Visit our website at www.Callahan.aero or e-mail us at der@callahan.aero for any questions or special interest.

“Misunderstanding DERs“

“We all see only that which we are trained to see.” ― Robert Anton Wilson

Stop limiting us! We DERs should ONLY work outside the manuals.  Therefore most of the time what we approve “violates” an A&P’s training, published allowable damage, “rules of thumbs”, and the manuals.  If what we approve is “per” or “in accordance with” then why are we approving it.

I may sound frustrated and that would be because I am so its time for a story.

Years ago I was sent down to Lake Charles on a Tiger team of engineers to save the day. We left Wichita at 7 AM and arrived via Boeing Corporate jet an hour later for THE meeting.  We were told the on site engineering team was scrapping everything and the KC-135 vendors have long since gone out of business.  There were no replacement parts available and aircraft re-deliveries were not happening. Lions, and tiger, and bears – OH MY! (after all we were from Kansas)

So we visited the local engineering team who were absent, as in not invited, from THE meeting and oblivious to the scrap rate. What? There’s a lack of communication? I’m shocked, shocked to find that gambling is going on in here!

So we  four engineers paired off, grabbed a few tags, went data collecting and in less than an hour we figured out what was happening. The inspectors were scrapping any damaged parts exceeding allowable damage or repair per TO and used the engineers to disposition cosmetic items like washing skin laps with soap and water so the USAF would pay for it.  No joke.

So before lunch, we figured out the problem was not engineers scrapping parts but where to have lunch. I find on most trips it is getting a group of engineers to make a decision about lunch to be the biggest problem. Now the shop had a major problem and it was ignorance or “lack of training” but that was a shop management problem so we left advising the on site engineers to get more involved.

Moral of the story is Inspection didn’t know how to use Engineering correctly and shop management hadn’t included Engineering on their team.  So if cost or schedule is an issue, Engineering may be of use.  Call us; we can say no if we can’t help.

I believe I should provide options and not necessarily the decision. One can replace or repair and the owner / manager should make the decision based on all available options.  Don’t get me wrong, I can advise or even take over but running the show is not what I am usually hired to do.  I did say usually.

We DERs do not release aircraft back into service, approve any “hands on” work, or inspect.  A DER approves data, the A&P complies with the data, and an IA releases the aircraft back into service.

Why an IA releases and not an A&P? Because DERs only work Major Repairs or Alterations but this is outside my area of expertise.  I only need to know the A&P declares a repair major or minor not me. I do advise if I disagree but the A&P declares the repair major.

A DER is god like when it comes to design, analysis, and data certification because of her authority.  Yeah I said her, so what there are female DERs and I said god like not GOD.  She needs to substantiate that the approved data complies with the applicable FARs.  And that substantiation is only subject to the FAA ACO (FAA Engineers) review and scrutiny.

I have accepted .91 e/D on primary structure and disapproved 2.0 e/D on secondary structure. We DERs work the exact damage at the specific spot. I have shown over 50% material removal acceptable and have allowed cutting parts into two on purpose.

CALLAHAN AIRCRAFT SERVICES, LLC CURRENT PROJECTS:

BEECH KING AIR “EYEBROW WINDOW” STC / PMA
BEECH KING AIR UPPER AND LOWER EXTERNAL AVIONIC PLATFORMS STC / PMA
BELL 206L CARGO POD ALTERATION DESIGN, ANALYSIS, & APPROVAL
CESSNA 208 CARAVAN CARGO POD COMPOSITE STANDARD REPAIR
CESSNA 310Q LOWER FUSELAGE SKIN CUTOUT ALTERATION DESIGN, ANALYSIS, & APPROVAL
CESSNA 402C ENGINE MOUNT SHIM REPAIR STC / PMA
EMBRAER E170 & E190 SLAT TOOL JIGS AND CHECK FIXTURES DESIGN, ANALYSIS & APPROVAL
ALL COMPOSITE CARGO CONTAINERS TSO / PMA
MISCELLANEOUS REPAIRS DESIGN, ANALYSIS & APPROVAL

O x y m o r o n s

May I ask a question?

Words of Wisdom and Warning

“The Constitution of most of our states (and of the United States) assert that all power is inherent in the people; that they may exercise it by themselves; that it is their right and duty to be at all times armed and that they are entitled to freedom of person, freedom of religion, freedom of property, and freedom of press.”  Thomas Jefferson

Aged to perfection

If I’d known I was going to live so long, I’d have taken better care of myself!

We are suspending our weekly updates for now. Past postings will be updated, cleaned up, and revised but my “free” time will be given to my book, “Basic engineering for Aircraft Repairs” and associated 40 hour seminar. “Follow the money”

And spring has sprung so I have “farming/ ranching” to do like seeding 500 pounds of grass seed.

And we are welcoming two summer engineering interns, Matt and James to the office within the month.

And assembling AOG teams! Providing total technical and certification support for General Aviation for those problem repairs saving structure versus replacing parts.

Sincerely,

James W. Callahan

General Manager / FAA DER

DER@CALLAHAN.AERO

256-891-3677
P.O. BOX 533
Albertville, AL 35950

Visit our website at www.Callahan.aero or e-mail us at der@callahan.aero for any questions or special interest.

“Misunderstanding DERs“

1) A DER approves data.  Got it, it is that simple.

The fact that the DER’s definition and understanding is messed up may be because we had to create new acronyms, titles, and make things complicated in an effort simplify things.  Oh yeah, we as in we the people or the government.  Be leery of, “I’m from the government and I’m here to help you.”

So let’s go back twenty years or so when the non-FAA employee approving data engineer was called a DER.  A DER approves data. Most approved data is approved by a DER with FAA ACO (engineers) oversight.  Make sure you understand this because there are a lot of folks that don’t.  DERs approve data.

Data from the OEM is acceptable data only, it is not approved data.  Bill Boeing or the Boeing Company has NO authority to approve data.  Their DERs do and only their DERs do!  And they may use Consultant DERs as their DERs.  This goes for Cessna, Beech, Bombardier, etc.  DERs approve data not OEMs.

Is AC43.13-1 or -2 approved data? Very rarely, it is acceptable data from the FAA but not necessarily used for Major Repairs.  Read the first paragraph. If there is no approved data for your repair then replace the part, hire a DER, or ask FSDO.  There is no option to do want you think is okay.

AC No: 43.13-1B, signature sheet:

“1. PURPOSE. This advisory circular (AC) contains methods, techniques, and practices acceptable to the Administrator for the inspection and repair of nonpressurized areas of civil aircraft, only when there are no manufacturer repair or maintenance instructions. This data generally pertains to minor repairs. The repairs identified in this AC may only be used as a basis for FAA approval for major repairs. The repair data may also be used as approved data, and the AC chapter, page, and paragraph listed in block 8 of FAA form 337 when:

a. the user has determined that it is appropriate to the product being repaired;
b. it is directly applicable to the repair being made; and
c. it is not contrary to manufacturer’s data.”

The phrase “nonpressurized areas of civil aircraft” means AC43.13-1 can not support repairs on pressurized skins.  Normally it can’t but if there is approved data stating,  directing, or letting AC43.13 be allowed or used, then go for it.  Read carefully because if the approved data stated “apply corrosion protection IAW AC43.13-1″ it does not allow AC43.13-1 use except for the application of corrosion protection.

“only when there are no manufacturer repair or maintenance instructions” is another precise wording of legalize from the government.  Regardless, AC43.13-1 can’t be used if there is manufacturer data.  That means if there is a SRM or AMM but it doesn’t address the damage / repair be very careful and read the whole manual especially the introduction.  It may state some language limiting its use.

And if the manual defines primary structure then the definitions of major repair just got changed. The FAA approved manual overrides the definitions of primary structure listed in FAR Part 43, App. A.

AC No: 43.13-2B, signature sheet:

“1. PURPOSE. This advisory circular (AC) contains methods, techniques, and practices acceptable to the Administrator for the inspection and alteration on non-pressurized areas of civil aircraft of 12,500 lbs gross weight or less. This AC is for use by mechanics, repair stations, and other certificated entities. This data generally pertains to minor alterations; however, the alteration data herein may be used as approved data for major alterations when the AC chapter, page, and paragraph are listed in block 8 of FAA Form 337 when the user has determined that it is:

a. Appropriate to the product being altered,
b. Directly applicable to the alteration being made, and
c. Not contrary to manufacturer’s data.”

Notice there is more latitude for alterations compared to repairs.

CALLAHAN AIRCRAFT SERVICES, LLC CURRENT PROJECTS:

BEECH KING AIR “EYEBROW WINDOW” STC / PMA
BEECH KING AIR UPPER AND LOWER EXTERNAL AVIONIC PLATFORMS STC / PMA
BELL 206L CARGO POD ALTERATION DESIGN, ANALYSIS, & APPROVAL
CESSNA 208 CARAVAN CARGO POD COMPOSITE STANDARD REPAIR
CESSNA 310Q LOWER FUSELAGE SKIN CUTOUT ALTERATION DESIGN, ANALYSIS, & APPROVAL
CESSNA 402C ENGINE MOUNT SHIM REPAIR STC / PMA
EMBRAER E170 & E190 SLAT TOOL JIGS AND CHECK FIXTURES DESIGN, ANALYSIS & APPROVAL
ALL COMPOSITE CARGO CONTAINERS TSO / PMA
MISCELLANEOUS REPAIRS DESIGN, ANALYSIS & APPROVAL

O x y m o r o n s

A verbal contract isn’t worth the paper it’s written on. — Samuel Goldwyn

Words of Wisdom and Warning

“Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote!”
Benjamin Franklin

Aged to perfection

We do not stop playing because we are old; we grow old because we stop playing.

Sincerely,

James W. Callahan

General Manager / FAA DER

DER@CALLAHAN.AERO

256-891-3677
P.O. BOX 533
Albertville, AL 35950

Visit our website at www.Callahan.aero or e-mail us at der@callahan.aero for any questions or special interest.

“JOINTS – LAP”

From last week we had

 
CALLAHAN AIRCRAFT SERVICES, LLC CURRENT PROJECTS:

BEECH KING AIR ENGINE MOUNT REPAIR DESIGN, ANALYSIS & APPROVAL
BEECH KING AIR “EYEBROW WINDOW” STC / PMA
BEECH KING AIR WING LOWER SPAR CAP REPAIR DESIGN, ANALYSIS & APPROVAL
BEECH KING AIR UPPER AND LOWER EXTERNAL AVIONIC PLATFORMS STC / PMA
BELL 206L CARGO POD ALTERATION DESIGN, ANALYSIS, & APPROVAL
CESSNA 208 CARAVAN CARGO POD COMPOSITE REPAIR
CESSNA 310Q LOWER FUSELAGE SKIN CUTOUT ALTERATION DESIGN, ANALYSIS, & APPROVAL
CESSNA 402C ENGINE MOUNT SHIM REPAIR STC / PMA
CONVAIR 440 AIRBORNE PLATFORM ANALYSIS & APPROVAL
EMBRAER E170 & E190 SLAT TOOL JIGS AND CHECK FIXTURES DESIGN, ANALYSIS, & APPROVAL
ALL COMPOSITE CARGO CONTAINERS TSO / PMA
MISCELLANEOUS REPAIRS DESIGN, ANALYSIS & APPROVAL

This joint can hold 6480 pounds before it fails and it will fail with all the six rivets shearing into two separate pieces.  It is not nor probable that these twelve rivet pieces would come loose and fall out if properly installed.  Probable doesn’t mean it wont happen, it just means it isn’t likely but given a hundred examples having only sixty or eighty pieces left in place would fit the definition of probable.

A joint’s load may not be directly related to aircraft weight.  Try closing a door only an inch from the upper hinge and notice how much force or load you used.  Now repeat this but this time next to the door knob instead of th hinge.  Notice it had nothing to do with the door’s weight (weight did not change).  Well that’s how loads work and in aircraft with limited space we can have high loads.

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.

O x y m o r o n s

Gentlemen, I want you to know that I am not always right, but I am never wrong. – Samuel Goldwyn

Words of Wisdom and Warning

“I believe there are more instances of the abridgement of the freedom of the people by the gradual and silent encroachment of those in power, than by violent and sudden usurpation.”
President James Madison (1751-1836) speech, Virginia Convention, 1788

Aged to perfection

It is up to us whether age brings wisdom or age comes alone.

Sincerely,

James W. Callahan

General Manager / FAA DER

DER@CALLAHAN.AERO

256-891-3677
P.O. BOX 533
Albertville, AL 35950

Visit our website at www.Callahan.aero or e-mail us at der@callahan.aero for any questions or special interest.

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. 

“JOINTS – LAP”

Iyi gunler or 좋은 날 and best wishes from America

A lap joint is simply a joint with overlapping parts and is either glued, nailed, or even spot welded together.


Yes, another story, when I was working “delivery” at a major mod center whose initials were Boeing Mod, I was discussing an aircraft issue concerning the aisle way ceiling panels.  I had a couple of trainees with me when I said, “so you are going to nail it together, right?”  On the way back to the office the bright one asked, “they use nails?”  It is a figure of speech. Nails refer to rivets or bolts and glue is resin. When working with experienced mechanics, I shouldn’t have to state the obvious.  But then again.

I consider this subject the gist of what we do in the repair world. Consider this example:

I’ve been told that A&P Mechanics learn how to do this kind of calculation but I wonder how many remember how. The answer will be in next weeks post.

CALLAHAN AIRCRAFT SERVICES, LLC CURRENT PROJECTS:

BEECH KING AIR ENGINE MOUNT DAMAGE REVIEW
BEECH KING AIR “EYEBROW WINDOW” STC / PMA
BEECH KING AIR WING ROOT SPAR CAP CRACK AD 89-25-10 AMOC REPAIR DESIGN, ANALYSIS & APPROVAL
BEECH KING AIR UPPER AND LOWER EXTERNAL AVIONIC PLATFORMS STC / PMA
BOEING 737 & 757 DAMAGE TOLERANCE REPAIR APPROVALS
CESSNA 402C ENGINE MOUNT SHIM REPAIR STC / PMA
CONVAIR 440 AIRBORNE PLATFORM ANALYSIS & APPROVAL
EMBRAER E170 & E190 SLAT TOOL JIGS AND CHECK FIXTURES DESIGN, ANALYSIS & APPROVAL
GULFSTREAM III AIRBORNE PLATFORM APPROVAL
LOCKHEED SUPER CONSTELLATION DOOR REPAIR APPROVAL
ALL COMPOSITE CARGO CONTAINERS TSO / PMA
MISCELLANEOUS REPAIRS DESIGN, ANALYSIS & APPROVAL

You may have to visit the blogs on the four modes of failure.

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.

O x y m o r o n s

Gentlemen, I want you to know that I am not always right, but I am never wrong. -Samuel Goldwyn

Words of Wisdom and Warning

“I believe there are more instances of the abridgement of the freedom of the people by the gradual and silent encroachment of those in power, than by violent and sudden usurpation.”
President James Madison (1751-1836) speech, Virginia Convention, 1788

Aged to perfection

It is up to us whether age brings wisdom or age comes alone.

 항공기, 비행기,베어링, 긴장, Shear, 압축, 가장자리 거리, 가장자리 차로 실패의 4 모드, 기체,갑 심, 신문기사, 패커는, preload, 당기고, 눈물, 쇼생크, 구조, 관용, 분석, stressjoint, 피로감, 태 성장, 도르래 장치, 끈, 수립했던

Sincerely,

James W. Callahan

General Manager / FAA DER

DER@CALLAHAN.AERO

256-891-3677
P.O. BOX 533
Albertville, AL 35950

航空機、飛行機、ベアリング、緊張感、せん断、圧縮、端距離、端のマージン、失敗した場合、胴体、ギャップ、シム、フィラーの 4 つのモード, パッカー、荷重、引き付け、切り取り、シャンク、構造、寛容、分析、 stressjoint 、疲労、亀裂成長、リベット、ストラップ、ダブラ

Visit our website at www.Callahan.aero or e-mail us at der@callahan.aero for any questions or special interest.

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.

“SHIMMING” continued

Shim/Filler Combinations – In some circumstances, a filler may be used in conjunction with a laminated shim to fill a gap in structure. When using this combination, take up the maximum gap possible with the solid filler. Boeing requires designers to obtain the Stress group approval for structural applications. Funny thing is this is for designers but your customer support, Liaison, LE, Life Cycle Product, or MRB Engineer will do that too. Why? Why not or maybe they don’t know structure. If they don’t know structure then are they the ones “that carry paper from the customer to the engineers” Reference Office Space, the movie. But for those of you that want those jobs at Boeing make sure you use all these keywords: Liaison, LE, Life Cycle Product, and MRB Engineer. Human Resources is all about keywords and their college degree so don’t expect them to think.

I think college is a tool and is important but I was told a long time ago that all college does is teach you how to work for someone else.

“Shimming, the answer to all gap problems, specially for tapered gaps has to be done correctly.” Duh, I quoted that from some place but brushing your teeth has to be done correctly too.

Have you ever considered a torqued tension bolt introduces preload stresses into the bolt of 50 to 60 ksi? Yes, AND it is acceptable even desired for structural reasons.

Three things before we continue on shimming. One: engineers think in stress where the mechanic is concerned with applied torque. Applied torque can be directly translated into bolt tensile stress. Two: you can usually identify a tension joint because tension bolts and nuts are used. And “ksi” is thousand pounds per square inch.

But imagine a tension joint with 220 ksi bolts torqued to 60 ksi that is shimmed with laminated shim stock.

Let’s say the fatigue loads induce 40 ksi stress on these bolts. The maximum and minimum stresses would be 100 ksi (60 ksi + 40 ksi) and 60 ksi, respectively. The stress ratio (minimum divided by maximum) or R is 60/100 = .60. Let’s assume the fatigue tensile stress required is 40 ksi, from the S-N curves (Stress – Cycle or load versus flight cycles) this joint is good for a million cycles. But, as time marches on the shim starts to fret and develops a .000001″ gap. Bolt preload is now zero! Stress ratio is 0 (0 ksi/40 ksi) and the joint is good for only 12,000 cycles. Yes. laminated shims have ‘fretting’ problems as well as a corrosion concerns.

If this example seems unrealistic look at an engine pylon diagonal brace attachment on the B767. The tension fitting common to the aft bulkhead had this problem due to poor shimming practices. Running the aircraft up and down the tarmac induces fatigue stresses at this joint. Production inspection only checked for gaps around the periphery of the shim not at the bolts. It was argued it took too much time and impractical to measure. The designers and production agreed that the Stress group was the problem not poor design. Well, the airlines had a different opinion being that the joint was failing in service but design and production still complained.  The Stress group (me) suggested a redesign to a shear joint but that would cost money. So the beat goes on with the Engine Strut Drag brace failures.  Good thing the strut is designed or should I say stressed for any one of four attachments failing.

Time for another story this time in Narita.  An aircraft landed and while taxiing one of the engines fell to the tarmac.  You see someone left out the bolt in the R2 joint and apparently R1 failed so the strut rotated down and aft placing the engine on the ground.  Oops. Because of another incident, each strut now has 4 more attachments.

Tension fillings are not the preferred choice for fatigue joints but due to manufacturing plans they are used.

Did you General Aviation folks go to sleep?  Think about the outer to inner wing joints!  Of course they have ADs on them. But before you criticize the design, these aircraft have lasted well beyond their design lives.

CALLAHAN AIRCRAFT SERVICES, LLC CURRENT PROJECTS:

BEECH KING AIR ENGINE MOUNT DAMAGE REVIEW
BEECH KING AIR “EYEBROW WINDOW” STC / PMA
BEECH KING AIR UPPER AND LOWER EXTERNAL AVIONIC PLATFORMS STC / PMA
BOEING DC 9-15 PASSENGER TO CARGO CONVERSION AMOC
CESSNA CARAVAN COMPOSITE CARGO POD TSO / PMA
CESSNA 310 BELLY SKIN CUTOUT ALTERATION
CESSNA 402C ENGINE MOUNT SHIM REPAIR STC / PMA
CONVAIR 440 AIRBORNE PLATFORM ANALYSIS & APPROVAL
EMBRAER E170 & E190 SLAT TOOL JIGS AND CHECK FIXTURES DESIGN, ANALYSIS & APPROVAL
LOCKHEED SUPER CONSTELLATION CARGO FLOOR PANEL REPAIR DESIGN AND ANALYSIS
ADVANCE COMPOSITE CARGO CONTAINERS TSO / PMA
MISCELLANEOUS REPAIRS DESIGN, ANALYSIS & APPROVAL

Next week’s subject hasn’t been set. I have several posts in work but I’ve been a little busy too. And talking of being busy, I’ve noticed MROs, repair stations, and other aircraft places are “dumbing down” along with a few FSDOs. Looks like “our lack of experience” is finally showing. We mature aircraft folks are repeating ourselves with “they just don’t get it”

I remember visiting a client with a young engineering CO-OP student of mine. The aircraft had suffered some damage having been driven into a panel truck. The propeller blades shredded that truck but our problem was the plane. The client’s Liaison Engineer was a mature A&P mechanic from the school of hard knocks. We addressed all the damage individually in less than a half hour. Ah, the good old days. I was done except for finishing up. We decided most of the damage would be repaired per SRM. I would make large cutouts and splice in new panel sections. So we had a plan and my student engineer made a rubbing of all the damage to take back home. He said that when the senior mechanic (Liaison Engineer) and I discussed each discrepancy or damage neither one of us made a complete word, we grunted the whole time. I believed I said “yeah” once or twice but usually said “uh uh” and he said “hmm” but there was a lot of thumbs up, slit your throat motion, etc. you know non-verbal communication. Today I find myself explaining several times in different ways. Oh and I am talking mainly about management.

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.

O x y m o r o n s

A little pain never hurt anyone.

Words of Wisdom and Warning

“We the People are the rightful masters of both Congress and the Courts–not to overthrow the Constitution, but to overthrow the men who pervert the Constitution.”
Abraham Lincoln

Aged to perfection

Anyone who keeps the ability to see beauty never grows old.

Sincerely,

James W. Callahan

General Manager / FAA DER

DER@CALLAHAN.AERO

256-891-3677
P.O. BOX 533
Albertville, AL 35950

Visit our website at www.Callahan.aero or e-mail us at der@callahan.aero for any questions or special interest.

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?

“SHIMMING”

The recent problems on the A380 wing rib “boom” or shear ties and the B787 aft fuselage shear ties may be related in several ways.

One of those reasons may be shimming. I have to say “may” because obviously I don’t have all the particulars. What I do know and understand is shimming aircraft structure and the apparent lose of that tribal knowledge.

When I was a pup representing Boeing on the start-up of the “shimless” B757 after supporting both the B727 and 737 production lines shimming was one of the hot topics. The B757 aircraft is much lighter than the B727 it replaced but Boeing accepted a weight penalty designing the B757 shimless fuselage shear ties. I was heavily thrown into the discussion around a $50 million lawsuit from the vendor (they lost). There were many issues with that joint requiring me to release a memo directing the vendor on shimming restrictions and a formal non-proprietary document was later produced called “DESIGN GUIDE FOR STRUCTURAL SHIMMING.” And remember “physics don’t change” with time nor place. So let’s begin.

What is a shim?

“A shim is a thin and often tapered or wedged piece of material, used to fill small gaps or spaces between objects” per Merriam-Webster Dictionary. A “shim” may be a generic term for shim, filler, packer, structural shim, etc.  Talk is cheap and we don’t always use the precise term so make sure you are using the correct term for the correct application. Our English and Canadian cousins like the term “packer” for instance.  I assume the Koreans use another term but regardless translating terminology between cultures can add to the confusion.  I’m trying to remove the confusion so feel FREE to ask for and explain any culture issues.  I’m a Southerner so when I say “bless his heart” I am not being nice but those damn yankees fall for it  and we are both Americans (and forget those west coast dudes).  Culture difference are good but needs to be addressed to communicate correctly.

Paraphrasing Wikipedia shims are typically used in order to adjust for better fit or as spacers to fill gaps between parts subject to wear. Sounds good but incomplete because shims are used in an airplane assembly to:

a. Control structural fit-up
b. Maintain contour
c. Maintain alignment
d. Provide for aesthetics
e. Provide adjustment

Shims are necessary evils because there are gaps. We have gaps because we live in a real world. The significant issue with improper shimming is the pull-up load or preload that can cause large built-in tensile residual stress. Such tension stress can seriously affect part-life through fatigue cracking and stress corrosion cracking. That gibberish means any gap no matter how small has already started to break the joint or part. More stuff follows for those interested in more details.

Each joint is unique and requires an analysis of its deflection and stress for the typical ivory tower statement on acceptable gaps but in reality there are some accepted rules of thumbs that Henry Ford (the dude that nurtured mass production) would appreciate. What is important is there are options, there are always options, some good some poor but by using a good engineer one can get some creative options.

Fatigue performance is affected by alternating stress and mean stress. Pull-up stress does not necessarily affect the alternating stress, but will significantly affect the mean stress. The material S-N curve shows this effect and notice part-life is significantly reduced at all alternating stress levels.

CALLAHAN AIRCRAFT SERVICES, LLC CURRENT PROJECTS:

BEECH KING AIR ENGINE MOUNT DAMAGE REVIEW
BEECH KING AIR “EYEBROW WINDOW” STC / PMA
BEECH KING AIR WING ROOT SPAR CAP CRACK AD 89-25-10 AMOC REPAIR DESIGN, ANALYSIS & APPROVAL
BEECH KING AIR UPPER AND LOWER EXTERNAL AVIONIC PLATFORMS STC / PMA
BOEING 737 & 757 DAMAGE TOLERANCE REPAIR APPROVALS
CESSNA 402C ENGINE MOUNT SHIM REPAIR STC / PMA
CONVAIR 440 AIRBORNE PLATFORM ANALYSIS & APPROVAL
EMBRAER E170 & E190 SLAT TOOL JIGS AND CHECK FIXTURES DESIGN, ANALYSIS & APPROVAL
GULFSTREAM III AIRBORNE PLATFORM APPROVAL
LOCKHEED SUPER CONSTELLATION DOOR REPAIR APPROVAL
ALL COMPOSITE CARGO CONTAINERS TSO / PMA
MISCELLANEOUS REPAIRS DESIGN, ANALYSIS & APPROVAL

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.

O x y m o r o n s

A little pain never hurt anyone.

Words of Wisdom and Warning

“We the People are the rightful masters of both Congress and the Courts–not to overthrow the Constitution, but to overthrow the men who pervert the Constitution.”
Abraham Lincoln

Aged to perfection

Anyone who keeps the ability to see beauty never grows old.

Sincerely,

James W. Callahan

General Manager / FAA DER

DER@CALLAHAN.AERO

256-891-3677
P.O. BOX 533
Albertville, AL 35950

Visit our website at www.Callahan.aero or e-mail us at der@callahan.aero for any questions or special interest.

“A mechanically fastened joint“

What is a joint?

Stop laughing this is serious.  A joint is the joining together of two or more parts by welding, mechanically fastening, or bonding. First we need to discuss identifying what type of joint we have and then what that means. Wow, that sounded simple but I’m overwhelmed on how to do that especially here on this blog.  Well, let’s give it the old college try. WAR EAGLE!

When two parts come together to transfer a load (not all joints transfer load) it is by tension, compression, or shear. Tension is pulling, compression is pushing, and shear is ripping, cutting, or sliding sideways.  Therefore we have tension joints, shear joints, and compression joints or any combination there of.

Combination thereof? What the heck does that mean? Think of a stringer on the side of the aft fuselage section with the tail reacting side wind loads.  Which side is the wind coming from? The answer is both sides over the life of the airplane so that stringer must be able to react either tension or compression.

Take a piece of paper, lay it flat on a table, place both hands touching tightly side by side flat on that paper then while pressing down slide your right hand away from you and keep the left hand stationary. That is shear. Now take your thumb and index fingers of each hand to the top of the paper and tear it. That’s shear. Take a pair of scissors and cut the paper. That’s shear. Don’t worry, it is a hard concept to master.  So get on with it and master it!

A typical skin lap joint is a shear joint. Sheet metal webs transfer their load primarily by shear. Shear Ties transfer their shear load primarily by shear. Stringer clips transfer their tensile load primarily by shear.

There are very few compression joints but when you find one study it. It should be interesting like the compression joint on a 747-200 keel beam. A tension joint is actually a poor design and brings with it several problems especially in fatigue and shimming. A shear joint is the preferred method of joining two parts even in composites. The fay surface bonding agent transfers the load from part to part and a welded joint transfer the load through the fillet weld.

A shear joint may take a part loaded in tension  as shown above and transfer the load by shear. So now it gets tricky and next week we will introduce some graphics to help explain it. One must read and listen to the verbiage because we will mix and match words. (and that is why engineers don’t want to explain things. It takes time, quite a bit of time and they aren’t here to teach. Neither am I really, I’m just stupid.)

And what about the analytical modeling of the joint as a pinned, fixed, or simply supported? We will discuss those in beam and pin bending.

CALLAHAN AIRCRAFT SERVICES, LLC CURRENT PROJECTS:

BEECH KING AIR “EYEBROW WINDOW” STC / PMA
BEECH KING AIR WING ROOT SPAR CAP CRACK AD 89-25-10 AMOC REPAIR DESIGN, ANALYSIS & APPROVAL
BEECH KING AIR UPPER AND LOWER EXTERNAL AVIONIC PLATFORMS STC / PMA
BOEING 737 & 757 DAMAGE TOLERANCE REPAIR APPROVALS
CESSNA 208 CARAVAN CARGO POD STANDARD LARGE REPAIR PROCESS
CESSNA 402B UPPER WING WALK REINFORCEMENT REPAIR DESIGN, ANALYSIS & APPROVAL
CESSNA 402C ENGINE MOUNT REPAIR STC / PMA
CONVAIR 440 AIRBORNE PLATFORM ANALYSIS & APPROVAL
EMBRAER E170 & E190 SLAT TOOL JIGS AND CHECK FIXTURES DESIGN, ANALYSIS & APPROVAL
GULFSTREAM III AIRBORNE PLATFORM APPROVAL
LOCKHEED SUPER CONSTELLATION DOOR REPAIR APPROVALS
ALL COMPOSITE CARGO CONTAINERS TSO / PMA
MISCELLANEOUS REPAIRS DESIGN, ANALYSIS & APPROVALS

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.

O x y m o r o n s

A little pain never hurt anyone.

Words of Wisdom and Warning

“We the People are the rightful masters of both Congress and the Courts–not to overthrow the Constitution, but to overthrow the men who pervert the Constitution.”
Abraham Lincoln

Aged to perfection

Anyone who keeps the ability to see beauty never grows old.

Aeronaves, aviões, ostentando, tensão, compressão, cisalhamento, distância à borda, margem, borda quatro modos de falha, fuselagem, gap, calço, enchimento, packer, expansão volêmica, puxe para cima, se rasgarem, pernil, estrutura, tolerância, análise, stressjoint, fadiga, crescimento de uma trinca, rebite, alça, duplicador

Sincerely,

James W. Callahan

General Manager / FAA DER

DER@CALLAHAN.AERO

256-891-3677
P.O. BOX 533
Albertville, AL 35950

Visit our website at www.Callahan.aero or e-mail us at der@callahan.aero for any questions or special interest.

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?

“Company versus Consultant DERs“

Company DERS are now called ARs  just to add confusion to an already complex situation.

If I have only confused you more about DERs just remember we are the master of change and deviation and are extremely anal.  If you think you need four widgets but only have three widgets call us because we may approve only three or even two widgets unless we explain you really need five or no widgets. And we will ask what a widget is and its specification.

But one of the reasons DERs seem to be misunderstood is because we create new data. New data as in original data. The OEM may generate and appear to approve data for the A&P’s use but actually the OEM only generates unapproved data. The FAA approves all data but they may delegate this authority and responsibility to some qualified engineers at the OEM.  The OEM does not receive this authority, the individual AR does.

The company DER may only approve data on their own company’s products.

Did you know when you call the OEM for engineering assistance you usually get customer support (a non-engineer) that suggests a known repair or part replacement. When you open up your pocketbook  communication with an engineer starts.  The keyword is “an” meaning any or any recent new hire to screen the calls. If you PAY for the repair then it will be analyzed by a stress analyst (engineer).  Once the repair is shown acceptable it is given to the AR or DAS engineer for FAA approval. Yep, I threw another acronym into the mix so here are they are: AR, DAS, DER, DOA, SFAR 36, and ODA engineering staff members. Did you notice you don’t talk to the approving DER.

Consultant DERs can be hired by an OEM representing OEM’s ARs staff. The Consultant DER approves OEM data for the OEM like a company DER.  There are some countries that will not accept a Consultant DER’s approval but if he is sitting at the OEM they will.  Canada doesn’t have a choice because of our bilateral agreement with them, they have to accept it.

Consultant DER are not restricted to any companies product or geographical area.  A misconception about Consultant DER is their lack of available data may be wrong. DERS  have enormous resources and are NOT restricted by office politics, other OEM customer requirements, or most importantly the cosmetic requirements.

Office politics held up the use of a new corrosion inhibiting sealant on new Boeing aircraft because their Wichita plant developed it. It took years for Boeing Seattle to accept it on their aircraft.And you would have thunk that Boeing cares about corrosion protection more than male ego.

The story I like is the “Wichita repair” for the 747 aft pressure bulkhead developed in Wichita by Liaison Engineers (not designers or stress analysts). Everett Division wouldn’t put Wichita developed repairs in the SRM (Everett builds the 747) but when the airlines demanded the repair was inserted into the SRM. All this repair does is to allow access and repair of the lower aft pressure bulkhead when corroded but its’ not like it was more important than Everett elitism (remember Japan Airlines Flight 123).

But the best part of a Consulting DER is he doesn’t need to make it pretty. A dented fender is acceptable but a Ford dealer (OEM) will push a new one or a repair. You don’t have to fix it and you could remove the fender. And if you’re a taxi or bus service a “use as is” approval is worth a lot especially given within minutes in the middle of the night.

Other customer requirements means you accept an exterior doubler with protruding head rivets accepting the drag penalty and cosmetic scar next to the entry door but other airlines or corporate owners say no to “scab” patches.  Your DER will approve a scab patch but the OEM DER may not.

I had a sharp deep skin dent just aft of the entry door on a DASH 8 that was scheduled to depart within the hour at 7 AM. What to do? Simple, drill a big hole to remove dent (3/8″‘ diameter), HFEC, then install 3/8″ diameter protruding head bolt (exterior), washer, and nut. Plane was ready and off it went. Oh the OEM did not like that because it was ugly (and it was) and they said, “we would never do that!” So they would never get an aircraft airworthy to make a scheduled revenue flight? Because their solution several hours later was to ground the aircraft and repair it “properly” (skins, door cutout reinforcing doubler, adjacent skin lap, a long down time.  My repair was “properly” repaired later at the next C check (planned long down time inspection, maintenance, and repair) within the year. Safe and certified! Right now there are engineers thinking I was wrong to do that!

Before you give me credit for being a genius, this repair is in the 747 SRM. Oh, those poor engineers that were just thinking I was wrong are confused because if it is in a Boeing SRM it must be right.  No. it doesn’t. It means it is approved and it may be wrong because there are errors in SRMs. Why do you think there are ADs.

All DERs must comply with the Federal Aviation Regulations and physics don’t change. But it is a given the OEM DER may be more up to date and access to more data leaving the Consulting DER to be more conservative. And don’t forget all DERs are not created equal but we are all Amazing Super Stars (acronym?).

CALLAHAN AIRCRAFT SERVICES, LLC CURRENT PROJECTS:

CONVAIR 440 AIRBORNE PLATFORM ANALYSIS & APPROVAL
SUPER CONSTELLATION REBUILD REPAIRS
GULFSTREAM III AIRBORNE PLATFORM ANALYSIS & APPROVAL
402B UPPER WING WALK REINFORCEMENT REPAIR DESIGN, ANALYSIS & APPROVAL
402C ENGINE MOUNT SHIM REPAIR STC / PMA
E170 & E190 SLAT TOOL JIGS AND CHECK FIXTURES DESIGN, ANALYSIS & APPROVAL
KING AIR “EYEBROW WINDOW” STC / PMA
KING AIR WING ROOT SPAR CAP CRACK AD 89-25-10 AMOC REPAIR DESIGN, ANALYSIS & APPROVAL
KING AIR UPPER AND LOWER EXTERNAL AVIONIC PLATFORMS STC / PMA
ALL COMPOSITE CARGO CONTAINERS STC / PMA
MISCELLANEOUS REPAIRS DESIGN, ANALYSIS & APPROVAL

Next week, “identifying a shear joint”  And we haven’t forgotten shimming

Y’all, some 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. I did say we wouldn’t be PC so I confess, there are quite a few DERs and engineers that are jerks.  They do milk the job for all its worth and complicate the design on purpose.  Some even generate designs on purpose that wont fit so they make more money.

 I was working AF-1 after it was over due and over budget with poor but acceptable inspected cosmetic quality is the perfect example of unethical engineering.  The B747-200 AF-1 project went to a design / build phase  because of schedule (meaning the design is late but manufacturing is ready).  Contrast that with other design / build projects that design is planned to be concurrent with the build in an overall effort to tighten the schedule.  The AF-1 program hired many contract engineers and some were affiliated with their own contract shop so they had an unethical incentive to generate engineering man-hours. A particular contract engineer would make suggestions because noticed the Boeing management team’s lack of the design and manufacturing process knowledge and the overall engineers lack of modification experience and design skill.  He made two types of suggestions with one being the placement of avionics and other equipment knowing full well there would be a conflict with other installations down the line. This allowed him to “immediately” know how to remedy the “problem” when it surfaced. This one act generated two very positive results for him. One it generated more engineering man-hours and two his standing among his peers and management soared. The later lent to him being a Czar of the design / build teams. The second type of suggestion were the “improvements” like suggesting an access panel between to wire bundle connections “in case” they ever had to have access between those connections.  It was a remote possibility but if maintenance did need access later, couldn’t they do it then. And the delivery slid to the right, costs soared, and he was praised and his wallet grew thicker. Oh, how do I know this?  We bumped heads over a disconnect bracket (I won).

My network of DERs and engineers do not do this because they are ethical and some are even moral. “The ethical man knows he shouldn’t cheat on his wife, whereas the moral man actually wouldn’t.” Dr. Donald “Ducky” Mallard (David McCallum) in the CBS television series “NCIS”

O x y m o r o n s

A verbal contract isn’t worth the paper it’s written on. — Samuel Goldwyn

Words of Wisdom and Warning

“Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote!”
Benjamin Franklin

Aged to perfection

We do not stop playing because we are old; we grow old because we stop playing.

Sincerely,

James W. Callahan

General Manager / FAA DER

DER@CALLAHAN.AERO

256-891-3677
P.O. BOX 533
Albertville, AL 35950

Visit our website at www.Callahan.aero or e-mail us at der@callahan.aero for any questions or special interest.

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?

So what is the ACO?

It is the Aircraft Certification Office and is RESPONSIBLE for:

• Design approval and certificate management
• US production approvals
• Engineering and analysis questions
• Investigating and reporting aircraft accidents, incidents, and service difficulties
• Designated Engineering Representatives (DER) oversight

or commonly put they are the FAA engineers.  Behind them are more engineers writing, coordinating and editing regulations, testing, researching, etc.  But ACOs rely extensively on DERs and commonly delegate FSDO and MIDO type issues to them.

I was once visiting Larry at an ACO when it so happened a FSDO inspector from Seattle called questioning whether or not I was a DER.  Back in the day there was no handy and accurate directory on the internet so I thought nothing of the question.  Larry went ballistic shouting back at the FSDO inspector about how dare question a DER’s legitimacy.  Larry cooled down and acknowledged he may have overreacted but he hadn’t had his morning office coffee yet.  There are touchy subjects out there people and it isn’t spell check.  FSDO doesn’t report to the ACO and the ACO doesn’t report to FSDO. And the Navy doesn’t report to the Army and the Army doesn’t report to the Navy. (But both of them report to the Air Force)

Seriously, they should work together and they all report to the President as does the FAA.

FAA chain of command:

Between FSDO / MIDO and the ACO, there isn’t one. They are supposed to work together within their defined roles and responsibility but as in all good marriages there are differences of opinion (and personalities.) The ACO can trump FSDO the same as a MRB engineer trumps an inspector on the factory floor.  But FSDO / inspector can trump the ACO/ engineer depending on the function. Engineering wrote the book so their interpretation wins but FSDO controls the process of approval. A good engineer listens because dare I say it, “the engineer might not have been as clear as he could have been.”  “Trust me, I’m an engineer.”  Okay stop laughing, we are human even if we don’t show it. We really do laugh quite a bit but usually away from mechanics, inspectors, accountants, managers, and anyone else not an engineer.  You don’t think we know when we screw you? And we don’t actually do it, God or nature does it. Engineers have limitations and I wish some engineers would acknowledge it. If we need 2 plus 2 then we will say 4, not what someone else wants us to say even if intimidated.

I take great pride in helping bankrupt three airlines for several good deeds.   Remember Peoples Express, two days before redelivery I was able to take a 747 wheel well left hand frame and by cutting it into three separate pieces and splicing them back together, installed it on the right hand side making delivery.  Peoples Express didn’t have the cash to take redelivery.  Oops, Chapter 11.

I remind you, when I say we or I spliced, installed, made, etc. it means we or I wrote and approved the engineering technical data. The mechanics do the hands on work.

But I take great pride in making scheduled delivery on budget with an acceptable level of quality aircraft repair or alteration that complies with all the requirements. That may sound impossible but if you get a DER’s bill, you will understand it is not impossible just expensive. Seriously a DER works in the world of deviation from the norm.

Repair DERs are the masters of deviation assuring a safe and certified repair.  Most A&Ps don’t have a clue what a good engineer can do with structure.  I arrived at a modification center and one of my first problems was a vertically cracked fore and aft running L angle along the exterior of the vertical stabilizer.  I told them to cut it through into two pieces, blend and smooth, and paint the ends. What chaos broke out after releasing that data. Cutting a structural part into two separate pieces and NOT splicing them back together seem odd to you? Well, it was done after it was explained to the shop by another engineer. It is what we do and we take over where the manuals stop.

CALLAHAN AIRCRAFT SERVICES CURRENT PROJECTS:

CONVAIR 440 AIRBORNE PLATFORM ANALYSIS & APPROVAL
SUPER CONSTELLATION REBUILD REPAIRS APPROVAL
402B UPPER WING WALK REINFORCEMENT REPAIR DESIGN, ANALYSIS & APPROVAL
402C ENGINE MOUNT SHIM REPAIR STC / PMA
E170 & E190 SLAT TOOL JIGS AND CHECK FIXTURES DESIGN, ANALYSIS & APPROVAL
KING AIR “EYEBROW WINDOW” STC / PMA
KING AIR WING ROOT SPAR CAP CRACK AD 89-25-10 AMOC REPAIR DESIGN, ANALYSIS & APPROVAL
KING AIR UPPER AND LOWER EXTERNAL AVIONIC PLATFORMS STC / PMA
ALL COMPOSITE CARGO CONTAINERS STC / PMA
MISCELLANEOUS REPAIRS DESIGN, ANALYSIS & APPROVAL

Next week, “Company versus Consultant DERs”  (not a battle but the differences)  and the means of approving data. And we haven’t forgotten shimming and by request identifying a shear joint.

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.

O x y m o r o n s

AIRLINE SCHEDULES

Words of Wisdom and Warning

“Every step we take towards making the State our Caretaker of our lives, by that much we move toward making the State our Master.”
Dwight D. Eisenhower

Aged to perfection

Growing older we learn miracles are great, but they are so darn unpredictable.

Sincerely,

James W. Callahan

General Manager / FAA DER

DER@CALLAHAN.AERO

256-891-3677
P.O. BOX 533
Albertville, AL 35950

Visit our website at www.Callahan.aero or e-mail us at der@callahan.aero for any questions or special interest.

CERTIFICATION from a DERs point of view by request.

What is a DER?

A DER is a Delegated Engineering Representative of the Federal Aviation Administration. “Designation of a private person as a DER is a privilege granted by the Administrator. It is not the right of every qualified applicant to receive a DER designation.”

“The DER is the connecting link in the engineering team between the FAA and the repair work in the hangar. He does not work for the FAA, but is a member of the Super Star engineering team, yet by virtue of his license as an extended arm of the FAA, he has the authority to make decisions and approve engineering work. “My signature at the bottom of a document carries the same weight as an official FAA stamp,” he says. In this connection DERs are subject to stringent checks on the part of the FAA, they have to submit their signed documents to the assigned FAA specialist supervision office for examination and every year they have to demonstrate their competence in an FAA check. “But we can also approach our FAA contacts on critical issues and obtain advice,” he explains. “In the American engineering world, there are just two industries that are controlled and regulated to this extent – aviation and the nuclear industry – and for good reason!”" Lufthansa Technik

What is an Engineer?

We need to explain what an engineer is in the good ol US of A aircraft industry.  And this is a touchy subject when thin skinned junior engineers take offense.  An engineer does not have to have a college degree.  The Roman Empire engineers designed and built many roads without any college degree.

The Egyptians built the first computer using binary code.  It was an irrigation system with go and no-go gates providing water to the exact field intended.  I think a lot of farmers are good engineers and a designer does not need to be an engineer.

My older brother still thinks I drive a train but really I drive a tractor.

Engineers design, analyze, test, research, study, and sometimes even do drafting.  Most aircraft engineers are Designers but most Structural DERs have been Stress Analyst and usually have at least a bachelors degree in engineering.  A Stress Analyst belongs to a Staff or specialist group similar to aerodynamics, thermodynamics, or loads groups. A Stress Analyst crunches the numbers to substantiate the structural strength of the design. The following poster is not a joke, it’s true and these groups get passionate about the importance of their group. They all think they are the most important therefore the actual product is a compromise. Lately the manufacturing engineer has been brought into the act so more committee action and further compromise. So get rid of the idea that the shear tie, stringer is optimally designed for strength. There are areas of primary structure that are literally over-designed by a magnitude of 5 or more times. The secret is to know where is over-design is.

Back to DER: “A DER may approve or recommend approval of engineering technical data within the limits of their authority by means of FAA Form 8110-3, Statement of Compliance with the Federal Aviation Regulations.” Or as commonly put he is delegated the authority to approve data.  Talk about double talk “engineering technical data” when is engineering data not technical? He only cares about aircraft safety and factually justifying it. He doesn’t care about producibility or maintenance costs or schedule because that is not his FAA charter.

A DER is not an inspector or mechanic; he only approves technical data.

What is engineering technical data?

A&P mechanics see it as drawings, manuals, bulletins, or Technical Orders. Airworthiness Directives, Test and Stress Reports, specifications, processes, procedures, etc are engineering technical data.  Engineering writes the manuals that A&P mechanics follow be it from any source as long as it is approved by the FAA usually by an OEM or a consultant DER.

There are derivatives that others write based on approved engineering technical data that may be translated into work orders or jobs.  Engineering and therefore DERs are moving (being nudged by the FAA) into this business too.  I guess the FAA has lost faith in the translators? Remember translators have no authority so be careful using their data. An airline may have a FAA approved process allowing qualified personnel to “translate ” approved data and therefore following the planning is acceptable because it is following FAA approved data via an FAA approved process.

14 CFR § 183.29 defines the privilege for appointments in the following technical fields:

(1) Structural Engineering

(2) Powerplant Engineering

(3) Systems and Equipment Engineering

(4) Radio Engineering

(5) Engine Engineering

(6) Propeller Engineering

(7) Flight Analyst

(8) Flight Test Pilot

(9) Acoustical Engineering.

to list some and even these delegations can be limited within these fields.  This is why you may need more than one DER.  An example may be an antennae installation through a pressurized skin.  You would need DERs delegated with Structure Design and Damage Tolerance, Systems and Equipment Electrical and maybe an Acoustical DER.

“A DER offers technical expertise with state-of-the-art knowledge. An FAA specialist understands the framework of critical regulations that allow technology to be applied.”

DER Categories.

a. Company DER.

An ACO may appoint an individual to act as a company DER for his employer. A company DER may only approve, or recommend approval of technical data for the company. If a company DER is assigned to work in a consortium, business arrangement (such as using other company’s DERs), partnership or licensing agreement, the DER’s managing office will define the limits of the DER’s authority.

b. Consultant DER.

An ACO may appoint an individual to act as an independent (self-employed) consultant DER to approve, or recommend approval of technical data for a client. This DER usually has no geographical boundary or aircraft limitation.

DERs are only required for Major Repairs and the A&P mechanic makes the decision whether or not the repair is a Major Repair. Unlike engineers, DERs are a source for approved data and don’t answer to the A&P mechanic nor FSDO or MIDO.  A DER answers to the FAA ACO.

An analogy would be the DER is the surgeon, the engineer is the doctor, the A&P mechanic is the Registered Nurse, assemblers are the CNAs, etc.

I know a DER that made one phone call and instantly had two mechanics dismissed. Another time FSDO inspectors were fired. You see, a DER should know when a FSDO inspector is outside FSDO’s charter and by going through his congressman FSDO addressed the issue. Don’t think DERs do that for a living, FSDO is usually just fine but there always a few poor apples in the barrel. Except for DERS, we are perfect, just ask us.

So what is the ACO?  is for next week and we will get to SHIMMING soon

CALLAHAN AIRCRAFT SERVICES, LLC CURRENT PROJECTS:

CONVAIR 440 AIRBORNE PLATFORM ANALYSIS & APPROVAL
SUPER CONSTELLATION REBUILD REPAIRS APPROVAL
GULFSTREAM III AIRBORNE PLATFORM ANALYSIS & APPROVAL
402B UPPER WING WALK REINFORCEMENT REPAIR DESIGN, ANALYSIS & APPROVAL
402C ENGINE MOUNT SHIM REPAIR STC / PMA
E170 & E190 SLAT TOOL JIGS AND CHECK FIXTURES DESIGN, ANALYSIS & APPROVAL
KING AIR “EYEBROW WINDOW” STC / PMA
KING AIR WING ROOT SPAR CAP CRACK AD 89-25-10 AMOC REPAIR DESIGN, ANALYSIS & APPROVAL
KING AIR UPPER AND LOWER EXTERNAL AVIONIC PLATFORMS STC / PMA
ALL COMPOSITE CARGO CONTAINERS STC / PMA
MISCELLANEOUS REPAIRS DESIGN, ANALYSIS & APPROVAL

O x y m o r o n s

BALANCED FEDERAL BUDGET

Words of Wisdom and Warning

“If a republican government fails to secure public prosperity and happiness, it must be because the citizens neglect the divine commands, and elect bad men to make and administer the laws.”
Noah Webster

Aged to perfection

As we grow older and wiser, we talk less and say more.

But y’all, DERs do take questions and are on the same team.  Most DERs are comfortable in their role and don’t mind giving 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