VTOL Issues

[TopQuark]

I seem to be haveing some problems getting a VTOL running. Not because of balance issues, but one of the two engines always fails! I've rebuilt the plane several times, and each time, one of the VTOL engines on either wings just flames out for appearantly no reason. I'm not really familiar with the game's air flow logic, but it seems like it shouldn't be happening.

 

The engine on the left flames out during spool-up, but the one one the right runs fine

 

Plane side profile

 

Plane top profile

[Red Iron Crown]

Welcome aboard! I think it needs more intake area. Intakes perform their worst at low speed, what is more than enough area in forward flight is often insufficient for near stationary operations like witha  VTOL.

[TopQuark]

4 minutes ago, Red Iron Crown said:

Welcome aboard! I think it needs more intake area. Intakes perform their worst at low speed, what is more than enough area in forward flight is often insufficient for near stationary operations like witha  VTOL.

On a previous design, I had three of those intakes, one for each engine, and the problem persisted. In Scott Manley's VTOL tutorial, I believe he used just two of the long intakes, which didn't work for me either. I'll try covering the thing in intakes, and see exactly how many it wants.

[TopQuark]

Okay, I packed the thing with intakes, and the engines will run without flameing out. It will appearantly run on no less than three wide intakes and five narrow intakes, which sounds wrong to me.

Now, the plane is imbalanced for no reason. It's not my piloting skills, for as soon as I take off, it gravitates towards the right. I checked the engines' readouts, and they're outputting equal amounts of kN, so it has to be a weight issue. However, the CoW/L indicators in the AB look fine.

 

[Newpossum]

Pardons if this is a dumb suggestion, but could it be torque?

[TopQuark]

9 minutes ago, Newpossum said:

Pardons if this is a dumb suggestion, but could it be torque?

I don't see where any imbalanced torque could be coming from. The only things with gyros are the cockpit and two reaction wheels on either side of the fuel tank. Though, I'm not really familiar with planes in the game, so it could be that something wierd is happening with the torque.

[Rocket In My Pocket]

I waste a lot of time designing VTOL's for fun (but never profit!) from the super tiny, to the insanely large. 

Drifting to one side could be indicative of a lot of things, the engines could be tilted at a slightly different angle, wings bending at the root could be a problem as well.

Could you upload the craft file maybe? It'd be so much easier to help if we could get our hands under the hood, so to speak.

[Geschosskopf]

15 hours ago, TopQuark said:

Okay, I packed the thing with intakes, and the engines will run without flameing out. It will appearantly run on no less than three wide intakes and five narrow intakes, which sounds wrong to me.

Now, the plane is imbalanced for no reason. It's not my piloting skills, for as soon as I take off, it gravitates towards the right. I checked the engines' readouts, and they're outputting equal amounts of kN, so it has to be a weight issue. However, the CoW/L indicators in the AB look fine.

In case you don't know, the order in which you attach intakes and engines to the ship matters a lot, due to the way the craft file is organized.  If you attach all the intakes and then all the engines (or vice versa), then the craft file will have them listed that way.  This means the 1st engine on the list will hog all the air from all the intakes and the other engines will get less than their fair share.  If one of the other engines has just enough air to run but not at full power, then you get asymmetrical thrust.  If an engine ends up with no air, then you get asymmetrical flameouts.  Therefore, it's always good practice to add an intake, add an engine, repeat.  That way, each engine will draw from the intake listed next to it in the craft file and should run OK.

I'm thinking you're running into this problem.  In the beginning, you had 1 engine hogging all the air so the other flamed out.  If you didn't rearrange the existing planes but just added all the additional intakes to it, then the 1st engine was hogging most of the new air and only when you got an excess amount did the other engine run, but not at full power so you have asymmetrical thrust.

Due to the need for mirror symmetry of the engines, it's hard to build intakes and engines sequentially with VTOLs. with multiple lift engines out on the wings.  About the only way I've found is to make a subassembly of an intake/engine pair, then attach such subassemblies with symmetry and use the offset gizmo to position them where I want them.  I find it a lot easier to put the lift engines under the fuselage, so I can add them 1-at-a-time mixed in with adding their intakes.  Even better is to use only a single lift engine if you possibly can.  Not only is this the simplest technically, it also means the horizontal engine has less dead weight to push around in flight.

BTW, if you're serious about VTOLs, I suggest you try @allista's wonderful "Throttle Controlled Avionics" mod.  This really helps with flying the things.

 

 

[bueskyd]

Try using the Engine Nacelle, it has a very powerful Static suction, and works great with VTOL's. I've never had any problems with VTOL's after I began using it.

[SR]

Jet flameout is always caused by lack of intake air or fuel.

check that fuel gets to the engines properly

[Wanderfound]

It's all about the static suction.

Look at the details of the intakes: the ones with a high static airspeed (nacelles, intercooler, circular intakes) are the ones you want for a VTOL. Ram-style intakes (ramscoop, shockcone, structural, supersonic radial) don't work well for hovering, 'cos you ain't ramming them when you aren't moving.

Edited April 11, 2016 by Wanderfound

[Vegetal]

As others have said, you have to use the best intakes for this specific job, which are the nacelle and the precooler.

I just made a X-men plane replica in FAR (lol), it has 2 wheesleys and 4 junos for vertical flight, and needs 4 precoolers. So yeah, you need lots of static suction for VTOLs.

[Redshift OTF]

For some reason the Wheesley's need more than one radial intake each to stop flame outs when stationary when they are at full power, (i.e 3 radial intakes for 2 Wheesleys).

 

As for your balance problems, right click on the back engines and reduce thrust to zero to see the CoL for just the VTOL engines. If that doesn't help upload a craft file and I will take a look at it. You might just need some more reaction wheels.