Use the computer or aiming device.

3rd person view should be remove in general, too much arcade!

First of all, mortar is not a cannon.
For firing with mortar you have to setup correct angle to reach your target.
You can also firing on targets and don't see on them.
http://www.globalsecurity.org/military/library/policy/army/fm/7-90/fig7-4.gif
For this, there's the computer.
So this is not a bug.

3rd person view is for achieving lower difficulty.

@redstone at the moment 3rd person view is like 1st person looking up. All you see is the sky, how could anyone even use it for anything? I'm aware how you aim mortar even made a quick tutorial http://killzonekid.com/arma-3-how-to-aim-mk6-mortar-in-first-person/

3rd person should be for keeping an eye on your surrounding. At the moment, it is useless for everything except looking at the clouds

3rd person view is aligned with the tube, becose crosshair is for aiming from "external" view, so you have to aim "manualy" in this >45° direction to hit the targets.
There's nothing to change.

Just note from my arma gaming experience... For keeping an eye on your surrounding is better to use optics or binoculars then 3rd person view at all ;)

@redstone I have uploaded a video of aiming in 3rd person.

http://www.youtube.com/watch?v=w7hhPY-dRqs

I would like you to explain to me what am I doing wrong, because the way I see it you can't possibly use this view for anything. You have no idea what is your elevation or direction. You need to have compass to know direction because you cannot see anything but clouds. Also sorry but you can't even call it 3rd person view as it looks like 1st person view.

I would also like to hear from those 3 who downvoted it. How do you use it? What is the secret?

3dr person view should stay forever. That's one of the main reasons people love arma. This doesn't means that in some cases is useless, like this one.
Like redstone says the crosshair is aligned with the tube and is nothing we can do. Is not a bug is the way the game is.
Don't use 3rd person view in this cases mate.

Wow Peter just wow! Arma 2 is full of bugs, but this is Arma we all love so there is nothing we can do. Arma 3 is also Arma so there is equally nothing we can do. Right.

Yeah, Peter, that is a very bad explanation on your part. I'm completely on Killzone's side. What is the secret to using it? IRL you can look at your target and then adjust your mortar according to what you see. The men who use mortars aren't locked to hugging it and staring at the sky. Please explain.

If I not wrong I see that issue in arma 2 with some static weapons like that. I think the mortar but Im not sure. I was referring that this issue is related to the engine or the way the config is stablished. If they can solve/change this Ill be also happy but I dont think they will do that due to there are lot of things to improve.
Anyways thats the reason of this forum :-)

There should be a way to keep the unit 3rd pers view instead of the "vehicle" 3rd pers view.

I think this can be considered related to #10117 (SDV gunner w/ periscope-down issue in 3rd pers.).
In these cases, as 50.cal says, the external view should be tied to the character and not the vehicle.

@redstone here is what I'm talking about:

http://www.youtube.com/watch?v=_FtojHPdmEI

@redstone Thank you for fixing it!

Could you post a screenshot of the new view? Or is it like in the video?

almost like in the video, but the camera is centered

fixed