Tail strike on roll-out after landing

[rrohde]

This seems to happen each time the speed goes below 100 knots, rolling on the runway - the Mirage's nose goes up, until the tail strikes, and then typically veers to the left off the runway. This is with airbrakes extended, and no wheel brakes applied.

 

Is me, or is this supposed to happen?

 

I remember that when the Mirage first was released, the nose would stay at ~14 deg AoA until it would come down by itself as the speed dropped, same aircraft configuration.

[nomdeplume]

Not sure, but I have read that they don't let the nose drop on its own (not just on the Mirage), as it can come down too hard. Better to gradually lower the nose yourself while you still have control to do it gently.

 

Intuitively it might make sense for the FBW to raise the nose to try to maintain AoA as the speed slows. But perhaps there should be a weight-on-(main)-wheels modifier to that behaviour to prevent it commanding a tail strike?

[jojo]

You have to lower the nose before 100kt, and 110 is better, this is the way it is.

 

By the way aero-braking us to reduce brakes wearing. It's more efficient in term of stopping distance to put nose down and brake right away.

[rrohde]

You have to lower the nose before 100kt, and 110 is better, this is the way it is.

 

By the way aero-braking us to reduce brakes wearing. It's more efficient in term of stopping distance to put nose down and brake right away.

 

Thanks for the feedback!

 

When you say "this is the way it is", is that based on the real M2000C, or based on the recent changes in RAZBAM's patches?

 

I based my initial observation on the very first time I landed the Mirage when it was first released, and it made sense (to me) that the nose drops by itself once there is no more lift after the speed drops sufficiently, and the FBW systems no longer keeps the nose up. Right now, it feels opposite to what makes sense - but as long as this is the real plane's behavior, I will do as you suggest and either push the nose down or engage the wheel brakes to bring it down.

[jojo]

I didn't say to break to put the nose down.

 

What I said is:

- land

- put the nose wheel down with stick

- (use drogue chute if needed)

- then brake

 

You can put nose wheel down at 150kt it's not a problem.

Edited April 9, 2016 by jojo

[Sarge55]

Curious about this as well. It took a lot of forward stick to get the nose down, more than I would have thought. I was quite surprised to be dragging my tail the other day... :joystick:

 

If it's accurate then I'll adjust my landing procedure.

[rrohde]

So yeah, hence my initial comparing the landing behavior of the M2000C when it first came out to now:

 

When it first came out: runway roll-out would eventually lead to the nose setting down by itself after sufficient speed has bled off.

 

Now: runway roll-out eventually leads to the nose going up, even after sufficient speed has bled off.

 

The question is - between the two, which one is the realistic behavior of the real M2000C?

 

Thanks.

 

PS: I'm with Sarge55: "If it's accurate then I'll adjust my landing procedure". Same here; but it would be nice to know if it is (or WIP, bug, etc).

[IvanK]

"When it first came out: runway roll-out would eventually lead to the nose setting down by itself after sufficient speed has bled off."

 

..... is undoubtedly the correct response. The nose remaining high at Low IAS is an impossibility unless there is some truly horrendous aft C of G thing going on.

[rrohde]

Thanks for the feedback, Ivank!

 

So this is an issue then... CptSmiley, what's your take on this? ;)

[Sarge55]

I concur, the nose use to drop of it's own accord which seemed to be a reasonable action as the speed dropped. Very similar to other aircraft. It seemed odd that I now have to force the nose down.

 

However, I have no experience with flying anything let alone a Mirage so will follow direction from those who know.

[mvsgas]

I know nothing about the Mirage 2000, but some aircraft are tail heavy. It could be the mirage is tail heavy or CG is behind main wheels and is one of the reasons it needs FBW and could help with pitch response, maybe quicker in vertical changes...maybe :dunno:

[Sarge55]

Have to say though she lands like a dream now otherwise. No more skidding off into the weeds or weird braking action.

 

Mirage is a pleasure to fly.

[BitMaster]

Tail strike on roll-out after landing

 

I know nothing about the Mirage 2000, but some aircraft are tail heavy. It could be the mirage is tail heavy or CG is behind main wheels and is one of the reasons it needs FBW and could help with pitch response, maybe quicker in vertical changes...maybe :dunno:

 

 

If the cg was that far back behind center gear u couldnt taxi at low speed at all without a techie hanging loose on your cone to keep the nose down ;) Not likely to be like that.

 

 

 

 

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[mvsgas]

You don't think after flying around and burning fuel the CG shift back? O well, it was an idea.

[Art-J]

With or without fuel, every plane has to stand on all its wheels to taxi / be towed around or just stand on the ramp*. Something ain't right here. CG shift calculations in the code?

 

*OK, F7F Tigercat was an infamous exception :).

[spiddx]

Well before nose wheel is down it's not only the CG but also the AoA and corresponding air resistance which pushes the plane back and up... Could be a factor with the big delta wings.

[rrohde]

It now feels much better where it will naturally drop on its own at the right speed. However if you manage to keep pulling up as long as possible and keep the nose up and end up sitting on your tail.

 

So, for me the big question is - if we don't keep pulling, but leave it to the FBW system to hold the prescribed 14 deg AOA, you are saying that with the upcoming tweak the "nose will drop on its own at the right speed" as it should? NICE! :thumbup:

[rrohde]

Awesome. Thanks, CptSmiley!

[Rlaxoxo]

From all indications the gear the reference CG for this guy is in the right location unless I get new information so I guess it is possible you can get this guy to sit on his tail if you try.

 

Already done : D

 

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[IvanK]

Just flown the latest update (1.5.3.52018) I see little change in the Mir2K desire to hold its nose up in the air to very low IAS in the landing roll out. If you overcook it even full forward stick wont get the nose down ... brakes are about the only way to do it. This is most unnatural and unrealistic imo.

 

I have 1500hrs or so on the Mir 3 and broadly speaking the landing roll out (with Auto command engaged ) would imo be very similar to the Mir 2K with full authority FBW. To me I would think that around 100Kts or so the Flight controls simply wouldn't have enough authority to hold the nose up.

[mvsgas]

To me I would think that around 100Kts or so the Flight controls simply wouldn't have enough authority to hold the nose up.

Not the flight controls holding it up

 

Hey guys made some changes this weekend to slightly adjust the feel of landing, mostly it was overhauling the way the weight on wheels sensor works to use the actual physical parameters of the gear (strut compression and force on the struct). Before it was using a built in function call to get weight on wheels which I'm unsure how it does its thing and was proving inconsistent.

 

It now feels much better where it will naturally drop on its own at the right speed. However if you manage to keep pulling up as long as possible and keep the nose up and end up sitting on your tail:

 

There are aircraft out there that, if you manage to let it sit back on its tail it will stay there, it's the way the geometry between the gear and the CG works, here is a diagram to explain:

 

 

Imagine if you tilted this aircraft fully back, if the CG was close enough to the gear in such a way then when you tilted it fully back so that the back is on the ground, if the normal line (that is the vertical from the CG to the ground) could end up being behind the landing gear he'll be able to sit on his tail. I hope that makes sense, I couldn't find a diagram showing the change when pitched up.

 

From all indications the gear the reference CG for this guy is in the right location unless I get new information so I guess it is possible you can get this guy to sit on his tail if you try.

 

http://forums.eagle.ru/showpost.php?p=2739942&postcount=17

[IvanK]

My point is MSVGAS even with full backstick you shouldnt be able to hold the nose up..... it happens even with stick neutral in the mir2k. I understand the C of G related issues.

If the real Mir2k behaved like this there would scraped tails left right and centre..... and the sumpies would soon get tired of replacing nozzle flaps :)

Edited April 11, 2016 by IvanK

[BitMaster]

You don't think after flying around and burning fuel the CG shift back? O well, it was an idea.

 

 

Sure, the cg shown is dry weight, whatever is added is added before or on top of cg. You dont burn fuel to becone tailheavy unless pump failure or such.

 

Nose heavy flies well as long as the fuselage and stabs have enough strength ( long. chord ) and authority to rotate around horiz. axis.

 

Have you ever flown tail ?

Watch the stick and UP she goes

 

 

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[Davee]

My point is MSVGAS even with full backstick you shouldnt be able to hold the nose up..... it happens even with stick neutral in the mir2k. I understand the C of G related issues.

If the real Mir2k behaved like this there would scraped tails left right and centre..... and the sumpies would soon get tired of replacing nozzle flaps :)

 

+1

and . . . . . IvanK knows his stuff guys.

[rrohde]

Hey guys, got some info from others as well as the very useful input here, going to be looking into it and will probably be making some small adjustments to get the right response per the input, will provide a summary when all is done. Thanks!

 

This statement here is still correct, though?

 

http://forums.eagle.ru/showpost.php?p=2740178&postcount=19