C172 Taxiing speed

[David Luff]

Hi all,

I'm working on getting the small plane to taxi back in after flying a
circuit, so I'd appreciate some input from the pilots from the list on
real-life taxiing. What sort of speeds are typical during taxiing on the
runway, on a large taxiway, on a small taxiway between rows of parked
planes, and when turning corners. What's a typical turn radius at a
90degree junction. Are major taxiways such as the one parallel to the rwy
that normally seems to be called Alpha 2-way or is the traffic normally
directed one-way on them by ATC depending on the rwy in use? Do most light
plane parking spots have a designated direction when parked or is either
way fine?

Thanks in advance for any input,

Cheers - Dave

[David Megginson]

Post by David Luff
I'm working on getting the small plane to taxi back in after flying a
circuit, so I'd appreciate some input from the pilots from the list on
real-life taxiing. What sort of speeds are typical during taxiing on the
runway, on a large taxiway, on a small taxiway between rows of parked
planes, and when turning corners.

The rule I learned is never taxi faster than you can jog comfortably
(10 km/h or about 5kt for me), and usually more slowly, especially at
night or in bad weather or gusty winds. The ASI isn't all that useful
at low speeds on the ground, so we usually gauge it by power setting:
I was told to taxi a 172 at about 1000 RPM, but I end up riding the
brakes that way -- I find that 800-900 RPM is more suitable (and even
then, I brake more than I'd like to).

Post by David Luff
What's a typical turn radius at a 90degree junction.

That's easy -- follow the yellow line.

Seriously, rwy 4/22 at CYOW is 75 ft wide, and we usually backtrack on
04 from taxiway papa to get the full length for takeoff. When I go
back right along the edge (say, 5 or 6 feet in), and turn very tightly
with a lot of differential braking, I can just bring it onto the
centreline without an s-curve and without stopping my forward roll.
That's a minimum turning diameter of about 30 feet (15 foot radius)
while actually rolling forward -- a 25 foot radius would likely be
much more comfortable. You can turn much more tightly if you stop
your forward motion and just pivot around one wheel, but that's not
good for the plane.

Post by David Luff
Are major taxiways such as the one parallel to the rwy that
normally seems to be called Alpha 2-way or is the traffic normally
directed one-way on them by ATC depending on the rwy in use?

That would be very airport specific, but note that almost every case
ends up being a special case. People are always requesting a
different runway, a different taxiway, a different intersection
takeoff, etc., and ATC is usually pretty obliging. When I taxi on
taxiway alpha at CYOW, there is sometimes a big 767 or Airbus heading
straight towards me -- I have an instruction to hold short at delta
and the big plane will turn onto the main apron before there, so
there's not conflict, but it would look quite frightening to a new
passenger.

So the short answer is to let your AI plane take the shortest route
back to parking. Note that it should stop for a while before crossing
any runways -- even when you're precleared to cross, you still stop
and look.

The C172 should also stop to do a runup just before it goes to the
hold-short line runway -- that can take 3-5 minutes for a single and
longer for a twin. Allow another minute or so for tower clearance
before taxiing out for takeoff.

Post by David Luff
Do most light plane parking spots have a designated direction when
parked or is either way fine?

Light planes are almost always parked facing into the prevailing wind,
especially if they're out on the field. On the apron in front of our
hanger, they're facing any which way. The easiest choice would be to
have the AI plane just stop in front of the pumps.


All the best,


David

[David Luff]

On 11/7/02 at 4:33 PM David Megginson wrote:

<lots>

Thanks.

Post by David Megginson

Post by David Luff
Are major taxiways such as the one parallel to the rwy that
normally seems to be called Alpha 2-way or is the traffic normally
directed one-way on them by ATC depending on the rwy in use?

That would be very airport specific, but note that almost every case
ends up being a special case. People are always requesting a
different runway, a different taxiway, a different intersection
takeoff, etc., and ATC is usually pretty obliging. When I taxi on
taxiway alpha at CYOW, there is sometimes a big 767 or Airbus heading
straight towards me -- I have an instruction to hold short at delta
and the big plane will turn onto the main apron before there, so
there's not conflict, but it would look quite frightening to a new
passenger.

So basically they're 2-way, but sequentially, with planes never passing
wing-tip to wing-tip in opposite directions each side of the yellow line?

Cheers - Dave

[David Megginson]

Post by David Luff
So basically they're 2-way, but sequentially, with planes never
passing wing-tip to wing-tip in opposite directions each side of
the yellow line?

The yellow line is where your nosewheel is supposed to be. That said,
little planes pass each other all the time on taxiways -- it's just
like a country road, where one plane pulls far over to the side (even
onto the gravel) to let the other by. During daylight with good
visibility, ground control basically clears us to taxi to a runway and
leaves us alone to work out the details. Big planes, of course, have
to be more organized and wouldn't have room to pass on the same
taxiway (there are also issues with jet blast -- taxiing too close
behind an idling 737 could flip your Cessna upside down).

Even runways are two-way in the real world -- in light winds, one
plane might land on 32 as soon as the previous one turns off from a
landing on 14 and just before another takes off on 25 right through
the intersection with 14/32. In good VMC during the day, everyone
(especially the big transports) takes straight-in if they can get it.
In fact, the other night my instructor and I took a (long) runway with
a 5kt tailwind to save ten minutes getting home.


All the best,


David