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Glenn Armellino MS, PE

Glenn Armellino MS, PE

In Aviation Engineering, If You Don’t Build It Right, You Need to Fix It Right

How experience and smart engineering can simplify the problem and lead to the solution.

As an aircraft and aviation subject matter expert, my clients look to me for a precise understanding and a technical explanation of what went wrong in the case of an aircraft accident or an airline disaster. It’s imperative to accurately interpret the data and be able to explain those facts in a way that is relevant and makes sense to a judge or a jury. Especially in the aviation engineering field that requires so much hands-on training and experience, those who have this complete skill set are few and far between.

My experience in the aviation industry in aviation engineering has taught me many things, and I’ve been very lucky to have worked for some of the greatest aircraft manufacturing companies in the world. As an example, understanding how to evaluate a problem and recognize a potential solution is one of the most valuable lessons I’ve learned. And while every position I’ve ever had has contributed to this mindset, the time I spent serving as a contractor with Gulfstream Aerospace Corporation (GAC) in Savannah, GA had a profound impact on the way I approach and analyze engineering challenges.

The Gulfstream G650 Business Jet

Working at Gulfstream taught me two things:    

  1. How to build things right the first time, and 
  2. How to fix it in the unlikely event something does go wrong

My first contract was in the Systems Stress Group on the incredible G650 business jet.  

I arrived shortly after the official program launch, and it was my first ‘drawingless’ aircraft, and Gulfstreams first as well.  The thought was that so-called ‘model based definition’ using Catia v5 should work for us, and it certainly did.  Catia has endless capability, one of which is the ability to animate actuators functioning, linkages moving and control surfaces (in this example, doors) opening and closing.  But it is so ‘beautiful’ that it can give a false sense of security.

First flight of the G650 on November 25, 2009 resulted in a problem with its landing gear doors.  This was by no means a life-threatening in-flight aviation problem, but it was one that required serious attention, nonetheless.  When the landing gear is retracted, two doors close and fit tightly to the underside of the fuselage, creating a smooth profile through the airstream.  During takeoff and landing, the gear is extended and these doors are open, of course, and the aircraft must fly for a relatively short time in this ‘aerodynamically undesirable’ state.  

The certification of an aircraft involves an extensive FAA approved flight test plan which restricts altitude, speed, range etc. until a full Type Certificate is granted.  One of these restrictions is to not retract the landing gear on the first flight for safety.  The G650 landing gear doors didn’t like this, and the test pilots reported a ‘shuttering’ sound forcing the aircraft to land prematurely during a highly publicized first flight.

This of course led to  wild speculation and rumor, creating two areas of concern.  One was the negative exposure, and the other was the aviation engineering.  Gulfstream handled the publicity so adeptly that the ‘problem’ was reduced to an ‘incident’ followed by an ‘occurrence’ leading to an ‘anomaly’ and ending with a distant memory.  Now for engineering.  This was also so efficiently handled that the distant memory remains exactly that.  

Getting Real

How did Gulfstream do that? How did they minimize what could have been a PR nightmare and delayed the certification process?  The answer is by getting real.

So many companies have a culture of blame, finger pointing and a philosophy of covering your own ass that serious engineering problems are never truly solved, but instead are continually patched and never really fixed.  Not Gulfstream.  Not Gulfstream. 

Two parallel efforts were immediately put in place, one that did involve retrofitting the one and only G650 main landing gear (MLG) door and fairing in existence, and the other that entailed a complete redesign.  I was not directly involved with either effort, but as far as I know, there have been no ongoing G650 MLG door and fairing problems to date.  The point is that it was fixed right the first time, by being honest and getting real.

The Gulfstream G500 and G600

I returned to Gulfstream in March of 2011, again in the Systems Stress Group, on the then classified P42 program, which ultimately evolved into the G500 and G600 business jets.  And even though my G650 door and fairing experience was a bit limited, I was tasked with analyzing the P42 main landing gear door and fairing. 

The preliminary design I was presented with was similar to the G650, but anything reminiscent of the G650 first flight ‘memories’ could not be risked.  I recall being somewhat surprised when granted a clean slate and allowed to experiment with virtually any design from the initially proposed G650-like composite co-cure to a G450-like sheet metal buildup. 

The G650 doors experienced high buffeting when open, making stiffness-to-weight driven modal frequencies a design driver.  Static and fatigue strength, parts count, system weight, reliability and maintainability and on it goes were all performance indicators, with cost being last on the list.  Making it safe and getting it right the first time was the priority, and this task had some profile.  

I was fortunate to work with and for some very skilled designers and managers, and after maybe three major design choices we agreed that a honeycomb co-cure was the way to go.  The complexity of these doors is quite significant, including a contoured outer and inner skin, machined core, heavily loaded actuator link and hinge attachment points, and the tendency of the door to pull away from the fuselage at high speed when closed due to aerodynamic forces.  

Now how do you prevent that problem? How do we make the door stiff enough to stay closed when it is closed without adding weight, altering natural frequencies and going right back to buffeting when it’s open? The answer lies in a pre-warp analysis, consistent with the industry-advanced engineering that Gulfstream delivers.

A Commitment to Product and Public Safety

The takeaway here is that a well-managed engineering company like Gulfstream almost always gets it right the first time, and in the rare instances when they don’t, they always fix it right the first time. This is more than just a company that strives for excellence, it’s a foundational value that they instill in their employees and their contractors.

It’s an ethos that can only be successful with a commitment to product and public safety, backed up with state-of-the-art aviation engineering expertise executed in an atmosphere based on honesty and integrity. In an industry where lives are at risk everyday, few companies have a greater obligation to people’s well being. But what’s truly special is that companies who embrace these types of core values also impart them into their people for the rest of their lives.

I consider myself lucky enough to be one of them. Imagine what the world would look like if all companies adopted such a practice.

Do you need an aviation engineering expert?

At Armellino Engineering, we specialize in aviation engineering and airframe structural analysis. We provide expert testimony and advisory services on legal and liability matters concerning aviation investigations, accidents, and disasters.

If you specialize in aviation law, please give us a call so we can be of assistance for your next case.

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