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Old 23rd June 2016, 19:56   #211
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Default Re: Boeing 777 - Pilot's Review

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As said in the above paragraph, de-icing is automatic on the 777. But auto de-icing failure happens and has proved to be fatal in many situations. The 777, depending on the gravity of the failure, provides EICAS messages and warning light and beepers. I have attached a list of the warnings/caution messages which occur on de-icing failure.
Hi Buddy! Am a little confused, if de-icing is automatic then why do pilots ask for it at the airports? I have seen a crane spraying de-icing liquid on the wings of an aircraft in sub-zero conditions.
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Old 23rd June 2016, 20:57   #212
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Default Re: Boeing 777 - Pilot's Review

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Hi Buddy! Am a little confused, if de-icing is automatic then why do pilots ask for it at the airports? I have seen a crane spraying de-icing liquid on the wings of an aircraft in sub-zero conditions.
As mentioned earlier, the automatic de-icing system works only when the engines are running. Now the engines are started only after the aircraft has been pushed back or in the process of pushing back. Once we have pushed back from the gate, we cannot waste time getting the wings de-iced using the engine. We barely get enough time to spool up the engine properly, forget de-icing. The best place to get it de-iced is when it's at the gate. Saves a lot of time. Although due to safety reasons, we sometimes use a de-ice pad on the airport.
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Old 25th June 2016, 16:10   #213
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Default Re: Boeing 777 - Pilot's Review

So rearranging luggage and in fact even passengers could be one of the 'technical' reasons a flight gets delayed!
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Old 25th June 2016, 23:54   #214
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So rearranging luggage and in fact even passengers could be one of the 'technical' reasons a flight gets delayed!

Correct and it does happen. Although probably, having to offload luggage for a passenger that did not board happens more frequently
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Old 26th June 2016, 09:40   #215
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Default Re: Boeing 777 - Pilot's Review

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Hi Buddy! Am a little confused, if de-icing is automatic then why do pilots ask for it at the airports? I have seen a crane spraying de-icing liquid on the wings of an aircraft in sub-zero conditions.
There appears to be a confusion between deicing and anti icing. Deicing is clearing the aircraft surface from ice which is already present/formed. Anti icing is using systems to prevent a potential buildup of ice. All aircraft have anti icing systems which use bleed air (bled from engines and is quite hot) to run along channels on the leading edges of wings and turbine blades etc to ensure that ice doesn't build up during operation. Deicing is a procedure carried out at gates or at special areas in the airport where in deicing fluids are sprayed all over the aircraft which melts ice and prevents further buildup during the 'holdover period' a time frame of usually around 40/45 mins which is sufficient for the airplane to get airborne.
In short you deice before startup, then start your anti icing systems on and then takeoff.
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Old 26th June 2016, 10:32   #216
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Default Re: Boeing 777 - Pilot's Review

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Originally Posted by apachelongbow View Post
There appears to be a confusion between deicing and anti icing. Deicing is clearing the aircraft surface from ice which is already present/formed. Anti icing is using systems to prevent a potential buildup of ice. All aircraft have anti icing systems which use bleed air (bled from engines and is quite hot) to run along channels on the leading edges of wings and turbine blades etc to ensure that ice doesn't build up during operation. Deicing is a procedure carried out at gates or at special areas in the airport where in deicing fluids are sprayed all over the aircraft which melts ice and prevents further buildup during the 'holdover period' a time frame of usually around 40/45 mins which is sufficient for the airplane to get airborne.
In short you deice before startup, then start your anti icing systems on and then takeoff.
I am not so sure though, because my manual specifically says that the engine anti-ice systems can also de-ice when required, in air or on ground. Although I have never seen or heard about anyone using their engines to de-ice on the ground. It depends on the operator and the aircraft as well. Here is an excerpt from my manual. Read the 2nd paragraph.
Attached Thumbnails
Boeing 777 - Pilot's Review-pages-777_2_complete.jpg  


Last edited by searchingheaven : 26th June 2016 at 10:40.
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Old 26th June 2016, 12:18   #217
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Default Re: Boeing 777 - Pilot's Review

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Originally Posted by searchingheaven View Post
I am not so sure though, because my manual specifically says that the engine anti-ice systems can also de-ice when required, in air or on ground. Although I have never seen or heard about anyone using their engines to de-ice on the ground. It depends on the operator and the aircraft as well. Here is an excerpt from my manual. Read the 2nd paragraph.
Thanks...it appears the 777 has some provision for de icing as well. In the a320 it's clearly said only anti icing possible and de icing is via gate and detailed in cold wx ops
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Old 26th June 2016, 12:19   #218
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Default Re: Boeing 777 - Pilot's Review

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Originally Posted by apachelongbow View Post
Thanks...it appears the 777 has some provision for de icing as well. In the a320 it's clearly said only anti icing possible and de icing is via gate and detailed in cold wx ops
Yeah, I guess that would depend on the aircraft. Anyway, thanks for the information . Learn something new everyday.
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Old 26th June 2016, 16:46   #219
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Default Re: Boeing 777 - Pilot's Review

OK. now please throw some light on how the jet engines are cooled, what is the type of coolant, engine oil used, quantity etc.!
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Old 27th June 2016, 10:34   #220
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Default Re: Boeing 777 - Pilot's Review

Cgi is not a deal breaker. It can be adjusted to an atomic level in new planes.

Take off
A fully loaded 747 has a take off weight of 360 tons. HALF that weight is fuel. Mostly in the wings. Some planes store a % age of the fuel in the central region below the passengers.

Exam question
300 fat passengers at 100 kg each is 30 tons. That's 7-8% total plane weight. Engines have the capacity to lift a 360 ton plane. So it makes a very marginal difference where you sit. Accounting for crew bags wt. is just some old template they didn't bother to change from WW2. If the cargo is balanced you're good to go.

Hydraulic systems: not just oil
Planes have pumps to move fuel automatically between tanks. A manual switch override pumping is obviously possible. If somebody is making passengers move about to achieve balance then the automatic systems are kaput. Or their previous career must have been as a boatman. At a lake resort.

Big planes (747ish size) have a trim tank in the tail wings in the horizontal portion. During take off fuel gets pumped to the trim tank. That makes it tail heavy which helps take off. Think of the plane as doing a wheelie.

Tanking matters
Plus the main wing tank has an outer and inner tank. Inner tank fuel is used first. Then outer followed by central tank if available. The fuel is not just for burning. It's weight keeps wings horizontal at take off. Else the upper thrust (school Bernoulli's eqn.) will make the wing U shape. Or maybe not. Just a slight upward curve!

Obviously on landing most of the fuel is spent. That's why on landing you'll see the wings bend upwards more.

If you want to get deeper into the fuel management you may read about usable fuel, drainage fuel, upper and lower pumps, temperatures and fuel density, RAM air pressured tanks, protective layers b/w fuel and passengers, etcetra.

Spies
Now you can theoretically make a plane super rigid and strong like a block of steel. Zero bend anywhere. That is too much weight. And a waste of material. So they achieve strength and lightweightedness by copying the hollow bones of birds. As many of you know from YouTube the SR 71 spy plane would leak fluids - fuel, oils, etc when parked. At operational speed it would get heated and all joints would expand. At that point the plane sealed tight like a vault. If you made it leakproof when cold, it would have become spare parts at Mach 1 temps.

Get rich by cutting out coffee
The main time consuming factor/problem in planes is the passenger boarding. Some don't allocate seat numbers. Some make 1 st class enter first. Both are messy. Airlines use just one loading (steps) truck to save money on rentals. Some don't even use moving type steps. Pretty soon they'll just put a ladder against planes and ask passengers to use it.

B.E.S.T airlines
Airlines must board/exit from all available 4-6 doors. They must give everyone seat numbers. And as a rule inner-most passengers board first.
A Bohemian first class ticket ensures not first in, first out as the airlines do now. But first out only. And an extra free toast.

Last edited by hangover : 27th June 2016 at 10:59.
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Old 27th June 2016, 10:49   #221
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Originally Posted by hangover View Post

Obviously on landing most of the fuel is spent. That's why on landing you'll see the wings bend upwards more.
.
If they use Fuel to adjust the weight distribution, wouldn't it affect the CG at the time of landing?
Since the fuel tanks will be almost empty and would that be enough to adjust the weight distribution?
Or is the CG important for take off only?
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Old 27th June 2016, 16:34   #222
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Default Re: Boeing 777 - Pilot's Review

Quote:
Originally Posted by hangover View Post
Cgi is not a deal breaker. It can be adjusted to an atomic level in new planes. Accounting for crew bags wt. is just some old template they didn't bother to change from WW2. If the cargo is balanced you're good to go.
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If they use Fuel to adjust the weight distribution, wouldn't it affect the CG at the time of landing?
Since the fuel tanks will be almost empty and would that be enough to adjust the weight distribution? Or is the CG important for take off only?
While the limitations of CG do take into account a wide variation in load distribution, proper CG value is extremely important for an aircraft to takeoff properly and fly efficiently. The FMC calculates the takeoff performance values, V1, V2 & V3 based on the CG % and flap values. If I used a value of 35% instead of 26%, the takeoff performance will vary, even though both values are within the limits for a given weight. Please note that the CG referred here is the takeoff CG.

While in cruise, we use another value called the cruise CG, which is set in the FMC. This CG determines your in-flight performance. This value controls your max altitude as well as your maximum maneuver speed in relation to the buffet. For the 773, the value is around 30%. Basically, you're telling the computer that your CG is further aft than the default value, and therefore it can allow a higher cruise level than would have been calculated with the default CG. The default CG of 7.5% is very conservative. The buffet protection required for that value would limit your climb. Also, a higher aft CG means lower fuel consumption.

All said and done, I would definitely say that you could play around with the CG values and get away with it. But that's not the point. With jetliners, the aim is to do everything by the book. Every small and trivial sounding rule is followed because one small mistake can destroy your life and career. Why take chances with it?

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Originally Posted by hangover View Post

Planes have pumps to move fuel automatically between tanks. A manual switch override pumping is obviously possible. Big planes (747ish size) have a trim tank in the tail wings in the horizontal portion. During take off fuel gets pumped to the trim tank.
No, since the 777 does not have those stabilizer tanks, adjusting the CG FWD or AFT by moving fuel from wing to center or vice versa is not recommended by my operator. If there is a FWD or AFT CG issue, the only way is to move passengers. I have not done it, but I know a colleague who did it once. He had to move the first, business and some seats of premium economy to the coach section at the back of the aircraft for takeoff. They weren't happy, but they obliged.

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Originally Posted by hangover View Post
The main wing tank has an outer and inner tank. Inner tank fuel is used first. Then outer followed by central tank if available. The fuel is not just for burning.
No, the 777 burns the fuel from center first and then the main wing tanks. Here is the FCTM photo highlighting the same.
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Old 27th June 2016, 17:12   #223
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Default Re: Boeing 777 - Pilot's Review

To add to what Searchinghaven wrote before

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Originally Posted by hangover View Post
Exam question
300 fat passengers at 100 kg each is 30 tons. That's 7-8% total plane weight. Engines have the capacity to lift a 360 ton plane. So it makes a very marginal difference where you sit. Accounting for crew bags wt. is just some old template they didn't bother to change from WW2. If the cargo is balanced you're good to go.
.
CG is not about weight, it's about momentum along the longitudial axle of the plane. That's very different. And even 100 passengers in a 747 piled in the back and no seats taken up front will make a noticeable different on the CG!

No pilot will ever marginalize the importance of a very thorough weight and balance calculation and check. The weight part of the W&B calculation is, obviously about the total take off weight. The balance part of the W&B is about the Centre of Gravity. It has to be within strict parameters.

Weight and CG determine take off parameters and (when applicable) stabiliser take off settings. And yes, unfortunately sometimes it goes wrong. Aviation doesnt work by rule of thumb. Get the cargo sorted and you're good to go doesn't work. Because there will and have been cases when that is simply not good enough.

As far as I know it is also a legal requirement to perform and document a W&B calculation to do so, on any plane, prior to take off. I know I always do, because that's what a pilot is supposed to do and on top of it, its also a legal requirement.

Aviation and being a pilot is for a large part based on enforcing very strict regimes and sticking to it. That's why we have check list. That's why we have W&B calculation. There is always the danger of people skipping items, because they believe it will be ok. But that is how accidents happen.


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Originally Posted by hangover View Post
Big planes (747ish size) have a trim tank in the tail wings in the horizontal portion. During take off fuel gets pumped to the trim tank. That makes it tail heavy which helps take off. Think of the plane as doing a wheelie.
.
NO, not necessarily, its not about tail or nose heavy perse. It is ensuring the centre of gravity falls within predescribed limits. Its about the plane being balanced in seach a way that aerodynamic forces (wing/stabilizer) can rotate the plane adequeatly within predescribed margins.

I have never ever heard of fuel being pumped to the trim tanks during take off. Could you show me the procedure for pumping fuel to the trim tank of the 747. Never heard of it, certainly not in any of the 747-400 AOMs I have.

In fact on modern airliners once established in cruise, not much fuel is pumped around for trim. Useages of the various tanks mostly follows a predescribed logic and sequence, often automated or in written procedure.

Planes such as the Concorde did have to pump fuel back and forth to ensure proper trim as there is a big difference between flying sub and super-sonic when it comes to the required CoG.

Quote:
Originally Posted by hangover View Post
B.E.S.T airlines
Airlines must board/exit from all available 4-6 doors. They must give everyone seat numbers. And as a rule inner-most passengers board first.
A Bohemian first class ticket ensures not first in, first out as the airlines do now. But first out only. And an extra free toast.
Not sure where the must" comes from? It would be nice, but even on widebodies you would be lucky to see 2 maybe 3 doors used during boarding.

Many studies have been conducted on what is the quickest way of boarding.
First/Business/Economy, by seatnumber, by row etc.

Many test have been run with variying degree of result. As a frequent flyer with Titanium status on three different carriers I would say the biggest factor is how well adherence is being applied to whatever method is used.

The Indian method appears to be a free for all, even when the ground staff specifically asks for boarding by row, very few people adhere and very often I don't see the ground staff taking action. So they announce boarding by row but leave everybody in no matter what.

Jeroen
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Old 27th June 2016, 17:28   #224
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Default Re: Boeing 777 - Pilot's Review

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No pilot will ever marginalize the importance of a very thorough weight and balance calculation and check. The balance part of the W&B is about the Centre of Gravity. It has to be within strict parameters.

As far as I know it is also a legal requirement to perform and document a W&B calculation to do so, on any plane, prior to take off. Aviation and being a pilot is for a large part based on enforcing very strict regimes and sticking to it. ---------But that is how accidents happen.
Exactly. Very well put. It is a FAR requirement to have the exact W&B calculations done, as I had shown in my earlier posts. And as I said, every small and trivial sounding rule is followed because one small mistake can destroy your life and career.

Take the example of National Air Cargo FL102. The aircraft was carrying a consignment of armored vehicles. One of the armored vehicles was not secured properly in the cargo area. During the flight, it shifted, thereby disturbing the balance of the aircraft and crashing it.


Quote:
Originally Posted by hangover View Post
300 fat passengers at 100 kg each is 30 tons. That's 7-8% total plane weight. Engines have the capacity to lift a 360 ton plane. So it makes a very marginal difference where you sit.
Just to add an example of the moment, here is a photo. A boy sitting on the edge with half the mass of the man, will have the same moment as the man. This is because Moment = Force x Arm distance. The pivot that you see in the image is the CG of the aircraft.
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Old 27th June 2016, 17:37   #225
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Default Re: Boeing 777 - Pilot's Review

Ah yes. I forgot this article is about the Boeing 777. Boeings don't use a tail tank except as optional options on some 747 versions. Only Airbus uses it constantly in flight. And I think Concorde.

The CG of the central tank fuel is a little ahead of the dry plane CG. And CG of the wing fuel is slightly behind the dry plane CG. So when the central tank fuel is burnt first (as mentioned by searchingheaven) the CG overall moves backwards. As the wing tanks fuel is used the CG moves forward.

In Airbus planes the tail tank is used continuously. It's further back. So by moving a small amount of fuel back to the tail the CG is easily controlled. Weight X distance calculation.

Both have advantages and disadvantages. The central tank system needs inert gas cooling. Your AC generates heat. To prevent the fuel from igniting due to heat an inert gas system is used in Boeings.

There are more factors here than an IIT exam quadratic equation. The fuel can only be pumped from wing tank to central tank. Reverse isn't possible. When planes bank (turn) how do you endure the dry part of the tank isn't at the pump inlet (use 2 pumps).

Airbus planes don't need inert gas cooling as they don't use a central tank. On most types anyway. They shift fuel tailwards. However it means a lot of pumping back and forth. Plus extra weight of pumps and fittings.

You may ask isn't the Aluminium wing fuel going to get heated due to the sun. Yes a little. Wings have a lot of air pockets and natural cooling possibilities. But the heat due to AC systems next to the central tanks is much more. So nobody uses inert gas system for wing fuel tanks.

Why airlines don't simply top up the tanks every time?
The reason why so much calculation is done on fuel is because a big aircraft can't land with a full load of fuel. Maybe once or twice is okay for testing purposes. Not every time. The landing gear components will simply break.

On average a big plane lands with 10 tons of fuel. It burns up the rest of it (100+ tons) in flight. It needs enough to reach an alternative airport. Or circling. It can't land with only fumes in the tank.

That's why planes dump fuel before emergency landings. The risk of an explosion is not mitigated. (10 tons burns for a lesser time than 100 tons. It's still a fire.) It is to save the landing gear systems.

Last edited by hangover : 27th June 2016 at 17:57.
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