Subscribe by Email

Monday, January 26, 2015


Is it important for pilots to know why they do what they do?  I thinks so, but some might disagree.  I think we should talk about it.

I have stated before that my desire for this blog is to facilitate a dialog among aviation professionals.  I hope this post will initiate such a discussion. 

Standard Operating Policy (SOP) is the hallmark of private and commercial aviation.  It describes in detail the steps that are to be taken to accomplish a specific action or task. Is it relevant or required to know what the SOP is supposed to accomplish or why it is important?  Must SOP compliance accomplish a specific objective or may compliance be its own objective with no other purpose?

I would like for readers to “weigh in” on this subject based on a specific example.  Therefore, I pose these questions….

As a single pilot or a pilot in command of a multi crew aircraft, what is my responsibility in the following scenario?   I am landing on a runway that I have landed on many times before.  The aircraft is at a normal landing weight and I have landed at this weight many times before. There are no weather considerations and the wind is less than 10mph.  The runway is clear and dry.

Must I compute landing distance for this landing?  If the answer is no, why is it not required?  If the answer is yes, why is it mandatory?  If the only reason to obtain landing data is because it is included in SOP is that a valid reason? Is computing distance the same as evaluating landing performance?

Finally, should a single SOP be written for all conditions or should SOP be based on the relevant conditions?

Sunday, July 13, 2014

Asiana 214 and NTSB Credibility

The National Transportation and Safety Board of the United States, NTSB, recently released it’s findings on the crash of AsianasFlight 214, which crashed on July 6, 2013 at San Francisco International Airport (SFO).  All professional aviators and their instructors as well as air traffic control specialists should read and study the report.  The information in it describes the enormous potential for and realization of unimagined failures that always exist in the complex relationship between humans and the machines they control. 

There is no question that the crew of Asiana 214 (humans) failed to effectively manage their Boeing 777 in the final moments of the flight.  The NTSB detailed the operational errors of the crew, the design flaws of the flight guidance system and some relevant issues related to their training.  The report also highlights numerous other contributory factors, but uncharacteristically for the NTSB, missed a very obvious one, air traffic control.  The NTSB has been the worlds “gold standard” in aviation accident investigation for decades.  Unfortunately, it seems the gold might have lost some of its glitter.

The probable cause of Asiana 214 focused on human failures, primarily by the crew and secondarily by designers and trainers, which were thoroughly examined in the investigation.  However, there are other human components of this story that should also be examined for their role in this fatal accident.   Specifically overlooked was the environment in which the flight operated.  The machine was a Boeing 777. The environment was the airspace near SFO. The humans are the engineers, instructors, air traffic controllers and pilots who design, train and operate them. The NTSB report on Asiana 214 surprisingly describes the contributory role of the aircraft and each of these other elements except air traffic control.  How can this report have such an obvious omission?  This is very perplexing.  Was it just a huge oversight or an intentional exclusion?   In light of the fact that there was speculation by the Board on other contributing factors, this oversight is even more astonishing. 

Currently, at large metropolitan airports where the air traffic volume is heavy, a flight crewsrole has evolved into that of a facilitator between air traffic control instructions and the airliners flight guidance system rather than that of aviator.  Like all pilots flying modern airplanes into highly controlled airports, including SFO, the crew of Asiana 214 was tasked with converting the commands (not suggestions) of ATC into a desired flight path and energy state by programming the aircrafts flight guidance system.  The Boeing 777 is both designed and its pilots trained to operate it with reference to the flight guidance system.  Desired parameters are entered and the computed information is shown to the pilots by reference to the flight directors on the primary flight display (PFD) or heads up display (HUD).  The pilots follow the flight director commands manually or by engaging the autopilot.  The flight directors are turned off in flight on only very rare occasions.

Because the Asiana crew was ineffective applying their approach clearance to the flight guidance system, their workload increased dramatically.  ATC’s instruction to maintain a high speed longer than normal increased task saturation as well.  A late landing clearance by SFO tower provided an additional distraction diverting the crew’s attention away from subtle flight guidance information in the final seconds before the crash.   

Although there are many aspects to the air traffic control handling of Asiana 214, I will limit the discussion of ATCs contributory role to the time period after the crew received their approach clearance.

From the NTSB history of the flight (italics): 

"According to recorded information, NORCAL stated “Asiana 214 heavy, San Francisco airport 9 to 10 oclock, one seven miles, do you have it in sight?” The flight responded they had the field in sight and NORCAL cleared them to fly a visual approach to runway 28L on an assigned heading of 310° to intercept final approach. At a point approximately 14 NM5 from the airport NORCAL instructed the flight to maintain 180 kts until 5 NM from the airport."

This command by ATC, as well as the inoperative electronic glide slope, set up a series of events that facilitated the crash.  It is not certain, but clearly reasonable to infer that if the crew had been allowed to slow the aircraft at their discretion, or if there had been an operable electronic glide slope, the unintended consequences of autothrottle “HOLD” would have occurred at a higher altitude or not at all.  How can the NTSB omit these relevant facts?

The NTSB found that the flight could have been completed successfully without the electronic glide slope.  That statement is not particularly probative since it is made without context. As the Asiana pilots pointed out in their submission, a Flight Safety Foundation (FSF) report on approach and landing accidents (ALA) stated that 75% of flights did not use or have a precision approach aid available.   The FSF further states that the accident risk is 5 times greater for commercial aircraft flying non-precision approaches.

In the hearings the NTSB conducted on the human factors of this accident, Dr.s Sarter and Abbott and Captain McKenney all testified to the interrelationships between parts of a safety system. As the “swiss cheese metaphor” for safety systems shows, the slices are only effective when used in combination.  Removal of one slice may or may not be significant depending on the make up of the other slices.  Why does one plane crash in the same conditions that allow many others to be successful?  That is why the role of ATC in this accident cannot just be brushed as inconsequential.   These are exactly the issues the NTSB is tasked with considering.

“The trainee captain stated that after arming and intercepting the localizer he set the DUYET intersection crossing altitude of 1,800 ft. MSL in the mode control panel (MCP) altitude window and began using the AFDS vertical speed (VS) mode to descend at 1000 feet per minute (FPM). The IP stated the arc on the navigation display (ND) showed they would be high at DUYET. The observer stated he thought they were a little higher than the normal profile when they were cleared for the approach, and they extended the landing gear earlier than normal because they needed to get down. The trainee captain set the command airspeed bug to 172 kts, and acknowledged when the observer commented this was below the assigned 180 kts.”

This emphasizes the fact that the 180 knot restriction was increasing the crew's task saturation by complicating energy management solutions. 

At the prompting of the IP, the trainee captain increased the command vertical speed to 1,500 FPM. The trainee captain commanded the flaps be set to 20° and requested the IP to reset the command altitude from 1,800 ft. to 3,000 ft., the missed approach altitude, as the flight approached 2,000 ft. MSL.

According to recorded data, at 1,600 ft. MSL the AFDS pitch mode changed to FLCH SPD, the throttles began to increase power, and the airplane pitch attitude began to increase; this was followed by autopilot disconnect and shortly thereafter a reduction in the thrust levers to the idle position, followed by a change of the autothrottle mode from THRUST to HOLD. The trainee captain stated he considered pressing the FLCH pushbutton to obtain a higher descent rate but he could not recall what he did for sure. He disconnected the autopilot and called out “manual flight.” None of the three pilots could recall the autothrottle status displayed on the flight mode annunciator (FMA). The IP stated he set the command airspeed to the approach speed of 137 kts. and turned both flight director (FD) switches off and then turned the right FD switch back on. Recorded data showed the left FD switch was turned off but the right FD switch remained on.

Pre selecting the missed approach altitude is common practice by B777 crews.  However, setting an altitude above the aircraft without the flight guidance capturing and maintaining either an altitude or glide slope caused the autopilot to initiate a climb. The pilot naturally and appropriately disconnected the autopilot and manually flew the aircraft. Unfortunately, that unusual set of circumstances caused the auto throttle mode to remain in "HOLD" and not respond to the commanded speed as the crew expected. 

“The trainee captain called for the flaps to be set to 30°, and after a delay due to the airspeed being in excess of the flap limit speed of 170 kts. the IP placed the flaps to 30°.”

Because ATC instructed Asiana 214 to maintain 180 knots until 5 miles, they would be 10 knots above the limit speed for flaps 30° and 43 knots above their target approach airspeed at approximately 1500AGL (3 degree glide path).  Without an electronic glideslope or a VNAV PATH, this complicated programming of the flight guidance system.  At 1000’ AGL, their mindset would likely have been slowing the airplane down quickly as they descended and closed on the runway.  The power needed to be reduced to idle to get below the limit speed for flaps 30 (170 knots) as well as slowing to the target approach speed of 137 knots.  This maneuver, set up by ATC requirements was clearly contributory to the accident.

Flight 214 was handed off to, but not acknowledged by, San Francisco Tower.  In combination with the ATC imposed energy management complication, lack of electronic glide slope and flight guidance mode confusion, this was another significant distraction. 

“The instructor pilot stated he saw 2 red and 2 white precision approach path indicator (PAPI) lights at 1,000 ft. MSL and speed was a little high. The observer saw the descent rate on the vertical speed indicator was in excess of 1,000 FPM as the flight descended through 1,000 ft. MSL, and he called out “sink rate” several times. The IP stated he heard this callout but they were still high and the descent rate was only 1,000 to 1,100 FPM.”

Slightly above the glide path and slowing, the trainee captain manually flew the aircraft toward what he thought would be a stable approach at 500’.   Unaware of the significance of the autothrottle “HOLD” mode, the aircraft slowed toward target speed.  Still not cleared to land and below 1000the crew once again queried San Francisco Tower and received landing clearance 9 seconds later.  The late prompted landing clearance was an ATC distraction that diverted the crews attention at a very critical time.    

The aircraft was on glide path with the idle power as it descended toward 500’.  At about 500the aircraft began to drift below the PAPI (glidepath).   As the pilot began to adjust the descent with pitch, the aircraft quickly slowed well below target speed.  By the time the crew was alerted, noticed the low speed and initiated a go around it was too late.

In any accident, there are many factors that intersect to create the causal conditions.  Failure to consider all of them results in an incomplete and ineffective investigation. The relevance air traffic control resources, procedures and practices might have had on this accident is not the depth of analysis we have come to expect from the NTSB.

It would be extremely naive to believe ineffective or improper use of the flight guidance system to comply with air traffic control instructions only affects a few crews.  Recognition by the NTSB that air traffic control practices have a profound impact on how crews operate the flight guidance systems of modern airliners would be more consistent with their role in aviation safety. 

Since the report on Asiana 214 was prepared under his leadership, I would hope that Acting NTSB Chairman Hart would be given the opportunity to give his perspective on this controversy during his confirmation process.

Sunday, April 6, 2014

Austrailians And The Search For Malaysian Flight 370

On reports that possible “pings” from flight data recorders, Retired Air Chief Marshal Angus Houston, head of the Australian agency coordinating the search operation, briefed the press.  "We are treating each of them seriously. We need to ensure before we leave any of those areas that this does not have any connection with MH370,"

It is very encouraging that there is some hard data to report in the search for Malaysian Flight 370.  It’s only fitting that the Australians are assuming a leadership role in the hunt for the missing Boeing 777.  It’s not just because of the proximity to the search location nor the vital role of the Australian vessel Ocean Shield or Air Chief Marshal Houston.  It is because an Australian, Dr. David Warren, invented the flight data and cockpit voice recorders that have become the “holy grail” of this investigation. 

Dr. David Warren was born in 1925 in the remote Northern Territories of Australia.  To receive a better education he attended 12 years of boarding school in Sydney.  His father’s last gift to him before an untimely death in a plane crash in 1934 was a crystal radio set.  David hoped to pursue radio telephony and electronics, however, the war efforts were inconsistent with “radio hams” and he turned to his other hobby chemistry.  Chemistry took his career path into the fuels industry, but he became famous for his contributions in electronics.

David was involved in the accident investigations related to the mysterious crash of the world’s first jet-powered aircraft, the Comet, in 1953.  He theorized that the cause of the accident would be obtained much easier if they knew what statements, if any, about the aircraft’s malfunctions the crew might have made in their last moments. He proposed a device to record cockpit conversations.  Aviation had little interest for such a device at that time.  However, Warren built a prototype based on a miniature wire recorder he had purchased.  Voice and sound could be recorded on this pocket-sized device.  He built two prototypes, one for voice and one for recording aircraft parameters such as speed, altitude, heading, etc.

There was little acceptance of the devices in Australia, however, a British company bought the manufacturing rights and began to produce cockpit voice and flight data recorders. Dr. Warren liked to share how his devices, which in fact are bright orange for better visibility, became known as the "Black Boxes".  Warren says, “It was called a black box because in the records of my meeting in London when it was first demonstrated and they were so keen, one of the people in the discussion afterwards said, ‘This is a wonderful black box.’   And a black box back then was a gadget box.  You didn't have to understand it but it did wonderful things.”

Coincidentally, the first government to make the flight and voice recorders mandatory was Australia.  The step was taken after the investigation of a Fokker F27 crash in Queensland did not have enough information to reach a definite conclusion in the probable cause of the accident.

Dr. Warren’s “Black Boxes” and the information they've provided have contributed more to aviation safety than any other single device.  They are the only way we will ever know the fate of Malaysian Flight 370.

Friday, March 28, 2014

What Could Possibly Go Wrong?


The FAA is soon to implement “Climb Via” procedures and phraseology into SID (Standard Instrument Departures) clearances.  On the surface it doesn’t seem like a big deal.  “Descend Via” clearances have been around for some time.  What has been learned, mostly through the non-punitive data collection efforts of the FAA, pilot unions, operators and LOSA (Line Operational Safety Audits) is that tactical reprogramming of the FMS (Flight Management System), particularly with respect to the vertical path, creates many threats.  When real time adjustments are made to the FMS with LNAV (lateral navigation) and or VNAV (vertical navigation) engaged, the associated threats are increased many fold and their consequences are much greater.  The vast majority of these threats involve communication.  The remaining threats involve the pilot’s ability to effectively monitor the aircraft.  There is a very critical communication process, especially in FMS equipped aircraft that must be precisely followed in order for an ATC clearance to be effectively consummated. 

First and most important, the clearance must be clearly communicated.  It must be understood and correctly read back by the pilots.  The pilots must make the necessary inputs to the aircraft’s flight controls, either manually or through the auto flight systems.  Those inputs must be crosschecked to ensure their compliance and accuracy.  Finally, the crew must identify any inconsistencies between the acknowledged clearance and the aircraft’s current and anticipated speed, course and vertical path must monitor the aircraft.  This communication process between ATC, pilots and aircraft is simple, but at the same time very complex.  This is especially true of FMS equipped aircraft that, once programmed, have the “capability” to completely control speed, course and vertical path with no pilot input or supervision. 

The final and most pernicious component of this communication process is time.  During periods of time compression, i.e. when either the controller or pilots are rushed, are the most fertile territory for error.  Generally this time compression is initiated by the controller’s need to make a tactical change to the SID or STAR (Standard Terminal Arrival Route).  The dynamic environment air traffic controller must deal with drives the time critical changes.  These tactical changes are usually communicated to the crew with minimal notice.  Hence, the introduction of time compression into the communication paradigm between pilot crew, air traffic control and the aircraft.  When this tactical change is received the crew is asked to rapidly understand it and transmit the changes to the aircraft.  Most often this is done through the FMS and auto flight systems.  This reprogramming of the FMS as well as time compression introduces many threats, i.e. potential for error.  Time compression often causes the crew to abbreviate verification protocols.  Just when extra scrutiny is needed most, crews short cut valuable error mitigation steps to try to expeditiously comply with the clearance. 

When short cuts result in an error, a deviation from the clearance, it is often labeled as intentional non-compliance by the crew.  That is a gross over simplification.  More often than not the error comes from the crews attempt to respond the actual or perceived time compression introduced by ATC.  Sometimes it feels like we’re at a “ho down” and the faster ATC fiddles the faster we need to dance.  I have seen this time compression many times, often at Denver International Airport (KDEN).  When a “Descend Via” clearance is modified the reprogramming of the flight guidance systems ranges from simply adjusting the altitude selector to reprogramming the entire arrival.  This happens every day at KDEN when the crew is given a completely new arrival at, just prior to or even after the aircraft has begun its descent.  This can be extremely challenging to do correctly and in a timely manner.

A solution to these threats includes a better understanding by air traffic control of the complexities of managing the sophisticated flight management systems on today’s modern aircraft.  In September 2001 the predominant aircraft types were MD-80s, B-727s, DC-10s and older models of the B-737. There was also a number of FMS equipped aircraft, but not the large number of RNAV arrivals in use today.   In over 12 years since 9/11 I have only had one air traffic controller ride in the flight deck.  I know why, but that doesn’t eliminate the fact.  My guess is that very few air traffic controllers working today that have ridden on the flight deck on modern airliners and observed crews manipulate the flight management systems in “real world” operations. 

Another solution would be for ATC to use less off course vectoring for spacing arrivals. This would reduce the need to amend and reissue “Descend Via” clearances.   RNAV arrivals are designed to minimize the amount of off course vectoring.  London’s Heathrow airport (EGLL), one of the busiest in the world and equipped with only two runways, has a very efficient arrival without all the complexities of the typical RNAV arrival in the United States.  The EGLL arrivals have only a couple of step down fixes and one speed limit point and ends at a holding fix adjacent to the airport.  When the arrival rate exceeds capacity, the holding pattern acts as a buffer and eliminates the need for vectoring.  Planes always leave the holding fix on a downwind heading.  Speeds have been 220 knots on downwind, 180 knots on base and 160 knots on final since the days of the B-707.  It’s very predictable and ATC issues very few amendments.

Another solution to communication problems between ATC and pilots would be for everyone to talk more slowly and clearly.  The objective should not be the number of words spoken in the shortest amount of time, rather the amount of information effectively communicated.  Pilots could do their part by using proper radio phraseology.  Controllers need to speak clearly and deliberately.  Talking fast and using jargon may sound cool, but is not the most effective way for controllers and pilots to communicate.

I do not expect any of these solutions to be adopted anytime soon.  However, more “Descend Via” and now “Climb Via” clearances are coming next week.  Be careful.  Every crew should recognize these clearances are loaded with threats from communication as well as execution.  Make sure you understand the clearance and ask for clarification if necessary.  Make sure you fly the airplane first and reprogram the FMS when you can.  Don’t be in a hurry!  Just because the controller is talking fast doesn’t mean you have to react faster than you’re comfortable.  Accurate compliance with a clearance is the goal not rapid sloppy non-compliance.  Get verification from the other pilot(s) even if it takes a little longer.  Make sure the airplane is doing what you want after it is reprogrammed.  Ron Popeil’s “Set it and forget it!” doesn’t work here.  Watch what the airplane is doing and make sure it is what you want it to do.  When the airplane is climbing or descending in LNAV and VNAV it actually takes more focus, not less.  It’s like telling someone else how to do something and then watching them do it.  You have to stay engaged because you don’t know when they might make a mistake. Either because you told them wrong or because they made a mistake, you have to be ready to intervene.  Finally, if you don’t have the time, distance or understanding to effectively comply with a clearance you simply need to use the word “unable”.  The controller’s expertise is facilitating air traffic, not flying airplanes.  Because a controller issues a clearance doesn’t always mean it is appropriate for the environment.  The Captain’s first responsibility is the safety of the airplane and always has the authority to meet that responsibility.