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Create Aeronautics: the propeller spins but the ship won't move

Seeing a second, ghost set of sails? Don't re-assemble that bearing or rebuild its rotor: players report the ghost sails can collide with the real ones and destroy the ship. Read this first.

The short answer

A ship moves only when three things are all true at once:

  1. The rotor is assembled on the bearing. The sails have to be turning as one moving piece, not sitting there while the bearing spins.

  2. The bearing is part of the ship. A bearing that stayed behind in the world is spinning against nothing.

  3. Thrust is above zero. Real sails, spinning, in air thick enough to push against.

A spinning propeller tells you none of these for certain. Neither does a healthy-looking Thrust figure in your goggles. The one thing that shows whether a bearing is actually pushing the ship is the Contraption Diagram (Step 4). Work through the steps below.

A few terms first:

  • Contraption: Create's name for a group of blocks that moves together as one piece. A spinning propeller is a small contraption.

  • Ship: the whole build after the Physics Assembler turns it into a physics object that can fly.

  • Rotor: the blocks attached to the front face of the Propeller Bearing, the part that spins.

Checked against: Create Aeronautics 1.3.2, Sable 2.0.5, Create 6.0.10.

On this page

Applies to Create Aeronautics 1.3.2, Sable 2.0.5 and Create 6.0.10, on Minecraft 1.21.1 and NeoForge 21.1.248: the versions FTB Skies 2: Aero 1.10.0 ships.

Step 1: before you touch anything

Answer these two questions first. Some fixes on this page make these cases worse.

  1. Can you see a second, ghost set of sails on or around the propeller? Go to Known limitation: bearings stop pushing after a relog now, whatever your goggles or diagram show. Do not re-assemble that bearing, or rebuild its rotor, before you read that section. Players report that re-assembling a bearing while ghost sails are showing can make them collide with the real ones and destroy the ship.

  2. It flew before, and stopped after you left and rejoined the world or server, or flew far away and came back: go to Known limitation: bearings stop pushing after a relog. That is a bug, not your build. Don't keep re-assembling the bearing first. The section explains why.

  3. Neither, or you're not sure: go to Step 2.

Step 2: is the propeller spinning?

It is spinning: don't right-click it. On a healthy bearing, a right-click stops it. Go to Step 3.

  • If you already right-clicked a spinning propeller and nothing happened, go to Known limitation: bearings stop pushing after a relog. A right-click that does nothing on a spinning bearing is that bug's reported symptom.

  • If a propeller is still spinning right after you assembled the ship, it was probably left out of the ship. Assembly stops every bearing it takes in. Go to The bearing was left behind.

It is not spinning: right-click the Propeller Bearing to start it. If you assembled the ship since it last ran, this is expected: every bearing on a freshly assembled ship starts stopped (why).

  1. It starts: go to Step 3.

  2. It refuses, with a message about sail-like blocks: go to The bearing says there are no sails.

  3. Nothing happens: go to Step 4 and check with a Contraption Diagram. One form of the relog bug leaves the propeller still, with no particles, and a right-click that does nothing (end state B). The sources describe no other cause for a stopped bearing ignoring a right-click.

Step 3: put on goggles and read the running bearing

Wear Engineer's Goggles and look at the Propeller Bearing. Aviator's Goggles work too: they show exactly the same tooltip.

While the bearing is running, the tooltip shows Thrust and Airflow. The readout only appears while the bearing is running. A stopped bearing that shows nothing is normal.

What the two numbers mean:

  • Airflow is the propeller's top speed, in m/s. More sails or a faster rotation raise it. Altitude does not change it.

  • Thrust is the push the propeller is working out right now. It already includes two penalties: thinner air higher up, and how fast the ship is already moving along the propeller's axis. As that speed gets close to the Airflow figure, Thrust falls steadily to zero.

If you have read about a Can lift readout elsewhere: that line only appears on the Gyroscopic Propeller Bearing. A normal Propeller Bearing never shows it.

Now find your case:

  1. Airflow is 0: the rotor is not turning. Check that the bearing is getting rotation. If it is, check the pack's airflow setting (The whole pack feels weak). If both are fine, go to Step 4.

  2. Thrust is near 0, and the ship is moving in the direction this propeller pushes: this can mean the ship has reached this propeller's top speed. That is working as designed. See The ship stops speeding up. If the ship is drifting sideways or falling, this does not apply to a lift propeller. Go to item 3 or 4.

  3. Thrust shows 0: on Aeronautics 1.1.0 and later your sails are not the cause. A running bearing already has at least 2 counted sails, and sails can make thrust low but never 0. Check these, in order:

    1. Height. Air pressure fades over the top 40 blocks of the world and is zero at the very top (y=320 in a standard Overworld). See The ship climbs, then levels off.

    2. The pack's thrust setting is 0. See The whole pack feels weak.

    3. Neither: go to Step 4.

  4. Thrust is above 0, whether it looks low or healthy: go to Step 4.

Step 4: check whether the bearing is pushing, with a Contraption Diagram

The Contraption Diagram shows the forces the server is actually applying to your ship. It is the most reliable check on this page, because it doesn't depend on what your game draws.

If you have seen ghost sails, don't rely on this check. Go to Known limitation: bearings stop pushing after a relog. With ghost sails, the diagram can look normal (see end state C).

Make one: craft Paper and a Physics Assembler together, shapeless (any arrangement in the crafting grid). That is the mod's base recipe. A modpack can change it.

Place it:

  1. Place it on a block face on the ship, like a painting.

  2. Right-click it to open it.

If you place it off the ship, it says: "This Diagram must be on a Simulated Contraption to be inspected...". Move it onto the ship.

First: count everything that pushes

  1. On the diagram screen, click Configure Diagram (the forces icon, top-left). A panel slides out with one tab per force type.

  2. Find the Propulsion tab. It shows a live count of pushing forces the server is applying right now. The count is still there, greyed out, even if Propulsion is hidden.

  3. Count every block on your ship that can push. Each of these adds to the count while it is pushing. Each bearing adds exactly 1; for the others, how much each one adds has not been confirmed:

    • Propeller Bearing (Aeronautics)

    • Gyroscopic Propeller Bearing (Aeronautics)

    • Andesite Propeller, Wooden Propeller and Smart Propeller (Aeronautics)

    • Encased Fan (Create; Sable is what counts it), while it is spinning with air in front of it

    • Nozzle (Create; Sable is what counts it)

  4. Compare the two. If the count is higher than your list, or you aren't sure your list is complete, use the Separate arrows (set up below) to check that each Propeller Bearing has its own arrow.

Count all of them, not only the bearings. If a ship has a fan or a small propeller, a dead bearing can hide behind a count that seems to match your bearings.

Pushes too weak to register are not counted, and nobody has established how weak that is. So a healthy bearing can drop out of the count when its thrust is close to 0: near the top of the world, where the air runs out, or when the ship has reached that propeller's top speed. Either one makes the count lower without anything being broken.

Then: set up the arrows, to see which one is missing

Settings are saved on the diagram itself, for every player. If someone else placed or changed this diagram, don't assume the defaults. On the Configure Diagram panel:

  1. Make sure the Propulsion tab is shown. Clicking a tab shows or hides that force type.

  2. Set Force Arrows to Separate. Merged groups arrows into clusters, so you can't tell which bearing is missing one.

  3. Show Gravity. It is hidden on a new diagram, and item 1 below compares your arrows with it.

Propeller bearings and propellers only ever show under Propulsion, never Lift, whichever way they point. Sails fixed to the hull, or to a moving part that isn't a propeller, show under Lift.

On a brand-new diagram, Propulsion, Lift, Balloon Lift and Levitation are shown; Gravity, Drag and Magnetic are hidden; Force Arrows is Separate; Center of Mass is hidden. Each arrow is labelled in pN. The panel also shows the ship's mass.

Find your case

  1. The Propulsion count matches everything that pushes, but the arrows are small next to the Gravity arrow (turn Gravity on first, step 3 above): the ship is underpowered, or high enough that the air is thin. See The ship climbs, then levels off for how to add lift.

  2. The count matches, but Propulsion arrows point against each other, or push the ship into the ground: see The ship pushes the wrong way, or not at all.

  3. The count is lower than everything that pushes: at least one is not pushing the ship, or is pushing too weakly to be counted. Use the arrows to find which. The diagram doesn't say why. If the one missing is a Propeller Bearing, check it in this order:

    1. Is it spinning? If not, go to Step 2 and start it. If you came here from Step 2 because right-clicking it did nothing, skip to check 4.

    2. Walk back to where you built the ship. If a bearing is still standing there, go to The bearing was left behind.

    3. Did the goggles show Thrust near 0 or very low for it? It may be too weak to be counted. The threshold is not known. Which case you are in:

    4. The ship flew before, and right-clicking the bearing does nothing (a healthy bearing starts or stops when you click it; if yours stopped, right-click again to restart it): go to Known limitation: bearings stop pushing after a relog. Flying far away and back, or the ship leaving simulation distance on a server, have also been reported to cause it, so you may not remember a relog.

    5. None of these: our sources don't cover this case. Go to item 4.

  4. None of these fits: this page doesn't cover your case. Some reports nobody has explained yet are listed under What is known, and what isn't; compare yours with those.

Sources for the diagram: Simulated (Aeronautics suite 1.3.2) item simulated:contraption_diagram, its base recipe, lang text, force labels, Configure Diagram panel, force counts, defaults and saved settings (Delve). What adds to the Propulsion count, the noise cut-off, and bearings never recording as Lift: Aeronautics and Simulated at commit b9cb3a8, Sable mc1.21.1-2.0.5-neoforge (Delve). Not established: the size of the cut-off.

The bearing says there are no sails

When you can see the sails and the bearing still counts 0, check the glue first. The rotor needs Super Glue. Honey Glue does not hold it.

What you see: you right-click the Propeller Bearing and it refuses to start. The message reads:

Attached structure does not include enough sail-like blocks: 0
A minimum of 2 are required

The wording is Create's text (Create 6.0.10), so a Create update alone could change it. The check that shows it, and the minimum of 2, belong to Aeronautics.

There are two causes in the sources: the sails are held on with Honey Glue, or the blocks are not sails. Glue first.

Why it happens

Aeronautics has two kinds of glue, and they are read by two different things.

  • Super Glue is Create's glue. When you right-click a Propeller Bearing, it builds an ordinary Create contraption from the blocks on its front face. An ordinary Create contraption follows Super Glue, slime and honey blocks, and blocks that attach naturally. Nothing else.

  • Honey Glue belongs to the ship side of the mod. Only the Physics Assembler reads it, when it turns your build into a ship.

The bearing never looks at Honey Glue. Sails held on with it are not part of the rotor, so the bearing counts zero sails. The mod's own Ponder scene says the same: Honey Glue "does not attach to animated Contraptions" and "exclusively attaches to Simulated Contraptions".

The rule to remember: Super Glue for the spinning parts, Honey Glue for the ship.

Fix

  1. Hold the sails onto the bearing's front block with Super Glue.

  2. Make sure at least 2 of those blocks count as sails (see the list below).

  3. Right-click the Propeller Bearing.

Honey Glue on the rest of the ship is fine. Keep it. Once fixed, this does not come back.

What counts as a sail

A rotor needs at least 2 sail blocks, or it will not assemble. Every sail block adds thrust. Anything else adds weight and nothing more.

Counts as a sail:

  • Windmill Sail Frame, even with no cloth. It gives the same thrust as a full sail.

  • Windmill Sail and its coloured versions (Red Sail, Light Gray Sail and so on).

  • Any wool, any colour.

  • Symmetric Sail and its coloured versions (Red Symmetric Sail and so on).

  • A Copycat Panel holding wool.

Does not count:

  • Any carpet.

  • Envelope blocks.

  • A Copycat Step holding wool, and every Create: Copycats+ shape holding wool. The game judges these by the copycat block itself, not the wool inside, so they give zero thrust. The Copycat Panel is the only copycat whose contents are checked.

  • Any other block, unless your modpack has added it to the sail list (the create:windmill_sails block tag).

If you're on Aeronautics older than 1.1.0: wool in a Copycat Panel raised the bearing's stress there but gave no thrust. That was fixed in 1.1.0. Update if you can.

Whether other copycat shapes are meant to be left out is not confirmed by the developers. The code only checks the Copycat Panel, in both Create and Aeronautics.

Sources: Aeronautics 1.3.2 PropellerBearingBlockEntity (assemble(), getSailPower()), SimAssemblyContraption, BearingContraptionMixin; Ponder text simulated.ponder.honey_glue_intro; Create 6.0.10 windmill_sails tag, BearingContraption and lang key create.gui.assembly.exception.not_enough_sails; issues #1177, #454, commit 5aadca7.

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Propellers stop after assembling the ship

Right-click every Propeller Bearing on the ship after you assemble it.

What you see: the propeller spun fine on the ground. You used the Physics Assembler, the ship became physical, and now the propeller is static blocks or won't push.

Why it happens

When the Physics Assembler builds the ship, it stops every running Create contraption inside it and turns those blocks back into ordinary blocks. Your Super Glue is kept. Nothing starts the bearings again afterwards, so every Propeller Bearing on a freshly assembled ship starts stopped.

Fix

  1. Assemble the ship.

  2. Right-click each Propeller Bearing on it.

This happens every time you assemble the ship, not only the first time. It is expected behaviour, not a fault in your build.

A bearing that was still spinning right after assembly was not taken into the ship. Go to The bearing was left behind.

If a bearing won't start after the right-click, go back to Step 2. If it starts and the ship still won't move, go to Step 3.

Sources: Aeronautics 1.3.2 SimAssemblyHelper.disassembleAndAddCreateContraptions(), PropellerBearingBlock.useItemOn.

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The bearing was left behind

The bearing, or the engine driving it, was not glued to the ship, so it stayed in the world when the ship was assembled.

What you see: the propeller spins and the goggles show thrust, but the ship sits still. A Contraption Diagram on the ship shows no Propulsion arrow for it.

Why it happens

A bearing can only push the ship it is part of. The Physics Assembler only takes blocks it can reach through Super Glue, Honey Glue, slime or sticky faces, or blocks that attach naturally. A bearing that was only touching the hull, or connected by a shaft that wasn't glued, stays where it was. It keeps spinning, with nothing to push.

How to tell

  • Walk back to the spot where you built the ship. If a bearing is still standing there, this is your problem.

  • A bearing that kept spinning right after you assembled the ship is a strong sign. Assembly stops every bearing it takes in, so one still running was left out.

Fix

  1. Disassemble the ship.

  2. Cover the whole ship in Honey Glue (or Super Glue), including every bearing and whatever powers it.

  3. Assemble the ship again.

  4. Right-click every Propeller Bearing to start it (see Propellers stop after assembling the ship).

Sources: Sable 2.0.5 BlockEntitySubLevelPropellerActor; Aeronautics 1.3.2 SimAssemblyContraption.moveBlock, SimAssemblyHelper.disassembleAndAddCreateContraptions() (stops contraptions whose controller is inside the ship).

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Known limitation: bearings stop pushing after a relog

What you see: the ship worked before. After you rejoin, or fly far away and come back, it no longer moves, and right-clicking the bearing does nothing.

Three ways it can look

Not everyone sees the same thing. If your bearing doesn't match the first one, it can still be this bug.

  • A. The common case. The propeller spins normally and shows particles. The goggles show normal-looking Thrust and Airflow. The ship gets no push. Right-clicking does nothing.

  • B. The propeller is dead in your game too. It doesn't spin, shows no particles, and the goggles show no Thrust or Airflow lines at all. One report (#426) mentions missing particles, which fits.

  • C. Duplicate sails. A second, ghost set of sails appears (#1263). What the goggles show in this state could not be established from the code. Testing in-game would settle it.

How to confirm it

If you can see ghost sails (C): treat that as the sign. You don't need the diagram. Each bearing records at most one propeller force, so two rotor copies give one arrow or none, never two. Whether the server's bearing is still linked to a copy that pushes could not be established from the code, so the diagram may look normal. Go to the workarounds below, and read the warning first.

Otherwise (A or B): place a Contraption Diagram on the ship and open Configure Diagram (see Step 4). A bugged bearing adds nothing to the Propulsion count and has no Propulsion arrow.

A missing force means "this bearing isn't pushing", not "relog bug". A bearing left behind at assembly shows none either. It points to this bug when it goes with the rest: it worked before the reload, the bearing is on the ship, and right-clicking does nothing.

If that doesn't match, this is probably not this bug:

  • The ship never flew, or the right-click works normally: if your click stopped the bearing, right-click it again to restart it. Then go to Step 2 and work through the page from there.

  • The Propulsion count matches everything that pushes, and you have seen no ghost sails: every bearing is pushing. Go to Step 4, items 1 and 2.

Why right-clicking does nothing

The bearing still thinks it's running, so a right-click asks it to stop. But the spinning rotor it would stop has come loose from it behind the scenes. With nothing to stop, the click silently does nothing.

What is known, and what isn't

  • Confirmed in the code: a bearing only pushes while its spinning rotor exists as a live object on the server. After a reload, if that object is missing, no force reaches the ship. The goggles and the spin you see come from your game's own copy, which can survive when the server's doesn't.

  • Strongly supported by player reports, not confirmed by the developers: mods that skip updating things far from players can freeze the rotor. On three issues, players found that removing a tick-skipping mod fixed the problem. Does It Tick? and DoesPotatoTick are two different mods. Our research didn't record which one each player removed; the issues themselves may say. One player reported a reliable fix by changing DoesPotatoTick's config.

  • Related, motive unknown: the FTB Skies 2: Aero pack excludes the propeller and contraption entities from its own tick-skipping settings (see below). Nobody has said why FTB added them.

  • The likely reason these mods get it wrong: Sable keeps every ship's blocks more than 30 million blocks out in the world's raw coordinates. To another mod, the rotor can look extremely far from every player. This comes from reading the code, not from a developer statement.

  • Not explained: in some reports, nobody has linked the bug to a tick-skipping mod. One says it happens when the ship leaves simulation distance on a server (#904). Another reports bigger contraptions failing to detect forces when loading (#426). There is probably a second save and load bug in Aeronautics or Sable that nobody has pinned down yet.

Workarounds, in order

1. Check for a mod that skips far-away entities.

What to do depends on your pack.

If you play FTB Skies 2: Aero (checked on 1.10.0): Aero includes neither Does It Tick? nor DoesPotatoTick, so don't go looking for them. Aero ships ServerCore, which also skips updating distant entities. Its activation range is on: entities more than 16 blocks from a player only update once every 20 ticks. The pack excludes aeronautics:propeller_bearing_contraption, create:contraption and simulated:honey_glue from it, so that setting is probably not your cause.

The settings are in config/servercore/config.yml. The key names are ServerCore 1.5.19's; the values are what Aero 1.10.0 ships.

  • Activation range: under activation-range:, enabled: true. The range is under default-activation-type: as activation-range: 16 and tick-interval: 20.

  • The exclusions: under activation-range:, in excluded-entity-types:.

ServerCore's dynamic performance is also on in Aero 1.10.0. It can lower simulation distance and chunk-tick distance as far as 2. One report ties this bug to a ship leaving simulation distance on a server (#904), so it is a live lead. It is in the same file:

  • The switch: under dynamic:, enabled: true.

  • The trigger: under dynamic:, target-mspt: 35. There is no TPS setting.

  • The limits: under dynamic:, in dynamic-settings:. The entry - setting: 'SIMULATION_DISTANCE' has max: 8 and min: 2. The entry - setting: 'CHUNK_TICK_DISTANCE' has max: 10 and min: 2.

If the problem continues on Aero, go to workaround 2.

If your pack has DoesPotatoTick:

Add the four mods to its always-tick list, or remove it.

  1. Open config/doespotatotick-common.toml.

  2. Find EntitiesOfTheModsThatWillAlwaysTick.

  3. Add "aeronautics", "simulated", "offroad" and "sable" to it.

  4. Restart the game or server.

If your pack has Does It Tick?: this is a different mod from DoesPotatoTick. We have no confirmed setting for it. Players on three issues found removing a tick-skipping mod fixed the problem, but our research didn't record whether it was this one. Look in its config for an exclusion or always-tick list, or try without it.

If your pack has some other mod that skips updating distant entities: look in its config for an exclusion or always-tick list, and add the Aeronautics entities or mods to it. The setting names will differ.

If your pack has none of these, skip to 2. This may still happen to you, for the unexplained reasons above.

2. Prevention: stop the bearings before you leave.

  1. Before you log out or fly away from a ship, right-click each Propeller Bearing to stop it. The sails turn back into blocks.

  2. When you come back, right-click each one again to start it.

Players report this works. It will not help if the server crashes while the bearings are running.

3. Recovery: when a bearing is already stuck.

Right-clicking will not work at this point.

  1. Break the Propeller Bearing. The sails drop back onto the ship as blocks. Do this before anything else, and before re-assembling the ship.

  2. Place the bearing again.

  3. Attach the sails with Super Glue.

  4. Right-click the bearing.

  5. If the ship won't accept the new bearing, disassemble the ship and assemble it again, then right-click every bearing.

Not the same problem: jittering sails

With the mod EntityCulling installed, sails can jitter and snap back to their starting angle. This is visual only. Thrust is not affected. A community fix exists but has not been merged.

Sources: Aeronautics 1.3.2 PropellerBearingBlockEntity.isActive(), client and server rotor behaviour and the right-click path (Delve); Simulated simulated:contraption_diagram (Delve); Sable 2.0.5 SubLevelContainer; FTB Skies 2: Aero 1.10.0 manifest and overrides/config/servercore/config.yml, 1.9.1 manifest (Beacon); Does It Tick? (CurseForge 543308) and DoesPotatoTick (CurseForge 825355) as separate projects (Beacon); issues #508, #904, #972, #974, #1029, #1263, #1391, #1425, #426; PR #1427; Aeronautics changelog and Sable git log through 2.0.5 (no fix found).

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Working as designed: altitude, speed and direction

These are limits built into the mod. Nothing is broken.

The ship climbs, then levels off

Thrust weakens as air gets thinner higher up. A ship settles at the height where its thrust equals its weight. The same list below is the fix for a ship that is underpowered at any height.

  • In a standard Overworld, air pressure is about 62% of sea level at y=180 and about 42% at y=280.

  • Pressure fades to zero over the top 40 blocks of the world. At y=320 in a standard Overworld, propellers give no thrust at all.

  • An Altitude Sensor tells you the pressure where you are.

  • Packs and data packs can change this curve per dimension, so your numbers may differ.

To fly higher (if you have seen ghost sails, go to Known limitation: bearings stop pushing after a relog instead):

  1. Add sails. Thrust grows faster than the sail count: doubling the sails gives nearly three times the thrust.

  2. Spin the bearings faster. Thrust rises with rotation speed.

  3. Add more bearings.

  4. Make the ship lighter.

The ship stops speeding up

Every propeller has a top speed. The goggles show it as Airflow, in m/s. As the ship's speed along that propeller's axis gets close to the figure, Thrust falls steadily to zero. So Thrust near zero on a ship cruising in the direction the propeller pushes can mean it has reached this ceiling.

This only applies along the propeller's axis. A lift propeller showing Thrust near zero while the ship drifts sideways or falls has not hit its top speed. Go back to Step 3, items 3 and 4.

To raise the top speed (if you have seen ghost sails, go to Known limitation: bearings stop pushing after a relog instead):

  1. Spin the bearing faster. Airflow rises in step with rotation speed.

  2. Add sails. Airflow grows more slowly than the sail count: four times the sails gives twice the Airflow.

The ceiling can also be scaled by the pack's server config (see The whole pack feels weak).

The ship pushes the wrong way, or not at all

  • Each bearing has a scroll setting (its value box, or a wrench) that switches between pulling and pushing when it turns clockwise. Reversing the rotation also reverses the thrust.

  • Two bearings working against each other, or one pushing the ship into the ground, looks like "it won't move". A Contraption Diagram on the ship, with Force Arrows set to Separate, shows which way each Propulsion arrow points.

The whole pack feels weak

Propeller thrust and airflow are server settings (propellerBearingThrust, default 0.2, and propellerBearingAirflow, default 0.05). A modpack can turn them down. Thrust and Airflow are both multiplied by these, so a value of 0 means no thrust or no Airflow at all. If every ship in a pack underperforms, check the pack's Aeronautics server config before rebuilding.

Sources: Sable 2.0.5 DimensionPhysics.createDefault(), BlockEntityPropeller.getScaledThrust() and airflow scaling; Aeronautics 1.3.2 PropellerBearingBlockEntity (getThrust(), ThrustDirection), AeroPhysics server config; Ponder text aeronautics.ponder.gyro_pressure, propeller_bearing_thrust, propeller_pressure.

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