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Old 20th July 2013, 09:54   #91
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Default Re: Airbus A320 Long-Term, 3 Million KMs Review

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Originally Posted by vivekiny2k View Post
which wheel?

(is powered?)
More OT.

Good question. Answer = Right wheel. To make it turn towards the kerb by default.

Fordday.
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Old 20th July 2013, 10:01   #92
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Originally Posted by Jeroen View Post
Not entirely true; on any multi engine plane, if you lose an engine, the pilot needs to deal immediately with asymmetric thrust. Going from two engines to one, or from four to three for instance, means not only less power but also asymmetric trust.

You counter it by applying opposite rudder and sometimes, depending on various factor aileron. That by itself introduces additional drag making the lack of power even more pronounced.

Jeroen
Exactly what I said, just in simple terms. The three controls are there to look after the asymmetric thrust and could be handled manually or with the onboard computers in new generation pessenger aircrafts which are programed for assisting pilots in such conditions.

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Old 20th July 2013, 13:50   #93
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Not directly related, but I thought people reading this thread would appreciate this video:

cya
R

That is one sweetest landing I've ever seen !!. Can't forget some other landing videos with lots of tire smoke and stuff. Thanks for sharing the video.
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Old 20th July 2013, 17:52   #94
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That is one sweetest landing I've ever seen !!. Can't forget some other landing videos with lots of tire smoke and stuff. Thanks for sharing the video.
Lot of people qualify this landing as ultra smooth or sweet etc. I wonder what the real (commercial) pilots think of it. Personally I don't think it is a very good landing or safe landing at all. It will have felt very smooth for the passengers admittedly.

This guy is floating his plane along the runway, whether its because he came into fast and is now riding out the ground effect, or whether he's doing it intentionally I can't tell from the video. Either way, he is eating up runway length very fast. You want to touch down at predefined points on the runway, basically pretty early once you come in over the threshold. That gives you the longest runway length to decelerate. If you leave the touch down point to late you simply have less runway length left, you need to brake harder and what if all of sudden your brakes fail or the reverse thruster don't work. Things will start going wrong very quickly, all because you did not put down early enough.

Planes are not at their safest in this flight mode which is sort of half in between flying and rolling on their gear. That's why you need to touch down distinctively, pop the spoilers, dump lift and start (auto) braking and or reverse thrust. This guy puts the plane down very slowly (smooth), but all that time he is in a bit of a grey area, you don't want to be there. You want to go from flight mode into landing rolling mode quickly without to big a bump, but planes are designed to withstand these landing bumps with no problem.

Proper touch down point gives you additional safety margin in terms of runway length. This guys throws all of that out of the window.

Not sure what it does to his tires. I seem to recall a study from a number of years back. (American Airlines??). Anyway, they found that these very smooth landings actually put more wear and tear on the tires then a good, not to firm touchdown! Somebody asked earlier if the wheels could not be spun up prior to landing. That's been researched by various manufacturers quite often. But they all came to same conclusion. The machinery and equipment that is required to spin up the wheels comes at additional weight. Lugging that additional weight around during the life time of a plane cost more in fuel, than replacing the tires often.

There is another problem with the way this guy lands. As long as he is actually flying and hasn't touched down firmly and hasn't popped his spoiler his plane is still developing lift and thus wake turbulence, all along the runway, right up to the moment he does land and pops his spoilers. That means, especially for smaller planes, e.g. me, I have to wait longer before I can land on this same runway, or take my changes. Proper wake turbulence avoidance procedure dictates I need to land past this guys touch down point. And he eats up all the runway.

So, yes, very smooth landing for the passenger. Not particularly safe or smart or considerate for fellow pilots behind him. And probably hard wearing on the tires too.

Since we have a commercial pilot on the forum, I would really like to hear what he thinks?

Jeroen
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Old 20th July 2013, 19:30   #95
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Default Re: Airbus A320 Long-Term, 3 Million KMs Review

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Originally Posted by Jeroen View Post
So, yes, very smooth landing for the passenger. Not particularly safe or smart or considerate for fellow pilots behind him. And probably hard wearing on the tires too.

Since we have a commercial pilot on the forum, I would really like to hear what he thinks?

Jeroen
Agree!

I once had a very similar landing at Delhi from a 777-200, the other passengers were all praises (including an ex-KF pilot/flight instructor) for the perfectly smooth landing, and I was furious, because as a frequent flier, that idiot of a pilot had actually put full wheels down almost a couple of hundred meters past the regular zone. Except most people just don't get it :(

And like you pilots say, air above and runway behind the plane is of no use to a pilot - I believe it myself

Last edited by phamilyman : 20th July 2013 at 19:32.
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Old 20th July 2013, 19:58   #96
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Default Re: Airbus A320 Long-Term, 3 Million KMs Review

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Originally Posted by Jeroen View Post

This guy is floating his plane along the runway, whether its because he came into fast and is now riding out the ground effect, or whether he's doing it intentionally I can't tell from the video. Either way, he is eating up runway length very fast. You want to touch down at predefined points on the runway, basically pretty early once you come in over the threshold. That gives you the longest runway length to decelerate. If you leave the touch down point to late you simply have less runway length left, you need to brake harder and what if all of sudden your brakes fail or the reverse thruster don't work. Things will start going wrong very quickly, all because you did not put down early enough.

...

Jeroen
Agree with you! My bad I couldn't imagine many of those factors like tire wear n tear and especially the stability issues in staying longer in the air etc. It was just a layman's opinion.
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Old 21st July 2013, 09:51   #97
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Default Re: Airbus A320 Long-Term, 3 Million KMs Review

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Originally Posted by Jeroen View Post
Lot of people qualify this landing as ultra smooth or sweet etc. I wonder what the real (commercial) pilots think of it. Personally I don't think it is a very good landing or safe landing at all. It will have felt very smooth for the passengers admittedly.
Well said Jeroen. I also think the landing was smooth but imperfect in the ways you mentioned. In addition to those facts, I believe the final breaking would have been admittedly jerky and sudden as the pilot will have to apply breaks with some more force to bring the plane to a turning stop in shorter length of the runway.
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Old 21st July 2013, 11:38   #98
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@Jeroen Thumbs up !

You have nicely explained the video. It was not very clear so I couldn't see how much runway length he has eaten up by floating the aircraft over it. Then you have also mentioned the over usage of brakes required thereafter. Thats great understanding.

No doubt passengers and cabin crew do appreciate these kind of landings but these are not the safest landings. Most of us would still remember the Air India Express crash at Manglore Airport a couple of years ago. There the pilot was not trying to do a smooth landing by floating over the runway to arrest rate of descend at touchdown. Infact he was high on approach and his touchdown was way beyond the touchdown zone.

What I am trying to say here is that runway left to stop in both the cases is way less than normally it would be. And when luck runs away, an icident or accident is impending.

Coming back to this video this particularly Gentleman who is flying the aircraft is holding the nose up for an extended period of time after landing, which increases the chances of a tail strike. What is a tail strike? Please search 'tailstrike on landing' on youtube and you would find the answer.

To give you all an example, a B777 crash at SFO a few days back, the severance of the crash would have been much lesser if the tail strike would not have happened when they landed short of runway due to underspeed.
Exact findings would be public very soon once NTSB completes the investigation.

A perfect touchdown is the one where we land at 1000 feet marker. Thats the area which is 1000 feet down the runway from start of the runway.

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Old 21st July 2013, 19:53   #99
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Default Re: Airbus A320 Long-Term, 3 Million KMs Review

What a superb thread. Kudos to the OP and thanks so much. Most of us guys have dreamt of being pilots at some point or other in our younger days.

As a 4 year old boy I though I could knock planes out of the sky with a big stick and once they were on the ground play with them. I thought of being a fighter pilot but was dissuaded from joining as I'd have been the 4th generation from my family in the defence services!

And kudos to Jeroen for hitting the nail on the head with his comments on that visibly "ultra smooth landing" which lacks the correct technique and does not adhere to landing guidelines.
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Old 21st July 2013, 20:51   #100
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Default Re: Airbus A320 Long-Term, 3 Million KMs Review

You sir have a great job, i always wanted to be a pilot myself, ended up being a doctor. Anyways 2 very small and idiotic questions.I always wanted to ask this to a pilot but her goes.
1) Like in cars we have keys for ignition, do you have something similar on your aircraft or it just comes alive with flip of a switch?
2)The Yoke which controls the Pitch and Roll, does it also control the aircraft to turn the wheels when it is taxiing? What happens to the wheels when its in air and the landing gear is pulled up?
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Old 21st July 2013, 21:17   #101
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Thanks i'fly for starting a wonderful thread

Regulations say the touchdown should happen in the touchdown zone.Touchdown zone is the first 3000 feet or first 3rd of runway whichever is first! If you look at the video carefully you'll see that the main gear touched within the touchdown zone. So by definition the landing is correct. Thereafter the Pilot held the nose up, which though is not a correct technique, but is used by many, for aerodynamic braking, so as to avoid usage of full reversers, thereby increasing the life of the engines. Landings have to be positive, smoothness factor depends on the pilot expertise, but not at the cost of safety!
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Old 21st July 2013, 21:46   #102
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Default Re: Airbus A320 Long-Term, 3 Million KMs Review

What a fantastic thread! Kudos to ifly for sharing this with us.

I have one noob query - before take off I have seen ground-staff attaching a long hose from a generator sized equipment to the engine.

What's for that?

I can make two guesses only - one to cool down the engine and second to remove any foreign objects which may have entered engine?
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Old 21st July 2013, 22:17   #103
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Quote:
Originally Posted by DocRock View Post
You sir have a great job, i always wanted to be a pilot myself, ended up being a doctor. Anyways 2 very small and idiotic questions.I always wanted to ask this to a pilot but her goes.
1) Like in cars we have keys for ignition, do you have something similar on your aircraft or it just comes alive with flip of a switch?
2)The Yoke which controls the Pitch and Roll, does it also control the aircraft to turn the wheels when it is taxiing? What happens to the wheels when its in air and the landing gear is pulled up?
1) keys
It all depends: On small planes, like Cessna's, Cirrus, Diamonds you do actually have a key, just like in a car. The key works exactly as in your car, it engages the starter and starts the engine. The bigger the planes get, you typically don't have a key. On a 747 for instance you have to throw a switch. Well actually, there's a whole bunch of switches and you have to do it in the correct sequence before anything happens.

2) controlling the wheels
Again it really depends on the plane. but the yoke never controls the wheels.On some small planes like for instance the Cessna 150 the rudder pedals also control the nose wheel. So you steer the plane with the rudder pedals. On other planes, e.g. the Cirrus, the nose wheel essentially castors. You control the steering by means of the rudder pedals which also controls the brake on your left and right main gear. So you steer the plane by differential braking. Takes a bit of getting used to.

On larger plane you tend to have a steering yoke/handle. Ie. a special yoke that directly controls the nose wheel.

When you pull up the wheels, providing you fly a plane with retractable gear, the wheels just spin. Even when retracted the wheels still spin, but of course, eventually they will stop spinning all together.

Jeroen

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Originally Posted by airforce1 View Post
Thereafter the Pilot held the nose up, which though is not a correct technique, but is used by many, for aerodynamic braking, so as to avoid usage of full reversers, thereby increasing the life of the engines. Landings have to be positive, smoothness factor depends on the pilot expertise, but not at the cost of safety!
Sorry, but I dont think that's entirely correct. I don't think reverse thrust does not affect the life of engines by any relevant margin. Number of hours and number of starts determine the life of turbine engines. They don't count the number of reverse thrusts, the do count the number of hours and the number of starts.

Although I'm not that familiar with the airbus as far as know SOP is to use the auto braking system at all times. By aerodynamic braking he might think he's increasing the life of the brakes perhaps. Again, I'm not so sure. The airbus uses carbon brakes and the best you can do for those is to build up heat very fast indeed!

I seem to recall that the Airbus does have some system logic built in that prevents the auto brakes to come in to the preset settings until the nose gear is on the ground and the strut has been compressed. Again, another reason not to land like this. At what time does you auto brake system kicks in?? Anybodies guess.

You land single engine prop planes like this, you keep the nose of the ground as long as can, to avoid prop strike. The only plane I know that gets landed with an intentional nose up attitude for aerodynamic braking effect is the Vulcan. One of my very favorite planes. Probably something to do with a V-wing, the fact that it was British designed and made and probably had pretty crappy brakes to start with. They did not have carbon brakes in those days

Jeroen

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Last edited by .anshuman : 23rd July 2013 at 10:51. Reason: See note in post. Thanks
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Old 21st July 2013, 23:55   #104
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Lots of noob questions. Here is one from me. Are the wheels powered / driven only for taxing? When accelerating for takeoff, does the wheels spin freely and the aircraft propelled purely by thrust of the tubine engines?

OT: all this while I thought this thread is in the Review section. I started looking for the Thanks button today. Thanks iFly for starting this thread, and Jeroen for providing so much technical insight.
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Old 22nd July 2013, 00:01   #105
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Lots of noob questions. Here is one from me. Are the wheels powered / driven only for taxing? When accelerating for takeoff, does the wheels spin freely and the aircraft propelled purely by thrust of the tubine ..
Wheels are not powered even for taxiing. Its the thrust from the engines which makes the wheels start moving. And yes as you said, 'When accelerating for takeoff, the wheels spin freely and the aircraft propelled purely by thrust of the engines'.
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