Engine vibrations-causes and types explained

On Dec 5,2019 a routine Indigo flight 6E-236, from Mumbai to Bengaluru had to be diverted back to Mumbai after a caution advisory was alerted in the cockpit. In what could be termed as the second such occurence, the A320 neo had to be diverted due to abnormal vibrations on one of its PnW engines. Both aircrafts were subsequently grounded pending approvals for flying again.

There are many reasons that can be attributed to the cause of engine vibrations and they are not uncommon during any routine flight. Extension and retraction of landing gear, spoiler deployment, free play in movable systems-all have their own role in causing vibrations. Bottomline is, the flight crew need to be adept at recognizing the cause and effects of airplane vibrations so that effective action can be taken to maintain flight safety and airframe integrity.

**Meggitt

What is vibration and what are its types?

Vibration is defined as the oscillatory or any periodic motion of a rigid/elastic body from a state of equilibrium. When the frequency and magnitude varies, it is termed as "random vibrations".

Further sub-divided into 3:

1.Buffet: Often experienced during deploying spoilers and turbulence, it is generally random and caused by airflow separation.

Aircraft buffeting

2.Flutter: An unstable condition that often leads to structural failure, caused by the excitation of the natural frequencies of the structure over which air flows which may proliferate and cause structural failure.

Aircraft flutter

3.Noise: Vibration that sets the air particles in motion-Known as "harmonics" when it sounds musical and "random"  when the noise is unmusical or haphazard.

Causes

All vibrations have their associated corresponding frequencies and magnitudes which further categorise them into:

1.NORMAL VIBRATIONS: Low level vibrations result when external forces, such as air, flows over control surfaces . This might be perceived as simple background noise as opposed to when the aircraft flies through turbulence where the vibrations are larger and can be clearly felt. Mechanical operation of pumps also produce normal vibrations as does engine operations at certain spool speeds.

2.ABNORMAL VIBRATIONS: Any vibrations with a sudden onset, accompanied by noise are categorised as abnormal. Engine rotor imbalance, mechanical equipment malfunction, airflow distortion over control surfaces, wear and tear of mechanical parts , all lead to abnormal vibrations. They may/may not be associated with prior events and are rarely caused by structural failure or unstable power supply systems.

3.FLUTTER: Vibrations emanating from the airplane rather than the atmosphere, results in the formation of flutter. Also closely related is limited cycle oscillation (LCO), which is most often caused by excessive free play within the flight control surfaces.

Expected flight crew response

Detection and perceiving airplane vibrations can be tricky as every event is different and flight crews have their own ways of defining their perception of an abnormal event . That said, abnormal vibrations on an engine is easily recognised and cannot be mistaken as there are special accelerometers installed to measure spool vibrations.

The highlighted area shows the engine vibrations

Analyzing the situation for a brief period of time would be an ideal crew response to an unexplained vibration.

Airspeed and engine speed should be ideally reduced as long as it doesn't compromise with the performance characteristic-basically eliminating further added stress on the airplane.

Comparision with previous incidents on the same airplane can reveal the cause of the anomaly and this should be done immediately following the report of the incident by the flight crew. If this comparison leads to unfruitful results, an entire inspection of the aircraft is made.

COVER: Pratt and Whitney Canada

AirAsia India's Ahmedabad-Chennai flight and IndiGo's Bengaluru-Vadodara flight came within 8 km of each other with 300 ft vertical separation between them over Mumbai airspace on January 29, according to an Aircraft Accident Investigation Bureau (AAIB) report.

The probable cause for this "serious incident" was the air traffic controller's "loss of situational awareness", the report released earlier this month said.

Another probable cause was that the situation was evaluated by the controller at the Mumbai airport "under the influence of preconceived mind", it said.

Explaining the incident, the report said that most of the flights that go from Ahmedabad to southern India overfly Bhavnagar. However, on January 29, the AirAsia India flight was on a route that is usually taken by planes descending to land at the Mumbai airport.

Due to the change in routing by AirAsia India flight and "direct routing" of the IndiGo flight that was coming from the opposite direction, the "heading of both aircraft became reciprocal to each other" but at different altitudes, it mentioned.

At this time, when there was enough lateral separation, the automation system of the air traffic controller issued a "predicted conflict warning". However, the controller did not respond to the visual "predicted conflict warning", the report stated.

The controller presumed that the AirAsia India flight was following its usual route over Bhavnagar due to his or her previous experience. Therefore, the controller perceived that the AirAsia India flight is not in the immediate vicinity of the IndiGo flight, it said.

By the time the controller realised the situation, the Air Asia India flight had reached 38,008 ft while the IndiGo flight was flying at 38,000 ft. The AirAsia India flight continued its ascent as its Traffic Collision Avoidance System (TCAS) in the cockpit issued a warning to the pilots, it said.

"It (Air Asia India flight) was at 38,396 feet when the conflicting traffic was resolved," the report said. The IndiGo flight maintained an altitude of 38,000 feet.

"The minimum separation between both the aircraft was recorded as 8 km laterally while (it was) 300 feet vertical(ly) when the AirAsia India flight was below the IndiGo flight and it was 6.5 km laterally when the vertical separation was 500 feet when IndiGo flight was below the AirAsia India flight," the report mentioned.

It recommended that suitable corrective training may be imparted to the controller with an emphasis on situational awareness and the importance of warnings generated on the automation system.

"It is recommended that Airports Authority of India may reassess the volume of traffic in all sectors which were withdrawn due to less number of traffic during the lockdown and may implement sectors as before pandemic," it stated.

The report said the minimum separation between both aircraft was recorded as 8km laterally when the climbing AirAsia aircraft was 300ft below the IndiGo aircraft and it was 6.5km laterally when the AirAsia aircraft was 500ft above IndiGo aircraft after having crossed its path.

What the regulation says

Perhaps the most important separation when it comes to aircraft spacing, is the vertical separation. The ICAO States that all aircrafts below 29,000 ft be separated by 1000ft while those above 29,000 ft should be separated by 2000 feet-applicable to all IFR flights. In order to fly more optimum flight paths without compromising safety leading to fuel savings advocated the need to reduce the minimum from 2000 ft to 1000 ft. Finally in 1988, following extensive studies and research, ICAO approved the changes and mandated that only RVSM approved aircrafts may fly through this airspace and non-RVSM aircrafts “may” travel through RVSM route provided authorisation is obtained from the concerned ATC and guidance is given at all times. Two aircrafts on the same course have to be laterally separated by atleast 10 nautical miles and vertically separated by 1000 ft.

RVSM

The DGCA India Civil Aviation Requirement (CAR) prescribes the following monitoring instruments to be installed by all Indian registered aircrafts:

ACAS IITransponder

These instruments help Flight crews in adverse situations. Introduction of ACAS has made flying safer than ever as it helps in further minimising scope of human error.

Air India will start operating a weekly flight between Indore in Madhya Pradesh and Dubai in the UAE from September 1, Union Civil Aviation Minister Jyotiraditya Scindia said on Monday (August 23). Scindia is a Rajya Sabha member from Madhya Pradesh.

"Great news for the people of Indore! Air India is going to start new services between Indore and Dubai that will operate once a week (on Wednesday) currently," the minister said on Twitter.

https://twitter.com/JM_Scindia/status/1429827819756945410

Financial bids for disinvestment-bound Air India are likely to be received from qualified interested bidders (QIBs) by September 15, Minister of State for Civil Aviation V K Singh had said on July 22 in Lok Sabha.

The Centre had invited Expression of Interests (EoIs) for Air India on January 27, 2020. The last date of submission -- after multiple extensions due to the COVID-19 pandemic -- of EoIs was December 14, 2020.

Govt targets Air India handover by Dec 

The Department of Investment and Public Asset Management (DIPAM) has expressed a strong hope that the process of financial bidding for the strategic disinvestment of Air India will be held next month, while also maintaining that the government plans to hand over the airline by December this year. 

A source in the department also indicated that the Bharat Petroleum Corporation (BPCL) transaction will be completed only by the end of the current financial year and the financial bidding for the same is likely to be completed by December. 

DIPAM also clarified that Cairn moving court in the southern district of New York against Air India to enforce a tax arbitral award will not dampen the investor sentiment for strategic sale and in case of need, the government will give a guarantee to the prospective bidders against the same. 

Financial bids for disinvestment-bound Air India are likely to be received from qualified interested bidders (QIBs) by September 15

The source pointed out that BPCL's strategic sale has been impacted by the second wave of the COVID-19 pandemic and will see the light of the day by the end of the current financial year. Meanwhile, the process of due diligence is currently going on in the case of the Shipping Corporation of India.  

The strategic sale of Air India was approved by the Cabinet Committee on Economic Affairs in February 2019, while that of BPCL, SCI and Container Corporation of India were approved in November 2019. The government plans to raise Rs 1.75 lakh crore in the current financial year through disinvestment and strategic sale.

The Secretary-General of ICAO

Juan Carlos Salazar of Colombia officially assumes the office of the ICAO Secretary-General, succeeding Dr. Fang Liu of China who has held this position since 2015. His role comes at a critical time when the air transport industry is still recovering from diminished air travel and tourism and fewer routes amidst the ongoing Covid-19 pandemic. Mr. Juan is a former director-general of Civil Aviation for Colombia and possesses more than 26 years of experience in civil aviation, public policy, and the management of large and complex organizations. As a Head of the Secretariat and chief executive officer of the Organization, Mr. Juan is responsible for the general direction of the work of the Secretariat, the Secretary-General. The ICAO comprises specialized international staff working in the international aviation field. The Secretary-General serves as the Secretary of the ICAO Council and carries out duties mandated by the council, in addition to making periodic reports of the Secretariat to the Council.

Uniting Aviation

Assuming Office

It is a great honor to be assuming this role at this time and to have the opportunity to help governments and ICAO play an important part in how this sector builds back better and recovers from the global pandemicMr. Salazar

With global aviation hitting a major roadblock, Mr. Salazar has vowed to support developing States that have suffered the most devastating impacts of the pandemic. He has also stated that he would further strengthen ICAO’s global presence through its Regional Offices and support for key regional priorities.

The ICAO Council is very pleased to welcome Mr. Salazar as he officially assumes his new role, and as Council President, I look forward to working closely with him in helping to modernize ICAO and make it a more responsive and efficient agency at the service of its 193 Member StatesICAO Council PresidentSalvatore Sciacchitano

Mr. Sciacchitano also expressed his appreciation towards the previous ICAO Secretary-General, Dr. Fang Liu, in recognition of her dedication and efforts during her two-year term as Secretary-General.

ICAO

The ICAO was officially formed at the Chicago convention on 7 December 1944 in Chicago, Illinois. At the time 52 countries signed the convention and by 1947, it officially became an agency of the UN under its Economic and Social Council. (ECOSOC). The Secretariat has six main divisions.

1. Air navigation bureau2. Air transport bureau3. Technical Co-operation bureau4. Legal affairs5. External relations bureau6. Administration and services bureau

List of Secretary General

SECRETARYNATIONALITYTERMJuan Carlos SalazarColombiaFrom August 2021Fang LiuChina2015–August 2021Raymond BenjaminFrance2009–2015Taïeb ChérifAlgeria2003–2009Renato Claudio Costa PereiraBrazil1997–2003Philippe RochatSwitzerland1991–1997Shivinder Singh SidhuIndia1988–1991Yves LambertFrance1976–1988Assad KotaiteLebanon1970–1976Bernardus Tielman TwigtNetherlands1964–1970Ronald MacAllister MacdonnellCanada1959–1964Carl LjungbergSweden1952–1959Albert RoperFrance1944–1951

Dr. Shivinder Singh Sidhu

Wikipedia

SEVENTH ICAO SECRETARY GENERALTERM OF OFFICE: 1988-1991  

Dr. Shivinder Singh Sidhu was born on 13 October 1929 (India) and was appointed as the Secretary-General of the Organization on 1 August 1988. He held advanced degrees in Economics and Public Administration and a Doctorate of Philosophy.

Achievements

Held a number of senior posts and represented his Government at numerous bilateral and inter-governmental negotiations in various fieldsThe Chief Delegate of the Indian delegation to a number of international conferences, Dr. Sidhu was also elected as the President of the Twenty-sixth Session of the ICAO Assembly in 1986Served as the Director of India's Civil Aviation Administration (February 1985 to October 1987), Chairman of Air India and Indian Airlines, and as Secretary to the Government in the Ministry of Civil Aviation.

Dr. Sidhu passed away on 25 October 2018 at the age of 89.

COVER: Wikipedia

A management system which makes optimum use of all available resources (equipment, procedures and people) to promote safety and enhance the efficiency of flight operationUK Civil Aviation Authority

How did it come about? A brief history

On December 29, 1972, an Eastern Airlines Lockheed L-1011 with 176 people aboard crashed in Florida just minutes away from touching down in Miami International airport. Extensive investigation reports attributed the cause of the accident to distraction and mayhem in the cockpit. The flight crew were apparently focused on an un-illuminated landing gear indication bulb, distracting them from the rapid descent the aircraft was subjected to-leading to the crash. As a response, British aviation psychiatrist and professor, Elwyn Edwards, developed the first ever " Cockpit resource management".

The NASA built upon Dr. Edward's principles and concluded that primary causes of aircraft accidents were human errors resulting from improper interpersonal communications and lack of decision making skills. Thereby, it became imperative that everyone involved be trained in effective management of resources and interpersonal communication to complete every flying task safely.

When is CRM used?

AOPA

Right from the moment when the crew meet in the briefing room all the way until they checkout for the day-day-CRM is applied. Accurate environmental perception and situational awareness are key to effective CRM.CRM can be thought of as a combination of:

1.Communication2.Problem solving3.Situational awareness4.Decision-making5.Teamwork

Situational Awareness

One’s ability to accurately perceive what is in the flight deck and outside the aircraft, comprehend the meaning of these elements and be able to project their possible status in the near future-UK CAA

SKYbrary

Often times it is possible that the crew might believe they have a clear perception of the current situation while in fact, they might not. For instance, believing they are correctly lined up with the runway for landing while in fact they actually might be configured with the parallel taxiway. Hence there is a continuous need to keep questioning whether your perceived reality is actually correct or not. It is to be realised that pilots are humans too and are prone to making errors. This is called situational awareness. While it can take a long time to build up this habit, it will only take seconds to lose it.

Fatigue awareness and workload have also found way into CRM over the recent years. At times, the cockpit could get busy, communicating back n forth with the ATC. It is very easy to get distracted in such scenarios and hence effective CRM ensures the pilots are attentive at all time.

Summing up

Long story short, CRM is two or more people working together as one. This isn't limited to pilots alone as everyone involved in the safety of the flight, including the ATC, are part as well.With increasing reliance on automation, effective CRM has become all the more important as, contrary to the popular belief, automation actually requires more vigilance than otherwise.

Sterile Cockpit Rule

BLOG-SMITH SYSTEM

Imposed by the FAA in 1981 following a string of aviation accidents, the sterile cockpit rule stipulates that during critical phases of a flight and all other flight operations conducted below 10,000ft MSL, all unnecessary talk and commotion is to be avoided in the cockpit.

Air India bids adieu to "Sir" in the cockpit

DNA India

In a bid to improve CRM in the cockpit, Air India express has asked its first officers now to adress the PIC(pilot I'm command) as "Captain" or by their first name and not address them as "sir".

The circular issued regarding the same refered to an Air India Express incident at Trichy in October 2018 where the aircraft hit the lower portion of a ground-based navigation aid before finally taking off for the destination. Apparently, the cause of the mishap was attributed to poor CRM in the cockpit, essentially communication failure between the two pilots. According to regulatory bodies, the proposed move will bring about a more informal environment in the cockpit and reduce trans-cockpit-authority-gradient.

Hyderabad-based GMR Group is investing INR 20,000 crore to expand existing airports and develop new aerodromes, Chairman GM Rao said in the company’s latest annual report.

“Airport Development and Construction: GMR Group has set benchmarks for the development of world-class airport infrastructure. The company is currently investing approximately INR 20,000 crore to expand the existing airports and develop new airports,” he mentioned.

The infra major’s airport business comprises four operating airports including Indira Gandhi International Airport, Delhi, Rajiv Gandhi International Airport, Hyderabad, Bidar Airport, Karnataka and Mactan Cebu International Airport in the Philippines.

GMR Group is investing INR 20,000 crore to expand existing airports and develop new aerodromes

In addition, GMR Group has commissioned Mopa Greenfield Airports in Goa and Crete International Airport in Greece, which is currently under construction. The company had also signed the concession agreement for a Greenfield Bhogapuram International Airport in Andhra Pradesh in June 2020. Development works including earthworks for the project are in progress.

Currently, GMR’s Delhi Airport is expanding its airside infrastructure and terminal capacity to 100 million passengers annually. The entire Phase 3A expansion is set to be completed by June 2023, Rao mentioned.

Delhi Airport has also raised $450 million in the form of overseas green bonds to meet the funding needs of the expansion project and to repay the $289 million bond maturing in FY21-22.

GMR’s Delhi Airport is expanding its airside infrastructure and terminal capacity to 100 million passengers

Further, as part of its capital expansion works, GMR Hyderabad International Airport Ltd (GHIAL) has commissioned four rapid exit taxiways, and has completed rehabilitation works of the main runway in the first quarter of the current fiscal.

"GHIAL is well underway to complete its expansion to a capacity of 35 million passengers annually by September 2022," Rao said. GHIAL raised 5-year bonds amounting to $300 million in the previous fiscal to meet the funding requirements of the expansion project.

In February 2020, Goa Airport resumed construction and development works on the site after the Supreme Court gave its reaffirmation of environmental clearance to the project. The airport is expected to be commissioned by August 2022.

Separately, after the Nagpur bench of Bombay High Court ruling, GMR said it is would develop Nagpur airport into a “world-class facility”. The court had recently set aside an order of Mihan-- a joint venture of Maharashtra Airport Development Company and Airport Authority of India. Mihan, in March 2020, had cancelled the award letter issued to the GMR group, but the high court has asked it to execute a concession agreement with the GMR group in six weeks. 

The existing facilities at Nagpur airport have been operating close to the maximum capacity, handling a total of about 3 million passengers and 9,500 metric tonnes of cargo during the financial year 2019-20.