UNRELIBLE AIRSPEED INFORMATION AND UPSET TRAINING

A subject rarely covered in recurrent simulator training, often due to time constraints but one which has proved to be more dangerous than any engine failure scenarios, is one where the crew of a jet aircraft is faced with either a total or partial loss of Air Data Computer information.

The aircraft itself is to be found perfectly capable of flight, however, often fatal crashes result due to the crew receiving incorrect airspeed and altitude information and then acting inappropriately.

When I was undergoing my basic training, I commenced a ‘solo’ take-off in a little two seat Piper Tomahawk from Oxford airport. As I accelerated down the runway I noticed that my IAS was not increasing, now I’d never rejected a take-off, so continued down the runway, until the little aircraft became airborne of its own accord. I was climbing away at an above normal pitch attitude and with full power and 0kts IAS. Now I knew I must be faster than 0kts as I was neither a helicopter nor dead! I reverted to P.A.T….Power…Attitude and Trim, I flew an untidy circuit at what must have been a higher than normal approach speed as the houses below seemed to be getting bigger much quicker than normal! I touched down, bounced and then stabilised and taxied to the ramp to meet my equally bemused and relieved instructor. Investigation by the engineers found that the hose behind the pitot tube had become detached. I learnt a very valuable lesson, very, very early in my career.

It is time for all of us to review and learn from the mistakes of others and use current technical information and training guidelines to assist us should we ever be faced with both a widely confusing and terrifying situation, especially at night and/or in IMC. I was lucky it was a beautiful clear summer’s day.

These days’ modern glass cockpit jet aircraft have numerous backup systems alongside an independent standby system to relay correct airspeed and altitude information to the pilots. However, with the addition to numerous warning systems such as Stall Warning, Overspeed and Airspeed Low; the combination of this information can conflict in our perceptions of our situation. This confusion degrades the crew’s management and performance, again often with fatal consequences.

With the recent very public accident involving Air France 447, the aircraft involved, an Airbus 330 crashed as a result of some of the previous mentioned reasons. It now seems that finally the aviation industry is waking up to the realisation that something needs to be done. Americans call this a Monday morning quarterback response, in the UK we say ‘closing the stable door after the horse has bolted’. The result is the same; this wake-up call has come too late for countless hundreds of passengers and crew. Correct training should assist in our own behaviour and responses when faced with a similar situation, eliminating as much as possible the chances of reading accident reports similar to those described further on.

The findings of the Air France flight 447 crash report stated, amongst others, the following:

1.       There was no explicit task-sharing between the two co-pilots. (CRM FAILURE)

2.       There was an inconsistency between the measured speeds, likely as a result of the obstruction of the Pitot probes in an ice crystal environment. (INSTRUMENT FAILURE)

3.       Even though they identified and announced the loss of the speed indications, neither of the two co-pilots called the procedure "Unreliable IAS". (S.O.P. FAILURE)

4.       The co-pilots had received no high altitude training for the "Unreliable IAS" procedure and manual aircraft handling. (TRAINING FAILURE)

5.       No standard callouts regarding the differences in pitch attitude and vertical speed were made. (S.O.P. FAILURE)

6.       Neither of the pilots made any reference to the stall warning and neither of the pilots formally identified the stall situation. (EXPERIENCE/TRAINING FAILURE)

 

As we all know, during CRM training we discuss the ‘Swiss cheese model’ where it is generally not one action which causes an accident, but multiple actions which when added together, lead to disaster. The above six points relating to Air France show five different ‘actions/failures’ which led to the deaths of 228 passengers and crew, on an aircraft which was perfectly capable of flight.

Again and I cannot reiterate this enough. We all need to learn from these mistakes, through refresher training and ensure that through knowledge and practice; can respond correctly and safely should we ever be unfortunate enough to encounter a similar situation.

 

BOEING AND AIRBUS CHANGES IN ATTITUDE.

Finally both Boeing and Airbus have recognised the need for further training in recognising and recovering from the situation where the pilots have to, sorry, need to ‘return back to basics’; so being able to produce a safe and successful outcome when faced with problems affecting pitot and static failures.

For example, with respect to the soon to be introduced Airbus A350, Airbus Company’s training department has decreed the following at a recent conference.

“Airbus is going to train pilots for its A350XWB differently.

The first three days in the A350 simulator will be about letting the pilots find out that it is "just another aeroplane". Without using any of the sophisticated flight guidance systems they will be able to find out how it flies and what that feels like. These pilots may not have done that for years on the aircraft they fly now, so they might find out a few things about themselves as well as the A350.

Airbus' flying training manager David Owens stated at the Royal Aeronautical Society's annual Flight Crew Training Conference in London that pilots will not be allowed to switch on the automatic systems until they have learned how to fly the aeroplane.”

Although Airbus’s Owens didn't spell it out, it seems the industry is beginning to learn that never letting the pilots treat the aeroplane like a flying machine means they never find out what it can do. And more importantly, what it can't; so again requiring us to go back to basics.

Boeing has been working with the FAA and the aviation industry to develop training aids that improve a pilot's ability to respond to challenging situations. Boeing has provided an updated training aid as part of their continuing effort to reduce loss-of-control airplane accidents. The upset recovery training aid focuses on helping flight crews recover from unusual flight attitudes that can result from unusual weather or other "upset" conditions as a result of loss of reliable cockpit information. This enhanced training also increases the pilot's ability to recognize and avoid situations that can lead to airplane upsets, and potentially fatal consequences.

 

CAUSES AND CONSEQUENCES-CASE STUDY REVIEWS

 

Going ‘back to basics’ starts with understanding how the pitot static system, when functioning incorrectly can affect our displayed information.

 

FIRSTLY THE STATIC SYSTEM.

 

 

For example when the static ports are blocked, disaster can and has occurred. Partial recognition of this can be explained as follows.

Should the static ports be blocked or covered, then during the take-off roll, both the altimeter and the airspeed indicator operate correctly. After lift-off, assuming the trapped static pressure is that of the field elevation, the altimeter indication remains at the field elevation. With respect to airspeed, the sensed dynamic pressure fails to increase as rapidly as it should during climb because of the trapped static pressure. Therefore, if the airplane actually climbs at a constant speed, the airspeed indication decays, reaching the lower end indication. If the captain relies on the airspeed indicator for proper information, the typical response will be to reduce the pitch attitude to maintain the erroneous airspeed, possibly causing the airplane to exceed its airspeed limitations. Complicating this situation is the fact that the overspeed warning does not operate if connected to the same erroneous airspeed source. 

The above scenario led to the following accident. On October 2nd 1996 shortly after takeoff just past midnight, the Boeing 757 airliner crew discovered that their basic flight instruments were behaving erratically and reported receiving contradictory serial emergency messages from the onboard computer, such as rudder ratio, mach speed trim, overspeed, underspeed and flying too low. The crew declared an emergency and requested an immediate return to the airport.

 

 

Later investigation into the accident revealed that duct tape was accidentally left over some or all of the static ports (on the underside of the fuselage) after the aircraft was cleaned, eventually leading to the crash. One of the company’s employees had left the tape on by mistake.

As a result of the blocked static ports, the basic flight instruments relayed false airspeed, altitude and vertical speed data. Because the failure was not in any of the instruments but rather in a common supporting system, thereby defeating redundancy, the altimeter also relayed the false altitude information to the Air Traffic Controller, who was attempting to provide the pilots with basic flight data. This led to extreme confusion in the cockpit as the pilots were provided with some data (altitude) which seemed to correlate correctly with instrument data (altimeter) while the other data provided by ATC (approximate airspeed) did not agree.

Although the pilots were quite cognizant of the possibility that all of the flight instruments were providing inaccurate data, the correlation between the altitude data given by ATC and that on the altimeter likely further compounded the confusion. Also contributing to their difficulty were the numerous cockpit alarms that the computer system generated, which conflicted both with each other and with the instruments. This lack of situational awareness can be seen in the CVR transcript. The fact that the flight took place at night and over water, thus not giving the pilots any visual references, was also a major factor. All onboard died in the ensuing crash. 

SECONDLY THE PITOT SYSTEM.

Blocked or malfunctioning pitot tubes cause their own system malfunctions and subsequent erroneous information indications. If the pitot probe is plugged, its sense line likely contains air trapped at a pressure equal to that of the field elevation static pressure. During the take-off roll, therefore, the sensed dynamic pressure remains zero and the airspeed instrument remains pegged at its lower stop. If the flight crew does not reject the take-off, the pitot pressure remains plugged at field-elevation pressure as the airplane climbs, but the static pressure begins to drop. The altimeter operates almost correctly during the climb. However, the resulting sensed dynamic pressure causes the airspeed indicator to come alive seconds after lift-off. Regardless of the actual climb speed of the airplane, the faulty airspeed indication continues to increase as altitude increases, until the airspeed catches up to the correct value. The indicated airspeed continues to increase through the correct value as the airplane climbs. The VMO speed can appear to be exceeded. Additionally, an overspeed warning can be triggered. If the pilot flying trusts the faulty airspeed indicator because of the temptation early in the climb to believe that some movement means the indicator has begun to operate normally, the pilot flying is in grave danger of increasing pitch, reducing thrust, or both to reduce the erroneous indicated airspeed. This could cause the airplane to exceed its stall angle of attack, though the stall warning system, which is driven by angle of attack, should continue to function normally.

The above can explain partially what happened to Birgenair flight 301 which was a Turkish registered Boeing 757. During takeoff roll at 11:42 p.m. the captain, one of Birgenairs' most senior pilots, found that his air speed indicator (ASI) was not working properly, but chose not to abort takeoff. The co-pilot's ASI was functional.

While the plane was climbing through 4,700 feet (1,400 m), the captain's airspeed indicator read 350 knots. The autopilot, which was taking its air speed information from the same equipment that was providing faulty readings to the captain's ASI, increased the pitch-up attitude and reduced power to lower the plane's airspeed. Co-pilot’s ASI read 200 knots, and decreasing, yet the airplane started to give multiple contradictory warnings that it was flying too fast, including rudder ratio mach airspeed and overspeed lights and sounds.

 

The autopilot reached the limits of its programming and disengaged. After checking their circuit breakers for the source of the warnings, the crew then reduced thrust to lower the speed. This immediately triggered the 757's stick-shaker stall alert, warning the confused pilots that the aircraft was flying dangerously slow, seconds after it was warning them that the speed was too high. The co-pilot and relief pilot both seemed to recognize the approaching stall and tried to tell the captain, but did not intervene directly, possibly out of deference to the captain's age and experience. The captain then tried to recover from the stall by increasing the plane's thrust to full, but the plane was still in a nose up attitude, preventing the engines from receiving adequate airflow to match the increase in thrust. The left engine stalled and flamed out, which caused the right engine, still at full power, to throw the airplane into a spin. Moments later, the plane inverted. At 11:47 p.m., the Ground Proximity Warning System sounded an audio warning, and eight seconds later the plane crashed into the Atlantic Ocean. All 13 crew members and 176 passengers were killed.
 

CRM AND QRH CHECKLIST USE.

So three crashes have been highlighted, to three aircraft all of which could fly with a little sitting on your hands analyzing the situation and reverting to basics, Pitch and Power. Have some basic numbers ingrained in your brain with which you can ensure that the aircraft will remain in a stable flight condition and also within the aircraft flight envelope; these figures can be refined once the aircraft is confirmed as being under control.

These scenarios requires good Crew Resource Management skills, use your colleagues on the flight deck to assist in identifying what ‘might’ or has failed, then together come up with the correct checklist. Remember aviate first. The QRH states that when you are faced with ‘flight with unreliable airspeed’, then both altitude and vertical speed indications could be incorrect to.

Which leads us to the QRH checklist:

IAS DISAGREE

or

Airspeed Unreliable

IAS DISAGREE or Airspeed Unreliable

Condition: One or more of these occur:

 

•The captain's and first officer's airspeed indications disagree by 5 knots or more.

•The airspeed or Mach indications are suspected to be unreliable (Items which may indicate Airspeed or Mach Unreliable are listed in the Additional Information section).

 

Objective: To maintain control using manual pitch and thrust.

 

1. Check pitch attitude and thrust.

2. If pitch attitude or thrust are not normal for the phase of flight:

 

Autopilot disengage switch . . . . . . . . . . .Push

Autothrottle disconnect switch . . . . . . . . .Push

F/D switches (both) . . . . . . . . . . . . . . . . OFF

 

Establish normal pitch attitude and thrust setting for the phase of flight.

 

Note: Normal pitch attitude and thrust setting are available in the Flight With Unreliable Airspeed table in the Performance Inflight chapter.

 

3. Altitude, vertical speed, and reference EPR indicator may be unreliable.

4. Crosscheck PFD airspeed displays and standby airspeed indicator. A PFD airspeed that is more than 10 knots different than the standby airspeed should be considered unreliable. 

 

Then the Boeing QRH checklist directs you to trouble shooting. But the aircraft is now being controlled. 

The easiest way to maintain control would be if at or above your minimum safe altitude, Level Off. The aircraft is obviously easier to stabilise when flying straight and level.

Disengage the Autopilot Flight Director System and Autothrottle.

 

RULES OF THUMB…..

 

AT FL100…….MAXIMUM LANDING WEIGHT………TO FLY AT 290kts-------3’ PITCH AND 70%N1

 

AT FL100…….MAXIMUM TAKE-OFF WEIGHT……..TO FLY AT 290kts-------4’ PITCH AND 75%N1

 

(INCREASE THE ABOVE N1 FIGURES BY 10% FOR EACH ADDITIONAL 10,000ft.)

 

BELOW 10,000ft REMEMBER THE B747-400 IS NOT A DEVIL TO FLY!!!! SO 6’ PITCH AND 66%N1 (ALL THE SIXES!!!)

 

So, know your aircraft systems, know your checklist Recall items, know basic aircraft performance numbers know how to practice good CRM……all of which will lead you to ‘knowing’ how to protect your aircraft and stay safe. Even when in the dead of the night when your body is feeling naturally tired, after a moment of reflection, you KNOW what to do.

 

 

 

 

 

 

 

 

 

A PERFECT WORLD……………..MAYBE ONE DAY.

“I ADD THE FOLLOWING CAVEAT……ALL BELOW IS MY 'SOUL' OPINION.”

Currently there are approximately, oh I don’t know, but it is in the hundreds of thousands, airline pilots globally, however, in ten years’ time this number will have both reduced and increased. Okay I know that does not make sense, neither mathematically nor linguistically.

I am implying that the number of commercial, in other words primarily airline pilots, will have numerically increased, but their collective experience will have decreased as the ‘veterans’ of the industry retire. This will leave a very worrying gap.

Now I am not a ‘dinosaur’, one who harps on as to how it used to be, and how it should still be done. Yes, admittedly I have been flying the ‘Airlines’ for almost 30 years, in-fact since I was 19 years of age and have over 18,000 hours of flying experience in my log books. I have also been fortunate to fly for airlines from more than ten different countries, embracing many different cultures; I have seen the good and the bad, promoted the good and walked away from the bad.

 

 

                                          (Author is wearing the 'picasso' themed sweater!)

I do understand the need for progress and industry advancements. But and it’s a big ‘but,’ I have my concerns that sophisticated automation is taking over. HAL (One less than IBM, for those who remember the Stanley Cubrick movie 2001) is becoming more and more of a worrying reality on the modern airliner flight deck.

I am also finding that reliance and reliability are frequently taking over from awareness and understanding. In my role as a training captain I have seen supposedly experienced pilots literally stabbing at buttons and flicking switches hoping that these actions will rectify a particular situation, showing minimal understanding of the systems involved. Somewhere, something at a basic level has broken down. Would you want your family flying as passengers in the back of this crew’s aircraft; neither would I.

 

              (The muscle is the Auto-flight system, the brains the Flight Management Computer, the         operator and over-seer.....the pilots.)

In the last couple of years we have seen how situational awareness, when absent, can and will cause a perfectly serviceable aircraft to fly into the ground. How a lack of understanding basic aerodynamics will place a reasonably serviceable aircraft at the bottom of the ocean; or how personality disorders, often through local cultures, will reduce almost four hundred tonnes of Boeing’s finest aircraft into scrap metal.

 

(Korean Airlines Boeing 747-200 C.F.I.T in Guam)

These all could have and should have never occurred; their victims should still be alive. An aircraft commander guilty of these crimes  is only spared being described as a ‘serial killer’ due to simple definition and timescale, but they are just as complicit as any Fred West or Ted Bundy.

Teaching and training, discussions and consultations, sharing of experiences but above all learning and understanding; should mitigate the number of these incidents and accidents.

 

(Air France Airbus 330 loss of control and crash into the Atlantic Ocean.)

I find that the attitudes of members of all nations can be included in my statements. The western world is not exempt, poor attitudes prevail here too…..one Far Eastern airline I flew for, the ex-pats had an unofficial ‘shoes on – shoes off’ policy for take-off. If it was an ex-pat as the aircraft commander then they felt that they could relax and make themselves comfortable. However, if it was a ‘local’ Captain, then shoes would remain on until gear up in case of a runway ‘excursion’ or rejected take-off. I now realise in equal measures the arrogance and ignorance of this mentality.

(TACA Airbus 320 runway 'excursion in Honduras.)

There are many excellent pilots in Africa and Asia, just as there are many in the western world, yet disturbingly there are similarly many that shouldn’t be entrusted with anything more complex than a light switch, let alone a hundred million dollar plus aircraft.

There is arrogance, ignorance, mistrust, unprofessionalism and a general lack of ability globally, throughout all cultures. We have regulatory bodies such as the FAA, JAA and EASA amongst others, though they try hard and their motives are well founded but  I find that often they are realistically impotent. Yes their members and regulators can push out rules, requirements and guidelines. Yes these same bodies can carry out company department audits and random spot checks on airport ramps. I have been ‘ramp-checked’ and been asked the most ridiculous questions by various people, on one occasion it caused me to suspend belief in both their qualifications and sanity.

 

Have an experienced Airbus training captain delve into an airline’s Airbus flight operations department, the same goes for Boeing, Embraer et al. Do not allow a Human Resources ‘expert’ or an engineer investigate this flight operations department, in simple terms, ‘like for like’.

However, more often than not these are no more than carefully orchestrated charades. Whether it is slipping members of an African ‘authority’ several thousand dollars to go shopping instead of digging any deeper into a company’s infrastructure, or trying to pull the wool over the eyes of European regulators in a way that would have the directors of the iconic movie ‘The Sting’ blushing in disbelief.

Hundreds of innocent people, men, women and children die needlessly each year because of mistakes which should have been avoided. Whether the root causes are due to improperly policed national authorities allowing pilots with falsified documents to be in command of multi-million dollar aircraft, or western pilots who ‘slip’ through the ‘training’ net due to company politics, amongst other ‘crimes’. I have personally witnessed many of these, not in deepest darkest Africa or a once colonial outpost in the Far East, but in Europe.

 

 

(A pilot with fake documents and a barely trained co-pilot got into a Yak-42 private jet to fly three-time Russian league champion team Lokomotiv from Yaroslavl to Minsk.

44 died after a failed take-off.....)

These ‘so called’ pilots are no better than east European pick pocket gangs which can be found roaming on any given afternoon any busy London street, as they too think that they can and will get away with their crimes and deceptions. I say they shouldn’t, they should be made accountable and to a lesser extent, ‘exposed’.

The sixty thousand dollar question is….what is the answer? Well I can only see one option; a totally independent non-affiliated team of ‘over-seers’.  A team which has the political and regulatory backing of aviation authorities globally; a team which has the powers to descend on an airline and request immediately training documents and operational line documents. A team whom are able to attend flight simulator training details or ‘fly the line’, as observers with crews which have not been cherry picked; this team would have the recognition of the member states and able to make their findings heard, respected and ultimately acted upon.

I know we already have teams of auditors belonging to various authorities and organisations; however, there are also consultants that are brought in by the soon to be audited companies to show how to pull the wool over their eyes. Everyone wins except for those innocent people who die as a result of these charades.

How do we go about making this fabulously rewarding profession all we hope and desire it to be? Petitions, lobbying….strongly worded letters? I am told that we have systems involving checks and balances in place and in a moral unbiased world they would work. It’s obvious that they don’t as yet another aircraft over-runs a runway breaking up and killing yet more innocent people. As well as a disregard for SOPs and ATC procedures where but for the grace of your God, nobody was killed.

This is where I need your advice and assistance. Or sadly, am I just wasting my time…………

 

Watch this...so true.