GE and the Geared Turbofan

There was quite a lot of hype in the last days around a story, first reported by Bloomberg, saying that GE talked with Airbus about a new engine for “a narrow-body jetliner in development”. In the article (and many that followed that first story) there is a lot of speculation about the aircraft: If it would be a successor of today's A320, a future stretched variant of the A220 or if that aircraft would in the end be the ZERO E (E for Emissions) aircraft announced by Airbus in September and the engine GE and Airbus discuss here would be an engine that would be used for that aircraft until a ZERO E engine (technology) would be available.

To make it short: this last consideration is – sorry to say it that way – bullshit! Whatever the source of energy of the future ZERO E aircraft would be – hydrogen or electricity comes to mind- the aircraft has to look very different from the design of a jet fuel powered aircraft and it would make no sense at all to hang a Geared Turbofan on an aircraft designed and optimized for zero emissions.

The fact that GE and Airbus talk about a new narrowbody is not a big story in the first place, as there are always discussions between airframers and engine companies about all kinds of possible future projects. But Bloomberg made a lot of noise due to the fact, that the design proposed by GE would be a geared turbofan, which is the engine design that today only Pratt & Whitney uses. GE always more or less dismissed the geared design in public because of the added complexity of the gear. Rolls Royce began developing their own geared engine concept called Ultrafan a few years ago.

So does GE not believe in the conventional turbofan anymore?

Not necessarily: believe it or not, but it is not the first time that GE proposes a geared design to an aircraft manufacturer. For the B777X, today's B777-9, GE also pitched a geared design towards Boeing, as did P&W at that time (I believe RR proposed a 3 spool design). But obviously Boeing went down the low-risk path of the GE9X engine, an evolution of the GE90-115B and the GENx engines, although the geared engines would have had a better fuel burn.

For the now (forever?) dormant NMA, Boeings reference engine was a geared turbofan. This makes sense, as at least in the beginning two of the three possible engine provider offered a geared design (P&W and RR), so we can only guess that GE (or CFM) also offered both variants (geared and non-geared) to Boeing. Later RR went out of the discussions as the aimed EIS timing was too early for the UltraFan.

So when today GE talks with Airbus about a geared engine, there is nothing sensational in there. Most likely the geared engine is just one out of two or more designs. And it most likely not more than a paper study, in which P&W and RR are involved as well. It is not more than the usual business of the future concept groups of all parties involved.

So do not expect an announcement of a new aircraft in the near future. Even a stretched A220 (-500) seems not to be on the horizon too soon...

The future is geared!(?)

The future in commercial aviation is geared, it seems:
Of course P&W and it's partners in the PWW1000G engine thought so when they started to develop their engines for the Mitsubishi MRJ, the Bombardier CSeries, the A320neo and the Irkut MS-21 and the Embraer E2-Jets.
But then, about three years ago, RR started developing their own engine with a geared architecture, calling their product (to be) the "Ultra Fan".
No I read in an article from Aviation Week that also Safran is working on a geared fan engine, under the umbrella of the european Clean Sky initiative, the equivalent  to NASA's CLEEN program.
A cross section of the engine concept can be seen on page 17 of this presentation.
My guess is, all engine concepts that CFM, RR and  P&W will eventually offer Boeing and Airbus for a replacement of today's A320 and B737 will have a gear between the LPT and the Fan!

A320neo start-up times

The hype was huge when the problem around longer start-up times of the PW1100G-JM went public. Indigo stated that the ~2min. extra time that it took to start up the engines would threaten their Business model as a low cost carrier with high utilization and short turn around times between flights. As I showed in an earlier post this was not very plausible from the beginning. But at airports with tight infrastructure (Frankfurt comes to my mind) it could cause some headache - more for the airport than for the individual airline though - as, if one aircraft blocks the way to the gates as it has to wait until the engines are started, other aircraft have to wait.
Believing what Airbus, P&W and Lufthansa said recently the problem is largely gone now.
Now we can read in a report from airwaysmag about the first revenue flight onboard on the first Frontier A320neo that the that the competing LEAP-1A engine has a "noticeably long startup time". What that exactly means we don't know yet. There was nothing official about that yet, showing once again that the PR Folks at GE, CFM and Safran are doing a much better job than those at P&W.
But maybe someone should tell Qatar Airways CEO Al Akbar about it as the LEAP-1B should "suffer" the same problem before he confirms his order for the B737MAX. Or maybe he already counts on compensations...?

Indigo business model threatened by PW1100G?

Yesterday I read that Indigo sees their business model threatened by the engines of their A320neo – because of  the longer start-up times of the PW1100G (dependent on how long the engine was out after shutdown) the aircraft has to wait up to 2 min. longer with their engines at idle before the aircraft can begin to roll and taxi for takeoff.

Now let’s have a look if there is anything in this claim by looking at how Indigo actually operates their aircraft:

According to flightradar24 the 3^rd A320neo (VT-ITA) flew on May 2^nd from Delhi to Nagpur. The aircraft landed perfectly on time at 3:40am (UTC). It took off again 52 minutes later, 7 minutes later than scheduled but early enough to arrive back in Delhi 4 min. ahead of the scheduled arrival at 5:56am.

The 2^nd leg of the day went to Bangalore with a scheduled departure at 7:30am (actual departure time 7:55am). The aircraft arrived Bangalore 3 min. ahead of schedule at 10:17am. Scheduled departure back to Delhi was at 11:15am, which was missed by 9 min. Arrival in Delhi then was 5 min. ahead of schedule at 13:50am.

So we can see no delays stemming from the start-up times. The 2 min. longer start-up time is an the maximum, which only occurs when the engine was off for about 2.5 hours. But turn-around times for the two legs was below one hour, so the extra start-up time should be

Why I don't believe In MoM...

In the last couple of weeks a new discussion about the so-called „Middle of the Market“ or “MoM” aircraft broke out. Apart from that nobody really knows what this aircraft should look like (B757 successor or B767 successor or both, narrowbody or widebody, scalable to cover the B737 market or not?) or every potential customer wanting something different, I do not really believe in the launch of such an aircraft in the near future.

Why?

Airbus has no interest in such an aircraft. They have a good market position with their A321neo, especially the LR version and the future A330-800, although I don’t foresee large order volumes for that aircraft. For sure Airbus is studying the MoM, but (for now) for the pure purpose of looking into what Boeing could do and if and how Airbus would have to react to it.

Boeing would be the one to launch such an aircraft. But do they have to do it? Although the B737MAX has less orders than the A320neo, the amount of orders the B737MAX got is massive. The B737MAX8 is right in the sweet spot of the market and has a small advantage in costs per seat against the A320neo – if the LEAP-1B engine performs as advertised, what remains to be seen.

The B737MAX8 just had it’s first flight. the –MAX9 and the –MAX7 have to follow. So why unsettle your (potential) customers talking too much and eventually launching a new aircraft that would at least partly overlap with the B737MAX family?

Also, Boeing will probably feel a drop in cash flow during the transition of the B777 Classic to the B777X between 2020 and 2022, just when the MoM would need large sums of money for R&D spending.

But there is another aspect why I do not believe in a launch of MoM for a, say, 2024 entry

Three in a row, two in a week..

There is some movement in the A320neo engine market right now, it seems. P&W scored three "wins" in a row recently. After BOCA announced an order for 15 A320neo to be powered with the PW1100G-JM, this week both Tigerair and ANA selected the Geared Turbo Fan for 37 and 30 aircraft.
I would expect that we will see more decisions about A320neo engine options being taken this year as EIS is now less than 20 months away. The PW1100G-JM should gain certification this summer so that it will maybe have an advantage in customer confidence (and this is badly needed by P&W after the PW6000 disaster).
Right now the GTF has a slightly larger market share with 896 aircraft (866 shown here by pdxlight plus 30 by ANA) to be powered versus 827 to be powered by the LEAP-1A. But there are large campaigns waiting for a winner, like Lion Air (174 aircraft), American Airlines (130 aircraft) and easyjet (100 aircraft), so the picture can turn by any of these campaigns decided.

Rolls Royce looking ahead...

Yesterday Rolls Royce surprised the aero engine world at a briefing about it's strategic roadmap by looking ten and more years ahead and revealing, what the company plans as their next steps in engine development.

In the 2020 timeframe we could see a further evolution of the Trent 3-spool engine family for now called "Advance" (I am sure the name will change once it should evolve from being a technology project and becomes a real program). This engine should deliver an SFC that is 5% better than the Trent XWB. As aspire aviation pointed out, the GE9X for the B777X should be about 5% better than the Trent XWB, so it is clear who is the "enemy" here.
The time frame and the SFC goal puts this engine concept  in the position to be a good candidate to power the A380neo, if the project goes ahead. But Airbus could also ask for a version with more thrust than the roughly 70klbf needed for a re-engined A380 to power a A350-1100 and then have a formidable competitor to the Boeing B777-9.
A first test engine based on the Trent XWB, but with a new core with a higher OPR - up to 60 and thus being on the same level as the GE9X - should run as early as next year.

The second engine does not necessarily build on the Trent 3-spool architecture as it - potentially - could use a gear as we currently have on the PW1000G family from Pratt&Whitney. Of course also a 3-spool GTF is possible, but I doubt that makes real sense, so I would guess it would have 2 spools. This engine should then be another 5% better than the "Advance" engine.
This engine concept should not only target the widebody market but also future narrowbodies. In the light of recent discussions about a possible B757 replacement and a successor to the B737MAX family with an EIS around 2025 this is an interesting move of course. After selling their stake in the IAE to P&W, both companies announced  a partnership for future narrowbody programs. This partnership was later canceled. But for any future narrowbody we should expect a choice of two engines, not three. And CFM seems to be the frontrunner in any case (unless the LEAP engines will fail completely, what I doubt), so either RR or P&W would be out of the game. So is this move aimed at P&W begging for a new try of the partnership? Who knows...
Anyway, the above SFC comparisons are true for widebody engines in the GE9X class - for narrowbody engines we have to scale the SFC values, as for example the tip clearances are not scaling with the physical smaller components of the engines. Relative clearances are larger and so are aerodynamic and parasitic losses. Therefore all engine components have lower efficiency levels. And as the core components (high pressure compressor and turbine) get smaller and smaller with increasing bypass ratio (BPR) and overall pressure ratio (OPR) for a given thrust, it gets harder and harder to maintain a decent efficiency level. Also surge capability of the compressor might not be easy to control. In the end, to achieve an OPR of 70(!) for this engine I predict this will only be achievable with a radial compressor stage at the back and of the compressor. And at temperatures that will be reached at such a high OPR this wheel has  to be out of a material that can only be found in turbines today. Maybe CMC? Then good luck producing such a complex piece out of that material? The other possibility would be to have an intercooler between the low and high pressure compressors. But that would add weight and complexity, counterproductive for a narrowbody engine. This is why I see that concept better suited for a long range application, where (engine) weight does not have such an immediate effect on fuel burn, The same argument could be, but must not be necessarily true for the envisioned variable pitch fan system. This idea goes back to the ADP concept from P&W from the 1980's. The variable pitch system has two great advantages versus non-pitch fans: there is no need for a thrust reverser (which save weight) and the whole nacelle can be shortened, also saving weight. On the other hand, the pitch system itself is complex and needs additional maintenance. As these maintenance cost are mainly cycle driven, I also see this technology better suited for long-range, low cycle operations.
But who knows what "white rabbits" Rolls Royce will pull out of their hat by then - it is a great company and I would not be surprised if they find ways to handle all these challenges.