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American Airlines Two Planes Grounded After Tail Strikes

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American Airlines Two Planes Grounded After Tail Strikes

Old 21st Jan 2011, 05:14
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Since I have never flown aircraft long and powerful enough to whack their tails, can somebody explain to me what causes tailstrikes?
In theory, any aircraft could suffer a tail-strike during Take-off or Landing (except taildraggers).

A tail-strike occurs when the horizontal stabilizer (Tail) is capable of generating a sufficient downward force that the lower tail section of the aircraft is brought into contact the ground before the aircraft is able to fly. Think about basic flight theory - angle of attack and stalling.

In other words, exceed the "Ground" angle of attack and a tail-strike occurs, just like the exceeding the "Air" angle of attack will cause a stall.

It generally happens when the aircraft is either rotated, or flared, at a speed below optimal for the conditions (Vr, Vref, etc) It can also happen if the pilot is aggressive on the controls (Over-rotation,etc), but in this case the tail-strike is caused by aircraft's geometry over reaction time, not really by the aerodynamics.

Some aircraft would appear more prone than others based on their design. The 727, some 737's, 767 and some others, have limited tail/runway clearance and subsequently were manufactured with a "Skid" which would offer at least some damage protection.
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Old 21st Jan 2011, 05:16
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This is worse than a string of bad luck. Something isn't right at AA and they need to get to the bottom of it.
Yup, but true to form at AA, they are in the deny/deny/deny mode.
Isn't going to change, either, unless the FAA suspends their operating certificate.
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Old 21st Jan 2011, 05:18
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think China had a TS not too long ago, in a 340. At the end of the Runway, and with bugs missing a few legs, ... or cost the Company an airplane, or at least a gazillion Euros, (Yuan). Live, and learn Bartending.
I'm pretty sure that this was an Emirates A340 taking-off from Melbourne, Australia.
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Old 21st Jan 2011, 05:39
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tailstrike

We had a tail strike at our outfit(737 NG) about a year back on takeoff accompanied with stick shaker as the copilot had made wrong takeoff speed calculation( max Reduced thrust) at max takeoff weight and the relatively new captain didn't notice the error in his haste to get going.

Luckily, other than structural damage and a few frightened pax , the aircraft made it OK. Both pilots were grounded for a while and after investigations and corrective training are now flying. A rule of thumb I use(taught to me by a senior check pilot) to cross-check the speeds is the V2 speed set in the MCP window should be approximately 20 knots less than takeoff weight ...eg. if T/O weight on the -800 is 70 tons ( 70-20=50) , therefore 150 knots approx. For the -700 , reduce by 25 .

masalama.
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Old 21st Jan 2011, 05:58
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the rule of thumb is a good idea however some of the recent tailstrikes have occured due to incorrect weight being entered in the first place... garbage in...
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Old 21st Jan 2011, 18:17
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Captain Greg Smith is the LAX Director of Flight. Which makes him the big cheese for the base.
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Old 21st Jan 2011, 23:20
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Captain --- --- is the LAX Director of Flight
No reason to put his name on internet, is there? (Next time it's you!)
BTW, what is he called now?
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Old 22nd Jan 2011, 01:32
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No reason to put his name on internet, is there? (Next time it's you!)
BTW, what is he called now?
His name was in post #1 which means it was also in the WSJ.
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Old 22nd Jan 2011, 23:06
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The 757 rotation technique as taught at AA is to smoothly begin rotation AT VR trying for 2.5 degrees per second to 10 degrees. The aircraft should be airborne during those 4 seconds and rotation is smoothly continued to maintain V2 +15 which requires 18-20 pitch attitude.
At VLO and 10 degrees pitch, the 757-200 tail (All AA 757's are -200s) is about 33 inches above the tarmac with the struts extended. Tail contact takes about 12.5 degrees with struts extended. With struts fully compressed, which they would NOT be for any TO the tail will contact at 10 degrees.
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Old 22nd Jan 2011, 23:18
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His name was in post #1 which means it was also in the WSJ
Sorry, thought they were only talking about "the chiefpilot". Later on in the article his name was indeed mentioned.
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Old 23rd Jan 2011, 00:01
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Tail strikes are not limited to takeoff situations – they occur during landings as well. As PappyJ very correctly states:
In other words, exceed the "Ground" angle of attack and a tail-strike occurs, just like the exceeding the "Air" angle of attack will cause a stall.
It generally happens when the aircraft is either rotated, or flared, at a speed below optimal for the conditions (Vr, Vref, etc) It can also happen if the pilot is aggressive on the controls (Over-rotation,etc)…
However, I don’t completely understand the balance of PappyJ’s comment …
in this case the tail-strike is caused by aircraft's geometry over reaction time, not really by the aerodynamics.
Any tail strike involves aerodynamics – the way the controls are manipulated to influence the aerodynamic characteristics of the airplane. For example, if the controls are moved abruptly, not giving the airplane a chance to be influenced by the changing airflow … like a continuing rotation on either takeoff or landing … and the airplane may well achieve a pitch attitude that would place the tail structure appetizingly close to any “airplane-eating runway” on the planet.

Certainly it can’t be the training at AA, as all airlines in the US are required to comply with the training that is contained in part 121 of the FARs … and that would include AA, right?
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Old 23rd Jan 2011, 00:44
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As a sidebar comment, I know of at least two airlines which provide the crew with flight data information right after takeoff and after landing. The speed, RA, pitch attitude, pitch rate (deg/sec) throughout the maneuver), Vertg, Descent Rate are all provided to the crew for their examination if they wish. Providing this information to the crew immediately, gives them something to learn from if a rotation or a flare was slightly outside normal. This use of flight data has already reduced tailstrikes at these two airlines. This data remains the crew's to use/dispose of as they deem.

Typical FOQA Programs have events which track how close an aircraft came to tailstrike on liftoff or on the flare at landing, as well as monitoring rotation rates, (almost all the events I've seen were very slow rotation rates...between 0.8 and 1.5deg/sec and took a long time to get the pitch to 15deg +).

Tailstrike on the approach is most certainly aerodynamic in nature - we have seen higher risk of tailstrike with a quartering tailwind and the airspeed right on the bug, (Vref +5 or Vapp on the 'bus). There is a FOQA event that monitors flare times as well; Any flare longer than 8 to 10 seconds can be an indication of higher risk of tailstrike and here is where aircraft geometry can come into play.

Both the FOQA events and the data link information to the crew are attempts to deal with the problem of tailstrikes and are obviously preventative. Of course, in any actual incident, all data is available to the airline safety investigation team and flight ops to see if there are training issues.
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Old 24th Jan 2011, 20:39
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Perhaps...management pilots need to stay firmly in the office, or...have a bit more regular line flying experience.
Many years ago, demonstrating new aircraft to airline and military operators around the world, while trying to make the demonstratee look (and feel) good, we always used the maxim: "watch out for Chief Pilots and Colonels".

Scene 1: lined up on the departure runway, CP of a developing world airline in the left seat, very thorough briefing complete, T/O clearance received - Me "Any questions?" - He "Yes, which one's the airspeed indicator?"

Scene 2: CP of a legacy flag carrier in the left seat, CAVOK day, calm wind, very light weight, no issues. The result - the hardest landing I ever experienced in my career and, - it happened a flash!

Chief Pilots and Colonels! And then I were one.....
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Old 26th Jan 2011, 19:35
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Originally Posted by PJ2
Tailstrike on the approach is most certainly aerodynamic in nature - we have seen higher risk of tailstrike with a quartering tailwind and the airspeed right on the bug, (Vref +5 or Vapp on the 'bus). There is a FOQA event that monitors flare times as well; Any flare longer than 8 to 10 seconds can be an indication of higher risk of tailstrike and here is where aircraft geometry can come into play.

Both the FOQA events and the data link information to the crew are attempts to deal with the problem of tailstrikes and are obviously preventative. Of course, in any actual incident, all data is available to the airline safety investigation team and flight ops to see if there are training issues.
While “flair time” may be a decent data point for discussion, it seems to me that anyone who is still “flaring” any airplane (i.e., continuing to move the nose to a higher position) after anything approaching 8 to 10 seconds is indicative of the fact that the pilot has no idea of what attitude he/she wants for the airplane to land. Said differently, that pilot likely knows not what he/she is attempting to achieve, or if he/she is just pulling on the controls “until it lands” which would be a classic case of the airplane flying the pilot. To avoid speculation, the attitude that should be sought is the attitude that would achieve level flight for the airspeed and airplane configuration at THAT time. There should be no way that the level flight attitude of any airplane, particularly when in ground effect, would require such a nose high position that it would risk a tail strike. Pulling the nose up above the attitude that would maintain level flight is only inviting something that no one would desire. Transport category airplanes are not expected to be landed “in a full stall” condition. Unless someone flies final approach at something like 8 – 10 degrees nose LOW, there is almost zero chance that a change in airplane attitude (i.e., flare) should take anything approaching 8 to 10 seconds to achieve a level flight attitude. It would seem to me that any review of FOQA data that shows any pilot flaring for something approaching 8 to 10 seconds will have already demonstrated the need for additional training – tail strike or not.
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Old 26th Jan 2011, 20:39
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So, "flair" is the culprit. Hunting (waiting) for liftoff after initiation (rotation) or T/D (landing) is not a stabilized approach. Rather simple. Is that it? Poor speed control?
 
Old 26th Jan 2011, 20:42
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I've worked for three small airlines and one really big airline. AT no time was their a discussion of "Flare" techniques or concepts.

It took seperate study on my part to learn the following:

1. Learn and be aware of the visual clues that can lead you to ''flaring'' too long. For example, when on a runway sloping downhill, if you ''keep flaring'' you will keep floating as the runway is moving away from you...

I was going to write an extended explanation, but have decided I enjoy talking about other people screwing up and if they actually learned something, the whole pprune thing would get dull.
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Old 26th Jan 2011, 20:50
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Interesting. I had assumed that all tail strikes happen as a result of overrotation on takeoff. Never occurred to me that you could have one on landing.
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Old 26th Jan 2011, 21:08
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Over rotating on take off is poor pilot technique because you did it to yourself with no outside forces. Landing and hitting the tail is poor pilot technique with outside forces. The pilot flying shouldn't be getting a tail strike unless he or she really screwed it up. I can see it happening after a bounce and screwing the recovery up but not a normal landing, no matter what the wind component is. When you fly to Hawaii once a month and get one or two landings anything can happen.

My biggest challenge was landing uphill on a short strip in Honduras in a 757 and landing in a climb. Firm landings were quite common there. It took a while to figure the climb angle needed to get a smooth touchdown.
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Old 26th Jan 2011, 21:22
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That would be what we used to call Tegoose.
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Old 26th Jan 2011, 22:33
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But wasn't it fun? Landing uphill at TGU rarely happened because of the prevailing wind so we got really good at landing north. Landing south seemed so easy, uphill, but our best landings were downhill turning final at about 100 ft to miss the hill. I really miss that place. Had a reverser not work one day but no big deal. I am waiting for the report to see how this could have affected one of our arrivals. The 757 is a wonderful airplane, lots of power and you can override everything manually. I like it as much as my beloved Lear Jets. It is hard to kill yourself in machines like that if you pay attention.
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