Aircraft Accidents and Getting It Wrong

When I was young, I had a Long Island Newsday route, flinging papers from the basket attached to the front of my blue Schwinn Sting Ray bicycle’s handlebars. Folding the papers, I usually read the headlines, perhaps a few paragraphs, to see what was going on. In those days, the newspaper’s first pages were just that: news. Reporters did not write opinion, speculation or political views. They wrote news.

The amazing thing about this decade is we read everything but news. Political parties have the integrity of a reality show, e.g. Jersey Shore or Here Comes Honey Boo Boo, to name a few. ‘News’ anchors – not opinion talk show hosts – lay naked their political leanings. Gone are the days of Huntley, Brinkley and Cronkite. Today, the ‘News’ doesn’t deal in facts, at least none that aren’t part of the dialog at the time.

On October 29, 2018, Lion Air flight 610, a B737MAX, crashed into the Java Sea. On March 10, 2019, Ethiopian Airlines flight 302, a B737MAX, crashed on land shortly after takeoff. Both flights appeared to suffer from similar events – not identical – but similar. One thing I learned as an aircraft mechanic was that: until facts are learned from troubleshooting, coincidences sometimes are just that: coincidences.

The 737MAX accident similarities, 132 days apart, were too much for the media to ignore; they guessed away, especially when pointing fingers at Boeing and FAA Certification. Speculation flew from ‘experts’ and anyone who had an opinion, based on nothing but hearsay and personal grandstanding; the most vocal were those whose technical knowledge of the Boeing 737MAX – indeed, of any airliner – was nil. The guesswork came mostly from those who, in addition to not knowing the aircraft, had never worked for an airline; people who could not understand the hazards that working on a ramp presented.

There were those few on social media who said, “Let’s not speculate. Let the industry learn from facts, not what the barbershop-version of expertise think happened.” They were called arrogant, disrespectful, full of themselves. One ‘expert’ said, “Speculation was every aviation enthusiast’s right.” Incredible.

That was until April 10, 2019, when Aviation Daily, in an article titled: Ethiopian Crash Data Analysis Points to Vane Detachment. Meanwhile, the investigation, despite this early revelation by an investigator involved in the investigation, still moves forward. But what a show-stopper!

The Aviation Daily article stated, “This, says one source, is a clear indication that the AOA’s [angle of attack] external vane was sheared off – most likely by a bird impact.” What does this mean? The AOA departed the aircraft BEFORE the accident. An important sensor that senses the aircraft’s attitude, was lost and possibly caused the accident … sort of like Air France 447, where the aircraft received conflicting airspeeds from sensors before the crash. The source stated that a bird struck the left-hand (L/H) AOA vane. The odds of Lion Air 610 suffering the same event are astronomical: a bird strike that took out either AOA, then upset the B737’s Maneuvering Characteristics Augmentation System (MCAS).

However, the damage was done. Speculators caused irreversible damage to the Ethiopian Airlines and Lion Airlines accident pilots, Boeing, the FAA Certification group, and anyone who fell under the speculation target. Even people, self-pronounced ‘experts’ in other industries were slandering Boeing or the FAA, based on hearsay and not on factual information.

I get it, accident investigations are frustrating; patience is not easily tolerated. Investigations are tedious. I’ve dug through boxes of decades-old maintenance records, an aircraft’s lifetime, looking for the silver bullet. I have interviewed countless mechanics, trying to find the General Maintenance Manual error that sparked a lapse in procedure. I observed many hours of maintenance checks and phase maintenance simulations to find why a work card led to a mistake. But I never ignored facts and rushed to conclusions … no, no, no. Why? Because it destroys hard-earned reputations. Jumping the gun wrecks innocent people’s lives. Posturing for the cameras detracts from the integrity of the accident investigation, can even divert attention away from the root cause, which can put us all in danger.

But the most important reason: Feeding unfounded theories to the accident victims’ grieving families is cruel and so very selfish. ‘Experts’ may excuse the practice as “helping the families find closure” … that is, until the ‘experts’ are, often enough, wrong. They only munch a slice of crow, lay low for a while before landing another News ‘expert’ gig. But the accident victims’ grieving families get to live the heartbreak over and over and over again; directing their rage, often at the wrong party.

How does diverting attention put us all in danger? Remember Atlas 3591? An Atlas B767 aircraft, flight 3591 crashed on February 23, 2019, outside of Houston. For the fifteen days before Ethiopian Airlines 302, Atlas 3591’s mysterious plunge occupied the news. But then the second 737MAX accident shoved Atlas Air 3591 to the background, even though B767s, filled with passengers, fill the sky today. Has the industry followed the latest from the National Transportation Safety Board (NTSB) updates?

Remember American Airlines flight 191? The authorities originally focused on the DC10, instead of on American Airlines’ unapproved maintenance procedures. How long did it take for the NTSB to check if American was using similar procedures on their other airliners, e.g. B747? That’s distraction.

What does working on a ramp (as mentioned in paragraph four) have to do with anything? The L/H AOA sensor is located one foot behind the radome, on a level with the pilot’s feet. Since a damaged AOA sensor causing the accident has a high probability, could a bird knock it out? That’s a low probability – even infinitesimally improbable that it happened on both 737MAXs. Bird impacts have played into many accidents, but ramp activity is more likely. Equipment movement, e.g. ground power units, air conditioning units, air carts, air stairs, catering trucks, even baggage carts, can be hazards around aircraft, especially where time-sensitive turn-arounds occur.

But wouldn’t anyone who damages an aircraft be quick to report the incident? In earlier years, airlines in the US were quick to fire anyone who damaged an airliner, that is, until management discovered that people would damage the plane and then not report it. So no, they might not report it.

In 2010, a belt loader punched a hole in a US-based regional aircraft, compromising the pressure vessel. The plane, full of passengers, took off, but could not pressurize in flight. The plane landed safely, but it should never have taken off with the damage it incurred. For decades ramp activity has caused millions of dollars in damage, lost flights and affected the safety of flying aircraft. Improper equipment movement has damaged wing leading edges, static ports, engine cowls, cargo door thresholds and entry doors. Is it possible that an AOA vane could get damaged in this way? It is very possible, more so than a bird strike. It certainly deserves attention and fact-finding.

The Ethiopian authorities have not finalized their report; the L/H AOA sensor’s departure is still a serious working theory. However, if it proves out, the Speculators have done a great disservice to the industry; they have distracted from the root causes, caused unnecessary harm and wasted everyone’s time. Journalists may someday regain their integrity … maybe. But as for speculators, we are stuck with their useless opinions that aren’t worth the paper they should not be printed on. �](>

Aircraft Accidents and Lessons Unlearned XXIV: British Airways PLC 5390

This month’s Lessons Unlearned looks at a decades old accident, which resulted in zero fatalities. The end result could have been worse, if not for the fast thinking of the first officer. The quality of the British accident report is so different from an American report; the writing style is Elizabethan; no words are wasted or misused. Most importantly, the investigators understand what they are investigating; they know the subject matter, e.g. aircraft maintenance, thoroughly and communicate the problems without leaving any doubt.

On June 10, 1990, British Airways Public Limited Company flight 5390 was a scheduled flight between Birmingham, England and Malaga, Spain. The aircraft was climbing from flight level (FL) 140 (14,000 feet) to FL 230; the co-pilot (first officer) manned the radios while the commander (captain) flew the aircraft. The captain had just released his shoulder and lap belts when the aircraft suffered an explosive decompression; the L-1 windscreen directly in front of the captain departed the aircraft. The captain? He was forced into the new hole by the higher cabin pressure and became wedged half-in/half-out of the windscreen hole; from the waist, up, he was on the outside.

This was not a manufacturer design issue; it was a maintenance issue. The root cause was also discovered with enough time that it should have prevented other accidents – and, yet, did not. This is what makes accident investigation so frustratingly unproductive, the waste of opportunity and learning.

The airliner involved, a British Aircraft Corporation (BAC) 111 was a twin-engine, short-range airliner; it resembled a shorter version of the DC-9, with design basics similar to most airliners, meaning: as it climbs or descends, the BAC-111’s fuselage acts like a rigid balloon. The cabin pressurizes/depressurizes to provide the crew and passengers enough atmosphere to survive high altitudes, keeping the occupants from asphyxiating. Depending on the altitude, the differential pressure (DP) within the aircraft is proportionally higher than the air pressure outside the aircraft.

If all hands survived and the aircraft landed safely, why was this an accident? According to Title 49 code of federal regulations 830.2, “Aircraft accident means an occurrence associated with the operation of a aircraft which takes place between the time any person boards the aircraft with the intention of flight and all such persons have disembarked, and in which any person suffers death or serious injury or in which the aircraft receives substantial damage.” This reference applies to US law, but international law definitions are/were similar.

The accident report estimated that the captain was forced out of the cockpit with the equivalent of 5,357 pounds of pressure. At 17,000 feet of altitude, the DP between the aircraft’s interior and exterior was far less than, e.g. the DP of China Air 611 at 35,000 feet; China Air 611, a B747, suffered an in-flight structural breakup from explosive decompression. This does not trivialize flight 3590. It emphasizes that the windscreen’s departure did not occur at the BAC 111’s upper DP range; a minimal amount of DP ejected the windscreen. At 17,000 feet, it is estimated the window had only 8.77 pounds per square inch of air pressure pushing outward on the windscreen.

The window was secured by 90 countersunk bolts secured into #10 Kaylock anchor nuts. Of these ninety bolts, thirty were recovered, either with the window or in the aircraft windshield frame. Eighty-four bolt shanks were 0.026 inch narrower than the anchor nut’s width while six bolts were 0.1 inch too short. The eighty-four bolts with the wrong shank width did not have the thread depth to engage the anchor nut threads. These bolts slid out with minimum resistance. The six short bolts had the correct thread width yet did not engage enough of the threads for security. Though more stable, they were six bolts doing the job of ninety.

Flight 5390 was the first flight following the replacement of the previous L-1 windscreen. There was no doubt as to the probable cause of the accident: incorrect fasteners. What was more important was the root cause: the maintenance practices employed at British Airways. There is much to be written about the torques used; how the bolts were torqued and the differences between fine and coarse threads. However, these matters stray from the root cause.

Due to Flight 5390’s non-fatal status, its successful landing worked against its lessons learned; nothing is more disinteresting to sensationalists than a close call. Because the public rapidly lost interest, the story quickly became unattractive. However, this is a mistake that plays over and over in aviation safety. For instance, cargo aircraft accidents usually attract less attention due to the low number of fatalities, yet the accidents occur in equipment flown by major passenger airlines. On February 23, 2019, Atlas Air flight 3591, a B767 cargo airliner, mysteriously crashed. It was soon forgotten in the wake of two B737-MAX accidents, even though the B767 is flown extensively by the Big Three: Delta, American and United.

A random check of British Airway’s and other airlines’ BAC 111s found multiple errors in the manufacturer number for the windshield bolts being used. This fact should have raised concerns, not only with British Airways, but with many airlines, particularly those following similar maintenance programs. In addition, per the accident report, post-maintenance pressure checks were not required on the BAC 111 following a windscreen replacement. How could British Aircraft Corporation not require a pressure check on a replaced windscreen’s integrity? How many other aircraft had questionable return-to-service checks?

Because of workloads and available mechanics, the maintenance manager took it upon himself to work the windscreen replacement; this is where an experienced airline maintenance investigator shows his/her particular advantage to an engineer. This culture displayed many problems someone with a mechanic background could easily have identified, e.g. human factor issues; manpower; distribution of work; familiarity of the aircraft; effectivity differences of one BAC 111 to another BAC 111 and the pressure to meet a flight. These are the risk factors, that when lined up, lead to disaster, as it did for Flight 5390.

Both the shift supervisor and the avionics supervisor – both management, not workforce – replaced the windscreen. After determining the removed bolts were damaged, the shift supervisor searched for replacement hardware (bolts) in an uncontrolled hardware carousel. He found the narrow bolts and used them to replace the old hardware. The two supervisors then used uncalibrated torque tools to torque the windscreen bolts. Similar errors were made fifteen months later (September 1991) that led to the Continental Express (Britt Airways) Flight 2574 accident near Eagle Lake, Texas.

Although the Birmingham maintenance area manager dedicated 80% of his time focused on Birmingham, “The Area Manager did not monitor the day-to-day work practices of his subordinates, but relied on the trending of parameters such as numbers of Acceptable Deferred Defects, repeated defects and failures to meet schedules as indicators of quality.” This disconnect began to manifest itself years later in accidents, e.g. Air Midwest 5481, where the station manager worked different shifts from the workforce, disqualifying himself from the actual work and relying instead on data parameters. The Federal Aviation Administration itself, risks falling into this trap, relying heavily on data retrieval and avoiding good old-fashioned surveillance.

British Airways 5390 was due to a windscreen installation; Air Midwest 5481 was due to elevator rigging errors; Britt Airways 2574 occurred because of communication breakdowns and a failure to follow the job. However, the lessons unlearned are the same: a lack of maintenance job familiarization; a rush to get the job done and training issues. More importantly, the communication of lessons within the industry, both domestic and international, is key to preventing similar accidents. Operations accident causes are easily communicated; pilots talk, even outside their airline. Airworthiness accidents are not communicated as well, at least not outside one’s own airline. To depend on accident investigation bureaus, whose attention is focused on the tragedy, e.g. victim numbers, and not on the lessons to be learned, is a recipe for failure and the reoccurrence of events that should never have reoccurred.