Uçakların yaklaşma ve iniş safhalarındaki stabilizasyonkriterlerinin incelenmesi
Analysis of stablization criterias during approach andlanding phases of flight
Yazar: BAHTİYAR FİKRET AYDIN
Danışman: DOÇ. DR. AYTAÇ ARIKOĞLU
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Uçak ve Uzay Mühendisliği Ana Bilim Dalı / Uçak ve Uzay Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2019
Konu: Havacılık Mühendisliği = Aeronautical Engineering ; Uçak Mühendisliği = Aircraft Engineering

Özet:
Bir gün içerisinde dünya üzerinde yaklaşık 100.000'den fazla iniş gerçekleşmektedir. Havacılık sektörü oldukça hızlı gelişmekdir ve havacılık otoriterleri tarafından emniyet anlamında sürekli kurallar yayımlanmakta ve revizeler yapılarak uçuş emniyeti en üst düzeyde tutulmaya çalışılmaktadır.  Buna rağmen uçuş emniyetinde ne kadar gelişmeler kaydedilse de kaza riski her zaman vardır ve olamaya devam edecektir. Uçuş emniyeti bu riskleri sürekli azaltıcı yönde çalışmalar yapmakla ve bu risklerin yönetilmesini sağlamakla görevlidir. Bu nedenle uçuş emniyeti kavramı havacılık sektöründeki en önemli kavramlardan biridir. 
Havacılık kazalarının büyük bir çoğunluğu uçakların yaklaşma ve iniş safhalarında gerçekleşir. Bir yıl içerisinde gerçekleşen tüm kazaların %65'i yaklaşma ve iniş safhalarında gerçekleşmektedir. "Flight Safety Foundation" kurumunun yapmış olduğu 16 yıllık bir araştırmanın sonucuna göre yaklaşma ve iniş safhasında gerçekleşen bu kazaların %83'ü doğru bir pas geçme manevrası uygulanarak önlenebilirdi. Değerlerin bize göstermiş olduğu gibi, havacılık dünyasında gerçekleşen tüm kazaların da yaklaşık %54'ü doğru pas geçme manevrası ile önlenebilir durumdadır. 
Stabilizasyon kriterleri uçakların yaklaşma ve iniş safhalarında doğru bir gerekçe ile pas geçme manevrası uygulamaları için kılavuz gibidir. Stabilizasyon kriterleri bu tür kritik kazaların önlenmesine yardımcı olmak için tasarlanmıştır. Bu kriterlerin herhangi birinden yoksun bir yaklaşmaya stabil olmayan veya kararsız yaklaşma denilebilir ve iniş esnasında gerçekleşen uçak kazalarının ana nedenini oluşturur. 
Kararsız yaklaşmalar tüm yaklaşmaların yaklaşık %3.5 ila %4'ünde gerçekleşir. Kararsız yaklaşmarın ise sadece yaklaşık %3'ü doğru bir pas geçme manevrası ile sonuçlanmaktadır. Geri kalan %97'sinde inişe devam edilmektedir. Havacılık şirketlerinin yayımlamış olduğu standart prosedürlere uygun hareket etme çağrılarının yanı sıra pas geçme manevrası prosedürlerinin kendisi de hiç kuşkusuz en sık rastlanan kaza türlerinin sayısını azaltmak için en önemli enstrümanlardır.
Bu tez kapsamında öncelikle kararsız bir yaklaşma sonucu gerçekleşen uçak kazalarına genel bir bakış yapılmış ve oluşum nedenleri incelenmiştir. Dünyadaki diğer araştırmalardan istatistiki veriler paylaşılarak konunun önemine vurgu yapılmıştır.
Bu tez, yukarıdaki gerçeklere dayanarak uçuş ekiplerinin neden bu kritik stabilizasyon kriterlerini ihlal etmelerine rağmen pas geçme marevrasını uygulamadıkları ile ilişkilidir. Belirlenen bu kriterlerin sektörel beklentileri karşılamasının yanı sıra pilotlar için her türlü koşul altında uygulanabilirliğinin önemi vurgulanmıştır. Kararsız bir yaklaşmanın oluşumuna pilotların durum farkındalıklarının eksikliğinin de neden olabileceği belirlenerek akademik olarak bu alanda ne gibi çalışmaların yapıldığı anlatılmıştır. 
Sonuç olarak pilotlara yapılan bir anket vasıtasıyla bulgular ortaya konulmuş, varolan stabilizasyon kriterlerinin uygulanmasındaki eksiklikler belirlenmiş ve kurallara belirli güncelleme yapılması için önerileride bulunulmuştur.

Abstract:
There are more than 100.000 landings have being done in one day. Aviation industry is exponentially developing so aviation authorities are revising and publishing new rules to improve and maintain the safety at the maximum level. In spite of these rules, there are always risks that can never go away. Aviation safety departments always study to decrease and manage that risks in order not to have accidents. So we can say that the 'safety' is the most important thing when we talk about aviation sector.

Many approach and landing accidents have been investigated thoroughly over time, and much is known about contributing factors. Research and analysis of go-around decision making have been conducted primarily from the psychosocial science perspective to gain an understanding of the psychological drivers of noncompliance, and to identify corrective steps that can be taken, based on science. Approach and landing is the most common phase of flight for aviation accidents, accounting annually for approximately 65 percent of all accidents.

Aviation accidents mostly occur during approach and landing phases of the flight. 65% of all accidents are approach and landing accidents in one year. According to 16 year study that the  "Flight Safety Faundation" made, 83% of these accidents could be avoided if the crew had go around maneuver. When we calculate we can obtain that 54% all accidents could be prevented if the crew decided to go around rather than continue to land.

It is generally felt that an unstable approach is the primary cause of landing excursions. However, just over half of the landing excursions followed a fully stable approach; in these instances, the flight became unstable only during landing. 

A critical industry policy designed to help prevent such accidents is the go-around policy. Interestingly, the collective industry performance of complying with go-around policies is extremely poor, approximately 3 percent of unstable approaches result in go-around policy compliance. Why is a critical policy designed to prevent the most common type of accident ignored by flight crews, and why is that policy not being managed effectively by management? This thesis is searching answers to these questions.

Stabilization criterias are very important guide for flight crews to know when to go around if something happens throughout the approach and landing phase. These criterias are designed and still being improved to avoid critical accidents. Unstable approach is the approach that one or more significant stability criterias are missing. Unstable approach is mostly the main reason of approach and landing accidents.

3.5% to 4% of all approaches are unstable approaches. However only 3% of unstable approaches end up with a go around maneuver, the rest 97% continue to land. Although the Airline Companies  are encouraging flight crews to maintain stabilized approach and landing conditions, and apply go around maneuver if necessary to minimize the most common accidents, the numbers show that the applicability of the criterias are very low.

Improving the go-around compliance rate holds tremendous potential in reducing approach and landing accidents. The go-around itself is not without risk. There is an increased risk in loss of control events during a go-around compared to exposure with all other phases of flight.

It was also intended to improve our understanding of the risks associated with executing go-arounds and to make recommendations to improve compliance and mitigate risks associated with the go-around maneuver itself.

Not all unstable approaches carry the same level of inherent risk, and based on the different objective environments from approach to approach, there can be a conflict between these and the singular prescriptive company go-around policy, as indicated by the pilots' disagreement with company go-around policy thresholds. Once a pilot is outside the prescriptive box of go-around policy and has made the decision to continue the approach, he is left to his individual risk assessment method, whatever that may be, to determine his personal risk threshold, without guidance. 

Robust prescriptive policies that allow for some guided, open analysis of risk and decision making can offer a solution to these cases in which the objective environment and stated policies do not align well.

For example, if a company's go-around policy says that a flight crew must go around in all cases if the aircraft has not touched down within seven seconds of crossing the threshold, the pilots likely would view the importance of that policy differently, depending on the conditions of the day. They would likely be more in agreement with the policy for an approach to a shorter runway that was contaminated and had a slight tail wind than for an approach to a longer, dry runway with a slight head wind. 

If the policy is written to allow some deviation from the seven-second requirement, under some guiding principles, pilots will agree with the policy more often. In this example of the short contaminated runway, the pre-descent briefing should include a statement that there would be no modification of the seven-second rule, whereas in the case of the dry, long runway, the briefing may include an allowance to increase that timeframe to 10 seconds. 

It is important to emphasize that these allowances should follow a guided process laid out by the company, and that the policies remain predominately prescriptive. In this example, guiding principles may be that all crewmembers agree in advance of the modification, and that the landing distance available exceeds the landing distance required by a predetermined percentage.

This thesis's content areas are general view of the approach and landing accidents occured in the World and the statistics of studies about unstable approaches that resulted in accidents to attract notice to this important issue. According to this content, this study searches for why flight crews still decide to land when they violate the stable approach criteria and break the rule of go around. Also investigation of sustainable stablilization criterias and its' practicability by the flight crews is made.

The design of this study enabled us to look at the differences between those pilots who were compliant with their companies' policies and those who were not, according to objective and subjective measures. There are tables that shows data for the demographic, flight operational and objective factors present in the unstable approach events reported by pilots.

As a conclusion, a survey is performed among the several airline pilots and results with realistic datas are shown. There are also significant suggestions are made for companies and industry that would have an important status in the aviation future.  By these datas the Airline Companies and the aviation industry can cover the deficiencies in the stabilization criteria and update them to improve applicability.