Why the "500's" in jump altitudes - e.g., 9500 not 9000?

[pchapman 279]

I'm curious: Why have jump altitudes historically been at "500's" instead of full thousands of feet?

I'm guessing it followed the VFR cruising altitude regulations in the USA, where VFR aircraft cruise at the 500's and IFR cruise at the full thousands?

[NickDG 23]

So it matched with the 30 seconds from 7.5 and the 60 seconds from 12.5 in the freefall tables in the back of those little red log books . . .

NickD BASE 194

[Spizzzarko 0]

Why not?


No really... Planes flying east fly at odd thousand plus 500 feet, and planes flying west fly at even thousand feet plus 500 per FAA Recomendations.

[JohnRich 4]

Quote

Planes flying east fly at odd thousand plus 500 feet, and planes flying west fly at even thousand feet plus 500 per FAA Recomendations.

Yeah, but jump planes use the same altitude levels no matter which direction they are flying the jumprun...

For your theory to be true, east/west jump runs would be at 13,500', while north/south jump runs would only get 12,500'. And that ain't so.

And I won't even mention the MSL vs. AGL complication.

[Andy9o8 2]

Nick is correct. In the "red logbook days", it started at 2,500 & went up at 1,000 ft increments.

[pchapman 279]

Yeah, I realized the problem with the FAA altitudes varying with the direction of flight.

I'll accept the best answer seems to be that they started counting at 2500' and just went up from there. I had to remember skydivers didn't start out at some arbitrary 'top floor', but worked their way up -- doing style and eventually even relative work 'way up high' at 7500'.

[wartload 0]

The east-to-west (and opposite) rule applies to planes flying from one location to another. In theory, at least, jump planes are circling. Since pilots are not supposed to throw anything out of a plane (including jumpers) when they can't see the ground, they are flying under VFR conditions - which means thousands-plus-500 altitudes in level flight and see-and-avoid rules apply (unless they are in controlled airspace).

[jumpwally 0]

Naw,,,i like the 30 and 60 second explanation better.....

smile, be nice, enjoy life
FB # - 1083

[patworks 5]

500's because the first 'altimeter' was a stopwatch. We freefall parachutists could delay our opening by exiting high enough to allow an "X"-second delay before parachute deployment. You timed your freefall with the stopwatch. Altimeters did not replace stopwatches for a long time. During the transition period in the 1960s both a stopwatch and an altimeter were mounted in a mini-dashboard bungied to your chest reserve. Altimeters were scarce, expensive, and bulky. The only altimeters available. They sported two hands. A fat one displayed AGL in thousands of feet. The skinny one recorded feet and spins like a top in freefall. Size-weight = a can of beans. It seemed that all altimeters were purloined from airplane-dashboards from grounded airships.
Having one was a status badge. My Jumpmasters allowed me to progress from 10 second delays directly to 30 second delays if I purchased an altimeter for $25.00 then-there. I did. We did. .............. Branded in my memory is that interesting jump. Anyhow, the '500 is an artifact of what we parachutist’ called 'delayed-falls' in an epoch when altitude was measured by time.

Pat Works nee Madden Travis Works, Jr .B1575, C1798, D1813, Star Crest Solo#1, USPA#189,

[pchapman 279]

Thanks for finding the thread, Pat, after 6 years!

I would need examples to see how it worked according to your scenario.

For example, one might say jumpers open at around 2500', and on one set of freefall tables (not necessarily what one used in those days), a 15 second delay is 2005'. So jump at 4500'. But would one have used 2500', not 2000' as an assumed pull altitude? And a 30 second delay shows up as 4615', so then one would pick 2500' + about 4500' = 7000'.

So it all depends on what assumptions one uses. Perhaps a particular set of them make it work out the way you say?

[jimmytavino 16]

a few reasons though that logbook reference works for me....

1. because Howie said so !!

2. and because saying "Seven-Five" or
"Ten-Five".. sounded so much cooler than saying "Seven" or saying "Ten".

plus 500 feet more, is 500 feet More...

jt
a3914
nscr1817

[lodestar 0]

Don't forget to dial in the altitude of the drop zone as well, assuming that the figures presented here are AGL but to clarify the altitudes presented here they are Above Ground Level. Something that could easily confuse a novice. Although most all jumpers will set the altimeters at "Zero" on the ground thus compensating for the altitude of the DZ.
Just a miniscule point but one to be considered.

[SCR216 2]

Hello Pat,

My way of looking back on it fits right in with yours.
Also as i remember it, Jacques Istel is the one that put the rules together for the first sport log books with the delay times from exit altitude to opening altitude. They were figured at that time by a stop-watch.

I still have the scar on my chin from the first time I had to use my belly reserve with the dashboard altimeter / stop-watch / knife / compass / night-light / air-horn and condom holder on it.

[Andy9o8 2]

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because Howie said so !!

[jimmytavino 16]

Andy9o8
that was absolutely for you !!!...when i posted it...
and for tbrown.
We three and maybe jking of Fingerlakes Skydivers and hymand over in Syracuse, might get a Laugh out of that.....!!

for others...Howie was a DZO ...in another time.... MANY interesting and funny and memorable stories...
and so since this is the history forum..... i tossed it out there...

jmy
A 3914
pops3935

[patworks 5]

Sorry, No. I was there. Then was not now.

Pat Works nee Madden Travis Works, Jr .B1575, C1798, D1813, Star Crest Solo#1, USPA#189,

[RogerRamjet 0]

I think Nick is right too though I didn't know there were tables in the back of the book... It was about time from exit altitude to 2000 feet (normal pack opening altitude for experienced jumpers at that time).

12,500 = 60, 10,500 = 50, 7500 = 30.

And then there were the style guys and gals who went (at least at Z-Hills where I started) to 6600. Not sure what the time to opening was for them since they got into such a tight ball for the turn/loop sequences.

-----------------------
Roger "Ramjet" Clark
FB# 271, SCR 3245, SCS 1519

[AndreLapointe 0]

My understanding of it, the price was to the 1000'
For example $10 to 7000 ft.

But the pilot was not always at 7000 ft when he got over the spot.

For billing simplicity, the *500 ft is the limit altitude at a specific price.
At *600 ft the price goes up to the next increment.

For example, 6600' to 7500' is $10
then 7600' to 8500' is $11

So the jumper would ask for 7500 ft