A320 NEO - PW1100G versus LEAP-1A

"Laaayyydies and Gentlemen."

"In the blue corner providing a maximum (projected) thrust of 33000 Lbs , the cruiser from Connecticut, Pratt and Whitney's PW1100G!!!! "

"In the red corner providing a maximum (projected) thrust of 35000Lbs the French/American CFM International, the Leading-Edge-Aviation-Propulsion - LEAP-1A!!!!"

Note: Being written from a maintenance engineering perspective, this article is objective and subjective. You'll have to be content with my impressions, having been on the Part-147 courses and seen both engines up close. I'll leave you with tonight's commentators Bob Bypass and Mike Duct.

"Welcome, I'm Mike Duct and hello to all the folk at home. We've been waiting a long time for this match. Billed as the battle of the next gen engines! There's been some disappointment with the NEO as it is a re-engined Enhanced airframe rather than a Enhanced-Enhanced! Both engines come from heavyweight families and there are some big similarities with the CFM56 and V2500. Over to you Bob."

"Thanks Mike, I'm Bob Bypass. I see a lot of nervous CEOs in the crowd, having signed 20-year support contracts, they wanna know they've backed the right pony!"

"They're not ponies Bob."

Round One: Size

• PW1100G fan diameter: 2.06 metres
• LEAP-1A fan diameter: 1.98 metres

The PW has the reach, but at this stage, too close to call.

Ding, ding and after a very respectable first round, it is a victory to PW (on points).

"The size of these fans under the A320 wing are huge, but between them, little difference."

Round Two: Bypass

Efficiency: Both engines go for high bypass, with a massive increases in the bypass ratio.

• PW1100G: 12 to 1
• LEAP-1A: 11:1

Again, a very close round but as the LEAP-1A goes back to the corner, the PW marketing team deliver a low blow! The PW1100G is marketed as 'Ultra' high bypass while the LEAP is 'only' high bypass - below the belt! And the referee has to step in!

"There is chaos with both marketing departments getting involved!"

"Whoa Mike, there are airlines trying to smooth things out!"

With the judges' decision final, it is a draw.

Round Three: New Technologies

PW1100G: Fan Drive Gear System (FDGS) - PW goes for an immediate knockout punch, the FDGS reduces the fan speed compared to the N1 shaft speed by 3:1, effectively meaning that the lower speed fan and higher speed N1 are closer to their most efficient operating speeds. A separately controlled stage of VIGVs for the LPC add to the efficiency and suddenly the LEAP is reeling. PW are pushing.

FDGS

The LEAP-1A tries to block with the Modulated Turbine Cooling (MTC) which regulates stage 10 HPC Compressor Discharge Pressure (CDP) air flow to the stage 1 High Pressure Turbine (HPT) blade roots and blade internal cooling passages thus optimising fuel burn. And then counters with the Start Bleed/Booster Anti Ice (SB/BAI), a three way valve which aids start performance and gives controlled de-icing to the booster flow splitter.

PW holds and the LEAP hits again with the Transient Bleed Valve (TBV) which dumps air into the exhaust, improving stall margin and improving performance in transient conditions. PW defends with HPC passive and active bleed valves.

There's a hush from the crowd as the judges acknowledge the PW due to the innovative FDGS, but with the LEAP also boasting some new tech, it is another draw.

"Good call from the judges, looking at the central sun gear and five planetary gears of the PW, complexity is the word!"

"I hear you Mike, I'd hate to be the guy who's borescoping that in the field!"

Round Four: One More

"This is one amazing contest Bob.....both heavyweight manufacturers knowing what needs to be done, but having different approaches!"

The guns blazing approach slows, and both competitors test each other.

ATA 74 Ignition: The PW1100G cuts out one of the two ignition exciters, having a single dual channel box feed the two ignitor plugs, but the LEAP-1A sticks with the convention two, in an air cooled enclosure in the core.

ATA 73 Fuel: PW offers 18 fuel nozzles, but LEAP-1A jabs with 19 nozzles and three different fuel manifolds- POW!

ATA 73A Control: PW has a conventional dual channel EEC, POW-POW, LEAP hits back by having two independent EECs on the fan case (still operating as channel A and B). But the PW's EEC can work on an active/active mode for certain failures.

"The NAA licensing department representative in the crowd shakes his head, realising that a number of FADEC/EEC module 15 questions need to be re-written."

PW1100G - EEC

LEAP-1A - EEC A & EEC B

ATA 75 Air System: The PW blocks with four stages of HPC variable vane control, but the LEAP is too strong and swings in with five stages.

The crowd smell blood.

The bell goes and the LEAP team take the round, leaving PW to look at their lead being cut down to size.

"These boys are in for the long haul!"

"Is that an aviation pun Mike?"

Round Five: Maintenance Layout

As the fight continues, both contestants look to their respective corners for help from their maintenance teams, the B1s (physical) and B2s (moral). In the PW corner, there are some raised eyebrows.

The PW keeps the fan case clean with the only major accessible components being the EEC and oil tank and opts for the stateside everything-we-can-in-the-core, so it is fan cowls and ducts to open.

LEAP-1A - AGB (Fan case)

PW1100G - AGB (Core)

The LEAP has the accessory gearbox on the fan case at 8 o'clock (to allow for the required ground clearance of the larger fan). The engineers cheer, as so much is easily accessible. This does mean the LEAP's EECs and oil tank share the right side of the fan case, confusing many in the crowd familiar with the dry-side, wet-side engine layout.

LEAP-1A gets the thumbs up ahead of the PW1100G and wins the round.

"The engineering contingent nod in agreement for the LEAP, but claimed burn figures mean the CEOs are looking at the PW1100G."

"I've gotta say Bob, that in this aviation crazy world, that's probably the worse decision since the Concorde was retired!"

 Final Round Six: Heat Management

The core layout and the higher speeds shafts of the PW means some serious heat is being produced. Which means some heat exchangers are necessary. The LEAP has some heat issues of its own to deal with.

The LEAP-1A powers forward pre-emptively.

• A main oil - fuel heat exchanger,
• Dual Surface Air Cooling Oil Cooler (SACOC) mounted in the cold stream,
• IDG oil - oil heat exchanger
• Servo fuel heat exchanger

LEAP-1A Surface Air Cooling Oil Cooler (SACOC)

 The PW1100G team laugh and counter back:

• Air-Oil heat exchanger - BANG!
• Fuel - Oil heat exchange - WHACK!
• IDG Oil - Oil (engine) heat exchanger - BIFF!
• IDG Oil - Fuel heat exchanger- KAPOW!

All with a complex Heat Management System (HMS) effectively meaning that the 1100G can swap heat between systems as necessary.

PW1100G - CoreHeatExchangers

 "Mike. The PW can literally transfer heat around between oil, fuel and IDG oil!"

"OMG Bob! It's almost as though both manufacturers have sent simplicity on holiday. The judges give the round to the PW1100G!"

"With the final round, we tally the points......A DRAW!!!!

"What an amazing legal coincidence Mike! The fight being a draw!"

In summary:

Both engines offer enough new tech to keep engineering savvy professionals awake during the courses but there is enough conventional technology to keep the known-to-the-unknown manageable.

Additionally, both engines introduce fan cowl proximity switches for flight deck monitoring and visual indications for open cowls and the addition of a tertiary lock on the TRs thus raising the safety bar.

I've deliberately steered away from any 'gossip' or 'rumours' regarding performance. I have yet to know a new aircraft or engine not to have issues once in service.

Only time will tell which will be the most successful but be sure that both engines will be evolving throughout their lives as manufacturers fight to win the re-match!