CERTIFICATION 3

February 27, 2012 by Dr. Airplane

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.

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

CERTIFICATION 2

February 20, 2012 by Dr. Airplane

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

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

CERTIFICATION 1

February 13, 2012 by Dr. Airplane

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

RULES OF THUMB AND OTHER MYTHS 6

February 6, 2012 by Dr. Airplane

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

“1.5 e/d is okay” is NOT a good rule of thumb

Working the B757 start up on unit three (I think), we had a manufacturing boo boo. The shop installed the skin rivets all around the emergency exit door cutout with 2.0 e/D. Isn’t that nice but when that barrel section went in for final company or FAA inspection it failed. Why? Because the drawing required 2.5 e/D edge margin.

We figured the skin cutout’s corners lost one third of their life. This means the probability of skin cracks was high after two thirds (20 years) of the B757 design life of 30 years. The Liaison and Stress engineers from both the vendor and Boeing agreed it was unacceptable. But not manufacturing who complained through the Boeing Chief of Design, Jim to the DER, Pete. They agreed it was acceptable and I was informed to “buy it off.” Little ol me, the peon sole On-site Liaison Engineer to the vendor was indirectly told to accept the damage as is.

Passionately I called the Boeing Chief of Design to tell him what for and heck no. He wasn’t known to be real nice to subordinates (remember the Peter Principle) but he was nice to me. Lucky for me I took a Boeing fatigue class (that my Lead informed me was a dumb thing to do) because Jim walked me through their decision process by asking me Boeing technical fatigue and historical maintenance issue questions. We had NO data on this never before completely fatigue designed aircraft! (You CHS engineers working for Tony pay attention) We were using Boeing’s DFR process for design and analysis for the first time. I answered his questions and he summed it by asking me if a crack IF it occurred on THIS aircraft would go UNDETECTED prior to a catastrophic failure (crash and burn).

The answer was “no.”

“And who is taking responsibility for it?”

“Rockwell,” the vendor I replied.

“And who would be paying for the repair?”

“Rockwell,” I replied.

He was willing to accept a low probability of a hit to Boeing’s reputation so I concurred on the acceptance on Rockwell’s paperwork.

The section rolled out, shipped, and received by Boeing in Renton just as I returned from my assignment. Boeing arrogance would not allow them to accept Rockwell acceptance so they wrote Boeing paperwork so Boeing accepted it. I was the turkey to approve the acceptance but this time the DER consigned. So much for the vendor taking responsibility. And a few years later Boeing bought that plant from Rockwell and therefore accepted the repair costs if any.

The point to that story is Boeing Commercial did use airplanes to make money not money to make airplanes like they do now.

A short comment about composite’s end or edge margin requirements. 2.5 e/d is the usual EM requirement but 3.0 e/d isn’t abnormal for graphite or fiberglass composite structure compared to most metals. I don’t remember the requirements for plywood (used on C-130) or wood laminates. Yes, they are composites too making the Wright “Flyer” the first all composite aircraft. Beech’s Chief Engineer Wells book on structural guidelines includes good data for wood and resins and I would go there first, maybe the DC-3 SRM or AN5 Handbook (Army/Navy predecessor to MIL-HDBK-5) second.

DERs are only required for Major Repairs and the A&P mechanic makes that 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.

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 and aviation professionals.

CALLAHAN AIRCRAFT SERVICES CURRENT PROJECTS:

Next week’s topic will be “what is a DER” and coming soon topics will include identifying a shear joint and why some engineers or ARs don’t explain requirements making one feel small. AND shimming

O x y m o r o n s

Click the ‘Start’ button to Shut Down the computer.

Words of Wisdom and Warning

“It is the duty of the patriot to protect his country from its government.”
Thomas Paine

Aged to perfection

Peace is when time doesn’t matter as it passes by.

Sincerely,

James W. Callahan

General Manager / FAA DER

DER@CALLAHAN.AERO

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

Dr. Airplane FAA-DER

Aircraft Structural Engineering in Plain English

Monthly Archives: February 2012

CERTIFICATION 3

CERTIFICATION 2

CERTIFICATION 1

RULES OF THUMB AND OTHER MYTHS 6

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