Human Factors and CRM.

Human factors are “issues affecting how people do their jobs” (Australian Civil Aviation Safety Authority (CASA), 2020). Those issues are social and personal skills. The skills are required to maintain the operations running safely and efficiently (CASA, 2020). Therefore, those skills are essential in aviation. However, we need to understand that not just pilots need to have those skills, but everyone around the operations such as “air traffic controllers, management, maintenance, regulatory bodies and policymakers” (Stanton N. A., Li W. and Harris D, 2019).

For pilots, Crew Resource Management (CRM) is the correct use of resources available for the crew. The purpose of CRM is to increase operational efficiency by reducing stress and error. Further, social and personal skills or human factors, as well as other skills, are essential for functional CRM. Also, it is necessary to understand that accidents are a chain of mistakes, and as mention early, CRM lowers the risks for errors.

In a multi-crew environment, CRM is essential to prevent accidents. The reason is that communication between the two pilots, aeronautical decision making (ADM), and situational awareness help to avoid mistakes. For instance, both pilots should divide the workload, decide who is flying, and who is complying with the proper in-flight emergency (communication). Then, to deal with less stress, the pilot flying should engage the autopilot, so he/she doesn’t need to stress about maintaining altitude or a heading (ADM). Next, both pilots need to know the condition of the airplane like fuel remaining and flight path, as well as suitable runways nearby, terrain, and weather around the aircraft (situational awareness).

A good example of a lack of CRM is United Airlines Flight 173. In this accident, the crew failed to monitor fuel quantity after having an issue with the landing gear. Clearly, the pilots and the flight engineer were distracted, dealing with the unusual situation while neglecting the remaining task. However, it is important to understand that before this accident, CRM did not exist. More information about the accident in the following video:

References:

AOPA. (2019). Crm. Retrieved from https://www.aopa.org/-/media/Images/AOPA-Main/News-and-Media/Publications/Flight-Training-Magazine/1907f/1907f_ap_crm/1907f_ap_crm_16x9.jpg?h=675&w=1200&la=en&hash=4EDF84E3D13EE1C96F185FD0CE7A16EB

Neville A. Stanton, Wen-Chin Li & Don Harris (2019) Editorial: Ergonomics and Human Factors in Aviation, Ergonomics, 62:2, 131-137, DOI: 10.1080/00140139.2019.1564589

Safety Management Systems. (2016, February 16). Human factors. Retrieved from https://www.casa.gov.au/safety-management/human-factors

TACG. (n.d.). Flight Deck. Retrieved from https://www.tacgworldwide.com/portals/23/Images/pilot-sighting.jpg?ver=2016-10-12-130534-967

Improvised Explosive Devices (IED)

According to the Transport Security Administration (TSA), “Terrorist become increasingly interested in circumventing airport security screening by concealing improvised explosive devices inside commercial electronics, physical areas of the body, cargo, shoes/clothing, and cosmetics/liquids” (2015). Terrorists and suicide bombers use these improvised explosive devices (IED) to target the general public, airport facilities, and aircraft. The reason these individuals try to use this type of explosive is that since it is homemade, it can come in many forms, and it is harder to detect by airport security. Additionally, terrorists use IEDs because they can cause several adverse health effects, loss of life, as well as massive damage to structures and infrastructure.

IED attached to a cellphone. 

As previously mentioned, IEDs come in different forms, such as pipe bombs or sophisticated devices. However, the components of this type of explosive are the same. The United States Department of Homeland Security (DHS) says the “ingredients” include, “an initiator, switch, main charge, power source, and a container.” and “additional materials or ‘enhancements’ such as nails, glass, or metal fragments designed to increase the amount of shrapnel propelled by the explosion. (2003). For instance, the power source could be hydrogen peroxide, fertilizers, and gunpowder.

Metal detectors.

Fortunately, airport security has implemented many screening layers to prevent terrorists bring IEDs inside security areas in the airport terminal as well as onboard the aircraft. As mention before, terrorists carry these explosives in checked bags, clothing, shoes, commercial electronics, and liquids. For that reason, TSA screens each passenger and checked bags. 

Checked bag screening.

Passengers have to go through a magnetometer, which will detect metals in cloth and adjacent to the body. If the magnetometer detects metals, security personnel will pat-down the passenger as far as the carry-on and personal items that are scanned on an x-ray machine. 

For the checked bags, those go through another x-ray machine, and sometimes random checks are performed. Another layer that security uses is the canine unit. Depending on the airport, this unit can be before the screening area or moving around the terminal or a combination of both.

Canine unit.

All the layers of security previously mention made airport security better than in the last century. Further, in the US, it has been more than ten years since the previous incident relating to IEDs. Although the system is not perfect, it is clear it has been effective. Currently, most online stores do not products that can be a source of power for IEDs, but third-party stores do. Products used for a power source can be more controlled by the federal or local government.

References:

Bloomberg. (2013, July). A Transportation Security Administration employee moves a checked piece of passenger luggage toward a scanning machine at a security check point at O'Hare International Airport in Chicago, Illinois. Retrieved from https://api.time.com/wp-content/uploads/2015/06/gettyimages-137370194.jpg?w=800&quality=85

Juste. C. (2018, November 21). Miami International Airport started using bomb-sniffing dogs to screen passengers at terminals with heavy traffic. Using the canines enables the Transportation Security Administration to move passengers up to 30 percent faster than normal. Retrieved from https://www.miamiherald.com/news/business/tourism-cruises/article222021750.html

MEDIAPRODUCTION. (n.d.). Metal Detector. 
Retrieved from https://www.rd.com/wp-content/uploads/2020/02/GettyImages-182440070-e1582922201512.jpg

National Academies of Sciences, Engineering, and Medicine, Division on Earth and Life Studies, Committee on Reducing the Threat of Improvised Explosive Device Attacks by Restricting Access to Chemical Explosive Precursors, & Board on Chemical Sciences and Technology. (2018). Reducing the threat of improvised explosive device attacks by restricting access to explosive precursor chemicals National Academies Press. doi:10.17226/24862

U.S. Department of Homeland Security. (n.d.). DHS Science and Technology Directorate Checked Baggage Program [Fact sheet]. 
Retrieved from https://www.dhs.gov/sites/default/files/publications/Checked%20Baggage%20Fact%20Sheet%2014OCT16.pdf

U.S. Department of Homeland Security. (n.d.). DHS Science and Technology Directorate Pat-Down Accuracy Training Tool (PATT) [Fact sheet].
Retrieved from https://www.dhs.gov/sites/default/files/publications/OPSR_PATT-170208-508.pdf

U.S. Department of Homeland Security. (n.d.). Explosives Detection Canines – Protecting the Homeland [Factsheet]. 
Retrieved from https://www.dhs.gov/sites/default/files/publications/19_0807_st_updated-pbied-factsheet_508.pdf

U.S. Department of Homeland Security. (n.d.). IED Attack Improvised Explosive Devices [Factsheet]. 
Retrieved from https://www.dhs.gov/xlibrary/assets/prep_ied_fact_sheet.pdf

Landing Gear System

The Landing Gear System

The landing gear system supports the aircraft's weight on the surface. Also, it is responsible for resisting high loads on landings without damage while providing comfort to everyone on board. (Makhlouf & Aliofkhazraei, 2015 ). This system usually consists of wheels; however, skies or floats are an alternative, depending on the type of aircraft (FAA, 2016). Additionally, other components, such as the brakes assembly and hydraulic lines, are part of the system.

The Main Gear of a B737NG

Like any other system, the landing gear is subject to malfunction, even on aircraft with rigorous maintenance. Also, a failure on this system can endanger people on board, the airplane itself, and other people or airport facility near the aircraft. For this reason, pilots have to inspect the system before each flight thoroughly.   

Many things could go wrong with the landing gear system. Nevertheless, pilots are familiar with the troubleshooting procedures, and they have handbooks on the flight deck and electronic flight bags that describes the procedures to follow after a failure. Typically, the malfunction of this system represents a time threat, which means pilots will have time to deal with the problem and does not constitute an immediate danger to the aircraft.

One of the least issues this system could have is a flat tire. Similar to a car, this could happen for many reasons; the most common is due to a tire worn out. If this happens, the aircraft should stop immediately. Otherwise, the friction could damage the wheel disk. However, in extreme cases, a flat tire could lead to a fatal accident such as on the Air France Flight 4590.

G450 abnormal gear position

For instance, if the gear is stuck down, the airplane won't be able to accelerate due to the amount of drag generated by the structure. Therefore, the engines would have to produce more thrust to climb at an average climb speed and to maintain a normal cruise airspeed. Consequently, more fuel is needed, a fuel that was not planned, and most likely, a return to the field would be required.

E190's nose gear did not deploy.

Conversely, one of the gears might not come to the down and locked position. This problem usually happens in the approach phase; at this time, pilots should discontinue the approach and deal with the issue. The gear is kept in the up position by hydraulic pressure; therefore, pilots must remove that pressure following the appropriate procedure. However, if pilots are unable to bring the gear down, gear up landing must be planned.

A320 nose gear failure.

The worst issue the landing gear system could experience is a structural failure. Many factors could lead to this problem, from the environment to overloading the landing gear. If the structure is damaged, the gear could collapse. This failure could happen without any noticeable indication, and that is why this is the worst. Often maintenance technicians can recognize this issue on aircraft inspections.

References:

• 737NG nose landing gear. (n.d.). Retrieved from http://www.b737.org.uk/landinggear.htm#General

• Landing Gear 101. (n.d.). G450 Abnormal Gear Condition. Retrieved from http://code7700.com/g450_landing_gear_abnormals.htm

• Pilot’s handbook of aeronautical knowledge : 2016 (First Skyhorse Publishing edition.). (2016). New York, NY: Skyhorse Publishing. 

• Makhlouf, A. S. H., & Aliofkhazraei, M. (2015). Handbook of materials failure analysis with case studies from the aerospace and automotive industries: With case studies from the aerospace, chemical, and oil and gas industries. Burlington: Elsevier Science. 

• The Associated Press. (2019). Rescue team gather near a plane of Myanmar National Airline (Mna) after an accident at Mandalay International airport Sunday, May 12, 2019, in Mandalay, Myanmar. All passengers and crew are reported safe and uninjured after a Myanmar National Airlines plane made a scheduled but emergency landing at Mandalay International Airport on only its rear landing wheels after the front landing gear failed to deploy. (Aung Thura via Ap). Retrieved from https://abcnews.go.com/International/wireStory/myanmar-passenger-jet-lands-safely-landing-gear-fails-62986476

• The rear-most tire is dragging and about to catch fire. (2005). Retrieved from http://www.airlinesafety.com/editorials/JetBlueLAX.htm

Atmospheric Pressure and Aircraft Performance

Atmospheric Pressure

The atmospheric pressure is a variable factor that pilots must know very well since it is not only used in the essential instruments of the flight deck but is one factor that affects aircraft performance. Also, aircraft engineers need to understand all elements in the environment that affects performance, including pressure.

Sadraey defines pressure (2017) “as a normal force exerted by a fluid (gas or liquid) per unit area on which the force acts.” (p. 12). Considering pressure changes with altitude, temperature, and location, the International Civil Aviation Organization (ICAO) established a worldwide standard referred to as the International Standard Atmosphere (ISA). At sea level, the surface pressure is 29.92 inches of mercury or 1013.2 millibars. (FAA, 2016).

Standard sea level pressure.

Moreover, atmospheric pressure decreases as altitude increases. To illustrate, we must understand that air is compressible. Near the surface, the air is compressed by the air above it, but at higher altitudes, the air becomes less dense and pressure becomes less. Consequently, the rate at which pressure decreases with altitude is not linear (Sadraey, 2017). However, for simplicity, under the ISA, the rate at which pressure decreases with altitude is 1 “Hg per 1,000 feet of altitude gain to 10,000 feet.

The rate at which pressure decreases. 

Properties of a standard atmosphere.

As noted above, atmospheric pressure is one factor that affects performance, with it and the standard pressure we calculate pressure altitude. On the performance charts, we use pressure altitude to calculate different numbers, such as takeoff roll and landing roll. However, the performance calculated is valid only in standard atmospheric conditions, which is very unlikely to exist. For that reason, density altitude is calculated. 

References:

Pilot’s handbook of aeronautical knowledge : 2016  (First Skyhorse Publishing edition.). (2016). New York, NY: Skyhorse Publishing.

Sadraey, M. H. (2017). Aircraft performance: An engineering approach. Boca Raton, FL: CRC Press, Taylor & Francis Group. doi:10.1201/9781315366913