Afriqiyah Airbus 330 Crash
Join Date: Jan 2008
Location: Torquay UK
Age: 95
Posts: 163
Likes: 0
Received 0 Likes
on
0 Posts
Basic Aerodynamics
Garage years,
Once flaps are down Centre of Pressure moves aft, there is a requirement for a strong down force from tail trim and /or elevators. Loss of this down force is far more significant than pitch up from engines particularly if they are still winding up.
Once flaps are down Centre of Pressure moves aft, there is a requirement for a strong down force from tail trim and /or elevators. Loss of this down force is far more significant than pitch up from engines particularly if they are still winding up.
SkyGod
Join Date: Aug 2000
Location: Palm Coast, Florida, USA
Age: 67
Posts: 1,542
Likes: 0
Received 10 Likes
on
1 Post
Some folks are, some aren't. Some are reserving judgement in favour of curiosity.
Where does that conclusion take us?
Blame concludes the dialogue
Sorry I can't be more philosophical, been flying airplanes for too long I guess.
No time for touchy feely stuff when you are just about to hit the ground at great speed.
Join Date: May 2010
Location: Scotland
Posts: 13
Likes: 0
Received 0 Likes
on
0 Posts
I agree entirely PJ. Of course the pilot is part of the whole picture, but he is not the entire picture in an accident. Even if he was to blame, we need to look at all the aspects of the accident if we are to prevent a repetition. To use one example: the Panam /KLM tragedy in Tenerife. If we said the pilots were incompetent and that’s why that crash happened and left it at that, then that would have been futile. However, since that accident we have learned to repeat and confirm take off clearances.. that is objectiveness. Blame is NOT objective. Blame is a nasty concept as you say. It equates with victimisation, bullying, bigotry and even narcissism in proving that you know better than the erring pilot . Anyone who expresses those sentiments against his fellow pilot (a dead one at tha) has not a clue in my opinion.
TowerDog;
Yes but of course that isn't the time to be doing flight safety work either!
In any case, it's not "touchy-feely new-age-nice-guy" stuff, this is the stuff that flight safety work is now made of and is the intent behind SMS. The words aren't familiar because of habit not because they're not relevant. I am absolutely certain you understand this and the approach taken...not trying to say anything but general stuff that may help some who are reading this kind of discussion for the first time to see where most of the industry is intent on heading.
Cheers! PJ2
No time for touchy feely stuff when you are just about to hit the ground at great speed
In any case, it's not "touchy-feely new-age-nice-guy" stuff, this is the stuff that flight safety work is now made of and is the intent behind SMS. The words aren't familiar because of habit not because they're not relevant. I am absolutely certain you understand this and the approach taken...not trying to say anything but general stuff that may help some who are reading this kind of discussion for the first time to see where most of the industry is intent on heading.
Cheers! PJ2
SkyGod
Join Date: Aug 2000
Location: Palm Coast, Florida, USA
Age: 67
Posts: 1,542
Likes: 0
Received 10 Likes
on
1 Post
Yes but of course that isn't the time to be doing flight safety work either!
The person you are addressing certainly doesnt sound like a pilot to me.
Say it loud and clear if you are questioning my qualifications.
Couldn't care less...
In the first picture with the tail http://www.pprune.org/5699903-post611.html there is a bigger part, looking like a main gear strut, the lower part with the wheel sheared off?
Here a picture from the whole assembly http://commondatastorage.googleapis....al/7296126.jpg, note the three hollow connection bolts, which can also bee seen on the crash picture if you zoom into it.
Would that tell us something concerning the way of first impact?
franzl
Here a picture from the whole assembly http://commondatastorage.googleapis....al/7296126.jpg, note the three hollow connection bolts, which can also bee seen on the crash picture if you zoom into it.
Would that tell us something concerning the way of first impact?
franzl
quidquid excusatio prandium pro
Join Date: Jun 2001
Location: New York
Posts: 349
Likes: 0
Received 0 Likes
on
0 Posts
Dont waste bandwidth PJ2. The person you are addressing certainly doesnt sound like a pilot to me. Honestly.
Tiresome comments by young sprogs with reputations to forge on this forum really don't contribute to the collective intelligence and experience being brought to bear on this accident.
Last edited by bugg smasher; 19th May 2010 at 00:10.
Join Date: Mar 2009
Location: Chicago, IL, US
Age: 73
Posts: 48
Likes: 0
Received 0 Likes
on
0 Posts
I am equally amazed that anyone at all escaped this accident with their life, as the little boy(?) did. I cannot grasp how he survived the sheer destruction of this magnitude. Would be interesting to note, for me anyway, where the 10 year old was sitting at the time. Not that it really matters but did his location have something to do with his survival? Or was it just a matter of plain ol' good luck?
All that being said, in this accident the largest section of the cabin that remained was the tail. Once separated from the balance of the aircraft, this section had would have offered a high-drag, low-lift profile with no thrust from the engines to offset it. Contact with the ground would occur rapidly, if it were not already in contact at the point of breakup. The final resting position of the tail requires it to have rotated at least 180 degrees, during which aerodynamic drag would have further increased. Until we know where along the airframe the tail separated, it isn't possible to say how much of the forward end of the tail section was consumed by contact with the ground. However, all these factors, plus the lack of post-crash fire in this area, suggest that the tail provided best combination of protection and deceleration in this accident.
The smaller size of a child also reduces the moment arm as the upper body rotates forward and downward around the seatbelted waist, as well as reducing the potential impact of the head against the seat in front. The same factors might be of some value in the tumbling that may have also taken place. These factors are somewhat offset by the weaker bone structure, especially with respect to the skull. As I recall that the child suffered multiple leg fractures which required surgery.
Join Date: Jun 2001
Location: Rockytop, Tennessee, USA
Posts: 5,898
Likes: 0
Received 1 Like
on
1 Post
Know who Towerdog is, very experienced 747 skipper of NYC Tower Air fame, long years in hard conditions, planet-wide ops, survivor material, worth his weight in aviation gold.
Danny has had to take him to the woodshed a couple of times over the years for lack of political correctness though...
WilyFlier:
The pitch moment due to the flaps will depend on the CofG relative to the Center of Pressure. If the CofG is aft of the CofP then the pitch movement will be up, however, (and as I continue to assert will be the case with the tail torn off), if the CofG is forward of the CofP, then this will produce a significant pitch down movement. That, combined with the complete elimination of any pitch authority due to the loss of the tail, would doom the aircraft more than certainly.
-GY
Once flaps are down Centre of Pressure moves aft, there is a requirement for a strong down force from tail trim and /or elevators. Loss of this down force is far more significant than pitch up from engines particularly if they are still winding up
-GY
Join Date: Mar 2008
Location: KHPN
Posts: 13
Likes: 0
Received 0 Likes
on
0 Posts
Here's a helpful view of the final approach to rwy 9 - skip to 3:45 or so, as the mosque appears at 4:00.
YouTube - Landing at Tripoli International Airport, Libya
YouTube - Landing at Tripoli International Airport, Libya
Join Date: Sep 2000
Location: Bielefeld, Germany
Posts: 955
Likes: 0
Received 0 Likes
on
0 Posts
Puzzled
I have read most of the posts here since last week, and would like to express my appreciation for contributors who have kept the ratio of information to blather as high as PPRuNe used to be, and far higher than anything in recent memory (which extends back to July 2007).
People seem to think the tail hit first. There is a puzzle with that, which I raised with PJ2 privately.
Pitch angle for a tail strike first (bogies tilted, shock absorber extended) is 16° wings-level and 17.5° with 5° bank, and it doesn't go below 16° again until you are 13° AoB.
And the aircraft is descending. So add, say, 1°? That makes AoA at least 17°. High AoA protection is always active. I don't know what AlphaMax and AlphaProt are for that config or weight (I do have a query out). But how much higher than 17° can AlphaMax possibly be?
PJ2 suggests that you can pitch up to 15° on go-around. Sure, I would think, if the aircraft is ascending, which it usually is before the pitch-up gets to 15°. But this one wasn't, obviously. PJ2 also suggests the tail can hit first if there is say 2m of rising ground. I am not sure about that, since the bogies have gone over that same piece of ground a few fractions of a second before and apparently not left a trace (I note they are outside the line of the tail cone), so that still means the AC had a pitch angle of 16° or above, providing its AoB was 13° or less.
In short, I think there are some figures here that don't yet make sense for what is emerging here as a consensus CFIT scenario. And if it wasn't CFIT, there is nothing yet here to suggest how LOC may have occurred.
PBL
People seem to think the tail hit first. There is a puzzle with that, which I raised with PJ2 privately.
Pitch angle for a tail strike first (bogies tilted, shock absorber extended) is 16° wings-level and 17.5° with 5° bank, and it doesn't go below 16° again until you are 13° AoB.
And the aircraft is descending. So add, say, 1°? That makes AoA at least 17°. High AoA protection is always active. I don't know what AlphaMax and AlphaProt are for that config or weight (I do have a query out). But how much higher than 17° can AlphaMax possibly be?
PJ2 suggests that you can pitch up to 15° on go-around. Sure, I would think, if the aircraft is ascending, which it usually is before the pitch-up gets to 15°. But this one wasn't, obviously. PJ2 also suggests the tail can hit first if there is say 2m of rising ground. I am not sure about that, since the bogies have gone over that same piece of ground a few fractions of a second before and apparently not left a trace (I note they are outside the line of the tail cone), so that still means the AC had a pitch angle of 16° or above, providing its AoB was 13° or less.
In short, I think there are some figures here that don't yet make sense for what is emerging here as a consensus CFIT scenario. And if it wasn't CFIT, there is nothing yet here to suggest how LOC may have occurred.
PBL
Per Ardua ad Astraeus
Join Date: Mar 2000
Location: UK
Posts: 18,579
Likes: 0
Received 0 Likes
on
0 Posts
PBL - reducing to basics, and ignoring the 'doubts' on the AB control laws, we have to accept that the tail broke off well before the rest of it came down and if the Alitalia is to be believed it was well nose-down at impact. As said many times, all pitch/power etc is recorded up to loss of tail section at least
Per Ardua ad Astraeus
Join Date: Mar 2000
Location: UK
Posts: 18,579
Likes: 0
Received 0 Likes
on
0 Posts
No - I had a brief 'stab' earlier but it is really pointless when all will be revealed in matter of days. IF there is still a 'puzzle', as with AF447, then yes, it woud be worthwhile to pontificate..
Join Date: Dec 2005
Location: At home
Posts: 244
Likes: 0
Received 0 Likes
on
0 Posts
Can you solve the "puzzle"?
Speculation #2: A panic pull on the stick leading to a g-stall / high AoA and sink rate. Have no idea if control laws would allow this. Also the actual airspeed (margin to Vs) obviously plays a role here.
But FDR/CVR will obviously tell.
Join Date: Jan 2008
Location: uk
Posts: 857
Likes: 0
Received 0 Likes
on
0 Posts
I have no idea why they wouldn't be down, but then this wasn't a normal approach and landing, otherwise we wouldn't be here.