Aerodynamics ~ Yaw and Twin Rotors
Iconoclast
Join Date: Sep 2000
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Who's tougher? My old man or, your old man.
Actually Transport Canada is a lot tougher than the FAA where aircraft certification is concerned. The FAA will certify a foreign built aircraft based on the certification criteria of the country of manufacture. (Mostly JAR countries). In the case of the A-310 the FAA performed some route proving flights and checked the aircraft for general handling qualities and approved the A-310 for use in American airspace. The FAA for a long time would approve a derivative aircraft by only testing the differences between the new design and the original design no matter how many derivative aircraft designs here were. The A-310 was originally designed and certified to FAA standards, which required an FMECA for all systems. This was at the system level but to get Transport Canada certification the FMECA had to go to the smallest piece part level of every component in a given system, which was much more stringent than the original JAR requirements.
Bombardier tried to certify the CL-604 design based on previously approved versions of the same aircraft. This is based on the FAA and their method of certification. Transport Canada said no and made Bombardier perform the product assurance analyses down to the piece part level just as was done on the A-310.
I assume this also applies to helicopters as well.
Bombardier tried to certify the CL-604 design based on previously approved versions of the same aircraft. This is based on the FAA and their method of certification. Transport Canada said no and made Bombardier perform the product assurance analyses down to the piece part level just as was done on the A-310.
I assume this also applies to helicopters as well.
Iconoclast
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What they see and when they see it.
To: Another KOS
The certification authorities never see the FMECA (Failure Mode Effects and Criticality Analysis) and if they want to see it they must request permission and look at it at the manufacturers' facilities. The FMECA is used to define the failures and their modes and effects of those failures with this information feeding into the Safety Hazards Analysis (SHA). The SHA defines the probabilities of occurrence for different types of failures from minor failures to catastrophic failures. It stands to reason that if you go down to the piece part failures as opposed to trying to define the failures at the component level the information feeding into the SHA will be more detailed and the SHA will be more accurate in predicting the probabilities of the failures and their effects at the airplane level.
Even with the detailed figures as opposed to the less accurate figure the end result is defined by the manipulation of the numbers to show a probability of catastrophic failure at 10 9 or better and it is pure crap.
The certification authorities never see the FMECA (Failure Mode Effects and Criticality Analysis) and if they want to see it they must request permission and look at it at the manufacturers' facilities. The FMECA is used to define the failures and their modes and effects of those failures with this information feeding into the Safety Hazards Analysis (SHA). The SHA defines the probabilities of occurrence for different types of failures from minor failures to catastrophic failures. It stands to reason that if you go down to the piece part failures as opposed to trying to define the failures at the component level the information feeding into the SHA will be more detailed and the SHA will be more accurate in predicting the probabilities of the failures and their effects at the airplane level.
Even with the detailed figures as opposed to the less accurate figure the end result is defined by the manipulation of the numbers to show a probability of catastrophic failure at 10 9 or better and it is pure crap.
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Lu:
Thanks Lu; with regard to the difference between 'piece part' and 'component', how does one regard complicated components such as main rotor gearboxes (and even engines).
Is it possible to do 'piece part' analyses of main gearboxes and if so is damage tolerence considered? Is degradation due to wear considered and is this reflected in TBOs?
If the whole main gearbox (in effect a train of parts) has to meet the 1309 requirement of 10 -9, isn't it difficult considering the number of elements in the single failure path (have I expressed that well enough?).
What is more effective (practical), piece part analysis or component monitoring with HUMS?
It must be nice to be a clever bloke!
Thanks Lu; with regard to the difference between 'piece part' and 'component', how does one regard complicated components such as main rotor gearboxes (and even engines).
Is it possible to do 'piece part' analyses of main gearboxes and if so is damage tolerence considered? Is degradation due to wear considered and is this reflected in TBOs?
If the whole main gearbox (in effect a train of parts) has to meet the 1309 requirement of 10 -9, isn't it difficult considering the number of elements in the single failure path (have I expressed that well enough?).
What is more effective (practical), piece part analysis or component monitoring with HUMS?
It must be nice to be a clever bloke!
Iconoclast
Join Date: Sep 2000
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Smoke and mirrors
To: Another KOS
The piece part analysis would take into consideration every component in the engine or the gearbox including the nuts and bolts that hold the thing together. Damage tolerance is not considered in the analysis. The person doing the analysis will use accepted generic failure rates for each element in the system. If he does not have access to proven failure rates from his factories service records he can select failure rates from approved data sources. The failure rates for a gear might be manifold so in most cases the analyst will select the best number to make sure he can achieve the specified goal for the engine or the gearbox. In some databases the analyst can select the failure rate say for an electric clutch that was used in an atomic submarine. He can manipulate that failure rate by an approved K factor multiplying the failure rate for the atomic submarine clutch in order to get the failure rate for an electric clutch used in a non pressurized area of an aircraft.
You can see by this that the numbers start to skew from reality at a very rapid rate.
In a gearbox the most critical parts relative to catastrophic failure are the “Jesus nut” and the rotor shaft and most likely the analyst will select a failure rate of .01 10 6 which is realistic. The gears and the nuts and bolts will have similar failure rates where bearings would be significantly lower. Gear cases would also be shown as .1 or .01 10 6 depending on the stress loading however in the SHA the gearbox would be shown as a single entity having a failure rate that is an agglomeration of all of the piecepart failure rates. An internal failure of the gearbox would result in an autorotation, which provides the safety net.
Regarding the piece part analysis and the HUMS I would say that the FMECA and the SHA provide the necessary material for the FAA or CAA to approve an aircraft for certification but the HUMS will if it is designed properly and maintained properly will save your ass.
The piece part analysis would take into consideration every component in the engine or the gearbox including the nuts and bolts that hold the thing together. Damage tolerance is not considered in the analysis. The person doing the analysis will use accepted generic failure rates for each element in the system. If he does not have access to proven failure rates from his factories service records he can select failure rates from approved data sources. The failure rates for a gear might be manifold so in most cases the analyst will select the best number to make sure he can achieve the specified goal for the engine or the gearbox. In some databases the analyst can select the failure rate say for an electric clutch that was used in an atomic submarine. He can manipulate that failure rate by an approved K factor multiplying the failure rate for the atomic submarine clutch in order to get the failure rate for an electric clutch used in a non pressurized area of an aircraft.
You can see by this that the numbers start to skew from reality at a very rapid rate.
In a gearbox the most critical parts relative to catastrophic failure are the “Jesus nut” and the rotor shaft and most likely the analyst will select a failure rate of .01 10 6 which is realistic. The gears and the nuts and bolts will have similar failure rates where bearings would be significantly lower. Gear cases would also be shown as .1 or .01 10 6 depending on the stress loading however in the SHA the gearbox would be shown as a single entity having a failure rate that is an agglomeration of all of the piecepart failure rates. An internal failure of the gearbox would result in an autorotation, which provides the safety net.
Regarding the piece part analysis and the HUMS I would say that the FMECA and the SHA provide the necessary material for the FAA or CAA to approve an aircraft for certification but the HUMS will if it is designed properly and maintained properly will save your ass.
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REgarding the KA-32.
It was initially approved for use in Canada with the single hydraulic system under Russian registration, pending the design and approval of the dual hydraulic system and Canadian certification.
The certification is a bit strange "Transport Category with restrictions", if I remember correctly, which doesn't really exist as a recognized category. It was restricted to crew only, but I know they are working on getting a full Transport Category approval. This is going to take some changes of the instrument panel and other things, but nothing that can't be sorted out.
Nick- it also appears that the US has accepted Russian certification methods for materials, if my memory serves me right. But there are still a lot of problems getting Russian made machines accepted, let alone certified, in the West.
It was initially approved for use in Canada with the single hydraulic system under Russian registration, pending the design and approval of the dual hydraulic system and Canadian certification.
The certification is a bit strange "Transport Category with restrictions", if I remember correctly, which doesn't really exist as a recognized category. It was restricted to crew only, but I know they are working on getting a full Transport Category approval. This is going to take some changes of the instrument panel and other things, but nothing that can't be sorted out.
Nick- it also appears that the US has accepted Russian certification methods for materials, if my memory serves me right. But there are still a lot of problems getting Russian made machines accepted, let alone certified, in the West.
Thread Starter
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Flight Safety,
Thanks again for your earlier ideas.
You said; ~ "the flaps .... could even be cycled opened and closed during each rotorblade revolution to apply drag (and torque) where desired."
This idea is particularly attractive to the intermeshing configuration. It's masts are at an angle from the vertical. Therefore, the activation of a rotor air-brake will result in a yaw-pitch cross-coupling, which will cause the nose of the craft to rise.
By having a tip air-brake provide thrust as well as drag, your cyclic idea can provide sufficient lift at the back of the disk to offset the nose up, caused by the rotor's yawing of the craft.
Mechanically, the linkage for this fits perfectly into Shawn's Offset Teetering Hinge.
Thanks again for your earlier ideas.
You said; ~ "the flaps .... could even be cycled opened and closed during each rotorblade revolution to apply drag (and torque) where desired."
This idea is particularly attractive to the intermeshing configuration. It's masts are at an angle from the vertical. Therefore, the activation of a rotor air-brake will result in a yaw-pitch cross-coupling, which will cause the nose of the craft to rise.
By having a tip air-brake provide thrust as well as drag, your cyclic idea can provide sufficient lift at the back of the disk to offset the nose up, caused by the rotor's yawing of the craft.
Mechanically, the linkage for this fits perfectly into Shawn's Offset Teetering Hinge.
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Heliswiss have been operating a KA32 for at least 10 years out of Belpe I am not sure what type of certification flag it flies under, it is a magnificent beast and much quieter than their lusty 214B, which in the land of cuckoo clocks, alpine horns and cowbells is a very good thing...
Wunper
Wunper
