it was possible for a chute opened too early to snag on the tail to the detriment of both the jumper and the airplane. Making paratroopers count to 3 first let them get safely clear. True, it doesn’t matter on newer planes designed to be military cargo and paratroop transports, with rear-facing doors.

If you’re parachuting from an extreme altitude, for instance in an ejection, you’d want to wait until you reach dense, warm air first, or else risk hypothermia and anoxia.

In the case of spacecraft returning to earth, the main chutes can’t be opened too early, while the speed is still high, or they’d just tear off. Instead, small drogue chutes with very strong lines provide some stabilization as well as slowing, and the mains are deployed later. I’m thinking of Apollo command modules, but I believe Soyuz is set up similarly.

Not a problem. They just make the static lines for a C-47 eight feet longer than normal. Maybe before somebody thought of that, though…

Oddly, I can’t come up with a link, but I know of one case. There’s a story about a Navy parachutist getting snagged on the tail and tailwheel of a DC-2 (whatever its USN designation was) over NAS North Island sometime around 1940. He was rescued by the crew of a 2-man biplane that flew up underneath, cut him loose with a knife, and hauled him into their rear cockpit.

Also, in the extreme case that you were jumping from a plane traveling faster than whatever terminal velocity for a skydiver is, you might want to wait a few seconds to slow down before you pull the cord.

The rough jerk from the chute opening has to be bad enough without having to slow you down from 500 mph!

I’m pretty sure that the deployment sequence is automatic on parachutes used with ejection seats, as the pilot may not be in a condition to pull a rip cord. (One joke about the Martin-Baker seats in the F-4 “Phantom” called the seats “Martin-Breaker”. Newer models of the M-B seats are widely used today.)

There weren’t many DC-2s made, so you’re probably thinking of the DC-3. In the Navy, this was the R-4D.

I’m sure I remember from that magazine article (either Aviation Heritage or Smithsonian/Air&Space, a couple of years ago) that it was in fact a USN DC-2. I still couldn’t find a link to that story, but I did find that USN had a few DC-2’s that they named R2D’s. Too bad they didn’t have 2 versions, so there’d be an R2D-2.

I stand corrected. DC-3s (AKA R4D, C-47, “Dakota”, and occasionally nicknamed “Goony Bird”) so far outnumbered the DC-2s that I didn’t think any DC-2s saw service.

There were only a few R2D’s, after all. It wasn’t until I read that page that I found that the Navy had any DC-5 / R3D’s, either.

The parachutes used by pilots and crewmembers ejecting from an aircraft are designed not to open above an altitude that has sufficient oxygen.

I did some (non-military) skydiving back in the early eighties. As I remember, the first 15 jumps or so were static-line jumps from low altitudes (2000-2500 feet), and the rest were free-fall jumps from higher altitudes where I watched my altimeter and pulled my own ripcord to open the chute.

During the static-line jumps in particular, it was common to jump out the door and count up to a certain number (3? 5?). If you were still falling after that, it meant the static line or main chute had malfunctioned and it was time to take emergency measures (for example, rolling to the side to break a possible vacuum on your back, or popping the emergency chute if the main pack hadn’t opened at all). Same thing during free fall jumps–pull the main ripcord, wait a few seconds, and if nothing happens, then you have a malfunction and it’s time to start considering emergency measures.

In other words, (at least in my own case) the purpose of the count was traditionally a means of measuring off a period during which the main chute should be opening. At the end of the count, if you weren’t already under a chute, then it was time to go for the back-up chute. The count was particularly useful for new or infrequent jumpers, who might freeze up as they went out the door and forget to go for the extra chute in an emergency. Where I jumped, first-time jumpers were instructed to scream out the count as they fell (literally loud enough so that people both in the plane and on the ground could hear them), so that they would stay alert and recognize when it was past time for the main chute to be open.

I haven’t jumped in about 15 years, so I haven’t been keeping up with equipment modifications. But I suspect that automatic openers have been put on all emergency chutes since I last jumped (they were just starting to experiment with them in the early eighties), in which case it’s probably no longer necessary to count. With an automatic opener, if the main chute doesn’t open right away, the emergency chute would pop itself once it registered that the jumper was still free-falling past a certain pre-set altitude. The jumper may not have to do a thing.

Anyway, that’s what I remember about counting from my own skydiving experiences.

Oh yeah. And from what I’ve read in the past about military paratroopers, the average paratrooper used to jump only static-line jumps. Which means that he simply jumped out the door and waited for the static line to open his main chute for him. The only time he pulled a ripcord of any kind was if the main chute didn’t come out and he had to pull the ripcord for the emergency chute. In other words, his case was the same as any static-line jumper: Jump out, count to three, and go for his emergency chute if the main hadn’t come out on it’s own by the end of the count.

I believe there were some Special Forces units that trained with free-fall conditions (including pulling their own main ripcords) for high-alititude insertions, but that was the exception rather than the rule.

Again, I don’t know if today’s paratroopers might have switched to automatic openers for their emergency chutes in more recent times (getting rid of the need for counting).

I see. So as usual, movies and TV have been lying to me; I’m crushed ;). Thank you!

They got it wrong?!? I’m aghast! :wink:

Incidentally, I guess I really didn’t address the OP in my previous responses. Here are a couple scenarios for opening a parachute too soon.

  1. Opening a parachute inside the plane: It happens. Depending on the plane you’re jumping from, it can be pretty crowded inside, and sometimes one jumper’s gear snags on another jumper’s ripcord, and the ripcord gets pulled without anyone noticing. If the plane is at jump altitude and the jumpmaster has opened the door and the inside of the plane is windy, then you suddenly have a parachute billowing and flapping around inside the plane. If even a handful of the fabric gets outside the door of the plane, it is going to catch air, pulling the rest of the chute out, and then pulling the jumper out, all in about a quarter of a second. If the door is on the side of the plane (like most jump planes), then this pretty much means death for everyone. The jumper is going to be pulled out the door so quickly and unceremoniously that he is going to take most of the side of the plane with him, meaning instant death for him and a plane crash for the rest of the people inside.

This is an extremely rare occurrence, but it does happen once in a blue moon, and it’s the most dangerous thing that can happen in parachuting (in that it can kill a whole planeload of people all at once). Jumpers are instructed to keep a hand over their ripcords and leap on top of any stray parachutes that might suddenly appear out of nowhere.

  1. Opening the chute as the jumper is standing on the “step” outside the plane: Many jump planes are equipped with a little platform just outside the door called the “step.” One or even several jumpers at once can climb out the door and wait on the step for the signal to jump. If a chute were popped while waiting on the step, it’s possible that the chute could foul on the tailwing, in which case you might have a case where a parachuter is dangling from the tailwing. If the jumper is conscious, he can just cut away his main chute, go into freefall, and pop his emergency chute. If he’s unconscious, then a second plane could try to rescue him in the air, or the pilot of the first plane can try to land on grass and hope the jumper survives the bumping and dragging.

But overall, this scenario is unlikely. With most planes that jumpers use, the tailwing assembly sits high enough in flight that the parachute and jumper will simply fly harmlessly underneath the tailwing assembly. To get caught in the tailwing assembly the jumper would practically have to leap upward as the chute was being popped. But it does happen once in a blue moon–occasionally a first time jumper jumping from a small plane is so full of adrenaline that instead of simply stepping backward off the step, he leaps upward like he’s doing a swan dive off a diving board, and the static line gets caught somehow on the tailwing. It’s basically a freak occurrence. You hear about something like that happening once every 10 years or so.

  1. As for how soon you can safely pop your chute after you bail out the door or step off the step (assuming you want to deliberately pop your chute at the earliest possible instant), I would say that a jumper would be entirely clear of the plane within about a second or so. Step off a 12-foot ladder sometime and see how quickly you hit the floor. Once you’re out the door and falling, you’re underneath and behind the plane almost instantly. Add in the half-second or so that it takes for the pack to open and the parachute to begin to unfurl, and it’s hard to imagine any scenario where popping your chute too early is a problem. (I think that most static lines are only about 12 or 15 feet long, which means that the parachute is popped within the first second of the fall during a static-line jump.)

In summary, I would say that popping one’s chute too early is generally not a big concern for most jumpers. There are a lot of ways to get in trouble in parachuting, but fouling your chute in the tailwing assembly of the airplane isn’t really something most jumpers worry about.