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Comment by JCM9 | Hacker News Reader

Technically they’re grounding the Pratt & Whitney engine model that happens to be attached to their aircraft.

When one buys a big jet you pick out what engine you want to buy and slap onto it. It’s a particular engine they’re concerned about, not the 777 airframe itself.

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That's a good point.

As far as I know, newer B77* generally use GE or RR engines. The PW ones are old at this point, and also represent the smallest and decreasing share, so most planes of this type aren't affected. United (or one of its predecessors) was an early customer, and I think PW was the only engine option at launch.

(Not my area of expertise, so I'd appreciate a correction if I got something wrong.)

Pretty much correct. The Pratt engine was in service six or so months before the GE engine (and a year or so before the RR), and United was the 777 launch customer.

The only thing is that the newest 777 variants (777-200LR and -300ER) only offer GE as an engine option, there isn't even a RR choice.

The P&W-powered 777 is just one variant.

British Airways for example went with GE90s, and some airlines like El Al went with Rolls Royce Trent 800s.

Are there any Airbus (or other comapanies’) planes that have the affected engine? Or just Boeing?

Airbus A300-600/A310

Airbus A330

Boeing 747-400

Boeing 767/KC-46

Boeing 777

McDonnell Douglas MD-11

...however the exact type of engine Boeing is using for the 777 (PW4000-112 - https://en.wikipedia.org/wiki/Pratt_%26_Whitney_PW4000#PW400...) is not used by any other airliner. I'm no expert, but as the most powerful -112 version has almost twice the thrust of the -94 version, I wouldn't automatically conclude that problems with one type mean that there are also problems with the other types. OTOH, if they take a closer look at the 777 engines and find a lot with problems that went undetected until now, I assume the other PW4000 engines will get a closer inspection as well...

Its noted that a 747 had a very similar issue the same day as this 777 with the same series of engine.

Since the issue is most likely with fracture detection during maintenance inspection and P&W introduced new procedures for that a few years back, its likely the issue is with the tech being used or the procedures. Which would mean any P&W engines using the same technologies and procedures to detect fan and turbine blade cracks would be affected.

The core is the same. The different model numbers typically represent other configurations of the stages or pump throughput, type of FADEC, and all of these things.

That seems like a complicated way to sell airplanes - why is that ???.

It is like me buying a car from Ford and saying I don't want the Ecoboost turbo 4 but rather that V8 from the Raptor.

Most car models come with various engine options, sure you can't get a V8 in your focus but you can choose between various displacement Gas/Diesel/Hybrid options. In fact the current model year ford focus ships with 14 engine variations.

It’s a standard thing in aviation. The companies that make “airplanes” are usually not the ones that make airplane engines that go on those planes. For big airliners the engine makers are GE, Rolls Royce and Pratt and Whitney. Same concept applies to small general aviation aircraft where the two big engine makers are Lycoming and Continental Aerospace.

The engines are still type rated for the specific aircraft. Some aircraft might only have one engine type rated so there isn’t much choice. Others might have multiple engines to choose from, from multiple manufacturers. That’s the case with many commercial airliners.

https://aviation.stackexchange.com/questions/38156/why-bothe... might be helpful

One of the answers [0] on that page even discusses the next step in decoupling airframes from engines - sorry, I meant decoupling their supply: Power Generation as a Service complete with on-demand billing and feature locking. It's not well sourced, nor highly upvoted, but fascinating if true.

> These days, the engines are often leased, not bought, as part of a "power generation package"...The only physical difference between two "different versions" of a particular engine type, with different advertised power ratings, may [be] the electronic engine control system. In that situation, the airline might negotiate a "total power generation" deal where they only pay for the "higher rated" engine when they actually use it.

[0] https://aviation.stackexchange.com/a/38196

Used to work for a bank many moons ago and we bought a new mainframe (Unisys) and few months down the line we had major month end batch processing issues.

So they payed Unisys a not so small chunk of money to "unlock" the second CPU board which was always present inside the mainframe that was installed.

As a PC guy I was gobsmacked.

It’s actually antitrust at work - United Aircraft and Transport Corporation was split in 1934 into Boeing for airframes, United for airline, and holding called United Aircraft Corporation that owned Pratt & Whitney for engines.

There are a number of reasons - but one is that some AIRLINES will prefer to stay with an engine manufacturer across all their planes if at all possible, as it reduces maintenance training and headaches.

Many boats are the same way. You buy a hull and then mount whichever outboard motor you want.

This might be due to a car being a more common retail purchase compared to a plane. Airlines might want to customize their plane for the usage and different engines might provide different benefits.

I’m guessing it has most to do maintenance training and supply chains.

If x carrier standardized on PW or Rolls engines, it makes sense to try and keep their fleet on that engine. It simplifies maintenance, what parts need to be kept in stock etc.

If you have a fleet of rolls engines and one batch of planes running PW then you have to set aside entire storage, training and supply chains for a single batch.

From Boeing’s perspective, they can sell more airframes with a modular setup that allows the carriers to choose their powerplants. Especially in a worldwide setup where a rolls Royce may be cheaper in one market and a PW cheaper in another across a pond

Cost, supplier redundancy, antitrust laws

These kinds of systems do allow for corruption of course [0].

---

[0]: https://www.bangkokpost.com/thailand/general/1181845/rolls-r...

Also, this is not the first incident and it it's not the first Airworthiness Directive against the PW-4077.

https://duckduckgo.com/?q=PW-4077+%22airworthiness+directive...

While I understand the point you're trying to make, I'd just like to note that if you type any mature engine for any aircraft into a search engine, you're going to find more than one Airworthiness Directive for that engine

No point really, just interesting that they've had an eye on various metallurgy inspections for a while.

This is at least the third engine--with Trent and GE--so maybe those guys had their share of AD's. Also props to the 777 platform for being modular here and bulletproof in general.

edit. It's obviously a tradeoff of accepting a certain number of (usually) contained survivable fan events vs being able to afford flying them.

>>It’s a particular engine they’re concerned about, not the 777 airframe itself.

While literally true, in all practical terms those airframes are grounded. Engines can be swapped but it isn't as simple as swapping a V8 for a V6. These are expensive and physically large objects. There aren't enough spares available to re-engine so many airframes, and it would take years to build a new supply. So any airframe with the listed engines is essentially grounded until the problem can be addressed.

Only the 777s that have PW4000 engines. The 777s with GE or Trent engines are fine.

That’s only about 60 in service planes.

Try ordering 120 new airliner engines. It will take a while. There is no real surge capacity for these things. You would probably have better luck buying used.

Maybe. But most airline companies can ground a small portion of their fleet and it not really affect their outcome. They should have some redundancy built into their maintenance schedules so that 60 planes, even in a single company shouldnt have too much of a flight schedule burden.

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