Kev T said:
why some operations entail jumping from around 12,000 while others at anywhere from 20,000 - 40,000; does it have to do with the climate and weather or where one is jumping into e.g. mountains, etc or does it have to do with tactical considerations like radar, etc?
First off, little things like climate, weather, and mountains ARE tactical considerations...especially for jumping.
Jumping in mountainous terrain, for example, provides for thinner air (you land....no, assault the earth, harder), plus there always seems to be bitchin' mountain cross-winds. If you have the opportunity to use check streamers after determining your exit point, they will likely be 90 degrees off where you think they should be - - thus, use your team members as confirming "streamers" before you jump
Your choice of parachute insertion method is just another tool in the toolbox. In general, standard airborne mass-jumps allow you to put large numbers of troops onto a tactically significant objective (bridges, choke-points, cross-roads). You can train large numbers of such troops in little time ("go out the door, turn left"). Traditionally, paratroops have been considered high-speed because they rely on audacity and initiative, since they may have to wait a significant amount of time for reinforcement/link-up.
MFP skills are more difficult to master; as such, there will never be as many free-fall qualified troops, which means they will only be used to conduct more specialized missions.
MFP, whether HAHO or HALO, provides a stand-off capability, which allows for greater stealth. Given the right circumstances, the troops could exit the aircraft on one side of a border and fly to their objective, reducing the anti-air threat to the aircraft while increasing mission security from not having to overfly the objective. Don't think that paratroops are invisible though. With proper conditions (jumpers' formation, atmospherics, etc - - details will have to come from someone with a more pointy, tinfoil-covered head than me), four jumpers can provide a radar return similar to a C-130.
The jump altitude will depend on the mission requirements, including enemy anti-air capability, and weather conditions (will they need to track [move across ground] in freefall or basically go straight down? Are they required to open shortly after exit in order to fly a greater distance? Are the winds high, requiring a lower exit altitude to reduce target accuracy error?)
On paper, oxygen is required over 10,000 ft. Going to 12,500 feet without O2 is common. I've done a few jumps from 14,500 without oxygen without any problems, although we didn't hang around at that altitude for long.1 A 70-second freefall is an awesome rush
Of course, at the other end of the para spectrum, during the final days of Rhodesia, the RLI occasionally made three combat jumps in a single day....from a jump altitude of 100 metres! Basically, BASE jumping from a moving DC-3.
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1 And those who know me are saying "how could we tell if your brain wasn't getting enough oxygen; would there be any noticeable difference"? :
