30 min Dry Run Capabilities
No it did notpass the 30 min. it failed in real life at 10 min 47 seconds 47 sec approximately longer than the bench test,
What`I find unsettling is A. the box did not meet the requirement of 30 min run dry, B.the regulator then allowed the lessor level of safety to be certified, C. SK used the 30 min spec to appear in sales literature, presumably when they thought is was feasible?
What steps did they take to correct this erroneous advertising which would have been disseminated to a much larger audience than the rfm, & did the rfm state there was NO 30 minutes run dry
What`I find unsettling is A. the box did not meet the requirement of 30 min run dry, B.the regulator then allowed the lessor level of safety to be certified, C. SK used the 30 min spec to appear in sales literature, presumably when they thought is was feasible?
What steps did they take to correct this erroneous advertising which would have been disseminated to a much larger audience than the rfm, & did the rfm state there was NO 30 minutes run dry
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I find the comments about the MGB run dry capabilities very interesting. When we did the S76 ground school in Oz in the late 70s, the factory sent an engineer out to lecture us. We were quite clearly told the run dry capabilty was 1 hour & this was backed up by the factory pilots who endorsed us. A year or 2 later while flying out to a rig some 254 nm out to sea, at TOD about 200 nm at 8000 ft, the transmission pressure started to drop steadily & the temp rise plus the various warning lights. On arrival at the rig the pressure was zero & the temp on the max red line. I had decided to ditch once those figures were exceeded or nasty noises started as I didn't intend to be the first person to test the 60 mins!
Strange thing, no one ever suggested there wasn't a 60 mins capability.
Strange thing, no one ever suggested there wasn't a 60 mins capability.
From FAR 29.927
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...
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...
Language is tricky.
But from the Advisory Circular:
Section 29.927(c) prescribes a test which is intended to demonstrate that no hazardous failure or malfunction will occur in the event of a major rotor drive system lubrication failure. The lubrication failure should not impair the ability of the crew to continue safe operation of Category A rotorcraft for at least 30 minutes after perception of the failure by the flight crew.
It must be noted that "minimum torque necessary to sustain flight" will be low, of course...which will provide a commensurately lower airspeed. So you obviously can't look at your map and say, "Well, I'm 60 miles offshore, doing 120 knots and my transmission pressure just went to zero. I can make it back to land!" Uhh, nope. Maybe you'll only make it halfway back. Maybe less if there's a headwind.
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I asked the question on the other forum and haven't seen an answer. Since the intermediate and tail rotor gearboxes are "gearboxes," are they required to demonstrate a 30 minute run dry capability?
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The rule only states that it has to run for 30 minutes after a "loss of lubricant." Does it say "TOTAL or COMPLETE loss of lubricant?" Heck no! Does it say "loss of ALL lubricant?" Not even! It just says "loss of lubricant" which we interpret to mean "loss of...SOME...lubricant."
Now, (and without knowing anything about the background of the testing associated with the S92), where a manufacturer employs the delegate who is drafting the test plan, and perhaps witnessing the test, the delegate can have a sense of "shared" accountability, to both the employer, and the regulator. I shall leave that statement at that.
At the times in the past where I have witnessed endurance tests of this type, not only was a time piece a part of the test, but charted information described the observations of the test article at usually one, or at most five minute intervals for the whole test. A test results/observations chart which was only one third as long as the design standard required, would not even be considered for a pass!
As for the term "land immediately", I share the view that the pilot should have some expectation that although a landing is immenent, he retains some opportunity to look for a suitable landing surface with a safe reserve of running time. I sure would not think that the water of the North Atlantic was a suitable landing surface, unless it was calm, and right at shore! And the rationale that from 15000 feet, you have exactly 10 minutes to get down at 1500 FPM, and land! Not a real world expectation in my opinion.
The Lear Fan airplane of the early 1980's employed one propeller and gaerbox driven by two engines, and thus did not make the grade as a true twin engined airplane. To improve the image of the required redundancy, the gearbox had helical teeth on the drive gears, so it could loose a whole tooth and keep running smoothly. It also had a block of wax inside. If you lost the lubricant, the wax got hot and melted, coating the gear teeth for the ride down. The need to go down was indicated by sprung contacts cast into said block of wax, which upon the melting of the wax told the pilot that the oil was gone, and you're running on wax, so head down - no fooling! (my words, not Bill Lear's!). ibelieve that aircraft was required to demonstrate the same 30 minute run time, and did so sucessfully (though the prop provided only thrust, not lift).
I think that a lot has been learned from the Cougar accident, about what we are willing to accept as a showing of design compliance. Our industry and passengers have a big role to play in indicating to the regulator what we will accept as a design standard, and demonstrated compliance. Happily, some of my clients require that I witness tests which are noticably more rigourous that the design standard requires. Perhaps off shore operators will consider requiring helicopter manufacturers to demonstrate compliance beyond the minimums of the design standard (or even just the standard!)
Pilot DAR
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Strange thing, no one ever suggested there wasn't a 60 mins capability
That's been stated often just recently with the ETS debacle that is raging and the stacked 'houses' of collusion toward the debate.
Having operated heaps of heavy machinery at extremely high torque loadings that were made of the best steel, I can say with some experience that it is ludicrous to think that anything that is "DRY" will run anymore than a few seconds at peak loads.
There are only two Rules, when getting into trouble,
1) Unload as much as possible the torque settings, and
2) Inject some form of clinging lubricant to sate the grinding appetite of the affected component until the nearest landing place is reached.
What a stupid debate and a false advertising program from the past it seems, as has been suggested here and on previous threads.
Just design the blessed components with an add on lubricant dispenser that the pilot can activate at intervals to sustain life whilst safety is reached
Tonight I pray that Turnbull and the opposition Libs will inject some suitable brain juice into their grinding argument.
cheers tet
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TopEndTorque,
Exactly !
Industry's just got to make some decisions :
Do you need run dry (uncontained oil loss) redundancy ?
If yes, how much, i.e. 10,30,60,90 mins etc..?
Who's responsibility is it to make the above determination/s ?
Just design the blessed components with an add on lubricant dispenser that the pilot can activate at intervals to sustain life whilst safety is reached
Industry's just got to make some decisions :
Do you need run dry (uncontained oil loss) redundancy ?
If yes, how much, i.e. 10,30,60,90 mins etc..?
Who's responsibility is it to make the above determination/s ?
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At the time of the Lear Fan was in the testing stage I had the chance to have a look at the insides of the gear box and also inspected a gear box which we we informed had run for the required thirty mins with no lubricant other than the so called wax, If my memory serves me right after all these years I do not recall seeing any sign of heat stress or chunks of metal inside the case, maybe time to re visit this system methinks.
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FH100 Pilot,
reading on from your extract of AC 29.297A - Additional Tests, one sees this text:
Whilst I agree with your contention that the language is, of necessity, imprecise, use of the word drained does rather suggest that the colloquially used term 'run dry' is close to the real meaning.
Mars
reading on from your extract of AC 29.297A - Additional Tests, one sees this text:
A bench test (transmission test rig) is commonly used to demonstrate compliance with this rule. Since this is a test of the capability of the residual oil in the transmission to provide limited lubrication, a critical entry condition for the test should be established. The transmission lubricating oil should be drained while the transmission is operating at maximum normal speed and nominal cruise torque (reacted as appropriate at the main mast and tail rotor output quills).
Mars
Mars, I'm with you 100%!
Run it in simulated flight conditions, drain the oil out, reduce mast torque, then see how long it runs. In the case of the S-92 it was 10 minutes. That was when SAC had to resort to Plan B.
The italicized text in my post (#23 in this thread) was facetious and not to be taken seriously, but was meant more as one possibility of how things get interpreted when there is room for it.
Run it in simulated flight conditions, drain the oil out, reduce mast torque, then see how long it runs. In the case of the S-92 it was 10 minutes. That was when SAC had to resort to Plan B.
The italicized text in my post (#23 in this thread) was facetious and not to be taken seriously, but was meant more as one possibility of how things get interpreted when there is room for it.
js0987
Since no-one else is answering you, I will have a go. 29.927 applies to the transmission as a whole, not just to the MGB. Therefore the intermediate and tail gearboxes must have passed the test. Because these gearboxes run at very much less torque than the MGB, and have a much greater surface area to volume ratio (for cooling), I think the loss of oil thing is much less significant and I doubt any of these types of boxes would have difficulty passing the test. Indeed these gearboxes generally don't have a cockpit warning that oil level is low. They may have a temperature warning but I am not sure how that would behave with a sudden loss of oil - I am not convinced that it would show a particularly high temperature since it would be measuring air temperature inside the box and with the relatively good surface cooling I doubt that would get particularly high so maybe no in-flight warning.
Except for Sikorsky boxes of course, which one assumes only met the "extremely remote failure" part of the requirement
HC
Since no-one else is answering you, I will have a go. 29.927 applies to the transmission as a whole, not just to the MGB. Therefore the intermediate and tail gearboxes must have passed the test. Because these gearboxes run at very much less torque than the MGB, and have a much greater surface area to volume ratio (for cooling), I think the loss of oil thing is much less significant and I doubt any of these types of boxes would have difficulty passing the test. Indeed these gearboxes generally don't have a cockpit warning that oil level is low. They may have a temperature warning but I am not sure how that would behave with a sudden loss of oil - I am not convinced that it would show a particularly high temperature since it would be measuring air temperature inside the box and with the relatively good surface cooling I doubt that would get particularly high so maybe no in-flight warning.
Except for Sikorsky boxes of course, which one assumes only met the "extremely remote failure" part of the requirement
HC
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As i have told before, i have never actually experienced a total loss of xmsn oil....
But i had a total loss of hydraulic fluid during mission flight at night (under NVG).
In the Bell 205, we only had one hydraulic system-so no redundancy available.
I decided to land ASAP-not one second thinking about stretching the landing and making it to the next airfield, which would have been a 15-minutes flight..
The mechanics found a broken seal and changed it.
In my opinion it doesnīt matter what the industry says-they are not sitting in the helicopter with me...
As a pilot (and as a Captain, too) we have to make the right decisions-to satisfy our customers, but to always keep the crew and aircraft well...
But i had a total loss of hydraulic fluid during mission flight at night (under NVG).
In the Bell 205, we only had one hydraulic system-so no redundancy available.
I decided to land ASAP-not one second thinking about stretching the landing and making it to the next airfield, which would have been a 15-minutes flight..
The mechanics found a broken seal and changed it.
In my opinion it doesnīt matter what the industry says-they are not sitting in the helicopter with me...
As a pilot (and as a Captain, too) we have to make the right decisions-to satisfy our customers, but to always keep the crew and aircraft well...
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I donīt like discussing like "What would have happened if...."....
To be honest-I cannot tell you how i would have reacted..
As i told above-anything that keeps
1. Crew and passengers safe
2. Keeps the helicopter serviceable (or at least reparable)
will be okay.....but it is like most things:
Only success dictates the right way...unfortunately, you will only find out when it is too late...
To be honest-I cannot tell you how i would have reacted..
As i told above-anything that keeps
1. Crew and passengers safe
2. Keeps the helicopter serviceable (or at least reparable)
will be okay.....but it is like most things:
Only success dictates the right way...unfortunately, you will only find out when it is too late...
At least a 30 min run-dry capability might allow the option in high sea states of hover jumping the pax and rearcrew with their dinghies so at least they don't have to worry about getting out of an upturned helicopter - as the pilot you get to do the tricky bit of landing on the water and safely egressing by yourself.
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HC
Thanks for your analysis. Sounds spot on, but I notice its still supposition. Frankly, I think that's good. While we all want to know the aircraft and its systems, I don't think its a good idea to know the destruct limits that every system was tested to. Perhaps an example of too much knowlege being a bad thing.
Thanks for your analysis. Sounds spot on, but I notice its still supposition. Frankly, I think that's good. While we all want to know the aircraft and its systems, I don't think its a good idea to know the destruct limits that every system was tested to. Perhaps an example of too much knowlege being a bad thing.
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Ditching doesn't have to be an all-engines out plop onto the water. Imagine sitting on the water (even with it heaving the machine up and down) with the rotors still turning and people exiting (more or less calmly) into a liferaft that the helicopter then water taxis away from before the crew shuts things down and exits themselves?
Does anyone even think about this sort of procedure? Does anyone practice it in the sim?
Ditching doesn't have to be a hit-the-water-instantly-turn-upside-down thing. Better to have the transmission self-destruct on the water than in the air.
Does anyone even think about this sort of procedure? Does anyone practice it in the sim?
Ditching doesn't have to be a hit-the-water-instantly-turn-upside-down thing. Better to have the transmission self-destruct on the water than in the air.