INTRODUCTION OF AIRCRAFT STRUCTURAL REPAIR TECHNIQUES FOR MECHANICS BY AN ENGINEER. This Blog’s target audience is A&P sheet metal mechanics and new structural engineers. Feel free to comment or ask questions.
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Posts will be on Mondays containing technical, quotes, and stories. The technical will be excerpts from my book or by request, quotes will be from several humor and historical sources, my personal stories, and some marketing I’m a capitalist).
I’ve decided to present my new book by way of online classes. Each chapter will be a class segment. Each module will be available online for a fee. This seems to be the future but it does allow me to teach a chapter at a time with no travel costs or hassles. There will be interaction by in class work and email. Access to me will also be available. Need feedback, what say you?
Continuing with my first introduction into American business being McDonald’s where I learned the importance of processes and pro-activeness. Their process took an idiot like me and within hours taught me to cook 36 hamburgers, prep the buns, cook 10 quarter pounders all at the same time and I remember being intimidated by the “old” cooks that were a year younger than me.
The proactive night manager at a particular time stood at the front door night after night then turn to us and softly yell “3 sets.” We would lay 36 burgers down on the grill with no customers in sight. Three minutes later the head lights showed up outside and as the burgers come off the grill people piled into the store. The night manager had called the local movie theater and asked for when the movies would let out. Then he watched as they went to there cars and softly yell “3 sets” That was pro-active management.
While at NWA, Rich and I tried introducing a proactive maintenance. Everything was good except for upper management. They were in that blame and CYA game.
Recently while in Charleston on the 787 the lack of pro active management was one of the worse I’ve ever seen. My manager didn’t even plan for the next hour. He was into that blame and CYA game too. There will be many funny stories from those assignments but back to technical.
So more about wording.
“Engineering always buys it off’” is a phrase I used to hear in production quite a lot because it used to be true. In fact it was called S&FA or what I liked best UAI short for Use As Is. So for us to accept the discrepancy as is was a normal thing. It was drilled into me that Engineering is not inspection nor police. If nothing needs to be done then UAI is the best repair for quality, cost, and schedule. There is no place for emotion in our disposition by placing punitive action in it. The only time we “policed” something was when we saw it concerned safety of flight.
Today UAI is frowned upon and the engineer in the shop is instructed to police and inspect the area he visits. A UAI as thought of as you are not doing your job and you can’t use that term anymore. It must be something like “Structurally and Functionally acceptable because …” but don’t use it too often or your peers may think evil thoughts about you. Today the emphasis is on never being wrong and it is worth repeating “never being wrong” so scrap is now the preferred disposition or find someone else to take responsibility. And if I’m right, why have the needless overhead. Or at least decrease the staff to a level that can just support very expensive parts, many many man hours, or significant schedule impact when a good engineer is really needed. Keeping a full staff costs too much money. I heard it cost $2000 to process a discrepancy through the system but if the part is only worth $600 why ask an engineer to scrap it? Because they are available and why would Quality take responsibility if there is someone else to take it. Post production operations may not even have an engineer on staff but use the OEM or a Consulting DER (like myself.) We are expensive when used but only when used. I consider myself like a plumber or fireman waiting for the call.
I attended a Boeing 787 Engineering repair symposium back in the Spring of 2010 and was amazed at the inexperience and lack of knowledge of their technical staff group (the OEM DERs and Stress). Imagine being two years late on certification and just realizing it might be a good idea to have some data on bad holes in composite structure. What did they think? Every hole would be perfect? And that brings up the “remove and replace” disposition. Call the fireman and he comes to the fire without a hose or any water. He turns to you and says, “remove and replace.” And reminds me when Rockwell Intl Tulsa on the B-1B didn’t order one over-size Hilok pin because they weren’t listed on any drawing. They called the plumber and he didn’t even bring his toolbox. But that was Procurement’s error like the one on the C-5B where they only ordered shear pins (no tension pins) because the were cheaper (but weaker!) Hmm. Plumber didn’t bring the right washers. I personally have gone through quite a few plumbers trying to get my office drain and HVAC installed and then fixed.
I guess I’m a little sarcastic because the 757 was state of the art and “it has never been done before” about fatigue techniques. I remember a “remove and replace” disposition because of a bad hole and lack of data to support a repair. But only once and the B757 made delivery on time.
The other amazing thing was the attitude that every discovery 787 Engineering made was thought to be the first time the world ever knew about it. It was emphasized that accepting damage might be the best way to approach the repair. In other words, UAI was being pushed as a NEW idea. And this is because the ‘required’ repairs were not going as well as advertised. And don’t think the process changed over night, it was taking years. And this is usual on any new project run by technocrats that the don’t know everything and that the troops turn on the dime.
Back in the last century pre-AF-1 arrived in Wichita into the new AF-1 hangar to be jacked up for the modification work. AF-1 hangar is down the tarmac from the 747 mod line where one after another 747s were being overhauled and modified from passenger to freighter which also required jacking the aircraft.
The local Staff Engineers along with Liaison Engineers began the passenger to freighter program coordinating with Seattle’s jacking expert engineer. The responsibility went from Seattle to Staff to Liaison and then to Operations management. The process was streamlined with increased experience on every aircraft. It took minutes to safely jack a 747.
Back to AF-1′s jacking experience where a Design Engineer (a non hands on engineer concentrating on the design) with no jacking experience was put in charge. The shop crew were all new to the 747 model being new hires or from the KC-135 military program. Well, I’m not going to tell you what exactly happened but that Designer was gone and the “experts” from the 747 mod line were brought in to finish the jacking operation and handle the “damage.” And like usual the designer got the credit and Liaison wasn’t even mentioned. Did you know they did the same thing on Unit 2 (there are two AF-1s) and I was brought down again. Sometimes it easy to look good but I knew they were a quite few of us capable of doing what I did.
Do you notice how I float around but it is hard not to tell the whole story straight through. Back to that 787 symposium on maybe we shouldn’t fix what isn’t broke or leave well enough alone (I guess those sayings are new too). The other amazing thing was how it is important that you know what you are fixing. Amazing. In other words, know where you are and what the configuration of the design and damage is. On metal airplanes we like to know what the material, thicknesses, shape, etc. This symposium thought they “discovered” this idea of knowing the material, thicknesses, oops I mean layers, shape, etc. You see they were so quick to repair and assume they were state of the art they didn’t notice there was nothing wrong. That’s not a joke or hype. I mean they had a gouge two layers deep in a 12 layer panel that only required 9 layers. So having 10 good layers is better than 9 good layers last I remember. But geese the computer template said the panel was 10 layers so they thought there were only 8 good layers. But this was a huge announcement at the symposium, “know what the damage is!” I nearly fell over.
This particular repair is called a scarf repair and I was told repeatedly this was a first ever. I replied I did my first one on the Shuttle Atlantis payload doors in 1982 but we called it an overlay ply repair. I showed them the Dash 8 SRMs overlay ply repair from the late 80′s. This ain’t new, its kind of old school. Basically it is the same as fiberglass overlay ply repairs of the 50′s ( I was being born) except one uses new materials. I was very surprised nothing changed not even the step back on each repair ply.
While consulting at NWA a decade ago, I was a novice to airline processes but not to common sense and the aircraft repair. Being from Wichita at the time and working in Detroit, I planned Thanksgiving in Detroit because that Wednesday before is supposedly the busiest day of the year for the airlines. But what did I know about the airlines. So with my family traveling to Detroit, we settled down to dinner. It was quiet then but not that previous evening. I started getting phone calls from all over the planet about damaged NWA aircraft but I was assigned only to Detroit. Long story short, I was the only engineer NWA working that evening with all the NWA engineers leaving early that day. But like I said what did I know about the airlines. The next year the engineers had to be on duty for the holidays.
[But the caveat is they didn't have to be at their desk. So they answered their mobile phone and said. "replace the part." And this time I did hype it up a bit but the point is engineers do have lives and no one can really question them except another engineer.]
Summing this up, nothing is new only different with new people and tools. And because engineering says “remove and replace it” does not mean the part is no good so get a second opinion when cost / schedule justified. Most parts can be saved, it is just a matter of money or time, but those two things shouldn’t be left up to the engineer because it may be easier and quicker for him to save the part than for you to replace a part.
Next week, “you only need 9 out of ten rivets”
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Why do we wash bath towels? Aren’t we clean when we use them?
Words of Wisdom and Warning
“I have but one lamp by which my feet are guided, and that is the lamp of experience. I
know of no way of judging the future but by the past.” Patrick Henry
Aged to perfection
The longer we live the more we learn it is not who has the most – it is who makes the most of what he has.
Y’all, DERs do take questions and are on the same team. Most DERs are comfortable in their role and don’t mind giving a few minutes of free advice to other aviation professionals.
Sincerely,
James W. Callahan
General Manager / FAA DER
DER@CALLAHAN.AERO
256-891-3677
P.O. BOX 533
Albertville, AL 35950
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Without any other differences the allowable for bearing in metal sheets drops the closer to the edge of the part. There is a direct relationship between the allowable and the load carrying capability of the fastener.
