Fiji airways to begin Nadi-Adelaide 30/6/17

[Richard H.]

Interesting, I must admit when I first saw the announcement I thought that their solitary 700 series 737 would be a better fit for this run. A little more range to play with as a reserve and, well, I have my doubts about them reliably filling an 800 past the capacity of a 700 even at only twice weekly. (Although they will likely do better in winter...) Time will tell.

[Yusef D]

I can assure you that in the real world, a well attended 737-800 does not have 3000nm range. Most international flights require an alternate, and Nausori is usually unsuitable, leaving Apia, La Tontouta and Port Vila. (exemptions exist for airports with non-intersecting runways like SYD)

A real 737 , with liferafts, catering, rear hold cargo system etc tops out not far beyond the 2400nm that SYD/BNE/MEL to DPS requires. Virgin's PER-HKT was close to limit but doable. Plenty of good alternates around and before HKT.

[MarkR]

Yusef, I can assure in a real world it does, and so can Boeing, as per the books at MTOW with 160 pax and luggage (34000lb payload) no cargo range is 3200nm with a 200nm alternate. Given the route being discussed is 200nm shorter than SYD-DPS and would have some headwind only on the westbound leg where there is a plethora of alternates to ADL, no real issues at all by comparison.

[John C]

Mark

Do you speak from experience or merely looking at the books?

The payload/range tables usually are fairly light on for arrival fuel and I don't know anyone that would arrive with bare bones fuel.

Adelaide only really has Melbourne as a destination alternate, Edinburgh really doesn't help you much and taking a foreign registered aeroplane into that port would be a time consuming exercise.

It has been a while since I flew a 737-800 but it never did as well as book and I never took min fuel. I don't doubt there will be some days where departing with a full load won't be an issue but there will be days when it is.

That said I doubt they will fill it up so the point may well be moot.

The other thing worth looking at is the weight that comes with a full load. You have picked 15.5 tonnes for 160 pax. I generally use 100 kg per punter and then for predominantly holiday traffic that tends to be a bit on the light side - ok for business routes. I don't see many 77kg adults on board these days..

[Ryan Hothersall]

Many people from that part of the world aren't small either.

[Justin L]

Originally Posted by John C

Adelaide only really has Melbourne as a destination alternate

If strong headwinds are a cause for a diversion due to weight restrictions and fuel capacity, wouldn't this be known before take off or early enough mid flight to plan for additional alternates such as say Canberra, Sydney, or even Newcastle?

[Rowan McKeever]

Yes, but they'll still be required to plan for enough fuel for x (2, 3? I forget which) missed approaches at ADL, 30+ mins of holding fuel and then fuel to actually fly to an alternate from overhead the destination airport. That covers things like another aircraft being disabled on the runway, etc. The enroute alternates are factored in to the route planning but they still have to plan for last minute events at the destination.

[John C]

Yes, usually.

Strong headwinds are not usually the problem per se.

The strong headwinds mean extra fuel is required to make the trip, it isn't unusual to see 80-100 kts on the nose, particularly when you are heading southwest, but when weather at the destination requires an alternate or holding fuel, that's when you start having to get the abacus out and crunch some numbers.

It is pointless, in my opinion, to hold fuel for an alternate without giving yourself the fuel to fly a couple of approaches at the destination, the point of the exercise after all is to land at the destination.

If you carry destination fuel (one approach and missed approach) then off to the alternate, then you are in my opinion, setting yourself up for a divert.

The strong enroute wind case is less of an issue but if it is unexpected you can always drop into an enroute alternate on the way to gas and go. That usually never happens.

If you are tank capacity limited. I.e. The flight is so long that it requires full tanks to reach the destination then your options are much more limited. You can stop enroute for fuel, but you then have to ensure you are not landing weight limited at the enroute fuel stop port, or you can reduce weight (which reduces fuel burn).

If destination weather means an extra 30-60 minutes of fuel, and you were already MTOW constrained (I.e. You were taking off at the max takeoff weight for the runway and conditions) then you can't leave fuel behind, so the only option is offload pax and bags.

Fuel planning is a little different for international operations versus Australian domestic ops. Domestically we don't carry an alternate unless it is required by the TAF. Internationally most carriers (I say most because I don't know about all jurisdictions) carry an alternate. When the weather is good they may well carry a "technical" alternate. For example a Brisbane arrival might carry Cooly, a Sydney arrival might carry Canberra, but if the weather is crappy and the weather system impacts all the airports in the area, then you may need to carry an alternate much further away, which means more fuel.

Also the planning books usually stipulate landing with 30 minutes fixed reserve and that's pretty much it.

As long as my **** pointed towards the ground I wouldn't plan to land with 30 minutes, so I always carry more. Our company planning policy is to arrive with 60 minutes, and that is reflected on the flight plan, so it is usually not an issue, though in some cases I decide to take more, but do so having considered all the relevant factors - I don't carry more for "mum and the kids".

The planning books are really only a document to use as a datum when comparing things, not as a real world document.

The other thing that the planning books don't consider is PDA's which is the percentage that the particular airframe performs under/over book. Some new airframes can perform a couple of percent better than book and older more battered airframes can perform up to 10% worse than book. This is often (but not always) accounted for in the flight plan with a PDA which tweaks the burn to suit the particular airframe. It requires a significant effort on the part of performance engineering to properly determine the pda for each airframe and isn't super accurate.

[Justin L]

Thanks for the detailed information in the above two posts. Very interesting and makes a lot of sense.

I guess if you need to plan for an alternate once overhead ADL and can't land, then MEL does become the only logical choice.

[Radi K]

There will be days where due to strong headwinds and bad weather in Adelaide that a techstop or heavily reduced payload will be required. That being said, those day's aren't overly common. The problem with the schedule is that due to curfew, tech-stop options will be limited if they want to make it in/out on time. Still there is plenty of good options, BNE & SYD in the first instance (company ports).

That assumes on that given day up to three things happen
1. High Payload (probably capped by commercial anyway)
2. Strong headwinds
3. Bad weather in Adelaide requiring a Melbourne (or other) alternate.

Statistically that is a low occurrence and it's a risk any airline takes. It's not unusual for the tiger 737s to stop in DRW for gas on the way to DPS during school holidays.

Naturally there are Point of No Return options, no alternate options and also re-clearance in-flight options available to the crew and the dispatchers.

I will make the point; Fiji Airways already operates some of their 738s on very long routes thus have extensive pacific experience (HNL, MEL etc). The runways at ADL and NAN are long and don't have an performance limitations on them. Also- Fiji airways operates user preferred routes across the pacific so that will have it's advantages over fixed routes in avoiding headwinds and maximizing tailwinds.

Going back to Nadi won't see many issues. Suva is used as a primary airport for the 737 by Fiji Airways and their crew go into there without issue. It will have a tailwind and I doubt will ever be payload limited unless you get very bad weather in Fiji.

The other major 737 operator flying into NAN's major issue was on a sunday when Tonga was closed and you couldn't use it as an alternate. This reduced payload.

I agree the 700 is a better option for going TO ADL but you can fill an -800 coming home. Go on them for giving it a go... hopefully it works out.