The introduction of theinto scheduled service has been rocky. But after months of working intensely with Pratt & Whitney and Airbus and with significant operational restrictions, executives say they expect the worst of the entry-into-service issues to be overcome by June.
The airline stepped in to take the firstin early January after original launch customer refused to take delivery of its aircraft. It turned out that the aircraft’s Pratt & Whitney engines need extra cooling before startup to eliminate the risk of internal damage caused by minuscule shaft bending due to the temperature differential in different parts of the motor. The cooling, to be exercised for one engine after the other, could take several minutes in total, depending on how long the engine had been turned off. Experience shows the cooling takes longest for ground times of about 1 hr.; significantly shorter and longer turnarounds are less of an issue.
During two May 5 scheduled flights operated by Lufthansa’s first A320neo (registered D-AINA), which Aviation Week was invited to join, cooling times differed materially: Before the first leg, flight LH12 from Frankfurt to Hamburg, engine No. 2 took 2 min., 7 sec. to cool and engine No. 1 needed 2 min., 3 sec. The engines had been turned off 55 min. earlier. Before the return flight, LH19 from Hamburg to Frankfurt, the aircraft sat on the ground for about 40 min., and engine cooling took 1 min., 47 sec. and 1 min., 48 sec., respectively.
Normal engine startup is interrupted at 10% N2 and pilots are informed on their central display via a warning that the respective engine is “cooling.” When sensors inside the engine signal that the process has minimized the temperature differences to acceptable levels, the sign comes off and normal startup continues.
The slower than normal procedure continues to be the main issue for the two airlines flying the A320neo today, Lufthansa and IndiGo. Nuisance fault warnings were initially another problem that increased pilot workload. But Lufthansa’s chief pilot for the A320-family fleet, Sascha Unterbarnscheidt, says these faults were almost completely eliminated by two software upgrades from Pratt earlier this year.
As for the startup process, a clear road map has now been identified. Pratt has promised its operators a June software update intended to bring the maximum cooling time down to 90 sec.—and even lower levels if the aircraft is operated in an optimized way. Lufthansa expects the hardware fix, which Pratt has developed and currently incorporates into the latest standard engines, to reduce the delay to a maximum of 30 sec. That would bring the PW1100G in line with the International Aero Engines (IAE)on Lufthansa’s A321ceo fleet. The airline has selected several versions of the CFM 56 engine for the A319 and A320 fleets.
In addition, Lufthansa hopes Pratt and Airbus are developing a procedure it calls “dual cooling,” allowing both engines to be cooled at the same time rather than one after the other.
Lufthansa has taken delivery of two A320neos so far, registered D-AINA and D-AINB. Delivery of the third aircraft, D-AINC, will be delayed until the next major software upgrade has been uploaded by Pratt and Airbus in June. “We considered taking it earlier,” Unterbarnscheidt says. “But we decided that it would not have made much sense to fly it in the current status for a week or two and then install the new software.”
D-AINC will not yet have engines that include the hardware fix. The three first aircraft will receive new engines of the modified standard “as soon as they are available,” according to Unterbarnscheidt. He says fast action from Pratt is expected.
In spite of the persisting limitations, Lufthansa is slowly shifting the A320neo operation into normal mode. Initially, only a core group of 25 crews was allowed to fly the two Neos; early flights were even operated by enlarged crews with a third pilot monitoring from the jump seat. That decision was made not only because of the engine startup issues but also because the airline wanted to familiarize a core group of pilots with the behavior of the aircraft first.
Unterbarnscheidt says flying the A320neo feels somewhat different from the A320ceo. The wings are stiffer to accommodate the heavier engines, and the wingtips have been slightly redesigned, leading to slightly different behavior. These issues aside, the crews are full of praise for the aircraft: First Officer Jan Hoehn points out that unlike other turbofan engines, the geared turbofans react immediately to pilot input. “The engine has the same thrust as the A320ceo motors, but you can tell how much more effective they are. They almost behave like turboprops in their climb performance.” he says. On another May 5 flight from Hamburg to Frankfurt, Unterbarnscheidt and Hoehn were asked by air traffic control to climb from flight level (FL) 280 to FL 340; Hoehn points out that the performance at altitude was impressive.