How Can Planes Stay In Service For So Long?

[Jelly]

For example:

This DC-9 was built in 1966 (Yes, that's right, 1966!) and is still flying today!

Picture from mid-70's:

Picture from this past summer ('04):

 

[brianl703]

My understanding is that the maintenance schedules for airplanes specify when each part is supposed to be replaced, and it gets replaced, whether it's good or it's bad, at the specified interval.

 

[Steve S]

the AP guys can post why, but they are maintained and driven carefully.

.They run Mobil oil.

 

[MolaKule]

Here is the way its done in a nutshell:

When designing an aircraft structure, the analysis job of how long these parts can stay in service goes to the Stress and Fatigue Analysis team.

Step one is determining if each individual part can withstand the stresses encountered in the many cycles of aircraft operation. A cycle is takeoff, cruise, and landing. Also taken into consideration is gusting, emergency procedures (tight turns or dives for aircraft avoidance, hard landings, etc).

Once each part is analyzed and tested for maximum stresses, it is then passed on to the Fatigue group.

The fatigue group then determines how many cycles of stress each part can withstand over the projected lifetime of the structure. Not only do the calculations enter into project life of the structure, but airframe database history also goes into the final projections.

Lifecycle determinations are then given to the tech writers who write up the service manuals.

Thus, each part on the aircraft structure has a lifetime and must be replaced when it approaches the end of its life.

Special tech bulletins are issued for any part, subsystem, or system which has shown failures short of the projected lifetime, and their causes are thoroughly investigated.

 

[andrews]

Aircraft are designed to last many "cycles"....that means a take off and a landing. Some aircraft can last fifty to eighty thousand cycles, if properly cared for. Engines, rivets, struts, interiors and nearly all other areas of an aircraft are replaced or inspected according to very strict guidelines. Some aircraft in use are over 70 years old and they are still very safe. What it comes down to in the end is if the added expense of keeping an aircraft airworthy is worth the cost. Most airlines prefer to purchase newer more fuel efficient models as opposed to keeping really old ones flying.

 

[Matt89]

If it was financially worth it, you could keep your car on the road just as long by replacing each and every part as it went bad.

If parts remained economically available, it would be cheaper to bionically replace everything on your car (incl. engine, tranx, sheet metal) over 30 years than to buy 2 or 3 new ones. Of course that would be tough sell for most people!

 

[MolaKule]

Don't we call those people, "Classic Car Enthusiasts?"

[ November 10, 2004, 05:53 PM: Message edited by: MolaKule ]

 

[MolaKule]

To go back even further, DC-3's, B-52's, DC8's, and 707's are still flying.

 

[novadude]

quote:

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If it was financially worth it, you could keep your car on the road just as long by replacing each and every part as it went bad.

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Funny... up until last summer, my Mom's daily driver was a '69 Chevelle with 26x,000 miles on the clock. Replacing each and every part as it went bad was pretty much what my Dad and I did for the 20 years she drove the car (suspension, engine, transmission, etc.). While the car was in great shape, very few mechanical parts were original.

 

[XS650]

Good design, good manufacturing processes and good maintenance. Also upgrades as needed to correct problems that are discovered during the aircraft types life.


The US miltary has aircraft that have been in service longer than that. The last B-52 was built in 1962. They are expected to be in service until 2040. 78 years!

I believe the C-130E is still in service. They were new when I was in the AF in the early 1960s. Don't know if the early E models are still flying or not.

If you want to find out more about a particular aircraft, Google the aircrafts tail number ( N8914E in your case) and select the first option "Look up aircraft with registration number"

 

[moribundman]

An older airplane is like Cher. Parts range from "ancient" to "brand-spanking" new. Birthdays may occur on a daily basis.

 

[XS650]

quote:

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Originally posted by MolaKule:
To go back even further, DC-3's, B-52's, DC8's, and 707's are still flying.

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A few Ford Tri-Motors were still in service in South America about 15 years ago. They are late 1920s vintage.

Less than two years ago, a flight was offfered from Burbank to Auburn California on a Ford Tri-Motor, about 350 miles. Sorta like passenger service

. If I had been home I would have taken it.

 

[TR3-2001SE]

An older airplane is like Cher. Parts range from "ancient" to "brand-spanking" new. Birthdays may occur on a daily basis.

 

[Al]

quote:

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Originally posted by moribundman:
An older airplane is like Cher.

---

Well used cher

 

[JHZR2]

I guess you could ask why do highway mileage cars last so long, particularly down south... Why do over the road trucks last so long?
Why do toyotas last so long?

For the first two, its because of the more or less steady state operation, long term, in a warmed up state. For the third, its because of a rigorous maintenance schedule, which if taken to the dealer, will have you spending probably a thousand dollars a year for preventative maintenance.

I think the same things are the reasons why planes last so long. Theyre overdesigned to begin with.

JMH

 

[tom slick]

one of the reasons airplanes last so long is because the aren't built out of cheesy parts like cars are. they are extremely engineered and are overbuilt compared to autos.
maintance is another issue. their airframe is inspected for corrosion very often. their engines are replaced regularly. imagine inspecting your car every year by inspecting and testing every single system in it. it could last forever too.

c-130E's are still in service, i used to work on the oldest in the USAF fleet. they were 1961 and 1962 models. we still fly them all over the world and on fire fighting missions during the summer. the c-130 is still being produced today. only the VW beetle had a longer production run.

 

[snoboy]

To add a little to Mola's statement regarding cycles. A cycle also consists of a 1 pressurization and 1 depressurization. Whats that mean: It means the fuselage gets blown up like a ballon and then deflated. That puts all the skin fasteners in shear and or tension every flight.
We do high blows and low blows on every plane that comes down the line. Sitting in the factory at 19' ASL when the plane is pressurized the skin is visually swollen between the stringers and ribs. At 30,000 feet there's even less outside pressure on the skin.
I'm still amazed that they last as long as they do.

 

[moribundman]

I've always wondered how much a (pressurized) fuselage expands at high altitude. Are we talking about fractions of a mm or more than that? Also, isn't expansion/low ambient pressure the reason for the SR-71's "leaking" fuel tanks? Couldn't they have used bladder tanks instead?

 

[HunterG69]

I don't know about fixed wing too much but a helicopter for instance can be built from the data plate alone. You have a data plate you can have a helicopter.

On the pressurisation thing - some A/C can go longer than others, one of the reasons you see so many Convair 540's around.

 

[MNgopher]

Intersesting that you posted the DC-9 picture from Northwest. They are headquartered here and have one of their major hubs here, so of course we get all sorts of stories about them.

The DC-9s were a story several years ago. New noise regulations were coming into effect, and Northwest had to make a decision to spend a lot of money retrofitting every DC-9 with a hush kit, plus face the costs of maintaining an aging fleet or purchase new planes. Based on their analysis, customer input (passengers still liked flying on the DC-9), etc..., Northwest chose to continue flying the DC-9's rather than investing in new planes such as the 737 or Airbus A319's.

Forward years after making the decision, and the results have been interesting. Northwest's fleet is one of the oldest in the air, yet among the fleet, which planes have the highest reliability record? You guessed it, the old DC-9. Essentially, the DC-9 is plenty over designed and lasts one heck of a long time!

Even more interesting, it put Northwest in a unique postion after September 11th. Since it basically owned the majority of its fleet outright, it could park planes, and not have to make payments on them. Other airlines with newer fleets haven't been as lucky, and got stuck making payements on many planes that got parked. It has left NW in a slightly better financial situation versus its competitors.

Rumblings are in the works to replace the DC-9's eventually. NW has picked up quite a few A319's that seem to work well.