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Comment by InTheArena | Hacker News Reader

The FAA does a great job with general plane safety. Boeing does a great job with Safety. It's great to see this in public, so we can understand the system that leads to aviation being a unbelievably safe form of transportation, while still being responsive to the market.

(See https://www.popsci.com/why-air-travel-became-so-incredibly-s...)

All of that said, the modern generation of engines are so complex to hit their efficency windows, it's majorly impacting airlines. The A320-NEO engines by Pratt & Whitney have huge problems that have significantly impacted airlines and carriers, while GE is struggling with this problem.

All of these are engineering problems, with a complex trade-off between efficiency (fuel), safety and cost.

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I worked on engines like these about 5 years ago and they are incredibly finicky and easily require up to 8x the amount of time and attention just to process through one step than a 'standard' engine part.

I don't envy whoever is responsible for shipping these on time.

There's also a problem with the Trent 1000, the other engine option on 787s:

https://www.reuters.com/article/us-rolls-royce-hldg-trent100...

Basically, the compressor is not lasting near as long as expected, and, since it's a safety-critical part, airplanes are spending a lot of time on the ground awaiting expensive inspections and repairs that weren't in anyone's maintenance schedule.

Also everyone is futzing with business models. There are maintenance facilities from many companies all over the world that can work on airframes, engines etc. The airframe and engine manufacturers are seeing all this post-sale income go to those companies, and not back to the manufacturer. So they are "fixing" that.

For example Rolls Royce does "power by the hour" where the airline is essentially paying rent on the engine while it is in use. That means Rolls takes care of the maintenance etc (all rolled into the per hour price). There are far fewer Rolls locations that can do that work. Then suddenly a lot of maintenance work needs to be done, and planes have to wait.

For those interested in aviation, I recommend following leehamnews[1]. The industry is very similar to what is faced in the software industry but over far larger timescales. eg airframe manufacturers have constant streams of improvements, but have to work out if and how to charge for them, how to do deal with existing aircraft of the same model without them ("backwards compatibility"), and the constant spending money to make money. You even see second system effects (arguably the birth of the 787 was just that financially, manufacturing and technically).

[1] https://leehamnews.com

And Rolls wants their suppliers to be doing JIT delivery of all their parts--no one in the supply chain wants to be stuck holding the bag on inventory so Rolls expects to whistle at Pratt-Whitney for parts, and Pratt expects to be able to whistle at their suppliers (and down and down the supply chain) and still be able to get parts within an incredibly short window. Oh and they don't want to pay for anything they order until 6 months after receiving delivery. Its an incredibly tough squeeze on the supply chain.

You can tell some of my customers are in aircraft engine manufacturing.

The problem with JIT is the same as the problem everywhere else: When the wrong type of bean counters look at a cost too nearsightedly, they typically address the "static" costs and miss the hidden costs that are much harder to both understand and measure - typically "dynamic" costs that are both under-reported and hard to measure, and also to understand since there are a lot of moving parts.

The whole point of JIT is to take control of the dynamic effects so it's a bit ironic.

JIT works when those making the decisions are experienced engineers with financial knowledge, not bean counters without domain experience (IMHO).

There was a lot of coverage of the 787s problems in Polish media recently and it brought to light one thing regarding these engines that really frightens me. Quoting the (leaked?) memo:

>The experience with General Electric Engines, which had experienced perhaps two shut downs on the Boeing 767s in over 20 years, had given the airline a sense of security so that the shut down of one engine did not cause any pressure, the probability of the failure of the second engine was rated minimal.

>Rolls Royce on the other hand had taught the airline however, that this was not true. From RR bulletins it is clear that the shut down of one engine dramatically increases the likelihood of the other engine failing. This forces us to revise our approach to ETOPS.

http://avherald.com/h?article=4b69e455

Similarly, the Leap CFM56 engine (used on the 737 max) has failed (ie, boom) several times now, once fatally un-contained. I think they have quality issues with blades fatiguing and letting go.

https://www.seattletimes.com/business/boeing-aerospace/one-s...

The CFM56 (that failed on the Southwest flight recently) is actually a fairly old engine design - it ran for the first time in the 1970s, and has been in service on the 737 for decades. Based on total run time, it's actually one of the more reliable jet engines ever created.

The equivalent product for the A320NEO/737 Max is called the Leap 1A/1B. It's doing better than many of the new generation of jet engines, but it also has a flaw that requires a certain part to be replaced on all ~500 or so in-service engines.

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