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Tail strike at Faro

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Old 22nd Jun 2004, 11:57
  #81 (permalink)  
 
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Hopefully not ,Engine overtemp,but your point is certainly a valid one.
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Old 22nd Jun 2004, 13:16
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Flyerstar

Rather than degenerate into the standard PPRUNE slanging match where everyone says how unknowlegealbe and unprofessional everyone else is, why do we not just accept that there are a number of professional pilots on here who are very experienced on type and have all have read the Airbus documentation? It is always disappointing that so many fellow professionals want to denegrate the other guy rather than actually learn something from the other.

I have never met you but am quite happy to accept that you may have a lot of knowledge technically about the Airbus. Please give me the benefit of the doubt that I may actually know something too. If I am wrong I am happy to be shown the error of my ways - I hope you feel the same.

I have no intention of entering into a slanging match with you on a public forum so if you really want to know how the approach speed function works, e-mail me and I will send you a spreadsheet that shows you. It will obviously surprise you to know that I actively searched out every known piece of Airbus documention including all FCOM bulletins before producing it. Once you have looked at that and spent some time looking rationally at the arguments, then if you still disagree feel free to sound off about my ignorance.

Tunneler

Thanks for the correction about it being 6 months rather than a year. There is also some merit in the argument that says that because there are only 3 321s on the fleet there is statistically much less chance of a tailstrike. Nevertheless, my own view is that GB should be commended for taking the steps they have to reduce the risk. I am defiinitely one of those who believe that there is not some hidden law which states accidents are inevitable. You can go to great lengths to ensure they do not happen and I believe GB has set a good example here.
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Old 22nd Jun 2004, 13:26
  #83 (permalink)  
 
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NSF Well put old chap!
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Old 22nd Jun 2004, 15:47
  #84 (permalink)  
 
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@NSF

I did not slander you all i said is that you are incorrect. In a gist if others read what you wrote they will get a completely incorrect picture of how GS Mini works. The irony of it all ius that some seem to encourage you to do so!

The issue is one where if i understood you well you are confusing Vapp with GS mini. VIAS guarantees the safest minimum speed. On top of that we get GS Mini which compensates for any wind effects by making sure that thrust will not go to idle in cases where we have excess speed especially on short finals. Hence your assumption that you are worse off putting in the tower speed does not make sense. One must appreciate that this system is much better than that on other aircraft. If you have read the blue bulletin you will know why. I will be happy to take up the argument with you elsewhere.
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Old 22nd Jun 2004, 19:56
  #85 (permalink)  
 
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VIAS ? - What ???

Perhaps VLS ??

Also GND Speed Mini does allow the thrust to go to idle, as I found out and posted earlier a reference to this !

Perhaps you should consult Microsoft Flight Sim Manuals !!
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Old 22nd Jun 2004, 22:26
  #86 (permalink)  
 
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Flyerstar

I have rechecked my earlier post and am sticking to my guns, and no I am not confusing GS Mini with Approach Speed. GS Mini is only one small part of the main event which is the approach speed calculation.

GS mini is only one of several approach speed protections the Airbus uses and is best thought of as the minimum groundspeed that the aircraft will be permitted to have to prevent a low energy situation. It is effectively a fixed value as long as VLS does not change which for all practical purposes it does not during an approach. Remember that the higher the tower wind, the lower is GS mini. In order for GS mini to provide meaningful protection by not permitting the aircraft speed to decay below a certain value, the value must be realistic. If you have an enormous tower wind then you will never get near that value of GSmini when the protection kicks in.

The really important issue is the approach speed and the Airbus is effectively calcluating 4 different approach speeds at any one time, 2 of which are based on GS mini. The highest of those 4 values is the one it uses and that is what is displayed on the magenta triangle the pilot sees as the approach speed target. Airbus do not formally state that, but that is what is happening.

Regarding the written explanations that Airbus give in the manuals - these are not particularly helpful as they only cover one case and do not consider such things as circling approaches for example. Without a spreadsheet or computer program of some kind which simulates the different situations that can arise using the Airbus-provided equations it is almost impossible to see what is going on. For example, what happens if there is a large tower wind and small actual wind or vice versa? What happens if you forget to activate the secondary flight plan in conditions of high wind? What happens if you put in a reciprocal wind for the tower wind? When does it not matter what wind you put in? (The answer is that for any wind of 10 kts or less, you can put in a wind from any direction and it will not affect the approach speed calculation). And so it goes on.

Coming back to my original point, if you put in a high value of tower wind on a gusty day (ie 25 kts plus) there is always a danger that you will have a significant loss of energy when that gust disappears at low level. This is because the tower wind is always assumed to be there and if it is high then you are effectively telling the aircraft to ignore everything above 15 kts. That is OK as long as the wind does not disappear, but if it does you can find yourself in a low energy situation because GSmini (which is never displayed to the pilot) is artificially low. I have seen this on a number of occasions on the 321 and it has explained a number of hard landings in gusty conditions. Once I realised what was going on, I lowered the tower wind by a few knots and the heavy landings stopped. If this all sounds wierd then just get the spreadsheet and try it yourself - you will see it really does work. Like anything else, balance is the order of the day. It would clearly not be sensible to lower the tower wind hugely because that would result in a much higher approach speed and therefore a longer landing distance plus an unacceptable float. The essence of my argument is that you should be extremely wary of puting in high tower winds (20 kts+) on a windy day.
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Old 22nd Jun 2004, 22:59
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NSF said
Once I realised what was going on, I lowered the tower wind by a few knots and the heavy landings stopped.
What do your company's training department think of your unilateral action of lowering the tower wind by a few knots to suit your landing technique NSF as this is NOT an SOP ! You can't go making you're own rules up just because you've made some pretty spreadsheets of your own. Maybe we should all change our DA by a few feet or V speeds because we just feel like it Read Blue bulletin no.47/2 "Ground Speed Mini Function" It is very clear, very specific and gives adequate examples. Flyerstar is correct in that all you are doing is misleading people with "your" spreadsheet when they should be reading the official bulletin promulgated by Airbus. If you don't like it then the correct prodedure is to go through your fleet technical captain and fleet training Captain and not to make it up by inserting the wind of your choice. In the meantime stick to sop, because if it all goes wrong and you haven't then you will be hung out to dry for non-compliance, and all the evidence will be on the DFDR.
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Old 23rd Jun 2004, 01:34
  #88 (permalink)  
 
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Flex 42

To suggest that changing your approach speed in accordance with the prevailing wind conditions is the same as changing your DA or V speeds is clearly incorrect and shows your lack of understanding of what I have said. The whole problem of GSmini is the one of knowing which tower wind to use and that is not written down anywhere. Do you use the last ATIS wind or the last steady state wind from ATC? In most cases it makes virtually no difference but there are occasions when it will. Most people have no idea what the tower wind does and by definition cannot make an informed decision of what to put in.

The changing of your approach speed by altering the tower wind to reflect reality is similar to the 'non-standard' practice of puting 3 knots on the approach speed for a 321 which many people employ and has exactly the same effect. You will not find that in any manual for any company either but it is common practice - for very good reasons. We are all after the same deal - safe flying based accurately on knowlege and experience. For example most pilots would all apply a few knots for a gusty crosswind and the decision as to how many is 'a few' would be down to the individual pilot on the day with the captain having the final say. I am not advocating an 'under the table' technique, but what I am saying is that it is reasonable to be informed as to what is actually going on in the aircraft you fly. The decision to add a few knots to your approach speed under certain conditions is entirely reasonable and there are many ways of doing that. Like I said earlier - balance is everything. The random application of 20 knots onto your approach speed would not be sensible but a few knots sometimes is. That is airmanship and good judgement which we hopefully all exercise daily.

This forum is for the balanced discussion of matters such as this, but sadly it always decays into people getting on their high horse and telling everyone else how bad they are. All I have asked for is informed insight into how something as fundamental as approach speed is calculated. You never know - it is possible that the poor soul who had the tailstrike could have benefitted from a few extra knots to avoid a low energy drop out the sky and subsequent bounce. For those that want to have understanding of this subject the answers are there. There again you can just carry on in uninformed ignorance for ever, never researching an issue properly, and just rant on to those that do.

Last edited by Norman Stanley Fletcher; 25th Jun 2004 at 00:04.
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Old 23rd Jun 2004, 02:16
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Positively amazing!!

Just think, hundreds (thousands) of pilots worldwide for years and years flew heavy jets with manual throttles, and never scraped the tail, extra long body aircraft included.

Yet, here comes newer 'technology' long body aircraft (A321) with 'computer intervention' with the power setting on landing...and bang goes the tail.

Ain't it wonderful?
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Old 23rd Jun 2004, 02:47
  #90 (permalink)  
 
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well, i,m no bus driver but what about when the tower wind is wrong ?
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Old 23rd Jun 2004, 14:01
  #91 (permalink)  
 
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I don't know anything about the bus but I always thought that the airbus computers protect the flight envelope, including limiting the pitch on takeoff to prevent a tailstrike.

Can anyone explain to me if this is true and if this is also available for landings? I'm getting a bit confused here.

Thanx
FC
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Old 23rd Jun 2004, 14:44
  #92 (permalink)  
A4

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Funnel,

The Airbus flight protection envelope will not (and is not designed to) prevent tailstrike. If you haul back on the stick, you will hit the tail - simple.

The A321 has the same wing as the A320 (but different flaps) and can land 10 tonnes heavier. I rarely fly the A321 but when I do I notice it is much more "solid" due to the higher wing loading. Not flying it too often does tend to focus the mind on pitch - especially at landing and the added 3 knots seems fairly common.

If a high sink rate materiallises just before touch down it is quite possible the aircraft will bounce. Unfortunately, this is also just as the spoliers are deploying (WoW switch) which causes a pitch up with the possibility of a three pointer on main wheels + tail.

I'm not sure the if the A340-600 has some protection because that is seriously long!
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Old 23rd Jun 2004, 14:48
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For Funnel Cloud et al who seek enlightenmnet on the Airbus at landing; selected highlights from the A321 FCOM (NB NO TAILSTRIKE PROTECTION ON ANY AIRBUS TYPES)


From FCOM 1 - Flight Controls;

PITCH ATTITUDE PROTECTION

Pitch attitude is limited to :

30° nose up in conf 0 to 3 (progressively reduced to 25° at low speed).

25° nose up in conf FULL (progressively reduced to 20° at low speed).

15° nose down (indicated by green symbols "=" on the PFD's pitch scale).



From FCOM 3 - Supplementary Techniques

LANDING MODE

The system's landing mode gives the aircraft a stabilized flight path and makes a conventional flare and touchdown. It carries out the initial approach as this manual described earlier. At 50 feet, the system memorizes the attitude, usually 3° or 4° nose up. From 30 feet down, this value washes out over eight seconds to - 2°. The result is that the pilot has to exert a progressive pull to increase pitch gently in the flare. He should pull the thrust levers back at or above 20 feet, and the landing should occur without a long flare. Touchdown quality is better and more repeatable at fairly flat attitudes. An audible "RETARD" callout reminds the pilot if he has not pulled back the thrust levers when the aircraft has reached 20 feet.

Crosswind landings are conventional. The preferred technique is to use the rudder to align the aircraft with the runway heading, during the flare, while using lateral control to maintain the aircraft on the runway centerline (Refer to SOP 3.03.22). The lateral control mode does not change until the wheels are on the ground, so there is no discontinuity in the control laws. The aircraft tends to roll gently in the conventional sense as drift decreases, and the pilot may have to use some normal cross control to maintain roll attitude.

Even during an approach in considerable turbulence, the control system resists the disturbances quite well without pilot inputs. In fact, the pilot should try to limit his control inputs to those necessary to correct the flight path trajectory and leave the task of countering air disturbances to the flight control system.

Derotation is conventional. The pilot releases the back pressure he was holding for the flare and the nose wheel comes down nicely.

Pitch trim then resets to zero.



Other Important bits from FCOM 3;

LANDING

At approximately 30 feet :

-FLARE PERFORM

-ATTITUDE MONITOR

The PNF should monitor the attitude, and call out :
"PITCH, PITCH", if the pitch angle reaches 7.5 degrees.

"BANK, BANK", if the bank angle reaches 7 degrees.

-THRUST levers IDLE

In manual landing conditions, the "RETARD" callout is generated at 20 feet RA, as a reminder. Start a gentle progressive flare, and allow the aircraft to touch down without prolonged float.

Ground clearance

Avoid flaring high.

A tailstrike occurs, if the pitch attitude exceeds 11 degrees (9.5 degrees with the landing gear compressed).

A wingtip or engine scrape occurs, if the roll angle exceeds 18 degrees (16 degrees with the landing gear compressed).

mcdude
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Old 23rd Jun 2004, 15:14
  #94 (permalink)  
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411A

Didn't the 757 suffer such regular tail strikes at one time that Boeing had to introduce special training measures to deal with it? Similar length of aircraft, similar results.

A few others:
14 September 2002 Bristol Boeing 737-800. Aircaft suffered tail strike on take-off.

15 Oct 1997 Mexico City DC-9 Aeromexico: Tail-strike on landing with severe damage / evac on runway .

8 March1996 Halifax, Nova Scotia: Air Canada 767-300. Tail strike on landing

08 December 1985 Boeing 747 Japan Airlines: The aircraft suffered an aft pressure bulkhead failure due to improper repair of bulkhead by Boeing after a tail strike in 1978.

This is just a small selection from a two minute survey. There are lot's more. Hardly fair to say that "hundreds (thousands) of pilots worldwide for years and years flew heavy jets with manual throttles, and never scraped the tail, extra long body aircraft included."

Trolling again by any chance?

Dave
 
Old 23rd Jun 2004, 15:57
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@Jet A1

If you have no idea what Vias is (Its not Vls) then I hope to God i am never a passenger when you are flying the bus (If you do fly the bus at all). I think its you who would be better off reverting to the old flight sim dear chap.

@NSF

I understand what you are signifying but you are still wrong. Remember that Vias is the max of Vapp or GS Mini+Actual wind so you are ALWAYS guaranteed a safe amount of ENERGY. I have landed the bus in 50kts of gusting HWind and seen it landed gusting 50kts of Xwind (at least till short finals) no probs with the landing or speed honestly and i always put in the wind accordning to the Latest ATIS.
Kindly send me your spreadsheet to discuss further. pm me for the email. Cheers

Last edited by flyerstar; 26th Jun 2004 at 10:02.
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Old 23rd Jun 2004, 16:37
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Flyerstar, Have you really landed a FBW in 50kts of X-wind?
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Old 24th Jun 2004, 09:22
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A4 & mcdude,

Thanks for your answers. This took away some misunderstandings I had about the bus.

FC
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Old 24th Jun 2004, 09:47
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Flyer...

Feeling's mutual !
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Old 24th Jun 2004, 11:04
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If you have no idea what Vias is (Its not Vls) then I hope to God i am never a passenger when you are flying the bus
Well I've been flying it for 5 years and I don't know what VIAS is. I think he means the IAS target that g/s mini computes during the approach. Airbus never refer to this as VIAS in any of the documentation that I have (paper FCOMS and searchable CD ROM) but do call it either IAS Target or VAPP Target. Perhaps VIAS is a company name for the same?.

Interesting thread this, I now fly all three narrowbody Airbus a/c and still much prefer the 321 over the other two. Much nicer all round than the 319 and 320, it feels more stable and planted in all stages of flight and I find it easier to land consistently than the other two. It seems easy to "over flare" the 320 and 319 but the 321 just sits down nicely in the right place pretty much every time. A few knots entered in the perf page can certainly help if the bug is a little near VLS during the approach in strong x-winds for instance.
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Old 24th Jun 2004, 17:20
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Likewise Max, I'm struggling to find any reference to Vias. Are we alone? I spent a good proportion of time today flicking through the FCOM's and company manuals, and still can't find it. Come on flyerstar, give us poor mortals who would love to know more about our jet a clue as to what it is!
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