Decide model aviation: you’ll want to avoid these mistakes

Decide model aviation – wondering what the key decision-making processes and methods are? This post has everything you need to know.

Decision making during my pilot training was probably one of the last items I bothered figuring out. It definitely helps improve the quality of the outcome by having a good framework to use, particularly in stressful situations.

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Why do we need decision making models in aviation?

Flying is a very safe business.  Things seldom go wrong, and when they do, the problems are rarely so serious as to present a threat to the aircraft, the passengers, and the flight crew.  Whatever the emergency or incident, the flight crew will need to make decisions and take appropriate action. 

Poor decisions, or possibly no decisions at all, can have serious consequences.  Even a relatively minor issue, such as a faulty instrument, can result in a catastrophe if not handled properly, or if the flight crew allow themselves to be sufficiently distracted by a minor issue as to let a second, greater threat to the aircraft develop unnoticed.  

What happens when the decision making process is weak?

This happened in December 1978 when United Airlines Flight 173, a DC-8 operating a scheduled service between John F Kennedy International Airport and Portland International Airport, managed to run out of fuel whilst in a holding pattern and, as a result, crashed some seven miles short of the runway.  

The crew had allowed themselves to become distracted by a landing gear problem and forgot the golden rule, which is, whatever happens, to remember to fly the aircraft.  A possible landing with a retracted nose gear, which is eminently survivable, had become a dead stick landing in a built-up area resulting in the deaths of ten passengers.

The poor performance of the captain and the failure of the crew to influence the decision-making process in the cockpit was cited as a major contributing factor in this accident.

Assessing the time available

Pilots are trained to make appropriate decisions, but whatever decisions the flight crew makes will be based on a number of factors.  The most critical issue is of course time.  The more time you have, the easier it is to evaluate a situation and come up with a solution.

The ultimate example of this is probably when one of the oxygen tanks on the service module exploded during the flight of Apollo 13 in April 1970, forcing the crew to abandon the Command Module and to power up and occupy the Lunar Module.  

Once the initial emergency had been contained mission control in Houston had four days during which they could look at all the options available to them in order to bring the crew safely back to earth.  

Time available decision making vs non time available decision making

Non time available emergency

At the other extreme, with an engine failure on take-off, there is very little time to make a decision, and in any case, in this scenario, a flight crew’s options will be very limited.  They will either be committed to the take-off, or they won’t be.  

Time-critical decision making tends to be very procedural where a certain set of actions are performed after a given trigger e.g. engine fire bell during the take-off roll. You do not want to be having a discussion about whether or not to reject the take-off at close to decision speed (V1).

Time available decision making

However, if the situation presents itself when the aircraft is at cruising altitude there should be plenty of time for the flight crew to assess the situation and the threat to the aircraft and to consider the various options available to them before making a decision.  

However, even when at cruising altitude a relatively benign situation can turn to disaster if inappropriate actions are taken, which may be down to inexperience, a lack of situational awareness (particularly in an emergency that occurs at night with little or no horizon surface definition) poor Crew Resource Management (CRM), serious mishandling of the flight controls or a combination of all of these.  

Air France flight 447

A good example of this would be the loss of Air France flight 447 in 2009 when the aircraft, an A330 outbound from Rio de Janeiro to Paris stalled at altitude and crashed into the South Atlantic killing all the passengers and crew. 

 It was astonishing that such an experienced flight crew were unable to recognize the signs of an aerodynamic stall and to take the appropriate recovery actions.  As I alluded to earlier the crew on the flight deck clearly lost situational awareness.  

The crew were also misled by counter-indications they were receiving from the aircraft’s stall warning system and may have had an exaggerated sense of confidence in the aircraft’s stall protection system.  However, poor CRM allowed the situation to quickly deteriorate and become critical.

Once the captain had returned to the flight deck from the crew rest bunk where he had been when the emergency developed, at no time did he take command of the situation and make a decision.  In fact, it is fair to say that no one was in command in that cockpit when it smashed into the ocean at 02:14 UTC, just four minutes after the autopilot disconnected.  

This was an appalling accident involving a state-of-the-art aircraft, that shocked and stunned the aviation world.

Diagnosing the problem

In order to correctly diagnose a problem, the flight crew will need as much information as possible about what happened in the lead up to the problem, partly to avoid jumping to wrong conclusions or making false assumptions. 

This information may come from the aircraft instruments, or other visual clues, passengers, or Air Traffic Control. Modern aircraft are equipped with all sorts of audible and visual alarm cues to help a flight crew diagnose the problem, but even these may not be enough to give the crew he full picture.  

Insufficient information to diagnose the problem

British Airway volcanic ash incident

In 1982 a British Airways Boeing 747-200 took off from Kuala Lumpar, Malaysia bound for Perth, Australia.  When the aircraft was at cruising altitude above the Indian Ocean, south of Java, the flight crew were presented with some unusual visual phenomena.  

There was St Elmo’s fire dancing around the windshield, even though the weather indicated clear skies, there were lighting effects akin to tracer bullets being fired at the aircraft, along with a sulphurous smell pervading the aircraft.  

Passengers reported that the fan blades of the engines appeared to be glowing, seemingly lit from within, and their HF (High Frequency) radio communications were severely disrupted by static,  Captain Eric Moody, First Officer Roger Greaves and Senior Engineer Officer Barry Townley-Freeman had absolutely no idea when was going on.  

In fact, it is fair to say that they had no idea what was going on during the entire time of the emergency.  Within minutes of the appearance of these various phenomena the number four engine surged and failed, followed quickly by engines one, two and three, until the 747-200 was reduced to giant glider.  What subsequently happened is the stuff of aviation legend.  

Captain Moody and his flight crew repeatedly went through the engine re-light drills whilst preparing for an ocean ditching.  As Eric Moody recalled, here was little else they could do, other than experiment with various airspeeds during the relight procedures (which resulted in some unusual sensations for the passengers).  Their perseverance paid off. Fourteen minutes after the start of the emergency, at an altitude of 13,500 feet engine number three restarted, followed by numbers one, two and three.  

Thanks to some outstanding airmanship and CRM on the part of the crew, the aircraft was successfully landed at Jakarta airport.  It was only on landing that it became apparent to the crew what had happened.  They had unknowingly flown into a cloud of volcanic ash from the erupting Mount Galunggung which had effectively choked the engines.  

As the aircraft descended the molten ash froze and solidified and enough of it broke off to enable the engines to be re-started.  This is a fairly extreme example of the flight crew not being in possession of the full facts to help them to make a decision.  

Had they known what was happening, or had they been informed of their predicament by ATC they may have had time to perform a 180 degree turn and fly out of the ash cloud before the engines failed.  As it was, they flew deeper and deeper into the ash cloud, worsening their predicament.

Once the flight crew has assessed the time available to them and have diagnosed the problem, they can look at the options available to them.  

Americal Airline Flight 191 decision making

On 25 May 1979, the flight crew of American Airlines flight 191 were not in full possession of the facts regarding the state of their aircraft, a DC-10, when the number one engine and its pylon detached from the aircraft as it rotated at Chicago’s O’Hare Airport.  

As far as the crew were concerned, they were dealing with an engine failure only and flew the standard engine out departure as laid down by American Airlines operating procedure.  What they didn’t know was that as the pylon and engine detached the hydraulic lines that kept the leading-edge slats locked in the extended position had severed.  

A three-foot section of leading edge was also damaged.  Without the necessary hydraulic power aerodynamic forces pushed the leading-edge slats back in, increasing the stalling speed of the left wing by six knots.  This was unknown to the flight crew.  As it was, the left wing stalled and dropped, resulting in an increasing bank angle to the left to the point where the aircraft was unrecoverable.

Had the First Officer carried out the simple expedient of lowering the nose from its 14 degree nose up attitude and increased speed to 159 knots instead of flying at the prescribed 153 knots it is likely that the aircraft would have recovered and flown safely away on its remaining two engines.  Sadly, time was not on their side for them to make a detailed assessment of the situation.  

Only 50 seconds elapsed from the time the number one engine and pylon separated from wing to the aircraft to the aircraft slamming into a field some 1400m from the end of the runway. 

Factors typically considered in the decision making process in an aircraft emergency

In the case of an emergency descent and landing being necessary, the options available will be dictated to the crew by such things as:

• State of the aircraft
• Airports within range
• Weather at the divert airport
• Minimum runway length required
• Landing aids and fire and rescue equipment  such as ILS or Precision Approach Radar (PAR) at the airport
• Maximum landing weight (fuel may have to be dumped),
• The need to get down to a safe cabin altitude,
• and whether there are other factors dictating the need to get the aircraft down on the deck as quickly as possible, such as a passenger medical emergency or a fire.  

Ultimately the captain will make the final decision, but he or she will always explain why that decision is the most appropriate course of action given the information available to the flight crew and the extent of the emergency.

Selecting the best option

Once the flight crew has assessed the time available to them and have diagnosed the problem, they can look at the options available to them.  

United Airlines Flight 232

The options available to the flight crew of United Airlines flight 232 on 19 July 1989 were very limited given the state of the aircraft.  After the uncontained fan failure of number two engine all the hydraulic fluid had bled away out of the DC-10 into the airflow, leaving the flight crew with very little way of controlling the aircraft other than using asymmetric engine thrust on numbers one and three engines.  

However, Captain Al Haynes knew that he could give his passengers their best chances of survival if he could put down at an airport where there were emergency services, so putting the aircraft down in one of the cornfields that stretched from horizon to horizon in Iowa was definitely not one of his options, even though this might have been easier than bringing the stricken aircraft in to make an attempted landing at Sioux City Municipal airport.  

They also had to decide whether to put the gear down or to leave it up and belly land the aircraft.  The captain decided to put the gear down as this would absorb some of the shock of the impact, as there would be a far higher rate of descent than normal. Ultimately, what saved 184 of the 296 souls on board was a thoroughly professional performance from Captain Haynes and his crew in desperate circumstances.  

They were lucky in that Captain Denny Fitch, a United Airlines training captain, happened to be sitting in the first-class accommodation on a positional flight and could offer his services to Captain Haynes.  This was CRM at its finest, all four highly experienced crew working together to bring about as successful an outcome as they could have hoped for given the circumstances.

Assigning responsibilities

Once a decision has been made the captain will need to assign responsibilities.  These days this will normally involve only two flight crew, but the cabin crew will need to be kept in the loop.  The cabin may have to be prepared for an emergency landing, as opposed to a straightforward divert.  

The landing may possibly not be on the runway (as occurred at London Heathrow in January 2008 when a 777 on final approach suffered a double engine failure due to ice blocking fuel lines and landed short of the runway), or on water.  

The airport will need to be kept informed so that the emergency services can be deployed.  The airport approach plates will need to be consulted so that the flight crew can set up for the approach and landing, and the captain will assign flying duties.

Reviewing Actions Taken

During the entire course of the emergency the flight crew should be constantly evaluating what they have just done.  They will effectively be asking themselves the question “have we done the right thing?”.  

A classic example of this would be immediately following an engine failure or fire in flight.  Having performed the post engine failure shut down checklist the crew would be reviewing whether they really did have to shut down the engine, and if they did indeed have to perform a full shut down, whether they shut down the correct engine.  

The crew would be carrying out such reviews until the last minute, such as whether or not the decision to close, or indeed open a particular fuel cross feed in the event of fuel starvation to an engine was in fact the right thing to do. 

What are the different decision making models?

Various acronyms are used to help guide pilots through the decision-making process.

TDODAR Model

One of these is TDODAR.  We’ve already covered most of this but here it is spelt out:

T is for Time

D is for Diagnose the problem

O is for Options

D is for Decide on the best option

A is for Assign responsibilities 

R is for Review what you have done

PIOSEE Model

A variation of this acronym is PIOSEE, this is basically the same model using some slightly different wording. Here it is spelt out:

P is for what is Problem

I is for what Information do we have

O is for what are our Options

S is for Select the best option

E is for Execute the best option

E is for Evaluate what you have done

What is the Decide model in aviation?

Another acronym that is used frequently by pilots is DECIDE. Here it is spelt out:

D is for Detect the problem

E is for Estimate the need to counter or react to a situation.

C is for Choose a desirable outcome.

I is to Identify the actions which could successfully control the change.

D is for Do the necessary action.

E is for Evaluate what you have done.

Excellent decision making

To finish let’s look at a couple of accidents in which the decision-making process ended up in a successful outcome in one case and a disaster in the other.

Everyone will remember the accident on 15th January 2009 on the Hudson River in New York in which the actions of Captain Sullenberger and his First Officer Jeffrey Stiles saved the lives of all 155 passengers and crew aboard US Airways Flight 1549.

The facts are well documented but the decision-making process was executed under extraordinary circumstances involving a double engine failure at an altitude of only 2818ft. Captain Sullenberger had seconds to decide whether he could make it back to La Guardia airport or the alternate airport at Teterboro in New Jersey.

He also made crucial decisions that affected the outcome such as starting up the APU to maintain power in the cockpit. The decision to land on the Hudson River was entirely vindicated in the subsequent accident investigation conducted by the NTSB once they had factored in the crucial 30 seconds ‘thinking’ time immediately following the double engine failure. 

Example of where better decision making may have led to a better outcome

In contrast, let’s look at what happened to British Midland Flight 92, a Boeing 737-400, which crashed onto the motorway embankment near the town of Kegworth in Leicestershire in England on 8^th January 1989.

The aircraft suffered an engine failure in the left-hand engine whilst climbing through 28000ft. The decision the flight crew had to make was to ascertain which engine had failed, whether it could be restarted and whether or not a divert was necessary.

Unfortunately, despite counter-indications, the flight crew took the decision to shut down the number 2 engine which was the good engine. The flight crew also made some assumptions given the location of the smoke as being in the passenger cabin, but these assumptions were based on the previous model 737 which they were used to.

The flight crew did start to review what they had done but unfortunately during the review process they were interrupted by a call from ATC and never completed the review of their post incident actions. Also, they did not have information from the passenger cabin which would have been a crucial part of their decision-making process.

As we know, when the flight crew tried to throttle up the failed engine it totally disintegrated and only then did, they realise the appalling predicament in which they now found themselves, at which point they had insufficient time to start up the shutdown engine. Sadly 47 out of the 126 souls on board died when the aircraft struck the motorway embankment some 630 metres short of the runway threshold.

It is true that there were several mitigating circumstances, which help us understand why they made the decision they did, but the fact remains that the accident occurred because of an incorrect decision that was taken on the flight deck following the inflight emergency.

Any thoughts on decision-making models in aviation? Please leave a comment in the section below, we would love to hear from you!