Long Term Recommendations For ICS Based on Aging Aircraft Conference
18 April 2006
Introduction
After the Aloha Airlines incident in the 1990’s, Congress authorized NASA and the FAA to investigate the effects of aircraft aging on airworthiness. This work concentrates on Part 25 airplanes. The GA fleet is on their own. At the Aging Conference, the FAA recognizes that the Type Clubs are the knowledge base for the older airplanes, and will, in the future, allow greater participation in managing our own destiny.
Marv Nuss of the Kansas City Directorate is the key person for aging aircraft issues and policy. At the end of the meeting, he summarized his view on the direction Type Clubs should follow. These are discussed below, and one additional item I feel ICS must undertake.
1. Triage The Fleet
ICS needs to determine the current state of our fleet. How many hours? How many engines overhauled? How many times painted? How many times geared-up? What type of problems are the members having? Etc.
As you can imagine, the survey needs to be specific, reasonably short, and encompass current and potential future problems. I will create a “straw man” survey, and pass it around for improvement. It should be published in the Flyer, along with a ‘fire and brimstone’ message about its timely completion and return.
The survey needs to be designed in such a way that the data can be easily scanned or transcribed into a database. The computer literate can help out here.
2. Develop a Fatigue Management Plan
Comanche airplanes are known to be tough and strong. CAR 3 airplanes did not have a requirement to perform a fatigue analysis prior to certification. Will we have a problem in the future? Back in 1991, I got a copy of the FAA’s fatigue analysis software, and ran my twin through the numbers. When doing the evaluation by analysis only, divide the resultant fatigue life hours by 8. When doing it by test, divide the demonstrated fatigue life by 4. The number I came up with was not totally encouraging.
I asked for, and received, the latest copy of that software during the Conference. I propose an analysis be performed on each model of airplane. Given the different models, with different gross weights, with and without tip tanks and alterations via STC, I would speculate that at least 15 variations exist. To accomplish this analysis, someone needs to take the action, that for each model variation, measurement of the spar cross section at the fuselage junction be done very accurately. With that data, I can determine the FAA’s predicted life span.
Once an airplane reaches the predicted number of hours, then an ICS developed inspection plan comes into play. That plan is yet to be formulated. In addition, that plan may well include other areas of inspection we believe are potential fatigue problem areas. I will create a cross section drawing with blanks for the dimensions, with someone taking the lead in getting the information using calipers, micrometers, etc. We need volunteers to make this happen.
3. Corrosion Management Plan
Everyone knows about the torque tube corrosion problem. We have a Mandatory Service Letter from Piper. In spite of this, I suspect that many Comanche owners still have not done the inspection. The only way to put teeth in that Letter is by AD, and that is something ICS would not like to see. So, how do we, as an organization (primarily social per some pundits), get the message to these owners, ICS or not?
Part of the survey will focus on corrosion, and will try to get some answers. One area that is still a problem is that the corrosion resistant bolts are still corroding! I think the key work is ‘resistant’. A true mitigating solution is to use NAS 654V32 (singles) and NAS 655V32 (twins) Titanium bolts. I’ve been trying to locate a source with reasonable prices. Maybe someone else could take up this cause.
In addition to the torque tube, are there other areas of potential corrosion? Engine mounts? Fuel senders? Battery box? Fuel selectors? I have some photos of a twin sent to me by a European member that sat in the water a little too long. It looks pretty ugly.
We need to predict other areas of possible corrosion, and find ways of dealing with it. As the spare parts run out, then approved repairs will be necessary. For example, there is no approved repair on the torque tube. This Corrosion Management Plan needs to be developed quickly.
4. Structural Repair Manual
All we have for our Comanche’s is a Parts Manual and a Service Manual. There is no approved SRM. This could be a monumental task. But, the idea is that ICS develop a uniform set of repairs that become approved data for use by the members. This would bypass getting the approval by the local FSDO. At the conference, the FAA was receptive. How this is going to be implemented is and was unclear. I will contact Marv Nuss and see if there is any guidance in this matter.
Right now, if someone does a gear up, the typical mechanic must get approval for all aspects of the repair, including fabricating replacement pieces of damaged structural elements (ribs, formers, shear webs, etc.). Even a repair station is required to get FSDO approval.
I think that we have a good start with the Tips, and technical articles in the Flyer, such as Karl’s discourse on boost pumps. Charlie Tripp has the information on the scavenge pump problem. The information is out there, but needs to be carefully documented. I prefer a standardized format. Again, someone needs to delegated to take charge of this opportunity.
Summary
If we intend to keep our airplanes flying for a long time, then ICS must do the necessary groundwork now. By investing time and money on these important issues, we will be maintaining the fleet with the FAA’s blessing, demonstrating worthwhile efforts to the insurance carriers, and retaining high value to potential buyers.
Hans Neubert ICS 7685