Qantas 767s

[NickN]

Can someone with the technical knowledge explain what the benefits of the different types of engines are?

[Brenden S]

The GE CF6 is a twin spool engine.
The RR RB211-524H/G/T is a 3 spool engine. Its also heavier than the GE, it is also more robust and can take a little bit more of a hammering than the GE. You will also note that there are a lot of PW aircraft parked up in the states with the GE's still flying.

BA wanted QF to take more 767's and the ZX 767's are primarily used on the milk run as they get a better economy out of the aircraft than if they were to use the aircraft east west, which happens about 1 flight daily.

[Nick Te Mata]

In addition to what Brendan covered, there are some differences in broad capability between the two powerplants.

The Qantas decision to use GE's on the 767 was somewhat landmark and a cut with the management tendancy of the time -- the 238ERs had PWs, as did the earlier build 742s, while the subsequent 747 fleet (composed of 742, 743 and 74L aircraft) were all RB211-524D4 fitted.
The selection of GE for the 763s as a third major powerplant family was due to its particular suitability to the missions QF intended for the 763s, and the ability for the CF6 to make the commonality argument redunant was pretty significant. This was made even more notable as the 744s entering service just after the first 763 were fitted with the new RB211-524G engine, a very similar choice to the H2 and H4 engines offered for the 767.

The CF6, ultimately, is the most economic of the engines offered for the 767. It's fuel consumption is the lowest in its class, however this benefit is really only found on longer sectors. QF at the time was 8 years from being a domestic operator -- 763s were used almost exclusively on sectors of over 7 hours (SIN to everywhere in Australia, to HKG, NRT and KIX, MNL etc..).

The more robust RB211 is better suited to high sector flying, which is why the ZX fleet was considered a subfleet both in terms of maintenance and operations. They have been dedicated to domestic work since their arrival in 2000 even though the 767 dominated medium haul international work well into the 21st century. The RB211, however also has good (very) mature fuel burn; perfect for the 744 on ultra-long haul sectors that typify Qantas' work with that airframe but perhaps less so for the 767. Most operators used it on sectors about 5-6 hours, which perhaps gives some insight as to why the RB211 was sold in comparatively very small numbers. BA's dominating logic was reducing maintenance costs; I also believe the BA fleet is fitted with -524H2s, making them fully interchangeable with the 744 engines.

[NickN]

Nick and Brenden that was some great info something I will always remember and questions I have pondered myself for a long time. Thank you.

One thing I do want to know is..... what does it mean when you say:

The RB211, however also has good (very) mature fuel burn

..... and how is that type of fuel burn beneficial over the GE engines for ultra long haul.

I have noticed the Johannesburg QF63/64 and Buenos Aires are operated by RR powered 744's.

[Martin Buzzell]

Originally Posted by NickN

Martin, is that why the RR powered a/c hit the deck like a rock?

On that note what is the difference (apart from being single shafted) and benefit of a single shaft RB211 vs the twin shaft CF6?

As Nick says, the RB211 is three shafted and the CF6 has two. You might be correct about the RR (Zulu Xrays) landing a bit hard. They still catch a few off guard.

[Jack B]

Originally Posted by NickN

I have noticed the Johannesburg QF63/64 and Buenos Aires are operated by RR powered 744's.

Buenos Aires is ER (GE) only

Jo'burg is a bit of both

[Nick Te Mata]

I'm not sure if the whole 744 fleet has had the upgrades, but some of the Pacific 744s were upgraded from RB211-524Gs to -524GTs, indicating the installation of new Trent technology that lowers overall fuel burn, thus increasing MTOW/range. The later-build 744s delivered to QF definately had it (OJS, OJT and OJU) which were sent predominantly on Pacific runs in their early life-- some others may have been upgraded as well. This went some way to redressing payload restrictions (on 747s of both engine types) which were a thorn in the side of QF's Pacific services for some time until the ER came onto the market (QF 93/94 in particular).

Despite having good mature fuel burn, the RB211 is still less fuel efficient overall -- it's just that toward the end of very long sectors does the RB211 start to burn less fuel than its counterparts would on a comparable flight. 22-24 missions and the robust nature of the engine see it better suited to more fragmented time in flight and the greater number of cycles typical of European ops.

It is for this reason that when QF had the opportunity to take on some GE powered jets in the late 90s -- VH-OEB, C and D -- that they were classified as 'Pacific' 747s rather than part of the Kangaroo fleet, which involved a lot of rotations between Australia and Asia as precursors to the longer Asia-Europe sectors, where the RB211 is ideal. The GE lower overall fuel burn is better suited to longer non-stop sectors, SYD-LAX/SFO for example. JNB is also subject to some very strong prevailing winds at certain times of year; most of the time it is much of a muchness in terms of which engine is sent. The prevailing factor seems to be the premium seat market. I believe EZE is really only achievable non-stop with ERs under normal circumstances but happy to be corrected.

The arrival of the ER into the fleet (and subsequently the A380) has changed this somewhat; RRs rarely crossed the Pacific besides the 2-class aircraft on QF25/26 and what few services weren't covered by ERs were done so by the 'Ugly Sisters ' in OEB etc. Only recently has the 744 fleet been deployed almost haphazardly as 3 class services have been truncated, more QF11 and QF93 services are turned over to the 388 etc.

[Nick Te Mata]

Sorry also had to mention that the ability to carry out light/unscheduled maintenance at LHR is a factor in the choice of the RB211 for the 'Kangaroo' fleet.

[Jason H]

RRs rarely crossed the Pacific

So, currently the 744RR's are replacing some 744ER's and ugly sisters services on QF107 and QF11 mainly because of poor business travel (52J as opposed to 66J on the ER's). The need to fill the aircraft is obviously out weighing the extra fuel burn costs. What about when fuel prices peak in the near future??

[Nick Te Mata]

Actually Jason, QF's 4-class Pacific services are still the domain of the GE CF6 fleet. For example, QF11/12 has seen a RR powered aircraft roughly once a week for the past few months, whilst QF107/108 and QF 73/74 are only operated by RR aircraft on a rare, sporadic basis, QF93/94 even less. I'm sure this would be a different situation if the A380 wasn't in the midst, but its arrival has certainly kept these Pacific services relatively untouched by the Kangaroo fleet. Had the A380 not arrived when it did, we'd probably see the 4-class RR aircraft on these services more frequently. The entry of OQD into service will again the dilute the mix.
Where the biggest change has come is in the use of these 4-class RR aircraft on what were previously 2-class services. QF25/26 to and from AKL and QF15/16 from BNE certaintly now see a wide range of RR powered jets, not the 56J/356Y examples as previous. The non-stop SYD services still see a lot of the ERs as well as OEB-OED.