Taxiing a Boeing 747

[CaptainKing]

Here's a question to the 747 pilots out there.

At about what IAS do you guys taxi the 747 at? Been wanting to know for a while, please could you inform me, seeing as I want to be taxiing and flying a 747 one day.

Cheers

[Storminnorm]

Used to taxy a 767 at about 20-25 kts as I remember.
Depending on traffic of course.
And traffic lights.

[A Comfy Chair]

Taxi based on Groundspeed, not IAS.

Turns no more than 10 to 15 kts, on a long straight upto about 30kts.

Most of the time between 15 to 25.

[One Outsider]

At about what IAS do you guys taxi the 747 at?
Oh, Brother!

[max1]

IAS? WTF. Done any sailing?
I'd hate to see the G/S after landing into a 35kt headwind and taxying back the other way.

[Um... lifting...]

Headwind? For my part, I'm wondering how you tack or jibe that thing when it's a crosswind, all the passengers hiked out the windows on the high side.
When I had the pleasure of seeing one taxi downwind, you should have seen the size of the spinnaker on the thing... it was something to behold. Thing of beauty, really.

[Capot]

Come along now, do keep up.

Every proper pilot knows that a 747 is on a broad reach when moving forwards with a cross-wind, and doesn't need to tack or gybe.

In a headwind, though, it's a different matter, and net forward movement can only be achieved by a series of tacks across the runway or taxiway, with necessarily very short boards.

To save wear and tear on tyres every company I have been in would practice this in the simulator to develop the pilots' skills well beyond their normal rather low-level basic skills; this policy pays off handsomely as the taxi times shorten dramatically.


Edit (Well, it was in Jetblast when I started.....)

[Storminnorm]

Watch out for the boom in a jybing situation though!
Give you a nasty crack can that.

[CaptainKing]

What is jybing? Could someone fill me in. Has it got something to do with taxiing into the wind, or crosswind?

Thanks

[dany4kin]

The real question is whether the IAS would be any different if the aircraft were taxiing on a conveyor belt.

[Solid Rust Twotter]

Ah, fresh meat.....












Think we got a live one here folks......:E

[A Comfy Chair]

CaptainKing,

The usual suspects :} are out to have a bit of fun with the newbie. Like asking for a tin of checkered paint, or the left handed screwdriver.

IAS is Indicated Airspeed, and is your speed relative to the body of air. G/S is Groundspeed, and is your speed relative to the ground.

You taxi based on G/S.

As to the rest of it, you might have to learn to sail to understand what they're on about :}

[TurningFinals]

Like a lamb to the slaughter....

[Old Smokey]

I was with a trainee once who sought guidance for a "good" taxi speed on a straight taxiway. I told him "Just keep pace with that A310 in front, that's about right".

When our IAS came alive I had to say "OK, OK, that guy's on a hot date somewhere, slow down to 30 knots Ground Speed".:eek:

Regards,

Old Smokey

[Capot]

Captain King,

What is jybing? Could someone fill me in.Since no-one has, I will, with apologies for using technical terms and assuming that people know them.

Jibing is what people do to other people who can't spell gybing.

Jybing is what people do when they surf the Web together regardless of their geographic location.

I hope that clears it up helpfully.

PS Edit: Wikipedia, so often wrong, says Gybe, an alternative spelling of jibe (http://en.wikipedia.org/wiki/Jibe), a sailing maneuver In my book, there's only one way to spell gybe when talking about the manoeuvre. Wiki can't spell manoeuvre either.

The rot started with the Boston Tea Party.

[SNS3Guppy]

Captainking,

Our policy is 20 knots maximum taxi speed, and 10 knots maximum when in a turn. The maximum speed with body gear steering engaged is 20 knots. We read this speed from our FMS/INS displays.

[BelArgUSA]

The 747-200/300 FCTM does not publish speed limits for taxi.
Most operators I worked for had 20 knots limit, and 10 knots for turns.
Being "high" on the flight deck makes you think that you are slow. Wrong...
xxx
You want to taxi at 30 and 40 on long distances...?
Look at your brake temperatures 10 minutes after takeoff.
You might have a nasty surprise.
xxx
For tight turns (i.e. transitions JFK from inner/outer taxiway) you need to slow.
That leaves you with almost no "moving energy"...!
I always used outboard differential power in turns to assist.
And differential braking as well.
The nosewheel cannot "always" be trusted to steer you nicely.
I always instructed pilots to compare nosewheel effectiveness to a piece of wet kleenex.
Especially during takeoff. Loss of engine...? Nosewheel will not do much.
xxx
:}
Happy contrails

[galaxy flyer]

BelArgUSA

Quite right on NWS, even the 4 nosewheel tires could not overcome the aft gear when they were stuck castered outboard. A good demo on why Vmcg gives no credit for NWS

GF

[BelArgUSA]

Hola GF...
xxx
I suspected the 4 NW tires of the C-5 do not offer more than 2 on 747s...
As far as I am concerned, NWS is to line-up on the runway. Period.
Thereafter - forget the NWS.
xxx
Some "experts" make me smile...
After line-up, they push "forward" on the control wheel... airplane standing...!
As if there is a mechanical linkage, pushing the tail up, increasing NW effectiveness.
Then there are those (same) "experts" pushing forward during takeoff roll.
Elevators MAX down. They forget they are actually increasing... aerodynamic drag...!
Why not keeping the elevators neutral/faired to reduce drag...?
xxx
Interesting to note that with PanAm, the 747 steering (rudder pedals) was disconnected.
Once properly aligned (say, by 5 or 10 knots), I never touched the "tiller wheel" again.
In case of an early engine failure (and steering/VmcG problem) the tiller was never used.
Reject procedure was simple. ALL ENG IDLE, REV ON EQUAL PAIR, IDLE REV on ODD ENG.
Speed brakes deployed, because of reverse pair deployment...
But the "experts" love to make simple matters complicated.
xxx
I recall a 747 swinging 90º to the right, from a standing start on the runway.
I was holding short behind them. Looks like their nº 4 engine did not spool-up...
What I admired was seeing their nosewheel steered left, then right, then again.
Without ANY EFFECT. These guys probably "pushed their control wheels FWD" as well.
xxx
Shall we laugh at them, or cry...?
Or shall we recommend "radial" tires for nosewheels, Michelin ZX maybe...?
Let us now wait for the next "expert" recommending white walls...
xxx
:E
Happy contrails
xxx

[rodthesod]

A TAXI is what takes you to and from the airport.
TAXY is what you do when you drive an aeroplane on the ground.

[SNS3Guppy]

Actually, taxi is correct for motive operation of the aircraft on the surface.

[rodthesod]

I suspect it is in the USA - doesn't make it correct in English English.

[Gibon2]

From the Oxford English Dictionary:


taxi, v.

1. a. intr. Of an aeroplane, etc., or its pilot: to travel slowly along the ground or water under the machine's own power. Also transf. to taxi in, to taxi from a runway to a terminal or hangar; similarly to taxi out.

b. trans. To cause (an aeroplane, etc.) to taxi.


"Taxy" is mentioned as a spelling variant of taxi, but only for the present participle (i.e. "taxying"). There is no separate entry in the OED for "taxy".

Glad I could help.

[BelArgUSA]

Gibon - come on, friend -
Didn't you know that Oxford is located somewhere around Mut or Adana...?
That is, in Turkey...
That is the issue for their EU membership - teach others to spell English...
Taxy... ROFL
xxx
:E
Happy control

[BelArgUSA]

Hola shroom -
xxx
You agree generally with what I say... actually, I just repeat long established procedures.
Nothing is "from me personally" -
Such as items mentioned here were recommended for years at PanAm trainng.
The source were Boeing and various other airline training departments.
As you say, Airbus might recommend differently.
At times I admire Airbus modern design, but trust Boeing for expertise in older concepts.
I do not believe that forward pressure would improve VmcG (or NWS) on an Airbus 320...
Anymore than it does improve anything about VmcG on any Boeing.
As "more flaps" deflection increase drag (and slow acceleration), elevators do same.
xxx
Would you fly with any old fart from PanAm, as with me, you probably would object too.
That is the way we were trained by the then "big chiefs".
And after they were gone, I have to say, their techniques still worked.
When I did training with other airlines, later, I continued their procedures
As line pilot, I was just plain average, but as instructor, I had top reputation.
If the technique is recommended differently by Airbus, do it "their way".
What is mine is comparing NWS to be as effective as a piece of wet kleenex.
And when no ladies in the classroom, I worsen by saying "as slippery as a wet fart".
xxx
:ok:
Happy contrails

[SNS3Guppy]

I suspect it is in the USA - doesn't make it correct in English English.


USA...birthplace of powered controlled flight and aviation. UK...not.

It's taxi. When the Queen learns to taxi she can call it whatever she likes.

[shroom]

Though I will say that when practicing (in the sim) a #1 or #4 engine failure, with a wet runway, at light weight, early in the takeoff roll in a 747...well, needless to say, nosewheel steering won't do a damn thing to keep you on the runway and off the grass. That's for sure!