Sunday, April 26, 2015

Bird Strikes

‘Bird Strike’ is a term used to define collision between birds and vehicles. In aviation it refers to a bird’s collision with aircraft during any phase of flight, whether it is a take-off run or a landing roll, bird strikes have always been a serious concern. Comparatively there are not many reported accidents caused due to bird strikes yet there are thousands of incidents which result in major economic and reputation losses of the operator as well as the airport authority.

Impact on Aviation

Although not always resulting in a crash or accident bird strikes do pose a significant threat to aircraft safety. Monetary losses due to expensive aircraft repairs and increased grounding time are yet another negative contribution from bird strikes. In USA alone 600 million USD are spent each year for damage caused by birds and wild life strikes. As an example If we look at the graph of statistics of Bird Strikes reported in USA from1990-2013 (Source: FAA) we can conclude that bird strike is a constantly rising factor and has increased nearly 6 times in 25 years. This increased number of occurrences is due to increased number of flights as well as a pronounced increase in number of birds itself. One more thing to note is that on average only around 9.5% (13497) strikes have caused damage to aircraft, this is also a big number for the operators if maintenance cost is considered.

Reducing the Risks

Bird strikes can never be eliminated, yet they can be controlled/reduced generally by these steps:
1. ReportingBird Strikes are specific to aerodrome location, season, bird types etc. and this important data can be collected by inputs from occurrences. Reporting is the most important part of identifying and mitigating the risks involved in a certain location during a certain period of the year. Proper reporting should be made mandatory for every strike, no matter if it has caused damage or not, and then the collected data should be analysed for a trend of strikes. Generally there is a pattern of these events depending upon several factors, and once the pattern is established and understood it would be easier to reduce the number of strikes. For example see the 5 yearly charts below that show strikes in the UK, the general pattern is increased number in strikes during the month of June-July. The interesting thing is this chart follows nearly the same trend either from 1990s or the 2000s i.e. curve’s peak is highest during June-July       
 
 2. Habitat ManagementBird hazard cannot only be controlled by airport authorities, a firm environmental control is required and for that purpose a proper habitat management program should be followed keeping following key points a primary concern:
a) People living in the vicinity of the airport shall be informed of the risks involved from bird strikes and educating them to avoid attracting birds, like by planning waste disposal sites away from the runways
b) Ponds and lakes should be netted, streams should be drained.
c) Proper length of grass within the aerodrome should be maintained: if too long it would encourage birds for nesting, and too short will allow them to roost.

3. The “Scarecrow” theoryThere are several ways of scaring birds away once it has been analysed that what type of birds are causing trouble in a certain region.
a) Spirals
These white painted spirals apart from telling the ground crew about running engines play a vital role in distracting birds away as the appear as white flashing signals to the bird discouraging them to get ingested.
According to an AOPA report: One air carrier detected slightly reduced bird strike rates after painting the jet engine spinners white. Anything that increases contrast seems to help birds to avoid airplanes. Birds see colors in the ultraviolet range beyond what humans can see, and that information may be useful in future research on markings for aircraft that could reduce bird strikes
b) Distress Calls and Gunshots
Once the type of birds have been identified using previous strike reports birds can be scared away playing distress calls on loud speakers by using Bio-Acoustic Systems.  Another method is to fire blank bullets to shoo' the birds away. 



Conclusion

Bird Strike issues should be addressed seriously and appropriate actions should be taken as this is a factor that can be controlled using some easy techniques and once a proper safety plan has been established and maintained, it will save the operator as well as the authorities of monetary and reputation losses.

Sunday, March 22, 2015

Android Applications for Aircraft Maintenance Mechanics/Technicians/Engineers

Hi Everyone,
As android system is being popular day by day with free or pocket friendly applications, having millions of users, I thought it beneficial to share some cool must have apps for Aircraft Mechanics. I am adding some now, and will add more gradually.
Everyone is most welcome to suggest more apps and benefit others.

Magazines and Articles:

1. FAST by Airbus



Description (as on Google Play)
This free Airbus technical magazine stands for Flight, Airworthiness, Support and Technology. The articles are written by Airbus engineers, maintenance staff, pilots, instructors, upgrade services, etc. Its objective is to spread over the aviation community, airworthiness authorities, schools and universities, Airbus’ philosophy on technical, research & technology, maintenance and environmental matters, to name a few. The subjects vary from one edition to another for Airbus’ entire fleet.

Download FAST by Airbus

2. Aircraft Maintenance Technology

Description (as on Google Play)
Aircraft Maintenance Technology (AMT) magazine is written by aircraft maintenance professionals for the aircraft maintenance community. Editorial is focused on the latest technology and maintenance best practices from all segments of aviation and aircraft maintenance. Regular columns include Staying Legal, AMTSociety Mx Logs Update, and Industry Viewpoint. Special focus on tools is presented in the quarterly Tools & Equipment. AMT reaches more aircraft maintenance professionals than any other media with our print circulation and digital products including a weekly eNewsletter; quarterly webinars; and eMilitary Product News.

Download AMT Magazine

Sunday, November 23, 2014

What is the Boundary Layer?

INTRO


In fluid dynamics, Boundary Layer is a THIN (less than an inch), SLOW MOVING (nearly zero velocity) layer of moving fluid which is in contact with the surface of any object (car, boat, aircraft, golf ball etc). It STICKS and tends to wrap around the object due to the VISCOSITY of the fluid.





Yes! You guessed it right ZERO VISCOSITY (ideal) means NO BOUNDARY LAYER!

Being Aircraft Mechanics we are naturally more concerned about Aircraft!
Let's see how Boundary Layer affects our airfoils and how we control it to change overall lift and controllability characteristics

AERODYNAMICS
When the free air stream comes into contact with the airfoil, the flow closer or in contact with the airfoil tends to slow down owing to it's viscosity and surface friction with the surface of the object. This thin layer of airflow is termed as the BOUNDARY LAYER. The boundary layer consists of several layers flowing over each other, each layer is a bit faster than the layer below it, hence there is a gradual increase in velocity from airfoil surface to the free stream (see Fig 1)

Figure 1 - Gradual Increase of Layer Velocity from Surface to the Free Stream


As the boundary layer is slow-moving in nature it has low Kinetic Energy. This lower energy results in it's separation from the airfoil (Fig 2).

Figure 2

NOTE: The static pressure increases from the thickest point of the airfoil to the trailing edge (See Fig 3), thus the boundary layer needs more energy to flow to the high pressure area or it will separate from the airfoil.
Figure 3

MORE KINETIC ENERGY means FARTHER SEPARATION POINT

Thus to delay the separation point, or to get the maximum positive effects from the airfoil (lift, controllability), we try to provide more energy the boundary layer.
To energize the boundary layer devices like SLOTS, VORTEX GENERATORS are used.


P.S. I have kept the post simple, there is much more to be added to this article, but this one is to give just some general concept of the Boundary Layer. You can always suggest improvements and help others!

Monday, November 17, 2014

What are Vortex Generators and What purpose do they serve?

There is a lot of information over the internet about the purpose of Vortex Generators. I will shed light on just some important notes you should keep in mind as an Aircraft Mechanic, I will try to explain more details later (if necessary) bu updating this post

Before proceeding I assume you are accustomed with the following terms:
Boundary Layer, Laminar/Turbulent Flow, Stall

VORTEX GENERATORS

Vortex Generators are small aerodynamic devices, generally fitted to the leading edge of wings (including ailerons, elevators etc).
The laminar flow tends to separate from the wing at some point (Transition Point) behind the leading edge, as the angle of attack increases the transition point moves forward, this can lead to a situation which will ultimately cause the wing to stall.


Transition Point - The point at which Laminar Flow leaves the airfoil causing a Turbulent Flow in result, so there is a transition from Laminar to Turbulent Flow at the Transition Point


HOW DO THEY WORK
The boundary layer of Laminar Flow is low in energy as compared to that of Turbulent Flow, thus to energize the boundary layer vortex generators are used.

Simple Operational Principle: As the name implies, when the airflow passes over the vortex generators they generate small vortices, these turbulent vortices energize the boundary layer and helps it stick with the airfoil surface thus delaying the formation of transition point/region.

Saw this interesting photo on a website www.aerospaceweb.org which can help you understand the phenomenon


Note: I tried to keep it short and simple. More information can be provided upon your request. Kindly suggest me updates for this article to make it better! 

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