Life Limits

[misamajoco]

Do Mooney aircraft have life limits?  For example, the F-18 was designed with a life expectancy of XX hours, however there is are service life extension programs to get them an additional XX hours of service life.  Does the same apply to GA aircraft, specifically Mooney’s?  Yes, I understand Mooney’s are not flown as aggressively as a Hornet and there is not as much stress being induced on the airframe.  However, there are a number of Mooney aircraft that are 50+ years old and I have seen some airframes advertised with as much as 7000+ hours on them which leads me to this question.  Obviously corrosion would have an affect on the life of these aircraft, but is there a requirement to look for cracks or fatigue indicators on an airframe that has more than 5000, 6000 or 7000 hours on it?

[Guest]

26 minutes ago, misamajoco said:

Do Mooney aircraft have life limits?  For example, the F-18 was designed with a life expectancy of XX hours, however there is are service life extension programs to get them an additional XX hours of service life.  Does the same apply to GA aircraft, specifically Mooney’s?  Yes, I understand Mooney’s are not flown as aggressively as a Hornet and there is not as much stress being induced on the airframe.  However, there are a number of Mooney aircraft that are 50+ years old and I have seen some airframes advertised with as much as 7000+ hours on them which leads me to this question.  Obviously corrosion would have an affect on the life of these aircraft, but is there a requirement to look for cracks or fatigue indicators on an airframe that has more than 5000, 6000 or 7000 hours on it?

There is no regulated(type certificate) life limit on the airframe, engine or propeller.  Some Mooney airframes have had component life limits shown in Chapter 4 of the maintenance manual, others have been removed.

Clarence

[ChrisV]

Not an answer here, but something I find interesting... the King Airs (A200s) that my company uses were originally approved to 23,000 hours.  With additional inspections, Beech cleared them to 30,000.  At 30,000 Beech, flat out said NO MORE.  They returned stateside with less than 100 hours to spare and the owners said they were going to use them for training right up to 30K hours.

[Hank]

10 minutes ago, M20Doc said:

There is no regulated(type certificate) life limit on the airframe, engine or propeller.  Some Mooney airframes have had component life limits shown in Chapter 4 of the maintenance manual, others have been removed.

There are, however, things you can do to / with a Mooney that will limit your own life . . . .

[flyer338]

Last year when I was shopping, I saw a J for sale with more than 12,000 hours and three gear-up landings.

[cbarry]

I’ve never read there being an airframe hour limitation on a Mooney.  Hours, in my opinion, are similar to miles on an automobile’s odometer.  There are some driver’s cars I wouldn’t buy even if they had put only 25,000 miles on since new and then there are the driver’s that take care of their stuff.  

[jlunseth]

I learned a little bit about this, this past week, flying in an Extra 300XL fleet.  The aircraft has a certified life limit of 6,000 hours. Now, that is for commercial use, private owners are said to fly them for longer.  Some aircraft, like the old DeHaviland Otters and Beavers, have a certified limit of 10,000, but at the end of that they go through an airframe overhaul and get recertified.  That does not happen with the Extra.  The wing is carbon fiber and would have to be completely rebuilt/replaced.  The cost of that is high enough that the owner might just as well get a new aircraft.

The Mooney does not have a certified life limit that I know of.

[kortopates]

The only GA airframe that I am aware of with a life limit is the Cirrus SR20 & SR22 airframes with a 12,000 hr life limit. Probably more to do with it being certified under Part 23 than anything else. 

[Jerry 5TJ]

Piper PA46 airframes and wings have life limits. 

[rbridges]

48 minutes ago, kortopates said:

The only GA airframe that I am aware of with a life limit is the Cirrus SR20 & SR22 airframes with a 12,000 hr life limit. Probably more to do with it being certified under Part 23 than anything else. 

Some of the commanders have life limits, but it may be the wings (?).  

[skydvrboy]

I find this topic interesting, simply because everyone wants a airplane with low hours that has been flown regularly.  That just isn't going to happen as planes age.  Either they are going to have high total time or they are going to have long periods where they sat idle.

I won't speak for everyone, but I would feel much safer flying a 50 year old plane with 10,000 hrs TTAF flown 200 hrs a year than a "barn find" with only 1000 hrs TTAF and fresh annual.

[GeeBee]

2 hours ago, kortopates said:

The only GA airframe that I am aware of with a life limit is the Cirrus SR20 & SR22 airframes with a 12,000 hr life limit. Probably more to do with it being certified under Part 23 than anything else. 

How does Part 23 certification figure into that fact?

 

[Guest]

Piper PA44 Seminole has wing life limits from the type certificate, as an example.

Clarence

The below life limits are based on general aircraft usage for this aircraft class: a) PA-44-180
For S/N 44-7995001 through 44-8195026
The service life of the wing, wing carry through and their attaching structure has been established as 14663 hours maximum.
For S/N 4495001 through 4495013, and 4496001 and up
The service life of the wing, wing carry through and their attaching structure has been established as 14663 hours maximum.
b) PA-44-180T
For S/N 44-8107001 through 44-8207020
The service life of the wing, wing carry through and their attaching structure has been established as 14663 hours maximum.

[carusoam]

Composite materials have a wear factor that is much different than aluminum and rivets...

Rivets are easy to tell if they have lost their strength... the sheet metal doesn’t change in relation to time...

Composites can lose a percentage of the bond between the fibers and the matrix...

Under normal category flying... things aren’t getting stretched that much...

Many Mooneys that flew traffic watch also saw hours over 10k...

A plane with 10k hours on it has probably seen a lot of wear parts replaced...

PP thoughts only, not a mechanic...

Best regards,

-a-

[Yetti]

You say these airframes are not being stressed.  Have you seen some of these people land?

[Hector]

There is no documented fatigue life limit for Mooneys. There are also some very high time Mooney’s out there with no evidence or findings of fatigue cracks in critical structure. Most of the aluminum structure is 2024-T3 which has excellent ductility and the steel tube structure is lightly stressed. The killer for Mooney’s is corrosion. If you can keep corrosion under control the airplane will outlast you.


Sent from my iPad using Tapatalk

[kortopates]

On 1/30/2020 at 10:46 AM, GeeBee said:

How does Part 23 certification figure into that fact?

 

Only because these requirements stem from Part 23.1529 Instructions for Continued Airworthiness which are required for the aircraft certification process per 21.50b - you'll find those very brief yet the FAA provided all the details under Order 8110.54A. The ICA's mandate that the airframe manufacturer address mandatory replacement times, structural inspection intervals, related structural inspection procedures ... etc. Which leads us to how Cirrus, or for that matter how any manufacturer chooses their path through the ICA requirements since Cirrus had other options besides going with the life limit as they did. To better explain, I think Cirrus would say they took the simpler path. Rather than provide elaborate inspections methods and intervals for testing their composite airframe structural integrity after several thousand hours, as some other manufacturers have done, they instead got the FAA to agree that the airframe should be fine following their normal documented maintenance and inspections for upto 12,000 hrs without requiring any special elaborate inspections - because they haven't written them yet. Further, Cirrus didn't  get FAA approval for 12,000 hrs on day one. When the SR22 airframe first got certified, the SR22 was limited to 4000+ hours but as a few years  went by Cirrus had enough data to get the FAA agree to 12000 hrs for SR22 like they had for the SR20. But assuming Cirrus is going strong as the fleet ages and they have learned more about issues of concern on higher time airframe, in theory they can always provide additional inspections for airframes near the 12,000 hours to extend their life further if practical or even convince the FAA that the life limit can be extended further without additional inspection procedures.. But it was the certification requirements for ICA's that drove them down that path that we didn't see under CAR3 with the Mooney for example.  

[ArtVandelay]

Piper PA44 Seminole has wing life limits from the type certificate, as an example.
Clarence
The below life limits are based on general aircraft usage for this aircraft class: a) PA-44-180
For S/N 44-7995001 through 44-8195026
The service life of the wing, wing carry through and their attaching structure has been established as 14663 hours maximum.
For S/N 4495001 through 4495013, and 4496001 and up
The service life of the wing, wing carry through and their attaching structure has been established as 14663 hours maximum.
PA-44-180T
For S/N 44-8107001 through 44-8207020
The service life of the wing, wing carry through and their attaching structure has been established as 14663 hours maximum.

14663! I thought they could at least 14664? ;-)
No way can they go to that level of precision, who are they kidding?


Tom

[GeeBee]

2 hours ago, kortopates said:

Only because these requirements stem from Part 23.1529 Instructions for Continued Airworthiness which are required for the aircraft certification process per 21.50b - you'll find those very brief yet the FAA provided all the details under Order 8110.54A. The ICA's mandate that the airframe manufacturer address mandatory replacement times, structural inspection intervals, related structural inspection procedures ... etc. Which leads us to how Cirrus, or for that matter how any manufacturer chooses their path through the ICA requirements since Cirrus had other options besides going with the life limit as they did. To better explain, I think Cirrus would say they took the simpler path. Rather than provide elaborate inspections methods and intervals for testing their composite airframe structural integrity after several thousand hours, as some other manufacturers have done, they instead got the FAA to agree that the airframe should be fine following their normal documented maintenance and inspections for upto 12,000 hrs without requiring any special elaborate inspections - because they haven't written them yet. Further, Cirrus didn't  get FAA approval for 12,000 hrs on day one. When the SR22 airframe first got certified, the SR22 was limited to 4000+ hours but as a few years  went by Cirrus had enough data to get the FAA agree to 12000 hrs for SR22 like they had for the SR20. But assuming Cirrus is going strong as the fleet ages and they have learned more about issues of concern on higher time airframe, in theory they can always provide additional inspections for airframes near the 12,000 hours to extend their life further if practical or even convince the FAA that the life limit can be extended further without additional inspection procedures.. But it was the certification requirements for ICA's that drove them down that path that we didn't see under CAR3 with the Mooney for example.  

I would agree 1529 sets for the requirement for ICA, however. FAR 23 nor 1529 nor FAR 23 Appendix A itself mandates a formulation of airframe life. It only requires the development of intervals of inspection and inspection procedure. The use of a life limit is generally promulgated because there is no longer a procedure which will insure airworthiness. In composites as noted above it is difficult to assess the status of the material itself. In other cases, the manufacturer has made a determination that no inspection procedure is sufficient, such as Beechcraft center sections. However it is possible that an entire airframe can be designed such that it can be entirely inspected on regular intervals and in such case, can have no airframe life limit.

[carusoam]

Interesting point GB...

For composite plane parts... the inspection technology would need to ‘see’ through the materials... to make sure the fibers are still attached to the composite’s matrix...

There are probably some weaker or more critical sections that would need this type of X-ray (?) vision...

Similar to looking for mini stretch marks that may not be showing at the surface...

PP thoughts only, not a mechanic...

Best regards,

-a-

[GeeBee]

A perfect example is the XCub. FAR 23 certification.  Life limited components in the airframe, but no life  limits on the airframe itself, because it is easily inspected and components replaced.

 

 

[tmo]

The Grumman AA5 family has life limits on / around the spar.

[GeeBee]

The AA5 has a lot of bonded aluminum. Very hard to inspect.

 

[CharlesHuddleston]

On 1/30/2020 at 8:07 PM, Yetti said:

You say these airframes are not being stressed.  Have you seen some of these people land?

Better yet, have you seen some of MY landings!!! 

[flyer338]

The Grumman Tiger has wing spar life limits of 12,000 and 12,500 hours. 
http://www.grumman.net/cgrcc/a16ea.pdf