Aircraft Accidents and the Landing Circle

Articles in several aviation magazines drew attention to a funded project called the Endless Runway:

It is a circular runway, three kilometers (1.86 miles) in diameter with a circumference of 9.42 kilometers (5.85 miles); it encircles the entire airport, taxiways and terminals.  Access for trains and vehicle traffic is through a tunnel system under the runway enclosure.

It’s definitely a twenty-first century concept; I find the idea – in my opinion – to be incredibly simple in its design while being reckless in its execution.  Don’t get me wrong, the runway probably does what its designers say it will: there is an economy of real estate; good utilization of approach/departure despite which way the wind blows; and an avoidance of rerouting to alternate airports due to crosswinds.  I’m not a pilot, so my concerns aren’t directed at the pros and cons experienced by flight operations.

I’m a mechanic, and think as such.

Thirty-five years ago, I drove a tall Grumman courier truck between Mineola, NY, and Newark-Liberty airport, roughly forty miles; this particular truck was designed for short, low speed delivery routes, not long haul, interstate drives; it was used to transfer late freight that missed the container transport vehicle.  The Grumman was loaded as expeditiously as possible, meaning the vehicle became top-heavy.  With a narrow wheelbase, the truck was very hard to handle when changing lanes or making turns because of the high center of gravity.

I watched the proposal video showing an A380 capturing the runway and beginning its rollout.  If anyone has had the pleasure of being in the cockpit as your airliner lands, it’s interesting.  During high arrival/departure times, the pilots execute a Hi-Speed taxi; this is where the aircraft lands and must expedite to the nearest taxiway to clear the runway for arriving/departing traffic; it’s not landing speed, but it’s fast.  Under the best conditions, you can feel the entire fuselage fight the desire to keep going forward while the nose gear turns right or left.  My experience with Hi-speed taxis have been on narrow body aircraft, e.g. 727, 737 and DC-9, airliners that are low to the ground.  Most older narrow-bodies react more favorably to these forces than one with a high center of gravity, e.g. 747, A380 or any aircraft with a high gear profile accounting for wing mounted engines, which is … just about any airliner these days.  Wide-body aircraft can weigh in excess of 500,000 pounds, landing at 130 knots or more; that’s a lot of inertia to account for.

Add weather in the form of snow, rain and/or ice, and the forces acting on the aircraft should be a reminder of why aircraft rollout in a straight line.  During these weather conditions aircraft employ anti-skid on a level runway to keep from sliding sideways; this means, on the main gear trucks, a wheel that ‘locks’ due to sliding on ice is hydraulically ‘released’ along with its opposing wheel to prevent a skid.  This device may not work as efficiently on a circular runway that centrifugal force acts to move outward.  The designer has engineered an inward angle to the runway, which forms centripetal forces toward the center; this may nullify or exaggerate the condition.  It also raises another issue: wing strikes, which I’ll address shortly.

Again, I’m a mechanic, so let’s look at the effects on the aircraft.  An aircraft is designed with side load stresses built into the landing gear.  I’ve swapped out landing gear on 727 and DC-10 aircraft; the gaps built into the various joints and rotating mounts are minimal, as thin as a .001 inch of gap.  There is no slop in a landing gear’s mount in aircraft that normally move in linear motion, straight ahead.  However, introduce consistent side loads where centripetal and centrifugal forces act against the straight line; stresses not designed into the aircraft may not be redesigned in an affordable or safe manner.

A top heavy fuselage, e.g. a cargo airliner, wants to move in the opposite direction as the turn; let’s not forget Sir Isaac Newton’s first law of motion: “… An object in motion continues in motion with the same speed and in the same direction, unless acted upon by an unbalanced force.”  The ‘unbalanced force’ is often the gear and the tires, each wanting to follow the curve of the circular runway.  All tires, whether the airliner has six or eighteen, will also have to be modified to withstand the enormous side loads.  The results of these loads may not be evident immediately, but will surface over time and, perhaps, catastrophically.

I can’t get any information on the runway’s in-sloping angle, but best guess is it’s about a fifteen to twenty degree slope taken from the animation.  My second concern deals with wing strikes; the video shows the right main gear, if touching down wings level, would allow the left wing and winglet to strike the runway.  The video shows the A380 banking on approach and touching down on a matching side angle of fifteen to twenty degrees.  The departing flight matches the incline until its wings are clear of the runway and level flight can be achieved.  But airliners are designed to wings level landings; they may hit the runway at a bank and/or nose left/right of center while fighting a crosswind, but the manufacturer’s design is what the onboard computers operate under.  In my mechanical opinion, it is too easy for a wing or outboard wing-mounted engine to come within striking distance.  Entire landing procedures, from a programming standpoint, would have to be rethought and redesigned for each airliner.

And then there’s one last point: Run off.  Runways are designed to drain different forms of contamination, e.g. snow, de-icing fluid, away to the sides; this is to encourage run off on a 262-foot wide runway, away from the centerline.  Rain can cause hydroplaning; its ability to flow easily would allow quick run off on a runway that is angled fifteen to twenty degrees, assuming, however, that the temperature remains above freezing.

The circular runway requires water to travel more than twice the distance to one side, allowing for the extra width – as much as twice the width of a normal international runway of 262 feet – built in for centripetal forces.  Glycol and propylene glycol are used in de-icing and anti-icing fluids; they are more viscous – resistant to flow; this allows them to stay on the wings during taxi to prevent ice/snow build up; they are shed during the take-off roll as the aircraft gains speed.  Where the de/anti-ice fluids end up are on the runway.  This would prove to be a traction safety concern for both landing and departing aircraft if the fluids can’t be regularly removed to an acceptable limit in between flights.

Urea is also a concern; where glycol products are used to de/anti-ice aircraft, urea, and like substances, are used to prevent snow/ice build-up on the runway’s surface.  Again, this needs to run off naturally or be removed frequently.  Urea can affect the safety of arriving/departing aircraft, but also can affect the integrity of the aircraft itself; its damaging effects are a concern to the aircraft’s structure and exposed areas.

From an accident investigator’s point of view, I see as-of-yet unimagined errors that can happen to man and machine.  I hope the issues can be worked out; the design is interesting and probably will benefit the aviation industry.  But its simple concept may prove more difficult to overcome than we are led to believe.

Aircraft Accidents and Lessons UNlearned I: Air Midwest 5481

The purpose of National Transportation Safety Board (NTSB) accident investigations are a chance for understanding; if they concentrate solely on closure and not on lessons learned, then the transportation disaster only becomes more tragic; the aviation industry gains no knowledge to prevent a similar accident from taking place; the tragic events will re-occur.

The ‘product’ of the NTSB is its reports, results of painstaking investigating into an accident.  The most important parts of the accident report are the Probable Cause and the Recommendations.  Trivializing the Probable Cause and/or the Recommendations out of a rush to meet a deadline is wrong.  Trivializing because one doesn’t understand the facts is unforgiveable.

To make my point, let’s use an imaginary airline: Brand X; and an imaginary aircraft: ABC Aircraft’s Zeta-1.  If a Brand X Airline’s Zeta-1 crashes, the NTSB accident report must outline why that Zeta-1 crashed.  If the accident was attributed to something that goes beyond Brand X and the Zeta-1, e.g. approved procedures were not followed, then the airline industry itself faces a safety crisis; the accident report must prevent any further Zeta-1 crashes for all airlines and operators, not just Brand X; it must also prevent accidents that stem from people not following approved procedures.  To do this, the NTSB must understand the airline industry and what contributing factors, whether due to weather, pilot training, manufacturer design or maintenance, led to the accident.  Otherwise the accident report is useless.

Aside from the tragic loss of life, the Air Midwest (AMW) 5481 accident’s findings proved that the most important contributors to the accident were lost in all the ‘expert’ talk.  The NTSB focused the investigation on the obvious problems, while ignoring the fundamental issues at the core that dealt with management at both the Repair Station and the airline.

The air carrier, AMW, contracted with Part 145 repair station, Raytheon Aerospace (RA) to perform maintenance on AMW’s fleet of Beech 1900Ds; both companies made many mistakes at the management level, e.g. tracking mechanic training, violating the Federal Aviation Regulations (FAR) and being selective with maintenance manual references.  What followed was an amateurish shell game – albeit, well-played – where management for AMW and RA diverted attention away from many important safety concerns.

From the first hours after the accident on January 8, 2003, to the NTSB Hearing in May 2003, the Maintenance Investigatory team (MIT) was misdirected by the airline from who was responsible and for what, e.g. who the mechanics worked for and who contracted maintenance services to who.  The Huntington, West Virginia hangar’s decision to ignore the FARs and their approved procedures crippled their effectiveness.  When an accident would occur was only a matter of time.

Why RA’s and AMW’s misleading succeeded was due to the NTSB management’s unfamiliarity with the commercial aviation industry, in this case: the airline system.  For decades the NTSB employed a staff made up mostly of engineers; qualified engineers in their own wheelhouse, but ignorant of an airline’s maintenance organization culture.  These staff specialists eventually migrate into the NTSB’s management, making investigatory decisions without a clear understanding of how the airline industry works.  And that is the NTSB’s Achilles’ heel; they lack a basic understanding of the industry they investigate.

The Air Midwest accident report succeeded in determining what ‘caused the’ accident; however the report failed to discover ‘the cause’ of the accident.  Air Midwest 5481 crashed due to several problems, both specific and systemic, e.g. limited elevator authority due to an improper rigging of the elevators was specific to that aircraft; the accident may not have happened if another aircraft replaced it on the line that day.

But ‘the cause(s)’ of the Air Midwest 5481 accident – major contributors to this disaster – are systemic, e.g. the aircraft being out of center of gravity limits.  This issue may not have been discovered if that particular aircraft hadn’t been used on that particular flight that particular day; the problem was probably occurring on multiple aircraft on that ramp.  This individual aircraft whose problems extended to unsafe maintenance practices was key to discovering that loading aircraft out of center of gravity may have been more frequent than realized up until then.

What is also systemic?  The circumstances that led to the unsafe maintenance practices; the elevators being rigged incorrectly to begin with; this is even more crucial than the center of gravity problem because how it became incorrectly rigged was mostly ignored by the report. The NTSB, in pursuing what ‘caused the’ Air Midwest 5481 accident, ignored ‘the cause’ of the accident; a cause that could have resulted in similar problems occurring at another airline … and did.  The AMW accident was a result of maintenance-culture intensive problems.

This is most evident in the writing of the Probable Cause(s) and the Recommendations.  The Findings mention the problems experienced by AMW’s and RA’s confused relationship and control of the maintenance workforce, but the accident report trivializes the importance of the problems.  In its Recommendations, the NTSB managed to reword FARs that had been written years before, yet were ignored by the airline, e.g. FAR 121.369: Manual Requirements, or 121.371: Required Inspection Personnel.  Reminding the industry about decades-old regulations do nothing to improve safety; instead, it shows a complete lack of understanding of what is necessary to ‘fix the problem’, or in this case … problems.

AMW and RA conducted heavy maintenance in five different hangars of which Huntington, WV, was one.  Each hangar followed the same procedures, each with the same systemic problems: opportunities to stray from the procedures and FARs that led to the Air Midwest 5481 accident.  Air Midwest flew forty-three Beech 1900D aircraft; they routed their fleet through these five hangars for everything from daily checks to heavy Detail inspections/maintenance.

When the MIT discovered that the accident aircraft’s elevators were rigged incorrectly at Huntington, that AMW and RA did not follow the approved procedures and FARs, then any rigging procedures performed in any of the five hangars over the contract’s history were suspected to be unsafe and out of limits.  Riggings included in the installations and operational checks of engines, doors, landing gear and flight controls, e.g. ailerons, flaps, elevators, and rudders, on all forty-three aircraft.  These should have been checked fleet-wide.

Instead, the NTSB reworded the FARs.  The push to put out a report ignored the fundamental point of the accident investigation: If one airline could neglect the FARs and their approved procedures, then another airline could do the same thing elsewhere.

Important lessons were not learned; the tragic circumstances re-occurred; similar problems existed elsewhere.  And on August 26, 2003, 231 days later, another Beech 1900D crashed, under similar conditions, in the north Atlantic.  Why?  Because the approved procedures were not followed.

Aircraft Accidents and Teaching to Fish

First, my apologies; I missed last week’s blog.  I was attending my older son’s graduation 1300 miles away.

Second, my apologies to Anne Isabella Ritchie whose quotable expression I don’t intend to mutilate.  In her book: Mrs. Dymond, she originated a phrase using these words, “… if you give a man a fish he is hungry again in an hour; if you teach him to catch a fish you do him a good turn.”  Today it is worded: ‘Give a man a fish, and you feed him for a day; show him how to catch a fish, and you feed him for a lifetime.’

What does that have to do with anything?  Since I’ve returned to teaching, I have been trying to help aviation professionals understand the true nature of aviation accidents.  The National Transportation Safety Board (NTSB) has been tasked for decades with discovering what caused (verb) an accident.  The aircraft crashed due to some reason, they seek the reason(s); whether it was mechanical or pilot-driven, the NTSB will find what caused the disaster.

But only of that particular disaster.

What the NTSB won’t do, on most occasions, is look into the cause (noun) of the accident.  It is my intention to teach these professionals that an accident isn’t just a sum of its parts, but the depth to which it must be analyzed.  In other words, I can hand these people the reason(s) an aircraft crashed and that will give them a brief closure.  Or, I can teach them to look further into events than the NTSB normally goes and these professionals can prevent many accidents in the future.

On August 2, 1985, a Delta Airlines flight 191, an L1011 crashed in Dallas, Texas, due to wind shear.  The disaster prompted increased training for pilots across the board to recognize wind shear and how to fly out of it.  That was what caused (verb) the accident: the airliner entering wind shear unprepared.

On July 2, 1994, US Air flight 1016, a DC-9 crashed outside Charlotte, North Carolina airport due to a wind shear event.  An airliner entered a nearly identical situation as Delta 191, nine years later.  What came out of Delta 191 was increased training and a plan to modernize weather tracking technologies.  What didn’t come out was a major cause (noun) of the accident: a lack of procedures to deal with approaches into wind shear, in this case during the time between 1985 and when the new technology was up and running.

The airline industry was handed a fish when what they really needed was to be taught how to fish.  Accident history is filled with disasters that focused on ‘what-caused-the’ and not on ‘what-the-cause’; from the Titanic to the Challenger.

It’s a stretch to align my plans with the ‘give a man a fish’ adage, but the point is important.  One thing the NTSB does concern itself is with numbers; the greater the attention an accident receives, the more they will devote resources.  However, the people I instruct are involved with General Aviation (GA) or small repair stations; they will never deal with tragedy on the scale of a TWA 800.

But that doesn’t mean that the single-pilot accident that claims a father of three isn’t as important to the widow or orphans as any major accident.  Each accident is an opportunity to prevent another.  And if the resources aren’t dedicated to finding this single-pilot’s cause of the accident, then that family will only be the first to suffer a loss due to possibly the same cause.

Resources come in many forms: technical expertise, experience, analytical qualities, or even a fundamental understanding of Physics.  They are all Fish given to the aviation professional in their earlier days.  Now it is time to teach them how to use them.