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albertofdz
19th Aug 2012, 16:40
Good afternoon chaps;

I have been studying the new In Flight Performance section of the QRH, in particular I have paid special attention to the VAPP and landing distances calculations with failures.

At a first glance, I thought these calculations would be easier, however i'm having touble understanding certain calculations.

Let me set an example:

Imagine we suffer a dual hydraulic failure, G+B for instance, lets say that a dual leak has occured after takeoff performed using CONF 2.

According to the FCOM APPR PROC, flaps 2 will be used, and because s=2, APPR SPD will be VLS+10. This is where I get confused.

According to the new section added in the back of the FCTM, (LANDING PERFORMANCE - VAPP DETERMINATION WITH FAILURES) after using the matrix to asses the rwy condition, a VAPP and landing distance is extracted from the appropriate table. This section also states that certain procedures require the VLS to be incremented, this appears to be such a case.

However, the new IFL charts include delta VREF and landing distances for this very same failure.

The question is, what should I choose? Must I wait for the flaps to be extended and add 10kts to the VLS? Perhaps I should use the speeds extracted from the charts?

This speed calculation part is quite frankly getting on my nerves!

Some help would be ever so appreciated.

Happy landings to all.




Albertofdz

A320baby
22nd Aug 2012, 15:55
With a dual Hydraulic failure, there are summaries in the QRH, these make the calculations so much easier and faster,

For example G+B SYS LO PRESSURE

Gross weight 60T = vref 129 + 25kts = 154kts

Hope this helps

Burger Thing
23rd Aug 2012, 03:51
Hey Albert,

The new QRH is a bit strange at first. Especially the summaries have become more or less useless, because the VAPP and the Landing Distance tables are gone and one has to refer to the IFL Sections, as you stated. So what is the point of the summaries now? Right, they are frakkin' useless now :*

In the QRH version I am looking at, I see for a Slats = 2 G+B Hydraulic Failure in the IFL Failure Tables a delta VREF of 15.

So, what you could do, is to set up the FMCG for arrival and set on the PERF Approach Page Config Full. You should see your VLS speed there, or you could get the VLS speed (VREF) for Config Full from the IFL page in the QRH, for the estimated landing weight, if the FMGC hasn't been set up for the approach yet.

Then, for the case of a Slats = 2 case, the 1. increment to the VLS Conf Full is the 15 knots from the IFL Table (Hydraulic Failures). Now go and check the IFL table for the approach speeds. You will see, that for a delta VREF of 15, you might have to increase the approach speeds a bit further (1/3rd of the landing headwind). However, the total correction of delta VREF and the approach correction should not exceed 20 knots. So, let's say, the headwind is 12 knots, the VAPP would be = VLS Config Full (VREF) + delta VREF (15 knots) + approach correction (4 knots).

If the Headwind was 21 knots, then the approach correction would have to be limited to 5 knots.

For the final FMGS set up, you would select in your case then Conf 3 and enter your calculated VAPP into the PERF Landing page. However, if I am not mistaken, Airbus recommends to fly a selected speed when either Flaps/Slats are jammed.

For the landing distance, you would not have to increase it because the approach correction was 1/3 of the headwind. If, for any reason you added a few knots on top of the approach correction in -let's say calm winds- then per the IFL Hyrdraulic Failure tables you neeed to increase the distance a bit (plus 180 meters according to my QRH)


Hope that helps!

Ah, Airbus... :rolleyes: