With light taxi power set, it takes too long to accelerate to a proper taxi speed. I use a fair amount of power to get speed up to a decent figure and control with brakes from then on. You do not use differential brakes on big jets, and even differential power is not usually recommended. During taxi there is no set power- speed depends on weight, wind direction and taxiway slope. You just have to take it as it comes and keep on top of it.

Maybe you don't, but many of us do, especially on wet or slippery surfaces.

AnthonyGA, my experience is that FS does not accurately simulate aircraft taxi characteristics.

PLEASE! If you're asking about simulators instead of real airplanes, make that clear in your post!

Real Airplanes
 

In the real world,

It takes a little extra thrust to get rolling, but once you are moving idle is pretty much all you need. On a flat you may need brake to keep speed under control, but the only time I use extra thrust is going uphill or around a sharp corner.

From mostly flat airports,

Joe

The Boeing recommended way, for a light B757,767 and 747-400 is to get the aircraft moving and let it accelerate to no more than 20kts then firmly apply brakes and reduce to a fast walking pace, release the brakes and repeat. Am told it will minimise brake wear.

Rainbow
 

Training on the B.777 for BA was to use one side to slow during taxi and the next time use the other side. (Back in the 1990's anyway) Something to do with wear on carbon brakes being less rather than helping in a turn.


Regards
Exeng

Thanks for the replies. Looks like I'm safe setting the throttle to produce gradual acceleration and then tapping the brakes to slow down as required, if that's the way Boeing says to do it. I was worried about wear on the brakes or heating them up too much, but apparently that's not an issue.

I've not tried differential braking much because I figure it isn't used often in real life on large aircraft, and replies here seem to confirm that. It doesn't appear to have much effect in the sim unless I press one brake considerably harder than the other (in a small Baron, the aircraft will swing to one side with even the slightest differential pressure). I'll have to try the alternating technique and see how that works.

I suspect the throttle quadrant I have for my sim is a bit stiffer than the real throttle levers, and the range in which the throttles must be adjusted to go from slowing down to speeding up seems to be very small. Perhaps it's easier to make such small adjustments with the real throttles.

I haven't tried differential thrust at all (it's too hard to move the throttle levers separately in the sim), so I'm glad to hear that it isn't frequently used, as I was wondering about that as well.

Of the several aircraft I fly in the sim (737-800, 747-400, and 767-300ER), only the 767 seems to want to roll spontaneously at idle. The other two will eventually coast to a very gradual stop at idle thrust, depending on the weight of the aircraft and other stuff, of course. I'll have to try them all empty sometime to see what that does.

Autoland Capability
 

I'm wondering if the autoland capability that most large transport jets have is really needed. How often are airplanes approaching their final destination that have visibilities of under half a mile? (maybe 1/20 flights?) So all those other times the system is not being used and creates a loss for the operator... And for all the other times that the plane IS landing in poor visibility why can't HUDs be installed and pilot lands the plane using the HUD this is a much chepaer than have an autoland system.

What makes you think a HUD is cheaper than an autoland system? What is the relative level of training and maintenance required for both? After all, the autopilot systems are already installed (2 or 3 for redundancy), and the integration into the autoland system is well understood. By contrast, HUDs are relatively new in the airline world, and certification is not a piece of cake...

In Low Visibility Procedures aircraft land "hands-off", ie fully automatically, thereby removing any requirement for an HUD...

DV window
 

Hi could someone please tell me why the opening side cockpit window is known as thr DV window? Thanks Nick

Direct Vision. What you see is what you want.

i think its cheaper because mechanics and pilots have to constantly check if the EXTREMELY complex autoland system works, if it fails during low visibility - a diversion is needed, while in a HUD I'm quite sure that the system is much simpler since all it requires is to display primary display in another place (ie the HUD). I also don't think that the HUD system is new since a lot of old fighter jets already had that system and pilots coming from the military (back in those days) could have already known how to operate so the retraining would have been much cheaper for the operator, thus saving money once again.

So what would your proposed HUD display?? You still have to have the complex autoland equipment to get the aircraft on the ground.

With great respect, I don't think you fully appreciate the situation.. An HUD by itself cannot get the aircraft down in poor visibility - it's simply a way of displaying information to the pilot; a great deal of other equipment is required so an HUD cannot replace an autoland system.

but when the pilot is using the the HUD he is landing the airplane himself..... so there is no need to have an autoland system...

Yes there would be. HUD merely enables the pilot to fly head-up and see instrument information while looking through the window at the same time. It doesn't solve the problem, of actually seeing what is in front of you. There is a formalised requirement that the minimium visibility for pilot to obtain sufficient visual reference of outside world so that s/he can correctly judge the aircraft position, velocity and trajecotry in order to land safely is 300 m. With a HUD and 200 m RVR, there still woul be no benefit. Autoland can solve this. Actually, have solved this 40 years ago.

I would say 1/500 flights. But the operators decide what is best, to divert, not to fly at all, or pay for an autoland. Imagine you divert, crew runs of of duty time and in 2 hours the weather clears up and you have customers waiting for the return flight. The costs are immense and so is the competitive advantages for those with autolands. That's why manufacturers developed and successfully sell autoland equipment. These days it a well proven, easily obtainable, and operationally very benefical technology.

Talk of HUDs makes me thing of a question that has puzzled me for a long time: How do you keep the HUD aligned with the scene outside? I mean, if you are looking directly through the HUD, and the lines on the HUD match the contours of the runway ahead exactly, what happens if you move your head to one side? Don't the lines on the HUD shift out of alignment then?

Seems to me that either you'd need something to clamp your head in place relative to the combiner of the HUD, or the HUD would need some sort of optical system that somehow keeps the lines on the HUD in the right place no matter what the position or angle of your view through the combiner. So how is it done?

I'm not actually that keen on the idea of HUDs and I'm glad that they are not widely used.

De-icing Question
 

I have been following the very interesting Iberia IB6166 BOS-MAD thread and it has prompted a SLF de-icing question.

A couple of winters back I was on a TOM 737 flight from BOH to CDG. It was middle of the day no frost and about +3c. While we were boarding it started raining. After boarding the capt announced there would be a 'short delay for de-icing', which was a bit of a surprise. The Ryanair next to us departed without de-icing.

As the sector from BOH-CDG is short it may be that the a/c didn't require fuel (at ambient) and as TRT was short from the previous arrival would the decision to de-ice in positive ambient temperatures and rain be based on the potential below 0c fuel temperature in the wing from the previous flight causing freezing on contact? If so how does the PIC make this judgement call as I assume it takes a long time for fuel temps to normalise to ambient field level temps that are only a few degrees above freezing?

hud head clamp
 

the idea is that you use the eye liner, the three balls on the centre windscreen post, to ensure your head is in the correct spot.
BUT the HUD has a very small angle of view, so very often a small head movement moves the huds display out of the direct and correct line of sight.
Not normally a major problem, I find the worst problem, is the very slight lack of infinity, and thus a slight re focus is required. Now thats a problem.

Knife-Edge - the decision on whether to de-ice is a complicated one. If your a/c had a longish inbound sector the wings would have been well below zero and any rain would freeze on them (known as 'rain ice'). Often an upload of 'warm' fuel (normally well above ambient temperature since it is normally stored underground) will clear the ice. The Ryanair may have had a short inbound sector or uplifted fuel - or both. One hopes that consideration was given to de-icing and I'm sure it was. Normally a combination of experience, indicated wing fuel temperature and a look at the way the rain behaves as it lies on the wing will make the decision. No doubt your Tom Captain made the correct decision:ok:

The except from the A320 FCOM answers your question:


YS

Taxi procedures for heavies at TNCM
 

This is for anyone who has been to TNCM in a heavy, particularly a 747:

What are the real-world taxi procedures for TNCM for heavies? I've been asking around and looking around and I'm still not clear where the heavies turn around. Apparently they all go to taxiway Charlie, then backtrack along the runway to get to the start of runway 9, but I don't know if they take that little taxiway near the 09 end for their 360 to line up, or whether they backtrack all the way to the end of the runway and then turn around in the tiny space provided on the north side. Which procedure is used in real life? Or is the real-world procedure something entirely different?

Likewise, for landing, what's the usual procedure for large aircraft? Do they go all the way to the end of 09 and then backtrack to Charlie, or do they stop at that intermediate point where there's a space to turn around, or what? I have quite a bit of difficulty turning a 747 on either spot; with the tiller hard over and lots of brakes on the right side I can just barely squeak by, although the brakes are usually excessively hot on that side by the time I reach the gate.

Clunky engine noise on 737 ??
 

Whilst waiting on the spectators balcony at LPMA recently, I watched an Easyjet 737 arrive. As the engines spun down I could hear this god awful clunk with each revolution of the starboard engine. The ground crew didn't seem concerned, neither did the captain when he did a walkaround and gave the fan a spin with his hand (and the clunk was there as he did it).
I've never heard this before.
Any ideas on what it might be, and why nobody seemed concerned ?

I think it's the fan blades making that noise, the blades are seated in the hub but have a small gap in them (presumably for expansion) and you hear a clicking or ticking noise when they move downwards. It is very prominent when a breeze is going through the engine. I will be the first to admit I may be wrong, maybe someone can correct or elaborate for me.

Aircraft brakes
 

There is a thread in the flightdeck forum discussing a recent incident at Changi.

It is suggested that pliots can not use braking if the AC is rolling backwards as the result could possibly be an unplanned rotation. :)

Is it not possible to apply brakes to the nose gear only to prevent any danger of the aircraft ending up sitting on its tail?

The vast majority of aircraft only have brakes on the mainwheels. Good idea though.

Regards,
BH.

I was once sitting in the back seat of a C172 parked facing up a bit of a slope. For some reason mein Kapitan released the handbrake before start up and we started to roll backwards towards the clubhouse. He applied the brakes quite heavily and, no doubt assisted by 200lbs of yours truly perched aft of the centre of gravity, we came awfully close to ploughing a narrow furrow with the bottom of the rudder! Not an auspicious start to a jolly...:rolleyes:

The C-17 demo at Farnborough one year included a reverse thrust exit from the runway followed by some enthusiastic braking and a distinct lifting of the nose gear! The crowd loved it.:ok:

Pushbacks at Paris Orly
 

Flew out of Orly on Monday night and as we were pushing back I noticed that an AF 321 was being pushed back with the tug attached to the underwing left side undercarriage. I have never seen this before and it looked like an inefficient way of doing it.

Any ideas?

3 Pilots to Innsbruck?
 

I recently flew to/from LGW to Innsbruck (LOWI) for a ski-ing holiday with Easyjet on an A319. Both ways the Flight deck crew announced themselves as comprising three members. Normally, of course, there would only be two. Any particular reason? I thought it may be due to being a new-ish route for Easyjet but, moreover combined with the 'interesting' approach to LOWI thus, perhaps they were familiarising pilots to same. Any insider/official explanations?

You are correct. It is a Category C - ie 'more difficult' airfield - and special simulator training is required. A visit is useful as well and may be a requirement in EasyJet.

Flaps ???
 

Hello,
Had some ITVV DVD's for Christmas and a question has just popped into my head (Some 8 weeks later)

When the pilots are checking the control surfaces during taxi, why don't they check the flaps and spoilers ??

ie. Why not FULL flaps and then return them to TO configuration.

Cheers :ok:
Matt

Windy Landing
 

I was on a JET2 flight landing at LBA on Sunday (2 March) and the landing was quite bumpy due to wind conditions. Upon touch down we appeared to bank heavily to the right (felt like on one wheel!) and then levelled off. Everyone on board breathed a sigh of relief!

My question is how difficult is it to land in strong winds and are we in any danger from tipping over! As a passenger I feel quite nervous can anyone put my mind at rest?

Many thanks..

hi PPC,

been a flying instructor many years. we teach for these sort of things but sometimes a stronger than average crosswind gust may just strike when an aircraft is at its most vulnerable...that is just as it flares to land with consequential results but not always fatal nor damaging to aircraft nor passengers.

there have been in both light aircraft and large passenger jets crosswind induced accidents....but your chances of being involved in a car accident are still higher....

so relax...and enjoy your flights..when you a$$ is strapped to metal its going to do what its going to do in any event..!!:}

safe flying..

the dean.

It could have been that the pilot way just 'de-crabbing' the aircraft to align with the runway (using the rudder) and then putting in aileron control to put the into wind wing 'down' to maintain the centreline without drift. This is a recognised technique for the 737 and the 757 (which Jet2 have) and it means that you touchdown on one maingear before the other with the wing down. Nothing to worry about!

PP

p.s. should have been landing on Friday night, now that WAS windy!:ok:

It's very simple.
If the cabin is not secure then we DO NOT land. There is no way around it!!

Stall Warnings
 

We all (presumably) know about stick shakers and audible stall warnings that tell when a stall has or is about to occur but what I am confused about is how a stall or potential stall is actually detected.

Is the actual physical stall somehow detected by sensors reading air pressures etc, or does some particularly complicated bit of computer wizardry determine that the aircraft should be stalling "about now" given it's airspeed, configuration and external climatic conditions?

It is the air sensor on to top of the wing and senses the turbulent air foorewarning a stall

There's no sensor on top of the wing of which I'm aware, but methods of actually detecting a stall are nearly as varied as there are airplanes...and rightfully so, because airflow around each type of airplane is different.

A stall is an increase in angle of attack to the point of airflow separation, and a big buildup of induced drag and a loss of lift. These things don't happen all at once, necessarily. The key to understanding them is monitoring the angle of attack, and stall warning systems using stick shakers, pushers, etc, do this by sampling the angle of attack. They also sample the position of flight controls such as flaps...because the angle of attack at which the wing stalls will change with the flaps setting as the wing shape and configuration changes. It also takes into account air data information received from an air data computer. How the airplane does this depends on the airplane and the systems in use. Some are very simple, some are not.

Some airplanes like the airbus simply won't let the airplane stall due to "laws" built into the system. Some airplanes such as a single engine Cessna may use a small tab or even a simple suction port on the leading edge of the wing to produce a noise, and nothing more...and yet other airplanes don't even do that...they're simply detectable by a buffeting in the airframe or controls.

An angle of attack vane may be a movable vane which acts like a weathervane of sorts, or it may simply be a probe with holes that sample the way air flows around it to derive angle information. This is then applied to the aircraft data to determine what the actual angle of attack is (local angle of attack isn't the same as the free airstream, and AoA changes with maneuvering or configuration changes may mean that the AoA isn't the same as what the probe or vane is seeing at any given time...computers correct this). The system in use then takes this information in, and outputs whatever signal is necessary...such as a stick shaker or pusher signal.

What's checked really depends on the airplane. The airplane will fly with or without flaps...but not with or without ailerons, rudder, and elevator.

We check all the flight controls after we've set the flaps to their takeoff setting. In cycling the flaps we also move a number of other parts, including the leading edge devices which cycle in stages. We can only test certain things with flaps up, some with flaps out...and we have specific set procedures for everything. In some airplanes, spoilers or aileron augmentation is tested at the same time...happens on our airplane. On others we test them and then test emergency stow systems...some thrust reversers are tested and stowed, and on others, they're not.

The primary reason for testing the flight controls is to make sure they're powered, and that they're not locked for any reason. For example, in our airplane, when the flaps are up, the outboard ailerons are locked out. We have to extend the flaps to get the ailerons to work. We're checking for freedom of flight control movement and that our indicators in the cockpit correspond. There's no reason to run the flaps down, especially during ground operations when there's a greater possibility of damage, hitting something, etc. More importantly, we certainly don't want any possibility that they're overextended and a takeoff roll started with them in that dangerous condition. Further, there's no guarantee that simply because they extended before flight, that they'll work when it comes time to land.

Especially in a big airplane, moving flaps is a big deal, especially on the ground. Even powering a system, such as electrical or hydraulics, can have severe consequences...or moving a flight control for that matter. What's moved, when, where, and how fast must be carefully considered at all times...especially on the ground. We have flight control surfaces longer than a bus. Our horizontal stabilizer and elevators are bigger than the wings on a DC-3, with a wider span. There's a lot of metal moving out there. The flaps extend down a considerable distance, and there's just no good reason to put them down and then up again.

Fan blades generally sit loose in the hub, and tend to rattle when they're not under a load. This is done for several reasons, including issues regarding thermal expansion. hearing a rattle or clicking sound isn't at all unusual, when the engine winds down or is windmilling on the ground. You may hear other sounds, depending on the type of engine, associated with other parts of the engine, or even accessories.