In the "engineering marvel" thread ( viewtopic.php?f=2&t=163563 ), a common theme was raised again about the lack of durability of the Cirrus compared to, e.g., the Bonanza.



We see this claim made here on BeechTalk on a regular basis. I wonder just what components of a Cirrus will deteriorate and become unairworthy as the years go by.

So, engineers, in your opinion is it the composite material of the body itself? (Other than that, it seems the windows, engines, avionics, cables.....the "guts" of all these airplane types are pretty similar.) Is the theory that the composite body structures will fall apart or disintegrate? Is there evidence of that happening?

The oldest Cirrus planes are 20 years old now. My 310 will be 55 years old next month.

Some of these same claims were made about fiberglass in the 60's when glass boats were introduced into the marketplace and sailplanes as well.

I know several different types of sailplanes from the 60's and early 70's still flying today with little if any sign of deterioration.

I know a lot of un-maintained aluminum airframes that are unworthy due to corrosion and will never fly again.

I think the concern is that there's no simple way to verify the integrity of composite structures. If there's a delamination or other flaw, it's hidden inside. To detect internal flaws, you have to use Ultrasonic Testing, an expensive and time-consuming process. With aluminum, you can visually see cracks, etc.

Yes, they'll be here in 50yrs.

Advanced composites design and implementation have been around a longer time than Cirrus has.

Composite repairs take a different kind of skills, not unlike a guy like Del Lehmann getting a 60yr old Bonanza cowling reskinned and shaped to fit like it used to.

Keeping any aircraft in the air for 50 years means the plane was cared for, and got the costly maintenance performed in a timely manner.

Aluminum has a greater likelyhood of corroding than an autoclave bonded graphite wing has of delaminating or having an age related disbonding of the plies.

Interesting question. My suspicion is that it will have to do with damage repair.

Cirrus will not have any attrition due to gear mishaps, but they will have chute repack costs "forever".

Therefore, interesting comparisons would be:

1) hard nosewheel incident repair costs of a 182 vs a Cirrus.

2) hangar rash repair costs

Regarding chute costs: outside of aviation, a recurring cost like this would invite competition and help control the price. Aviaiton seems to foster the opposite.

Cirrus people: have chute costs gone up, down, or been steady?

I know, I know, the per hour cost of a repack is nothing. The reality is that many people don't accrue, they pay the expense as it happens.

One more thought: eletrical wire chafe and subsequent development. I don't know enough about the guts and wiring in a Cirrus. Any appreciable difference to an Aluminum airplane when both are 50-60 years old?

Thanks, Donald. So it appears you feel the Cirrus life expectancy will meet or exceed that of similar aluminum airplanes. I am not sure and I appreciate yor reply.

On the electrical comment. I think it is safe to assume there will be chafe/short issues in old Cirri. Perhaps at a rate much lower than similarly aged aluminum airplanes. My question was more along the lines of "when a short occurs, is the result the same in either type of airframe?"

Alot of chafed wire short circuits occur when an improperly supported wire chafes against the airframe, when that occurs on an aluminum airplane sparks/smoke/fire occur, on a composite airframe that doesn't happen. Composite is not conductive.

But, there are many more wires in a composite airplane, because the airframe is not a ground, so every component has a ground wire returning the current to a ground buss.

I admit that I've never seen or performed any Cirrus maintenance. I cannot speak with any authority about Cirrus, but can reasonably assume that their composite designs are similar to the one's I am quite familiar with creating repair instructions for.

One of the nice things about composites is that the tools needed are much cheaper than sheetmetal. A good vacuum bagging and hot box setup cost the same a a 52" foot shear for aluminum work. Once you've got those tools and the knowledge, any typical composite repair is pretty easy and undetectable after final paint applications. Many sheetmetal repairs require internal flush patches and a lot of skilled work to appear similarly undetectable. There are also plenty of damaged composite parts that are better suited to being replaced entirely, requiring a good OEM with spares. An orphaned design (Piaggio, Starship, etc) will be an enormous labor of love and eye wateringly expensive to re-fabricate airframe parts for.

I don't see how the wiring is any more or less prone to chafing than a sheetmetal aircraft, but certain wiring runs will be inside a thinwall plastic conduit, making replacement wiring runs arguably easier. Also, since Cirrus does not have any gear systems, most wiring is associated with avionics and autopilots rather that aircraft systems.

I bet changing plexiglass windscreens, repainting, and Major aircraft repairs will be where the costs of a composite design exceed the similar costs of a sheetmetal design. Anytime a hangar door chops the fuselage in two, you're going to need the factory autoclave and tooling to make airframe repairs, and the added weight may become another real concern that makes it cost prohibitive. I also highly doubt you will see composite aircraft "restored" to the level that many historic sheetmetal, tube and fabric, or other design gets taken apart to the individual component and reassembled.

What does it take to replace a window on a Cirrus? What about an aileron bearing on the bonded in ones? Honest questions wondering how these PM costs compare when trying to maintain a 20 plus year old Cirrus versus an aluminum airframe of similar vintage. Will these types of costs eventually make a cirrus uneconomical to repair in 50years when the repair becomes a significant percentage of the hull value or will it be similar to aluminum just different techniques?




Jeff

The Aloha Airlines Flight 243 incident was caused by the failure to see cracks in the lap joint by visual inspection and after the incident ultrasonic testing was required.

Vince

I think the structure will be fine, *IF* the planes are hangared. Ultraviolet rays will eventually break down the planes that sit outside.

I think the greatest threat to longevity for recently produced airplanes is avionics.

50 years from now, I don't think you will be able to maintain a G1000.

But an older airplane which originally came with steam gauges will be just fine, even if it has had after market glass, due to the lack of integration and ability to upgrade in steps as the tech improves.

Airplanes today have entered the age of planned obsolescence due primarily to the highly integrated electronics.

This is not a plastic versus metal problem.

Mike C.

I suppose that's true regardless of what the plane is made of. The aluminum planes that have been sitting outside for a few years at my airport are definitely not airworthy. I've never seen a Cirrus that lives outside, although I assume there must be some...

This is not an engineering problem, though. It's totally man made, and can be erased with a rules change.

All modern avionics should be designed to be easily upgraded or replaced in ten years, because technology will march forward.

I agree wholeheartedly. It is not a composites issue. It's how the fleets are treated in their respective lifetimes. Any plane certificated with a specific avionics package will get difficult to upgrade in a cost effective manner.

Likewise, the DA-20's and SR-20's used in flight school training are rode hard and I would expect to be retired from service due to costs as well.