The Inertia Factor

[wsherif1]

In a previous post I stated that, "The wake turbulence behind the 747 in the AA 587 accident could be compared to a tornado, and you know what damage a tornado can do." One chap pointed out that the houses on the ground are anchored to a foundation and that the aircraft are not. His point is well taken, the aircraft is free to move in the air. However, the amount of motion imparted to a light aircraft, by a certain applied force, will be considerably greater than a larger aircraft mass.

The 747 involved in the TWA 800 accident was of considerable mass and thus was not accelerated in motion, but rather absorbed a large percentage of the wake turbulence force in the structure! At 2031.12, the time of the wake encounter, a 13.5 foot section of the keel beam fell out of the aircraft, along with a number of other items, including the two forward bulkheads of the center wing fuel tank. None of these items exhibited any soot, fire or explosive damage. Eight seconds later the FDR stopped recording and the two clocks, in the cockpit, also stopped when the explosion occurred at 2031.20!!

Will special ATC handling of the Airbus "Jumbo Jet" be required???

Cheers

ws

[Jerricho]

Wsherif you make an interesting point.

While there has been intensive research regarding wake turbulence, particularly on final approach, there are instances when the "minimum" standard isn't enough (particular wind conditions etc). And as there are 5 wake categories in the UK, maybe there will be the introduction of a 6th?

I saw a nasty little problem not that long ago involving the at the time new A340-600 being followed by an MD-80. The following was about 7.5 miles behind the heavy, and by the sound of the R/T transmission signalling the pilot's intent to turn out of the wake, things were not all rosy on the flight deck. Of course, our seperation standards are a minimum standard, and it says in the book about being increased if deemed necessary.

[LEM]

One chap pointed out that the houses on the ground are anchored to a foundation and that the aircraft are not.
I was the chap, but you didn't get my point correctly: the fact is the sideways vector of the little "tornado" will hit the houses at a 90° angle, because they are stationary, not because they are anchored to the ground.

When it comes to and object moving rapidly, the sideways vector has to be combined with the forward vector (the speed of the airplane vector), thus the resultant force vector will hit the object at a very low angle, around 10-20° roughly in this case, not 90° degrees anymore.

Thus the force of the "tornado" will have little effect on the lateral walls of the house...


I'm glad you insist with your theories, it gives me the opportunity to improve my english grammar... :rolleyes:

[wsherif1]

Lem

Your comment,

"Thus the force of the "tornado" will have little effect on the lateral walls of the house."

Whatever the angle of the force striking the large vertical stabilizer and rudder it was still recorded as a force of 0.8 Gs!!! The aircraft went into a steep left bank and nosed down 30 degrees! A textbook example of a Dutch Roll!

The large, twin engine jet transport design, due to its requirement for a large vertical stabilizer and rudder, to counter the yaw in an engine out on T/O, is now an extremely sensitive weather vane!

The recorded movements of the rudder are an indication of the forces also striking the vertical stabilizer, which has now become a large, flight control surface! (Not under the control of the pilot.)

At some point in time, the linkages to the rudder actuators are severed and now the rudder is free floating and not available to the pilot! (There are no rudder actuator linkages in view in the picture of the vertical stabilizer, being hauled up from the recovery barge. The rudder was found in four pieces!) There is no right rudder input, by the pilot, to assist the full right aileron control input, in the attempted recovery maneuver!

The rudder inputs were not commanded by the pilot!!! Despite Airbus claims!!!

Cheers

ws