Taxi speed

Hi,

In article ,
wrote:
747 and 777, 15 knots. At least that's what we, as mechanics were taught.
Slowing to 8ish in turns.

Just out of interest, how do you measure speed on the ground? Obviously the
airspeed indicator isn't much use in these situations...

(This is from a sim 'pilot', so might seem like a daft question!)

Andy

Andy Hawkins wrote:

Just out of interest, how do you measure speed on the ground? Obviously the
airspeed indicator isn't much use in these situations...

GPS and inertial nav units can provide ground speeds.

Andy Hawkins writes:

Just out of interest, how do you measure speed on the ground? Obviously the
airspeed indicator isn't much use in these situations...

If you have fancy avionics, they'll tell you your actual ground speed, as read
from an IRU or GPS.

--
Transpose mxsmanic and gmail to reach me by e-mail.

Mxsmanic wrote in
:

Andy Hawkins writes:

Just out of interest, how do you measure speed on the ground?
Obviously the airspeed indicator isn't much use in these
situations...

If you have fancy avionics, they'll tell you your actual ground speed,
as read from an IRU or GPS.

Says mr know nothing..


Bertie

Bertie the Bunyip wrote:
Mxsmanic wrote in
:

Andy Hawkins writes:

Just out of interest, how do you measure speed on the ground?
Obviously the airspeed indicator isn't much use in these
situations...
If you have fancy avionics, they'll tell you your actual ground speed,
as read from an IRU or GPS.

Says mr know nothing..


Bertie


But he is right

Flydive wrote in :

Bertie the Bunyip wrote:
Mxsmanic wrote in
:

Andy Hawkins writes:

Just out of interest, how do you measure speed on the ground?
Obviously the airspeed indicator isn't much use in these
situations...
If you have fancy avionics, they'll tell you your actual ground
speed,
as read from an IRU or GPS.

Says mr know nothing..


Bertie


But he is right


Not really. We use them as a rough guide but they're not all that
reliable on the ground. Only as a guide. Older widebodies had ground
speedos just like a car. Just a little clock on the capt's panel down
the bottom, usually. All newer ones use IRS, but
IRS info can be out by up to 10 knots by the time you land. A
negligable error in flight, but huge on the ground. Also ****s up your
wind indications on appraoch. Not a problem for a pilot, BTW, but it
does screw up the automatics if they get confused about the crosswind on
some airplanes.
It's not uncommon for them to show movement while you're parked after a
long flight particualrly if radio update isn't all the best towards the
end. Like if you're flying into an area without a lot of DMEs. newer GPS
stuff is better, but it's not really neccesary anyway except in 74's
wher it's quite difficult to tell your GS.



Bertie

Bertie the Bunyip wrote:
Flydive wrote in :

Bertie the Bunyip wrote:
Mxsmanic wrote in
:

Andy Hawkins writes:

Just out of interest, how do you measure speed on the ground?
Obviously the airspeed indicator isn't much use in these
situations...
If you have fancy avionics, they'll tell you your actual ground
speed,
as read from an IRU or GPS.
Says mr know nothing..


Bertie

But he is right


Not really. We use them as a rough guide but they're not all that
reliable on the ground. Only as a guide. Older widebodies had ground
speedos just like a car. Just a little clock on the capt's panel down
the bottom, usually. All newer ones use IRS, but
IRS info can be out by up to 10 knots by the time you land. A
negligable error in flight, but huge on the ground. Also ****s up your
wind indications on appraoch. Not a problem for a pilot, BTW, but it
does screw up the automatics if they get confused about the crosswind on
some airplanes.
It's not uncommon for them to show movement while you're parked after a
long flight particualrly if radio update isn't all the best towards the
end. Like if you're flying into an area without a lot of DMEs. newer GPS
stuff is better, but it's not really neccesary anyway except in 74's
wher it's quite difficult to tell your GS.



Bertie

True in part, the latest FMS use the GPS as primary source, so the GS
indication is quite accurate on the ground.

Flydive wrote in :

Bertie the Bunyip wrote:
Flydive wrote in :

Bertie the Bunyip wrote:
Mxsmanic wrote in
:

Andy Hawkins writes:

Just out of interest, how do you measure speed on the ground?
Obviously the airspeed indicator isn't much use in these
situations...
If you have fancy avionics, they'll tell you your actual ground
speed,
as read from an IRU or GPS.
Says mr know nothing..


Bertie

But he is right


Not really. We use them as a rough guide but they're not all that
reliable on the ground. Only as a guide. Older widebodies had ground
speedos just like a car. Just a little clock on the capt's panel down
the bottom, usually. All newer ones use IRS, but
IRS info can be out by up to 10 knots by the time you land. A
negligable error in flight, but huge on the ground. Also ****s up
your wind indications on appraoch. Not a problem for a pilot, BTW,
but it does screw up the automatics if they get confused about the
crosswind on some airplanes.
It's not uncommon for them to show movement while you're parked
after a
long flight particualrly if radio update isn't all the best towards
the end. Like if you're flying into an area without a lot of DMEs.
newer GPS stuff is better, but it's not really neccesary anyway
except in 74's wher it's quite difficult to tell your GS.



Bertie

True in part, the latest FMS use the GPS as primary source, so the GS
indication is quite accurate on the ground.


If you need it. He was stil worng.




bertie

Hmm, interesting posts.

According to what I've read from the Manuals/Specs most are recommended to
taxi at about 20 and turns are at 12 or slower. I haven't seen that many
manuals or specs, maybe round 3 or 4 but they pretty much had the same taxi
speed requirements. Any faster than that, and I've seen mentioned of tire
and brake wear.

When I was sitting behind the Pilot in a Beaver, he kept it to a slow crawl
at all times. Probably because the taxi way was kinda bumpy and didn't want
us tossed around. Comfort of the paying customers is paramount. How would
you feel sitting in an Airbus and getting your cookies tossed around because
the Pilot was trying to make up some speed on the ground and couldn't care
about your comfort? I don't think so. Remember, the Pilot is responsible
for everyone's safety and their comfort.

http://img.photobucket.com/albums/v4...a/IMG_0290.jpg

Mark G
Not4wood


"Andy Hawkins" wrote in message
...
Hi,

In article ,
wrote:
747 and 777, 15 knots. At least that's what we, as mechanics were taught.
Slowing to 8ish in turns.

Just out of interest, how do you measure speed on the ground? Obviously
the
airspeed indicator isn't much use in these situations...

(This is from a sim 'pilot', so might seem like a daft question!)

Andy

Not4wood wrote:

When I was sitting behind the Pilot in a Beaver, he kept it to a slow crawl
at all times. Probably because the taxi way was kinda bumpy and didn't want
us tossed around. Comfort of the paying customers is paramount. How would
you feel sitting in an Airbus and getting your cookies tossed around because
the Pilot was trying to make up some speed on the ground and couldn't care
about your comfort? I don't think so. Remember, the Pilot is responsible
for everyone's safety and their comfort.

Something that's going to bounce you to the ceiling in a only going to
be a hiccup in an Airbus.