Mar 262008
 

Overnight, or rather late yesterday afternoon our time, QANTAS flight QF12, VH-OJE, known as ‘Wunala Dreaming’ due to it’s livery, underwent an ‘aborted take-off’ at Los Angeles International.


An ‘aborted take-off’ is not a usual procedure, but one which pilots train for and aircraft computer systems are programmed to accomplish as safely and efficiently as possible. Here’s my beef with MSM reporter for the Herald Sun, Evelyn Yamine. Read her article, which I have to say is far more embellished than Associated Press or Fox News, and you’ll notice the claim…

“The nose of the plane had already lifted off the ground and passengers were heavily jostled as it hit the tarmac at full speed. “

The nose of the plane had already lifted off the ground. Now, whether this is fact, which I strongly doubt, or conjecture based on the claims of frightened passenger, Samantha Thomas, the actuality of the situation had the plane’s nose left the runway, would have been a take-off, ‘go-around’ procedure and landing again at LAX. Not the reported ‘aborted take-off’. I’ll explain.
A fully loaded Boeing 747-400 weighs in at around 950,000 lbs, depending on cargo, passenger numbers, fuel distribution and so on. QF12 was lighter than that, having a passenger manifest of 232 people. Take-off speed varies depending on climatic conditions, wind direction, air density, aircraft weight and balance and these days, is calculated by an on-board flight management computer for each flight. We’ve all seen movies where the Pilot-in-Charge holds the yoke and the Co-Pilot assists with throttle management and instruments. Whether or not that’s reality is a moot point in the current age of computer assisted take-offs and landings. What we hear them say are obscure things like “V1……Vr (or Rotate)……V2…….Positive Climb” and so on.
V1 is defined as …

“critical engine failure recognition speed. V1 is the minimum speed in the takeoff, following a failure of the critical engine at VEF, at which the pilot can continue the takeoff with only the remaining engines. Any problems after V1 are treated as in-flight emergencies. In the case of a balanced field takeoff, V1 is the maximum speed in the takeoff at which the pilot must take the first action (e.g., apply brakes, reduce thrust, deploy speed brakes) to stop the aircraft within the accelerate-stop distance and the minimum speed at which the takeoff can be continued and achieve the required height above the takeoff surface within the takeoff distance. In this context, V1 is the takeoff decision speed.”

Vr is defined as …

“rotation speed. The speed of an aircraft at which the pilot initiates rotation to obtain the scheduled takeoff performance. It must be greater or equal to the V1 speed.”

V2 is defined as …

“the minimum safe speed in the second segment of a climb following an engine failure. Also called takeoff screen speed and sometimes, takeoff safety speed, although as the second climb segment indicates, V2 is an after takeoff speed frequently achieved shortly after rotate (Vr) as the aircraft accelerates. The engine failure case that is taken in the calculation of V2 is that of the “most adverse engine” because the effects of different engines when failed, differ. The calculation of V2 also includes set margins over the stall and other safety factors are built in as well.”

That’s the techo bit. Let’s get back to Evelyn’s overly hysterical piece in the Hun. She writes that the aircraft’s nose was off the ground, which to me indicates the aircraft’s flight management system had already accepted and exceeded V1, the decision speed at which an aborted take-off would/could be actioned by the pilot if he/she so desired. If the plane’s nose had lifted, clearly the flight management system would have also accepted and exceeded Vr or rotation speed, which by default has to be greater than V1, especially in the case of a laden Jumbo Jet. If that were the case, and the nose had lifted, the aircraft would be committed to a take-off for pure safety reasons alone. The pilot in charge would be aware of this, as would the second pilot and the flight management system would have practically required this to occur.

LaxAirportDiagram2.jpg

The reported event took place on, and subsequently blocked LAX’s ‘Southern Runway’, which would be 25L given that of the four runways there, it’s the widest at 200 feet. At 11,095 feet, it’s not the longest runway available, but only by less than 100 feet. With an estimated V1 of around 190 knots indicated and your average take-off run to Vr taking 40 to 50 seconds depending on load, it’s inconceivable that QF12 would have aborted after Vr. In fact, I’d go so far as to say it would be impossible. The flight management system wouldn’t allow it. Two-point-one miles of runway might sound long, but when you’re travelling at 190 knots that length runs out in less than 35 seconds. If the nose of the aircraft had lifted, she would have taken off on a go-around procedure. If, for whatever reason, she wasn’t able to complete her take off, we’d be reading about a massive loss of life situation in LA this morning.
So, after all of the above, I can only say that Evelyn’s copy is absolute trash, based entirely on speculation and inaccurate reporting from other media sources. It’s pathetic just what lengths the MSM will go to in order to speed up the news on a slow day.

  One Response to “Another Gaff by MSM”

  1. And 25L is used for landings at LAX, not take offs….