Air France Flight 447 crash

         Air France Flight 447 was a scheduled airline flight from Rio de Janeiro to Paris that crashed into the Atlantic Ocean on 1 June 2009, killing all 216 passengers and 12 aircrew.The investigation is still ongoing, and the cause of the crash has not yet been determined, but a briefing released by the BEA on 27 May 2011 revealed that the aircraft crashed following an aerodynamic stall. It further revealed that for about a minute prior to the crash there were inconsistent readings in the pitot tubes. The cause of the faulty readings is yet to be determined, but a theory is that ice formed on the pitot tubes, which would have caused them to freeze, giving inconsistent measurements owing to their reliance on air pressure measurements to give speed readings. Pitot tube blockage is suspected of having contributed to airliner crashes in the past such as Birgenair Flight 301 in 1996.

         The investigation into this accident was severely hampered by the lack of any eyewitness evidence and radar tracks, as well as by difficulty finding the aircraft's black boxes, which were located and recovered from the ocean floor two years later in May 2011.

         The accident was the deadliest in the history of Air France. It was the first fatal accident to befall an Airbus A330 airliner while in passenger service.

DETAILED REPORT ON THE CRASH

          French investigators have disclosed that the crew of Air France flight AF447 maintained nose-up inputs to the aircraft even after the Airbus A330 entered a stall.The inquiry has also revealed that the pilots set engine thrust variously to go-around power and idle as they battled to rescue the jet.

          In an update to the loss of the A330 over the South Atlantic two years ago the Bureau d'Enquetes et d'Analyses has detailed the last few minutes of the flight. BEA said the aircraft climbed from its cruise altitude of 35,000ft towards 38,000ft and stalled, but added that the flying pilot "maintained nose-up inputs" to the controls.BEA confirms that the captain had left the cockpit to rest, about eight minutes before the emergency on 1 June 2009, having discussed with the relief crew possible turbulence ahead of the aircraft.

Recovered black box data and details inferred :

LAST SIX MINUTES OF AF447

          The pilots altered course slightly, about 12° to the left, and as turbulence increased they opted to reduce speed to Mach 0.8.

          About 2min later the aircraft's autopilot and autothrust disengaged, and remained so for the rest of the flight. This would have put the jet into 'alternate' law, meaning it lost its angle-of-attack protection.

          The aircraft began to roll to the right, and as the pilot made a nose-up left input, the A330's stall warning sounded twice - an indication that the aircraft had exceeded a critical angle-of-attack threshold.

          The primary flight display on the captain's side showed a "sharp fall" in speed from 275kt to 60kt, and the aircraft's angle of attack "increased progressively" beyond 10°.

          While the jet had initially been cruising at 35,000ft, investigators stated that the aircraft climbed, with a vertical speed of 7,000ft/min, heading towards 38,000ft.

          The pilot made nose-down inputs as well as inputs for left and right roll. The vertical speed fell back to 700ft/min, the displayed speed "increased sharply" to 215kt, and the angle of attack reduced to 4°.

          In its update the BEA said the non-flying pilot "tried several times to call the captain back".

          There was another stall warning and the BEA said the stall warning sounded again. The thrust levers were positioned for take-off/go-around power but the flying pilot "maintained nose-up inputs".

          Angle of attack continued to increase, it added, and the trimmable horizontal stabiliser increased from a 3° nose-up position to 13° nose-up - where it stayed for the rest of the flight.

          The aircraft reached 38,000ft - its maximum altitude - with its angle of attack having increased to 16°.

          AF447's captain returned to the cockpit - just 90s after the autopilot had disengaged - by which time the aircraft had started its fatal descent.

          As it passed through 35,000ft the angle of attack increased to more than 40° and the A330 was descending at 10,000ft/min. Its pitch did not exceed 15°, its engine power was close to 100% of N1, and the jet oscillated with rolls of up to 40°.

"        The [flying pilot] made an input on the sidestick to the left and nose-up stops, which lasted about 30s," said the BEA.

         Just 20s after the captain returned to the cockpit, said the BEA, the thrust levers were set to the 'idle' position, with the engines delivering 55% of N1.

Measured angle of attack values, the BEA pointed out, are only considered valid when the measured speed is above 60kt. It said that the angle of attack, when valid, always remained above 35°.

          AF447's had turned almost a three-quarter circle to the right during the emergency, and - having descended for 3min 30s - it struck the ocean surface with a ground speed of just 107kt, a nose-up pitch attitude of 16.2°, with a heading of 270°.

BEA stated that the aircraft stalled but that the inputs from the flying pilot were "mainly nose-up". It added that the engines "were operating and always responded to crew commands".

Technical evaluation by FAE

Though the reasons has not been cornered to either technical fault or pilots errors, the first hand reports from blackbox data seems to suggest the error was on the pilot side and also the stall recovery procedure followed was not the appropriate one for the existed condition.

PROCEDURE THAT MUST HAVE BEEN FOLLOWED

1. Following the stall when the aircraft is on recovery, If the engines are set to full power an aircraft with engines mounted in low thrust line will tend to pitch up the aircraft which may increase the risk increased Angle of attack(the same condition persisted in AF447).
2. Therefore it is precautions to set back engine power and allow aircraft to pitch down for a short course 
3. Then gradually increase power and recover from stall.
4. This procedure is followed only in high altitude stall recovery since this procedure involves in loss of altitude which is not possible when in low altitude.

-Nirmal Kumar.U

FAE

 

(The content are based on articles published in various sites and magazines and the above post is on personal evaluation of the author over the crash )

Lift generation on Delta wing aircrafts

We are well aware that in aircraft with straight and unswept wings, flow separation results in a poor ratio of lift to drag, and vibration due to instability of flow. However in aircraft with swept wings(Delta wings also) the separated flow will roll up into a pair of stable cone-shaped vortices. Unlike the bound vortex of a conventional wing, which merely represents the circulatory tendency, these are real vortices of swirling mass of air like in whirlwind.

the flow separates in the leading edge and rolls up into pair of vortices

The separated vortex flow represents an alternative method of lift generation. The airspeed in the vortex is high, and so the pressure is low. Thus, lift is still produced by exposing the upper surface to a low pressure than the lower surface; this low pressure is produced due to the vortex motion above it.

At low angle of attack the generation of lift is same as in the convention wing the effect of vortex lift comes into play only in high angles of attack.

Cl vs angle of attack (note that the Cl increases in the high angles more compared to conventional wings)

The Slender delta-winged Concorde was designed to fly with separated conical vortex flow in normal flight conditions. The leading edge is sharp in order to favour flow separation even at small or moderate angles of attack.

The strong conical vortex forms over the leading edge of the slender delta wing Concorde can be seen by vapour condensation

This conical flow may be thought as an controlled separation. When lift is generated this way, the wing will not stall in the conventional sense, and the lift will continue to increase for angles of attack up to 40 degrees or so. At the higher angles, the vortices start to break down, and the lift falls off.

This method of lift generation is used in supersonic flights and it also have other advantage of postponing the sonic drag rise.

"Separated vortex flow is the reason for keeping paper darts flying across, this shows that this method is also suitable for producing lift in low speed flights and interestingly the slender delta aircrafts, based no doubt on the paper darts" 

            The Indian Air Force plays a crucial role in securing Indian airspace and also in India's power projection in South Asia and Indian Ocean. Therefore, modernizing and expanding the Indian Air Force is a top priority for the Indian government.The minimum sanctioned strength of the IAF is 39.5 squadrons of combat aircraft, with a healthy level of 44 squadrons.However, this level was achieved only in the mid-1980s, with the acquisition of the Mirage 2000s, MiG-29s and Jaguars. In addition, at the time, most IAF aircraft were comparatively new, being less than 10 years old. Most of the older aircraft would have become obsolete by the mid-1990s, with the rest needing replacement by 2010.

            Aging aircraft were not replaced, for reasons mentioned below, which led to frequent crashes and attrition losses. The Force levels have fallen to 34 combat squadrons, a big worry for the IAF. Further phasing out of aircraft has meant that the IAF now operates only 32 fighter squadrons, which represents a serious depletion of force levels. Even with the planned MMRCA procurement, the IAF will reach sanctioned strength only by 2017.

            This has led to a threat to India's traditional numerical-superiority over Pakistan's air force, and erosion of its position as compared to China, another Asian power. The ratios of aircraft has fallen from 2.79:1 to around 1.30:1 and could potentially fall further to 1.15:1 in the coming years. For the first time, the PAF would be inducting BVR missiles with its purchase of 500 AIM-120C5 AMRAAM missiles. Pakistan's acquisition of 18 F-16C/D Block 52+ aircraft from the U.S., and future JF-17 Thunder production, along with China's much bigger and modernizing air force, has led to further concern from the IAF.

Indian MRCA

            The Indian Air Force Medium Multi-Role Combat Aircraft (MMRCA) Competition, is an ongoing competition to supply the Indian Air Force (IAF) with 126 multi-role combat aircraft. The Defence Ministry has allocated Indian 42,000 crore (US$9.32 billion) for the purchase of these aircraft,making it India's single largest defence deal ever made in history.

The six MRCA aircraft: Rafale, Typhoon, F-16C/D, F/A-18E/F, JAS 39 Gripen and MiG-35.

On 27 April 2011, the IAF shortlisted two of the six competing fighter jets — Eurofighter Typhoon and Dassault Rafale.

Though there were no official declarations about the deal and the evaluation results, I have certain things from articles and news paper which might have shortlisted other four Aircraft

F-18-manufactured by Boeing (USA) has been shortlisted because of engine issues and inadequate details

Gripen - manufactured by Sweden has been shortlisted due to inferior radar system

MIG-35 – manufactured by Russia came with great spirits, advanced technology and maneuverability, failed to clear due to poor engine performance during IAF trials

F-16 – Manufactured by Lockheed martin (USA) an proven multirole aircraft, failed due to two main facts that it has no future prospects and it’s with all our enemies

            All the above aircrafts are proven bests but lost in front of the beasts, the Euro fighter Typhoon and Dassault Rafale

Rafale

Dassault Rafale: This machine is highly agile and proven to be highly maneuverable out smarted others in a very good margin during IAF trials, It has an added advantage that it can be easily inducted by making fewer changes to the MIRAGE Hangar ( multirole aircraft purchased by India from Dassault which proved its strength in Kargil )   

Typoon

Eurofighter Typhoon: Highly agile and proven advantageous aircraft with its multirole capability and Political backgrounds favored this.

Official conformation about the deal is expected to be released soon.


-Nirmal

Best way of starting simulator

There are many games which will be very interesting and useful for aeronautical engineers, though an engineer dont ever need to fly an aircraft its always useful that an engineer knows basics of flying. It will put you ahead of any others near to you. Often you end up in failure by starting higher end simulator without having basic experience, its not jus like an NFS or any other race games that you take on a car to road and drift. Simulator games are made to provide shear reality and sometime real controls. For almost all these games keyboard is alone enough you dont really need an joystick or yoke.I have mentioned an simple way that may help you to start flying simulators

Here are the first four games i started with,

• Microsoft Flight simulator 2004(FS 2004)

FS 2004 is an simulator dedicated game which is the best for starting, here you find flying lessons and flight plans. All you need to do is to takeoff and land. This will be really interesting if you proceed in a correct way

• Wings over Israel  (WOI)

WOI is an exciting game and is not an simulator dedicated( 30% as simulator and 70% as an game), the only problem is that you will be able to fly planes but you wont be able to control or even fire your weapons without a proper guidance(you need basic knowledge on radar, missile types and its variants). This game wont be having a great graphics as you see in ACE combat in PS2, but will relay more on realism,so after basics in FS if you want to be an Airforce pilot you can direstly start this (we will later provide you details on request)

• Wings over Europe(WOE)

This is similar thing to WOI but will have more missions and some legendary aircrafts, once you know WOI , conrols are too easy in WOE

• Lock on

This game is the best one for those who came this course, the game will be too tough and controls will be very complicated. This can be categorised as 70% simulator and 30 as game. This game is designed with training where you must be trained and only then you can survive in missions. Again this game wont have great graphics but excellent in realistic controls.

Here is an easy way to start this today,

• First of all download FS 2004 from Internet , there are many sites where you can download this for free( you can find this here http://thepiratebay.org/torrent/3542624 )
• Once you install all you need is to make you free for at least two hours, once you start you will find many tabs, click on the getting started option where you will be guided through a video for using controls. Once you finish you will be knowing the basic controls of your flight through keyboard
• Then you go to flying lessons option, and select Student pilot, follow and Dedicate a couple of hours and you can then start it easy
• Once you finish then the next thing is when ever you select a flight you have to taxi it to runway and then takeoff, but the beginners will find this too though to take a plane to runway and will take-off from taxi way( i did this at first). So you can follow this Create flight > selected location > change location >  Runway/ starting position > active runway.This will always start your flight direct from runway.
• Initially dont start flying Boeing 737, start with cessna sky hawk
• In a period of two days or a week you can start flying one by one and try to coupe up with Flying lessons and fly the same category of aircraft as you proceed

Will post more about other games soon.......

Books

"Aeronautical engineering is the branch of engineering dealing with the design and development of flight vehicles. Regarded as the most complicated of all technical domains it not only enjoys by giving life to metal structures and soaring them to sky but also needs utmost care to make its survival throughout. The reason for the need of high professionalism, discipline and knowledge is that unlike any other vehicle failure aircraft's failure is the most fatal one. Even a small rivet failure during flight can cause death of hundreds. The more you start to know thing in this field the more you find things that you haven't came across. -Nirmal"

The zeal and thirst of sharing knowledge gave birth to the FAE.As an part of FAE this blog is dedicated to provide you exciting facts and news relating to aeronautical stream that will make you interested and eager to know more thing.....
                                                                                                                      -FAE