04-07-2018, 09:43 AM
Discombobulating auto-dependency & AIOS continues -
I see in the Oz that BB has tapped out an article which highlights that the serious safety issues of auto-dependency are still yet to be satisfactorily risk mitigated...
MTF...P2
Auto-pilots cut pilot experience
12:00amBYRON BAILEY
Computer-reliant planes may be making the airways safer, but emergencies expose pilot weaknesses.
Pilot experience reduced by flight automation
Last month was not a good month for aviation safety statistics.
A Bangladeshi airliner crashed on approach into Kathmandu with 71 fatalities.
A day before, a private Turkish Challenger 604 crashed into the Zagros Mountains 370km south of Tehran, killing all 11 on board.
Conflicting reports put the private jet in cruise at 36,000 feet one hour 21 minutes after leaving Sharjah for destination Istanbul when it suddenly climbed to 37,700 feet before entering a pronounced descent, then crashing. The black boxes — flight data recorder and cockpit voice recorder — have been recovered and should be able to answer the question of why this popular and safe large jet crashed.
I am interested because I fly a private Challenger 604. Its avionics and electrical/hydraulic systems place it in the small airliner class plus, as a wide-body type jet, and it is very comfortable for the rich passengers, giving the cabin a loungeroom feel. The passengers of the crashed jet were Mina Basaran, socialite daughter of a wealthy Turkish businessman, and seven of her female friends who were attending her hens party in Dubai — now playground of the rich and famous (Beirut is passe).
The crew of two pilots and one cabin attendant were all female and the captain was a former military pilot.
There are several possibilities that come to mind.
There were thunderstorms active in this area of Iran so could it have been like the Asian Airbus A320 that crashed several years ago when the pilots lost control entering thunderstorm activity.
Perhaps the captain was trying to climb over a thunderstorm and stalled because the descent was rather sudden, which may indicate loss of control.
Maybe they had picked up some ice on the wings — unlikely because the Challenger has excellent anti-ice systems but they rely on the pilots to turn them on. The B777 anti-ice systems, in contrast, are automatic.
The Challenger, which has a supercritical wing, requires careful removal of even the smallest amount of ice before takeoff in low temperatures. When first introduced into service it suffered several takeoff accidents.
Could it be a bomb on board? The descent was sudden and the crew allegedly reported a technical fault. Sharjah is more like a secondary airport that is popular with eastern European airlines, especially Russian. I cannot comment on its airport security.
Sharjah is a small emirate — one of the seven that make up the United Arab Emirates — and is overshadowed by its close, glamorous neighbour Dubai.
The reason the jet was parked at Sharjah was probably because of lack of room at Dubai International airport.
Maybe Iranian air traffic control played a part. Iran has notoriously suspect control and poor communications. I encountered a Russian IL76 military/commercial freighter reciprocal on the airway over Iran. I was in a B777-300 and, according to the EOWE (east odds/west evens) flight level rule, cruising at cleared level 32,000 feet on the way to Paris.
This bogey popped up at my level at 40 nautical miles on my traffic alert and collision avoidance system at my altitude, the wrong altitude, and Tehran ATC was not answering so I immediately deviated 5nm right to let it pass.
Then, of course, comes the human element. The biggest problem facing airlines and corporate aviation is a lack of manual flying skills because of the dumbing down of pilots. The Challenger 604, same as the Airbus and B777, is highly automated. Immediately after gear retraction on takeoff the autopilot is engaged.
Lateral navigation and speed are all programmed before engine start into the flight management system computers, which then fly the aircraft to the destination.
The approach at destination is normally flown by the autopilot after the pilots enter arrival and runway details into the computer. Late on final approach the pilot flying disconnects the autopilot and lands the aircraft.
What this means is, on a typical — for example, nine-hour — flight, the pilot is hands-on for only several minutes. This is safe as modern aircraft are so reliable that air travel is safer than driving a car. The problem occurs when something unexpectedly goes wrong and puts the pilots out of their comfort zone.
Pilots get to refresh their aircraft systems knowledge and emergency handling skills every six months in simulators. Qantas does this every three months for its pilots.
However, even in the simulator, most training is done with the autopilot engaged as it is more reliable to fly an approach, even with an engine failed, with the autopilot engaged.
What this means is if you put a pilot in a situation they have never encountered the lack of a solid basic flying skill will surface.
Take, for example, the Air France A330 that after pitot tube icing, suffered a pilot-induced stall at high altitude. The panicked pilot froze and without realising it held the aircraft in the stalled condition all the way down until it crashed into the sea.
Corporate aviation, same as airlines, is subject to the same tyranny of cost. Pilot training is expensive and the trend, especially overseas, is for crews is to be less experienced even though on paper they appear to be equally qualified.
As remarked recently by the hero of the Hudson River landing of US Airways flight 1549 in New York in 2009, Captain Chesley “Sully” Sullenberger, “There is no substitute for experience in an unexpected and difficult situation.”
The automation of modern aircraft has resulted in the dumbing down of pilots, with many lacking adequate manual flying skills. But I guess it is something that aviation has to live with.
Byron Bailey, a veteran commercial pilot with more than 45 years’ experience, is a former RAAF fighter pilot and trainer. He was a senior captain with Emirates for 15 years.
(12-08-2015, 09:43 AM)Peetwo Wrote: AIOS - & the 21st Century??
The (other) Big "V" said.. :
Quote:My dear Gobbles:
The problem, simply put, is one of discombobulation.
In a crisis, the respones of modern systems, the changing displays, the cavalcade of warnings, and the lack of "familiar cues", completely discombobulate the crews.
The fact is, regardless of the howls of protest from the techno-nerds that design them, and those who love them "on paper" when in their arm chairs, in the "real world" the systems are actually discombobulating, ( ie, they throw the crew into a state of mental uncertainty ) and as a result, in a crisis situation, the crews quickly become completely discombobulated.
The result, is needless disaster, after needless disaster.
The "industry" will however, never admit to this truth.
The industry has "acquired institutionalised ostrichitis syndrome" (AIOS).
So, stand by for regular repeats of AF-447 and QZ8501.
Clues:
confusion, befuddlement, bewilderment, puzzlement, perplexity, disconcertment, discomposure, daze, fog, muddle, etc ........
Love it "V" - The head in sand bit is absolutely spot on, especially here in Oz where we presently have a totally dysfunctional regulator & an irrelevant, "non-independent" AAI (Aviation Accident Investigator). An AAI that is now so busy being 'PC' that ironically they have become a regular part of the causal chain (holes in the cheese), rather than the chief safety issue identifier to help prevent/mitigate repeat occurrences/accidents.
The classic - but not isolated - example of discombobulation/AIOS (Aussie style ) is of course the PelAir investigation, & now re-investigation:
Quote:Example references: PelAir MK-I (& probably MK-II ) - Beyond Reason - & the pale?? + O&O thread
Quote:Senator FAWCETT: The thing that the committee is struggling to come to is that there have been many witnesses who are pointing fingers of blame at particular incidents. Australia has been a leader in aviation safety for a number of years through its fairly robust adoption of a systems approach, and James Reason is the classic person who has driven that. So, clearly, the actions of the pilot in command and his decisions around flight planning and fuel have a role to play—so do the actions of the company in terms of their checks, training et cetera. But each slice of the Swiss cheese, as the James Reason model is often laid out, has the potential to prevent the accident. So the importance that the committee is placing on an incident such as a proactive alert to the pilot that there is now a hazardous situation is not the reason the accident occurred, but it is one of the defences that may well have prevented the accident. If Australia are to remain at the forefront of open, transparent and effective aviation safety then one of the roles of this committee is to make sure that our organisations collectively keep working towards having a very open discussion around that systems safety approach and making sure that each of those barriers is as effective as it can possibly be. That, I guess, is the intent behind a lot of the questioning this morning...
However while all this AIOS is going on ( ), the rest of the aviation safety world is struggling to get ahead of the game with the implications of the findings of repeat tragic accidents like QZ8501, Colgan etc.
The following is an excellent (TY 4 link Tinkicker ) overview article of QZ8501, courtesy Aviation Week:
Quote:AirAsia Crash: Are Regulators Moving Too Slowly On Upset Recovery?
Findings in the Indonesia AirAsia Flight 8501 crash highlight lessons learned—but not implemented—from high-profile crashes in 2009
Dec 7, 2015 John Croft | Aviation Week & Space Technology
[/url]Indonesia is calling for the U.S., Europe and its own regulators to accelerate mandatory upset-recovery training for airline pilots in the wake of the Indonesia AirAsia Airbus A320-200 crash in December 2014. The accident has key similarities to the 2009 Air France Flight 447 and Colgan Air crashes in which pilots, for a variety of reasons, failed to properly respond to aerodynamic stalls and upsets, resulting in rapid, largely uncontrolled descents into terrain or water.
The 2009 accidents spawned a variety of countermeasures in the international community, with the International Civil Aviation Organization (ICAO) publishing new standards and recommended practices in November 2014 and the European Aviation Safety Agency (EASA) and FAA set to implement their version of training upgrades in 2018 and 2019, respectively. That is not soon enough from the perspective of the AirAsia crash investigators. Loss-of-control accidents, which are often preceded by a stall and upset scenario, are the deadliest types of airline accidents, representing only 2% of all accidents but 25% of all fatalities in 2006-13.
Flight simulators will be the tool of choice to combat loss-of-control accidents as upset-recovery training becomes routine. Credit: NASA
Along with a call for upset prevention and recovery training, the final report on the Dec. 28, 2014, crash also highlights how maintenance and pilot procedural flaws, crew resource management shortcomings, and ignorance of A320 avionics and electrical design combined in a manner that overwhelmed the two pilots.
Indonesia’s National Transportation Safety Committee (NTSC) did not assign a probable cause or blame for the accident, but issued 10 recommendations for the airline, the Directorate General of Civil Aviation (DGCA), the FAA, EASA and Airbus. AirAsia in the interim had voluntarily initiated 49 safety actions, including dedicated simulator sessions for Airbus-designed upset and stall recovery training, more hand-flying during departures and approaches, and assigning an aircraft “custodian” to monitor defective equipment.
The first officer, with 2,247 flight hours, mostly in the A320, was the pilot-flying as the aircraft reached its cruising altitude of 32,000 ft. in the midst of cumulonimbus buildups shortly after 6 a.m. on the route from Surabaya to Singapore. The captain monitoring the flight had logged more than 20,000 hr. flight time in military jet fighters and airliners.
AirAsia’s Operation Training Manual, approved by the DGCA, included ground- and simulator-based upset training, but the airline had not implemented the curriculum because it was not mandated by the DGCA nor was it called for by the Airbus-supplied Flight Crew Training Manual, according to the NTSC. “The [manual] stated that the effectiveness of fly-by-wire architecture and the existence of control laws eliminate the need for upset recovery maneuvers to be trained on [envelope-protected Airbus aircraft],” notes the NTSC. Three months after the crash, Airbus published upset training guidelines for airlines, noting that while it is “extremely unlikely” that an upset will occur in the normal envelope-protected control mode, pilots should nonetheless experience pitch-up and roll upset excursions as high as 30 deg. and 67 deg., respectively, in different configurations and potentially in degraded control modes.
Twelve minutes after AirAsia Flight 8501 leveled off that morning, a series of amber advisories flashed on the electronic centralized aircraft-monitoring display in the cockpit, indicating the sequential failure of the two rudder travel limiter units, a safety feature that reduces rudder displacement as speed increases. In the next 11 min., as the crew turned to remain clear of cloud buildups and requested a climb to 38,000 ft., there were three additional failures. In each case, the pilots reset the two flight augmentation computers (FACS) that control the rudder limiters via two reset buttons on the overhead panel.
The captain had experienced this failure three days earlier in the same aircraft during pushback. A company engineer came into the cockpit and pulled circuit breakers for the two flight augmentation computers per the airline’s troubleshooting manual. One of the circuit breakers is in the overhead panel; the other is located on the wall behind and out of reach of the first officer’s seat. The captain had asked the engineer whether the circuit-breaker method could be used whenever the problem reappeared, to which the engineer said it could be done “whenever instructed on the ECAM [Electronic Centralized Aircraft Monitoring],” according to the NTSC. On Dec. 28, the ECAM instructed the pilots to disengage then reengage each flight augmentation computer via the push buttons.
This particular problem had been recurring at an increasing rate, 23 times during the previous year on PK-AXC, the accident aircraft, nine of which occurred in December. The troubleshooting manual advice—either resetting the FACS via the push buttons or pulling the circuit breakers—generally cleared the fault, so the issue was not considered a “repetitive problem” in the documentation, and the pertinent electronic modules were not changed out.
While ICAO standards call for pilots to record “all known defects” after a flight, the requirement was not specified in Indonesian regulations, and pilots often did not file reports regarding the rudder-limiter failure. Following the accident, investigators found evidence of solder cracking caused by temperature cycling in the electronics. Airbus had responded to similar reliability problems with upgraded electronic units in 1993 and 2000, both of which were installed in the accident aircraft, and again in 2015 following the accident. AirAsia in its post-crash safety actions made improvements to its maintenance processes to track repetitive issues, including assigning custodians to each aircraft.
One minute later, when the rudder-limiter-failure caution appeared for the fifth time, investigators surmise the captain resorted to pulling the circuit breakers. The NTSC notes that the limiter or FACS failure itself is not considered dangerous (rudder limits are maintained and the aural and textual alerts can be silenced by selecting the Emergency Cancel button). Although Airbus allows for pulling circuit breakers to reset various computers when on the ground, the airframer says “as a general rule,” resets using circuit breakers in the air must be limited to the air pack regulators and avionics ventilation system. The “general rule,” however, opens a door for other resets, providing both pilots “consider and fully understand the consequences of taking the action,” according to Airbus.
Based on the cockpit voice recorder (CVR), the accident pilots did not appear to discuss any consequences and were likely startled by what happened when the captain presumably pulled the breakers. Along with a series of fault messages on the ECAM, the autopilot and autothrottle disconnected, the control law transitioned to “alternate,” removing most of the fly-by-wire envelope protections, and the rudder deflected approximately 2 deg. to the left, resulting in a roll rate of 6 deg./sec. to the left. The first officer responded 9 sec. later—when the roll angle had reached 57 deg.—with a right control input initially and a nearly fully deflected rearward stick pull, rapidly increasing the pitch angle and causing an 11,000 ft./min. climb.
[url=http://aviationweek.com/site-files/aviationweek.com/files/uploads/2015/11/DF-AIRASIA_map.jpg]
When the initial stall warning occurred, the first officer briefly responded by pushing forward on the stick, as called for in standard procedures, but soon after returned to the full-back stick, where it caused the aircraft to enter a fully developed, deep stall, a state in which it remained for the remainder of the flight. The nose-up input after a stall, which is contrary to recovery techniques issued by the airline and the international community, was a common element in the Air France Flight 447 and Colgan accidents in 2009.
The captain attempted to control the aircraft through his stick, but he did not press the “take over” pushbutton on the stick to transfer control from the first officer, as is allowed for in AirAsia standard procedures during an emergency. With both pilots controlling, the A320 control system averaged the two sidestick inputs—nearly full aft stick from the first officer and slightly nose down by the captain—for a nose-up command. The NTSC recommended that AirAsia “reemphasize” with its pilots the “taking-over-control procedure in various critical situations of flight.”
At approximately 29,000 ft., the pilots were able to level the wings, but the angle of attack remained well beyond the stall, and the descent rate settled at 12,000 ft./min., with the audible stall warning and buffeting of the wings evident on the CVR. The aircraft remained in a relatively flat attitude until striking the water. “The condition of stall at [nearly] zero pitch was not a standard on pilot training as the training for stall is performed at high pitch attitude,” says the NTSC, adding that the pilot might have not recognized that the aircraft was in a deep stall despite the stall warning and the buffet.
The inability of some pilots to recognize and correctly recover from upsets and stalls has been a key safety concern in the industry for more than a decade, but it became a top priority after the 2009 crashes.
ICAO in November 2014 called for member nations to require on-aircraft upset prevention and recovery training for multi-pilot and commercial pilot licenses, and simulator upset training for multi-crew type ratings and airline pilot initial and recurrent training programs. Last January, EASA proposed new rules similar to the ICAO standards, to be implemented in April 2018.
The FAA’s upset training requirements for airline pilots, largely the result of Colgan, go beyond the ICAO and EASA. They mandate full-stall demonstrations in full-motion simulators by March 2019, an addition that will most likely require new expanded aerodynamic models for the devices. The agency plans next to update Part 60 rules detailing how to upgrade and gain approval for the extended simulators, although preliminary guidelines the FAA published in 2014 have already been used by FlightSafety International and Gulfstream to create an extended model for a business jet simulator.
It is doubtful the FAA can accelerate its plan, given the training infrastructure that must be put in place, but some airlines have already taken the initiative of providing third-party upset training to their instructors in order to set up in-house training programs. South African Airways and Delta Air Lines are two of the carriers that have such programs underway.
Somewhat promotional but I just had to include this must read post/comment from apstraining :
Quote:First-hand Experience in Airline Upset Training
As a leading Upset Prevention and Recovery Training (UPRT) provider for pilots from airlines around the world, the reaction of this crew as described in the Indonesian Accident Report is not surprising. Regularly - on a daily basis - we see professional pilots, who have not yet had first-hand modern UPRT experience, having serious difficulty in handling time critical upsets effectively. ‘Modern UPRT’ is in compliance with 2014 ICAO and 2015 IATA UPRT guidance on its effective delivery, together addressing more than 200 training elements to enhance awareness, prevention and recovery of airplane upsets.
An airplane upset is a precursor flight condition to loss of control in-flight (LOC-I) that meets certain attitude and/or speed criteria as defined by industry. Of equal importance to modern UPRT is that the provided UPRT is of sufficient intensity, delivered by expert instructors, conducted in appropriately certified airplanes and simulators, following a comprehensive building-block curriculum.
For example; on page 107 of the report, the FDR recorded the pilot flying's (SIC) first reaction to the over-banked attitude of 57 degrees (with likely the nose dropping since the autopilot was disconnected) was to pull and then apply right aileron … three seconds later the aircraft entered a stall. In our experience, this "rolling pull" technique is very common among pilots who have not been given both academic and practical understanding of the dangers of this often-inappropriate technique in a wide diversity of upset scenarios.
"Remf" mentions that "no amount of acceleration of training/warnings will replace common sense." Based on first-hand experience, we respectfully disagree. This conclusion is not substantiated by what we see when our professional pilot customers return for recurrent upset training anywhere from one to two years after their initial UPRT and consistently prove themselves to be very disciplined and effective in a startling upset scenario. It is certainly understandable how certain "techniques" would be considered “common sense” when they are being discussed in an academic context. However, and again based on years of first hand experience delivering UPRT, when non-UPRT trained pilots are put in time-critical, life-threatening situations, "common sense" is typically replaced by ineffective and unsafe "gut-reactions" on the controls due to knowledge and skill deficiencies further degraded by the pilot/crew’s state of mind due to human factors such as startle, surprise and fear.
As alluded to above; ICAO and IATA - with EASA in the process of implementing UPRT interventions in 2016 - have recognized the benefit of integrated (on-aircraft and simulator) upset training in a pilot's skill sets. They each have proposed significant upset training changes to our current licensing and type rating system (see ICAO Doc 10011, EASA NPA 2015-13, and IATA GMBP UPRT). We certainly agree with the Indonesian Report Conclusions that integrated (on-aircraft and simulator) upset training must be implemented across the globe sooner rather than later. The FAA has yet to make this same official conclusion. However, through Advisory Circular (AC) 120-111, the FAA is requiring upset recovery in simulators for Part 121 air carriers by 2019. Improved stall training across all FAA pilot training is also already underway through AC 120-109 - soon to be superseded by AC 120-109A, which likely will include full aerodynamic stall training.
The future is looking brighter when it comes to the worldwide mitigation of LOC-I.
Meanwhile what do we get.. Beard on...beard off..mi..mi..mi..mi..mi..mi..mi..mi..Beaker-UFB!
I see in the Oz that BB has tapped out an article which highlights that the serious safety issues of auto-dependency are still yet to be satisfactorily risk mitigated...
MTF...P2
Auto-pilots cut pilot experience
12:00amBYRON BAILEY
Computer-reliant planes may be making the airways safer, but emergencies expose pilot weaknesses.
Pilot experience reduced by flight automation
Last month was not a good month for aviation safety statistics.
A Bangladeshi airliner crashed on approach into Kathmandu with 71 fatalities.
A day before, a private Turkish Challenger 604 crashed into the Zagros Mountains 370km south of Tehran, killing all 11 on board.
Conflicting reports put the private jet in cruise at 36,000 feet one hour 21 minutes after leaving Sharjah for destination Istanbul when it suddenly climbed to 37,700 feet before entering a pronounced descent, then crashing. The black boxes — flight data recorder and cockpit voice recorder — have been recovered and should be able to answer the question of why this popular and safe large jet crashed.
I am interested because I fly a private Challenger 604. Its avionics and electrical/hydraulic systems place it in the small airliner class plus, as a wide-body type jet, and it is very comfortable for the rich passengers, giving the cabin a loungeroom feel. The passengers of the crashed jet were Mina Basaran, socialite daughter of a wealthy Turkish businessman, and seven of her female friends who were attending her hens party in Dubai — now playground of the rich and famous (Beirut is passe).
The crew of two pilots and one cabin attendant were all female and the captain was a former military pilot.
There are several possibilities that come to mind.
There were thunderstorms active in this area of Iran so could it have been like the Asian Airbus A320 that crashed several years ago when the pilots lost control entering thunderstorm activity.
Perhaps the captain was trying to climb over a thunderstorm and stalled because the descent was rather sudden, which may indicate loss of control.
Maybe they had picked up some ice on the wings — unlikely because the Challenger has excellent anti-ice systems but they rely on the pilots to turn them on. The B777 anti-ice systems, in contrast, are automatic.
The Challenger, which has a supercritical wing, requires careful removal of even the smallest amount of ice before takeoff in low temperatures. When first introduced into service it suffered several takeoff accidents.
Could it be a bomb on board? The descent was sudden and the crew allegedly reported a technical fault. Sharjah is more like a secondary airport that is popular with eastern European airlines, especially Russian. I cannot comment on its airport security.
Sharjah is a small emirate — one of the seven that make up the United Arab Emirates — and is overshadowed by its close, glamorous neighbour Dubai.
The reason the jet was parked at Sharjah was probably because of lack of room at Dubai International airport.
Maybe Iranian air traffic control played a part. Iran has notoriously suspect control and poor communications. I encountered a Russian IL76 military/commercial freighter reciprocal on the airway over Iran. I was in a B777-300 and, according to the EOWE (east odds/west evens) flight level rule, cruising at cleared level 32,000 feet on the way to Paris.
This bogey popped up at my level at 40 nautical miles on my traffic alert and collision avoidance system at my altitude, the wrong altitude, and Tehran ATC was not answering so I immediately deviated 5nm right to let it pass.
Then, of course, comes the human element. The biggest problem facing airlines and corporate aviation is a lack of manual flying skills because of the dumbing down of pilots. The Challenger 604, same as the Airbus and B777, is highly automated. Immediately after gear retraction on takeoff the autopilot is engaged.
Lateral navigation and speed are all programmed before engine start into the flight management system computers, which then fly the aircraft to the destination.
The approach at destination is normally flown by the autopilot after the pilots enter arrival and runway details into the computer. Late on final approach the pilot flying disconnects the autopilot and lands the aircraft.
What this means is, on a typical — for example, nine-hour — flight, the pilot is hands-on for only several minutes. This is safe as modern aircraft are so reliable that air travel is safer than driving a car. The problem occurs when something unexpectedly goes wrong and puts the pilots out of their comfort zone.
Pilots get to refresh their aircraft systems knowledge and emergency handling skills every six months in simulators. Qantas does this every three months for its pilots.
However, even in the simulator, most training is done with the autopilot engaged as it is more reliable to fly an approach, even with an engine failed, with the autopilot engaged.
What this means is if you put a pilot in a situation they have never encountered the lack of a solid basic flying skill will surface.
Take, for example, the Air France A330 that after pitot tube icing, suffered a pilot-induced stall at high altitude. The panicked pilot froze and without realising it held the aircraft in the stalled condition all the way down until it crashed into the sea.
Corporate aviation, same as airlines, is subject to the same tyranny of cost. Pilot training is expensive and the trend, especially overseas, is for crews is to be less experienced even though on paper they appear to be equally qualified.
As remarked recently by the hero of the Hudson River landing of US Airways flight 1549 in New York in 2009, Captain Chesley “Sully” Sullenberger, “There is no substitute for experience in an unexpected and difficult situation.”
The automation of modern aircraft has resulted in the dumbing down of pilots, with many lacking adequate manual flying skills. But I guess it is something that aviation has to live with.
Byron Bailey, a veteran commercial pilot with more than 45 years’ experience, is a former RAAF fighter pilot and trainer. He was a senior captain with Emirates for 15 years.