Single engined VTOL!

[hempa2]

Im quite used to VTOLs, i landed on the helipad a few times but only with 2-4 engined crafts. All my single engined VTOLs do backflips and spazz out.

[ScopusAurelius]

Is your thrust lined up vertically with your center of mass? If you're spazzily back-flipping, it sounds like the mass is behind your lift.

[hempa2]

They are perfectly lined up

[Claw]

Pictures always help.

I'm inferring that your craft is smaller if it is single engine. So my first blind guess is that you are using the standard landing gear bay. If that's the case, then the CoM marker is lying to you. And with a small craft the difference can be significant. Generally speaking for most typical airplanes, the small gear bay causes the CoM to display too far forward. That would cause the craft to flip backward if your CoM and CoT are lined up.

The reason why is because in-flight, the landing gear is massless. In the VAB/SPH, the gear has mass which causes the CoM to move. Take off the landing gear and see where the CoM is.

Also make sure you have at least some torque on your craft to help control.

[Hodo]

They are perfectly lined up

They can't be if your craft is flipping out.

[Sirrobert]

It could be your fuel tanks draining and shifting center of weight

[hempa2]

Pictures always help.

I'm inferring that your craft is smaller if it is single engine. So my first blind guess is that you are using the standard landing gear bay. If that's the case, then the CoM marker is lying to you. And with a small craft the difference can be significant. Generally speaking for most typical airplanes, the small gear bay causes the CoM to display too far forward. That would cause the craft to flip backward if your CoM and CoT are lined up.

The reason why is because in-flight, the landing gear is massless. In the VAB/SPH, the gear has mass which causes the CoM to move. Take off the landing gear and see where the CoM is.

Also make sure you have at least some torque on your craft to help control.

I use SAS units and even RCS to keep stable, my craft is heavy

It could be your fuel tanks draining and shifting center of weight

I can make a system to make it work

[Claw]

I use SAS units and even RCS to keep stable, my craft is heavy

I can make a system to make it work

Okay. If you could provide pictures then, that would help. It's quite hard to guess why you might be having problems when we have no idea what it looks like. That would keep us from making wild guesses.

[Sirrobert]

Well, this is all the help we can give you without pictures.

Guessing likely problems

[Jesrad]

It could be your fuel tanks draining and shifting center of weight

This.

The "simple" way around that is to have a single tank, or a single tank per engine, and have the center of mass of this tank or set of tanks lined up exactly at the center of mass of the rest of the craft.

[SpenSpaceCorp]

As claw said, the landing gear bays are massless when in flight, but they still affect the CoM marker in the SPH/VAB.

Try removing the gear bays and then lining up the CoM/CoT, then add the gear bays back on.

Also, here is a list of other "massless" parts, similar to the gear bay: http://wiki.kerbalspaceprogram.com/wiki/Massless_part

Hope that helps!

[Mesklin]

Im quite used to VTOLs, i landed on the helipad a few times but only with 2-4 engined crafts. All my single engined VTOLs do backflips and spazz out.

Off your engine and close intakes as fast as possibly after touch surface, it should help

[hempa2]

As claw said, the landing gear bays are massless when in flight, but they still affect the CoM marker in the SPH/VAB.

Try removing the gear bays and then lining up the CoM/CoT, then add the gear bays back on.

Also, here is a list of other "massless" parts, similar to the gear bay: http://wiki.kerbalspaceprogram.com/wiki/Massless_part

Hope that helps!

Thanks, it works now!

[Claw]

As claw said, the landing gear bays are massless when in flight, but they still affect the CoM marker in the SPH/VAB.

Try removing the gear bays and then lining up the CoM/CoT, then add the gear bays back on.

Also, here is a list of other "massless" parts, similar to the gear bay: http://wiki.kerbalspaceprogram.com/wiki/Massless_part

Hope that helps!

Yes, thank you.