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German military kicks off heavy lift helicopter competition

reuters.com

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Re: German military kicks off heavy lift helicopter competition

#41

Post by colechristensen »

geezerjay wrote: post #36
rbanffy wrote: post #6

Earlier quoted context omitted.

We shouldn't underestimate what we don't know about building machines. Maintenance should accommodate time to check for wear on parts we don't expect to, to check things that are different from what we expect them to be. The problem was there for decades and one inspection in one unit over that period would probably have evidenced the issue and added one more item for the maintenance checklists. It's not like the man…

> Maintenance should accommodate time to check for wear on parts we don't expect to How much time do you spend performing exhaustive checks for problems that don't exist?

You should.

You absolutely should spend time looking for things you expect not to find, because sometimes you will be wrong.

When you're maintaining an aircraft, a nuclear plant, or anything sufficiently complex or life critical, you should spend a certain amount of time looking for ghosts. You _will_ find them. Your model of an engineered system should include a finite rate of unknown bugs.

Re: German military kicks off heavy lift helicopter competition

#42

Post by colechristensen »

icebraining wrote: post #12
foldr wrote: post #10

Earlier quoted context omitted.

A 747-400 has 6 million parts (according to Google). Good luck inspecting all of those.

On each plane it would not be reasonable, but on a few planes it could be done, and would detect defects like the one described above.

The reasons planes are so safe is because there are several "unreasonable" things about designing and maintaining aircraft that most engineers would think somewhere between unnecessary and ridiculous.

A lot can be learned from aerospace engineering and the systems engineering used to design air and space vehicles.

Re: German military kicks off heavy lift helicopter competition

#43

Post by khamisiyah »

distances wrote: post #34
leroy_masochist wrote: post #27

Earlier quoted context omitted.

Not sure it makes sense to buy military aircraft from any given country if being able to stop them from invading you is your military's primary mission.

It depends a bit. For example Finland used to use a lot of Soviet weaponry while (practically if not officially) preparing to deter Soviet attack. Some upsides: - Results in trade deals with a neighboring superpower - In case of war, looted enemy armament is familiar and compatible - Cheaper due to Soviet attempts to keep sphere of influence (e.g. no direct NATO compatibility)

To add to this comment, the majority of Finland's infantry fighting and transport vehicles that in use are still Soviet BMPs and MTLBs. Same applies to artillery and also all light machine guns are and probably will Russian PKMs for a while.

But yeah since the fall of USSR they've been slowing shifting towards buying from NATO countries/allies, with German Leopard tanks having replaced T-72s and recently buying artillery units from South Korea.

Re: German military kicks off heavy lift helicopter competition

#44

Post by rbanffy »

geezerjay wrote: post #36
rbanffy wrote: post #6

Earlier quoted context omitted.

We shouldn't underestimate what we don't know about building machines. Maintenance should accommodate time to check for wear on parts we don't expect to, to check things that are different from what we expect them to be. The problem was there for decades and one inspection in one unit over that period would probably have evidenced the issue and added one more item for the maintenance checklists. It's not like the man…

> Maintenance should accommodate time to check for wear on parts we don't expect to How much time do you spend performing exhaustive checks for problems that don't exist?

Very little. In this case, a single inspection (assuming all units were affected) over a period of 20 years would have prevented losses that more than compensate the effort of the added scrutiny.

Also, I like to be the first to know I'm wrong. If I make 100 aircraft and dedicate one to disassembly for study after a quarter of its estimated life, I'll be a .75% investment on better understanding my product. If De Havilland had done that, the stress on the square windows of the Comet would have been discovered before they started falling from the skies and we'd all be flying more beautiful planes.

I was shocked when I found out that, in more than 100 flights, nobody inspected the underside or the leading edges of the shuttle in orbit to check for damage incurred on lift off. They were pretty sure the only dangerous part of the flight was the re-entry.

You say a problem does not exist. You may have good reason to think it doesn't, and, yet, people die because it does.

Re: German military kicks off heavy lift helicopter competition

#46

Post by azernik »

dingaling wrote: post #9

Same two contenders as the original competition in 1965! Significantly updated but still disappointing in showing how little aerodynamics has progressed in five decades.

This is what mature technologies look like. We also had rapid change (and obsolescence) in infantry rifles in the late 19th and early 20th centuries, and one big jump when the assault rifle was adopted, but since then mostly minor changes.

Re: German military kicks off heavy lift helicopter competition

#47

Post by foldr »

cm2187 wrote: post #15
foldr wrote: post #10

Earlier quoted context omitted.

A 747-400 has 6 million parts (according to Google). Good luck inspecting all of those.

I believe that B747 do get regularly tear down. They basically remove all the cabins, lots of the conduits and wires, remove the instruments in the cockpit, inspect hidden areas, and reassemble the whole thing. https://en.wikipedia.org/wiki/Aircraft_maintenance_checks#D_...

A tear down doesn't necessarily involve inspecting every part.

Re: German military kicks off heavy lift helicopter competition

#48

Post by foldr »

alexanderstears wrote: post #13
foldr wrote: post #10

Earlier quoted context omitted.

A 747-400 has 6 million parts (according to Google). Good luck inspecting all of those.

During the D maintenance, every part should be inspected. Things like fuel lines should be inspected much more regularly, ideally more often than it would take to rub through a fuel line. But a visual inspection on a fuel line can be really difficult. I had a motorcycle with a leaky fuel line once, luckily it sprung a leak while warming up in my driveway and I turned off the bike before anything bad happened but it w…

If the 6 million parts figure is correct, it's obvious that it is not possible to inspect every part of a 747. Suppose we allow 1 minute per part inspection. Then that's still about 11 years of inspection time (without taking any breaks!)

Re: German military kicks off heavy lift helicopter competition

#49

Post by tyingq »

colechristensen wrote: post #42
icebraining wrote: post #12

Earlier quoted context omitted.

On each plane it would not be reasonable, but on a few planes it could be done, and would detect defects like the one described above.

The reasons planes are so safe is because there are several "unreasonable" things about designing and maintaining aircraft that most engineers would think somewhere between unnecessary and ridiculous. A lot can be learned from aerospace engineering and the systems engineering used to design air and space vehicles.

Also, a fair amount of the safety of civilian aircraft is because the aircraft owners don't get to skip critical processes, maintenance, etc. They have to answer to regulatory agencies, inspections, etc.

The US military polices itself, so important things can be made optional. They don't have to answer to the FAA on maintenance issues, for example.

Re: German military kicks off heavy lift helicopter competition

#50

Post by vkou »

distances wrote: post #34
leroy_masochist wrote: post #27

Earlier quoted context omitted.

Not sure it makes sense to buy military aircraft from any given country if being able to stop them from invading you is your military's primary mission.

It depends a bit. For example Finland used to use a lot of Soviet weaponry while (practically if not officially) preparing to deter Soviet attack. Some upsides: - Results in trade deals with a neighboring superpower - In case of war, looted enemy armament is familiar and compatible - Cheaper due to Soviet attempts to keep sphere of influence (e.g. no direct NATO compatibility)

Another upside:

- Making it clear that you're not in the 'other guys' camp.

A NATO Finland would have been incredibly threatening to the Soviet Union. A friendly, non-aligned Finland that just wants to be independent, without stepping on anyone's toes is a useful buffer state.

After the second world war, Finland had to tread very, very carefully.

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