Just to add a bit more detail to the reply made by
dubaigong, for those who are not privy to Kabul ops, some of the problems with it are as follows:
For ops into Kabul there are basically 2 approaches which most operators will use:
- R29 RNAV (GPS). The minimum visibility requirement for this approach is 4.0 Km and it is not a WAT limited approach.
- R29 ILS. The minimum visibility requirement for this approach is 1.6 Km and it is a WAT limited approach.
Nb. A WAT (
Weight / Altitude / Temperature) Limit defines a proscribed climb gradient requirement to ensure that, in the event of a go-around (
for any reason) should the aircraft also then suffer an engine failure, it must still have sufficient climb performance available to ensure that it will miss any hills that form part of the missed-approach path. I would add that this is a Regulated safety requirement, it's not something that we just 'make up', and failure to take account of it would be (
at best) illegal and / or
(at worst) criminally negligent.
For those who've been to Kabul, you'll probably be well aware that the hills that surround the airport are both close-in and quite-high. As such, this requires a quite steep missed approach climb gradient, i.e. to ensure that you don't crash into the hills (
if / when going around, on one engine ).
For the last few weeks the visibility in Kabul has been somewhat limiting… it's that time of year!
On those days when the visibility has been less than 4.0 Km, it means that the only approach that will get you close enough to the runway, for you to be able to see it so that you can land on it, is the R29 ILS (
with it's inherent WAT limit requiring a 4.8% missed approach climb gradient). In order to achieve that (
steep) missed approach climb gradient (
if / when on one engine) necessarily requires that the aircraft is not overly heavy and this, in turn, means that the aircraft's maximum landing mass has to be managed (
by adjustment of passengers, baggage, and fuel)
prior to departure.
As to who makes the decision about the amount of passengers, baggage & cargo, that gets loaded onto the aircraft, that's something that's
not decided upon by the Flight Crew; though it's the Flight Crew who have to deal with any subsequent mess should the trip not go to plan.
And what of the case when the visibility is forecast to be greater 4.0 Km, but when one gets to Kabul one finds that it is less than that?!
In that instance you then can't do the R29 RNAV (GPS) approach (
with it's 4.0 Km minimum visibility requirement and no WAT limit) and instead one would like to use the R29 ILS (
albeit with its associated 4.8% missed approach climb gradient limitation).
However, you might now have the problem that the aircraft has been loaded such that, even if you burn-off any 'extra fuel', i.e. down to the point when you have just enough fuel (
i.e. just enough to allow you to shoot the ILS approach, fly a missed approach, and then divert) you might still be too heavy wrt the R29 ILS WAT limit (
due to the number of passengers and their baggage that was loaded before you took-off, remembering that the aircraft was loaded on the basis of one being able to do the non WAT limited R29 RNAV approach).
Thus you are screwed, and all you can do then is: divert !
It might well be the case that there are some airlines where the pilots would 'press-on' and endeavour to land, regardless of various aircraft performance restrictions & Regulations; but
that's not the flydubai way !!
Now it's a purely personal observation, but it never ceases to amaze me how a new B737-800, with 27K thrust engines, can be so evidently outperformed by some of the other (
did someone say, 'decrepit' ?! ) aircraft types that are often used for ops into / out of Kabul... or perhaps it's that some airlines and / or some pilots simply choose to ignore certain 'commercially inconvenient' safety regulations?!
Of course, maybe those who object to flydubai rigorously enforcing the safety requirements might, in the future, choose to fly with those those other 'more flexible' airlines, as they'd then always be assured of arriving at the same time as their baggage; one way or another?!
Now wrt carrying / tankering fuel into Kabul. Yes, when the passenger load & weather permits it, we do indeed tanker fuel into Kabul (
as do most airlines).
That said, I can personally attest to the fact that the last time I went to Kabul (
a time when I had to use the R29 ILS, and thus was WAT limited), in order to
maximise the passenger & baggage loads, I did not take one single ounce more fuel than the absolute legal-minimum as required from the Flight Plan (
the idea being to land at the maximum possible weight - made up predominantly through passengers and their baggage - albeit a weight consistent with also achieving a 4.8% go-around gradient, assuming one was doing so on one engine), i.e. just enough fuel to to get over to Kabul, do one instrument approach, a missed approach (
if need be?), and still have enough fuel to divert to an alternate airport (
which in fact means arriving at ones alternate airport with only 'Final Reserve' fuel onboard - which, trust me when I say, is bugger all fuel - but is still legal !! )... though that particular time we refuelled after we'd landed in Kabul.
Hopefully this dispels the suggestion (
made in the 1st post, above) that we'd tanker fuel, i.e. at the expense of the paying passengers and / or their baggage?!
As for not landing in Kabul when the runway braking action is reported as 'Medium', I'm not sure what that's about, but maybe there was more to that decision than just that one particular item ?!