Slightly off topic, but related.

Big chunks of the 76 are built offshore too, Czechoslovakia springs to mind.

I don't think there are many civilian transport aircraft or helicopters these days which are exclusively made in a particular country, the concept of 'Buy American' or 'Buy European' is somewhat facile and does not reflect the globalisation of the lower tier suppliers. Think how many PWC PT6 engines are installed in 'American Helicopters' for example and the proportion of the aircraft ticket price that the engines represent.

TOD

In US business, the bottom line is usually: Making a profit. If Martians outbid everyone else and make the part to the drawing then that's fine.

The only glitch these days comes when parts are made and assembled outside the US. For the most part, SAC farms out abroad a lot of parts but assembles the end item within its plants. Kind of a "Sorta American Made" product that keeps share holders especially happy and worker bees at a low grumble stateside.

NL 3-Hour Gearbox Run Quote
 

Sven, as I recall, the main box was run 3 hours without oil pressure, not without all oil. I cannot recall whether the test was terminated for cause, or whether the three hours was thought to be sufficient.

Just wanted to clarify that one point.

Thanks,
John Dixson

John

What do you think a customer would believe can be done without oil in the MRGB vice simply without oil pressure? And, how would a crew figure it to be one, or the other problem if pressure were to quickly indicate zero in flight?

Thanks.

WIII

Inferences
 

Whirlwind, I just meant to add what I recalled on that particular subject, not to imply that it had a bearing on the tragic accident in Canada. I mean, its very nice to know that one can lose both pumps etc etc, but that test is not particularly relevant to the issue at hand.

Thanks,
John Dixson

John

Difficult subject. No inference taken or intended. Very tragic accident.

Probably a subject best left to the experts, and I'm not one of those.

WIII

John,

As I heard it from sources present....the test was called off as it had run well beyond the maximum fuel endurance of the aircraft which was felt sufficient time.

Also....as I have seen in the checklist....oil pressure less than 5 psi has always required...."Land Immediately!"

One has to assume a complete loss of oil would result in a "zero" oil pressure thus an immediate landing would be the correct thing to do.

I think the test was run without cooling not without pressure.

Jim

I believe it was run in the same configuration as the Norsk Aircraft was in, following it's pump (drive) failure - the oil cooler bypassed (so no cooling) and the good pump driving oil predominently through the windmilling 'failed' pump, thereby providing some, but very little, pressure - close to 5 psi. I think it was run for around 3 hours, as John confirms.

The outcome was extremely favourable, from a technical perspective, insofar as the mechanical integrity of the dynamic componants was extremely sound i.e. there was no damage. That's not to say that there would not have been a whole bunch of very unpleasant cockpit indications, had the MGB been in flight, with secondary failures of the AC Generators likely and probably smoke and smell. It got very, very hot!

3 Hour Run
 

Jim L, I believe you are correct:Last night I was thinking that the test was run to test a failure of the bypass valve and that the pressure was up in that case.

Let me make a call to get it right. May take a day or two.

Thanks,
John Dixson

John, I respect the confidentiality of the information I receive in face to face briefings and e-mails, but I believe most of what I've described above is public domain by way of the AOL content and numerous webcasts to operators. I believe it to be correct. Let us know if it's not. Cheers

3 Hour Run
 

212, your note rang a bell and you are most probably exactly right.

Thanks,
John

I think they also let quite a bit of oil drain from the gearbox before they bypassed the cooler so the contents would be lower than expected following an actual event in which the crew would have to react to the situation. That reduced the amount of oil by a considerable amount which would have reduced the cooling ability as well.

..........now why do you think would they have done that ?

Gents

Interesting, OK, I'll bite. What's the difference between run-dry capability as demonstrated on a test stand and fly-dry capability for a MRGB at cruise?

WIII

As far as I can see they never demonstrated any run dry capability. They demonstrated run for 3 hours at reduced oil pressure and reduced oil capacity at one would assume cruise power settings. It was mentioned earlier that if failed the 30 minute test at cruise power with zero oil ,certification was achieved as they persuaded the FAA that complete loss of oil was an extremely unlikely occurance. The test is very specific , you start the test at full cruise power and then drain all oil and start the clock when the pressure is indicated at Zero.( perception of lube system failure )

far 29.927 quote below.

(c) Lubrication system failure. For lubrication systems required for proper operation of rotor drive systems, the following apply:
(1) Category A. Unless such failures are extremely remote, it must be shown by test that any failure which results in loss of lubricant in any normal use lubrication system will not prevent continued safe operation, although not necessarily without damage, at a torque and rotational speed prescribed by the applicant for continued flight, for at least 30 minutes after perception by the flightcrew of the lubrication system failure or loss of lubricant

widgeon

Apologies for not having remembered the previous post concerning the 30 minute test. Perhaps the FAA apply some sort of statistical probability to the use of the words extremely remote; maybe 10 -7th.

Tragic accident.

Thank you.

WIII

3 Hour Run
 

SAS, Jim L and 212, ( as you'll see below, your sources are very good! )

Talked to an old friend earlier today, who passed on the following re the 3 hour run, ( the one that I think was the run referred to by Nick ):

It occurred after the decision was made to install the bypass switch, and in fact the first 30 minutes of the run was done so as to met the requirements of FAR 29-927. Both pumps were running and a leak was forced on the cooler side of the bypass switch. After 5 seconds the bypass switch was thrown and the box was run with both pumps on with the oil remaining ( pressure was now much reduced due to the reduced amount of oil remaining in the box ). After the 30 minutes was up, the test was nonetheless continued to the 3 hour mark and some 30 min segments were run at higher power, looking forward to higher gross weights in the future. So this run was part of the original certification, and, while interesting background, does not seem directly connected to the tragic CHC accident.

There was some other testing done after Norsk, but I didn't ask about that because I was sure that discussion is a part of the investigation.

Thanks,
John Dixson

John,

Are you saying that the test you described was deemed succussful in demonstrating compliance with the FAR 29.927 Lubrication System Failure testing requirement, and the "extremely remote" clause wasn't used ?