|Quoting Pmg1704 (Reply 6):|
Can anyone explain what a cycle is? Does 1 cycle = 1 hour the engine is on?
GenxPower has explained a lot so I won't repeat as that answer is accurate enough for this discussion board. Yes test engineering is complicated, but so is being a chef unless you are one.
What I will note is that in older warranties an engine was guaranteed for so many hours. But... the catch is each cycle (idle to full and back) added one hour for purposes of calculating guarantee work and payments. For example, a 8,000 hour warranty might only cover 4,000 cycles and 4,000 hours of cruise. They were written in different ways. Later engine warranties were written more like a car warranty, 8,000 cycles or 12,000 hours (whichever comes first).
Note: I'm speaking in general. Many MX
plans are custom to the airline and believe me, engine makers *want* to sell power by the hour. (Highest premium, but very little risk to the engine buyer.)
Back on topic, This is a big accomplishment for the GenX, but much work lies ahead on the test stand. Stators algorithms must be optimized, fuel maps cleaned up, verifications of boroscope inspection plans etc. And there will be a mistake found. For instance, its quite common to beef up the bearings after an engine makes the test stant. OR
... perhaps TSFC was missed and a new fan will be added (rumors are the GenX is doing well). But if a new fan makes it more competitive versus the Trent, they'll change it. Its cheapest to change a fan before the bird strike, water ingestion, and blade out testing.
Maybe they'll change the fuel injectors (GE's traditional Gremlin is fuel injector durability on new designs. Its usually fixed before entry into the fleet. The big exception was early GE
-90's. IIRC the fourth fix finally gave that engine durable fuel injectors.). Before the Trent 800, RR
had trouble with combustor durability. Pratt traditionally misses fuel burn. (And the 4084's damn guide swirlers, a cheap part buried in the engine that "guides" the fuel injector home... Grrr.... A cheap part forcing engine pulls due to poor durability. Grrr...Any fix that impacts emissions is an expensive fix too... Unlike a fuel injector, these aren't line replaceable.)
I'll be interested to follow this engine through testing. I'm just sad there is no Pratt on the 787.
Cest la vie. (I've gone into more Pratt, GE
, and RR
issues before, feel free to search for them.)