Helicopter Age versus reliability

[peter manktelow]

read this first.................

http://timesofindia.indiatimes.com/cms.dll/xml/uncomp/articleshow?msid=134410

Ever since the demise of the Boeing 737 that shed a good part of its skin in Hawaii many years ago , we have been hearing from the various oil companies that helicopters over 10 years old are no longer acceptable for their contract bids. This , of course , is music to the ears of the helicopter manufacturers. You cant blame them for wanting to sell more machines. That is what they are in business for.

My point , however is this....is it a reasonable argument to compare aging helicopters with aging (pressurized) jets. Do our helicopters suffer the same or similiar fatigue with age ? Or is the industry getting confused with maintenance standards

Is it still not the case that a particular serial number helicopter may possess (many years later) only one of its original parts ie its data plate ???!!! (I say this with tongue in cheek , but......)

Take the S76A++ (or the Shortsky) It started life as an A model in say 1979 but is converted to A++ in 1999. When do you start the 10 year clock running with this helicopter?

THE AGING HELICOPTER DEBATE ?????

...but of course I would rather fly a brand new helicopter but I also get a little discombobulated with an argument that seems to have holes in it...big ones !

over to you..........

[John Eacott]

"ONGC is mulling forming its own helicopter division with a fleet of more than 20 modern aircraft."

Ah yes, ONGC, the mature operating company who couldn't even provide working fire extinguishers in the hangar :p Peter, don't you recall David and the superglue incident :D The very thought of ONGC.....no, I mustn't.

Re the "old" airframe bit, as you said it can be like Henry VIII's axe. Five new ax heads, and 7 new shafts, but it still has the same data plate. My 206A, reworked as a BIII, will perform as well as a brand new EC120, and at a known cost. That, plus the known support from Bell, will keep me happy for a while yet.

[GLSNightPilot]

We'll see how this factor plays out in the GOM in a few years. The two largest operators, Air Log & PHI, have gone in opposite directions - PHI with converted S76A++'s, & Air Log is buying new S76C+'s. Time will tell. It's not clear, however, that Air Log really wanted new aircraft, but PHI reportedly bought all the A++ conversion kits available, leaving Air Log with no choice but to buy new because they were late in starting to convert the A models they have.

[inthegreen]

I agree with you. I think this is an example of someone making a policy without really understanding the principles. Total age of the airframe has little to do with fatigue in helicopters. As we all know, it all has to do with power cycles and/or corrosion. An aircraft heavy lifting for 10 years at 20 cycles per hour is probably way past retirement status. One that has been doing personnel transport at 1 or 2 power cycles per hour is just getting broken in and comfortable to fly by 10 years. If there is no evidence of airframe fatigue or stresses and no instance of failure, what is the point of replacement? In addition, imagine the additional cost of the contract if a ten-year aircraft replacement had to be built in.

[Lu Zuckerman]

Not all helicopters are equal when it comes to reliability. I am not referring to actual in flight performance reliability but instead I am referring to predicted reliability. In the case of predicted reliability this prediction is made mainly on large helicopters that will be certified for passenger service.

In the performance of the predicted reliability the analysts will use failure rates (when possible) that are at the flat portion of the so-called bathtub curve. They do not consider infant mortality nor, do they consider failures due to excessive use or cycles (old age). When it is not possible to use failure rates that have been proved in service then the analyst will draw from other failure rate databanks that contain failure rates that may or may not apply to helicopters or for that matter aircraft in general. In any case the analyst will crunch the numbers until he can show that the helicopter meets or exceeds the requirements set down by the certification authorities.

The factory will then market the helicopter on the basis of the predictions and the spares will be predicated on the predicted rates of failure. There is a remote possibility that under specific operational conditions that the helicopter might and I emphasize “MIGHT” achieve the predicted reliability. This achievement is based on operational conditions, the number of times the helicopter is operated under extreme conditions (High stress levels), the quality of the maintenance, the change out of parts at the recommended time and other contributing factors.

In most cases the repair manuals will have minimum content. The content is not expanded until service difficulties have manifested themselves. ADs will be issued and will be incorporated in the repair manuals at six-month intervals. These service difficulties can range from minor items to those that resulted in a crash. If a crash results from a single point failure the manufacturer will not be held liable by the certification authorities if they change the design or come up with a repair solution.
Nothing is ever as reliable as predicted. As many of you have said “Never fly the A model of anything”. However some failures do not manifest themselves until the models B, C, D…. Are flying.

Here is an example of operating under stress: The CH-47 because of its’ flight control system operates with both rotors in full collective with no forward cyclic being introduced. During this period the helicopter is usually operating at near max gross. The rotor heads among other dynamic components are sent back to the factory for overhaul and or repair. When the rotorheads are disassembled and inspected over 60% of the high stress parts are rejected due to overstress and resultant cracking. In another few hours of high stress operations the parts could fail. On a Sikorsky head the parts can be reworked and placed back in service for many more operating hours.

The next time someone asks what you do you can honestly tell him or her that you are a TEST PILOT.

:sad: But true.

[Bladestrike]

For someone flying S61's offshore with no end in sight, I'm all for the ten year rule! The fact is, it gets the job done and cheaply. Pretty reliable as well!

[Steve76]

...76A++.....I wish!!
We are still flying the A model. Reliable as a $2 dollar watch. It lets you down at the worst of times.
Still like Bladestrike says...cheap and does the trick.

[Lu Zuckerman]

One dark night outside a small town, a fire started inside the local chemical plant and in a blink it exploded into flames.

The alarm went out to the fire departments from miles around.

When the volunteer fire fighters appeared on the scene, the chemical company president rushed to the fire chief and said, "All of our secret formulas are in the vault in the center of the plant. They must be saved. I will give $50, 000 to the fire department that brings them out intact.

But the roaring flames held the firefighters off.

Soon more fire departments had to be called in as the situation became desperate. As the firemen arrived, the president shouted out that the offer was now $100, 000 to the fire department who could bring out the company's secret files.

From the distance, a lone siren was heard as another fire truck came into sight. It was the nearby rural township volunteer fire company composed entirely of men over the age of 65.

To everyone's amazement, the little run-down fire engine passed all the newer sleek engines parked outside the plant. . . . . and drove straight into the middle of the inferno. Outside the other firemen watched as the old timers jumped off and began to fight the fire with a performance and effort never seen before. Within a short time, the old timers had extinguished the fire and saved the secret formulas.

The grateful chemical company president joyfully announced that for such a superhuman feat he was upping the reward to $200, 000, and walked over to personally thank each of the brave, though elderly, fire fighters. The local TV news reporters rushed in after capturing the event on film asking, "What are you going to do with all that money ?"

"Well, " said the 70-year-old fire chief, "the first thing we are going to do is fix the brakes on that f@@@@@g truck! "


:E

[Barannfin]

hehehe:} thats a good one.

As for my contribution, I would say that the maint. standards and such are there for safety, not just the hell of it. Theres no reason why a 20 yr old aircraft would be less safe than a 5 year old one. As long as maint. is good.

Actually now that i say that, I would still rather fly the 5 year old one offshore. ;)

[imabell]

i own an aircraft that has its 38th birthday this year and i bet any one of you that saw it and had a fly would love to own it.

it does about 500 hours a year and has not had a day down from unscheduled maintenance in the thirteen years i have had it.

and it's used for training.

i'll post a pic.

[peter manktelow]

Hey Lu...at least your firemen were still allowed to fly ..I mean drive their truck after 65......

...or am I on the wrong thread here !!!!!!????????

:8