Increase in maintenace interval frequency?
 

You hear a lot about maintenance interval escalation where the maintenance task frequency is reduced based on sufficient operational feedback.

But what about increases in the maintenance interval frequency? I suppose this would mean that relevant MSG-3 analysis is incorrect rather than conservative which is the typical case for escalation.

Does anyone know of any examples where airline findings have led to increases in the maintenance interval frequency and so the revision of the MSG-3 analysis?

The 15-year old 737-300 Southwest Airlines Flights 2294 and 812 fatigue-induced fuselage skin rip decompressions and subsequent AD springs to mind. However, what I'm after is whether anyone knows of any cases of proactive reporting of findings from airlines that supported an increase in the maintenance interval frequency.

It seems that we're quite saturated by hearing of things happening the other way around i.e. escalation or reactively via ADs after an incident/accident.

Absolutely. CPCP (corrosion Prevention Program) is a prime example. Operators must monitor corrosion findings, and ensure that findings are limited to Level 1 or better. Level 2 corrosion findings necessitate action, which can be either improvements in the protection, changes to the operation, training of staff, or even decrease of the inspection interval.
The CPCP philosophy is that whist everyone starts from the same baseline, there are many factors unique to each operator, such as operating environment (weather), choice of corrosion prevention compounds, skills and quality of the maintenance facilities, cargo types, etc, etc, that can all add up to corrosion being a problem in some areas for some, and not for others.


Another area of maintenance commonly subject to in house de-escalation regards component maintenance. Component reliability is measured, and if a trend is detected, then the inspection/overhaul interval is brought down to try to reduce the number of incidences of on wing failure.

Airlines also share information with OEM's, NAA's and each other. Whilst some parts of our maintenance programmes are closely guarded secrets, most of the big airlines share new, uncommon, or disturbing maintenance findings. The OEM's track findings and recommend changes to the operators, either by changing the MPD, or by issuing service bulletins. Where those Service Bulletins affect safety, the NAA's pick them up and mandate them with AD's.


The big public decompression incidents are primarily fatigue related. Fatigue affects all operators, where it exists in one airframe of a certain age, it is likely to be in other airframes of similar age, hence these issues become AD's, and public knowledge.
But in the background, there are people at every airline who are paid to fine tune the maintenance program to strike the right balance of reliability through product improvements, modifications, trend monitoring and task interval escalation and de-escalation.

Thanks for your comprehensive reply GroundedSpanner, goes to show how much happens in the background and yet you only get to hear about the stuff that makes for "easy" news.

Venturing off topic:

On the other hand, the role of the Maintenance Planning Engineer today seems to be advertised under more of an administrative guise rather than the analytical, optimisation scope that can improve aircraft availability and hence profits.

This in turn may lead to talent moving away from this field. We already hear about shortages of licensed engineers yet it is this experience that you want to capture in such positions that I personally view as managerial in terms of scope. The reason I consider maintnenance planning optimisation work to be managerial in scope is due to the extent of analytical skills that involve knowledge of the entire aircraft and its operation while following advancements in tools, methods, technology and of course safety findings and using all this information to be proactive or predictive rather than reactive. This is especially true for e-enabled aircraft that will eventually become the norm as they offer game-changing potential for maintenance programme optimisation and hence ways of making an airline improve its profitability.

a1rm4n
 

With regards the fatigue inspection for the SWA B737 and other fatigue inspections covering other a/c types, they do not come from MSG-3 analysis. :ok: