Medical perils of extending the range of single-aisle aircrafts

Single Aisle

The past decade has witnessed the introduction of new age technology aircraft engines. These engines are 12-15% fuel efficient and the airframe is lighter.

This has resulted in fuel efficiency and thus increased range of the aircrafts. Some of these aircrafts belong to the single aisle families of Airbus and Boeing.

This will be a shot in the arm for the aircraft manufacturers and the airlines who are already planning to introduce the opening of farther destinations.

However, there is a need to empathise with the plight of the passengers and crew. The physical movement of the crew is restricted in a single-aisle aircraft and with passenger seating over 180 passengers, it will be quite claustrophobic for many.

There are a number of medical conditions associated with long haul travel but most have not been proven with enough data.

World Health Organisation released research on Global Hazards of Travel (WRIGHT), in order to establish whether the risk of venous thromboembolism is increased by air travel, to determine the magnitude of the risk and the effect of other factors on the risk, and to study the effect of preventive measures.

The findings of the epidemiological studies indicate that the risk of venous thromboembolism is increased 2- to 3-fold after long-haul flights (more than 4 h) and also with other forms of travel involving prolonged seated immobility. The risk increases with the duration of travel and with multiple flights within a short period. In absolute terms, an average of 1 passenger in 6000 will suffer from venous thromboembolism after a long-haul flight.

Image result for long haul flying deep vein thrombosis
Medical conditions

Read the full report

Read More

A cognitive view of 100 Tonne takeoff weight error, close shave for AirFrance

How can a B-777 takeoff with an undetected takeoff weight error of a 100T, mindFly human factor analysis?


A number of serious incidents have been attributed to incorrect takeoff performance. A total of 20 occurrences were identified between the period 1 January 1989 and 30 June 2009 where the calculation or entry of erroneous takeoff performance parameters was cited as contributing to commercial jet aircraft accidents 

The Boeing 777-F takes off on 22 May 2015, from Paris Airport at low speed and the tailstrike protection (TSP) of the aircraft is activated. The plane does not take height. The crew then applies the full thrust. The aircraft flies over the opposite threshold at a height of approximately 170 ft and continues to take off. During the climb, the crew questions the causes of the incident and realizes that it has made a mistake of 100 tons in the mass used for the calculation of takeoff performance. The crew continues the flight to destination without further incident.

Flight preparation

The Captain and three Co-pilots prepared a cargo flight from Paris – Charles-de-Gaulle bound for Mexico City. While the two Relief Pilots carried out the exterior walkaround and checked that the load was safely in place, the Captain (PM) and the Co-pilot (PF) carried out the flight preparation in the cockpit.
The Co-pilot added up the various scheduled weights in his head and found a preliminary Take-Off Weight (TOW) of 243 tonnes instead of 343 tonnes. He entered this erroneous value in his Onboard Performance Tool (OPT)(3). The Captain added the supplementary fuel decided on by the crew to the TOW on the Operational Flight
Plan (OFP) and obtained a correct weight of 343 tonnes. The Captain entered the same erroneous TOW (243 tonnes) into his OPT as that calculated by the Co-pilot.
The Captain and the Co-pilot then cross-checked the take-off parameters calculated by their respective OPTs and obtained the same results.
The crew began to enter the OPT results, obtained from an erroneous TOW of 100 tonnes, in the FMS. The Co-pilot (PF) entered, in particular, the balance, an assumed temperature of 37°, a flap configuration of 5°, and the V1 of 143 kt calculated by the OPT(4). The Captain was surprised that the calculated take-off speeds were about 20 kt below the reference speeds calculated by the FMS.
The Captain received the Final Loadsheet and announced the final load figure to the Co-pilot (PF). The latter recalculated on paper, the take-off weight based on the Dry Operating Weight (DOW), the payload and final fuel weight. He made carrying over error and obtained 241.5 tonnes instead of 341.5 tonnes. He compared the newly calculated value (241.5 tonnes) with that previously entered in his OPT (243 tonnes) and called out ‘‘it is consistent’’.


The Captain compared the Take-Off Weight (TOW) of the Final Loadsheet with the gross weight (GR WT)(5) displayed on the FMS and found that they were consistent.
The latter was correct because it was calculated from the Zero Fuel Weight
(ZFW) – which was correctly entered into the FMS by the crew – and the fuel on board automatically calculated by the aircraft.
When the refuelling was completed, both crew members went back to entering the speeds. This time, the reference speeds were no longer displayed and the crew unsuccessfully tried to display them by repeatedly pressing REF SPDS ON/OFF. None of the crew members understood why the reference speeds had disappeared.
The Captain and Co-pilot (PF) re-entered all the data in the FMS starting with the ZFW. The reference speeds calculated by the FMS were still not displayed.

The crew finally entered into the FMS, the take-off speeds calculated by the OPTs (V1=143 kt, VR=152 kt and V2=156 kt) for take-off. The flap configuration was 5°. This configuration surprised one of the Relief Pilots, but he did not express his misgivings. The aircraft lined up for runway 26R from taxiway T12 and took off at 10:25.

Read More

Visual illusion in fog, Spicejet heavy landing saga

Approach in fog and illusion
How can a combination of surprise event, visual illusion and cognitive lockup lead to a heavy landing? Human factor analysis by mindFly


The Spicejet Q400 was approaching to land at Delhi airport on a foggy night of Nov 2018. During approach for landing at around 500 feet AGL, the crew sighted the runway and continued the approach. At around 411 feet AGL, the Captain disengaged the autopilot and simultaneously inadvertently
pressed the go-around (GA) button. As the GA button was pressed, the flight director bars which were synchronised with the instrument landing system,
moved to 10° pitch up on Flight Director for go-around mode. The Captain disregarded the bar on Flight Director and continued approach visually.
As the FD bars were showing GA pitch, the PIC had no reference other than approach lights & PAPI.

During landing, there was a high Rate of Descent and in order to reduce the decent, PIC increased power to maintain glide slope. During approach while over the threshold of runway 27 the aircraft was above the glideslope and in order to correct the same, PIC reduced power. While reducing the power, the Captain lifted the lock of power lever and the power was reduced below flight idle. There was a momentary warning sound in the cockpit for the same. This reduction in power further increased the rate of descent.

Due to low visibility prevailing at that time, the Captain had depth perception and initiated flare very close to the runway by increasing the pitch attitude to 6.3°. This increase in pitch very close to the ground with a high rate of descent resulted in hard landing with a vertical acceleration of 3.77G and subsequent tail strike.

Final investigation DGCA report

Approach in fog
Approach in fog

Visual illusion

Visual illusions take place when conditions modify the pilot’s perception of the environment relative to his / her expectations. They may result in landing short of the runway, hard landing or runway overrun, but may also cause spatial disorientation and loss of control.

30 % of approach-and-landing accidents occur during the conduct of visual approaches or during the visual segment of an instrument approach.
Visual approaches at night present a greater exposure because of reduced visual cues, increased likelihood of visual illusions and risk of spatial disorientation.
Low visibility and/or precipitations are a circumstantial factor in more than 70 % of approach-and-landing accidents, including those involving CFIT.

How do Visual Illusions Affect the Pilot’s Perception?

Illusions result from the absence of or the alteration of visual references that modifies the pilot perception of his / her position relative to the runway threshold. They affect the perception of heights, distances and/or intercept angles.
Visual illusions are most critical when transitioning from IMC and instrument references to VMC and visual references.
Illusions (such as the black-hole effect) affect the flight crew vertical and horizontal situational awareness, particularly during the base leg and when turning final (as applicable) and during the final approach.
Visual illusions usually induce crew inputs (corrections) that cause the aircraft to deviate from the original and intended vertical or lateral flight path.

Illusion in fog

Flying in light rain, fog, haze, mist, smoke, dust, glare or darkness usually
create the illusion of being too high.

Shallow fog (i.e., fog layer not exceeding 300 ft in thickness) results in a low
obscuration but also in low horizontal visibility. When on top of a shallow fog layer, the ground (or airport and runway, if flying overhead) can be seen, but when entering the fog layer the forward and slant visibility usually are lost.
Entering a fog layer also creates the perception of a pitch up, thus inducing a tendency to push over and place the aircraft below the desired glide path
and in a steeper-than-desired attitude.

Damage visuals
Damage visuals

mindFly human factor analysis

The crew were on their last leg of the duty. The approach was stable till the pilot inadvertently pressed the go around switches which on gave the pitch command that would be required for a go around.

From the safety point of view this resulted in tight coupling of events. The visual transition from instruments, surprise event, optical illusion into fog and cognitive lockup.

A go-around could have prevented the incident for sure but the pilot decided to recover the situation and continue visually taking cues from his senses. Had the same event taken place at a 1000ft, the pilot would have in all probability carried out a safe landing. Due to the tight coupling of events, the physical reactions were excessive. This led to abrupt inputs on the thrust lever and the control column leading to an excessive rate of descent and the heavy landing. An event like the inadvertent pressing of the go-around switches can cause a surprise event. This can lead to distraction and /or disorientation. Cognitive lockup prevents a task switch over from approach to go-around since the pilots objective is for task completion and over 90% task is complete. Therefore there is a psychological lockup which insists that the pilot continues and land the aircraft.

Training is the only preventive strategy. Read my paper on Cognitive lockup to better understand the concept. The role of the pilot monitoring has been undermined in the prevailing training setup in India. The BEA study on the role of PM globally has highlighted the fact that in most of the events the PM does not know where to look!

Cognitive lockup
Prevention/Recovery from disorientation
Blog Stats
  • 27,760 hits
My article featured in the ‘Mentor’ magazine of the National Association of Flight Instructors, USA Moscow airport Istanbul NEO Against all odds, were the crew in a situation to abandon the approach? Https://
Top Posts & Pages
Yours truly, Amit Singh
Follow mindFly on
%d bloggers like this: