2H4
Topic Author
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Tailstrike Avoidance

Sat May 21, 2005 2:09 pm

A post over in the Civil Aviation forum got me thinking....

During no-flaps landings in particularly long aircraft, such as the 777-300, A340-600, Q400, etc, what measures are taken to avoid tailstrikes?

The relatively nose-high attitude during landing must make this a real concern...


2H4


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Newark777
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RE: Tailstrike Avoidance

Sat May 21, 2005 3:27 pm

Well, I believe that in at least the 773 there are computer controls that prevent the tail from striking, but I do not know much about the technology, or whether it is present in the other aircraft.

Harry
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CosmicCruiser
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RE: Tailstrike Avoidance

Sat May 21, 2005 10:02 pm

The pitch attitude is high but not to the extent that you would hit the tail. I always preface my statements by saying "from the jets I know" so most jets hit the tail somewhere around 10-12 deg. nose up. Eg. The MD-11 flight manual states that in a no flaps/no slats app. do not hold the a/c off and make a normal flare. Make only a small flare to arrest the sink and fly it on. Mainly this to prevent floating down the rnwy.
 
PhilSquares
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RE: Tailstrike Avoidance

Sat May 21, 2005 11:17 pm

First of all, I don't think you'll find any of the aircraft you mention doing "no flap" takeoffs. There just isn't enough runway! So, that take care of the tail strike problem.
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2H4
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RE: Tailstrike Avoidance

Sun May 22, 2005 12:33 am

Quoting PhilSquares (Reply 3):
First of all, I don't think you'll find any of the aircraft you mention doing "no flap" takeoffs. There just isn't enough runway! So, that take care of the tail strike problem.

I wasn't implying they would be performing no-flaps takeoffs. I was referring to tailstrikes during landing. American had a rash of tailstrikes during landing in the A300 several years back, mainly due to unstabilized approaches and bounce recoveries.

If a no-flap landing requires a higher deck angle during the flare, it seems the longer aircraft would be prone to tailstrikes during landing. Just trying to find out what measures are taken in these aircraft to prevent it from happening.


2H4


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AJ
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RE: Tailstrike Avoidance

Sun May 22, 2005 1:36 pm

Hi 2H4, the 767 I fly is geometry limited in the -300 version.

The flight crew training manual mentions the following about tailstrikes on landing:
"A tailstrike on landing tends to cause more serious damage than the same event during takeoff.....the tail can strike the runway before the landing gear, thus absorbing large amounts of energy for which it is not designed."
The following factors are considered critical:
- Unstable approach,
- Holding off in the flare,
- Trimming in the flare,
- Mishandling of crosswinds
- Over rotation during go-around.

As for flapless landings the advise is minimal flare to avoid tailstrike. The manual then advises slight forward pressure to touch down in the correct zone.

A factor that we have seen on the line that has caused tail strikes is when the speedbrake lever is raised rapidly after a failure to auto-deploy. If the pilot flying is not prepared for the pitch up it can cause tail skid contact.

Cheers.
 
2H4
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RE: Tailstrike Avoidance

Sun May 22, 2005 2:04 pm

Thanks for the info, AJ. That's exactly what I had in mind. Greatly appreciated.


2H4


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andz
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RE: Tailstrike Avoidance

Mon May 23, 2005 12:48 am

some get pretty close on takeoff!


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kaddyuk
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RE: Tailstrike Avoidance

Mon May 23, 2005 8:18 am

I belive that the A346 anti-tailskid technology works on both landing and takeoff... but when it fails, its very easy to scrape the tail...
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Starlionblue
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RE: Tailstrike Avoidance

Mon May 23, 2005 1:32 pm

Quoting Kaddyuk (Reply 8):
I belive that the A346 anti-tailskid technology works on both landing and takeoff... but when it fails, its very easy to scrape the tail...

When it fails? Well, it's probably not that common an occurence, or? And in any case, care should be taken anyway. It's worse if computer control of the elevators should fail. The 346 is so long that the elevators move to decrease stress on the fuse from bending, and to avoid resonance vibrations.
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kaddyuk
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RE: Tailstrike Avoidance

Tue May 24, 2005 12:02 am

Quoting Starlionblue (Reply 9):
Well, it's probably not that common an occurence, or? And in any case, care should be taken anyway.

1) Nope its not a common occourance
2) Care SHOULD be taken, but sometimes it isnt and the system acts as a fail safe...

Normally two or three factors contribute towards an incident... not just one...
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Jetlagged
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RE: Tailstrike Avoidance

Tue May 24, 2005 12:53 am

Quoting 2H4 (Reply 4):
If a no-flap landing requires a higher deck angle during the flare, it seems the longer aircraft would be prone to tailstrikes during landing. Just trying to find out what measures are taken in these aircraft to prevent it from happening.

There's no reason the deck angle will be any higher. Vref with no flaps will be much higher, but the angle of attack, and so the deck angle, will be much the same. If anything having leading edges devices deployed allows you to pull a higher angle of attack, so in theory you have more chance of a tailstrike in that configuration than with flaps and slats up.
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2H4
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RE: Tailstrike Avoidance

Tue May 24, 2005 9:46 am

Quoting Jetlagged (Reply 11):
There's no reason the deck angle will be any higher. Vref with no flaps will be much higher, but the angle of attack, and so the deck angle, will be much the same.

Ahhhh....good point. For some reason, I was assuming identical approach speeds, in which case the deck angle would be greater. I forgot to take the increased speed (and the resulting affects on AOA) into account.

Thanks for pointing that out.


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AJ
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RE: Tailstrike Avoidance

Tue May 24, 2005 3:11 pm

Quoting Jetlagged (Reply 11):
There's no reason the deck angle will be any higher.

When the flaps are at five or greater on the 767 the inboard aileron droops, designed to lower the nose attitude on approach. On a flapless approach this effect is gone leading to a shigher attitude than normal. I've done them in the simulator, they are very entertaining!

The final approach is flown below the normal clean speed (Vref30+50 instead of +80). From the FCTM "Final approach body attitude will be approximately four degrees higher than normal". Mr Boeing says to "fly the aeroplane onto the runway", no mixing of words!
 
scarebus03
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RE: Tailstrike Avoidance

Thu May 26, 2005 9:44 am

On the A320 series to prevent tail strikes the flight control computers are programmed. But in the early days of the 321s I believe tailstrikes were quite frequent until the computers were modified. However this is a secondary system as the pilot has overall control. Also had several strikes with the 737-400 in DUB, Which is why they have a collapsable cartridge on the belly under the tail.
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sunrisevalley
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RE: Tailstrike Avoidance

Sun Jun 12, 2005 9:29 am

I am not sure how widely the report on the tail strike of SQ286 at AKL was deseminated.
For those interested go to :
www2.taic.org.nz/InvDetail/03-003.aspx - 25k - 9 Jun 2005

Clearly there are software inadequacies which allowed incorrect data to be input by the pilots and not queried.
I wonder if the accident at Halifax was a result of the same set of circumstances? As I understand from the preliminary report the investigator was puzzled by the power settings used.

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