Menu Sign In Contact FAQ
Banner
Welcome to our forums

Why doesn't aviation use standard (metric) units?

I guess if Pietenpol USA had designed these ridiculous € 5.- Socata M 4 screws with non standard taper heads you´d have to buy them from some specialist at his price. I don´t believe anybody would have entered this mini business for everybody to get these at big aviation stores at penny prices.

So who makes these funny prices , the EU parlament ? No, it is Socata who do the ripoff !
If you need new bolts for conrod big end caps for your Opel you´d be lucky, for Porsches you probably pay five times that Opel price, same precision, same material – but very different company attitudes ! And I guess you don´t get that type of bolts for your Lyconti from big aviation stores but from specialised suppliers only, not for cents. Would you get precision machined wing bolts from big US stores ? I would not think so . Maybe for spam cans that were thrown out in tens of thousands ? That kind of production runs was never seen in EU and will never happen in future so it is logic that nobody will enter a business for small batches of parts to sell them at discout prices. In consequence parts prices for surviving Dorniers , Bückers Zlins etc. will remain higher than mass produced “standard” items in US. That has little relation with metric system or imperial system, just a matter of high production runs.
Anybody here with technical background on Airbuses or Eurocopter ? Are these metric produced or imperial ? Can´t believe that all machining on these was imperial when all production is in EU. Same goes with Diamond and Rotax, Embraer, Pilatus and Saab as well, I believe, no imperial hardware on these – but big numbers produced.
As to metric hoses, again, prices are always political and are made by the supplier/aircraft company. I had a set of 29 metric hoses from Lithuania at € 1300.- inc. shipping , € 35.- per hose, including EASA form 1 of course. I could get any hydraulic hose commercially made for 300 bar systems started at below € 10.- depending on length of course. Would be perfectly safe in an aircraft but some hoses have to be changed in 10 years intervals so I would not have bands on these showing production date.
Anyway, prices are political depending on company attitudes and size of production runs mostly.

Vic

vic
EDME

it is Socata who do the ripoff !

Of course, and you cannot blame them (it’s human nature) but if the TB aircraft used AN etc parts throughout then the opportunity would not exist.

Anybody here with technical background on Airbuses or Eurocopter ? Are these metric produced or imperial ?

My A&P/IA works on Airbuses and tells me they use AN parts, US NPT hoses, etc. Presumably this was done to get market acceptance around the world.

Administrator
Shoreham EGKA, United Kingdom

Martin2 wrote:

Always been somewhat puzzled as watching the SpaceX launches everything is in metric, altitude in Km, speed in km/h, range Km, yet reading their literature they build in Imperial – they seem to have no problem in production but I assume it is just easier as all the tooling and materials will come from the US.

One of the possibilities when doing business with the US military is that you sign a contract requiring metrification, which is a remnant of an old 1970s Carter era congressional initiative. Then immediately after award, you start work under technical requirements that mandate use of US standard SAE or AN etc hardware. The benefits of scale that go along with that widespread military requirement is one reason why even space stuff, which operates at a stratospheric level of cost, uses US standard hardware. (oddly enough it’s not called Imperial )

Peter wrote:

However we are now debating European restrictive practices / moneymaking schemes, rather than the merits of the different measurement systems.

Or in other words, is the role of government to introduce useful standardization which eliminates monopoly practices and increases our standard of living, or alternately to enforce monopoly practices which ultimately support a ruling aristocracy favored by those in power. That issue like many is highlighted in regulation of aviation, and is more economically important than adherence to a particular system of units.

Re commercial hardware, I can buy anything in any units locally. US standard SAE etc might be a little bit easier, but roughly 11.25 of my 13 vehicles are metric and I’m often found buying odds and ends for them at the industrial hardware place, which is open on Saturdays and conveniently located halfway between home and hangar

Last Edited by Silvaire at 09 May 14:11

Peter wrote:

Of course, and you cannot blame them (it’s human nature) but if the TB aircraft used AN etc parts throughout then the opportunity would not exist.

Same, if they had used DIN EN ISO – parts, so no argument on the topic.

mh
Inside the sky.
EDXE, EDXF, Germany

@mh, would you feel comfortable specifying non-aircraft-certified DIN EN ISO etc. industrial hardware for structural or mechanical applications on a certified aircraft? To be meaningful and effective for owners, that would mean the parts book will call out hardware that the mechanic in the field will purchase from any industrial hardware supplier, not by airframe specific part number from a single source.

Last Edited by Silvaire at 09 May 15:10

Sure. DIN EN ISO also specifies strength values.

mh
Inside the sky.
EDXE, EDXF, Germany

I think the issue is quality control and I find it hard to believe the QA requirements for commercial hardware, supplied by any commercial vendor without airframe manufacturer involvement, would be acceptable to aircraft certifying authorities.

The way commercial hardware is ‘certified’ on LSA aircraft is to require that the mechanic buy the hardware from the airframe manufacturer, which is the problem long since solved on other aircraft by AN MS bolts etc, and not a solution.

Last Edited by Silvaire at 09 May 16:33

So please stick to one system of units: US gallons for fuel with 6 lbs for a gallon (standard temp. and pressure) and NM. The incursion of statute miles in the aeronautical world js already confusing (Wind reports, distances, etc..) but metric would be worse.

Everybody should remember the “Gimli glider”.

…Air Canada Flight 143 (Boeing 767) was a scheduled domestic passenger flight between Montreal and Edmonton that ran out of fuel on July 23, 1983 at an altitude of 12,500 metres (41,000 ft), midway through the flight. The crew was able to glide the Boeing 767 aircraft safely to an emergency landing at a former Royal Canadian Air Force base in Gimli, Manitoba, that had been turned into a motor racing track. This unusual aviation incident earned the aircraft the nickname “Gimli Glider.”

The subsequent investigation revealed that a combination of company failures, human errors and confusion over unit measures had led to the aircraft being refuelled with insufficient fuel for the planned flight.

During the flight, the management computer indicated that there was still sufficient fuel for the flight but only because the initial fuel load had been incorrectly entered; the fuel had been calculated in pounds instead of kilograms by the ground crew and the erroneous calculation had been approved by the flight crew. This error meant that less than half the amount of intended fuel had been loaded. Because the incorrect fuel weight data had been entered into the system, it was providing incorrect readings. A few moments later, a second fuel pressure alarm sounded for the right engine, prompting the pilots to divert to Winnipeg. Within seconds, the left engine failed and they began preparing for a single-engine landing….

I leave you with the rest of the story to be read on the attached link.

https://en.wikipedia.org/wiki/Gimli_Glider

Canada

Goldeagle wrote:

The incursion of statute miles in the aeronautical world is already confusing (Wind reports, distances, etc..)

Its not an incursion, its a defense At all times prior to 1969, FAA airworthiness standards (14 CFR Part 23) for small aircraft specified that distances were to be in statute miles, and speeds in miles per hour. Before that, nautical miles were a foreign concept for most light planes, pilots and aeronautical operations worldwide. I think the introduction of nautical miles was a mistake, and I see no practical reason why nautical miles exist at this point.

Last Edited by Silvaire at 09 May 22:56

ImSilvaire wrote:

Before that, nautical miles were a foreign concept for most light planes, pilots and aeronautical operations worldwide. I think the introduction of nautical miles was a mistake, and I see no practical reason why nautical miles exist at this point.

I’m with Silvaire here. Certainly miles and mph would make more sense to use in the US and km and km/h in Europe.

Using nm and kts is somewhat fair though, as neither Americans nor Europeans are forced to use units familiar to the other. Instead, both have to adapt to unfamiliar units.
Last Edited by MedEwok at 10 May 01:23
Novice pilot
EDVM Hildesheim
Sign in to add your message

Back to Top