JAGflyer
Topic Author
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Joined: Tue Aug 10, 2004 5:31 am

### How Many T/R On The A380

From all the pics I have seen they only have or use the inboard thrust reversers (engine 2 and 3). Does the A380 only have them on those engines or did they just use the inboards in all those photos?
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ZBBbird
Posts: 58
Joined: Sat Jul 17, 2004 10:04 am

### RE: How Many T/R On The A380

As far as I know they only have thrust reverse on the inboard engines. The reason being that with the A380's large wingspan their would be more danger of the outboard engines ingesting FOD as they would be at the edge or over the edge of the runway.

sabenapilot
Posts: 2442
Joined: Sat Feb 26, 2000 6:18 pm

### RE: How Many T/R On The A380

Reversers are not taken into account is the calculation of the stopping distance of a plane. On modern planes, the pilots simply select a deceleration rate of the plane upon landing and an automatic system does the rest. Should they decide to use some T/R, all that would do is to put less braking force on the brakes, but the plane would not stop on a shorter distance.

FDXmech
Posts: 3219
Joined: Sun Mar 19, 2000 9:48 pm

### RE: How Many T/R On The A380

 Quoting Sabenapilot (Reply 2):Reversers are not taken into account is the calculation of the stopping distance of a plane.

Not because thrust reversers provide a negligable slowing force rather these calculations are based on only basic equipment -brakes. And not based on new brakes able to absorb lots of kinetic energy but worn down to the limits.

 Quoting Sabenapilot (Reply 2):On modern planes, the pilots simply select a deceleration rate of the plane upon landing and an automatic system does the rest. Should they decide to use some T/R, all that would do is to put less braking force on the brakes, but the plane would not stop on a shorter distance.

The T/R's when using auto-brakes are an added component used to reach a desired deceleration rate. Not a good criteria to say T/R's don't affect stopping dx.

Though thrust reversers aren't used in determining stopping distance, the plane can't be dispatched with more than one inop.

If the A380 only has two T/R's, it was to address a weight problem.

And that's fine with me. Two less T/R's to break.

[Edited 2005-04-28 18:55:04]
You're only as good as your last departure.

Starlionblue
Posts: 17208
Joined: Fri Feb 27, 2004 9:54 pm

### RE: How Many T/R On The A380

 Quoting FDXMECH (Reply 3):If the A380 only has two T/R's, it was to address a weight problem.

Really, for the FOD problem as well.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

MrChips
Posts: 933
Joined: Wed Mar 30, 2005 2:56 pm

### RE: How Many T/R On The A380

Not only that, but consider the noise issue. Many of the airports the A380 will operate out of, such as LHR, have severe noise restrictions and quotas, meaning that many operators choose to forego the use of reverse thrust anyways.
Time...to un-pimp...ze auto!

MERSPACE
Posts: 56
Joined: Fri Mar 12, 2004 11:23 am

### RE: How Many T/R On The A380

Can the A380 make use of a single T/R, or is there an asymetry issue with
only one T/R --Engine thrust so far from centerline ?

MERSPACE

FDXmech
Posts: 3219
Joined: Sun Mar 19, 2000 9:48 pm

### RE: How Many T/R On The A380

 Quoting MrChips (Reply 5):Not only that, but consider the noise issue. Many of the airports the A380 will operate out of, such as LHR, have severe noise restrictions and quotas, meaning that many operators choose to forego the use of reverse thrust anyways.

I sincerely doubt it. If noise is that large an issue at certain airports, then simply don't use reverse thrust.

I believe leaving off two T/R's is simply a weight savings issue. Anything else is a public relations ploy. Spin if you will.

I don't see or hear many foreign operators negate the use of reverse thrust here at EWR.
You're only as good as your last departure.

MrChips
Posts: 933
Joined: Wed Mar 30, 2005 2:56 pm

### RE: How Many T/R On The A380

How is what I said "spin"?

I was simply stating that many airports that the A380 may operate out of have severe noise restrictions...much more strict than any airport here in North America.

Therefore, if its not going to be used, or is restricted in use, why include it in the airplane?

I think what happened here is a "cause-effect" situation...I had a potential cause, and FDXMECH another congruent cause as well:

Cause - noise restrictions, ever-pressing need to save weight,
Effect - delete T/R from engines #1 and #4.

I can imagine that deleting the reversers goes a ways to reduce complexity as well.
Time...to un-pimp...ze auto!

HAWK21M
Posts: 29917
Joined: Fri Jan 05, 2001 10:05 pm

### RE: How Many T/R On The A380

 Quoting FDXMECH (Reply 7):I believe leaving off two T/R's is simply a weight savings issue.

I think its mainly an FOD prevention Issue,due to Wing span of the A380.
regds
MEL
I may not win often, but I damn well never lose!!!

FDXmech
Posts: 3219
Joined: Sun Mar 19, 2000 9:48 pm

### RE: How Many T/R On The A380

MrChips;

In no way do I consider your suggestion, "spin". I apologize if you thought as much.

But if Airbus uses that reasoning, than I do consider it spin.
You're only as good as your last departure.

HAWK21M
Posts: 29917
Joined: Fri Jan 05, 2001 10:05 pm

### RE: How Many T/R On The A380

Any Pics with the T/Rs deployed.
regds
MEL
I may not win often, but I damn well never lose!!!

Jamie757
Posts: 838
Joined: Wed Apr 27, 2005 8:33 pm

### RE: How Many T/R On The A380

 Quoting Sabenapilot (Reply 2):Should they decide to use some T/R, all that would do is to put less braking force on the brakes, but the plane would not stop on a shorter distance

Surely thrust reversers would reduce the distance taken for a plane to stop?

Rgds
"I feel like a turkey who's just caught Bernard Matthews grinning at him!"

air2gxs
Posts: 1443
Joined: Mon Jun 18, 2001 1:29 pm

### RE: How Many T/R On The A380

 Quoting Jamie757 (Reply 12):Surely thrust reversers would reduce the distance taken for a plane to stop?

If the auto-brake system is not used, the reversers will aid in slowing the aircraft and decrease stopping distance. If auto-brakes are used, the stopping distance will not change. The deceleration rate is set by the flight crew and maintained by the computer. Any added effect from the thrust reversers would be added to the equation and the braking action from the brakes would be reduced. Thus, stopping distance is un-affected by the reversers.

Jamie757
Posts: 838
Joined: Wed Apr 27, 2005 8:33 pm

### RE: How Many T/R On The A380

 Quoting Air2gxs (Reply 13):If the auto-brake system is not used, the reversers will aid in slowing the aircraft and decrease stopping distance. If auto-brakes are used, the stopping distance will not change. The deceleration rate is set by the flight crew and maintained by the computer. Any added effect from the thrust reversers would be added to the equation and the braking action from the brakes would be reduced. Thus, stopping distance is un-affected by the reversers.

I understand now, thanks for the simpletons guide!! Lol

Rgds
"I feel like a turkey who's just caught Bernard Matthews grinning at him!"

Jetlagged
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### RE: How Many T/R On The A380

There is an exception to this, where the autobrake has a MAX position. In that case the brakes will be applied fully, with no demanded deceleration rate. Thrust reverse in this case will reduce stopping distance.
The glass isn't half empty, or half full, it's twice as big as it needs to be.

FDXmech
Posts: 3219
Joined: Sun Mar 19, 2000 9:48 pm

### RE: How Many T/R On The A380

This according to Airbus.com.
_________________________________________________________________
Environmental Friendliness

The A380 will help cope with growing passenger numbers without negatively impacting the environment, thanks to significantly reduced noise and emission levels. In spite of its higher weight and thrust requirements, the A380 will make less noise than its closest competitor, while carrying 30 to 50 per cent more people. Current noise certification rules (ICAO "chapter 3") will be met by significant margins and the A380 will be compliant with the strictest local noise regulations, classified QC2 for departure from London's busy airports and QC1 for arrival.

For ground operations, the A380 can taxi with only two engines if required, will use only two thrust reversers and will employ a low-noise auxiliary power unit to help eliminate any noise concern.

_________________________________________________________________

Putting a pleasant face on weight reduction.
You're only as good as your last departure.

fergulmcc
Posts: 1877
Joined: Thu Oct 14, 2004 8:36 pm

### RE: How Many T/R On The A380

 Quoting HAWK21M (Reply 11):Any Pics with the T/Rs deployed.

Here is one,

View Large View Medium

Take care

Fergul
Zambian Airways, Where the Eagles fly free!!

HAWK21M
Posts: 29917
Joined: Fri Jan 05, 2001 10:05 pm

### RE: How Many T/R On The A380

 Quoting Fergulmcc (Reply 17):Quoting HAWK21M (Reply 11): Any Pics with the T/Rs deployed. Here is one,

Wow.Old thread.Any Offical data on the T/Rs
Thanks.
regds
MEL
I may not win often, but I damn well never lose!!!

Starlionblue
Posts: 17208
Joined: Fri Feb 27, 2004 9:54 pm

### RE: How Many T/R On The A380

 Quoting Jamie757 (Reply 12):Surely thrust reversers would reduce the distance taken for a plane to stop?

If autobrakes are used maximally yes, but reversers can still not be used for the calculated stopping distance. That is, they are a bonus, but your calculations have to assume they don't exist.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

474218
Posts: 4510
Joined: Mon Oct 10, 2005 12:27 pm

### RE: How Many T/R On The A380

 Quoting Jetlagged (Reply 15):There is an exception to this, where the autobrake has a MAX position. In that case the brakes will be applied fully, with no demanded deceleration rate. Thrust reverse in this case will reduce stopping distance.

What about anti-skid system it has to be taken into consideration?

 Quoting ZBBbird (Reply 1):As far as I know they only have thrust reverse on the inboard engines.

So you must have at least two different spare engines, 1 inboard and 1 outboard, another added expense to an all ready expensive aircraft.

Starlionblue
Posts: 17208
Joined: Fri Feb 27, 2004 9:54 pm

### RE: How Many T/R On The A380

 Quoting 474218 (Reply 20):Quoting ZBBbird (Reply 1): As far as I know they only have thrust reverse on the inboard engines. So you must have at least two different spare engines, 1 inboard and 1 outboard, another added expense to an all ready expensive aircraft.

Not really. Most of the components of the engine are identical. It's only some parts of the bypass duct that change.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

OldAeroGuy
Posts: 3224
Joined: Sun Dec 05, 2004 6:50 am

### RE: How Many T/R On The A380

 Quoting Starlionblue (Reply 19):If autobrakes are used maximally yes, but reversers can still not be used for the calculated stopping distance. That is, they are a bonus, but your calculations have to assume they don't exist.

On icy runways, most pilots are happy to have all the reverse thrust they can get.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis

Starlionblue
Posts: 17208
Joined: Fri Feb 27, 2004 9:54 pm

### RE: How Many T/R On The A380

 Quoting OldAeroGuy (Reply 22):Quoting Starlionblue (Reply 19): If autobrakes are used maximally yes, but reversers can still not be used for the calculated stopping distance. That is, they are a bonus, but your calculations have to assume they don't exist. On icy runways, most pilots are happy to have all the reverse thrust they can get.

I get that, but you can't really "count" on them in your calculations. This doesn't mean they won't be used of course
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

Pihero
Posts: 4232
Joined: Mon Jan 31, 2005 5:11 am

### RE: How Many T/R On The A380

We seem to forget the A-380 dimensions, here.
To put things into perspective, the centreline of the outer engines are some 52 meters apart. That means that with the engines' diameter slightly less than four meters, each outer engine hangs only two meters inside the width of a 60 m runway. As the 744 manual states that at take-off power, the suction volume extends more than 35 feet around the engine, the likelyhood of ingestion appears quite real (I safely assume that the 380 ingestion volume will be a lot greater on 380 engines.)

On the weight question :
FedexMech, I think we need to qualify your observation :With the outer engines hanging that far out on the wing, I would also think that the wing bending relief they bring could mean a lot of weight saving on 1/ the wing structure and 2/- on the wing-to-fuselage attachment. How much compared to a T/R installation, I don't know but with such dimensions, I would bet on a lot.
A totally unconfirmed rumour last year was about AI needing to harden the airplane's structure as the whole airframe was close to a 1hz resonnance frequency, which was prejudicial to the occupants comfort, hence the fattening up of the aircraft. I happen to believe that rumour.

On the necessity of T/Rs :
The debate is wide open. What I can say is that I've seen airplanes dispatched with inoperative reversers -yes, a twin-engined aircraft can be dispatched without T/Rs except on contaminated runway take-offs - and that in Europe, local noise limitations prevent their use outside an emergency.

Let's not also forget that the 380 braking efficiency is greater than a 744's, because 1/-the landing and take-off speeds are much lower and 2/-the braking energy is distributed on a greater number of brakes (20 iso 16).

Just my two cents.
Contrail designer

Boeing Nut
Posts: 5078
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### RE: How Many T/R On The A380

There was another post on this sometime back and I was certain that the A380 had four reversers. In fact, I was very bullheaded about it. Until that is, I was "handed my ego" when a few member posted not only pics but links that stated that only two exist.

I had a nice merlot with my crow that night.

Turns out, that A.net actually can be educational.

I'm not a real aeronautical engineer, I just play one on Airliners.net.

Tristarsteve
Posts: 3373
Joined: Tue Nov 22, 2005 11:04 pm

### RE: How Many T/R On The A380

 Quoting 474218 (Reply 20):So you must have at least two different spare engines, 1 inboard and 1 outboard, another added expense to an all ready expensive aircraft.

No, The thrust reversers are in the C (orD) ducts which are part of the airframe. When you change an engine you open the C ducts and lower the engine out between them. They stay behind. This applies to most Wide body jets, except the RB211-524 on the B767 and B747 (and TriStar) where the reverser is part of the engine.

Starlionblue
Posts: 17208
Joined: Fri Feb 27, 2004 9:54 pm

### RE: How Many T/R On The A380

Just to clarify, the risk of ingestion on the outboards is of course there during takeoff as well, but any ingested turf or other junk would just be blown out the arse of the engine, not potentially bounce against the fuse or wing if it rocketed out of the reverser..
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

Jetlagged
Posts: 2562
Joined: Sun Jan 23, 2005 3:00 pm

### RE: How Many T/R On The A380

 Quoting Pihero (Reply 24):To put things into perspective, the centreline of the outer engines are some 52 meters apart. That means that with the engines' diameter slightly less than four meters, each outer engine hangs only two meters inside the width of a 60 m runway. As the 744 manual states that at take-off power, the suction volume extends more than 35 feet around the engine, the likelyhood of ingestion appears quite real (I safely assume that the 380 ingestion volume will be a lot greater on 380 engines.)

I think that off runway FOD is much more of a problem to the A380 in the takeoff case than in the reverse thrust case, for the reason you give (the suction volume in front of the intake). Airflow and suction is higher at takeoff than in reverse and takeoff thrust is applied at very low speed, whereas reverse thrust would be cancelled by 80 knots or so. Having the engine over the runway edge means some more debris will be thrown up but that doesn't necessarily mean more will be ingested as long as airspeed is high enough. Overall, the weight reduction theory seems a bit more plausible to me.

I would guess most pilots would prefer to have a reverser on each engine. What about a max weight RTO, where one of the inboard engines has failed, especially on a wet runway? With a twin you would have to deal with asymmetric reverse thrust, but on the A380 in addition to thrust asymmetry the outboard engines are still producing significant forward thrust, reducing deceleration.

Were there are any early Airbus concepts showing the A380 (or A3XX) with outboard reversers? That might shed some interesting light on the question.
The glass isn't half empty, or half full, it's twice as big as it needs to be.

OldAeroGuy
Posts: 3224
Joined: Sun Dec 05, 2004 6:50 am

### RE: How Many T/R On The A380

 Quoting Starlionblue (Reply 23):I get that, but you can't really "count" on them in your calculations.

No longer true and it never was true for UKCAA regulations.

With the advent of FAR25 Amendt. 98, the FAA and EASA (formerly JAA) now allow the use of reverse thrust for calculating certified takeoff performance on a wet runway.

From a practical standpoint, this helps twins more than quads for takeoff since quads are more frequently limited by factored all engine takeoff distance.

You're right for certified landing performance, but from a practical standpoint, alot of airline operations departments do calculate landing performance on wet, slushy and icy runways taking reverse thrust into account.

The low level of reverse thrust on the A380 may create some interesting real world landing issues on contaminated runways.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis

474218
Posts: 4510
Joined: Mon Oct 10, 2005 12:27 pm

### RE: How Many T/R On The A380

 Quoting TristarSteve (Reply 26):No, The thrust reversers are in the C (orD) ducts which are part of the airframe. When you change an engine you open the C ducts and lower the engine out between them. They stay behind. This applies to most Wide body jets, except the RB211-524 on the B767 and B747 (and TriStar) where the reverser is part of the engine.

Thanks TristarSteve,

I remember that now, all my engine experience (which is very limited) was on J-58's and RB-211's.

Pihero
Posts: 4232
Joined: Mon Jan 31, 2005 5:11 am

### RE: How Many T/R On The A380

 Quoting Jetlagged (Reply 28): What about a max weight RTO, where one of the inboard engines has failed, especially on a wet runway? With a twin you would have to deal with asymmetric reverse thrust, but on the A380 in addition to thrust asymmetry the outboard engines are still producing significant forward thrust, reducing deceleration.

That is an interesting discussion !
Contrail designer

474218
Posts: 4510
Joined: Mon Oct 10, 2005 12:27 pm

### RE: How Many T/R On The A380

 Quoting Pihero (Reply 31):Quoting Jetlagged (Reply 28): What about a max weight RTO, where one of the inboard engines has failed, especially on a wet runway? With a twin you would have to deal with asymmetric reverse thrust, but on the A380 in addition to thrust asymmetry the outboard engines are still producing significant forward thrust, reducing deceleration.

No problem, Airbus has said they have triple computer backup on all systems?

Pihero
Posts: 4232
Joined: Mon Jan 31, 2005 5:11 am

### RE: How Many T/R On The A380

So has Boeing.
Then what is your point ?
Contrail designer

474218
Posts: 4510
Joined: Mon Oct 10, 2005 12:27 pm

### RE: How Many T/R On The A380

Is it not Airbus philosophy that there is no problem that three computers can not get you out of, or better yet, not let you get into.

Jetlagged
Posts: 2562
Joined: Sun Jan 23, 2005 3:00 pm

### RE: How Many T/R On The A380

 Quoting 474218 (Reply 32):No problem, Airbus has said they have triple computer backup on all systems?

 Quoting 474218 (Reply 34):Is it not Airbus philosophy that there is no problem that three computers can not get you out of, or better yet, not let you get into.

Any number of computers won't stop an engine failing.
The glass isn't half empty, or half full, it's twice as big as it needs to be.

777236ER
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Joined: Sat Aug 18, 2001 7:10 am

### RE: How Many T/R On The A380

 Quoting Jetlagged (Reply 15):There is an exception to this, where the autobrake has a MAX position. In that case the brakes will be applied fully, with no demanded deceleration rate. Thrust reverse in this case will reduce stopping distance.

Small point, but generally the MAX autobrake setting still commands a deceleration rate. The maximum braking strength can be achieved using full manual braking, or the RTO setting.

Almost certainly the lack of thrust reversers was because of weight concerns. The FOD issue is real. Someone said the greater suction at t/o power will be more of a FOD hazard than reverse thrust, but that's not really the case. While reversing the bypass air, there's significant disturbance to FOD on the ground, someone of which can be blown forward into the fan. With the engine running at ~60% N1 (say) and with 87% of inlet air reversed, there's a greater FOD potential during reverse.

That being said, it would have been easy to limit the use of outboard engines to wide runways and emergencies.
Your bone's got a little machine

Jetlagged
Posts: 2562
Joined: Sun Jan 23, 2005 3:00 pm

### RE: How Many T/R On The A380

 Quoting 777236ER (Reply 36):Someone said the greater suction at t/o power will be more of a FOD hazard than reverse thrust, but that's not really the case. While reversing the bypass air, there's significant disturbance to FOD on the ground, someone of which can be blown forward into the fan. With the engine running at ~60% N1 (say) and with 87% of inlet air reversed, there's a greater FOD potential during reverse.

The someone was me. The point I was making was that while reverse thrust can certainly kick up FOD, potentially for ingestion, takeoff thrust will also suck it up from the grass, purely due to the suction of the intake air. So if reversers over the runway edge are a problem, so is full thrust at low forward speed. Perhaps I shouldn't have claimed it was more of a problem, but problem it is.

In my view the chances of FOD damage in reverse is no greater on the A380 than any other type, so long as you keep out of the FOD re-ingestion envelope.
The glass isn't half empty, or half full, it's twice as big as it needs to be.

Starlionblue
Posts: 17208
Joined: Fri Feb 27, 2004 9:54 pm

### RE: How Many T/R On The A380

 Quoting Jetlagged (Reply 37):The someone was me. The point I was making was that while reverse thrust can certainly kick up FOD, potentially for ingestion, takeoff thrust will also suck it up from the grass, purely due to the suction of the intake air. So if reversers over the runway edge are a problem, so is full thrust at low forward speed. Perhaps I shouldn't have claimed it was more of a problem, but problem it is.

As I said, if you have FOD during forward thrust, it'll probably just go out the back unless it's something large (planespotter holding camera).

But if you're in reverse, the FOD may end up rocketing out of the reverser and embed itself in something important, like the wing of the fuse or the other engine. Oops.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

HAWK21M
Posts: 29917
Joined: Fri Jan 05, 2001 10:05 pm

### RE: How Many T/R On The A380

 Quoting Jetlagged (Reply 37):So if reversers over the runway edge are a problem, so is full thrust at low forward speed. Perhaps I shouldn't have claimed it was more of a problem, but problem it is.

Considering the Angle created by the Deflected Reverse thrust to that by the Suction at the Inlet.I don't think they can be compared.The Reverse Thrust covers a wider angle & hence more prone to FOD.
regds
MEL
I may not win often, but I damn well never lose!!!

Jetlagged
Posts: 2562
Joined: Sun Jan 23, 2005 3:00 pm

### RE: How Many T/R On The A380

 Quoting Starlionblue (Reply 38):But if you're in reverse, the FOD may end up rocketing out of the reverser and embed itself in something important, like the wing of the fuse or the other engine. Oops.

Good point, but unless it's something large it won't do much damage, in which case the engine will suffer too.
The glass isn't half empty, or half full, it's twice as big as it needs to be.

Jetlagged
Posts: 2562
Joined: Sun Jan 23, 2005 3:00 pm

### RE: How Many T/R On The A380

 Quoting 777236ER (Reply 36):generally the MAX autobrake setting still commands a deceleration rate

Not on any Airbus, nor on the 747, at least.
The glass isn't half empty, or half full, it's twice as big as it needs to be.

HAWK21M
Posts: 29917
Joined: Fri Jan 05, 2001 10:05 pm

### RE: How Many T/R On The A380

 Quoting Jetlagged (Reply 41):Not on any Airbus, nor on the 747, at least.

Whats the Exception like.
regds
MEL
I may not win often, but I damn well never lose!!!

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