[liferocks]

Originally Posted by apachelongbow

That sounds like the Airbus energy circle or arc. It will show the track miles needed to be at approach config speeds based on current airspeed, configuration and rate of descent. It's available only on heading mode.

Hi.. This arc on a Boeing is little different from Airbus. In Boeing you don't necessarily need to be in heading mode to get that arc.
Another difference is that you get that green arc in Boeing for any altitude difference, Let's say you are descending from FL 200 to FL 100. This green arc will give you an estimate to as in, where will you reach FL 100 depending upon your present rate of descent.
That's how it works on Boeing.

[searchingheaven]

Originally Posted by A350XWB

Any specific reason to skip the mention of PW and RR engines?

Actually, it is (rather, was) available in 6 variants
777-200, 777-200ER, 777-200LR, 777F, 777-300 & 777-300ER.

I would be interested in some measurements or statistics for this. I keep searching and could not find any on-line.

The first -200LR was delivered to Pakistan International Airlines on February 26, 2006. The first -300ER was delivered to Air France on April 29, 2004. That makes them 10 and 12 years old respectively and not 20.

According to your post above, a difference of 0.0125 is head to head and a difference of 0.0018 will be difficult for the A350-1000 to hold its own. Can you explain this?

1. I specifically mentioned that I fly the 777-300ER and hence I will be reviewing that model only. So I found no reason to mention the other engines.

2. I was mentioning the seating capacity of the 5 variants and hence excluded the 777F, since it is not a passenger aircraft.

3. I am a pilot who flies the 777 as his daily job so I can assure you that the 777 handles turbulence better than the A330/A340. My captain told me that the reason for this was wing rigidity. Also you can ask any passenger and he will tell you that the 777 feels more stable in bad weather. Read this: Link to article

4. That is a mistake on my part. I should have mentioned that the 777's initial models were 20 years old and not the 777-200LR and 777-300ER. My apologies for this.

5. In terms of the CASM, the difference is 0.0018 is minimal. The problem is the seating capacity of A350-1000, which in a 3 class configuration will be around 57 seats lesser than the 777X. That is going to be the 777X's biggest advantage, since the 777X will have a higher capacity with the same range.

Originally Posted by napster1311

Thanks for such an informative and detailed review. Thought I accept it took me huge amount of time and effort to gulp so much technical information. I have always found Boeing way more comfortable than Airbus. More pictures would have been a delight. Thanks again.

Thanks for the compliments napster. I am glad that you liked it.

[napster1311]

Thanks for such an informative and detailed review. Thought I accept it took me huge amount of time and effort to gulp so much technical information. I have always found Boeing way more comfortable than Airbus. More pictures would have been a delight. Thanks again.

[A350XWB]

Originally Posted by searchingheaven

1. I specifically mentioned that I fly the 777-300ER and hence I will be reviewing that model only. So I found no reason to mention the other engines.

The thread title reads "Boeing 777 - Pilot's Review". I might be nitpicking

Originally Posted by searchingheaven

2. I was mentioning the seating capacity of the 5 variants and hence excluded the 777F, since it is not a passenger aircraft.

Again, I mentioned it because of the thread title.

Originally Posted by searchingheaven

3. I am a pilot who flies the 777 as his daily job so I can assure you that the 777 handles turbulence better than the A330/A340. My captain told me that the reason for this was wing rigidity. Also you can ask any passenger and he will tell you that the 777 feels more stable in bad weather. Read this: Link to article

I'm no pilot, but an aviation enthusiast and a member of the airliners.net because of my passion. I have read multiple threads on the forum regarding the turbulence handling ability of various airliners. But could never find any data substantiating that (In one of the threads there, it was told that the 340 is having the highest turbulence tolerance). I was specifically looking for some statistical data. One thing I know of is that the wing loading of the 777 is higher than most other airliners, which is one factor here.

Originally Posted by searchingheaven

4. That is a mistake on my part. I should have mentioned that the 777's initial models were 20 years old and not the 777-200LR and 777-300ER. My apologies for this.

No apologies please. The earlier models of 777 are indeed 20 years old. But the 773ER is still going strong and it exceeded even Boeing's predictions I suppose.

Originally Posted by searchingheaven

5. In terms of the CASM, the difference is 0.0018 is minimal. The problem is the seating capacity of A350-1000, which in a 3 class configuration will be around 57 seats lesser than the 777X. That is going to be the 777X's biggest advantage, since the 777X will have a higher capacity with the same range.

Here, I beg to differ. Profitability is not only driven by CASM. If an airline cannot fill the additional seats, it becomes an overhead for them. Higher number of seats does not always translate to better economics.

[Jeroen]

Originally Posted by vinair

After push back, when taxiing (hope that's the right spelling!), is there some sort of a 'idle setting' for the engines to run just enough to move all the bulk of the aircraft on the ground?

Also, just before take off, does the plane only depend on the brakes to stay still while the engines are being pushed for max thrust?

For the 747, you need to push the engine up a fair bit to get it rolling, especially when fully loaded. But once it rolls, the throttles go back to idle and that tends to keep it rolling pretty steady at a good enough pace.

I'm not sure whether jets go to full thrust regularly before they release the brakes. As far as I can tell/have seen they might spool up to 60-70%, then release the brakes and subsequently hit the TOGA button or manually set take off thrust.

There is nothing else then the brakes that can hold you in place on the runway.

On my little planes we use full thrust whilst keeping the brakes fully locked as part of a so called short field take off. Before releasing the brakes you want to have the engine/propeller providing maximum thrust

Also, on single engines we always do a what is called engine run up before we enter the runway. So along the taxiway we turn into the wind, apply brakes and run the engine up (how much depends a bit per plane, could be full power), verify that all engine parameters are normal and check the proper operation of the variable pitch propeller a few times.

[searchingheaven]

Originally Posted by A350XWB

I have read multiple threads on the forum regarding the turbulence handling ability of various airliners. But could never find any data substantiating that (In one of the threads there, it was told that the 340 is having the highest turbulence tolerance).

Here, I beg to differ. Profitability is not only driven by CASM. If an airline cannot fill the additional seats, it becomes an overhead for them. Higher number of seats does not always translate to better economics.

The thread I linked to in my earlier answer is an airliners.net thread. And it specifically states that the 777 is much more stable in handling turbulence. Read from post no 12 onwards.

Of course, it depends on whether the operator can fill the the extra seats. But the 777X's strength resides in its operational flexibility. Remember that most A380 routes currently run at around 75-80% occupancy which comes to around 450 passengers in a 3 class config. So, there is a market for that kind of seating capacity. This market demand, combined with the fuel efficiency of the 777X will make things difficult for the A350-1000.

Originally Posted by vinair

After push back, is there some sort of a 'idle setting' for the engines to run just enough to move all the bulk of the aircraft on the ground?

Also, just before take off, does the plane only depend on the brakes to stay still while the engines are being pushed for max thrust?

Well, the thrust required to taxi depends on the aircraft's ramp weight. A lightly loaded aircraft requires little more than idle, whereas a heavily loaded aircraft requires a lot more. The break-away thrust is the thrust required to get the aircraft moving under any given condition. After the aircraft is moving, the thrust levers are normally moved back to idle until more power is needed in order to maintain speed or speed up. We also have to allow some time for airplane response before increasing thrust further. Our carrier has a policy is that if it takes more than 40% N1 to move you must confirm that the area behind is clear or get a tug. For the 777, the engines are so powerful that if we are not careful with the throttles, the plane exceeds the taxi speed limits sometimes. Sometimes, reverse thrust has to be deployed for better control.

In general, a rolling takeoff procedure is recommended for setting takeoff thrust. It expedites the takeoff and reduces the risk of foreign object damage or engine surge/stall due to a tailwind or crosswind. A standing takeoff is achieved by holding the brakes until the engines are stabilized, ensuring the nose wheel steering tiller is released, then releasing the brakes and promptly advancing the thrust levers to takeoff thrust.

Allowing the engines to stabilize provides uniform engine acceleration to takeoff thrust and minimizes directional control problems due to asymmetric spooling. Also note that brakes are not normally held with thrust above idle unless a static run-up is required in icing conditions.

[quickdraw]

Originally Posted by searchingheaven

[*]First off, a lot of those switches you see are circuit breakers. Electrical failures and troubleshooting have to be handled while still flying the plane. These circuit breaker isolate a specific subsystem in case it fails.

This is exactly what I don't understand, if a system has failed the flight computer should isolate it automatically with respect to whatever is mentioned in the guidebook anyways, and make the pilot aware of the situation, why does the pilot have to manually intervene.

Originally Posted by searchingheaven

[*]When you're in a aluminum tube at 35000 ft with 300 people as your responsibility, the last thing you want to do is rely on a computer having 100% control over ANYTHING. The cockpit has manual controls and redundant systems for almost all subsystems onboard. About 60% of the switches never need to be flipped, but you want to have absolute control over everything for any sort of "just in case" moment, because at 35,000 ft. you don't have any other options if something goes wrong. Redundant controls also increase the complexity but add to the safety.

I disagree, more proprietary control switches doesn't necessarily mean its safer. In even of physical damage to all these circuit breakers/control knobs it will be impossible to change the settings. My point was why not have a control system which allows to control all systems. And have redundancies for it. Much more efficient IMHO. In a more simple way its like putting 10-20 iDrive controllers in the cockpit They are assigned a certain role but when need be their function can be changed.

Originally Posted by searchingheaven

eg. A perfect example of this is the RAT(Ram Air Turbine). It is a small turbine that is connected to a hydraulic pump, or electrical generator, installed in an aircraft and used as a power source. In case of the loss of both primary and auxiliary power sources the RAT will power vital systems (flight controls, linked hydraulics and also flight-critical instrumentation). On 5 flights till now, RAT has proved to be a savior, providing flight control when both engines have failed or power sources have failed.

A 777-300ER landing with the RAT deployed.
Attachment 1506911

I was talking more about the physical switches in the cockpit and not the systems themselves. But this is very interesting, reading up more about the RAT turbine implores me to ask you, if the engines are down and APU is not working is there no electricity stored to operate the instruments and control surfaces? Why not have batteries that can power aircraft for a certain stipulated period of time? The RAM system's biggest weakness seems to be it fails when you need it the most (closer to the ground during landing)

Nevertheless found this interesting article.

https://en.wikipedia.org/wiki/Gimli_Glider

Originally Posted by searchingheaven

As a small example, my father works on a software called Android Studio or something like that. I find that software absolutely horrendous to even understand. For you guys, it probably is very easy to understand. It's just because of my non-familiarity with it.

Android Studio is software to create software, it is not created to be intuitive. For intuitive software check any Apple creation tools (iMovie, Garageband etc.) I understand that after using it for a while you get used to it. Let me try and get my point across in a car manner. BMW and Audi create cars, both of them have instruments inside which show specific information that is vital to operation of the car and have controls for operation of various features of the car, although their layout is a little different on a basic sense its the same the information required would be the same for drivers of both these cars and its in the same place (Speedo, Tacho etc.) Why do aircraft manufacturers don't have standard cockpit layout for these controls/knobs/screens. This should cut down on retaining time and cost considerably, and they can still have their philosophy intact (Airbus can have joystick etc.)

Originally Posted by searchingheaven

Well, we don't access whatsapp at 35000 ft. , but we surely do relay important data from the aircraft to the ground using ACARS.

A sample ACARS transmission.
Attachment 1506923

I thought pilots can access in-flight WIFI. Also whats the frequency of ACARS transmissions? What tech do they use to relay this, why cant it have more info?

Originally Posted by searchingheaven

AF447's crash was a very unfortunate event brought about a lot of attention to what I said about the first point. Let me explain the crash to you first.

When the pitot pressure probe on the outside of the plane iced over, the airspeed indications became unreliable. The computer could no longer tell how fast the plane was going, and the autopilot disengaged. The fly-by-wire system switched to alternate law. First off, the crew failed to realize that the FBW had switched to Alternate law, which does not provide stall protection. Second, the crew were disoriented and didn't realize that they were stalling until the last minutes.

I believe that the autopilot cannot engage automatically when the airspeed becomes reliable. Anyway, by that time, both the pilots had already pressed the priority button & dis-engaged the autopilot.

I actually was avoiding talking about this, but the weakest link in a system has always been human beings. Hundereds of people died for absolutely no reason because two human beings sitting next to each other failed to communicate and stalled a perfectly fine plane.

One silly question that comes to my mind is why don't airplanes use GPS for speed measurement and still rely on mechanical methods?

Lastly, maybe Coolboy007 can answer, has airbus changed anything inside their cockpit to give better visual indication of current stick input and which stick has requested priority?

Originally Posted by searchingheaven

I seem to have missed this question the first time.

The Airbus vs Boeing debate

To start off, let me get one point out of the way. Both Airbus & Boeing produce VERY SAFE aircrafts... [truncated post] ...es flare mode is not available so aircraft is put in direct law for landing. Direct law is flare mode of alternate law.

This is why I love Boeing, so captain I'm putting my trust in you. Get me home safe.

[Jeroen]

Originally Posted by searchingheaven

A standing takeoff is achieved by holding the brakes until the engines are stabilized, ensuring the nose wheel steering tiller is released, then releasing the brakes and promptly advancing the thrust levers to takeoff thrust.
.

What do you mean with the nose wheel steering tiller released? I assume you would steer initially with the nose wheel until such moment your rudder gets enough authority based on air speed?

Thanks

Jeroen

[Jeroen]

Originally Posted by quickdraw

This is exactly what I don't understand, if a system has failed the flight computer should isolate it automatically with respect to whatever is mentioned in the guidebook anyways, and make the pilot aware of the situation, why does the pilot have to manually intervene.

Planes have typically multiple redundancy system and they kick in fully automotically without any intervention from pilots. E.g. hydraulics, electrical system, various navigation system. Pilots will get an annunciation on what is happening.

Based on these annunciation they will run through checklist on what to do next, what to account for etc. E.g. if a hydraulic pump fails, the other hydraulic circuits will take over. An alarm annunciation is raised. Depending on which hydraulic circuit was impacted the pilots might have to plan for instance their landing differently. For instance, on the 744 depending on which hydraulic system is affected you will have to choose different autopilots and your autoland capabilities are effected differently for different hydraulic systems.

Originally Posted by quickdraw

I disagree, more proprietary control switches doesn't necessarily mean its safer. In even of physical damage to all these circuit breakers/control knobs it will be impossible to change the settings. My point was why not have a control system which allows to control all systems. And have redundancies for it. Much more efficient IMHO. In a more simple way its like putting 10-20 iDrive controllers in the cockpit They are assigned a certain role but when need be their function can be changed.

One reason to have circuit breakers in the cockpit is because it is necessary to be able to isolate certain circuits. Sometimes as part of trouble shooting, or as part of MEL (Minimum Equipment List) procedures.

Originally Posted by quickdraw

I was talking more about the physical switches in the cockpit and not the systems themselves. But this is very interesting, reading up more about the RAT turbine implores me to ask you, if the engines are down and APU is not working is there no electricity stored to operate the instruments and control surfaces? Why not have batteries that can power aircraft for a certain stipulated period of time? The RAM system's biggest weakness seems to be it fails when you need it the most (closer to the ground during landing)

All planes have batteries. In case of an all engine failure, the jet engines are still spinning by the air rushing through them. The hydraulics and possibly even the generator could still be powering the system, but on 2 engine planes the RAT provides additional power. ON the 744 with four engines, there is no RAT. The four engines wind milling, provide enough emergency power to keep flying. Electrical power is provided by means of battery back up.

Originally Posted by quickdraw

I thought pilots can access in-flight WIFI. Also whats the frequency of ACARS transmissions? What tech do they use to relay this, why cant it have more info?

Depends on where the plane is. Depending on the set up, ACARS communicate on VHF or or satellite frequencies. There are even a few other possibilities. Whereas VHF frequencies are free of charge, satellite comms is not. So some airlines choose not to communicate on ACARS during the flights when out of VHF range. (Remember MH370?)

Originally Posted by quickdraw

One silly question that comes to my mind is why don't airplanes use GPS for speed measurement and still rely on mechanical methods?

GPS provides ground speed. Whereas ground speed is relevant for determining how fast you get from A to B, pilots are far more interested in air speed, because that determines how much lift you get. Without airspeed, groundspeed is pointless.

Groundspeed is indicated on the various displays, including wind component. How that is calculated (the ground speed) is up for much debate. Many pilots believe it starts with GPS speed. But then again there is not even a definition for GPS speed. (is it distance over time or doppler based). It is one area of aviation systems I have extensively researched for he 744 over the years and although I have some idea, nobody has been able to provide me with detailled technical details yet.

To be honest, it doesn’t really matter to the pilots, What they see on their display as ground speed and windfactors is perfectly fine. I’m just very anal when it comes to all things GPS.

Jeroen

[searchingheaven]

Originally Posted by keroo1099

Lovely thread.

Don't want to sound disrespectful but how do you keep your concentration levels up during long flights if you are really not 'flying' most of the time. It seems automation on commercial flights have made you redundant except for takeoffs, landings and emergencies.

For me the situation is similar to driving on long straight expressways because it reduces my focus and ultimately gives me less chance to react in time to an emergency.

I'm so glad you like it.

It’s true that a few minutes after take-off, we engage the autopilot. This, however, is not the end of our work! The autopilot cannot think, or talk to the air traffic controllers. That is our work. We also have to manage the autopilot functions thought the MCP and the FMC. We have to talk to the controllers continuously. At the same time we have to avoid a thundercloud and decrease speed due to traffic. Although it is true that once at cruising altitude our workload decreases a bit. One of us gets some sleep in the cockpit and then we alternate. Once we reach the top of descent, the cockpit becomes busy again. We talk about all the different options. We take the latest weather reports from the destination airports and know what approach to expect. The last 30 mins are the most demanding in terms of concentration. We constantly calculate our vertical profile (too high? too low?) and talk to different ATC's. The landing is manual most of the time.

Originally Posted by quickdraw

1. This is exactly what I don't understand, if a system has failed the flight computer should isolate it automatically with respect to whatever is mentioned in the guidebook anyways, and make the pilot aware of the situation, why does the pilot have to manually intervene.
   
2. I disagree, more proprietary control switches doesn't necessarily mean its safer. In even of physical damage to all these circuit breakers/control knobs it will be impossible to change the settings.
   
3. The RAM system's biggest weakness seems to be it fails when you need it the most (closer to the ground during landing)
   
4. Android Studio is software to create software, it is not created to be intuitive. For intuitive software check any Apple creation tools.Why do aircraft manufacturers don't have standard cockpit layout for these controls/knobs/screens. This should cut down on retaining time and cost considerably, and they can still have their philosophy intact.
   
5. I thought pilots can access in-flight WIFI. Also whats the frequency of ACARS transmissions? What tech do they use to relay this, why cant it have more info?
   
6. One silly question that comes to my mind is why don't airplanes use GPS for speed measurement and still rely on mechanical methods?
   
7. Has airbus changed anything inside their cockpit to give better visual indication of current stick input and which stick has requested priority?
   
8. This is why I love Boeing, so captain I'm putting my trust in you. Get me home safe.

Answers are given point-wise:

1. This is exactly what happened with AF447. The airspeed indicators failed and hence the computer rejected the airspeed values and isolated that system. Since the autopilot depends on the airspeed, the autopilot was also disconnected by the computer. The computer did isolate the faulty system and then informed the the pilots that it had switched to the alternate law. So what you're talking about is already in place. The fact that pilots failed to respond to the stall is another issue.
   
   
2. Modern airliners are built to provide an extremely high degree of reliability. All the systems failing at a time is not only improbable, it's impossible.
   
   
3. When everything has failed, the RAT deploys in a last attempt to save the plane and everyone on board. Batteries cannot provide enough power to run the hydraulics required for control surfaces and they are inefficient, in addition to being very heavy. The ram air turbine produces just enough power to run basic navigation, a very basic fly by wire, and limited control of a few flight surfaces, but it will be enough to get the aircraft through an emergency landing.
   
   
4. The basic cockpit layout is almost the same for both Airbus. The philosophy is different but the majority of instrument are in the same location. The primary flight display, the navigation display, the engine parameter display(EICAS or ECAM), FMC, throttles, brakes, rudders are all in the same place, aren't they? Even the overhead panels have some resemblance to each other. They aren't exactly the same because the systems are differently modeled. Yes, the terminologies are somewhat different but most of the instruments are in the same location on both Airbus & Boeing.
   
   
5. I didn't mean to say that we can't access wi-fi on flights. We can and sometimes do.
   
   ACARS stands for Aircraft Communications Addressing and Reporting System. It uses VHF radio signals that are received and sent by a global network of land based radio stations and satellites. ACARS provides data like weather, flight plans, technical information on the aircraft, information on aircraft components such as engines, and for communications between the flight crew and ground support teams.
   
   Some examples for you:
   
   

   • N732ANAAL088J#CFBWRN/WN14021208290022000006AUTO FLT FAC 2 FAULT
     The first part identifies the aircraft as registration number N732AN, it’s callsign for this flight is AAL088. The next part is the ACARS data – in this case the aircraft is reporting a fault.
     
   • N673UA UA0985 M1BPOSN51210W001338,BEDEK,082231,140,NIGIT,082458, D273L,M19,24058,225,/TS082231,120214798E
     This ACARS message is a position report from United Airlines Flight UA985
     
   • VTALU AI0229 3401 ETA 0229/12 EGLL/LIML .EI-DTE/ETA 0915/FOB 0051
     Estimated Time of Arrival report
     
   • N12114 CO0070 1EHAM REQUEST GATE ASSIGNMENT ETA0447
     This is a gate assignment request.

6. I have said this before in another thread probably. GPS is very inaccurate for speed measurement. Also note that an aircraft is not about the ground speed but the airspeed. The GPS can only measure ground speed. Pitot tubes are the most accurate and reliable method to measure the airspeed. The only thing to ensure is that they aren't iced or their air inlet is not blocked.
   
   
7. Airbuses already provide enough indication to the pilot's regarding sidestick priority and use on the glareshield panel. Aural warning "DUAL INPUT" also sounds on the speakers. This will help you understand better than my explanation.
   
   
   
   
   
8. Thank you for placing your trust in me. But I can assure you that Airbus's pilots and their aircrafts can be trusted as much as ours. Their safety records speak for themselves.
   

Originally Posted by Jeroen

What do you mean with the nose wheel steering tiller released? I assume you would steer initially with the nose wheel until such moment your rudder gets enough authority based on air speed?

Thanks

Jeroen

The tiller and rudder pedals can both control the nose wheel steering. The tiller allows the nose gear to rotate to about 70 degrees. The rudder pedals only allow the nose gear to rotate about 7-9 degrees. Therefore, the tiller is used for all turns, but once on the runway and straight, the rudder pedals are used. In the 777, if the nose wheel steering tiller is not released before application of takeoff thrust, a configuration warning may occur due to the aft axle steering being out of the locked position.

[karan561]

Originally Posted by Jeroen

Recently some aircraft tire has been in the news. Not sure what brand, not sure it would be good PR either. Have a look at this square tire:

http://avherald.com/h?article=498050d8

The same thing happened not to long ago to a 777 too

Jeroen

Ouch, that square tyre looks so weird, now it makes sense to have more than 4 tyres in a set of landing gear on one side (at the rear) so that if one tyre goes bust the plane can still land .

Also i read in one of the comments a very valid explanation;

"The tyre is square because it deflated at altitude, so the pressure inside reached a pressure altitude of say 35,000ft. The A380 tyres are 1400x530R23 40PR. These tyres have very strong but light (nylon+aramid reinforced sidewalls. When the aircraft descends, the atmospheric pressure crushes the tyre and the sidewall collapses inwards, giving the tyre its square shape. I've seen this on A340-600s with the same tyre size."

Originally Posted by apachelongbow

I will try and answer from an Airbus perspective since I fly one, however most systems are common to Airbus Boeing or other manufacturers.

Tyres are tubeless, filled with pure nitrogen and designed to operate at high speeds. The Airbus 320 tyre is rated at 195 kts..approximately 360kmph. The main landing gear wheels are larger in size than the nose wheel. The brakes are only on main landing gear and nose wheel is free castoring type.
Brakes are carbon brakes made by a subsidiary of Bugatti and operate at high temperatures. A typical 64 tonne landing weight aircraft stopping down the runway increases break temperature to about 300 degrees. Types are replaced per x number of landings. Each landing takes out a portion of rubber from the tyres which you can see as black strips on the runway. Tyres can be reconditioned once before being thrown away.

Thanks for the details

[Jeroen]

Originally Posted by searchingheaven

[*]I have said this before in another thread probably. GPS is very inaccurate for speed measurement. Also note that an aircraft is not about the ground speed but the airspeed. The GPS can only measure ground speed. Pitot tubes are the most accurate and reliable method to measure the airspeed. The only thing to ensure is that they aren't iced or their air inlet is not blocked.

Technically speaking GPS speed is very accurate, nearly all GPS chipsets measure speed by using the doppler effect. Event the cheapest Garmin Etrex from 10 years ago used doppler speed. Even if they would use time over distance it would be very accurate too. (This contrary to popular belief that the various inaccuracies in the measurement play a role in time over distance. They don’t as they are near constant within a limited geographical distance and time space).

However, in order to get an accurate reading you need to travel at a steady pace, no acceleration or deceleration. As discussed more importantly its ground speed only. That’s the foremost reason, pilots first and foremost need to know what their air speed is,

Originally Posted by searchingheaven

The tiller and rudder pedals can both control the nose wheel steering. The tiller allows the nose gear to rotate to about 70 degrees. The rudder pedals only allow the nose gear to rotate about 7-9 degrees. Therefore, the tiller is used for all turns, but once on the runway and straight, the rudder pedals are used. In the 777, if the nose wheel steering tiller is not released before application of takeoff thrust, a configuration warning may occur due to the aft axle steering being out of the locked position.

That must be 777 specific? I don’t think I’ve seen that on the 744. I certainly don’t see it in the various check list. Obviously, on the 744 the rudder panel also control the nose gear in a much smaller arc then the tiller.

Jeroen

[searchingheaven]

Originally Posted by Jeroen

However, in order to get an accurate reading you need to travel at a steady pace, no acceleration or deceleration.

That must be 777 specific? I don’t think I’ve seen that on the 744. I certainly don’t see it in the various check list. Obviously, on the 744 the rudder panel also control the nose gear in a much smaller arc then the tiller.

Jeroen

That is why I said that GPS is inaccurate for airspeed measurement since the speed isn't constant. And that is why pitot tubes are used.

Also, disconnecting the tiller is only because of the steerable aft axle in the nose gear being out of locked position. It is 777 specific.

[Jeroen]

Originally Posted by searchingheaven

Sometimes, reverse thrust has to be deployed for better control.
.

So you are using reverse thrust during taxi? Why not just use the brakes?

I don't think I have seen or read about using reverse thrust during taxi, is this company or 777 specific?

Jeroen

[searchingheaven]

Originally Posted by Jeroen

So you are using reverse thrust during taxi? Why not just use the brakes?

I don't think I have seen or read about using reverse thrust during taxi, is this company or 777 specific?

Jeroen

Reverse thrust is used in the 777 during taxi as well due to the extremely powerful engines. Carbon brakes are efficient but using them constantly to keep the plane from accelerating wears them out. So we use reverse thrust at idle to essentially cut the available thrust to half. Note that the use of reverse thrust above reverse idle is not recommended due to the possibility of foreign object damage and engine surge.

PS: I specifically remember seeing KLM 744s using single engine reverse thrust while taxiing at Schipol l when I was there 8 days ago.