Plane not taking off

[KvickFlygarn87]

I've made a plane, or more specifically a dropship. It is absolutely humongous. (Is that how you spell it?) However, it doesn't seem to like taking off? I have FAR, and in the "Calculate stability derivatives", all is green.

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Thank you in advance!

Edited July 7, 2014 by KvickFlygarn87

[Kerba Fett]

Is it possible that when sitting on the runway your nose is low enough to cause a negative angle of attack on the wings? If that's the case you wings would be acting as spoilers and holding you to the runway even after you reach flight speed.

I don't build many planes, but I usually try to mount the landing gear so I have 3 to 5 degrees of pitch when sitting on the runway. Once I turn on SAS and open the throttle I often don't have to touch the controls till well after takeoff.

If moving the gear is too much bother, you could try a few of the linear RCS ports on the bottom of the nose. This might provide enough lift to get your nose up for the takeoff.

[BudgetHedgehog]

I could be wrong but I think the gear under the tail are too far back (none of the angles show them clearly enough. The closest I can see them is this one where it looks like the large majority of your elevons are in front of them).

The elevons deflect the air, but the pivot for your plane is behind them so all they're doing is pushing the plane into the ground. If the gear absolutely need to be there, consider putting RCS thrusters underneath the nose pointing downwards, as Kerba Fett said.

[Kerba Fett]

While moving the rear gear forward so the plane can pivot up on it may work, you also increase your chance of hitting the engines on the runway on takeoff. Since most people fly with the keyboard you're either pulling the controls back fully or not at all so it's much harder to take off without striking the runway with the tail.

What would help a lot would be an extended front landing gear like the concord.

[BudgetHedgehog]

While moving the rear gear forward so the plane can pivot up on it may work, you also increase your chance of hitting the engines on the runway on takeoff. Since most people fly with the keyboard you're either pulling the controls back fully or not at all so it's much harder to take off without striking the runway with the tail.

To be fair though, that's more the fault of those ridiculous B9 engines. What I would do is a combination of both - move the wings (and gears) back and add canards on the front to help lift the nose up and bring the CoL forward to wherever it is now. Or just use the longer B9 gears on the nose instead?

[marach]

or you know add a canard

[BudgetHedgehog]

or you know add a canard

I don't know where the CoM and CoL are in relation to each other, just adding a canard could bring the CoL forward too much, possibly to the point of instability, which is why I suggested moving the wings back to compensate.

[KerbMav]

Try canards, control surfaces near the cockpit, to lift up the nose.

I also think B9 has landing gear with different "leg lengths" so you could place the plane with a higher nose on the runway.

Edit: Bad ninja me got ...

[Hodo]

You don't need Canards or anything near the nose to lift it. Your problem is exactly what ObsessedKSP said in his first post. Your landing gear are to far to the rear of the craft. Try moving your rear landing gear closer to your CoM, this would give you a point of rotation for the aircraft to rotate around so it can get the nose off the ground.

[Taki117]

Another issue (And this is more visual) is that your control surfaces are not in line. some of them appear to be at odd angles which may result in unwanted yawing. This is fixed by turning off angle snap when placing control surfaces.

[LethalDose]

You don't need Canards or anything near the nose to lift it. Your problem is exactly what ObsessedKSP said in his first post. Your landing gear are to far to the rear of the craft. Try moving your rear landing gear closer to your CoM, this would give you a point of rotation for the aircraft to rotate around so it can get the nose off the ground.

I agree that the issue with take off is probably due to the location of the gear, but canards would be hugely helpful for that aircraft.

It's my experience that aircraft without canards or elevators have horrid pitch control, since there's no control surface far from the CoM. So even if he does get off the runway when he fixes the gear location, the plane's still probably going to crash because it can't effectively recover from a dive or a stall.

All that being said, you have to do the canards right, meaning keep the CoL/CoM balanced. I don't get why so many players just dismiss canards, they work great when you do it right.

[Hodo]

I agree that the issue with take off is probably due to the location of the gear, but canards would be hugely helpful for that aircraft.

It's my experience that aircraft without canards or elevators have horrid pitch control, since there's no control surface far from the CoM. So even if he does get off the runway when he fixes the gear location, the plane's still probably going to crash because it can't effectively recover from a dive or a stall.

All that being said, you have to do the canards right, meaning keep the CoL/CoM balanced. I don't get why so many players just dismiss canards, they work great when you do it right.

If you place your elevators correctly and have adaquate size ones, you do not need or want canards at the front of the aircraft. At speed they have a tendancy to stall out long before the elevators at the rear of the craft anyway so they are nearly useless in a highspeed stall.

Like my F-21 SSTO combat aircraft design here, it is a delta wing setup without canards and it handles great.

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[O-Doc]

Move your wings back and your rear gears forward. Your basic problem is that your gears are behind your elevons so you won't get any pivot from your rear gears to pitch your nose up. Ideally your elevons should be back in line with your engines(or further back for high maneuverability) using that basic wing configuration you've gone for.

Edited July 7, 2014 by O-Doc

[Master Tao]

If you end up tail striking a lot, you can put long landing gear at the front and just behind the CM, and short landing gear close to the tail. You have to balance range of pitch on the ground with how much the tail gear get compressed.