Airship Altitude

Discussion on playing Earthdawn. Experiences, stories, and questions related to being a player.
Telarus
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Re: Airship Altitude

Post by Telarus » Sat Aug 24, 2019 1:20 am

Love this thread. ;D

ChrisDDickey
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Re: Airship Altitude

Post by ChrisDDickey » Tue Aug 27, 2019 12:05 am

I like this thread too, and thought of more antidotes to illiterate points which GMs might want to incorporate.

Non-pilots assume that lower is safer. That is almost never true. 100 feet of height is more than enough to kill you if you fall or crash. You are not more dead, or even more likely to be dead if falling from 10,000 feet than from 200 feet. You just have less time to figure out how to avoid dying. Remember, so long as you are still in the air, you are still alive. It is crashing into the ground that kills you. Being farther away from the ground is safer.

If a Cessna (typical small single engine aircraft) looses power, the procedure is to first establish your non-powered glide, then quickly figure out where you want to attempt your emergency landing and start heading in that direction, then attempt to restart the engine. If an aircraft loses power/control at 200 feet of height, than it will be crashing into whatever is directly in front of it in mere seconds. There is no time to do anything. At 2000 feet the pilot has about 3 minutes to get the engine restarted and a choice of about a 3 nautical miles radius as to where to attempt the emergency landing. At 12,500 feet it would have about 18 nautical miles of glide radius, and about 18 minutes in which to restart the engine.

If a plane stalls at 200 feet, it hits the ground and everybody aboard probably dies. If a plane stalls at 2000 feet, the pilot recovers and the flight continues. Higher is most definitely safer.

I think the same could probably be said about airships. Lets say "something goes wrong, and the ship is plummeting". Does the crew want to be at 1000 feet, and have one chance to fix the problem? Or at 2000 feet and have two chances to fix the problem? Or at 12,000 feet and have 12 chances to fix the problem? Higher should be safer, and the ship does not die until it hits the ground.

The comment that ships should stay close to the ground to avoid bad weather and strong winds is also actually not as true as non-pilots would assume. One of the three causes of turbulence (terrain features, storms, wind interfaces) is most likely nearer the ground (terrain features). I remember once I was flying at a bit higher than 1000 feet height above ground, with about a 20 knot tailwind. Without thinking about it, I passed over a line of hills, maybe about 200 feet high. I felt this was no big deal, since I was still well over 800 feet above the hills. Now as many, many diagrams in aviation books has illustrated, When a wind intersects a hill, the wind gets pushed up. I rapidly went from flying in air that was steadily moving 20 knots in the same direction I was, to air that was moving at an up angle, to air that was moving at a down angle, then sideways, etc. I had some earphones clamped to my head that ended up, not in the back seat, but in the cargo compartment behind the back seat. I should have climbed up higher above those hills.

Mataxes has an excellent point about wind catcher however. If your parachute analog only works at Rank x 100 yards height above ground, and baring in mind that that people do occasionally fall out of the rigging and/or over the side, then staying withing 500 or 1000 yards of the ground where practicable seems a prudent thing to do. Then at least the most experienced officers and crew have a chance. The question is whether the Wind Catcher limit outweighs any other factors that might argue for a higher altitude.

I am reminded that in ancient times, ships would always stay near the coast for navigation purposes. If you could not see land, you could not be certain where you were. And being near the coast, while actually more dangerous to the ship, "felt" safer to the crew.

Sharkforce
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Re: Airship Altitude

Post by Sharkforce » Tue Aug 27, 2019 2:56 am

i'm not entirely certain that in situations where an airship would be crashing, gliding would be an option. on account of them being shaped like ships rather than being shaped like something that would naturally fly (this would of course be even more true in a theran vessel, considering that they are almost literally magical flying bricks).

i suppose you might have a little bit longer to attempt to get the ship flying again if you're at high altitude (because again, i don't consider a controlled landing to be an option without a functioning airship), but unless you've got the world's fastest-working enchanter on board it seems improbable. i'd expect the bigger worry is from ground-based namegivers in regular travel situations; you want to be high enough that bandits aren't going to be able to reach you with ranged weapons, for example.

in combat, i would expect that higher is better, as it adds extra protection (it's harder for enemies to shoot a projectile upwards, and it's harder for people to jump upwards and impossible to use talents to glide upwards) and attack power (your own projectiles will gain power the further down the target is, and even a rock pushed over the side can be deadly if you manage to hit your target with it - which is not an easy task).

of course, some amount of height will likely also benefit navigation (you can see more of your surroundings, and have a better chance of noticing prominent landmarks) and gives you more time to react to another flying opponent as well (if a group of windling air pirates come after you on flying mounts, being 1000 feet up means you have more time to evade than if you're only 100 feet up).

incidentally, given that the rules for airships have never mentioned wind speeds being a major point that i can recall, i have generally assumed that something about the enchantments on airships mitigates that factor to a large extent. (possibly the reason irl would be that the developers were not pilots or air traffic controllers or anything like that and thus did not consider it, but the in-game reason would presumably be different :P )

ChrisDDickey
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Re: Airship Altitude

Post by ChrisDDickey » Tue Aug 27, 2019 9:51 am

Yes, gliding, per see, would not an option, but I would assume that similar situations would arise where a ship looses control, or looses a portion (but not all) of their lift. The rigging gets tangled or damaged. Various important things (rudders, etc) get damaged or fall off. Something goes wrong with the enchanting, or the true elements. For Therian ships, maybe a lot of your slaves have suddenly died, and the life force left in the remaining ones is not enough to give you full lift/control.

Maybe the ship is just bobbing around uncontrolled, but the wind is sweeping it towards a mountain, or a downdraft is causing it to sink. Maybe the ship is falling, but fairly slowly, and with some measure of control. In all of these situations, I assume there is "Something" the crew could do or fix, if they just have time to do it.

I agree that it does simplify things a lot if wind speed and direction gets taken out of the travel speed calculation. It actually could almost be necessary for sailing airships. Wind powered water ships sailing close to the wind works because of the interaction between the keel in the water and the sails in the air. Having nothing for the keel to push against makes sail powered airships a pretty dubious proposition (for sailing any direction other than directly downwind of course). So if you assume that the keel in some way magically interacts with the ground far below, it would allow airships to sail close to the wind (which is actually pretty advanced sailing - It was very poorly done until just a few centuries ago, and the physics of it were only worked out in the last two centuries).

The thing to worry about navigation is an overcast. Being over and overcast makes celestial navigation really easy, but landmark navigation impossible. If under the overcast, the opposite is true.

Scherme
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Location: Western Massachusetts

Re: Airship Altitude

Post by Scherme » Tue Aug 27, 2019 2:58 pm

This is awesome.

With complexity comes options.

Need to keep your players grounded? Sorry, this ship will not embark until winds become more favorable.
In a rush to move your players along? Great! We just grabbed an excellent tailwind, we are ahead of schedule.
Need to divert course? Unfortunately the crew were not skilled enough/equipment malfunctioned and we were blown off course by rogue winds, now we have to set down for the night over.. there!
And so on and so forth.

It's not railroading, its story driving.
In a perpetual state of lore overload.

Michael
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Re: Airship Altitude

Post by Michael » Tue Aug 27, 2019 3:34 pm

well imho, it's an Air SHIP not a Air PLANE.

I recall somewhere in 3rd ed that the Law of Similarities apply. Magic says you claim it's a ship that flies, it's still a ship and acts like one. Therefore, I think airship are indeed more susceptible to rough weather/high winds (seas) and the like. Higher altitude is colder thinner air, farther from the ground in case something happens and I would think airships drop out of the sky pretty quick when there's a problem.

Also, as I recall from somewhere in the books, there is a min amount of Air Sailing talent/ranks required to keep the boat in the air. IN combat, you lose too many of these people you might have a problem.

Currently in my 4th ed game, airships (smaller ones) run 16 hours then moor to the treeline or near mountains for the night. This is because of a smaller crew, lack of being able to see long distances at night, Large predators that although might not sink the ship, can do some serious damage.

thoughts?

Altanius
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Re: Airship Altitude

Post by Altanius » Tue Aug 27, 2019 4:00 pm

Michael wrote:
Tue Aug 27, 2019 3:34 pm
I recall somewhere in 3rd ed that the Law of Similarities apply. Magic says you claim it's a ship that flies, it's still a ship and acts like one. Therefore, I think airship are indeed more susceptible to rough weather/high winds (seas) and the like. Higher altitude is colder thinner air, farther from the ground in case something happens and I would think airships drop out of the sky pretty quick when there's a problem.
Sure, but terminal velocity is still a thing. At higher altitudes, you'd still have time to react.
Michael wrote:
Tue Aug 27, 2019 3:34 pm
Also, as I recall from somewhere in the books, there is a min amount of Air Sailing talent/ranks required to keep the boat in the air. IN combat, you lose too many of these people you might have a problem.

Currently in my 4th ed game, airships (smaller ones) run 16 hours then moor to the treeline or near mountains for the night. This is because of a smaller crew, lack of being able to see long distances at night, Large predators that although might not sink the ship, can do some serious damage.
There is a minimum number of successes required on air sailing tests (versus a TN of 5) to keep the Air ship in the air and moving. By default that number is equal to 25% of the crew. So a skilled crew probably wouldn't have much trouble keeping the ship in the air unless they've suffered heavy casualties and they could probably travel at night if they wanted to.

Low Light vision is stated to be excellent even at night, with full cloud cover providing visibility equal to a human at dusk, so I don't think seeing long distances at night would really be a problem. Even if it was, being a couple hundred feet off the ground makes it a non-issue, since there's not much to run into other than mountains (which you could see in anything other than pitch blackness.)

ChrisDDickey
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Re: Airship Altitude

Post by ChrisDDickey » Wed Aug 28, 2019 2:29 am

Yes, the 3rd edition RaW (game masters companion) is that a head wind or tail wind only imparts a -1 or +1 to a ships ground speed. This seems to imply that only a small percentage of the force of a typical wind is effecting the ships speed. It is up to the individual GMs of course, but the explanation for this has to be "it's a magic ship, it's weird magic"

And it does state that most ships, with standard number and quality of crew, do travel 16 hours per day, and tie up for 8 hours per night while the crew sleeps. I would think that you would need a crew half again as big (or half again as skilled) to routinely travel all night, so that you always have a standard sized crew on duty. And of course some of the crew would need to have low-light vision. The races with low-light vision are not known for their air sailing. They are not unknown of course, just not the most typical. But of course any crew that is running 16 hour days is still doing 4 hours or so of flying at night.

And it seems to me that a ship that is low to the ground, only needs one hourly crew airsailing test blown to end up crashing. One that is high enough needs to totally and completely tank 3 or 4 hourly tests before it crashes.

Avanti
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Re: Airship Altitude

Post by Avanti » Wed Aug 28, 2019 2:51 pm

This is a great thread!

Here is my take, although I've started GMing Terror in the Skies just now, so not much experience in the matter :)

I lean heavily on the Law of Similarity when I think of Airships - they behave mostly like a sea-faring vessel - i.e if it keels over, it sinks. There is no saving it no matter how high it was. What can cause a ship to keel over? On seas: high winds & waves - in air: rouge winds that go not only N/W/E/S but UP/DOWN as well.
Furthermore Airship treats air like water. We know that higher up = less air. So holding the Law of Similarity firmly in hand it stands to reason the higher it is, the more trouble the ship has staying "afloat" as there is less "water" supporting it. I would say that anything above 4km (14k feet) makes it more difficult for Airships to fly in. Why that attitude? Simply to avoid complications with oxygen and extreme cold. 4km is about 25*C colder than at sea level. Gathering true air happens "high in the sky" you say. Well "high in the sky is a very relative term. Let's look at other common circumstances where true air can be gathered - storms. Typical storm clouds have their base at around 2-3km and can strech up to 10km- which gives plenty of vertical space to gather the element. More experienced crew, that is accustomed to high attitudes can reach higher, 4.5 - 5km up, having to constantly counter the slow "sinking" but probably finding more true Air in return. This also means that you can probably find true air on the peaks of highest mountains in Barsawie.

I have never considered Airships tying down for the night as normally sea faring vessels do not anchor for the night unless a convenient place presents itself (like a port). Since only 25% of the crew is needed for the ship to operate (assuming everyone gets only 1 success) a fully crewed ship has 4 shifts of sailors - so 3 working 8 hour shifts and one spare (maybe that one spare is actually non-sailor but rather support/combat crew). Why would they ever stop before they reach destination, banning bad weather? All it takes is having a number of Orks or Elves in the crew to act as your radar :) But flying at 1km up, as long as you know where your mountains are, you are rather safe from crashing into anything.

So IMB, Airships fly at at any attitude that is convenient but stay below 4km mark. Fully crewed ships do not stop for the night, but obviously working night-shift is less desired.

ChrisDDickey
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Re: Airship Altitude

Post by ChrisDDickey » Thu Aug 29, 2019 1:36 am

It is not correct that only 25% of the crew is needed for the ship to operate. Read the Air Sailing talent more carefully. A number of successes equal to 25% of the ship types listed crew complement must be generated in an hour long test each and every hour for the ship to stay airborne. It requires 50% to actually maneuver (ie: make forward progress in the direction intended).

So if the plan is making forward progress each and every hour of the day, the captain needs to plan on generating at least 50% successes, not just 25%. And each hour that he did not have enough crew working to achieve the 50% success level, no forward progress is made. And each time the 25% success level was failed, the ship would crash.

My understanding of an airship crew is that typically a high percentage of them are probably not adepts, and have the air sailing skill, rather than the talent. Also, the 25% success rule is practically identical from 2nd edition, back when each karma you bought required you to spend LP. So nobody was probably routinely spending a karma every hour, all day every day. So considering that most of the crew can't spend karma on the test, and when the rule was written, even the adepts would never be spending karma on the test except in combat circumstances, some of the crew failing the test would be fairly common, and extra successes would be somewhat rarer. Now that karma is free every day, adepts can spend it on their air sailing tests every hour, but I think many would save it for when it was truly important.

I am not going to work out the exact math or probabilities since it depends upon the crew complement. Obviously a crew composed solely of journeyman air sailors could operate with fewer people than a crew of who all knew only one rank of the air sailing skill. But assuming most of the crew were common sailors with 1 or 2 ranks in Air Sailing, leavened with some more experienced sailors, to give the crew average skill of step 8, with nobody routinely spending karma on the task.

A Galley has a recommended crew size of 100, if it divided it's crew into 4 watches of 25 each, each, with one watch on duty at a time , it would need 50 successes to maneuver, and 25 just to remain aloft. It would fall out of the sky more often than made any forward progress.

If it had 3 watches of 33, each working one at a time, it would do better, but still not go forward many hours, and fall out of the sky pretty frequently.

Assuming you have crew that don't mind 16 hour days (the rules as written seem to make that assumption), the most efficient division for 24/7 operation is 3 watches of 33 each, with two on duty at any one time. That gives you 66 on duty at any one time. Assuming even modest skill levels, that should leave you making forward progress most hours, and almost never have a catastrophic failure. But you are still significantly more likely to have a catastrophic failure than if you had 100% of your crew on duty for 16 hours.

I would also ask what is the actual results of not generating the 25% necessary to remain airborne. A strict reading of the sentence would seem to indicate that the ship plummets, and no matter what it's height was, it crashes into the ground before the crew can do anything about it. It seems to me that this really ought to be height dependent. Maybe the ship looses 2000 feet of height that hour, maybe it looses 5000. Maybe it does fall to the ground no matter what it's height. But in any case, if failing the test at the 25% threshold would cause the ship to hit the ground, then this is a test that a ship can't afford to fail, not even once.

As gamers, we are all pretty familiar with probability distribution. If there is a 1% chance each hour of something happening, it will happen about every 4 days. If there is a one in a thousand chance of it happening each hour, it will happen every 40 days. An officer who wants to have a long career needs to set the chance of his ship crashing at less than one in ten thousand per hour. Preferably much less.

I will also point out that the British Royal Navy, back in the days of wooden ships and iron men, divided their crews into 2 watches, with 50% of the crew on duty at any one time in 4 hour watches. If they needed extra men they would call the off-duty watch up to help out. This 12 hours of hard labor per day, with sleep shifts of only 4 hours was considered ruinous to the mens health, and 40 year old sailors were often mistaken for 60 year olds.

It is also not entirely true that sailing and rowing ships did not routinely anchor for the night. Ships that boldly set sail far from land is a common phenomenon only in the last half millennia (not unknown prior to that, but less common). Many ships were day sailing coasters, creeping along the coast and anchoring almost every night. Again, this was only safer for the ship because of inability to navigate out of sight of land made that more dangerous. Also, it felt safer for the crewmen, who would rather have the ship wrecked on the rocks near shore than be lost far from land.

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