34R Not Available - QF Blows tyres

[Ken K]

That's what the balanced field requirement is for.

[Mick F]

I'm not an expert on heavy jet operations Phillip, so excuse me if I'm feeding you rubbish, however because of the short runway, V1 would have been earlier than usual to permit a safe RTO, . V1 is always different, because it is based on several things such as the runway length, weights, atmospheric conditions, etc. etc.

Mick

[Philip Argy]

Thanks, Mick - appreciate the explanation. Great thing about this Board is how there's usually someone who knows stuff others don't so we can all learn from each other.

[Will T]

Philip,

Mike's got it in one.

To simplify a fairly complex subject:

The aeroplane needs to be able to:

- accelerate, suffer an engine failure immediately prior to V1 (the decision speed) and then stop on the remaining runway
- accelerate with all engines to V1, then stop on the remaining runway
- accelerate, suffer an engine failure immediately prior to V1, continue to accelerate past V1 with an engine failed, and reach 35' above the end of the takeoff distance available

among other things.


As such, the V1 speed is adjusted according to aircraft weight, ambient conditions, and of course runway length. If the runway length available is such that the aircraft won't be able to meet one of the above criteria, the weight needs to be reduced until it does.

Whenever the runway is 'WET' (as given on the ATIS, for example), a further reduction in V1 and/or weight is usually applied. On the 744, we don't apply a weight penalty, but reduce our V1 by 10kts. This means that we have to make a decision to STOP/GO earlier in the takeoff roll, and takes account of the fact that a wet runway requires more stopping distance than a dry runway. In other words, the reduced V1 'biases' the takeoff towards the 'GO' case.

There's a speed, called Vmcg (Minimum Control - Ground), which V1 cannot go below. Below Vmcg, there is insufficient rudder force available (due to the lower airspeed) to counteract the assymetry caused by a critical engine failure, and so it is obviously unsafe to continue a takeoff under those circumstances, even though the difference between V1 and Vmcg may only be quite small. Whenever the theoretical V1 is less than Vmcg, we make V1 = Vmcg, which effectively biases the takeoff towards the 'STOP' case.

It's complex stuff, and all this before we even get into Balanced Fields

Will

[Philip Argy]

I'm learning fast - thanks, Will!

So, looking again at David's photo (http://www.airliners.net/photo/Qanta...438/0260864/L/), rotation has apparently been delayed until the last few metres of runway, which would mean that the takeoff roll went well beyond V1 as you've explained things. Doesn't that create a risk of something going wrong after V1 that would be avoided if rotation occurred as soon as possible after V1?

Or is 34R so short that rotation with a 744 really can't occur before the last few metres of runway?

[Nathan Long]

Philip,

Don't forget that because of the angle and the use of a long focal length lens, the length of available runway appears to be less than it really is. See this document (page 16) about how far the Fixed Distance Marking must be from the threshold:

http://www.casa.gov.au/rules/1998casr/139/139m08.pdf

In this case, there appears to be at least 300m of runway remaining prior to the threshold.

[Philip Argy]

I'm going right out on a limb here wondering aloud if it really is YSSY RWY 34R (the photo shows grass where white concrete should be?) or else to suggest that 34R is non-compliant (the chevrons aren't yellow as 8.3.2.2 appears to prescribe!).

Can we use the runway edge lights to calibrate the distance? On the western edge of the runway I count 5 edge lights after the final taxiway - does anyone know what their spacing is? That presumably would give us an accurate measure of how much runway was really left?

[Grant Smith]

Originally Posted by Philip Argy

I'm going right out on a limb here wondering aloud if it really is YSSY RWY 34R (the photo shows grass where white concrete should be?)

[Nathan Long]

1. Yes, it really is YSSY 34R.

2. As for it's official compliance, I am not in a position to say, but there are yellow chevrons in the bottom left hand corner marking the start of the runway (the angle of the shot makes them appear as straight lines). 16L appears to be marked as per the requirements for a permanently displaced threshold (section 8.3.9). This part of the runway cannot be used for landing on 16L, but can be used for takeoff on 16L (and I assume take-off on 34R). As for the runway light spacing, Nigel may (should?) know the exact distance but it would be somewhere between 55 and 60m.

[Nigel C]

60 metres between runway edge lights is the distance used for RVR's at YSSY.

As for the chevrons layout, check here http://maps.google.com.au/maps?hl=en...07253&t=h&z=17

Cheers