Transport Aircraft for IAF

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Pratyush
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Re: Transport Aircraft for IAF

Postby Pratyush » 08 Dec 2010 09:33

Giles,

Dont aircrafts carry a Small Ram air power turbines to deal with such contingency. So as long as fwd momentum is maintaines the aircraft will have power to control it self.

IIRC there was a case of a Canadian Boeing 767 which ran out of fuel in flight losing all electrical power. The turbine was deployed and the pilots were able to control the aircraft.

JMT

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Re: Transport Aircraft for IAF

Postby neerajb » 08 Dec 2010 09:57

^^^^

You are talking about Gimli glider, air transat flight 236 also encountered the same problem albeit the cause was fuel leak. More than electrical power, which incase of emergency is provided by batteries/hydraulic driven generator (HDG), one needs hydraulic power to steer the aircraft. Ram air turbine provides hydraulic and/or electrical power to the aircraft. In case of B 767, the RAT provides limited hydraulic power for flight controls and HDG.

Cheers....
Last edited by neerajb on 08 Dec 2010 09:58, edited 1 time in total.

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Re: Transport Aircraft for IAF

Postby Austin » 08 Dec 2010 09:58

Gilles wrote:FWB requires electricity. If all you have is FWB, no matter how many systems, if you lose all electrical power, you lose control of the aircraft. Airbus aircraft have FWB redundancy but the rudder and horizontal stabilizer trim are mechanical/hydraulic, which allow the pilot to maintain control of his aircraft should he lose all FWB computers (can really only be caused by losing all electrical power)


Gilles AFAIK all the modern Airbus and Boeing have full quad digital FBW with no mechanical backup , only older aircraft had a mix of both , thats probably because the technology was not mature or they did not want to keep full faith in full FBW , a mechnical backup also added weight to the aircraft and perhaps added complexity , weight is always an issue for any aircraft.

I can think of an aircraft loosing full electric power for couple of reasons , catastrophic all engine failure which would means they may have to rely on limited APU to power critical system or even that could be unavailable , a badly designed power system with no redundancy which will lead to complete failure a rarity these days , a shot-circuit or fire on board electrical system.

MTA has digital FWB with mechanical backup does this mean that mechanical backup is fully independent of FBW and in case of complete failure of FBW the mechanical backup can still fly the aircraft with all control surfaces accessible and functional ?

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Re: Transport Aircraft for IAF

Postby Gilles » 09 Dec 2010 04:17

Wikileaks informs us that the US Government did not approve the sale and installation of high end LAIRCM missile defence systems on Qatari C-17s.

http://www.wikileaks.ch/cable/2009/08/09DOHA502.html

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Re: Transport Aircraft for IAF

Postby Gilles » 09 Dec 2010 04:21

Pratyush wrote:Giles,

Dont aircrafts carry a Small Ram air power turbines to deal with such contingency. So as long as fwd momentum is maintaines the aircraft will have power to control it self.

IIRC there was a case of a Canadian Boeing 767 which ran out of fuel in flight losing all electrical power. The turbine was deployed and the pilots were able to control the aircraft.

JMT


The RAT (Ram Air Turbine) is generally a small hydraulic pump that maintains pressure on one of the hydraulic systems. In a FBW aircraft with no mechanical/hydraulic backup, if you loose all electrical power, you loose control, even your hydraulics system is intact and in full working order because is takes electricity to send the pilots control inputs to the hydraulic actuators.

The 767 is an aircraft with conventional hydraulic controls. Air Transat's dead stick landing in Portugal was with a FWB A-330 but the aircraft still had battery power and a hydraulically operated generator (The RAT provided Hydraulic pressure to the Green system which is fitted with a small hydraulically powered generator)

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Re: Transport Aircraft for IAF

Postby Gilles » 09 Dec 2010 04:34

Austin wrote:
Gilles AFAIK all the modern Airbus and Boeing have full quad digital FBW with no mechanical backup , only older aircraft had a mix of both , thats probably because the technology was not mature or they did not want to keep full faith in full FBW , a mechnical backup also added weight to the aircraft and perhaps added complexity , weight is always an issue for any aircraft.


Austin, that is both correct and wrong.

Where you are wrong is that the Airbus FBW aircraft do have mechanical/hydraulic rudder as well as a mechanical/hydraulic horizontal stabilizer that allows to control the aircraft in case of full electrical failure (They call it Mechanical backup)

Where you are correct, is that this backup system is only meant for temporary control of the aircraft in the air and while electrical power is being restored. It is not meant to allow landing of the aircraft. In the simulator, I heard that some pilots who tried it successfully landed the aircraft under Mechanical Backup, but that most who attempt it crash it.
Last edited by Gilles on 09 Dec 2010 05:29, edited 1 time in total.

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Re: Transport Aircraft for IAF

Postby Gaur » 09 Dec 2010 04:44

Air Force C-17s deliver Abrams tanks to Afghanistan

Image

U.S. Air Force C-17 Globemaster III aircraft crew assigned to the 816th Expeditionary Airlift Squadron loads a Marine Corps M1A1 Abrams tank for aerial transport to Afghanistan in support of Operation Enduring Freedom Nov. 28, 2010. The 816th EAS was deployed to an undisclosed location in Southwest Asia. (U.S. Air Force photo by Staff Sgt. Andy M. Kin)

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Re: Transport Aircraft for IAF

Postby Gilles » 09 Dec 2010 05:03

Gaur wrote: The 816th EAS was deployed to an undisclosed location in Southwest Asia


They airlifted it to Afghanistan from
an undisclosed location in Southwest Asia
after a boat trip.

Probably from Karachi. Sending the tanks over land would have exposed them to the embarrassment of worldwide front page pictures of 20 Taliban militia taking a joy ride on top of an M-1 Abrams in the Tribal Areas....... Something like this picture but with an M-1 Abrams instead of a Humvee

Image

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Re: Transport Aircraft for IAF

Postby Singha » 09 Dec 2010 08:36

well atleast it is just like a mcdonalds drive through, looking at the space on the side after tank enters. bodes well for Arjuns in aksai chin !! (Ahuja sir might be pleased to see this pic)

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Re: Transport Aircraft for IAF

Postby neerajb » 09 Dec 2010 12:10

Gilles wrote:Where you are correct, is that this backup system is only meant for temporary control of the aircraft in the air and while electrical power is being restored. It is not meant to allow landing of the aircraft. In the simulator, I heard that some pilots who tried it successfully landed the aircraft under Mechanical Backup, but that most who attempt it crash it.


Isn't it called as 'Alternate Law' in Airbus lingo. Essentially it is a simpler FBW channel with reduced automation, available in case of emergencies but still it is not mechanical. Quantas flight QF32 was recovered with 'Alternate Law' at Singapore.

Cheers....

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Re: Transport Aircraft for IAF

Postby Gilles » 09 Dec 2010 15:19

neerajb wrote:['Alternate Law' i


Airbus Flight Control:

In Normal Configuration = Normal Law
With some computer Losses = Alternate Law 1
With More computer losses Alternate Law 2
With Minimal electrical power and more computer losses = Direct Law
With No electricl power or with loss of all computers = Mechanical Backup

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Re: Transport Aircraft for IAF

Postby neerajb » 10 Dec 2010 10:29

Thanks Gilles. Searched on Google and found this. Rudder for roll/yaw control and pitch by horizontal stabalizer trim :eek:

If someone could land an aircraft with such limitations, he/she must be one hell of a pilot.

Cheers....

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Re: Transport Aircraft for IAF

Postby Singha » 10 Dec 2010 10:34

is real direct law and mechanical backup landing part of the training curriculum of military transport pilots or civilian airline pilots ?

or is it restricted to simulator training only?

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Re: Transport Aircraft for IAF

Postby Austin » 10 Dec 2010 10:39

Gilles wrote:Where you are wrong is that the Airbus FBW aircraft do have mechanical/hydraulic rudder as well as a mechanical/hydraulic horizontal stabilizer that allows to control the aircraft in case of full electrical failure (They call it Mechanical backup)


Thanks for the info , I am assuming Boeing does not have a mechanical backup like Airbus does , any reason for different approaches between the two ?

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Re: Transport Aircraft for IAF

Postby Gilles » 11 Dec 2010 00:08

Austin wrote:
Gilles wrote:Where you are wrong is that the Airbus FBW aircraft do have mechanical/hydraulic rudder as well as a mechanical/hydraulic horizontal stabilizer that allows to control the aircraft in case of full electrical failure (They call it Mechanical backup)


Thanks for the info , I am assuming Boeing does not have a mechanical backup like Airbus does , any reason for different approaches between the two ?


I am not very familiar with the flight control modes of FBW Boeing transports, which are the B-777 and the C-17. Perhaps someone else could pitch in?

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Re: Transport Aircraft for IAF

Postby shukla » 11 Dec 2010 16:10

Report faults pilot for deadly Alaska C-17 crash
Washington Post

A pilot's overly aggressive maneuvering and overconfidence were blamed in an investigative report on a C-17 plane crash at an Anchorage military base that killed all four airmen on board. Besides pilot error, the crew on board was also faulted for failing to notice the dangerous situation that culminated with the plane stalling and crashing into some woods


Military report cites aggressive acrobatics in C-17 crash
Los Angeles Times

"The mishap pilot violated regulatory provisions and multiple flight manual procedures, placing the aircraft outside established flight parameters at an attitude and altitude where recovery was not possible," the report's executive summary says.

When the stall warning sounded, the co-pilot responded by saying "temperature, altitude lookin' good," according to the report.

"Although the pilot eventually attempted to recover the aircraft, he employed incorrect procedures, and there was not sufficient altitude to regain controlled flight," the report says.

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Re: Transport Aircraft for IAF

Postby Austin » 12 Dec 2010 08:41

Aviadvigatel offers re-engining planes with PS-90A2

As previously reported, December 29, 2009 Aviation Register of Interstate Aviation Committee gave the developer the type certificate number ST309-AMD in the engine PS-90A2. From previous versions (PS-90A,-90A1, and 90-76), it differs in a number of upgraded parts and systems, thus improving its performance and substantially - by 37% - reducing life cycle costs.


PS-90A2

Should be part of our IL-76 upgrade and new IL-76 buy for awacs

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Re: Transport Aircraft for IAF

Postby Shalav » 12 Dec 2010 08:52

neerajb wrote:Rudder for roll/yaw control and pitch by horizontal stabalizer trim

If someone could land an aircraft with such limitations, he/she must be one hell of a pilot.


1. The rudder does not influence roll.
2. Mechanically induced yaw and pitch is controlled on thousands of aircraft everyday using the rudder and stabilizer.

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Re: Transport Aircraft for IAF

Postby nachiket » 12 Dec 2010 09:04

Shalav wrote:
neerajb wrote:Rudder for roll/yaw control and pitch by horizontal stabalizer trim

If someone could land an aircraft with such limitations, he/she must be one hell of a pilot.


1. The rudder does not influence roll.

You are wrong there.

Check this

Using the rudder causes one wing to move forward faster than the other. Increased speed means increased lift, and hence rudder use causes a roll effect. Also, since rudders generally extend above the aircraft's center of gravity, a torque is imparted to the aircraft resulting in an adverse bank. Pushing the rudder to the right not only pulls the tail to the left and the nose to the right, but it also "spins" the aircraft as if a left turn were going to be made. Out of all the control inputs, rudder input creates the greatest amount of adverse effect. For this reason ailerons and rudder are generally used together on light aircraft: when turning to the left, the control column is moved left, and adequate left rudder is applied.

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Re: Transport Aircraft for IAF

Postby Shalav » 12 Dec 2010 09:24

Well you are quoting wikipedia as a reference!!

Applying a left or right aileron induces a nose down attitude during the turn which is why one uses the rudder to maintain a level turn instead of loosing altitude on a turn using only ailerons. Your wikipedia quote fails to mention a level turn is the reason why ailerons and rudder are used simultaneously in a turn.

Given its failure to mention the most obvious use of rudder and aileron together for a coordinated turn - I'll ignore wikipedia as being valid reference; thank you very much!

Instead it mentions use of the elevator to "increase the AoA" so as to maintain level flight.

To maintain level flight requires increased positive (up) elevator to increase the angle of attack, increase the total lift generated and keep the vertical component of lift equal with the weight of the aircraft.

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Re: Transport Aircraft for IAF

Postby Indranil » 12 Dec 2010 12:53

Shalav you are right. But the whatever Wikipedia is saying is not wrong. You both are speaking of different flight control measures.

If you would build a plane with only rudder and elevator, you would notice that the plane banks when you turn it. In fact if you maintain the same speed and keep the rudder at same deviation, your plane won't make circles. It would bank and keep banking further and further. Depends on the the planes CG, but in most cases it will nose dive eventually (for the same reason you quoted when a plane banks, its pitch goes does) It is very simple physics, just like the differentials on a truck.

But you are right it wouldn't just role, it will start turning. So it will be incredibly difficult to control a big/heavy plane with just elevator trims and rudder .

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Re: Transport Aircraft for IAF

Postby nachiket » 12 Dec 2010 12:57

I was specifically talking about Shalav's confident statement that the "Rudder does not influence Roll". That is just plain wrong. I said nothing about using only the rudder to turn the aircraft. That will not work. But the Rudder does cause a secondary banking effect.

In fact a problem with the B737 rudder caused several incidents and three crashes in the 90's. The dual servo valve inside the PCU controlling the rudder would jam under certain conditions and the rudder would either be stuck in a particular position or be actually deflected in the opposite direction to the Pilot's input. The result would be that the aircraft would suddenly roll hard in one direction and cause a near complete loss of control since the ailerons weren't powerful enough to counteract the rolling force.

Anyways this is getting way OT. So I will withdraw before the admins come at me.

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Re: Transport Aircraft for IAF

Postby Indranil » 12 Dec 2010 23:06

nachiket wrote:I was specifically talking about Shalav's confident statement that the "Rudder does not influence Roll". That is just plain wrong.
<SNIP>
Anyways this is getting way OT. So I will withdraw before the admins come at me.

Agreed and agreed :).

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Re: Transport Aircraft for IAF

Postby Katare » 13 Dec 2010 04:28

Gilles wrote:
Gaur wrote: The 816th EAS was deployed to an undisclosed location in Southwest Asia


They airlifted it to Afghanistan from
an undisclosed location in Southwest Asia
after a boat trip.

Probably from Karachi. Sending the tanks over land would have exposed them to the embarrassment of worldwide front page pictures of 20 Taliban militia taking a joy ride on top of an M-1 Abrams in the Tribal Areas....... Something like this picture but with an M-1 Abrams instead of a Humvee

Image


:rotfl:

Gilles, give it up man! It's over!

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Re: Transport Aircraft for IAF

Postby Raman » 13 Dec 2010 08:06

Applying a left or right aileron induces a nose down attitude during the turn which is why one uses the rudder to maintain a level turn instead of loosing altitude on a turn using only ailerons.


This is incorrect --- the nose doesn't drop. Using ailerons causes one wing to develop more lift than the other, causing the bank. However, the lift differential also causes differential in induced drag --- the "high" wing develops more induced drag than the "low" wing. This causes the adverse yaw --- the nose rises a little and yaws towards the high wing, which is away from the direction of the turn, resulting in the aircraft skidding through the turn. The skid causes an unpleasant sensation and is inefficient because the side the fuselage is subjected to the airflow, causing a huge drag increment. As you pointed out, the rudder is applied to counteract this adverse yaw.

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Re: Transport Aircraft for IAF

Postby neerajb » 13 Dec 2010 14:10

Shalav wrote:
neerajb wrote:Rudder for roll/yaw control and pitch by horizontal stabalizer trim

If someone could land an aircraft with such limitations, he/she must be one hell of a pilot.


1. The rudder does not influence roll.
2. Mechanically induced yaw and pitch is controlled on thousands of aircraft everyday using the rudder and stabilizer.


The rudder does influences a roll, infact yaw always results in a rolling moment. If not, then how do you explain the rudder and aileron input during a crab?

In commercial planes the rudder is used for yaw/turning during landing/takeoff or at low airspeeds. At low altitudes it is not safe to bank an aircraft to align it with runway, So rudder is used. At cruise ailerons are used and there are many other schemes (mechanical/electronic) available to offset the adverse yaw so the pilots are not bothered about the coordinated turn.

Cheers....

Added later : I never said pitch control by elevator but by the trim tabs.
Last edited by neerajb on 13 Dec 2010 16:18, edited 1 time in total.

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Re: Transport Aircraft for IAF

Postby Lalmohan » 13 Dec 2010 14:18

six degrees of freedom
3 force directions
3 moments
first derivative cross effects
second derivative cross effects
everything has a bearing on everything else
welcome to flight mechanics!

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Re: Transport Aircraft for IAF

Postby shiv » 13 Dec 2010 17:26

Raman wrote:
Applying a left or right aileron induces a nose down attitude during the turn which is why one uses the rudder to maintain a level turn instead of loosing altitude on a turn using only ailerons.


This is incorrect --- the nose doesn't drop. Using ailerons causes one wing to develop more lift than the other, causing the bank. However, the lift differential also causes differential in induced drag --- the "high" wing develops more induced drag than the "low" wing. This causes the adverse yaw --- the nose rises a little and yaws towards the high wing, which is away from the direction of the turn, resulting in the aircraft skidding through the turn. The skid causes an unpleasant sensation and is inefficient because the side the fuselage is subjected to the airflow, causing a huge drag increment. As you pointed out, the rudder is applied to counteract this adverse yaw.


Not questioning your evident awareness of the subject (more than me anyways). If the aileron deflection that initiates a roll is not corrected soon the plane will keep on rolling, so aren't the ailerons brought back to neutral when the required angle of bank is achieved for a turn(typically in less than a second in a fighter)? But at this stage in a bank the "lift" in the "upward direction" (away from center of earth) is reduced. Therefore the plane "sideslips" and will necessarily lose altitude. However in a bank, the tailplane (now partially horizontal) produces some lift and does this not tend to produce a yaw turning nose towards the ground that can be somewhat remedied by applying rudder deflection to the direction opposite the bank - i.e left bank requires right rudder deflection to reduce the yaw?

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Re: Transport Aircraft for IAF

Postby Shalav » 19 Dec 2010 06:02

Neeraj,

The original statement was "using ruder to control yaw/roll". That statement is incorrect. While the rudder may cause an uncontrolled or unforeseen roll it is not used to control the roll, the ailerons are! That is the misstatement I am correcting. An unforeseen consequence of a sequence of control inputs DOES NOT MEAN they can ALWAYS occur, and the relevant control surface can induce or correct it EVERYTIME.


Nachiket,

I checked the NTSB database, they report only concludes loss of control due to rudder issues. I cannot see anything in their database which states the rudder issue caused a roll. The NTSB is very precise about its reports. If during the investigation they had any cause to suspect loss of rudder control caused a roll they would have mentioned it. Since there is no such conclusion, their reports DO NOT support your hypothesis.

NTSB conclusion of the accidents are below

US Air 427
The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
A loss of control of the airplane resulting from the movement of the rudder surface to its blowdown limit. The rudder surface most likely deflected in a direction opposite to that commanded by the pilots as a result of a jam of the main rudder power control unit servo valve secondary slide to the servo valve housing offset from its neutral position and overtravel of the primary slide.


United Airlines 585
The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
A loss of control of the airplane resulting from the movement of the rudder surface to its blowdown limit. The rudder surface most likely deflected in a direction opposite to that commanded by the pilots as a result of a jam of the main rudder power control unit servo valve secondary slide to the servo valve housing offset from its neutral position and overtravel of the primary slide.



Shiv,

Ailerons are deflected throughout the roll, and when they are returned to normal the aircraft levels off. Ailerons work by increasing or decreasing lift as needed to induce the roll, and the right and left ailerons work in tandem deflecting in opposite directions.

To make a left turn, you turn the yoke to the left and the left aileron deflects up while the right aileron deflects down. This creates greater lift in the right wing which lifts it up and greater drag on the left wing which dips it down. When the desired bank angle is reached the pilot maintains the yoke position - thus maintaining the aileron deflection and roll.

When the turn is completed, the yoke is moved to the neutral position the ailerons move back into their normal position, and at this time the asymmetrical lift on the wings is discarded and the wings will automatically level off as the lift forces acting on the wings equalize. So to answer your question - the ailerons will be deflected for the duration of the turn.

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Re: Transport Aircraft for IAF

Postby srai » 19 Dec 2010 07:33

indranilroy wrote:
Austin wrote:Any reason why IAF would replace 100 odd fleet of An-32 that can carry 6T to ~2500 km with 45 odd MTA that can carry 20T at the same range ?

So fewer aircraft with better payload and better maintenance/uptimes are better then larger fleet of small aircraft ?


Some will be taken up by the C-27 I guess.

This is a very good reason to get the RTA (military) version to come up ASAP.


There was also a report a while back of IAF planning an option for 40 MTA on top of the firm 45 MTA order. Plus, add to this the 12 C-130J (6 + 6 options).

It looks like IAF is replacing its 100+ An-32 (and 60+ HS-748) fleet with multiple aircraft types.
  • 6-12 C-130J - (6 + 6 options)
  • 45-80 MTA - (45 + 40 options)
  • 12-24 C-27 - (tender out)
  • 40-60 RTA - (probably replace the HS-748)
Last edited by srai on 19 Dec 2010 07:46, edited 1 time in total.

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Re: Transport Aircraft for IAF

Postby Singha » 19 Dec 2010 07:44

all the AN-32 are in process of upg in Ukraine. I think they will serve a decade more. the HS-748 needs to go away though...maybe C27? we should obtain more C130 - 25?

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Re: Transport Aircraft for IAF

Postby shiv » 19 Dec 2010 09:03

Shalav wrote:Ailerons are deflected throughout the roll, and when they are returned to normal the aircraft levels off. Ailerons work by increasing or decreasing lift as needed to induce the roll, and the right and left ailerons work in tandem deflecting in opposite directions.

To make a left turn, you turn the yoke to the left and the left aileron deflects up while the right aileron deflects down. This creates greater lift in the right wing which lifts it up and greater drag on the left wing which dips it down. When the desired bank angle is reached the pilot maintains the yoke position - thus maintaining the aileron deflection and roll.

When the turn is completed, the yoke is moved to the neutral position the ailerons move back into their normal position, and at this time the asymmetrical lift on the wings is discarded and the wings will automatically level off as the lift forces acting on the wings equalize. So to answer your question - the ailerons will be deflected for the duration of the turn.


You sound like you actually fly an aircraft - I am sure you must be right although it does not sound right to me.

If one aileron is up and the other one down what stops the aircraft from rolling through 360 degrees and more as long as the ailerons are deflected? Why should an aircraft merely bank to a particular angle and then hold steady if the aileron deflection is maintained? The reason I say this is that model aircraft do exactly that. If you maintain aileron deflection they keep on rolling and move forward looking like a corkscrew or a bullet from a rifled gun.

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Re: Transport Aircraft for IAF

Postby andy B » 19 Dec 2010 10:00

shiv wrote:
Shalav wrote:Ailerons are deflected throughout the roll, and when they are returned to normal the aircraft levels off. Ailerons work by increasing or decreasing lift as needed to induce the roll, and the right and left ailerons work in tandem deflecting in opposite directions.

To make a left turn, you turn the yoke to the left and the left aileron deflects up while the right aileron deflects down. This creates greater lift in the right wing which lifts it up and greater drag on the left wing which dips it down. When the desired bank angle is reached the pilot maintains the yoke position - thus maintaining the aileron deflection and roll.

When the turn is completed, the yoke is moved to the neutral position the ailerons move back into their normal position, and at this time the asymmetrical lift on the wings is discarded and the wings will automatically level off as the lift forces acting on the wings equalize. So to answer your question - the ailerons will be deflected for the duration of the turn.



You sound like you actually fly an aircraft - I am sure you must be right although it does not sound right to me.

If one aileron is up and the other one down what stops the aircraft from rolling through 360 degrees and more as long as the ailerons are deflected? Why should an aircraft merely bank to a particular angle and then hold steady if the aileron deflection is maintained? The reason I say this is that model aircraft do exactly that. If you maintain aileron deflection they keep on rolling and move forward looking like a corkscrew or a bullet from a rifled gun.


http://www.grc.nasa.gov/WWW/K-12/airplane/alr.html

Ailerons can be used to generate a rolling motion for an aircraft. Ailerons are small hinged sections on the outboard portion of a wing. Ailerons usually work in opposition: as the right aileron is deflected upward, the left is deflected downward, and vice versa. This slide shows what happens when the pilot deflects the right aileron upwards and the left aileron downwards.

The ailerons are used to bank the aircraft; to cause one wing tip to move up and the other wing tip to move down. The banking creates an unbalanced side force component of the large wing lift force which causes the aircraft's flight path to curve. (Airplanes turn because of banking created by the ailerons, not because of a rudder input.

The ailerons work by changing the effective shape of the airfoil of the outer portion of the wing.


Shiv, Shalav two points that I would like to ask please:

- Given that there is movement in alierons on both sides one going up the other going down depending on which direction the plane wants to roll is it always set that one will move up and the other will move down albeit the one moving up will be doing so at a higher extent than the one moving down or vice versa?

- Secondly is it that the plane rolls because of the distinct pressure above and below the wing so even if they move to same extent because of the pressure the plane rolls.

Apologies is questions seem noobish.

Shalav
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Re: Transport Aircraft for IAF

Postby Shalav » 19 Dec 2010 10:28

Shiv,

Take it FWIW. I'm not a pilot or an aeronautics engineer.

shiv
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Re: Transport Aircraft for IAF

Postby shiv » 19 Dec 2010 13:04

OK thanks. I think that as long as ailerons are deflected the plane will keep on rolling. If only a bank and a turn is required, the ailerons are deflected until the degree of bank is achieved and then returned to neutral, only to be reactivated if the plane shows a deviation from the required bank angle. In practice I think that most stable aircraft have a tendency to return to level flight from the position of a slight bank and that will require continued aileron inputs I guess. This is what I have observed in airliners anyway. Will try and locate video clips.

If the plane is rolled to 90 degrees - the plane will go nose down and will need altitude to recover. The famous B-52 airshow crash shows exactly this happening - but it did not have the altitude.
http://www.youtube.com/watch?v=yE3l3mEM9-4

shiv
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Re: Transport Aircraft for IAF

Postby shiv » 19 Dec 2010 13:27

andy B wrote:- Given that there is movement in alierons on both sides one going up the other going down depending on which direction the plane wants to roll is it always set that one will move up and the other will move down albeit the one moving up will be doing so at a higher extent than the one moving down or vice versa?

I am no expert.

One moves up and the other down, yes. Do they move simultaneously? Yes. Do they move equally? I guess so - although the meaning of "equally" is difficult for me to say. I guess if they are plain ailerons of the old type controlled by cables/rods then the amount of cable pull up on one side equals cable pull down on the other side. But if the plane flaperons or elevons that double up as flap or elevator and aileron then the movement may not be "equal"


andy B wrote:- Secondly is it that the plane rolls because of the distinct pressure above and below the wing so even if they move to same extent because of the pressure the plane rolls.

I am guessing that if you ask a person who actually speaks airpl-tongue - the language of aerodynamics - he may tell you things that I can't understand. If you ask me - yes, the pressure over the wing goes up when the aileron on that side is raised and the wing goes down. Vice versa for the other side.

Indranil
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Re: Transport Aircraft for IAF

Postby Indranil » 19 Dec 2010 13:44

Shiv ji you are right. Shalav your explanation of usage of ailerons to turn is not right.

One applies differential lift and banks. Once the required banking is achieved ailerons level off (This is the cause for most of aeromodelling rookie pilot crashes). The plane continues to follow the arc of it's turn. Once the turn is complete, the ailerons are reversed to level the plane. Once the plane is level the ailerons level off.

Also rudder doesn't produce the perfect yaw effect. You will always produce a rolling moment if you add radar in horizontal flight. Albeit the moment is not anywhere close to the amount provided by ailerons. In case of emergency one can produce roll from rudder is need be. Ofcourse one would need a lot of presence of mind and manual-reading to control the flight that way.

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Re: Transport Aircraft for IAF

Postby neerajb » 19 Dec 2010 16:05

Shalav wrote:Neeraj,
The original statement was "using ruder to control yaw/roll". That statement is incorrect. While the rudder may cause an uncontrolled or unforeseen roll it is not used to control the roll, the ailerons are! That is the misstatement I am correcting. An unforeseen consequence of a sequence of control inputs DOES NOT MEAN they can ALWAYS occur, and the relevant control surface can induce or correct it EVERYTIME.


You haven't read my post and are quoting out of context. Everyone knows what ailerons/rudders do so why rehash the obvious. The original discussion was Airbus control laws in general and mechanical backup in particular. Mechanical backup means you have rudder only for yaw/roll control and pitch trim for pitch control. I don't understand what do you want to assert by your above quote?

Cheers....

Philip
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Re: Transport Aircraft for IAF

Postby Philip » 20 Dec 2010 15:50

Report in a recent AWST Delhi report on C-130J acquisitions,quotes AM Sarad Savur (retd.),former commander of SC and a transport pilot, as saying that the numbers are insufficient to carry a special forces batallion and that more are required (16+?).It also says that the air force is looking at Spartan transports as a "filler" between C-130s and AN-32s and a poss. long term replacement for the AN-32s (which are al being upgraded by Ukraine).

The C-27A Spartan is a twin turboprop engine aircraft designed to meet an Air Force requirement for a rugged, medium size airland transport. The Spartan, which looked like a toned-down, twin engine version of the C-130, gave US military troops a unique, short-take-off-and-landing capability, providing access to airstrips otherwise unreachable by fixed-wing aircraft.

The C-27 can carry up to 18,000 pounds of fuel and cargo and can fly farther than cargo helicopters. Much like its big brother, the C-130 Hercules, the C-27 also has the unique ability to land and take-off on extremely small (less than 3,000 feet) undeveloped strips of land. These advantages made the C-27 a key player in delivering food, water and other supplies to remote areas that other airplanes and helicopters can not get to.

The aircraft was particularly suited for short-to-medium range tactical operations into semi-prepared airfields as short as 1,800 feet. The C-27A is an all-weather, day/night transport with capabilities to perform medical evacuation missions. It can carry 24 litters and four medical attendants, or 34 ground troops. The Spartan has a cargo capacity of more than 2,000 cubic feet, or 12,000 pounds. The C-27A operates with a three person crew of aircraft commander, copilot and loadmaster

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Re: Transport Aircraft for IAF

Postby Lalmohan » 20 Dec 2010 16:52

shiv, to add to indranil's comments on roll and ailerons - in normal aircraft - wing dihedral (angle up from the fuselage when looking face on) is used to induce stability, i.e. return it to the neutral position following manoevres. Also, differential ailerons rarely operate symmetrically - the wing aerofoil section is not symmetric and the lift/drag curves are non-linear. the impact of up and down ailerons vary non-linearly

in modern fighter aircraft, there is no real neutral point, i.e. the aircraft cannot return to a stable state since there isn't one - the forces and moments are designed to be out-of-balance. a stable state is maintained by computer direction of control surfaces to maintain an artificial stability

in a civil aircraft, this is a highly undesirable quality


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