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ColAvionLover
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B777 "Tailwheel"?

Wed Nov 16, 2011 3:40 am

Hi All

I just saw this photo on the Top 5 and wanted to know, what's that tin thing in the lower back part of the fuselage, like a tail wheel. I know it is not a tail wheel but something related to tailstrike.

What is it?


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Photo © David Brook-CYYZ Aviation Photography



Regards,

Jarib.
 
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Starlionblue
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RE: B777 "Tailwheel"?

Wed Nov 16, 2011 4:09 am

It's a tail skid. It protects the tail in case it should touch the ground during take-off or landing. Better for the skid to sacrifice itself than for the tail to hit. It's just a little peg with a hydraulic (I guess) actuator.

Many longer airliners have them, for example 340-600 and 737-900. Concorde had a little twin wheel unit.

 
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ColAvionLover
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RE: B777 "Tailwheel"?

Wed Nov 16, 2011 5:21 am

Quoting Starlionblue (Reply 1):
Many longer airliners have them, for example 340-600 and 737-900. Concorde had a little twin wheel unit.

Well, this is the first time I see that -tail skid- in a plane instead of a Concorde. Is it common for it to be dropped? I mean, do is it always dropped? Or is it automatically dropped according to plane's weight and any other variables (IE: Rwy Length, temperature, etc)?

Thanks.
 
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Starlionblue
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RE: B777 "Tailwheel"?

Wed Nov 16, 2011 8:30 am

Quoting ColAvionLover (Reply 2):
Is it common for it to be dropped? I mean, do is it always dropped? Or is it automatically dropped according to plane's weight and any other variables (IE: Rwy Length, temperature, etc)?

AFAIK it comes down with the gear but I'm not really sure.
 
murchmo
Posts: 112
Joined: Sun Sep 11, 2005 2:59 pm

RE: B777 "Tailwheel"?

Wed Nov 16, 2011 9:54 am

The recent LoT gear up landing utilized it well.

http://www.tvn24.pl/0,1722771,0,1,kl...boeinga-nad-okeciem,wiadomosc.html
 
wilco737
Posts: 7275
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RE: B777 "Tailwheel"?

Wed Nov 16, 2011 9:55 am

Quoting Starlionblue (Reply 3):
AFAIK it comes down with the gear but I'm not really sure.

Yes it does. During other phases of flight you don't need it.

wilco737
  
 
330guy
Posts: 239
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RE: B777 "Tailwheel"?

Wed Nov 16, 2011 1:02 pm

The 727 also has one... (Im in work so cannot post a picture) But its right where youd expect it to be
 
BoeingGuy
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RE: B777 "Tailwheel"?

Wed Nov 16, 2011 5:08 pm

The 777-300s, 767-300, 767-400, 737-800, 737-900 have Tail Skids due to the length of the fuselage. IIRC the 737 ones are always there, but the 767 and 777 ones extend and retract with the landing gear.
 
KingFriday013
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RE: B777 "Tailwheel"?

Wed Nov 16, 2011 9:38 pm

The 757-300 and CRJ-900 have tail skids as well. On all of the 737NG series (not sure about the 600 though... and maybe someone can clarify about classics) they have a skid kinda thing but looks more like a hump, and it's fixed (does not extend/retract).

-J.
 
BoeingGuy
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RE: B777 "Tailwheel"?

Wed Nov 16, 2011 10:32 pm

Quoting KingFriday013 (Reply 8):
On all of the 737NG series

I'm pretty sure the 737-700 doesn't have it either. It's a -800 and -900 thing. Yeah, I should have thought about the 757-300.
 
Tristarsteve
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RE: B777 "Tailwheel"?

Wed Nov 16, 2011 11:25 pm

Quoting KingFriday013 (Reply 8):
and maybe someone can clarify about classics) they have a skid kinda thing but looks more like a hump, and it's fixed (does not extend/retract).

The B737-400 was the first. Not fitted or needed on the -300 or -500.
It is a fixed skid, attached by a crushable cylinder. I have never seen one crushed.

The Tristar had a retractable tail skid. As usual on the Tristar a clever device that extended using hydraulic power and then used the same fluid as an oleo device. It was meant to cushion the impact. But I have only seen one contact, and it nearly ripped the whole strut off the fuselage.
 
Viscount724
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RE: B777 "Tailwheel"?

Wed Nov 16, 2011 11:27 pm

Quoting 330guy (Reply 6):
The 727 also has one... (Im in work so cannot post a picture) But its right where youd expect it to be

727 tailskid visible in these photos.


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Photo © Javier Rodriguez - Iberian Spotters
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Photo © Jaysen F. Snow - Midwest Tail Chasers


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Photo © JetStream Aviation
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Photo © Toni Marimon

 
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kanban
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RE: B777 "Tailwheel"?

Wed Nov 16, 2011 11:27 pm

As I recall some of the 707's were fixed and did not retract.. and at one point the skid surface was oak... that didn't last long (no pun intended)
 
BoeingGuy
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RE: B777 "Tailwheel"?

Thu Nov 17, 2011 1:33 am

https://www.airliners.net/aviation-forums/rules.main?confirm=no

Quoting kanban (Reply 12):
As I recall some of the 707's were fixed and did not retract.


The 707's were not tailskids in case there should be a tail strike. They were "ventral fins" for aerodynamic purposes. To my knowledge, no 707s had tailskids.

[Edited 2011-11-16 17:36:44]

[Edited 2011-11-16 17:37:03]
 
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tb727
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RE: B777 "Tailwheel"?

Thu Nov 17, 2011 4:45 am

Quoting Viscount724 (Reply 11):
727 tailskid visible in these photos.

-100's are electric and the -200's are hydraulic. It's a fairly big fuel hit if it gets stuck out for cruise, 10% increase in burn comes to mind.
 
atct
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RE: B777 "Tailwheel"?

Thu Nov 17, 2011 6:14 am

The 737-400/800/900's all have tail skids as seen below


The SFP (short field peformance) 800 and 900ER's skid extends due to the increase angle at which the aircraft approachs, rotates, and flairs due to its lower approach speed.


Not my pictures

ATCT
 
SlamClick
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RE: B777 "Tailwheel"?

Thu Nov 17, 2011 3:47 pm

The 727 skid had a one-time crush material inside the strut to absorb the energy of the strike. It appeared to be something very like tightly rolled cardboard, lacquered to a very rigid state. I have seen one of these that was compressed less than half an inch in a tailstrike. The remaining energy transferred up to the attach point and did damage to the aircraft structure almost equalling the value of the plane. Some complex sheet metal bits had to be drilled out and replaced, in some cases new ones fabricated because the plane is out of production.
 
yeelep
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RE: B777 "Tailwheel"?

Thu Nov 17, 2011 4:44 pm

Quoting atct (Reply 15):
The SFP (short field peformance) 800 and 900ER's skid extends due to the increase angle at which the aircraft approachs, rotates, and flairs due to its lower approach speed.

None of the -800 SPF equipt planes at my airline have the two position tail skid. It may be a option or a very recent running change.
 
Fabo
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RE: B777 "Tailwheel"?

Thu Nov 17, 2011 9:48 pm

Quoting yeelep (Reply 17):
None of the -800 SPF equipt planes at my airline have the two position tail skid. It may be a option or a very recent running change.

It is, (or at the very least was) an option. Two position skids are more expensive and slightly heavier.
 
vc10
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RE: B777 "Tailwheel"?

Thu Nov 17, 2011 10:18 pm

The 707's were not tailskids in case there should be a tail strike. They were "ventral fins" for aerodynamic purposes. To my knowledge, no 707s had tailskids.

I thought that the ventral fin was introduced on the B707 -400 at the request of the British CAA who thought it was lacking in fin area, and so Boeing built the B707-300 with a larger fin area to overcome the need for this ventral fin

Could be wrong though

littlevc10
 
JAGflyer
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RE: B777 "Tailwheel"?

Fri Nov 18, 2011 2:32 am

As mentioned, the 737NG tailskid contains a crushable cartridge which is meant to absorb the force so it does not (or does minimal) damage to the structural integrity of the aircraft. In the photo above you can see a green/red sticker. When the green part is visible, the tailskid is serviceable. When only red is visible it requires repair/replacement of the crush cartridge. For some reason, the green part is much larger than the red which is the opposite of the ones I have seen in person.

Anyone know how they change the "tail-wheel" on the Concorde? Is it small enough to replace by hand (like a wheelbarrow wheel)?
 
atct
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Joined: Fri Mar 16, 2001 6:42 am

RE: B777 "Tailwheel"?

Fri Nov 18, 2011 7:09 pm

Quoting yeelep (Reply 17):
None of the -800 SPF equipt planes at my airline have the two position tail skid. It may be a option or a very recent running change.

I didnt know we had SFP -800's, learn something new everyday.

ATCT
 
474218
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Joined: Mon Oct 10, 2005 12:27 pm

RE: B777 "Tailwheel"?

Fri Nov 18, 2011 7:22 pm

Quoting Tristarsteve (Reply 10):
The Tristar had a retractable tail skid. As usual on the Tristar a clever device that extended using hydraulic power and then used the same fluid as an oleo device. It was meant to cushion the impact. But I have only seen one contact, and it nearly ripped the whole strut off the fuselage.

Only the long body TriStar's (-1, -100, -200 and -250's) the -500's had no tail skid!

I agree with you about tail skids. Their alleged purpose was to protect the aft body from damage in case of a tail strike. My experience was that the tail skid actually added to the damage of a tail strike.
 
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ColAvionLover
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RE: B777 "Tailwheel"?

Fri Nov 18, 2011 8:11 pm

Thanks for all your responses. Now I'm wondering, if most of Boeing aircraft have the tail skid, what about Airbus. Which models have it, if they have it.
 
yeelep
Posts: 768
Joined: Mon Apr 04, 2011 7:53 pm

RE: B777 "Tailwheel"?

Sun Nov 20, 2011 11:38 am

Quoting JAGflyer (Reply 20):
In the photo above you can see a green/red sticker. When the green part is visible, the tailskid is serviceable. When only red is visible it requires repair/replacement of the crush cartridge. For some reason, the green part is much larger than the red which is the opposite of the ones I have seen in person.


The picture above is of a 737-400. The apu firebottle overtemp/pressure and discharge indicators are the giveaway. Your right, the NG's have much less of a green area.
 
Max777geek
Posts: 159
Joined: Wed Mar 07, 2007 6:20 pm

RE: B777 "Tailwheel"?

Thu Dec 08, 2011 10:31 pm

Quoting Starlionblue (Reply 1):
Better for the skid to sacrifice itself than for the tail to hit.

During an off board walk with a pilot below a 767, he explained me it was tied to the frame and not only externally for better shock forces distribution over the airframe instead than on the external panels. That did make sense.
 
Max Q
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RE: B777 "Tailwheel"?

Fri Dec 09, 2011 8:11 am

Quoting vc10 (Reply 19):


The 707's were not tailskids in case there should be a tail strike. They were "ventral fins" for aerodynamic purposes. To my knowledge, no 707s had tailskids.

I thought that the ventral fin was introduced on the B707 -400 at the request of the British CAA who thought it was lacking in fin area, and so Boeing built the B707-300 with a larger fin area to overcome the need for this ventral fin

Could be wrong though

You are completely correct, the CAA were not happy with the Dutch Roll characteristics of the B707 and insisted on a fix for certification, initially this was achieved with a Ventral fin for versions sold in the UK.


Later, this problem was addressed with a taller fin and the ventral mod was not necessary.
 
Viscount724
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RE: B777 "Tailwheel"?

Fri Dec 09, 2011 10:48 pm

Quoting Max Q (Reply 26):
Quoting vc10 (Reply 19):


The 707's were not tailskids in case there should be a tail strike. They were "ventral fins" for aerodynamic purposes. To my knowledge, no 707s had tailskids.

I thought that the ventral fin was introduced on the B707 -400 at the request of the British CAA who thought it was lacking in fin area, and so Boeing built the B707-300 with a larger fin area to overcome the need for this ventral fin

Could be wrong though

You are completely correct, the CAA were not happy with the Dutch Roll characteristics of the B707 and insisted on a fix for certification, initially this was achieved with a Ventral fin for versions sold in the UK.


Later, this problem was addressed with a taller fin and the ventral mod was not necessary.

The 707 modifications required by the UK involved both the ventral fin plus the approximate 3 foot taller fin. The taller fin wasn't a separate later modification. The ventral fin was eliminated on later production 707-320B/Cs but the taller fin was standard on all 707s and 720s. Those already built went back to Boeing for the modifications.
 
Max Q
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RE: B777 "Tailwheel"?

Sat Dec 10, 2011 12:52 am

Quoting Viscount724 (Reply 27):

The 707 modifications required by the UK involved both the ventral fin plus the approximate 3 foot taller fin. The taller fin wasn't a separate later modification. The ventral fin was eliminated on later production 707-320B/Cs but the taller fin was standard on all 707s and 720s. Those already built went back to Boeing for the modifications.

Thanks for the Clarification Viscount, I got that a bit mixed up !

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